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A STUDY ON THE POSITIONS OF THE MAXILLARY INCISORS IN ANTERIOR OPEN BITE CASES Daniel J. Floyd, 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 2015 COMMITTEE IN CHARGE OF CANDIDACY: Professor Eustaquio A. Araujo, Chairperson and Advisor Professor Rolf G. Behrents Assistant Clinical Professor Hiroshi Ueno i Dedication This work is dedicated to my family. Thank you for your unending love and support as I pursue my dreams. ii Acknowledgements This project was completed with the help of the following important individuals: Dr. Eustaquio Araujo. Thank you for all of your ideas and encouragement with this project and for sharing your seemingly unending wealth of knowledge in the classroom and in clinic. You have been the biggest influence on me as a clinician and your lessons will never be forgotten. Dr. Rolf Behrents. Thank you for all of your help with this project and for this opportunity to pursue my dreams in orthodontics. Dr. Hiroshi Ueno. Thank you for all of your extra time spent on attention to details and ensuring that residents get the most out of our experience at Saint Louis University. Your caring nature is ever abounding with each interaction I have with you. iii Table of Contents List of Tables........................................... vi List of Figures......................................... vii Chapter 1: Introduction................................... 1 Chapter 2: Review of the Literature....................... 4 The Anterior Open Bite .................................. 4 Skeletal Open Bite Characteristics and Contributing Factors ................................................. 6 Dental Open Bite Characteristics and Contributing Factors 9 Combination Skeletal and Dental Open Bite .............. 12 Open Bite Treatments ................................... 13 Potential Problems with Open Bite Treatments ........... 18 Vertical and Angular Change Effects of Maxillary Incisors ............................................. 20 Horizontal Change Effects of Maxillary Incisors ...... 22 Statement of Thesis .................................... 23 List of References ..................................... 24 Chapter 3: Journal Article............................... 30 Abstract ............................................... 30 Introduction ........................................... 32 Materials and Methods .................................. 35 Sample ............................................... 35 Methodology .......................................... 36 Measurements ......................................... 42 Statistical Analysis ................................. 43 Reliability .......................................... 44 Results ................................................ 45 Pre-treatment Measurements ........................... 45 Treatment Changes .................................... 47 Discussion ............................................. 50 Conclusions ............................................ 60 Appendix................................................. 61 iv List of References ..................................... 64 Vita Auctoris............................................ 66 v List of Tables Table 3.1: Descriptive pre-treatment data................ Table 3.2: Treatment changes non-extraction group........ Table 3.3: Treatment changes extraction group............ Table 3.4: Treatment change between non-extraction and extraction groups ..................................... Table A.1: Landmarks and definitions..................... Table A.2: Planes and definitions........................ vi 46 47 48 49 61 62 List of Figures Figure Figure Figure Figure Figure 3.1: 3.2: 3.3: A.1: A.2: Landmark location............................ Reference planes............................. Functional occlusal plane.................... Drawbridge effect illustration............... Drawbridge effect............................ vii 37 39 41 63 63 Chapter 1: Introduction Beginning with Norman Kingsley, the “father of orthodontics,”1 in the 19th century, anterior open bites have proven to be one of the most difficult malocclusions to treat and retain.2,3 There are many reasons for this and many factors that need to be kept in mind when attempting to tackle the difficult task of correcting an open bite. Much of the difficulty lies in the fact that the etiology is often multi-factorial and the relationships of the teeth, soft tissues, and skeletal structures are all important when diagnosing, treating, and maintaining correction of an open bite malocclusion.4 Open bites can be of either dental or skeletal origin, or often a combination of both, with the latter being the most frequent. Since most open bites exhibit both dental and skeletal characteristics, it can often be difficult to make an etiologic distinction and develop an appropriate treatment plan. Disproportionate soft tissues such as a large tongue or a short upper lip can exacerbate an existing dental or skeletal problem. Due to the wide range of influences, one single, universally appropriate way to treat an open bite does not exist. Open bites can either be treated by orthodontics alone, often with a compromised, 1 camouflaged outcome or they can be treated with a combination of orthodontics and surgery.5 While a combination of surgical and orthodontic treatment may yield the best esthetic and functional treatment result, this may not be feasible or desired by many patients and the orthodontic camouflage route may be the only option to provide them with an acceptable result. Due to the difficulty of treating this malocclusion, a wide variety of non-surgical treatment modalities have been developed and utilized to treat open bites. One of the most commonly employed methods is the use of dental extractions. Even though extracting teeth is a common method of open bite treatment, a widely held view by many orthodontists is that the closure of the extraction space always causes much more extrusion of the anterior teeth than non-extraction treatment. If this occurs in the patient where pre-treatment esthetics don’t dictate the need for anterior teeth extrusion, this side effect can have deleterious effects on the post-treatment esthetics involving the teeth and the surrounding soft tissues. The purpose of this study is to evaluate the vertical and horizontal position of maxillary incisors comparing 2 non-extraction and extraction of maxillary first premolar orthodontic treatments in anterior open bite patients. 3 Chapter 2: Review of the Literature The Anterior Open Bite Anterior dental open bite can be defined as a malocclusion having no vertical overlap or contact of the anterior teeth when the posterior teeth are in occlusion.8 The correction of this type of deviation has been regarded as a challenge to the specialty as stated by Cangialosi: “the cases which have proved most difficult to treat and which have the least favorable prognosis are frequently those in which there is a vertical discrepancy that is manifested anteriorly either as a deep overbite or as an open bite.”9 The author went on to say that “the phenomenon of anterior open bite is multifactorial, and there is an almost infinite variety to the dentoskeletal configuration and the magnitude of dysplasia associated with it.”9 This multi-factorial nature of open bites, therefore, makes them one of the most difficult malocclusions to treat and retain.4,10 A few of the possible causes of open bites are genetics, patient habits, influences of the facial soft tissues, and trauma. Studies show the prevalence of anterior open bites is between 1.5 to 11% depending upon 4 ethnic groups.5,11 The relatively high number of individuals who possess this malocclusion and the broad spectrum of contributing factors, make for a common problem with a wide range of issues that one needs to be aware of and continually monitoring throughout the course of treatment. The presence of an anterior open bite presents many problems for both patients and orthodontists. For patients such problems involve speech, swallowing and mastication. For the orthodontist tasked with the difficult challenge of correcting this malocclusion, a short list of problems includes: difficulty with diagnosis due to multi-factorial causation, issues with obtaining proper esthetics, and predictably being able to ensure long term retention of the malocclusion correction.2,4,10,12 Open bites have been classified as skeletal, dental or a combination of both.5,9,13-19 By definition, a skeletal abnormality does not contribute to the dental open bite. However, a skeletal open bite, has some contributions made by vertical facial form which cause the anterior teeth to be positioned in relation to each other in such a way where there is no vertical overlap between them.14 More often than not though, there is a combination of skeletal and dental contributions to the resultant open bite.17 5 Skeletal Open Bite Characteristics and Contributing Factors The distinct characteristics of open bites of skeletal origin are commonly determined by evaluating cephalograms.4,18,20 Individuals with a skeletal open bite show large gonial and cranial base angles and the mandibular ramus is short with an accentuated antegonial notch on its lower border. Posterior facial height is significantly smaller than anterior facial height, up to half the size. The excessive height of the upper anterior face from cranial base to molars and the short posterior facial height give rise to the downward and backward rotation of the mandible. Lower anterior facial height exceeds the upper anterior facial height and the opposite is true in the posterior face. The mandibular plane angle is larger than normal and is often classified as “hyperdivergent,” such that the angle between the cranial base and the mandibular plane (SN-MP) is larger than normal. In the growing patient, there is often a vertical growth pattern with the cranial base and mandibular plane angle becoming more obtuse.4,18,21 It is important to note, that a long face skeletal pattern alone does not in and of itself determine the depth of a dental bite.22 6 The contributing dental effects of the open bite will soon be discussed. In part, due to the vertically directed growth, open bite individuals have a mandibular symphysis that is small anteroposteriorly and large vertically. Subsequently, when looking at the profile view of the individual, a small chin is often evident,21 and commonly, the mandible as a whole is retrognathic.2 Examining the other three dimensional views of the individual, the cranium is dolichocephalic and the frontal face is leptoprosopic. Theories of skeletal shape and form suggest that the musculature plays a primary role in the architecture of the skeletal components of the cranium.23 Therefore, it is of no surprise that individuals with open bites have similarities in the size and span of musculature and its underlying skeleton. Often in open bite individuals, the temporal fossa and the temporalis muscle are small which suggests the individual has weak musculature.11 In open bite individuals, this weak and posteriorly positioned musculature, especially the masseters, allows hyperdivergence and tendency towards vertically directed growth to develop.2,21 In contrast, deep bite patients, who often have large, strong musculature, demonstrate 7 large temporal fossa and large, wide spanning temporalis muscles.21 Individuals with skeletal open bites have similarities involving the soft tissues as well. Despite the orifice of the mouth frequently being wide and broad, vertically short lips have difficulty closing at rest and mouth breathing is subsequently very common. As previously mentioned, the skeleton of the chin is commonly long, narrow, and retrognathic. Correspondingly, lip incompetence from the short lips causes strain of the mentalis muscle when the lips are forcibly closed together and this further lends the individual to the appearance of a lack of chin.15,17,21,24 Examination of the dentition shows frequent impaction of the 3rd molars and teeth tend to be proportionally larger than normal with crowding and bi-maxillary protrusion commonly being present. The incisors form an acute interincisal angle and even though the incisors are often more extruded in individuals with open bites, the extrusion is not enough to allow for contact between the maxillary and mandibular incisors.21 Ultimately, the cause of the skeletal open bite can be determined by viewing the position of the molars. Over eruption of the molars occurs as the palatal plane tips 8 down in the posterior and up anteriorly.11 This posterior tipping of the palatal plane therefore causes the bite to open in the anterior. The tipping of the maxillary occlusal plane then generates a backward and downward rotation of the mandible. This subsequent divergence of the occlusal planes causes a large palatomandibular plane angle and an increase in anterior facial height.21 Therefore, skeletal open bite is a consequence of the tipping of the palatal plane through over eruption of maxillary posterior teeth and the maxillary sutures moving inferiorly.2,25 Although the dentition plays a role in the clinical presentation of the open bite, it is secondary to the abnormal skeletal morphology that is to blame for the relationship of the anterior dentition. Dental Open Bite Characteristics and Contributing Factors The true dental open bite with no contribution from an abnormal skeleton has a much smaller list of characteristics and contributing factors. Dental open bite is associated with the following characteristics: normal craniofacial pattern, proclined incisors, undererupted anterior teeth, normal or only slightly excessive molar height, and little to no gingival display.11,20 9 Open bites of dental origin can be due to trauma, oral habits, influences of the oral and facial soft tissues, and eruption and relationship of the dentition.5,14,18 cause of dental open bite is digit sucking. A common Incidence of digit sucking is 30% at one year of age, 12% at 9 years, and 2% by 12 years of age. Females are more likely than males to be persistent digit suckers. The influence of the digit sucking on the dentition and the surrounding tissues is determined by the age until which this habit persists and the frequency and intensity of the habit. If cessation of the habit occurs before or during growth, the remaining growth of the individual will likely transition back to its underlying, normal pattern.4,14,18 Worms et al.,26 found 80% spontaneous correction of simple open bites, those with no overlap from canine to canine, in individuals ranging from ages 7 to 12. If this cessation does not occur before growth is complete, the clinical presentation will be a persistent anterior open bite and a high, narrow palate and maxillary arch. Along with the lack of vertical overlap of the anterior teeth, the habit can cause an asymmetrical canting of the occlusal plane and a counter clockwise rotation of the palatal skeleton.14 Abnormal tongue function is thought to be another habit where oral soft tissues have direct effects on the 10 creation and maintenance of an open bite. A common abnormal tongue function that can cause or perpetuate an anterior open bite is the tongue thrust or forward resting position habit.4,5,14 Proffit8 has suggested that the open bite is not created through the transient thrusting of the tongue, but rather the open bite is caused by the tongue’s forward resting position between and against the anterior teeth. Cangialosi raised the same question of whether the abnormal tongue function caused the open bite or whether the reverse is true.9 The absolute answer to the question, however, is unknown. Open bite associated with abnormal tongue function is an example of a dental open bite of either primary or secondary origin. Primary open bite is due to excessive contraction of circumoral musculature during swallowing. With primary open bite, the anterior occlusion begins closed, but the action of the musculature on the dentition causes the bite to open. In comparison, the secondary cause of an open bite, perpetuates an open bite that already exists as the tongue frequently rests in between the maxillary and mandibular incisors and positions itself between the incisors in order to create an oral seal during swallowing.14 For both individuals with digit sucking 11 habits and abnormal tongue function, six hours or more per day is required to cause a resultant malocclusion.8,14 Anterior open bite might also be the result of excessive axial inclination of the anterior teeth.19,27 The idea of the “drawbridge effect” has been used to describe an anterior open bite created by excessive proclination of the maxillary and mandibular incisors. The more these incisors are proclined, the larger the amount of open bite that results. As they are retroclined, as in the closing of the two halves of a drawbridge, the smaller the open bite becomes until it eventually closes and positive overbite occurs.5,11,28 Combination Skeletal and Dental Open Bite The third and most prevalent source of an open bite is the combination skeletal and dental open bite. It is a secondary dental open bite with skeletal contributions. Due to the short ramus and the high, narrow positioning of the palatal vault, the airway space is more constricted. As a result, these individuals tend to position their tongues forward in order to breathe. Making matters worse, if an individual also has enlarged tonsils, the tongue will rest and act in an even more anterior position, thus 12 causing the secondary bimaxillary protrusive presentation and acting to reinforce the dental open bite, ensuring it remains and becomes even more severe.21 Open Bite Treatments Treatment of an anterior open bite depends on the cause of the malocclusion, age and the expectations of the patient. Since open bites either have a dental or skeletal etiology, there must be treatment methods that are unique to addressing the malocclusion of each origin. An interesting recommendation to keep in mind is the idea that 90% of patients with true skeletal anterior open bite are best treated with a combination of orthognathic surgical and orthodontic procedures.2,25 This occurs generally because skeletal open bites only become more severe as a patient grows, often regardless of any attempts at growth modulation. Whereas, open bites of purely dental origin, if addressed early enough in a growing patient, may spontaneously close. When they don’t fully close, they are mild enough that generally only orthodontic treatment is necessary.4,14 There are four common treatment modalities for the correction of open bites: observation and myofunctional 13 therapy intervention of early problems, interceptive treatment, orthodontics alone, or a combination of orthodontics and surgery.5,11,14,18 The observation and intervention of early problems modality involves discussing and working through habit modification and cessation with patients. A more active approach to treatment in the use of appliances is interceptive treatment which involves growth regulation and modulation.4,14 Both methods along with the orthodontic and surgery methods will be discussed in greater detail. Abnormal tongue function and non-nutritive sucking are examples of open bite contributing factors seen in young patients where early intervention could allow for growth modification and correction of at least part of the open bite malocclusion. Abnormal tongue function, also referred to as a tongue thrust, are treated with myofunctional training therapy often in combination with appliances such as tongue cribs and rakes. Non-nutritive sucking can also be treated with orthodontic appliances, but extraoral procedures such as chemical aversion and hand wraps are also often used. It is important to be mindful that patients may have a psychological dependence on the sucking habit, so addressing the habit as early as possible is most effective.4,5,8 14 Interceptive treatment takes aim at an early intervention in the growth of the jaws. Intervening before the pubertal growth spurt can be important in preventing future, more complicated procedures in order to correct the malocclusion. At this stage, treatment focuses on avoiding over eruption of posterior teeth, controlling and attempting to redirect growth in all three dimensions with intraoral or extraoral forces. A short list of these passive or active appliances are as follows: vertical holding appliance, vertical chin cup, posterior bite blocks, high pull headgear, Frankel IV regulator, spring loaded bite block, and the active vertical corrector. Pressures from the soft tissues, extraoral anchorage, dental eruption blockage, active forces through springs and magnets are all mechanisms that have been utilized with these appliances.4,5,8 Once growth is complete, if the open bite is mild, camouflage treatment with orthodontics alone can be considered. Both functional and esthetic considerations must be made prior to commencing treatment. Of course, closing an open bite so that a patient can speak, swallow and masticate properly are very important, obtaining acceptable esthetics through orthodontic treatment should be a priority as well. 15 When a patient exhibits a lack of esthetic incisor and gingival display, extrusion of anterior teeth is necessary. This is often done with vertical elastics in the anterior region.14,16 However, when a patient exhibits normal or excessive gingival display, treatment that would prevent or minimize an increase in the incisor and gingival display must be rendered.29 This is best done through extraction or intrusion of posterior teeth.30 Both will be discussed later in greater detail. There are a variety of ways to treat an anterior open bite with orthodontics. Perhaps the most common involves the extraction of posterior teeth.5 Extractions are justified in treating anterior open bites due to two possible mechanisms. The first is the theory that mesial movement of the teeth posterior to the extractions will decrease the “wedge effect” and reduce the mandibular plane angle as the mandible rotates forward.31 However, whether this occurs or not is still quite controversial.32,33 The second mechanism is when premolars are extracted, the previously mentioned “drawbridge effect” occurs.5,11,28 The closure of this space involves the retraction of and the resultant relative extrusion of the maxillary incisors which can cause the closure of the bite.3,14 16 Sarver and Weissman3 have suggested that if this does in fact occur, there are certain selection criteria for open bite patients that must be kept in mind prior to initiating treatment. First, the patient should have proclined maxillary incisors and minimal to no gingival display. Second, the skeletal pattern of the face should not be leptoprosopic, as extraction of mandibular teeth to resolve mandibular incisor proclination could result in mandibular molar extrusion during space closure and this could further increase the mandibular plane angle and cause greater bite opening. Third, the maxillary incisor to lip relationship is important as the retraction and uprighting of the incisor will result in an inferior positioning of the maxillary incisor which could compromise esthetics involving soft tissues.3 More recently, the intrusion of posterior teeth has also been a treatment of choice anchored by bone plates and mini screw implants with elastics or NiTi springs.5 Through a similar mechanism, clear aligner therapy has been advocated for this purpose, though validity is still in question.34 When the patient displays inadequate maxillary incisor and gingiva, the use of vertical elastics with multiloop edgewise archwire (MEAW) technique via the “rocking chair” effect has been utilized attempting to 17 close open bites by extruding the anterior teeth and through very slight intrusion of the posterior teeth. The MEAW technique can also be utilized when minimal extrusion of the maxillary incisors is desired in the case of a patient with normal or excessive incisor and gingival display. This variation, employs a combination of the MEAW and mini screw implants for greater posterior intrusion.16,17 Anterior vertical elastics can be used with straight wires as well, but attention must be paid to minimizing posterior extrusion through mini screw implants or headgear.4,14 If the extrusion of posterior teeth is not prevented, the bite will open further and the anterior teeth will need to be extruded more to close the bite. This could cause inadequate incisor or gingival display.35 Potential Problems with Open Bite Treatments Esthetics is a priority of an orthodontic treatment and must be considered when selecting mechanics and analyzing the consequence of resulting force vectors. Side effects of all treatments need to be studied when deciding which treatment modality to utilize. 18 Negative side effects can occur in three dimensional facial esthetics. One of which involves the amount of incisor and gingival display.2,3,5,7,16,36,37 It has been expected that incisors will be more retroclined when treated with extractions compared to nonextraction treatment.38 When the open bite is due to the excessive proclination of the incisors, the aforementioned “drawbridge effect” is the desired mechanism.5,11,28 However, when this effect occurs in patients with upright or retroclined incisors, such as in Class II, division 2 patients, the result is excessively retroclined incisors. Previous studies have shown, on average, 2-3 mm retraction of the incisors with first premolar extraction treatment.39-41 If pre-treatment esthetics does not warrant it, this posterior movement of the incisor causes retraction of the lips and negative effects on the smile. This could cause the lips to sink back and cause inadequate vermillion display of the upper lip and a more “dished in” profile.3,38,40,42-44 In contrast to extraction treatment, it has been shown that non-extraction treatment results in more proclined incisors.38 Therefore, sufficient attention should be paid to proper diagnosis when deciding between an extraction and a non-extraction treatment plan. 19 Maintenance of adequate incisor angulation throughout treatment avoiding excessive retraction of the incisors can help in obtaining proper soft tissue esthetics. Before setting out to attempt to correct an open bite malocclusion, one must first ensure their diagnosis is comprehensive and correct.9 Then, the selected treatment method must be screened for potential undesirable side effects. Caution should be exercised to not allow palatal cusps of posterior maxillary teeth to hang down, thus opening the bite further.14,18 One must also think about retention prior to initiating treatment to ensure all treatment objectives are achieved to minimize posttreatment relapse. Considering open bites are one of the least stable malocclusions, beginning with the end in mind would be a prudent approach.10,45 Vertical and Angular Change Effects of Maxillary Incisors According to Downs46, the normal interincisal angle should be 135°, while Steiner47 states it should be 131°. Previous studies have shown an increase of 4.5° in the interincisal angle and posterior movement of the incisal edge of the maxillary incisors in extraction treatment.48 This could mean the angulation of the maxillary incisor has 20 decreased which subsequently could cause the incisor to relatively extrude. However, the interincisal angle uses the angulation of the maxillary and mandibular central incisors. According to this study, it is unknown how much of this angular reduction is due to the maxillary or mandibular central incisors individually. Perhaps lending evidence to the contribution of the maxillary central incisor to the interincisal angle reduction is Bishara’s study49 in which maxillary incisors in the four first premolars extraction group compared to the non-extraction group retroclined 2.3° more in males and 4.6° more in females. Related and pertinent, Ramos et al.,42 studied changes to the maxillary central incisors in maxillary first premolar extraction patients and showed the incisor extruded 0.06 mm to 0.65 mm in relation to the lower curvature of the upper lip. Therefore, according to these studies, after extraction and during the retraction of the anterior teeth, the maxillary central incisors decrease in angulation and extrude. It is important to note that no studies have compared the amount of extrusion in patients treated with extractions versus non-extraction. 21 Also, it is unknown how much of the incisor extrusion was via pure extrusion or relative extrusion. Horizontal Change Effects of Maxillary Incisors Evaluating the anteroposterior movement of the maxillary central incisor, three studies showed very similar results. Bishara found the maxillary central incisor retracted 4.6 mm and 1.5 mm in the extraction and non-extraction groups, respectively.49 Although a non- extraction group was not studied, Ramos et al.,42 found comparable retraction ranging between 3.7 and 5.6 mm for patients treated with extractions. Similar, though not as much retraction in the extraction group was found in the Luppanapornlarp study evaluating four first premolar extraction treatment in “borderline” patients. The results showed maxillary central incisor retraction of 2.8 mm in the extraction group and 1.4 mm in the non-extraction group. Luppanapornlarp suggested this retraction then caused 2-3 mm of retraction of the upper lip, thus causing a decrease in the convexity of the patient profile.40 Ramos et al.,42 found that changes in the incisor position and angulation affected the position of the upper lip as well. Another important finding was that changes to the cervical 22 portion of the maxillary central incisor had almost twice as much correlation to changes in the upper lip angle than the changes in the incisal edge. Therefore, retraction of the cervical portion of the incisor affects the lips more than retraction of the incisal edge. Many studies40,42,46,47,49 have shown these changes in the incisor position and angulation have direct effects on the esthetics of the smile. Therefore, when orthodontically treating patients, one must be knowledgeable of the composition of the smile. Taking this a step further, one should be familiar with the esthetic normative values of these components and how certain treatments ultimately influence their post-treatment esthetics.50-76 Statement of Thesis This study aims to evaluate the vertical and horizontal position changes of maxillary incisors when comparing non-extraction and extraction of maxillary first premolar orthodontic treatments in anterior open bite patients. 23 List of References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. Peck S. Dentist, artist, pioneer: orthodontic innovator Norman Kingsley and his Rembrandt portraits. JADA 2012;143(4):393-7. Beane RA, Jr. Nonsurgical management of the anterior open bite: a review of the options. Semin Orthod 1999;5(4): 275-83. Sarver DM, Weissman SM. Nonsurgical treatment of open bite in nongrowing patients. Am J Orthod Dentofacial Orthop 1995;108(6):651-9. Ngan P, Fields HW. Open bite: a review of etiology and management. Pediatr Dent 1997;19(2):91-8. 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Using clear aligner therapy to correct malocclusion with crowding and an open bite. Gen Dent 2012;60(3):218-23. Kuhn RJ. Control of anterior vertical dimension and proper selection of extraoral anchorage. Angle Orthod 1968;38(4):340-9. Kumar SK, Deepika M., Chandrasekaran, TR. Janardhanam, P. Diagnosis and Treatment Planning of Excessive Gingival Display: A Review. J Ind Orthod Soc 2006. Mackley RJ. An evaluation of smiles before and after orthodontic treatment. Angle Orthod 1993;63(3):183-9. Weyrich C, Lisson JA. The effect of premolar extractions on incisor position and soft tissue profile in patients with Class II, Division 1 malocclusion. J Orofac Orthop 2009;70(2):128-38. Saelens NA, De Smit AA. Therapeutic changes in extraction versus non-extraction orthodontic treatment. Eur J Orthod 1998;20(3):225-36. Luppanapornlarp S, Johnston LE, Jr. The effects of premolar-extraction: a long-term comparison of outcomes in "clear-cut" extraction and nonextraction Class II patients. Angle Orthod 1993;63(4):257-72. Ong HB, Woods MG. An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects. Angle Orthod 2001;71(2):90-102. Ramos AL, Sakima MT, Pinto Ados S, Bowman SJ. Upper lip changes correlated to maxillary incisor retraction: a metallic implant study. Angle Orthod 2005;75(4):499-505. Perkins RA, Staley RN. Change in lip vermilion height during orthodontic treatment. Am J Orthod Dentofacial Orthop 1993;103(2):147-54. Drobocky OB, Smith RJ. Changes in facial profile during orthodontic treatment with extraction of four first premolars. Am J Orthod Dentofacial Orthop 1989;95(3):220-30. Huang GJ. Long-term stability of anterior open-bite therapy: A review. Semin Orthod 2002;8(3):162-72. Downs WB. Analysis of the Dentofacial Profile. Angle Orthod 1956;26(4):191-212. 26 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. Steiner CC. Cephalometrics In Clinical Practice. Angle Orthod 1959;29(1):8-29. Kocadereli I. Changes in soft tissue profile after orthodontic treatment with and without extractions. Am J Orthod Dentofacial Orthop 2002;122(1):67-72. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111(1):18-27. Duchenne de Boulogne GB. The Mechanism of Human Facial Expression. 1st ed Cambridge: Cambridge University Press, 1990. Sabri R. The eight components of a balanced smile. J Clin Orthod 2005;39(3):155-67. Kokich VO, Jr., Kiyak HA, Shapiro PA. Comparing the perception of dentists and lay people to altered dental esthetics. J Esthet Dent 1999;11(6):311-24. Jananni M, Sivaramakrishnan M, Libby TJ. Surgical correction of excessive gingival display in class I vertical maxillary excess: Mucosal strip technique. J Nat Sci Biol Med 2014;5(2):494-8. Macari A, Abou Chebel N. Upper lip shortening combined with Lefort 1 maxillary intrusion: a novel approach to correct the long face syndrome. Eur J Plast Surg 2014;37(4):245-50. Peck S, Peck L, Kataja M. Some vertical lineaments of lip position. Am J Orthod Dentofacial Orthop 1992; 101(6):519-24. Sarver DM, Ackerman MB. Dynamic smile visualization and quantification: Part 2. Smile analysis and treatment strategies. Am J Orthod Dentofacial Orthop 2003;124(2):116-27. Rigsbee OH, 3rd, Sperry TP, BeGole EA. The influence of facial animation on smile characteristics. Int J Adult Orthodon Orthognath Surg 1988;3(4):233-9. Robbins JW. Differential diagnosis and treatment of excess gingival display. Prac Periodont Aesthet Dent 1999;11(2):265-72. Geron S, Atalia W. Influence of sex on the perception of oral and smile esthetics with different gingival display and incisal plane inclination. Angle Orthod 2005;75(5):778-84. 27 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. Pithon MM, Santos AM, Campos MS, Couto FS, dos Santos AF, Coqueiro RdS, et al. Perception of laypersons and dental professionals and students as regards the aesthetic impact of gingival plastic surgery. Eur J Orthod 2014;36(2):173-8. Suzuki L, Machado AW, Vieira Bittencourt MA. Perceptions of gingival display aesthetics among orthodontists, maxillofacial surgeons and laypersons. J Dent Sci 2009;24(4):367. Armitage GC. Development of a classification system for periodontal diseases and conditions. Ann Periodontol 1999;4(1):1-6. Proffit WR, White, RP, Jr., Sarver, DM. Contemporary Treatment of Dentofacial Deformity. 1 ed: The CV Mosby Company; 2003. Finnoy JP, Wisth PJ, Boe OE. Changes in soft tissue profile during and after orthodontic treatment. Eur J Orthod 1987;9(1):68-78. Johnson DK, Smith RJ. Smile esthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995;108(2):162-7. Kim E, Gianelly AA. Extraction vs Nonextraction: Arch Widths and Smile Esthetics. Angle Orthod 2003;73(4): 354-8. Meral O, Iscan HN, Okay C, Gursoy Y. Effects of bilateral upper first premolar extraction on the mandible. Eur J Orthod 2004;26(2):223-31. Spahl TJ, Witzig JW. The Clinical Management of Basic Maxillofacial Orthopedic Appliances. PSG Publishing Company;1987. Paquette DE, Beattie Jr, Johnston LE, Jr. A long-term comparison of nonextraction and premolar extraction edgewise therapy in "borderline" Class II patients. Am J Orthod Dentofacial Orthop 1992;102(1):1-14. Lim H-J, Ko K-T, Hwang H-S. Esthetic impact of premolar extraction and nonextraction treatments on Korean borderline patients. Am J Orthod Dentofacial Orthop 2008;133:524-31. Tjan AH, Miller GD, The JG. Some esthetic factors in a smile. J Prost Dent 1984;51(1):24-8. Dong JK, Jin TH, Cho HW, Oh SC. The esthetics of the smile: a review of some recent studies. Int J Prosthod 1999;12(1):9-19. Peck S, Peck L, Kataja M. The gingival smile line. Angle Orthod 1992;62(2):91-100. 28 74. 75. 76. Paula DFJ, Silva, ET, Campos, AC, Nunez MOL, CR. Effect of anterior teeth display during smiling on the self-perceived impacts of malocclusion in adolescents. Angle Orthod 2011;81(3):540-5. Silva CO RJN, Campos TVS, Rodrigues JG, Tatakis DN. Excessive gingival display: treatment by a modified lip repositioning technique. J Clin Periodontol. 2012;40(3): 260-5. Mack MR. Vertical dimension: a dynamic concept based on facial form and oropharyngeal function. J Prosthet Dent 1991;66(4):478-85. 29 Chapter 3: Journal Article Abstract Purpose: The purpose of this study is to evaluate the vertical and horizontal position of maxillary incisors when comparing non-extraction and extraction of maxillary first premolar orthodontic treatments in anterior open bite patients. Materials and Methods: The sample of 60 subjects was selected from the records at Saint Louis University Center for Advanced Dental Education. The cases were selected on the basis of the following inclusion criteria: 1) Class I or Class II, division 1, 2) anterior open bite from canine to canine, 3) canines shouldn’t be in occlusion but an end to end relationship was acceptable, 4) all permanent incisors had to be present and fully erupted, 5) high quality pre- and post-treatment cephalograms. Group 1 had no extractions of permanent teeth during treatment and group 2 had extractions of at least maxillary first premolars. Temporary anchorage devices could have been used for anterior and posterior movement of teeth, but not for intrusion mechanics. used. No extraoral appliances were Patients with a syndrome, a congenital deformity like cleft lip and palate or missing one or more incisors were excluded from the study. Results: Both groups experienced statistically significant changes in the 30 position of the maxillary central incisors in the horizontal and vertical directions. However, the mean change of the position of Prosthion in the horizontal and vertical directions was not statistically significant between the two groups. In the non-extraction group, the maxillary central incisor extruded 2.97 mm and retracted 0.56mm. In the extraction group, the maxillary central incisor extruded 3.52 mm and retracted 2.19 mm. Conclusions: The results of this study show that maxillary central incisors are extruded similar amounts in extraction and non-extraction treatment of anterior open bite. However, the changes in the horizontal position of the extraction group were significant and greater than the nonextraction group. 31 Introduction Beginning with Norman Kingsley, the “father of orthodontics,”1 in the 19th century, anterior open bites have proven to be one of the most difficult malocclusions to treat and retain.2,3 There are many reasons for this and many factors that need to be kept in mind when attempting to tackle the difficult task of correcting an open bite. Much of the difficulty lies in the fact that the etiology is often multi-factorial and the relationships of the teeth, soft tissues, and skeletal structures are all important when diagnosing, treating, and maintaining correction of an open bite malocclusion.4 Open bites can be of either dental or skeletal origin, or often a combination of both, with the latter being the most frequent. Since most open bites exhibit both dental and skeletal characteristics, it can often be difficult to make an etiologic distinction and develop an appropriate treatment plan. Disproportionate soft tissues such as a large tongue or a short upper lip can exacerbate an existing dental or skeletal problem. Due to the wide range of influences, one single, universally appropriate way to treat an open bite does not exist. Open bites can either be treated by orthodontics alone, often with a compromised, 32 camouflaged outcome or they can be treated with a combination of orthodontics and surgery.5 While a combination of surgical and orthodontic treatment may yield the best esthetic and functional treatment result, this may not be feasible or desired by many patients and the orthodontic camouflage route may be the only option to provide them with an acceptable result. Due to the difficulty of treating this malocclusion, a wide variety of non-surgical treatment modalities have been developed and utilized to treat open bites. One of the most commonly employed methods is the use of dental extractions. Even though extracting teeth is a common method of open bite treatment, a widely held view by many orthodontists is that the closure of the extraction space always causes much more extrusion of the anterior teeth than non-extraction treatment. If this occurs in the patient where pre-treatment esthetics don’t dictate the need for anterior teeth extrusion, this side effect can have deleterious effects on the post-treatment esthetics involving the teeth and the surrounding soft tissues. The purpose of this study is to evaluate the vertical and horizontal position of maxillary incisors comparing 33 non-extraction and extraction of maxillary first premolar orthodontic treatments in anterior open bite patients. 34 Materials and Methods Sample The sample of 60 subjects was selected from the records at Saint Louis University Center for Advanced Dental Education. The cases were selected on the basis of the following inclusion criteria: 1) Class I or Class II, division 1, 2) anterior open bite from canine to canine, 3) canines shouldn’t be in occlusion but an end to end relationship was acceptable, 4) all permanent incisors had to be present and fully erupted, 5) high quality pre- and post-treatment cephalograms. Group 1 had no extractions of permanent teeth during treatment and group 2 had extractions of at least maxillary first premolars. Temporary anchorage devices could have been used for anterior and posterior movement of teeth, but not for intrusion mechanics. No extra-oral appliances were used. Patients with a syndrome, a congenital deformity like cleft lip and palate or missing one or more incisors were excluded from the study. 35 Methodology All cephalograms were taken on the same cephalometer within Dolphin Imaging Software (Dolphin Imaging Software, Inc., Dolphin Imaging, Version 11.5, Chatsworth, California). Following collection of each of the patient records, all pre- and post-treatment cephalograms were digitized using Dolphin Imaging software. Nine hard and soft tissue landmarks were located: S (Sella), N (Nasion), ANS (Anterior Nasal Spine), PNS (Posterior Nasal Spine), U1a (maxillary central incisor apex), U1i (maxillary central incisor incisal edge), PR (Prosthion), L1i (mandibular central incisor incisal edge), SS (Stomion Superiorus). A diagram of landmark location can be seen in Figure 3.1 and their definitions are located in Appendix Table A.1. The digitized cephalograms were then printed at a 1:1 ratio to ensure no change in magnification. 36 Figure 3.1: Landmark location 37 An X-Y coordinate grid was constructed on the cephalograms. The most superior X-axis was represented by a horizontal constructed line, which was created by subtracting 7° from the Sella to Nasion line (SN-7°). The Y-axis was represented by a vertical line perpendicular to SN-7° from Sella. The B plane X-axis was represented by a horizontal line perpendicular to the Y-axis through Stomion Superiorus (SS). The C plane X-axis was represented by a horizontal line perpendicular to the Y-axis through the incisal edge of the maxillary central incisor (U1i). reference planes are depicted in Figure 3.2 and their definitions are located in Appendix Table A.2. 38 These Figure 3.2: Reference planes 39 The amount of open bite was obtained using the functional occlusal plane (FOP) as the reference. The FOP was represented by the line bisecting the maxillary and mandibular first molars and premolars, not taking into account the position of the incisors.8 The measurement of a line drawn perpendicular from the FOP to the incisal edge the maxillary and mandibular incisors was recorded. The sum of these distances was the amount of pre-treatment open bite (OB). The sum of this distance minus the post- treatment positive overbite was the amount of open bite closure that occurred. The FOP plane is shown below in Figure 3.3. 40 Figure 3.3: Functional occlusal plane8 41 Measurements The following manual measurements were taken using a digital caliper and compared using multiple two sample ttests and paired t-tests: Millimetric linear measurements - A plane to B plane - B plane to C plane - U1a to SN minus 7°: The maxillary central incisor root apex to S-N line minus 7°. - U1i to SN minus 7°: The incisal edge of the maxillary central incisor to S-N line minus 7°. - PR to SN minus 7°: The most anterior point on the maxillary alveolar process in the midline to S-N line minus 7°. - PR to Y-axis: The most anterior point on the maxillary alveolar process in the midline to Y-axis. - U1a to Y-axis: The maxillary central incisor apex to Y-axis. - U1i to Y-axis: The incisal edge of the maxillary central incisor to Y-axis. - U1i to FOP: The maxillary central incisor incisal edge to the functional occlusal plane. - L1i to FOP: The mandibular central incisor incisal edge to the functional occlusal plane. 42 Angular measurements - SN-MP: Angle between Sella to Nasion line and plane connecting Gonion and Menton. Gonion determined by bisecting the angle formed by tangents to the posterior border of the ramus and inferior border of the mandible. - SN-PP: Angle between Sella to Nasion line and line from anterior nasal spine to posterior nasal spine. - U1-SN: Angle between Sella to Nasion line and line through long axis of the maxillary central incisor. Pre-treatment to post-treatment horizontal and vertical changes were computed by subtracting the pretreatment landmark position from the post-treatment landmark position. Statistical Analysis Descriptive data was obtained for all measurements and statistical analysis was done utilizing the Statistical Package for the Social Science (IBM SPSS, Version 20, Armonk, NY). Independent sample t-tests were used for each variable to detect differences at the start of treatment between the non-extractions and extractions groups. Paired t-tests were used for each variable to detect differences between pre-treatment and post-treatment measurements 43 within the non-extraction or extraction groups. Independent sample t-tests were used for each variable to detect differences in mean changes between the nonextractions and extractions groups. A significance level of p <.05 was set to detect differences for all statistical analyses. Reliability To determine the consistency of measurements, Chronbach’s alpha was used. Intra-class correlations greater than or equal to 0.80 were considered to be reliable. All measurements for 12 randomly selected subjects were re-measured to test of intra-examiner reliability. measurements. Chronbach’s alpha was above 0.80 for all This indicates original and repeated measurements were at an acceptable level of reliability for accuracy of measurements. 44 Results Pre-treatment Measurements Descriptive data was obtained for pre-treatment measurements. Independent sample t-tests were calculated for each of the 14 variables to detect differences at the beginning of treatment between the non-extractions and extractions groups. The results showed statistically significant differences between the non-extraction and extraction groups in the distance from the maxillary central incisor incisal edge and Stomion Superiorus. There was also statistically significant difference in the SN to MP angle. A statistically significant difference was found in the distance from the maxillary central incisor incisal edge to the occlusal plane. Details are shown below in Table 3.1. 45 Table 3.1: Descriptive pre-treatment data Pre-Treatment Measurements non-extractions and extractions Group NonExtractions extractions Variable Mean SD Mean SD Sig. A – B (mm) 69.45 5.53 69.21 5.30 0.866 0.006* B – C (mm) 1.49 1.46 2.68 1.74 U1a to SN-7 (mm) 49.03 4.63 50.50 4.71 0.227 U1i to SN-7 (mm) 70.08 5.76 71.86 5.42 0.223 PR to SN-7 (mm) 59.06 5.33 60.12 4.94 0.428 PR to Y-axis (mm) 68.67 6.82 67.02 8.37 0.407 U1a to Y-axis (mm) 61.31 6.41 59.01 7.17 0.195 U1i to Y-axis (mm) 70.65 7.72 69.08 9.60 0.488 0.015* U1i to FOP (mm) 3.09 1.78 1.90 1.88 L1i to FOP (mm) -0.78 1.57 -0.43 1.58 0.403 OB (mm) 2.31 1.63 1.58 1.43 0.070 0.037* SN - MP° 35.19 6.12 38.25 4.90 U1 - SN° 107.45 9.21 109.82 9.98 0.343 SN - PP° 17.46 4.57 17.74 5.24 0.824 *P<.05 All measurements in millimeters or degrees as indicated 46 Treatment Changes Descriptive data was obtained for the pre- and posttreatment changes for each of the 14 variables. Paired t- tests were calculated for each variable. In the non-extractions group, A-B, B-C, U1a to SN minus 7°, U1i to SN minus 7°, Prosthion to SN minus 7°, U1i to Y-axis, SN-MP°, U1-SN°, U1-FOP, and amount of open bite showed statistically significant changes. The maxillary central incisors were extruded and retracted. The mandibular plane increased slightly and the angulation of the maxillary central incisor decreased. Details are shown below in Table 3.2. Table 3.2: Treatment changes non-extraction group Pre- to Post-Treatment Change Variable Mean SD Sig. change 0.001* A – B (mm) 1.95 3.00 0.014* B – C (mm) 0.83 1.74 U1a to SN-7 (mm) 2.68 2.31 <0.001* U1i to SN-7 (mm) 3.20 3.06 <0.001* PR to SN-7 (mm) 2.97 3.02 <0.001* PR to Y-axis (mm) -0.56 2.74 0.274 U1a to Y-axis (mm) -0.18 3.01 0.741 0.002* U1i to Y-axis (mm) -1.63 2.63 U1i to FOP (mm) 2.69 2.12 <0.001* L1i to FOP (mm) 0.51 1.55 0.084 OB (mm) -3.19 1.61 <0.001* 0.006* SN - MP° 1.22 2.24 0.002* U1 - SN° -4.48 7.09 SN - PP° 0.76 3.96 0.302 *P<.05 All measurements in millimeters or degrees as indicated 47 In the extractions group, A-B, U1a to SN minus 7°, U1i to SN minus 7°, Prosthion to SN minus 7°, Prosthion to Yaxis, U1i to Y-axis, U1-SN°, SN-PP°, U1-FOP, and amount of open bite showed statistically significant changes. The maxillary central incisor vertically were extruded and retracted. The palatal plane increased slightly and the angulation of the maxillary central incisor decreased. Details are shown below in Table 3.3. Table 3.3: Treatment changes extraction group Pre- to Post-Treatment Change Variable Mean SD Sig. change 0.001* A – B (mm) 2.53 3.72 B – C (mm) 0.50 1.77 0.135 U1a to SN-7 (mm) 2.95 3.63 <0.001* U1i to SN-7 (mm) 3.13 3.31 <0.001* PR to SN-7 (mm) 3.52 3.47 <0.001* 0.003* PR to Y-axis (mm) -2.19 3.77 U1a to Y-axis (mm) -0.10 2.49 0.827 U1i to Y-axis (mm) -4.47 5.57 <0.001* U1i to FOP (mm) 2.36 2.24 <0.001* L1i to FOP (mm) 0.41 1.69 0.190 OB (mm) -2.96 1.41 <0.001* SN - MP° 0.43 3.00 0.439 U1 - SN° -11.53 11.16 <0.001* 0.010* SN - PP° 2.42 4.81 *P<.05 All measurements in millimeters or degrees as indicated 48 Independent sample t-tests were calculated for each of the 12 variables to detect differences in mean changes between the non-extractions and extractions groups. The results showed a significant reduction in the distance between the maxillary incisor incisal edge to the Y-axis and a reduction in the angle between the SN line and the long axis of the maxillary central incisor. Details are shown below in Table 3.4. Table 3.4: Treatment change between non-extraction and extraction groups Pre- to Post-Treatment Change Group NonExtractions extractions Variable Mean SD Mean SD Sig. change change A – B (mm) 1.95 3.00 2.53 3.72 0.511 B – C (mm) 0.83 1.74 0.50 1.77 0.464 U1a to SN-7 (mm) 2.68 2.31 2.95 3.63 0.736 U1i to SN-7 (mm) 3.20 3.06 3.13 3.31 0.932 PR to SN-7 (mm) 2.97 3.02 3.52 3.47 0.510 PR to Y-axis (mm) -0.56 2.74 -2.19 3.77 0.060 U1a to Y-axis (mm) -0.18 3.01 -0.10 2.49 0.907 0.014* U1i to Y-axis (mm) -1.63 2.63 -4.47 5.57 OB (mm) -3.19 1.61 -2.96 1.41 0.546 SN - MP° 1.22 2.24 0.43 3.00 0.255 0.005* U1 - SN° -4.48 7.09 -11.53 11.16 SN - PP° 0.76 3.96 2.42 4.81 0.149 *P<.05 All measurements in millimeters or degrees as indicated 49 Discussion The purpose of this study was to attempt to bring to light additional evidence for or against the commonly held axioms that extraction orthodontic treatment negatively effects post-treatment esthetics. This study sought to add another layer to the evidence base involving orthodontic treatment and facial esthetics by attempting to correlate the effects premolar extraction treatment has on post-treatment gingival display by looking at the horizontal and vertical changes of the maxillary incisors.3,6 Empirical, though not completely unequivocal, conclusions could perhaps be inferred from this study regarding the amount of post-treatment gingival display in patients with anterior open bites. These conclusions could be used to guide orthodontic practitioner’s decisions in treating these patients rather than assumptions based primarily in theory and observations not substantiated by evidence. The literature reveals little information regarding the effect on intraoral esthetics, specifically in amount of gingival display, between orthodontic treatment completed with extractions of permanent teeth and nonextraction treatment.6,7,9-12 Throughout the orthodontic community, there has been a widespread, accepted belief 50 that extracting maxillary first premolars causes a greater increase in post-treatment gingival display than does orthodontic treatment without extractions. However, no studies have been performed to confirm or disprove this assertion. The present study aimed to provide evidence to whether or not extraction and non-extraction orthodontic treatment causes similar or different changes on the vertical and horizontal position of the maxillary incisors and attempt to correlate it with gingival display. This study looked at 60 orthodontic patients with anterior open bite from canine to canine, with either extraction of maxillary first premolars or non-extraction orthodontic treatment. All patients were either Class I or Class II, division I pretreatment. In comparing pre-treatment measurements, a significant difference was found between the extraction and nonextraction groups in the distance between the inferior curvature of the upper lip, Stomion Superiorus, and the maxillary incisor incisal edge. This distance was 1.49 mm in patients treated without extractions and 2.68 mm in patients treated with extractions. This shows that, in the extraction group, the maxillary central incisors began more inferior to the upper lip than the non-extraction group. 51 Patients treated without extractions show less pretreatment hyperdivergence than patients treated with extractions as their mandibular plane angles were 35.19° and 38.25°, respectively. Both of these findings were found to be statistically significant. There was also a significant difference in the distance of the maxillary incisor incisal edge to the functional occlusal plane between the extraction and non-extraction groups of 1.90 mm and 3.09 mm, respectively. On average, the amount of pre- treatment anterior open bite was 2.31 mm in the nonextraction group and 1.58 mm in the extraction group. This difference, however, was not significant between the two groups. Therefore, in regards to pre-treatment amount of open bite, the groups are similar and accurate conclusions can be drawn from comparison of the groups. Evaluation of the pre- and post-treatment changes between the non-extraction and extraction groups shows there was no significant difference in the amount of open bite closure. The non-extraction group had 3.19 mm and the extraction group had 2.96 mm of open bite closure. Therefore, the amount of open bite closure is nearly identical between both groups at around 3 mm. The data also shows that the open bite was closed primarily due to the extrusion of the maxillary central incisors with 52 relatively little contribution coming from the minimal extrusion of the mandibular central incisors. An important, non-statistically significant finding was that the maxillary central incisors extruded vertically during treatment, regardless of treatment group. The non- extraction group showed 2.97 mm and the extraction group showed 3.52 mm of extrusion when viewing the vertical changes of Prosthion. With no vertical change differences evident, significant differences between the two groups begin to become noticeable when looking at anteroposterior and incisor angulation changes. By way of the anteroposterior change of Prosthion, the maxillary incisors were retracted 2.19 mm in the extraction group and 0.56 mm in the non-extraction group. This was not a statistically significant difference, but a P-value of 0.060 shows there is a near significant change. Although the retraction of Prosthion did not prove to be significant, there was a statistically significant change in the anteroposterior position of the maxillary central incisor incisal edge in both groups. The incisal edge was retracted 4.47 mm in the extraction group and 1.63 mm in the non-extraction group. These findings coincide with those in previous studies.13-17 Comparing this data to the change in the maxillary central incisor apex, 0.18 mm in 53 the non-extraction group and 0.10 mm in the extraction group, open bite closure occurs primarily through tipping around the center of rotation rather than bodily movement through the center of resistance. Due to the greater amount of retraction during space closure, the extraction group demonstrates much more tipping than the nonextraction group. Upon evaluation of the change in the angulation of the maxillary central incisor, the data revealed a statistically significant change in both groups. In the non-extraction group, this angle decreased 4.48° and in the extraction group, the angle decreased 11.53°. Angulation of the maxillary incisors is important for the esthetics of the teeth themselves as well as influencing the esthetics of the surrounding soft tissues. The effects of the incisor position on the vertical position of the upper lip and the gingival soft tissues will be discussed in detail. Observers who believe extraction treatment compared to non-extraction treatment causes an increase in gingival display due to a greater amount of extrusion, as referenced earlier, may be surprised by the findings of this study. Comparing the amount of vertical extrusion between nonextraction and extraction patients reveals no statistical difference. The data shows that in the treatment of open 54 bites, maxillary incisors extrude nearly equal amounts in non-extraction and extraction treatments. Therefore, if one believes the extrusion of maxillary incisors is the most important factor in causing an increase in gingival display, then both groups could cause this increase in nearly equal amounts. However, while the impact of vertical extrusion of the incisors on gingival display could be important, there are other influences to keep in mind as well. The previously mentioned “drawbridge effect”5,18,19 is at work in evaluating the increase in downward and backward tipping and angulation decrease of the maxillary central incisor crowns. This decrease in angulation of the incisors within the extraction group corresponds with the relative extrusion idea mentioned in orthodontic literature and textbooks.2,3,20,21 When the angulation of the maxillary incisors decreases, relative extrusion causes an increase in the display of the gingiva. The incisor crown tips back and even though it is not vertically extruded, it appears to relatively extrude as more of the crown becomes visible.3,21 In the present study a significant extrusion difference between the extraction and non-extraction groups was not evident. Therefore, if proper orthodontic 55 mechanics are employed, the “drawbridge” relative extrusion effect may not occur. This concept demonstrates the dynamic relationship of the teeth to the soft tissues. However, the gingiva is not the only soft tissue directly affected by changes in the position of the maxillary incisors. As the maxillary incisors are extruded and retracted, the lips can also be directly affected. Many studies have proven that changes in the position of the incisors affect the spatial position of the lips. During non-extraction or extraction orthodontic treatment, as the maxillary incisor moves, its interaction with the upper lip will change in the vertical and horizontal directions. This study looked at the vertical changes of the lip in this relationship. An important finding was that the vertical change of the incisor to Stomion Superiorus is different for the nonextraction and the extraction group. There was a statistically significant increase in the distance between the incisal edge and Stomion Superiorus in the nonextraction group of 0.83 mm. If one still believes that only extraction treatment causes a significant amount of extrusion, this change, along with the previously mentioned amount of measured extrusion, confirms the extrusion of the 56 incisors during treatment without extractions. Interestingly, even though this distance in the extraction group also increased 0.50 mm, the change was found to not be statistically significant. The explanation of this finding could involve the retraction of the incisor. When the incisor is retracted in the anteroposterior direction, the upper lip will also be retracted. inferiorly, the lip will follow. As the incisor moves This inferior movement of the upper lip potentially offsets some of the vertical extrusion of the maxillary incisor. Ramos et al.,17 had similar findings involving the vertical changes of the upper lip in extraction cases, showing 0.06 to 0.65 mm greater vertical display of the incisor compared to Stomion Superiorus. The present study showed the upper lip moved inferiorly 1.95 mm in the non-extraction group and 2.53 mm in the extraction group. The vertical movement of the upper lip in this study coincides with that found in previous studies.6,7,9-12,17 This finding is important when one correlates these findings with Sabri’s22 conclusion that the average elevation of the upper lip is 7-8 mm, with a range of 2-12 mm. If one assumes the activity of the musculature remains the same, this inferior movement of Stomion superiorus could help to mask 2/3rds of the effect 57 the vertical extrusion of the maxillary central incisor has on the amount of post-treatment gingival display. Although it does not signify that it causes less gingival display than the non-extraction group, in the extraction group the lip covers more of the incisors and a conclusion could be drawn that this dynamic relationship could at least not cause increased gingival display. Mackley23 demonstrated similar findings as well. An evaluation of pre- and post-treatment photographs compared with a cephalometric analysis of patients showed that this was achieved in the patients with the smallest increase or even decrease in the Stomion Superiorus to maxillary incisor edge distance. He also found that the least amount of gingival display post-treatment was seen in the patients with the greatest U1-SN angulation. Therefore, Mackley’s findings verify the conclusions of this current study. As the SS to U1i distance increases, vertical extrusion increases and as the U1-SN angle decreases, relative extrusion occurs and the net result contributes to an increase in gingival display as more of the crown is visible and the gingiva moves inferiorly. According to the data of this study, changes by hard and soft tissues visible on the cephalograms can shed some light onto how the maxillary gingiva likely responds during 58 treatment. The findings of this study do not support the rationale behind the common assumption that extracting permanent teeth unequivocally causes an increase in maxillary incisor extrusion and gingival display compared to non-extraction treatment due to vertical extrusion of the maxillary incisors alone. However, extraction treatment without proper angulation maintaining orthodontic mechanics control, could cause an increase in gingival display due to the relative extrusion during retraction.3,21 Due to the limitations of this study, however, absolute conclusions regarding gingival display cannot be drawn. Two dimensional cephalometric radiographs do not affirm absolute conclusions related to amount of gingival display change. Further study is necessary to attempt to glean more absolute conclusions. 59 Conclusions Given the results of this study, the following conclusions can be made: 1. Maxillary incisors in both the extraction and nonextraction groups moved vertically similar amounts. 2. Amount of open bite closure was similar in both groups. 3. Greater tipping and retraction in the horizontal direction and greater decrease in maxillary incisor angulation occurred in the extraction group. 4. The maxillary incisor incisal edge extruded more in relation to Stomion Superiorus in the non-extraction group. 60 Appendix Table A.1: Landmarks and definitions Landmark Sella Abbreviation S Nasion N Prosthion PR Maxillary incisor apex edge U1a Maxillary incisor incisal edge Stomion Superiorus U1i Mandibular incisor incisal edge L1i SS 61 Definition The center of the pituitary fossa. The most anterior point of the frontonasal suture. The most anterior point on the maxillary alveolar process in the midline. The most apical point of the maxillary central incisor. The incisal edge of the maxillary central incisor. The most inferior point on the curve of the upper lip. The most incisal point of the mandibular central incisor. Table A.2: Planes and definitions Plane Y-axis Abbreviation Y A plane A B plane B C plane C Mandibular plane MP Palatal plane PP Functional occlusal plane FOP 62 Definition Vertical plane originating at Sella perpendicular to Sella to Nasion plan minus 7 degrees. Sella to Nasion plane minus 7 degrees. Perpendicular from Y-axis to Stomion Superiorus. Perpendicular from Y-axis to maxillary central incisor incisal edge. Line connecting Gonion and Menton. Gonion determined by bisecting the angle formed by tangents to the posterior border of the ramus and inferior border of the mandible. Line from Anterior Nasal Spine to Posterior Nasal Spine. Line bisecting the maxillary and mandibular first molars and premolars, not taking into account the position of the incisors. Figure A.1: Drawbridge effect5,18,19 illustration Figure A.2: Drawbridge effect.5,18,19 Incisors rotate around the center of rotation away from the occlusal plane as they are proclined and toward the occlusal plane as they are retroclined. This retroclination causes the incsisors to relatively extrude.3,21 63 List of References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. Peck S. Dentist, artist, pioneer: orthodontic innovator Norman Kingsley and his Rembrandt portraits. JADA 2012;143(4):393-7. Beane RA, Jr. Nonsurgical management of the anterior open bite: a review of the options. Semin Orthod 1999;5(4):275-83. Sarver DM, Weissman SM. Nonsurgical treatment of open bite in nongrowing patients. Am J Orthod Dentofacial Orthop 1995;108(6):651-9. Ngan P, Fields HW. Open bite: a review of etiology and management. Pediatr Dent 1997;19(2):91-8. Ng CS, Wong WK, Hagg U. Orthodontic treatment of anterior open bite. Inter J Pediatr Dent 2008;18(2): 78-83. Ghaffar F, Fida M. Effect of extraction of first four premolars on smile aesthetics. Eur J Orthod 2011; 33(6):679-83. Bowman SJ. More than lip service: facial esthetics in orthodontics. JADA 1999;130(8):1173-81. Jacobson A. The "Wits" appraisal of jaw disharmony. Am J Orthod Dentofacial Orthop. 1975;67(2):125-38. Kim E, Gianelly AA. Extraction vs Nonextraction: Arch Widths and Smile Esthetics. Angle Orthod 2003;73(4): 354-8. Johnson DK, Smith RJ. Smile esthetics after orthodontic treatment with and without extraction of four first premolars. Am J Orthod Dentofacial Orthop 1995;108(2):162-7. Meral O, Iscan HN, Okay C, Gursoy Y. Effects of bilateral upper first premolar extraction on the mandible. Eur J Orthod 2004;26(2):223-31. Spahl TJ, Witzig JW. The clinical management of basic maxillofacial orthopedic appliances. PSG Publishing Company;1987. Luppanapornlarp S, Johnston LE, Jr. The effects of premolar-extraction: a long-term comparison of outcomes in "clear-cut" extraction and nonextraction Class II patients. Angle Orthod 1993;63(4):257-72. Ong HB, Woods MG. An occlusal and cephalometric analysis of maxillary first and second premolar extraction effects. Angle Orthod 2001;71(2):90-102. Saelens NA, De Smit AA. Therapeutic changes in extraction versus non-extraction orthodontic treatment. Eur J Orthod 1998;20(3):225-36. 64 16. 17. 18. 19. 20. 21. 22. 23. Bishara SE, Cummins DM, Zaher AR. Treatment and posttreatment changes in patients with Class II, Division 1 malocclusion after extraction and nonextraction treatment. Am J Orthod Dentofacial Orthop 1997;111(1):18-27. Ramos AL, Sakima MT, Pinto Ados S, Bowman SJ. Upper lip changes correlated to maxillary incisor retraction: a metallic implant study. Angle Orthod 2005;75(4):499-505. Justus R. Iatrogenic Effects of Orthodontic Treatment: Decision-Making in Prevention, Diagnosis, and Treatment. Springer International Publishing;2015. Shrestha BK. Orthodontic Treatment of Anterior Dental Open Bite with Drawbridge Effect: A Case Report. Orthod J Nepal 2013;3(1):69-72. Proffit WR, Fields, HW, Sarver, DM. Contemporary Orthodontics. Mosby Elsevier; 2007. Burford D, Noar JH. The causes, diagnosis and treatment of anterior open bite. Dent Update. 2003;30(5):235-41. Sabri R. The eight components of a balanced smile. J Clin Orthod 2005;39(3):155-67. Mackley RJ. An evaluation of smiles before and after orthodontic treatment. Angle Orthod 1993;63(3):183-9. 65 Vita Auctoris Daniel James Floyd was born on September 8, 1983 in Corvallis, Oregon to Donald and Carol Floyd. He grew up in Albany, Oregon and graduated from Santiam Christian High School in 2002. After high school, he attended Arizona State University in Tempe, Arizona and concentrated his studies in business and biology for four years. In 2006, he began dental school at Oregon Health Sciences University in Portland, Oregon and graduated with a Doctor of Dental Medicine degree in 2010. as a general dentist for three years. He then worked In 2013, he began his orthodontics residency at Saint Louis University. He expects to receive his Masters of Science in Dentistry degree in December 2015. Daniel plans to practice in Oregon after receiving his degree. Go Hawks. 66