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COMPARING TWO METHODS OF NON-COMPLIANCE CLASS II THERAPY: THE DISTAL JET AND THE SMD (FROG) Larrissa K. Cali, D.M.D. An Abstract Presented to the Graduate Faculty of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2011 0 Abstract Purpose: The objective of this study was to compare the dental effects of the Distal Jet and the Frog, two types of molar distalizers. The position of the upper second molars was also evaluated to determine if second molar eruption affected the dental changes caused by the distalization appliances or the rate of distalization. Materials and Methods: The investigation was a retrospective, clinical study of 79 Distal Jet patients with a mean initial age of 13.6 years and 29 Frog patients with a mean age of 11.5 years. The Frog and Distal Jet samples were matched according to initial age and gender. Pretreatment (T1) and postdistalization (T2) lateral cephalograms were traced and analyzed with the pitchfork analysis. The long axes of the upper first molar and upper incisor were measured relative to the functional occlusal plane to evaluate angular changes in these teeth. Variations in design of the Distal Jet appliance were assessed by comparing the original tube and piston design to the Bowman modification. The dental effects and rate of the distalization appliances were compared when second molars were erupted or unerupted. Independent t-tests were used to assess differences between groups. 1 Results: The original tube and piston design of the Distal Jet exhibited a significantly significant greater amount of horizontal molar movement over a shorter period of time. Patients treated with the Frog and both appliance designs of the Distal Jet exhibited a general trend for mesial movement of the maxilla, mandible, and dentition. The Distal Jet produced significantly more molar distalization than the Frog in a shorter period of time. Greater mesial movement of the lower incisors and lower molars was seen in the Distal Jet group when compared to the patients treated with the Frog. More incisor anchorage loss was observed when distalizer therapy was initiated after second molars erupted. Conclusions: The original design of the Distal Jet appliance produces greater distal maxillary molar movement in a shorter period of time when compared to the Bowman modification. The Distal Jet and the Frog are effective at correcting Class II malocclusions although the Distal Jet is a more efficient means of molar distalization. Molar distalization after second molar eruption causes more incisor anchorage loss than that produced when second molars are unerupted. 2 COMPARING TWO METHODS OF NON-COMPLIANCE CLASS II THERAPY: THE DISTAL JET AND THE SMD (FROG) Larrissa K. Cali, D.M.D. A Thesis Presented to the Graduate Faculty of Saint Louis University in Partial Fulfillment of the Requirements for the Degree of Master of Science in Dentistry 2011 3 COMMITTEE IN CHARGE OF CANDIDACY: Professor Rolf G. Behrents, Chairperson and Advisor Professor Eustaquio Araujo Associate Clinical Professor Donald R. Oliver i ACKNOWLEDGEMENTS I would like to thank Dr. Behrents for allowing me to be a part of the orthodontic program at Saint Louis University. I feel very blessed to have received my orthodontic education at an institution that provides an extraordinary clinical and didactic environment and the opportunity to learn from so many incredible instructors. Thank you to Dr. Behrents for sharing your vast expertise in diagnosis and treatment planning and for guiding and advising me on my thesis. I would like to recognize Dr. Araujo for his assistance on my thesis. He is an extraordinary clinician, mentor, and individual and his guidance has left an indelible impression. I will be forever grateful for the ways that he has shaped my life and future career. Thank you to Dr. Oliver for his immeasurable support and encouragement during the research process. and attention to detail are incredible. His memory I am thankful that I have had the opportunity to gain experience from such a remarkable instructor and orthodontist. A special thank you goes to Dr. Jay Bowman and Dr. Kevin Walde for providing the records that were used in this study. They are exceedingly busy in their practices ii yet never hesitated to take the time to provide guidance and assistance to me. Thank you to Heidi Israel for her help with the statistical analysis. She has worked tirelessly even with an extremely demanding schedule and I am grateful for the time she made available to help me. iii TABLE OF CONTENTS LIST OF TABLES............................................v LIST OF FIGURES..........................................vi CHAPTER 1: INTRODUCTION..................................1 CHAPTER 2: REVIEW OF THE LITERATURE......................4 The Class II Problem Defined.........................4 Prevalence of Class II Malocclusions.................4 Class II Etiology....................................5 Class II Correction..................................6 The Role of Compliance in Treatment..................8 Appliances Requiring Minimal Compliance.............10 Fixed Functional and Bite Jumping Appliances........11 Herbst.........................................11 MARA...........................................14 Mandibular Protraction Appliance (MPA).........16 Forsus.........................................17 Jasper Jumper..................................19 Intraoral Molar Distalization Appliances............21 Magnets........................................22 NiTi Coil Springs..............................23 Pendulum.......................................24 Jones Jig......................................26 Distal Jet.....................................27 Simplified Molar Distalizer (SMD)..............38 Distalizing and Second Molars.......................40 Summary and Statement of Thesis.....................41 References..........................................42 CHAPTER 3: JOURNAL ARTICLE Abstract............................................47 Introduction........................................49 Materials and Methods...............................51 Sample.........................................51 Data Collection................................53 Statistical Methods............................55 Results.............................................56 Discussion..........................................60 Conclusions.........................................67 References..........................................69 Appendix.................................................71 Vita Auctoris............................................73 iv LIST OF TABLES Table 3.1: Sample characteristics of age-matched Distal Jet and Frog samples...............58 Table 3.2: Comparison of age-matched Distal Jet and Frog samples..........................58 Table 3.3: Comparison of patients on the basis of second molar position..................60 Table 3.4: Comparison of Distal Jet appliance effects reported in the literature........65 Table A.1: Description of cephalomeric variables used in the pitchfork analysis............71 Table A.2: Sample characteristics of Distal Jet group according to appliance design.......72 Table A.3: Comparison of original tube and piston Distal Jet and Bowman modified Distal Jet................................72 v LIST OF FIGURES Figure 2.1: Diagram of the original bilateral tube and piston design of the Distal Jet..................................28 Figure 2.2: Diagram of the Frog appliance........39 Figure 3.1: Diagram of the variables included in the pitchfork analysis............54 vi CHAPTER 1: INTRODUCTION Many techniques and appliances are used to correct Class II malocclusions. All of the methods can be successful at producing Class I occlusions in patients with dental and/or skeletal problems. Attempts have been made to develop new techniques to make treatment better and more efficient, decrease chair time, and reduce the need for patient cooperation. Class II malocclusion presents a frequent challenge to orthodontists. Many of the techniques aimed at correcting Class II malocclusions such as headgear, removable appliances, and interarch elastics, rely heavily on patient compliance. Acquiring cooperation from patients can be difficult and when cooperation is lacking, longer treatment times and inferior outcomes can result. To limit the reliance on patient compliance, clinicians have turned to appliances such as molar distalizers to treat Class II patients. Distalizing appliances can be an effective means to translate upper molars that are positioned forward into a Class I relationship without the reliance on patient cooperation. Establishing the effects of various appliances and determining which are most effective is 1 important for clinicians so that they can make educated treatment decisions. Maxillary molar distalizers are not without drawbacks. They can be costly and uncomfortable. The appliances can break or fail requiring repair and increasing chair time. Undesirable effects on the dentition can result. The Distal Jet has been previously compared to several different molar distalizing appliances. It has proven to be an effective and reliable method of molar distalization. The Distal Jet has been touted as an appliance that produces bodily movement of the maxillary molars. The ability to produce bodily molar movement has also been attributed to the Frog, another appliance for molar distalization but, to date, there is no published data examining the effects of the Frog. The purpose of this study is to compare and contrast the dental effects of the Distal Jet and the Frog. The amount and rate of molar distal movement and tipping along with the amount of anchorage loss will be considered. The goal of this investigation is to establish whether the Frog appliance can be used effectively to correct Class II dentitions and how it compares to the Distal Jet, an established method of Class II treatment. Additionally, two types of Distal Jet appliances will be compared to 2 determine if there is a difference in the dental effects they produce. The effect of erupted second molars on the efficiency and results of distalizer therapy have been examined and the conclusions about their contribution in distalization treatment are contentious. In this study, the position of second molars will be compared with the dental effects that are produced to determine if these teeth play a significant role in the amount of distalization or anchorage loss that is observed. 3 CHAPTER 2: REVIEW OF THE LITERATURE The Class II Problem Defined The goals of orthodontic treatment are aesthetics, function, and stability. Occlusal function is determined by the relationship of the upper and lower teeth to each other. Angle, the father of modern orthodontics, is credited with developing the first meaningful classification of occlusal relationships in the 1890s.1 Angle suggested that the upper first molars were the key to occlusion and that a Class II malocclusion exists when the lower molars are positioned distally relative to the upper molars.1 In Class I, or normal, occlusion, the mesiobuccal cusp of the upper first molar occludes in the buccal groove of the lower molar. Orthodontists attempt to finish orthodontic treatment with Class I occlusion whenever possible. Prevalence of Class II Malocclusions Class II malocclusion is a common finding within the general population and among orthodontic patients. It is characterized by the upper molars positioned forward of the lower molars and a preponderance of upper incisors are forward of the lower incisors in what is termed overjet. 4 The third National Health and Nutrition Examination Survey (NHANES III) was conducted from 1988 to 1991 and studied 7,000 individuals to provide estimates of malocclusion in U.S. children and adults. Rather than looking at molar relationships, measurements of overjet were used as an estimate of the prevalence of Class II malocclusion.2 According to data from NHANES III, Class II malocclusion, defined as 5 mm or more of overjet, occurs in 23% of children (ages 8-11), 16% of adolescents (ages 1217) and 13% of adults (ages 18-50). Mildly increased overjet, 3-4 mm, is as prevalent as what is considered an ideal overjet of 1-2 mm. Severe Class II malocclusion occurs in 4% of the population and is more frequent in African-Americans and Mexican-Americans than in Caucasians.2 This data indicates that the skeletal Class II jaw relationship is the most common skeletal disharmony occurring in the United States. Class II Etiology The nature of Class II malocclusions has been examined extensively. In 1981, McNamara evaluated the lateral cephalometric radiographs of 277 children eight to ten years of age with Class II malocclusions to determine the maxillary and mandibular skeletal and dentoalveolar positions and the vertical development of each patient.3 5 According to McNamara, those with Class II malocclusions most frequently exhibit retrusion of the mandible. The position of the maxilla is more variable but tends to be normally positioned. If it is in an abnormal position, the maxilla tends to exhibit skeletal retrusion more often than protrusion, which was found in only a small percentage of the subjects. In patients that exhibited excessive vertical development, maxillary retrusion was most commonly occurring. Excessive vertical development is found frequently in Class II individuals and McNamara suggests this may be due to abnormalities in respiratory function. The results of this study indicate that the maxillary dentition is less protrusive in Class II malocclusions than what was reported in previous studies. McNamara indicates that lower incisors are typically normally positioned. He concluded that the Class II problem is complex and there are 77 different combinations of morphological traits that can result in a Class II malocclusion.3 Class II Correction Proffit refers to a skeletal growth pattern that is cephalocaudal, i.e., more growth occurs in the lower extremities than in the upper.1 This same phenomenon takes place in the face where the mandible exhibits accelerated growth relative to that of the maxilla. 6 This trend is referred to as differential growth and can contribute to the correction of a Class II malocclusion. Proffit cautions, however, that it is unlikely to expect that growth will supply more than 3-4 mm to the correction of a Class II malocclusion. Numerous methods have been described for the correction of Class II malocclusions. Some techniques affect only the dental arches while others result in skeletal correction. Extraction of teeth in both dental arches or in the maxillary arch alone can also be employed to modify occlusal relationships and reduce overjet.1 This approach can be particularly helpful in patients exhibiting dental crowding or protrusive soft tissue profiles. Class II treatments can involve extraoral traction with headgear to modify the growth of the maxilla and allow differential forward growth of the mandible and to distalize or maintain the position of the maxillary dentition.1 Multiple techniques act intraorally to deliver distally-directed forces on the maxillary dentition and mesially-directed forces in the mandible.1 either fixed or removable. These can be Examples include functional appliances and intermaxillary (Class II) elastics. Orthognathic surgery to reposition one or both jaws is an effective method to treat Class II patients when soft tissue aesthetics is a concern and in those individuals 7 where a severe occlusal and/or skeletal discrepancy exists.1 Each of these approaches has been used successfully in Class II correction and all have inherent strengths and shortcomings. The Role of Compliance in Treatment Studies investigating the role of patient compliance in treatment are frequent in the orthodontic literature. Many of the appliances used in the treatment of Class II malocclusions such as headgears, removable functional appliances, and intermaxillary elastics rely heavily on patient cooperation for success. Bos et al. studied headgear compliance objectively with a timer device that recorded temperature.4 Their findings indicate that compliance with headgear is significantly overestimated by orthodontists, patients, and parents of patients. Often times, subjective information from patients is the only evidence of cooperation with appliances.5 False reports regarding compliance and an inability to accurately measure a patient’s level of cooperation make distinguishing compliant patients from noncompliant ones difficult or impossible.5 Prediction of patient compliance may be helpful to forecast treatment issues in order to alter the treatment plan and reduce the need for cooperation before problems 8 arise. Unfortunately, “identifying characteristics that predict cooperation with treatment is a difficult and complex problem.”6 Several characteristics of patients have been examined in an attempt to determine what drives a patient to comply. Several studies have shown that younger patients comply more readily than older ones4,7,8 and that girls are more compliant than boys.6 Other studies have shown no relationship between gender and level of compliance4 and some have found that boys are more compliant than girls.7 Overall, the complexity of human behavior makes it difficult to make useful predictions.5 It has been said that “patient cooperation is the single most important factor every orthodontist must contend with.”6 Motivating patients can be challenging and when patient compliance is lacking, longer treatment times6, 9 and compromised outcomes6 may result. The results of a study by Skidmore, et al., indicate that orthodontic treatment of patients with Class II molars takes longer than Class I treatment.9 Correction of Class II malocclusions is made more challenging by the use of appliances that require cooperation such as headgear, elastics and removable appliances.10 Conversely, patients whose treatment is completed in a timely manner may be more 9 pleased with their orthodontic treatment and more likely to refer other patients to their orthodontist.11 Because of the concerns regarding patient compliance, orthodontists have sought treatment modalities that reduce the need for patient compliance. There are several examples of appliances that require minimal cooperation yet can be used successfully to correct a Class II malocclusion. Appliances Requiring Minimal Compliance Appliances that do not rely on compliance to correct Class II malocclusions can be classified into those that reposition the mandible forward and utilize certain functional or bite jumping elements for correction and those that are focused only on maxillary molar distalization. The following is a partial listing of appliances that are considered to require minimal patient cooperation: Fixed Functional Appliances Herbst MARA MPA Forsus Molar Distalizers Jones Jig Pendulum Distal Jet Frog 10 Fixed Functional and Bite Jumping Appliances Fixed functional appliances are attractive to clinicians because they reduce the reliance on patient cooperation. Some common fixed functional appliances include the Herbst, MARA, MPA and Forsus. Herbst The Herbst was introduced by Herbst in 1909.12 appliance was re-introduced in 1979 by Pancherz. The It consists of bilateral telescope mechanisms which are each made up of a tube attached to the upper first molar band and a plunger attached to the lower first premolar band. Alternatively, cast splints can be used instead of bands. The length of the tube and plunger determines the amount of mandibular advancement. Pancherz recommends advancement of the mandible until the incisors are in an edge-to-edge relationship.13-15 Speech, mastication, and swallowing are all carried out with the mandible in an anteriorly protruded position. Pancherz contends that Herbst appliance therapy causes a redirection of maxillary growth, mesial tooth movements in the mandible, distal tooth movements in the maxilla, and possibly stimulates mandibular growth.14 Pancherz has conducted several studies comparing the skeletal and dental effects in Class II, division 1 11 patients treated with the Herbst compared with untreated control groups.13,14 Patients were treated for six months while the control group was followed for the same length of time.13 The occlusion was analyzed via dental casts and the skeletal effects were assessed using lateral cephalograms taken before and after the examination period with the teeth in centric occlusion and with the mouth wide open so as to inspect the mandibular condyle. All patients started treatment with a full-cusp Class II molar relationship. There were no significant differences between the treatment group and the control group in any of the cephalometric variables that were studied. After treatment, all of the cases exhibited successful correction to a Class I relationship. The overjet decreased 3.8 mm and the overbite decreased 2.5 mm. None of the patients showed a difference in centric occlusion and centric relation greater than 1.5 mm. The control group exhibited no changes in the same parameters. The ANB angle was significantly reduced in the Herbst group as compared to the control group and this was attributed to a decrease in the SNA angle and an increase in the SNB angle. Lower facial height was increased more in the treatment group. The position of the upper incisors was not changed in either of the groups but the lower incisors were 12 significantly proclined (5.4º) in the Herbst group and they were unchanged in the control group. Herbst treatment resulted in a reduction in facial profile convexity while the control group exhibited negligible profile changes. There was a significant increase in mandibular length in the Herbst group (3.2 mm) when compared with that of the untreated controls (1.0 mm). Pancherz asserts that the improvement in sagittal molar and incisor relationships seen after Herbst therapy is a consequence of equal contributions of orthopedic and dentoalveolar changes.14 Molar correction is primarily a result of an increase in mandibular length, distal movement of the maxillary molars and mesial movement of the mandibular molars.14 Overjet correction is a consequence of an increase in mandibular length along with proclination of the lower incisors. According to the research conducted by Pancherz, the temporomandibular joints were unchanged in all of the patients treated with Herbst appliances. The mandible exhibited greater skeletal effects than the maxilla primarily due to an increase in length in combination with an anterior displacement. Intrusion of lower incisors and eruption of the lower molars causes the occlusal plane to tip downward.15 After Herbst treatment, patients exhibit less increase in mandibular length that untreated 13 controls.15 The occlusal plane tips up anteriorly and the upper molars are moved mesially and extruded. Most of the posttreatment changes occur in the first six months after Herbst therapy. When compared with removable functional appliances, the Herbst has several advantages: it cannot be removed by the patient, requires no patient cooperation, and has a short active treatment time of approximately 6-8 months.15 The Herbst is indicated in patients with a Class II, division 1 or division 2 malocclusions. It is most effective in the permanent dentition approximately at the pubertal growth peak. Herbst therapy is not suggested for use in the deciduous or mixed dentition and should not be utilized for nongrowing patients as the effects of treatment would be limited to the dentition.15 MARA The Mandibular Anterior Repositioning Appliance (MARA) was introduced by Ormco in 1998 after being developed and tested by Toll and Eckhart.1 The appliance consists of stainless steel crowns on the upper and lower first molars attached to a TPA and lower lingual holding arch, respectively. Horizontal bars protrude from the upper and lower molar crowns on the buccal which creates occlusal interferences causing the mandible to protrude forward into 14 a Class I occlusion. Shims can be used to incrementally increase the activation. According to Pangrazio-Kulbersh et al., the MARA produces significant dental and skeletal effects.16 Their sample of 30 Class II patients treated with the MARA was compared to a matched sample of untreated controls from the Michigan Elementary and Secondary School Growth Study and to a previous study investigating the effects of the Herbst and Frankel II appliances. The results indicated that the MARA produces no orthopedic effect in the maxilla. On the other hand, the greatest difference between the treatment and control groups was in mandibular skeletal measurements indicating enhanced mandibular growth. The maxillary molars were moved distally and the lower molars and incisors were moved forward. were not observed. Vertical dental movements Significant increases in the anterior and posterior face heights were observed in the treatment group. The MARA produces effects similar to those of the Herbst and has a greater dental effect than the Frankel II. The Herbst has a greater effect on maxillary growth and exhibits greater intrusive effects on the dentition when compared to the MARA. The authors concluded that 47% of the Class II correction produced by the MARA is orthopedic while 53% can be accounted for by dental alterations.16 15 Advantages of the MARA in comparison to the Herbst include enhanced aesthetics, disengagement does not occur, and breakage is not as common.12 Additionally, the MARA can be used with full fixed appliances.12 Disadvantages include the requirement of molar crowns which increase the facial height and can cause mobility of the molars.12 Mandibular Protraction Appliance (MPA) The Mandibular Protraction Appliance (MPA) was introduced in 1995 by Coelho.12 fabricated by the orthodontist.12 It was designed to be The original appliance has been redesigned four times to facilitate construction and installation and to improve on the functionality.17,18 The most recent advancement, the MPA IV, consists of a tube that connects to the maxillary molar at the headgear tube and a piston that connects to the lower archwire at a helix distal to the canine bracket.19 A comparative study of the Herbst and MPA was conducted by Alves and Oliveira to evaluate the skeletal, dental, and soft tissue effects of the two appliances.19 The study included 43 adolescents divided into three groups: 12 subjects with a mean age of 12 years and 4 months treated with the Herbst for 8.7 months; 15 subjects with a mean age of 13 years and 2 months treated with the MPA for 8.3 months; and group 3 consisted of 16 subjects 16 with a mean age of 10 years 4 months who received no orthodontic treatment. Lateral cephalograms were taken of each patient in the treatment groups before treatment and after appliance removal. Patients in the control group had two radiographs within the 10 month interval they were followed. Results of the study indicated that both the Herbst and MPA result in greater increases in mandibular length, protrusion of the lower incisors, and retrusion of the upper lip when compared with the untreated controls. Patients treated with the MPA exhibited significantly more mandibular sagittal change than those in the Herbst group.19 Forsus Vogt is credited with development of the Forsus Fatigue Resistant Device (FRD).20 The Forsus consists of a push rod with a hook on the mesial end that is crimped onto the lower archwire distal to the canine or first premolar brackets.21 The distal end of the push rod inserts into a telescoping cylinder that is made up of an inner and outer sliding tube surrounded by an open-coil spring. The distal end of the cylinder is then attached to the maxillary first molar headgear tube with an L-pin or clip feature. When the spring is compressed it delivers about 200 g of force.21 Generally, the springs are not fully compressed making the force level more comparable to interarch 17 elastics. The force of the spring places a distal and intrusive force on the upper maxillary molars using the lower arch as anchorage. A study of the Forsus appliance evaluated the skeletal and dental effects of the device.20 A questionnaire was also used to assess patient satisfaction with the appliance. The sample was made up of 13 growing Class II patients with an average age of 14.2 years treated for four months with the Forsus. Lateral cephalograms were taken before treatment and upon removal of the appliance. Results indicated that the upper molars were moved distally and the lower molars were moved mesially, improving the Class II molar relationship by ¾ of a cusp width. Sixty- six percent of the correction was shown to be a result of dental effects. The upper anterior teeth were retroclined by 5.3º while the lower teeth were proclined 9.6º, reducing the overjet by 4.6 mm. The overbite decreased 1.2 mm owing to intrusion and protrusion of the lower incisors. The occlusal plane rotated 4.2º and the upper and lower dental arches were broadened during treatment. More dental expansion occurred in the upper arch in comparison. A questionnaire provided to patients two months into treatment indicated that the Forsus appliance did not cause pain or issues with sleep but patients reported minor 18 eating and speech problems, limited mouth opening, change in appearance and soft tissue discomfort. reportedly an issue. Oral hygiene was Two-thirds of the patients preferred the Forsus to the previous Class II appliance that was being used (headgear, activator, or interarch elastics).20 According to Vogt, the Forsus can be used in the place of Class II elastics or the Herbst appliance.21 It is indicated in patients with convex profiles but should not be used in Class II patients with protrusive maxillae or normal mandibles. 21 Jasper Jumper Jasper introduced a flexible fixed force module called the Jasper Jumper in 1987. The appliance is composed of a stainless steel spring that is covered by an opaque plastic covering.22 It is most commonly attached with a ball pin through the headgear tube of the first maxillary molar posteriorly and anteriorly it is connected to the lower arch wire. The lower premolar brackets are removed to allow increased movement. Alternatively, the appliance can be attached with “outriggers” (sectional bypass wires) in the lower arch to allow the premolars bonds to remain in place.22 The role of relative contributions of dental and skeletal changes to the overall treatment effects of Jasper 19 Jumpers is controversial. Cope et al.23 and Covell et al.24 suggest that the primary effect of Jasper Jumpers on Class II correction is dentoalveolar. Cope et al. demonstrated limited posterior displacement of the maxilla and only posterior rotation of the mandible, no significant effect on horizontal mandibular growth. Covell et al. found that forward maxillary growth was restricted but discovered no significant effect on mandibular growth. On the contrary, a study by Stucki and Ingervall indicated a slight retrusive effect on the maxilla and a significant increase in mandibular prognathism.25 The findings of Weiland and Bantleon also suggest a considerable orthopedic effect, concluding that 40% of the Class II correction is a result of skeletal changes while 60% is due to dentoalveolar alterations.26 They indicate that the skeletal correction occurred mainly in the mandible with the appliance producing an increase in mandibular growth and a mild reduction in maxillary horizontal development. The various studies that have investigated the effects of Jasper Jumpers tend to agree on the dentoalveolar changes that are produced by the appliance. The maxillary incisors are retracted and extruded while the mandibular incisors are proclined and intruded.23-25 The maxillary molars undergo distalization whereas the mandibular molars 20 are moved mesially.23-26 In addition, the Jasper Jumper produces expansive forces on the maxillary teeth.22 All of the studies showed a corrected Class I occlusion at the end of Jasper Jumper therapy in every patient.23-26 In comparison with the Herbst, the Jasper Jumper has several advantages.22 The amount of force is more easily controlled and the flexible modules offer increased patient comfort. Eating and brushing are less complicated with the Jasper Jumper. The most noteworthy drawbacks to the appliance are breakage, which occurs in 9% of the patients according to Stucki and Ingervall25 and undesired tooth movements. Intraoral Molar Distalization Appliances Maxillary molar distalizers have been developed as a minimal compliance method for Class II patients with reasonably good skeletal relationships and only mild or moderate space discrepancies in the maxillary arch. Molar distalizers are intra-arch appliances that often rely on the palatal vault and upper premolars and anterior teeth to provide anchorage for the distalization force. Proffit asserts that up to 6 mm of distal movement can be created with distalization.1 Even so, it is difficult to move maxillary molars bodily and to maintain the molar position after the molars have been distalized and the rest of the 21 maxillary dentition is retracted. Often times, the treatment approaches to retract anterior teeth after distalization require cooperation from the patient. Numerous appliances have been developed to distalize maxillary molars. Magnets Gianelly first described the use of repelling magnets for maxillary molar distalization in 1988. The magnets are attached on the upper fixed appliance in the buccal around the area of the first or second premolar and the first molar.27 In a study with ten consecutively treated patients with a mean age of 13.4 years, Bondemark and Kurol used intra-oral photographs, lateral radiographs and dental casts acquired pretreatment and after molar distalization to evaluate the dental effects produced.28 They found that magnets were successful at distalizing upper molars to a Class I relationship in all of the patients with a mean treatment time of 16.6 weeks. On average, the upper molars were moved distally 4.2 mm, tipped distally 8.0º, and rotated disto-buccally. Anchorage loss of roughly 1.5 mm was demonstrated by mesial movement of premolars, canines, and incisors. The upper incisors moved forward 1.8 mm and were tipped forward 6º. Gianelly, et al. indicated that 22 80% of the space created with molar distalization using magnets is attributable to distal movement of the molars.27 This method does not require patient compliance and can be successful at correcting Class II molars into a Class I relationship in a relatively short period of time (mean of 16.6 weeks, according to Bondemark and Kurol28). Nevertheless, the magnets are costly, lack corrosion resistance, and produce a great deal of distal molar tipping when bodily movement is more desirable.28 They also require frequent activation to maximize the force. Weekly activation has been recommended by Gianelly.27 NiTi Coil Springs NiTi coils have been used as a compliance-free method of distalizing upper molars. The appliance consists of a Nance button attached to the first premolars for anchorage control and 100 g coil springs positioned on the upper archwire between the first premolars and first molars.29 An uprighting spring can be used in the vertical slots of the first premolars for anchorage augmentation. A comparison of NiTi coil springs and magnets was performed to evaluate the dental effects of the two methods.30 The study involved 15 Class II patients evaluated cephalometrically and through dental model analysis. Each patient received a modified Nance appliance 23 attached to the upper first premolars along with magnetic devices on the right side and Ni-Ti open coil springs on the left. Coil springs produced significantly more distal molar movement than was found with the magnets. The amount of distal crown tip and distopalatal rotation produced by both techniques was not significant. All of the patients were successfully treated to a Class I molar relationship in 3 months, however, the NiTi coil springs were more effective and required less frequent activation.30 Pendulum The Pendulum appliance was first described by Hilgers in 1992. It utilizes a Nance appliance with auxiliary wires that can be soldered to bands on the premolars or deciduous molars or bonded to the occlusal surfaces of the teeth. Increasing the number of teeth in the anchorage unit, increases stability of the appliance.32 Two .036 inch TMA springs extend from the distal aspect of the acrylic button and when activated and inserted into the first maxillary molar lingual sheaths, provide the distalization force. If the upper arch requires expansion, an expansion screw can be added to the center of the Nance button. This appliance is referred to as the Pend-X. Byloff and Darendeliler evaluated the Pendulum appliance utilizing 200-250 g of distalization force to the 24 upper first molars in 13 patients with dental Class II malocclusions.31 The dental and skeletal effects were assessed with pretreatment and postdistalization cephalometric radiographs. weeks on the average. Pendulum therapy lasted 16.6 During this time, the maxillary first molar was moved distally 3.39 mm and tipped distally 14.5º. The rate of molar distal movement was 1.02 mm per month. The upper molars were intruded and second premolars were extruded. The maxillary second premolars moved mesially 1.63 mm. The upper incisors moved anteriorly and tipped labially but incisor anchorage loss was minimal. The Pendulum did not have any orthopedic effects.31 A study by Ghosh and Nanda used a larger sample size (41 subjects) to evaluate the dental effects of the Pendulum appliance.33 Their analysis used lateral cephalometric radiographs and dental models. They found that the mean amount of maxillary molar distalization was 3.37 mm with mean distal molar tipping of 8.36º. The first premolars were moved mesially 2.55 mm on average and tipped mesially 1.29º. Intrusion of the first molar was not statistically significant however the first premolar extruded 1.7 mm. Transverse molar widths were increased during appliance therapy. The results of the study indicated a mesiobuccal rotation of the first molar which 25 is favorable in Class II treatment and according to the authors, may be caused by the arc created by the spring when it moves distally.33 The Pendulum appliance has the benefits of minimal reliance on patient compliance and simple construction and activation.33 It can be used to increase maxillary transverse width when necessary. The large amount of molar tipping should be considered when planning treatment using this appliance. Jones Jig The Jones Jig, developed by Jones, uses an open-coil NiTi spring in a jig assembly to provide distalization force to the maxillary first molars. A modified Nance button with auxiliary wires attached to the upper first or second premolars or the deciduous molars acts as the anchorage unit. The Jones Jig provides 70-75 g of force when it is activated by compression of the NiTi coil spring.34 Evaluations of the Jones Jig demonstrate a dental Class II correction with orthopedic alterations. As with other intraoral molar distalizers, the maxillary first molars are moved distally which results in anchorage loss that is revealed by mesial movement and tipping of the maxillary premolars.35-36 Gulati, et al showed that the 26 appliance causes significant distal tipping and distopalatal rotation of the upper first molars.35 The appliance causes maxillary molar extrusion and an increase in the mandibular plane angle.35 According to Jones and White, Class II malocclusion caused by maxillary molar rotation alone can be corrected in 90-120 days while true Class II molar relationships can be corrected in 120-180 days.34 Distal Jet The Distal Jet was developed by Carano and Testa in 1996 (Figure 2.1). The original design of the appliance consists of a bilateral piston and tube assembly. The .036 inch internal diameter tubes are embedded in an acrylic Nance button in the palate. A wire extends from the tube, like a piston, runs posteriorly parallel to the occlusal plane, and ends in a bayonet bend that is inserted into the lingual sheath on the first molar band. Each tube has a NiTi open-coil spring and screw-clamp that provides the distalization force. The appliance is supported by an anchor wire from the Nance button to bands on the second premolars. Every four to six weeks, the coil spring is reactivated by moving the screw-clamp distally to compress the spring. The clamp is locked in place by tightening the mesial set-screw with a small Allen wrench. 27 In 1996, Carano and Testa recommended 160 g NiTi coil springs for children and 250 g springs for adults.37 Alternatively, stainless steel springs can be used in the place of NiTi. One advantage of the Distal Jet is the ability to convert the appliance to a Nance holding arch after the desired molar position has been obtained. A solid extension is formed by flowing light-cured acrylic around the coil spring, set-screw, and the distal bayonet bend. The premolar supporting wires can be sectioned at the Nance button with a high speed to allow retraction of the anterior teeth. Figure 2.1: Diagram of the original bilateral tube and piston design of the Distal Jet (photo used by permission of Dynaflex) 28 Several modifications have been made to improve the ease of use and functionality of the Distal Jet.38 A variation that includes two set screws in the activation collar makes the transition to a Nance holding arch easier, cleaner, and more reliable.38 The mesial set screw is still used during the active distalization phase but when distal movement is completed, the collar is moved mesially so that the spring can be pulled from the wire with a plier. The collar is then locked into place at the junction of the tube and wire. The mesial set screw is tightened onto the tube and the distal set screw is tightened onto the wire to lock the tube and piston together. With the Bowman modification, the tube and piston arrangement was replaced with a rigid tracking wire. This variation simplifies the conversion to a holding arch following distalization. The coil springs are left in place, the hex screws are locked, and the premolar supporting wires are sectioned. Variations can be included such as helical loops in the bayonet wires to produce distal maxillary molar rotation or to upright mesially tipped molars.38 Limited maxillary expansion can be accomplished by embedding a jackscrew in the Nance palatal button.38 The terminal ends of the Distal Jet can be adjusted to provide molar rotation 29 correction.39 Carano, et al. recommend rotation correction before activating the appliance for distalization.39 A variation on the design of the Distal Jet can be used to upright lower molars that have tipped mesially.40 Carano and associates contend that the appliance is comfortable, uncomplicated to insert, and has an insignificant extrusive component.39 Some advantages of the Distal Jet are good esthetics, comfort, and ease of insertion and activation.41 Carano and Testa indicate that the Distal Jet can produce bodily movement of the maxillary molars because the line of force is through the center of resistance of the first molar.37 It can be used for both unilateral and bilateral Class II correction.41 Bowman advocates overcorrection of the maxillary molar to a super Class I by 2 mm as has been suggested by Hilgers. Additionally, it has been suggested that auxiliaries such as headgear or elastics can be used if there is an increase of more than 1 mm in overjet during distalization, an idea that was first proposed by Gianelly.28 Two studies have examined the forces and moments created by the Distal Jet during molar distalization.43,44 Kinzinger and Diedrich conducted an in vitro study of three lab-fabricated appliances using a 3D metering device.43 30 Their results indicate that the Distal Jet produces distalizing forces with uprighting moments. There are forces and moments that are buccally directed and, because the force is palatal to the center of rotation, it acts to rotate the first molars mesio-palatally. The forces remain uniform because the coil is reactivated frequently. They relate that if a patient’s palate is shallow, the amount of molar distal tipping can be increased because of the inability to direct the line of force through the molar’s center of resistance. Uprighting activation can be used to compensate for distal tip of the molar and a toe-in bend can be used to counteract the rotational moment. The authors, however, indicate that these adjustments cause an increase in friction which therefore would hinder the distal movement of the molar and should not be used. They recommend overcorrection to a super Class I so that uprighting can occur. They also advocate the use of a TPA or bihelix to rotate the molars.43 Nishii, et al. scanned and superimposed pre- and postdistalization casts to evaluate the effects of the Distal Jet on the maxillary teeth 3-dimensionally.44 Their results indicate a mean maxillary first molar distalization of 2.4 mm, distal tip of 1.8º, lateral expansion of 1.2 mm, and vertical extrusion of 0.5 mm. The second premolars moved 31 mesially 1.4 mm, expanded laterally by 0.3 mm, and extruded 0.5 mm. The upper incisors moved mesially 2.4 mm and tipped mesially 4.5º while extruding 0.3 mm. Measurements of pre- and post-distalization cephalograms indicated no significant skeletal changes but the Y-axis, lower face height, and mandibular plane were increased. The monthly mean molar distalization rate was 0.4 mm.44 A study of the Distal Jet was conducted by Ngantung, et al. to evaluate the effects of the appliance on the maxillary teeth and the outcomes following orthodontic treatment.41 Pre-treatment, post-distalization, and post- treatment lateral cephalograms of 21 female and 12 male patients with a mean age of 12.8 years were used. Bands were cemented on the maxillary first molars and second bicuspids. All of the subjects had full fixed appliances during distalization and Jasper Jumpers were used to maintain the molar distalization. The maxillary molar distalization phase averaged 6.7 months in length while mean total treatment time was 25.7 months. The maxillary first molars were distalized 2.1 mm and were distally tipped 3.3º while the second premolars moved mesially 2.6 mm and were distally tipped 4.3º. The distal tipping of the second premolars is in contrast to that found with the Pendulum and Jones Jig which tip the premolars mesially. 32 The maxillary second molars were also moved distally 2.6 mm. The maxillary incisors exhibited anchorage loss from the distalization force. The upper incisor to SN increased 12.2º and overjet was increased by 1.7 mm. They found an increase in lower anterior face height of 2.4 mm and the upper and lower lips to E plane increased during the distalization phase. At the end of treatment, the maxillary first and second molars were positioned mesially, tipped mesially, and extruded. An interesting finding was that the maxillary first molars finished treatment more mesially than when they started. The maxillary second premolars were positioned distally and tipped mesially. The upper incisor was uprighted and extruded. The final angulation of the upper incisors was nearly ideal. The upper and lower lips to E plane decreased. The investigators concluded that the Distal Jet generated less tipping of maxillary molars and better bodily movement when compared to the Pendulum and Jones Jig. According to the authors, reduction of distalization force is not effective in deterring anchorage loss (the Jones Jig utilizes 75 g of force, while the Distal Jet uses 240 g). They indicate that the Distal Jet should not be used on patients with full profiles, high FMAs, anterior open bites, or significant crowding.41 33 Bolla et al. assessed the effectiveness of the Distal Jet used independent of multibracket appliances.45 In their study, the bicuspids and canines were retracted one tooth at a time using .017 x.025 NiTi sectional wires and power chain. A utility arch was used for incisor retraction. In five months, the upper first molars moved distally 3.2 mm and tipped distally 3.1º. The upper first premolars moved mesially 1.3 mm and tipped distally by 2.8º. They found no significant change in upper incisor position, overjet, lower facial height, or mandibular plane angle. Seventy- one percent of the space created during distalization was from distal molar movement while 29% was from anchorage loss. The distalization force was increased from 180 g to 240 g if the patient had second molars.45 There are several studies comparing the Distal Jet to other methods of Class II correction in terms of efficiency, degree of undesired side effects.46 Chiu, et al. compared the dental and skeletal effects of the Distal Jet and Pendulum. The Distal Jet group had concurrent full fixed appliances during molar distalization while fixed appliances were delayed in the Pendulum group until the distalization had been completed. The study consisted of two groups of 32 Class II division 1 patients with a mean age of 12 years 3 months in the Distal Jet group and 12 34 years 6 months in the Pendulum group. were analyzed at three time points: Lateral cephalograms pretreatment, postdistalization and posttreatment for skeletal and dental differences. During treatment in both groups, the mandibular plane angle opened, increasing lower anterior facial height. The authors point out that this effect of the Distal Jet and the Pendulum on the vertical dimension has been observed in other studies. In the Pendulum group, molar distalization was significantly greater but the molars were also tipped distally to a greater degree. Nevertheless, when the amount of distal movement was considered, the Distal Jet was equally as likely to tip the molars (each mm of distal movement corresponded to 1.8º of distal tip). Less anchorage loss, when measured at the first premolars, was found in the Pendulum group. The maxillary incisors in the Distal Jet group exhibited more flaring and intrusion and the overjet was increased significantly more than in the Pendulum group. The investigators attribute the differences in premolar anchorage loss to the fact that the Pendulum utilizes four premolars instead of two in the anchorage unit. They credit the incisor anchorage loss to the use of full fixed appliances in the Distal Jet group. The Pendulum was shown to be more efficient (distalization took seven months 35 instead of ten). On the whole, during treatment, the maxillary molars finished in a more mesial location than their original position in the Distal Jet group but the overall molar correction was the same in both groups.46 Bolla et al. conducted a study evaluating the nature of maxillary molar movement and degree of anchorage loss with the Distal Jet with the intention of comparing it to other molar distalizers.47 The sample consisted of 20 subjects with a mean age of 12.6. Pre- and post- distalization lateral cephalograms and dental models were analyzed. The results indicated that the average distalization phase took five months to distalize molars 3.2 mm and distally tip them 3.1º. First bicuspids were moved mesially 1.3 mm and tipped distally 2.8º. The first molars were extruded 0.5 mm while the first premolars were extruded 1.1 mm. The maxillary incisors and overjet were not significantly changed and there was an insignificant increase in lower anterior facial height. The molars were expanded laterally and mildly rotated mesio-palatally. Other appliances such as the Pendulum, Jones Jig, Greenfield appliance and sagittal appliance display a more advantageous distal rotation of the upper molars but also exhibit molar constriction which is unfavorable in Class II treatment. They noted that if recovery from tipping is 36 taken into account, the total space created by the Pendulum, Distal Jet with fixed appliances, and Distal Jet alone is approximately the same.47 A literature review was conducted by Kinzinger et al. to assess the treatment effects of several appliances that use intramaxillary anchorage for distalization.48 After reviewing 85 articles, 22 were included in the analysis. The longest linear amount of molar distalization was found with the Pendulum which also exhibited the greatest amount of tipping. Vertical movements of molars were minimal with the least amount of vertical side-effects found with the Distal Jet, the Pendulum exhibited the greatest amount of intrusion and the Jones Jig had the highest amount of extrusion. The Jones Jig and Pendulum displayed the smallest amount of premolar anchorage loss. The smallest amount of premolar tipping was found with the Distal Jet and Pendulum while the Jones Jig demonstrated the most tipping. The incisors were mesialized the most and displayed the largest protrusion with the Distal Jet that utilized two anchorage teeth. The Jones Jig showed the least amount of incisor mesialization. The highest effective molar distalization was found with the Pendulum but the authors point out that there is also a significant amount of distal tipping therefore subsequent uprighting 37 reduces the space. The First Class appliance and the Distal Jet had the highest efficiency (greatest amount of distalization with the least amount of anchorage loss). The authors recommend that the anchorage unit have as many teeth as possible and indicate that deciduous molars can act as anchorage but will perform this task with lesser quality than that provided by premolars. They point out that anchorage loss is more marked in the incisors than in the first premolars with maxillary distalizers.48 Simplified Molar Distalizer (Frog) The Simplified Molar Distalizer (SMD), or Frog, was introduced by Walde in 2003 (Figure 2.2).49 The design of the Frog consists of a modified Nance button with embedded .028-inch stainless steel wires that are bonded to either two or four premolars or deciduous molars. The appliance also includes an expansion screw and a removable spring bent from a .032-inch stainless steel or TMA wire with adjustment loops used for fine tuning and double back bends for insertion into the lingual sheaths of the upper first molar bands. The appliance is activated by inserting the activation tool into the head of the screw and rotating it counterclockwise. Each 360º rotation of the screw opens the appliance approximately 0.5 mm and the appliance can be reactivated at four-to-eight-week intervals. 38 Multiple turns of the screw can be made at each patient visit. According to Walde, the Frog can produce 1-2 mm of maxillary molar movement per month. Conversion to a Nance holding arch is accomplished by sealing the screw with acrylic or composite resin and severing the connections to the premolars from the Nance button. Figure 2.2: Diagram of the Frog appliance (photo used by permission of Dynaflex) Walde relates that there are several advantages of the Frog which include easy assembly and activation, threedimensional molar control, and an easily removable and adjustable distalizing spring. It can be used for bilateral or unilateral molar distalization and when second molars are fully erupted. There is minimal requirement for 39 patient cooperation and the appliance has an aesthetic appearance. Walde maintains that appliance placement is critical and correct placement will result in bodily molar movement. The appliance should be positioned approximately at the trifurcation of the upper molars which is generally 10-12 mm from the occlusal surface. According to Walde, this position places the distalization force at the center of resistance of the molars for bodily tooth movement. If the appliance is placed too far occlusally more crown tipping will occur, too far apically, more root tipping will occur.49 Distalizing and Second Molars Several studies have investigated the influence of erupted second molars on the amount and rate of distalization, the amount of molar tipping, and the degree of anchorage loss. The results are controversial. Some studies have concluded that the position of the second molars has no effect on the amount of distal molar movement, molar tipping, or anchorage loss.33,34,50 Some have noted that distal molar movement appears to be more efficient before second molar eruption.32 According to Bolla et al, there is less molar tipping and less loss of anchorage when second molars are partially or completely 40 erupted but there is no significant difference in the amount of distalization.45,47 Summary and Statement of Thesis The purpose of this investigation is to compare and contrast the dental effects of two maxillary molar distalizers: the Distal Jet and the Frog. Multiple studies have investigated the dental effects of the Distal Jet but studies of the Frog have not been reported. Comparisons will be made based on the amount and rate of maxillary molar distal movement and the degree of distal tipping. Anchorage loss will be determined from the amount of anterior movement of incisors and the extent of labial tipping. The original Distal Jet design will be compared to a modification made by Bowman that replaces the tube and piston arrangement with a rigid wire. The modification has been said to significantly diminish anchorage loss.51 The eruption of second molars will be evaluated to determine if there is an effect on the amount of molar distalization or anchorage loss. 41 References 1. Proffit WR, Fields HW, Sarver DM. Contemporary Orthodontics. 4th ed. St. Louis, MO: Mosby Elsevier, 2007. 2. Proffit WR, Fields, HW, Moray, LJ. Prevalence of malocclusion and orthodontic treatment need in the United States: Estimates from the NHANES III survey. Int J Adult Orthodon Orthognath Surg. 1998;13:97-106. 3. McNamara, JA. Components of Class II malocclusion in children 8-10 years of age. Angle Orthod. 1981;51:177-202. 4. Bos A, Kleverlaan, CJ, Hoogstraten J, Prahl-Andersen B, Kuitert R. Comparing subjective and objective measures of headgear compliance. Am J Orthod Dentofacial Orthop. 2007;132:801-805. 5. Sahm G, Bartsch A, Witt E. Reliability of patient reports on compliance. Eur J Orthod. 1990;12:438-446. 6. Nanda RS, Kierl MJ. Prediction of cooperation in orthodontic treatment. Am J Orthod Dentofacial Orthop. 1992;102:16-21. 7. Brandão M, Pinho HS, Urias D. Clinical and quantitative assessment of headgear compliance: a pilot study. Am J Orthod Dentofacial Orthop. 2006;129:239-244. 8. Egolf RJ, BeGole EA, Upshaw HS. Factors associated with orthodontic patient compliance with intraoral elastic and headgear wear. Am J Orthod Dentofacial Orthop. 1990;97:336-348. 9. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors influencing treatment time in orthodontic patients. Am J Orthod Dentofacial Orthop. 2006;129:230-238. 10. McSherry PF, Bradley H. Class II correction-reducing patient compliance: a review of the available techniques. J Orthod. 2000;27:219-225. 42 11. Beckwith FR, Ackerman RJ, Cobb CM, Tira DE. An evaluation of factors affecting duration of orthodontic treatment. Am J Orthod Dentofacial Orthop. 1999;116:439-447. 12. Graber TM, Vanarsdall RL, Vig KWL. Orthodontics: Current Principles and Techniques. 4th ed. St. Louis, MO: Mosby Elsevier, 2005. 13. Pancherz H. Treatment of Class II malocclusions by jumping the bite with the Herbst appliance. A cephalometric investigation. Am J Orthod. 1979;76:423442. 14. Pancherz H. The mechanism of Class II correction in Herbst appliance treatment. A cephalometric investigation. Am J Orthod. 1982;82:104-113. 15. Pancherz H. The effects, limitations, and long-term dentofacial adaptations to treatment with the Herbst appliance. Semin Orthod. 1997;3:232-243. 16. Pangrazio-Kulbersh V, Berger JL, Chermak DS, et al. Treatment effects of the mandibular anterior repositioning appliance on patients with Class II malocclusion. Am J Orthod Dentofacial Orthop. 2003;123:286-295. 17. Coelho Filho CM. The Mandibular Protraction Appliance No. 3. J Clin Orthod. 1998;32:379-384. 18. Coelho Filho CM. Mandibular protraction appliance IV. J Clin Orthod. 2001;35:18-24. 19. Alves PFR, Oliveira AG. A comparison of the skeletal, dental, and soft tissue effects caused by Herbst and Mandibular Protraction Appliances in the treatment of mandibular Class II malocclusions. World J Orthod. 2008;9:1-19. 20. Heinig N, Göz G. Clinical application and effects of the Forsus spring. A study of a new Herbst hybrid. J Orofac Orthop. 2001;62:436-450. 21. Vogt W. The Forsus Fatigue Resistant Device. J Clin Orthod. 2006;40:368-377. 43 22. Jasper JJ, McNamara JA. The correction of interarch malocclusions using a fixed force module. Am J Orthod Dentofacial Orthop. 1995;108:641-650. 23. Cope JB, Buschang PH, Cope DD, Parker J, Blackwood HO. Quantitative evaluation of craniofacial changes with Jasper Jumper therapy. Angle Orthod. 1994;64:113-122. 24. Covell DA, Trammell DW, Boero RP, West R. A cephalometric study of class II Division 1 malocclusions treated with the Jasper Jumper appliance. Angle Orthod. 1999;69:311-320. 25. Stucki N, Ingervall B. The use of the Jasper Jumper for the correction of Class II malocclusion in the young permanent dentition. Eur J Orthod. 1998;20:271281. 26. Weiland FJ, Bantleon HP. Treatment of Class II malocclusions with the Jasper Jumper appliance--a preliminary report. Am J Orthod Dentofacial Orthop. 1995;108:341-350. 27. Gianelly AA, Vaitas AS, Thomas WM. The use of magnets to move molars distally. Am J Orthod Dentofacial Orthop. 1989;96:161-167. 28. Bondemark L, Kurol J. Distalization of maxillary first and second molars simultaneously with repelling magnets. Eur J Orthod. 1992;14:264-272. 29. Gianelly AA, Bednar J, Dietz VS. Japanese NiTi coils used to move molars distally. Am J Orthod Dentofacial Orthop. 1991;99:564-566. 30. Erverdi N, Koyutürk O, Küçükkeles N. Nickel-titanium coil springs and repelling magnets: a comparison of two different intra-oral molar distalization techniques. Br J Orthod. 1997;24:47-53. 31. Byloff FK, Darendeliler MA. Distal molar movement using the Pendulum appliance. Part 1: Clinical and radiological evaluation. Angle Orthod. 1997;67:249260. 44 32. Hilgers JJ. The Pendulum appliance for Class II noncompliance therapy. J Clin Orthod. 1992;26:706-714. 33. Ghosh J, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod Dentofacial Orthop. 1996;110:639-646. 34. Jones RD, White JM. Rapid Class II molar correction with an open-coil jig. J Clin Orthod. 1992;26:661-664. 35. Gulati S, Kharbanda OP, Parkash H. Dental and skeletal changes after intraoral molar distalization with sectional jig assembly. Am J Orthod Dentofacial Orthop. 1998;114:319-327. 36. Runge ME, Martin JT, Bukai F. Analysis of rapid maxillary molar distal movement without patient cooperation. Am J Orthod Dentofacial Orthop. 1999;115:153-157. 37. Carano A, Testa M. The Distal Jet for upper molar distalization. J Clin Orthod. 1996;30:374-380. 38. Bowman SJ. Modifications of the Distal Jet. J Clin Orthod. 1998;32:549-556. 39. Carano A, Testa M, Bowman SJ. The Distal Jet simplified and updated. J Clin Orthod. 2002;36:586590. 40. Carano A, Testa M, Siciliani G. The Distal Jet for uprighting lower molars. J Clin Orthod. 1996;30:707710. 41. Ngantung V, Nanda RS, Bowman SJ. Posttreatment evaluation of the Distal Jet appliance. Am J Orthod Dentofacial Orthop. 2001;120:178-185. 42. Bowman SJ. Class II combination therapy (Distal Jet and Jasper Jumpers): a case report. J Orthod. 2000;27:213-218. 43. Kinzinger GSM, Diedrich PR. Biomechanics of a Distal Jet appliance. Theoretical considerations and in vitro analysis of force systems. Angle Orthod. 2008;78:676681. 45 44. Nishii Y, Katada H, Yamaguchi H. Three-dimensional evaluation of the Distal Jet appliance. World J Orthod. 2002;3:321-327. 45. Bolla E, Doldo T, Giorgetti R. Distal movement of maxillary canines and premolars with sectional mechanics following Distal Jet application to molars. Prog Orthod. 2004;5:72-89. 46. Chiu PP, McNamara JA, Franchi L. A comparison of two intraoral molar distalization appliances: Distal Jet versus Pendulum. Am J Orthod Dentofacial Orthop. 2005;128:353-365. 47. Bolla E, Muratore F, Carano A, Bowman SJ. Evaluation of maxillary molar distalization with the Distal Jet: a comparison with other contemporary methods. Angle Orthod. 2002;72:481-494. 48. Kinzinger GSM, Eren M, Diedrich PR. Treatment effects of intraoral appliances with conventional anchorage designs for non-compliance maxillary molar distalization: a literature review. Eur J Orthod. 2008;30:558-571. 49. Walde KC. The simplified molar distalizer. J Clin Orthod. 2003;37:616-619. 50. Byloff FK, Darendeliler MA, Clar E, Darendeliler A. Distal molar movement using the Pendulum appliance. Part 2: The effects of maxillary molar root uprighting bends. Angle Orthod. 1997;67:261-270. 51. Bowman SJ. Class II combination therapy: Molar distalization and fixed functional. In: Current Concepts in Clinical Orthodontics, Elsevier, in press. 46 CHAPTER 3: JOURNAL ARTICLE Abstract Purpose: The objective of this study was to compare the dental effects of the Distal Jet and the Frog, two types of molar distalizers. The position of the upper second molars was also evaluated to determine if second molar eruption affected the dental changes caused by the distalization appliances or the rate of distalization. Materials and Methods: The investigation was a retrospective, clinical study of 79 Distal Jet patients with a mean initial age of 13.6 years and 29 Frog patients with a mean age of 11.5 years. The Frog and Distal Jet samples were matched according to initial age and gender. Pretreatment (T1) and postdistalization (T2) lateral cephalograms were traced and analyzed with the pitchfork analysis. The long axes of the upper first molar and upper incisor were measured relative to the functional occlusal plane to evaluate angular changes in these teeth. Variations in design of the Distal Jet appliance were assessed by comparing the original tube and piston design to the Bowman modification. The dental effects and rate of the distalization appliances were compared when second 47 molars were erupted or unerupted. Independent t-tests were used to assess differences between groups. Results: The original tube and piston design of the Distal Jet exhibited a significantly significant greater amount of horizontal molar movement over a shorter period of time. Patients treated with the Frog and both appliance designs of the Distal Jet exhibited a general trend for mesial movement of the maxilla, mandible, and dentition. The Distal Jet produced significantly more molar distalization than the Frog in a shorter period of time. Greater mesial movement of the lower incisors and lower molars was seen in the Distal Jet group when compared to the patients treated with the Frog. More incisor anchorage loss was observed when distalizer therapy was initiated after second molars erupted. Conclusions: The original design of the Distal Jet appliance produces greater distal maxillary molar movement in a shorter period of time when compared to the Bowman modification. The Distal Jet and the Frog are effective at correcting Class II malocclusions although the Distal Jet is a more efficient means of molar distalization. Molar distalization after second molar eruption causes more incisor anchorage loss than that produced when second molars are unerupted. 48 Introduction Persons with Class II malocclusions represent a significant proportion of the population. According to NHANES III, which classified individuals as Class II when 5 mm or more overjet was displayed, Class II malocclusion occurs in 23% of children, 16% of adolescents, and 13% of adults.1 Multiple techniques for correction of Class II malocclusions are employed in orthodontic practices. These include fixed and removable appliances, extraction of teeth, and orthognathic surgery.2 Difficulty acquiring patient compliance has resulted in decreased success and more challenging orthodontic treatment when some of the methods for Class II correction, such as headgears, removable appliances, and intermaxillary elastics are utilized.3 A lack of patient compliance can result in increased treatment time.4,5 Minimal compliance techniques, such as maxillary molar distalization appliances, have been utilized to reduce the problems associated with methods that require cooperation. Examples of these appliances include the Pendulum, Jones Jig, Distal Jet, magnets, and NiTi coil springs. These appliances are effective at translating Class II maxillary molars into Class I occlusion but can result in undesirable 49 side effects such as maxillary molar tipping and incisor proclination. The Distal Jet was developed by Carano and Testa in 1996. The appliance derives its force from a bilateral tube and piston assembly that is embedded in a Nance acrylic button that serves to resist the forces produced during distalization. Several modifications have been made to the original design in an attempt to improve the efficiency of the appliance. Several studies have examined the effects of the Distal Jet7,8,9,10 and compared them to other molar distalizing appliances.11,12,13 The Frog was developed by Walde. It was introduced in 2003.14 The Frog derives its distalization force from an expansion screw that is embedded in a Nance palatal button. Stainless steel wires are bonded to the upper first and second premolars. There are no published reports on the effects of the Frog on the maxillary dentition. The purpose of this study is to examine the effects of the Distal Jet and Frog on the dentition and compare the appliances with regard to the amount and rate of maxillary molar distalization and the degree of unwanted side effects. Further, the position of upper second molars will be evaluated to determine if their presence affects the magnitude or quality of molar distalization. 50 Materials and Methods Sample Class II patients treated with non-implant supported molar distalization appliances were evaluated in this study. Two groups of subjects treated with either the Distal Jet (AOA) or the Frog (Forestadent) appliance (78 Distal Jet and 29 Frog) were selected from the offices of two practicing orthodontists. Dr. Jay Bowman (Kalamazoo, MI) supplied the Distal Jet sample while the Frog sample was obtained from the office of Dr. Kevin Walde (Washington, MO). The Distal Jet sample was further classified according to appliance design and whether the upper anterior teeth had brackets placed prior to distalization therapy. Of the 78 Distal Jet patients, 16 had the original tube and piston design of the Distal Jet. These patients had bands on the first premolars and the upper incisors were bonded prior to distalization. The balance of the sample had the Bowman modification of the Distal Jet in which the tube and piston is replaced with a rigid wire and two locking collars. Of those 63 patients with the Bowman modified Distal Jet, 24 had incisor brackets placed before distalization. The balance of the sample (39) was not bracketed prior to Distal Jet activation. Further, in 19 of these 39 patients, occlusal 51 rests on the first premolars were utilized instead of premolar bands. The entire sample of Frog patients had brackets bonded to the upper incisors prior to distalization and anchor wires were used in the distal embrasures of the upper first and second premolars. All of the patients (Distal Jet and Frog) had the lower arch fully bonded during distalizer therapy. Lateral cephalograms taken before treatment was initiated (T1) and immediately following the molar distalization phase (T2) were acquired. Additionally, patient records were examined for information regarding each patient’s age, gender, length of distalizer therapy, and total treatment time. The inclusion criteria utilized for patient selection were: Pre-treatment Class II malocclusion No permanent teeth extracted (excluding third molars) Diagnostic quality lateral cephalograms before treatment and immediately following molar distalization No other means of molar distalization utilized between T1 and T2 Bilateral distalization Variation in treatment mechanics was minimized by using samples from only two practitioners. The upper first molars were corrected to a Class I or super Class I 52 relationship in all of the patients. Other Class II appliances such as Jasper Jumpers, Forsus, or Class II elastics were utilized in some of the patients following T2 in order to maintain the position of the distalized molars during subsequent retraction of the upper teeth. Data Collection The pretreatment and postdistalization cephalometric radiographs were either traced electronically using Dolphin imaging software (Frog sample) or hand-traced on acetate (Distal Jet) by the same investigator. The electronic radiographs were then printed and hand-traced on acetate. Pre-treatment (T1) and post-distalization (T2) tracings were superimposed using the Pitchfork analysis as described by Johnston.14 The pitchfork analysis allows the maxillary and mandibular translatory growth changes relative to the cranial base and the dental changes relative to the basal bone to be measured (See Fig. 3.1 and Appendix, Table A.1). The sum of the maxillary and mandibular skeletal changes, ABCH, represents the net effect of skeletal growth. When the value for the ABCH is summed with the change in upper and lower first molar movements, the overall change in molar relationship can be determined. The analysis also allows the change in upper and lower incisors to be 53 measured and when this value is added to the ABCH, the change in overjet can be determined. Each measurement is given a sign relative to its impact on the Class II malocclusion: positive if it tends to improve the Class II relationship or reduce overjet, negative if it worsens the Class II relationship or increases overjet. All measurements are made along the mean functional occlusal plane, an average of the T1 and T2 functional occlusal planes, defined by the premolars and first molars. Measurements were carried out with digital calipers (Mitutoyo), as suggested by Johnston, to the nearest tenth of a millimeter.14 Figure 3.1: Diagram of the variables included in the pitchfork analysis. Skeletal and dental changes are measured relative to the basal bone.14 54 Because maxillary molar distalizers are likely to produce angular changes of the upper first molars and upper incisors, the angulations of these teeth were measured by hand relative to the occlusal plane. The upper second molars were classified as unerupted if they were at the level of the CEJ of the upper first molar or higher and erupted if they were below the level of the upper first molar CEJ. The sample of patients treated with the Frog was matched with Distal Jet patients on the basis of age. The angular changes of upper first molars and incisors and results of the Pitchfork analysis were compared. The Distal Jet sample was compared according to the version of the appliance used (original tube and piston version or the Bowman modification). Dental changes produced by distalization therapy along with the time required for distalization and the rate of distalization were compared when second molars were erupted or unerupted. Statistical Methods SPSS 15.0 for Windows (IBM) was used for statistical analysis of the data. Levene’s test was used to assess the equality of variances before performing the independent two-sample t test to evaluate differences between the 55 groups. Differences between groups were considered statistically significant when p < .05. Intra-examiner reliability was tested by random selection of 10% of the original sample which was retraced and superimposed. All of the measurements were carried out again and evaluated with the Cronbach’s Alpha test. The intraclass correlation coefficient was 0.938. Results Cephalometric comparison of the original design (Group 1)and the Bowman modification (Group 2) of the Distal Jet (See Appendix Table A.2 and Table A.3) revealed minimal differences. The pitchfork analysis demonstrated that the maxilla moved mesially relative to the cranial base (0.26 mm in Group 1 and .019 mm in Group 2). The mandible also exhibited mesial movement of 0.74 mm in Group 1 and 0.57 mm in Group 2, on average. The apical base change was 0.44 mm in Group 1 and .37 mm in Group 2. In both groups the upper molar was distalized and tipped distally, the upper incisor was moved mesially and tipped labially, and the lower first molar and lower incisor moved mesially. Group 1 exhibited 2.7 mm of distal molar movement and 4.7º of distal tipping. The upper incisor moved forward 3.2 mm and was flared 11.2º. The total change in molar position was 4.3 mm with the lower molar moving forward 1.1 mm. 56 The lower incisor moved forward 1.9 mm and the change in overjet was 0.7 mm. In Group 2, there was 3.9 mm of distal molar movement with 4.6º of distal tipping. The upper incisor moved forward 3.9 mm and tipped 8.6º. The lower molar and lower incisor were moved mesially, 0.8 mm and 2.1 mm, respectively. The total molar change was 5.1 mm while the overjet increased 0.6 mm. The total treatment time was 27.5 months in Group 1 and 30.0 months in Group 2. The time required for distalization was 7.0 months in Group 1 and 7.7 months in Group 2. The amount of distal molar movement per month was .41 mm in Group 1 and 0.53 mm in Group 2. Statistically significant differences were found in the amount of molar distalization (U6) and rate (mm of molar distalization/month) of distalization. These differences were considered to be minimal so these groups were combined. The group of patients treated with the Frog appliance was matched according to age to the Distal Jet group without regard to the version of Distal Jet appliance used (Table 3.1). The pitchfork analysis revealed a trend toward mesial movement of the maxilla and mandible in the Distal Jet and the Frog samples (Table 3.2). The ABCH was 0.6 mm in the Distal Jet group and 0.4 mm in the Frog group, on average. The maxilla and mandible moved forward 57 Table 3.1: Sample characteristics of age-matched Distal Jet and Frog samples Table 3.2: Comparison of age-matched Distal Jet and Frog samples 58 Selected variables were compared when patients had second molars erupted or unerupted in order to determine if the presence of second molars affected the amount or rate of molar distalization, degree of molar tipping, or the amount of anchorage loss at the incisors (Table 3.3). Distal Jet and Frog patients were classified according to the amount of eruption noted on the lateral cephalograms. Molars were considered unerupted if they were at or above the level of the CEJ and erupted if they were below the level of the CEJ. Of the total sample of patients, 58 were deemed to have erupted second molars while in 50 of the patients, second molars were unerupted. The amount of molar distalization and degree of molar distal tipping were 3.5 mm and 5.3º, respectively on average, if the second molars were unerupted and 3.3 mm and 3.9º when they were erupted. In the group with unerupted second molars, the upper incisors moved mesially 2.4 mm and tipped labially 8.1º. The amount of overjet increased by 0.3 mm. The time required for distalization was 7.3 months, on average, in this group and the rate of distalization was 0.5 mm/month. The patients with second molars erupted exhibited 3.2 mm of mesial incisor movement and 8.9º of incisor flaring. amount of overjet was increased by 1.0 mm. The It took 7.7 months, on average, to distalize the molars and there was 59 0.4 mm/month of distal molar movement. The only statistically significant difference between the groups was found in the amount of mesial movement of the upper incisors. Table 3.3: Comparison of patients on the basis of second molar position Discussion In previous published studies the Distal Jet appliance has been compared to many various techniques used to distalize molars including the Pendulum, Jones Jig, magnets, and NiTi coil springs. The Distal Jet has proven to be an effective, reliable method of Class II correction. The present retrospective study compares the dental and skeletal effects in 78 patients treated with the Distal Jet appliance and 29 patients treated with the Frog. 60 To date, there are no published studies that examine the effects of the Frog. Distal Jet and Frog patients that were matched according to age and gender were compared (Table 3.2). In both groups, skeletal changes were observed with a trend for mesial movement of the maxilla and mandible relative to the cranial base which is the normal growth pattern. The skeletal changes seen between the groups were not statistically significant as would be expected. The trend for dental changes produced by the molar distalizers in this investigation agrees with the results of previous studies. The maxillary molars were moved distally and tipped distally due to the line of force acting below the center of rotation. Anchorage loss was observed in the form of upper incisor mesial movement and flaring. Both appliances were effective at moving the maxillary molars into a Class I relationship. The Distal Jet group exhibited 3.6 mm of distal maxillary molar movement and 4.7º of molar distal tipping, on average. The Frog appliance translated the maxillary molar a mean of 2.6 mm with 4.4º of tipping. The amount of maxillary molar movement and the change in molar relationship was statistically significant. Since the pretreatment 61 characteristics of the patients were not examined, this difference could be explained by a greater Class II molar discrepancy in the Distal Jet group at the start of treatment. When employing molar distalizers, clinicians will typically activate the appliance until the upper molar is in a Class I or super Class I relationship at which time the appliance is converted into a holding arch to help maintain the distalized molar position. If the Class II relationship in the Distal Jet group was more severe at the beginning of treatment, greater amounts of molar distalization would be required to correct the relationship. The lower molar and lower incisor moved mesially in both samples. This trend can be explained because the lower arch was bonded in all of the patients and orthodontic appliances cause a general mesial migration of teeth. The amount of lower molar and lower incisor movement between the groups was considered statistically significant. In the Distal Jet group, the lower molars were moved forward 1.2 mm and the lower incisors moved forward 2.7 mm while in the Frog group they translated 0.7 mm and 1.0 mm, respectively. This difference could be explained by a difference in treatment technique, dissimilar appliances used in the two practices, or the 62 amount of pretreatment crowding. The increased mesial movement of the lower incisor in the Distal Jet group would explain the favorable change in overjet because the postdistalization position of the lower incisor would assist with the Class II correction to a greater degree. The change in overjet was found to be statistically significant. Anchorage loss was examined at the level of the upper incisor. The Distal Jet group exhibited 2.9 mm of upper incisor movement and 8.6º of flaring. There was 2.2 mm of incisor translation and 6.7º of tipping displayed in the Frog patients. These differences were not considered statistically significant. Anchorage loss in the form of mesial movement of the upper premolars was not considered in the present study. The total treatment time and the rate of distalization were statistically significant when the two groups were compared. Patients were in treatment for 27.4 months in the Distal Jet group and 33.8 months in the Frog group. The differences in treatment time could be explained because of varied treatment philosophies and mechanics of the two practitioners. The rate of distalizer therapy was 0.5 mm/month in the Distal Jet group and 0.4 mm/month in 63 the Frog group. This difference was found to be statistically significant. When comparing the effects of the Distal Jet appliance found in the present study with published studies on the Distal Jet, previous studies have demonstrated 2.1-3.4 mm of molar distalization (Table 3.4).6,8,10,15,16 The present study found a similar but slightly greater amount of molar distalization (3.6 mm). In previous studies, the degree of distal molar tipping ranges from 1.8-5º.6,8,10,15,16 In this investigation, 4.7º of distal molar tipping was found. This value is on the high side of the range seen in other studies which would be expected given the greater amount of molar distalization. The amount of upper incisor movement and degree of tipping reported in other studies varies considerably. Some studies found a very small, insignificant amount of incisor movement11,16 while others reported incisor anchorage loss values greater than what was found in the current investigation.6,10,15 The results of the various studies are not directly comparable as the upper incisors were variably bonded or unbonded during distalization therapy. Edgewise appliances can affect the amount of incisor movement making the anchorage loss not completely attributable to the distalization appliance. The present study used patients that had orthodontic 64 65 Table 3.4: literature Comparison of Distal Jet appliance effects reported in the brackets placed before distalization which would be expected to affect the amount of incisor movement. Time required for distalization, ranged from 5-10 months in previous studies.6,8,10,15,16 In the present study, the Distal Jet therapy took 7.3 months on average, a value that is comparable to published reports. The rate of distal movement in this study was 0.5 mm/month, a value that is greater than that found in Chiu, et al.10 but less than that found in Bolla, et al.11 The position of maxillary second molars and their effect on molar distalization and anchorage loss was evaluated in this study (Table 3.3). Other studies have presented conflicting results regarding the effect of second molars during distalizer therapy. Some studies have indicated that there is no effect on molar distalization or anchorage loss when second molars are erupted or unerupted.17,18,19 Other studies report that distalization is more effective before the second molars are erupted.20 Bolla, et al., indicate that when second molars are partially or completely erupted there is less molar tipping and loss of anchorage during molar distalization but there is no significant difference in the amount of molar distalization.9,11 In the present study, the amount and 66 degree of molar tipping, the amount of incisor movement, the total treatment time, and the rate of distalization were compared when second molars were above the level of the CEJ (unerupted) and below the level of the CEJ (partially or completely erupted). The only statistically significant difference was found in the amount of horizontal movement of the upper incisor (i.e., anchorage loss). In the group with unerupted second molars, the incisors exhibited 2.4 mm of incisor translation while in the group with partially or completely erupted second molars, the incisors moved 3.2 mm. A possible explanation for the greater amount of anchorage loss exhibited when second molars are erupted is because two teeth instead of one are being distalized, the reciprocal force on the incisors is greater resulting in greater mesial movement. Conclusions The results of the present study indicate: 1. The Bowman modified Distal Jet produces significantly more maxillary molar distalization when compared to the original design. 2. The Distal Jet produces greater distal maxillary molar movement in a shorter period of time. 67 3. Undesirable side effects (distal molar tipping and anchorage loss) are observable with both distalizer therapies. 4. More anchorage loss is observed in patients with erupted second molars. 5. The Distal Jet appliance and the Frog are effective therapies in the correction of Class II malocclusions although the Distal Jet may be slightly more efficient. 68 References 1. Proffit WR, Fields, HW, Moray, LJ. Prevalence of malocclusion and orthodontic treatment need in the United States: Estimates from the NHANES III survey. Int J Adult Orthodon Orthognath Surg. 1998;13:97-106. 2. Proffit WR, Fields HW, Sarver DM. Contemporary Orthodontics. 4th ed. St. Louis, MO: Mosby Elsevier, 2007. 3. McSherry PF, Bradley H. Class II correction-reducing patient compliance: a review of the available techniques. J Orthod. 2000;27:219-225. 4. Nanda RS, Kierl MJ. Prediction of cooperation in orthodontic treatment. Am J Orthod Dentofacial Orthop. 1992;102:16-21. 5. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors influencing treatment time in orthodontic patients. Am J Orthod Dentofacial Orthop. 2006;129:230-238. 6. Ngantung V, Nanda RS, Bowman SJ. Posttreatment evaluation of the Distal Jet appliance. Am J Orthod Dentofacial Orthop. 2001;120:178-185. 7. Kinzinger GSM, Diedrich PR. Biomechanics of a Distal Jet appliance. Theoretical considerations and in vitro analysis of force systems. Angle Orthod. 2008;78:676681. 8. Nishii Y, Katada H, Yamaguchi H. Three-dimensional evaluation of the Distal Jet appliance. World J Orthod. 2002;3:321-327. 9. Bolla E, Doldo T, Giorgetti R. Distal movement of maxillary canines and premolars with sectional mechanics following Distal Jet application to molars. Prog Orthod. 2004;5:72-89. 10. Chiu PP, McNamara JA, Franchi L. A comparison of two intraoral molar distalization appliances: Distal Jet versus Pendulum. Am J Orthod Dentofacial Orthop. 2005;128:353-365. 69 11. Bolla E, Muratore F, Carano A, Bowman SJ. Evaluation of maxillary molar distalization with the Distal Jet: a comparison with other contemporary methods. Angle Orthod. 2002;72:481-494. 12. Kinzinger GSM, Eren M, Diedrich PR. Treatment effects of intraoral appliances with conventional anchorage designs for non-compliance maxillary molar distalization: a literature review. Eur J Orthod. 2008;30:558-571. 13. Walde KC. The simplified molar distalizer. J Clin Orthod. 2003;37:616-619. 14. Johnston LE. Balancing the books on orthodontic treatment: an integrated analysis of change. Br J Orthod. 1996;23:93-102. 15. Gutierrez VME. Treatment effects of the distal jet appliance with and without edgewise therapy [unpublished thesis]. Saint Louis: Saint Louis Univerisity; 2001. 16. Ferguson DJ, Carano A, Bowman SJ, et al. A comparison of two maxillary molar distalizing appliances with the distal jet. World J Orthod. 2005;6:382-390. 17. Ghosh J, Nanda RS. Evaluation of an intraoral maxillary molar distalization technique. Am J Orthod Dentofacial Orthop. 1996;110:639-646. 18. Jones RD, White JM. Rapid Class II molar correction with an open-coil jig. J Clin Orthod. 1992;26:661-664. 19. Byloff FK, Darendeliler MA, Clar E, Darendeliler A. Distal molar movement using the Pendulum appliance. Part 2: The effects of maxillary molar root uprighting bends. Angle Orthod. 1997;67:261-270. 20. Hilgers JJ. The Pendulum appliance for Class II noncompliance therapy. J Clin Orthod. 1992;26:706-714. 70 Appendix Table A.1: Description of cephalomeric variables used in the pitchfork analysis. Values are given signs relative to their impact on Class II correction: positive if they would assist in the correction (i.e., forward displacement of the mandible or mandibular dentition) and negative if they would hinder correction (i.e., forward displacement of the maxilla or maxillary dentition). Measurements are made parallel to the mean functional occlusal plane (MFOP) 71 Table A.2: Sample characteristics of Distal Jet group according to appliance design Table A.3: Comparison of original tube and piston Distal Jet and Bowman modified Distal Jet * signifies significance at p > 0.05 **signifies significance at p < 0.01 72 VITA AUCTORIS Larrissa Cali was born on October 20, 1978 in Cleveland, Ohio. She attended The Ohio State University in Columbus, Ohio for her undergraduate studies and received a Bachelor of Science in Agriculture. She relocated to Cleveland and was married to Lucas Cali in May 2004. She attended Case Western Reserve University where she earned her DMD degree in 2008. Following graduation from dental school, she began the orthodontic residency program at Saint Louis University in pursuit of a Masters Degree in Dentistry. Upon graduation, she will move to Texas to begin her orthodontic career. 73