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CEPHALOMETRIC EVALUATION OF ADULT ANTERIOR OPEN BITE NONEXTRACTION TREATMENT WITH INVISALIGN Shuka Moshiri, B.A., 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: Associate Professor Ki Beom Kim, Chairperson and Advisor Professor Eustaquio A. Araujo Assistant Clinical Professor Julie F. McCray i DEDICATION I dedicate this work to my parents, Fariba and Farhad Moshiri, whose unending love and support has enabled me to become the person I am today. I have never witnessed two people pour so much of their heart and energy into their children. They are the ultimate example of self-sacrifice and unconditional love, and I’m beyond grateful to have them as parents. To my brother, Mazyar Moshiri, who has not only gracefully carried forth our family’s legacies, but has surpassed our expectations. He is an inspiration to me and I couldn’t be more proud to call him my brother; his leadership has impacted my life greatly. To my friends who, along with family, are the backbone of my life. To the faculty at Saint Louis University, who are the heartbeat of our program. The knowledge you impart onto your students is a gift that lays the groundwork for their future; this is absolutely invaluable. ii ACKNOWLEDGEMENTS The following individuals deserve special acknowledgement for their contribution to this project: Dr. Ki Beom Kim. Thank you for accepting the role as my advisor and chairperson of my thesis committee. Your constant patience, guidance and support were integral to the completion of this work. The dedication you give towards your students resonates in our program. Dr. Eustaquio Araujo. Thank you for your encouragement and mentorship through this process. You are an instrumental figure in many lives and to be called your student is an honor. Dr. Julie F. McCray. Thank you for taking time out of your busy private practice schedule to teach us clinically at SLU. Your time and genuine interest in my thesis project was always greatly appreciated. Dr. Willy Dayan. Thank you for working tirelessly with me to help procure the majority of my thesis sample. You opened up your practice and home to me and treated me like family. Your hospitality and guidance will forever be remembered. Dr. Mazyar Moshiri and Dr. Jonathan Nicozisis. Thank you for providing the additional records used for my sample. In spite of your demanding practice schedules, you iii were both extremely prompt in your correspondences with me and went out of your way to help. the support you’ve shown. iv I’m very grateful for TABLE OF CONTENTS LIST OF TABLES......................................... viii LIST OF FIGURES.......................................... ix CHAPTER 1: INTRODUCTION................................... 1 CHAPTER II: REVIEW OF THE LITERATURE...................... 5 Anterior Open Bite ...................................... 5 Definition ............................................ 5 Etiology .............................................. 5 Thumb and finger sucking............................. 7 Tongue thrust........................................ 8 Airway.............................................. 11 Skeletal growth aberrations......................... 16 Temporomandibular joint pathology................... 17 Morphology of Skeletal Open Bite ..................... 17 Face height......................................... 18 Palatal plane....................................... 19 Occlusal plane...................................... 20 Cranial base........................................ 21 Mandibular plane.................................... 21 Morphology of Dental Open Bite ....................... 23 v Diagnosis ............................................ 23 Treatment ............................................ 24 Multiloop edgewise archwire......................... 26 Extractions......................................... 27 Skeletal anchorage systems.......................... 29 Fixed appliance therapy............................. 30 Surgery............................................. 32 Invisalign ............................................. 33 Statement of Thesis .................................... 37 LITERATURE CITED ....................................... 39 CHAPTER 3: JOURNAL ARTICLE............................... 46 Abstract ............................................... 46 Introduction ........................................... 47 Purpose ................................................ 50 Materials and Methods .................................. 50 Sample ............................................... 50 Data Collection ...................................... 52 Statistical Methods .................................. 57 Results ................................................ 57 Discussion ............................................. 60 vi Angular Measurement Changes .......................... 62 Linear Measurement Changes ........................... 64 Conclusion ............................................. 70 Appendix ............................................... 71 Literature Cited ....................................... 73 Vita Auctoris .......................................... 77 vii LIST OF TABLES Table 3.1 - Measurement definitions . . . . . . . . . . . . . 54 Table 3.2 - Descriptive statistics of T1 and T2 . . . . . . . 58 Table 3.3 - Descriptive statistics of treatment changes . . . 59 Table 3.4 – Reliability statistics . . . . . . . . . . . . . 59 Table A.1 - Sample treatment duration . . . . . . . . . . . . 71 Table A.2 - Sample angle classification and crowding . . . . .72 viii LIST OF FIGURES Figure 2.1 – Example of maxillary MEAW wire . . . . . . . . . 27 Figure 2.2 - Example of maxillary Invisalign aligner . . . . 34 Figure 3.1 – Anatomical landmarks . . . . . . . . . . . . . . 53 Figure 3.2 - Cephalometric angular measurements . . . . . . . 55 Figure 3.3 – Cephalometric linear measurements . . . . . . . 56 Figure 3.4 – Sample superimposition of patient #12 . . . . . . 65 ix CHAPTER 1: INTRODUCTION Open bites pose as one of the more challenging dentofacial deformities in the orthodontic world, as they tend to defy treatment.1-3 Indeed, many researchers contend that vertical discrepancies are more difficult to manage than those in the anteroposterior dimension.4, 5 The complexity of this particular bite stems from both the mechanics needed to treat it and the efforts to combat its high relapse tendency. Due to lack of anterior contact, anterior open bites can lead to excessive wear of the posterior dentition, as the patient lacks anterior disclusion. Impairments with mastication and speech, in addition to dissatisfaction with the esthetics of an open bite, can negatively impact patients on a psychological and emotional level.6 The etiology of anterior open bites is complex and multifaceted. It may develop from either oral habits, excessive growth of lymphatic tissues, tongue position, or a genetic predisposition. While growing patients with oral habits may be treated with interceptive orthodontic appliances, treatment of adult patients presents a more complex picture. As Nahoum7 stated: “The diagnosis of a growing child is different from that of an adult. 1 The adult presents us with a fait accompli. There is no hope for improvement without treatment.” Thus, non-growing patients with anterior open bites are often prescribed a treatment plan involving a combination of surgery and orthodontics.8 Greenlee et al.’s9 meta-analysis on the long-term stability of treatment of anterior open bites found that both surgical and non-surgical correction had success rates greater than 75% (with an 82% mean stability value for patients treated surgically and 75% for patients treated with orthodontics only). This indicates that nonsurgical orthodontics has nearly equal long-term stability outcomes, while overall being a less invasive and more economical option for the patient. Non-surgical adult treatment of anterior open bites involves either extrusion of the anterior segment or, less commonly, intrusion of over extruded posterior segments. The rising popularity of adult orthodontics, and lack of guaranteed stability with both fixed appliance therapy and surgery, has generated impetus to discover more effective treatment modalities for anterior open bites. One alternative practitioners have turned towards is that of clear aligner therapy. Upon arrival to the market, Invisalign (registered trademark of Align Technology, Inc., Santa Clara, CA) was promoted as an esthetic alternative to fixed labial 2 appliances.10 Initially, it was indicated for low complexity cases, without skeletal discrepancies, mainly involving mild crowding. Since its inception, the appliance has undergone several iterations to improve its ability to achieve proper alignment and occlusion. The Invisalign system has rapidly evolved into what is now its sixth generation; newly incorporated features ostensibly have enabled it to treat more complex malocclusions. Although the literature examining orthodontic treatment with Invisalign is limited, a few investigators have demonstrated its successful management of mild anterior open bites.11-13 The appliance is purported to have a bite block effect and to maintain vertical control, two traits that make it an ideal treatment modality for open bite cases. Unfortunately, the few published studies are case reports that do not adequately evaluate the appliance’s capacity to maintain vertical control, a parameter that is often worsened by the extrusive effects of fixed appliance therapy. The purpose of this study is to evaluate the vertical effects of non-extraction, adult anterior open bite treatment with the Invisalign system. A cephalometric appraisal will be conducted, as no current studies have assessed the vertical dimension in this manner. It would be 3 beneficial to understand Invisalign’s influence on this dimension in order to understand the appliance’s capacity for vertical control. 4 CHAPTER II: REVIEW OF THE LITERATURE Anterior Open Bite Definition Several conflicting definitions for dental anterior open bites exist1, but the explanation that prevails in the literature defines anterior open bites as a lack of vertical overlap of the incisors.14-17 Its prevalence and severity varies among different races; for the U.S. population alone, studies have reported open bites in 16.3% of black children and 4% of white children.18 The incidence of open bites is reported to decrease from the mixed dentition period into adulthood.19 This decline is a byproduct of normal eruptive patterns, involution of the adenoids, development of a normal adult swallow, and cessation of oral habits.6 Although the prevalence appears low, approximately 17% of orthodontic patients possess anterior open bites20, indicating that thorough knowledge of its diagnosis and treatment is paramount. Etiology A myriad of etiological influences may contribute to the development of an anterior open bite. Practitioners often focus so closely on the dental and skeletal complex 5 that they overlook other external factors, such as muscular and soft tissue components, that may be variables to consider in the malocclusion. The treatment indicated, and thus rendered, should depend upon the etiology behind each specific case. Vertical relationships are established and dictated by the dynamic interplay between neuromuscular activity, skeletal growth, dentoalveolar bone growth, eruption patterns and oral habits.19 Some hereditary and environmental factors contributing to open bites include: vertical facial growth pattern, nasal airway obstruction, abnormal tongue size or posture, and nonnutritive sucking habits.6 Open bites during the primary and mixed dentition years are mostly self-limiting. In a cross-sectional study examining 1,408 Navajo children ranging between ages 7-21 years of age, Worms19 discovered 80% had spontaneous correction of their anterior open bites as they progressed from mixed dentition into permanent dentition. In particular, a marked decrease in prevalence was noted between the transition from the age group of 7-9 to 10-12 years of age. Much of the correction observed was attributed to growth that occurs between transitional dental periods and the acquisition of normal swallowing patterns. Overall, it was found that open bites are in a 6 constant state of flux during the growth period and that the prevalence varies with age and sex. If the open bite extends into the permanent dentition phase, however, orthodontic and/or surgical correction may be needed to close the bite. Thumb and finger sucking Non-nutritive sucking continues to be one of the major causes of anterior open bite amongst children.8 Distinguishing characteristics of a habitual dentoalveolar open bite enables the practitioner to differentiate it from one that is skeletal in nature. Anterior teeth are usually over-erupted in skeletal open bites; whereas they tend to be under-erupted with inadequate development of the anterior alveolar processes, due to pressure of the foreign object, in a habitual open bite.4 Often, the spatial disposition of the teeth lends evidence to the offending oral habit. Common features of a thumb-sucker, for example, include proclined maxillary incisors, retroclined mandibular incisors1, and an asymmetric anterior open bite mirroring the shape of the thumb. An open bite due to over usage of a pacifier would, instead, manifest as undereruption of maxillary and mandibular incisors, with the open bite assuming a circular form.6 7 In a persistent thumb sucker, the tongue adopts an inferior position which, along with hyper function of the perioral musculature, causes maxillary constriction. According to Graber21, thumb sucking in the first four years of life is normal and may be a significant component of the child’s psychological and emotional development. It is believed that that the habit is self-limiting and will decline with normal growth and development. Beyond approximately 3.5 years of age, a continuation of the habit may be indicative of delayed psychological maturation.21 Ultimately, the duration and intensity of the habit will determine the severity of the open bite.1 More importantly, if the habit does not cease at an appropriate time, the sequela may remain permanent. The open bite and increase in overjet that follows a thumb-sucking habit may gradually lead to secondary dysfunctions such as perioral muscle aberrations, compensatory tongue thrust during deglutition and mentalis strain.21 The concern, then, lies in the potential for the sucking habit to pave the way for more harmful forces to enhance the open bite. Tongue thrust In the longstanding debate over etiology of anterior open bites, the exact influence of the tongue remains 8 unresolved. A tongue thrust occurs when the tongue protrudes against or between the incisors during deglutition, resulting in excessive circumoral activity.16 The question still persists: Does the tongue thrust cause the open bite or does the open bite cause the tongue thrust? While some researchers consider the tongue thrust as the primary etiological factor behind open bites, others argue that tongue thrust is a result of the open bite itself. Straub22 submits that abnormal swallowing and tongue thrusts cause open bites, but no data is presented to substantiate his assertion. Subtelny & Sakuda17 suggest, instead, that the tongue adapts secondarily to the anterior opening created by the thumb or finger. This, they reason, is why spontaneous self-correction of habit-related open bites occurs once the habit is eradicated. When the habit ceases, anterior teeth erupt and the tongue readapts to the new occlusion. Nevertheless, they do acknowledge that an excessively large or hyperactive tongue with a protruded position may cause an open bite. Tongue thrusting may be a result of multiple influences. Use of tongue thrusts during deglutition, also referred to as infantile swallowing, may be the primary mode of swallowing up to ten years of age.16 As previously noted, the maturation of this swallowing reflex might serve 9 to explain the spontaneous correction of open bites Worms19 discovered to occur between the mixed and permanent dentition phases. In addition to compensatory tongue thrust secondary to anterior open bites, Subtelny and Sakuda17 suggested that severely enlarged tonsils and adenoids may lead to mechanical obstruction of the oropharynx and subsequent posturing of the tongue in a forward position. It is worth noting that the prevalence of tonguethrusting is greater than the open bite malocclusion itself.16 Those who ascribe to the camp that tongue pressure from thrusting is insufficient to cause the open bite believe that the resting posture of the tongue is more likely the culprit behind the malocclusion. The teeth appear to be unaffected by pressures exerted from the lip and tongue during abnormal swallowing; resting posture holds greater weight, as it can affect the eruption of teeth. As per the equilibrium theory, tooth movement is a consequence of light, continuous forces, where the duration of force outweighs force magnitude.23 Proffit23 argues that the dentition is able to resist the short-acting forces of tongue thrusting, which he believes to be more of an effect- than cause- of open bites. In further support of this idea, individuals may demonstrate consistent, abnormal 10 swallowing activity with tongue thrusts but have a normal occlusion.24 Airway The influence of naso-respiratory obstruction on facial growth and form has long been a contentious matter. The most common cause of mouth breathing is due to enlarged adenoids6, 25 , although chronic allergies, nasal infections, blocked turbinates and a deviated septum are other known causes.16 When an oral mode of respiration dominates, postural changes take place that aid in opening the oralpharyngeal airway, namely the lips separate and the mandible drops down and back. It is thought that a more vertical pattern of facial growth will ensue; with the mandible open, this would promote eruption of the posterior teeth and increase the lower anterior facial height, which may heighten the potential for an anterior open bite to develop.6, 26 There are several features supposedly typical of persons with enlarged adenoids who are mouth-breathers, and the term “adenoidal facies” has been coined to describe this condition. Common characteristics of adenoidal facies include downward and backward posturing of the mandible, incompetent lips, increased lower face height, and small 11 underdeveloped nostrils.3 Intraorally one might encounter a constricted maxillary arch, a high palatal vault and possibly a posterior crossbite. Many researchers have tried to resolve the form and function debate behind this craniofacial morphology and respiratory behavior. some25, 27 While argue that adenoidal facies is the manifestation of an obstructed airway, others28, 29 oppose with the idea that the condition is genetically predetermined and thus inherited. Many researchers stand firmly behind the notion that enlarged adenoids affect the mode of breathing and, in turn, facial growth and characteristics of the dentition. Linder-Aronson30 studied a group of children scheduled to undergo adenoidectomies and found that mouth breathing was prevalent in children with large adenoids and a small nasopharynx. The children presented with constricted maxillary arches, crossbites or a crossbite tendency and retroclination of the upper and lower incisors. Furthermore, nasal obstruction due to adenoids was seen most in leptoprosopic children who had a small nasopharynx. While acknowledging the complexity of the issue, he admits that other causal relationships are likely involved, and suggests that perhaps the size of the nasopharynx is what causes the mouth-breathing and possibly dictates the size 12 of the adenoids. In their study examining facial growth patterns in children who are mouth-breathers versus nose breathers, Bresolin et al.27 discovered that their mouth breathers had longer faces, larger gonial angles, deeper and narrower palatal vaults, and more retrognathic mandibles as compared to nose breathers, which gives further credence to the claim that upper respiratory obstruction and mouth breathing leads to deviant facial growth. A well-known study designed to test the relationship between mouth breathing and malocclusion was conducted by Harvold31 in 1981. Nose plugs were used to obstruct the nasal passages in a group of rhesus monkeys in order to induce mouth breathing and examine the resulting changes. The animals responded differently, but eventually all acquired facial and dental characteristics different from that of the control group, including increased facial height, mandibular plane angle and gonial angle.31 Caution must be taken in extrapolating these findings to understand mouth breathing in humans, as total nasal obstruction is a rare occurrence in humans. Rather, a combination of oral and nasal airflow more accurately describes the human respiratory mode. 13 Other investigators assert that mouth-breathing is not capable of affecting facial growth considerably enough to result in adenoid facies. Ballard28 asserts his longitudinal studies confirm that orofacial morphology is generally constant throughout growth and the deviations observed with adenoid facies are, in fact, predetermined morphological traits. Others have noted that adenoidal facies does not necessarily exist in all children with obstructive adenoids29 and not all patients with enlarged adenoids achieve nasal respiration after an adenoidectomy.3 Fields et al.32 attempted to compare breathing behaviors between normal and long-faced adolescents. Even though differences in airway variables, such as minimal crosssectional nasal area and tidal volume, were not statistically different between the two groups, long-faced subjects had a reduced percentage of nasal breathing. In other words, although measures of respiratory function were comparable between both groups, they still demonstrated significantly different modes of breathing. This implies that airway patency is not always related to breathing mode. Perhaps some individuals with normal airways remain mouth breathers out of a habit stemming from a previously established behavior. 14 A definitive cause and effect relationship cannot be established between breathing mode and vertical dentofacial morphology, as many unanswered questions still remain. Most studies that examine the interaction between respiratory obstruction and facial morphology are subjective in nature and fail to adequately define nasal obstruction. Furthermore, the diagnostic tests that otorhinolaryngologists use to assess airway obstruction are neither valid nor reliable.3 There are, likewise, several flaws inherent in airway studies, mainly that they base their quantification of airway size and patency off of cephalometric radiographs. While such studies may reveal a positive correlation between these airway measurements and airflow, one must assess the validity in exploring a three-dimensional structure via a two-dimensional depiction.2, 3 Another concern is that investigators use nasal resistance to explain respiratory behavior, but nasal resistance measurements have limitations that do not enable it to be correlated with respiratory mode.2 At present, we do not know what amount of nasal obstruction must be present to influence facial growth or during which time period this impediment exerts its greatest effect.3 15 Until these concerns are addressed, we can at best acknowledge these associations with caution. Skeletal growth aberrations In open bites that continue into, or even develop in, the late stages of growth, one must consider aberrant skeletal growth as a causative factor. As Nanda33 mentions in his study examining vertical growth, “The expression of disharmonious proportions in the facial skeleton can be attributed to the failure of normal, coordinated growth of the various regions of the craniofacial complex in terms of timing, magnitude, and direction.” A favorable growth pattern could perhaps close the bite and improve the prognosis of the treatment. Conversely, if a particular structure exhibits deviant growth while other sites grow normally, an open bite could result. Bjork34 states genetic and environmental factors that induce growth in the molar region, without adequate compensatory growth at the condyle or ramus can lead to an anterior open bite. Schudy35 adds that overbite is dictated by the relationship between vertical and horizontal growth. He believes that downward movement of the maxillary molar during growth is the most important determinant of facial height and accounts for seventy per cent of vertical facial growth. 16 Therefore growth in strategic sites, such as the posterior face height, may ultimately govern the success of treatment.7 Temporomandibular joint pathology Condylar resorption may result from an array of etiologies including condylar fractures, autoimmune diseases, rheumatoid arthritis, orthognathic surgery, and TMJ internal derangement. It should be considered in the differential diagnosis of patients who present with an acquired and progressive open bite. Open bites due to condylar resorption may lead to clockwise rotation of the mandible, with a resultant Class II malocclusion and mandibular retrognathia.36 Morphology of Skeletal Open Bite Categorizing an open bite as entirely skeletal or dentoalveolar is problematic, as many open bites feature elements of both kinds of dysplasia. Nevertheless, the skeletal morphology between a skeletal versus a habitual dentoalveolar open bite is quite different. Various skeletal components have been studied in an attempt to characterize skeletal open bites. Unfortunately, no single site can be pinpointed as a marker for all skeletal open bite cases. Rather, the sites of dysplasia are numerous 17 and differ for each individual patient, but all must be taken into account. According to Taibah et al,37 most researchers agree upon certain elements of an open bite, namely increased mandibular plane angle, increased gonial angle, increased lower anterior face height and decreased interincisal angle. Most disagreement has centered around the following features: palatal plane angle, cranial base angle, ramus height, upper face height, posterior facial height and dental heights.7, 13, 17, 33, 37-40 Findings for several of these dimensions will be elaborated upon briefly. Face height Most investigators7, 17, 37, 41, 42 agree that skeletal open bite patients have a larger lower anterior facial height (LAFH), which is often attributed to an upward cant of the anterior aspect of the palatal plane. It is thought by some that the upward cant produces a short upper anterior face height (UAFH), thereby lengthening the LAFH7. This finding is at variance with other studies, however, which reported normal upper facial dimensions.40, 42 Similar controversy exists over the posterior dimension. In their longitudinal study comparing open versus deep bite subjects, Sassouni and Nanda43 discovered 18 their open bite subjects had shorter rami, but Richardson’s44 retrospective study found no difference. Subtelny & Sakuda17 carried out a cephalometric comparison between twenty-five subjects with persistent open bites and thirty subjects with normal occlusions and reported no significant differences in the posterior vertical dimensions of the open bite patients. Other authors4, 38, 41 contend there is a definite decrease in the posterior vertical dimension. Nahoum7 believed that the ratio of upper anterior facial height to lower anterior facial height (UAFH/LAFH) was a vital measurement that should be used in diagnosing open bite cases. He submits that patients with a dental open bite and a UAFH/LAFH ratio below .650 will have a poor orthodontic prognosis and should be considered surgical candidates. Palatal plane It has also been suggested that the posterior segment of the palatal plane is tipped downward; this would displace the molars downward, leading to clockwise rotation of the mandible and an increased lower anterior facial height.41 With anterior nasal spine (ANS) being the point that divides UAFH from LAFH, Nahoum39 maintained that the 19 palatal plane contributes significantly to the anterior facial height ratio. He postulated that the tipping of the palatal plane results in a smaller upper face height and concomitant increase in LAFH in open bite subjects. This claim is substantiated through his data that depicted SN-PP angle measures that were smaller, and PP-MP angle measures that were greater, on average, for open bite subjects than for normal subjects. This remains controversial, however, as other authors have noted the SN-PP angle does not differ in open bite groups.17 Occlusal plane The occlusal plane is generally regarded as being steep in open bite patients.41 Conventionally, the constructed (bisected) occlusal plane bisects the overlap of the mesial cusps of the first permanent molars and the incisor overbite or open bite. Nahoum7 felt it was inaccurate to use this plane in open or deep bite cases and, instead, defined two separate, maxillary and mandibular occlusal planes. He observed the maxillary occlusal plane tends to cant upward alongside the palatal plane, versus the mandibular occlusal plane which tips downward. Nahoum38 and Taibah37 only reported significant increases in the mandibular occlusal plane angle, as 20 compared to control groups, while Nanda45 found no difference in the occlusal plane angle in open bite subjects. Cranial base It has been asserted that the cranial base angle is reflective of the glenoid fossa and temporomandibular joint positions. Therefore, an acute angle would suggest a forward position of the mandible, whereas an obtuse angle would reveal a retrusive position.45 Some investigators further advanced the idea that the cranial base angle is obtuse in open bite patients.41 Other authors contend that the cranial base angle is not significantly different in open bite patients and that the angle should not be utilized as a marker for identifying vertical dysplasias of the face.7, 45 Mandibular plane There is more consensus regarding hallmark features of the mandible, including an increased mandibular plane angle in open bite subjects.1, 37, 41 It is thought that an increased mandibular plane angle is indicative of a backwards rotational growth pattern, which increases the anterior facial height. Some investigators have attempted 21 to use the mandibular plane as a prognostic criteria in diagnosis of facial types and as a predictor of the direction of facial growth.46 However, Bjork34 asserts that an increased mandibular plane angle is apparent in both backward and forward mandibular growth patterns and is, therefore, not a valid predictor of facial growth. Although some angular and linear features prevail in skeletal open bites, no causal relationship can be established between these skeletal variations. Previous studies exhibit conflicting findings, likely owing to differences in methodology and sampling. While some studies are cross-sectional, others are longitudinal in design. Furthermore, the data sources are mixed, as certain studies compared open bites subjects to deep bite subjects, versus others compared open bite groups to normal control groups. This could introduce bias into the study, potentially skewing the results. Suffice it to say, several features do, in fact, have strong associations with skeletal open bites which, when identified, will enable the clinician to make a more apt diagnosis. 22 Morphology of Dental Open Bite Dentoalveolar open bites will exhibit characteristics indicative of the etiology. Since the bite opening is often due to a habit involving a foreign object, the open bite is usually restricted to the incisor region. Cephalometric analysis may show a decrease in alveolar height in the maxillary incisor region, as well as angular and linear evidence of protruded maxillary incisors.1 The mandibular incisors may be retroclined and crowded if a thumbsucking habit exists but the patient may not display skeletal characteristics related to vertical dysplasia,1 i.e., greater eruption of the dentoalveolar segments near the maxillary molars and incisors.17 Diagnosis For diagnostic measures, open bites have generally been grouped into two categories: 1) Dentoalveolar 2) Skeletal.1, 7 As previously discussed, dentoalveolar bites tend to be acquired via habits and do not display any overt craniofacial dysplasia. Skeletal open bites, on the other hand, are persistent bites that are likely linked to skeletal growth aberrations. The treatment plan must focus on the origin of the malocclusion for a favorable prognosis to occur. Given the complex nature of open bites, it is 23 often difficult to pinpoint the exact cause. Practitioners may be unable to correct the problem even if the cause is known, as would be the case with a patient who refuses to wear elastics or refuses surgery. Prognosis of treatment is contingent upon correct analysis of the open bite as one that derives from either a skeletal dysplasia or from a dentoalveolar origin. Proper attention must be given towards the methods used for diagnosis. Cephalometry, for instance, lacks the ability to account for functional patterns such as oral habits, nasal obstruction, abnormal swallowing and speech patterns, and atypical posturing of the tongue.4 As a result, the use of cephalometry alone for diagnostic purposes can potentially lead to misdiagnosis. This may be one of many reasons open bite cases are prone to relapse.47 As with most differential diagnosis, all probable genetic and environmental factors should be taken into account. Treatment Proper treatment of anterior open bites rests strongly on correct diagnosis and understanding of its multifactorial nature, and is the reason behind the multiple treatment modalities that exist to correct it. The practitioner must take care to employ the correct 24 mechanics and avoid worsening the open bite via further clockwise rotation of the mandible, which could lead to an increased anterior face height. Even more, the treatment plan should pertain to the etiology of the malocclusion for the prognosis to be stable. Orthodontists must be cognizant of what sorts of anatomic liabilities their mechanotherapy may have. For instance, if supra-eruption of maxillary incisors is prevalent in a skeletal open bite case, treatment with vertical elastics to extrude the incisors would prove fruitless. Treatment can be broken down into four main modalities: 1) Orthodontic mechanotherapy 2) Myofunctional therapy 3) Surgery 4) Combination of orthodontics & surgery. Some examples of treatments include high pull headgear, chin cups, multi-loop edgewise archwires, bite blocks, functional appliances, habit control, extractions and surgery. It is essential for the orthodontist to diagnose the etiology of the open bite carefully so that he or she may select the treatment most suitable for the patient. A few treatment modalities for adult open bites will be discussed briefly. 25 Multiloop edgewise archwire The multiloop edgewise archwire (MEAW) technique employs the use multilooped archwires and anterior vertical elastics to close anterior open bites. The objective of this technique is to achieve positive overbite, to correct the cant of the occlusal planes, and to address the mesial inclination of the posterior teeth.15 This is purportedly achieved via uprighting and retrusion of the posterior dentition, and retraction and extrusion of the anterior teeth, which enables the occlusal planes to converge.15 MEAW has been shown to have more dentoalveolar than skeletal effects. In a cephalometric evaluation of the treatment effects of MEAW, Endo et al.48 demonstrated that open bite correction with MEAW is predominantly due to extrusion and uprighting of the maxillary and mandibular incisors. Additionally, it was found that extrusion of the posterior segments caused unfavorable downward and backward rotation of the mandible.48 While MEAW has proved itself capable of treating anterior open bites, no significant skeletal changes are seen in nongrowing patients.49 A non-biased assessment of treatment efficacy is difficult, as most MEAW cases are performed in conjunction with extractions. Regarding stability, Kim et al.49 found a relapse rate of 6% in 26 growing patients and 10% in non-growing patients treated with his MEAW technique. These relapse rates appear low but, of the 55 patients he treated, the two-year follow up examined only 27 patients. The technique, albeit useful, is labor intensive, makes hygiene difficult, and requires full patient compliance with elastic wear. Figure 2.1 Example of maxillary MEAW wire15 Extractions Removal of first molars, second molars, and premolars have all been suggested as extraction options for treatment of anterior open bites. Many investigators believe that extractions contribute to a bite-closing effect. It is hypothesized that protraction of premolars or molars, without extrusion, into the extraction spaces will decrease the palatomandibular wedge, enabling counterclockwise rotation of the mandible.50 This would prove particularly beneficial for patients with high mandibular plane angles and increased facial heights. In reality, the potential 27 extrusive effects of orthodontic tooth movement may offset the benefits of the “wedge effect.”51 Extraction treatment in anterior open bite cases does not always lead to a mandibular rotational change or an improvement of the vertical dysplasia. Chua et al.52 reported that non- extraction treatment resulted in a downward and backward rotation of the mandible, accompanied by an increased LAFH. No significant changes in LAFH, however, were observed in subjects treated with extractions. Interestingly, when Zafarmand and Zafarmand51 examined the effects of bicuspid extraction on LAFH, they found LAFH increased significantly in their extraction groups. This was attributed to the “inherent extrusive effect of most orthodontic treatment modalities, i.e., molar protraction, which can be adversely compensative to facial height reduction.”51 While the aforementioned studies observed these effects in normodivergent patients, Cusimano et al.53 found that mandibular plane angle increased slightly, but not significantly, in their high angle patients post-extraction. They posit that occlusal movement of the molars nullified the bite-closing effect of posterior protraction. Therefore, it appears extractions either maintain the vertical dimension or slightly open it in high angle patients. Although some investigators believe extraction treatment of 28 hyperdivergent facial types reduces the vertical, these studies indicate that extraction treatment alone may not be sufficient in controlling the vertical. Skeletal anchorage systems Many investigators contend that maxillary incisor extrusion in adult patients may compromise the periodontal structures, lead to root resorption and ultimately jeopardize smile esthetics.54 Other authors have shown extruded teeth to be less stable than intruded teeth55 and have, instead, turned their efforts towards posterior intrusion. Molar intrusion is often needed if a skeletal open bite is to be corrected non-surgically.56 The use of skeletal anchorage systems, such as mini-implants and miniplates, has been promoted for closure of anterior open bites via molar intrusion. The studies conducted have shown promise, with true maxillary and mandibular molar intrusion leading to counterclockwise rotation of the mandible and, consequently, closure of the bite.54, 56 Concomitant reduction of the mandibular plane angle and anterior face height usually follow. Other advocated treatment alternatives such as highpull headgear, vertical chin cup, vertical holding 29 appliance, or an active vertical corrector cannot achieve effective molar intrusion in adult patients due to lack of rigid anchorage.56 Presumably, open bite closure through posterior intrusion and little to no anterior extrusion leads to more stable outcomes.55 Baek et al.57 investigated the long term stability of anterior open bite correction after intrusion of maxillary posterior teeth; they observed 22.88% relapse of the maxillary molars and 17% relapse of the incisal overbite after a three year follow up period. Unfortunately, the majority of literature involving skeletal anchorage and open bites are case reports lacking long-term follow up studies examining stability.20 Fixed appliance therapy Most of the literature evaluating the dento-skeletal effects of open bite therapy is centered on early treatment of growing patients. With the exception of case reports, there is a lack of sound data examining the effects of fixed appliance therapy in adult anterior open bite patients. When Remmers et al.58 evaluated treatment results and stability in a large group of anterior open bite adolescent patients, they discovered mean overbite increased from -3.2 mm pre-treatment to .4 mm posttreatment, with 71% of the sample obtaining a positive 30 overbite. Mean values for MP-PP and SN-MP decreased insignificantly, while the mean value for SN-PP increased insignificantly post-treatment. There were no appreciable differences in these angular measurements over five years post-treatment. The relapse rate was 27% five years post- treatment and, overall, 44% of the sample had an open bite at five years follow-up. The authors admit, “The poor treatment response between Ts and T0 in the present study raises the question whether conventional edgewise treatment can adequately control the vertical dimension.”58 One variation of the MEAW technique uses upper accentuated-curve and lower reverse-curve NiTi arch wires with intermaxillary elastics; this theoretically offsets the anterior intrusive forces of the wire and allows the posterior intrusive forces to take effect while extruding the anterior teeth. Once incisal overlap is achieved, stainless steel wires are placed and patients are directed to wear box elastics. Kucukkeles et al.59 observed the dentofacial effects of this method on adult anterior open bite patients and found that LAFH increased significantly by 2.5 mm (p < .001) post-treatment, which the authors believed to be a consequence of molar extrusion. Interestingly, the mandibular plane angle was maintained throughout treatment. SN to the functional occlusal plane 31 (FOP) decreased by 2.09˚ (p <.01) and the FOP-MP increased by 2.38˚ (p <.001). The counterclockwise rotation of the FOP can be accounted for by the extrusion of the lower premolars and uprighting of the lower molars. Upper and lower incisors and first molars were all extruded while being uprighted. As compared to the MEAW technique, this method proves to be more efficient, hygienic and comfortable for the patient. However, bite-closure is primarily achieved through extrusion of the incisors which is not always ideal, particularly in those individuals already presenting with excess gingival display at the outset of treatment. Surgery If patients present with a true skeletal open bite, a combined surgical-orthodontic approach is often encouraged to attain an esthetic and stable treatment result. A common surgical technique utilized for skeletal open bites is posterior maxillary impaction. Superior repositioning of the maxilla allows for autorotation of the mandible, closure of the bite, and a decreased LAFH.60 If the open bite it not severe, however, it is hard to justify the risks and trauma involved with surgery to achieve a correction with no guaranteed stability. 32 Invisalign Invisalign, clear removable aligners, was first introduced to the U.S. market in 199961; sixteen years later, the technology is still met with much skepticism. Initially, this was not unwarranted, as the earliest version of the system attempted to accomplish tooth movement solely via the aligner, without the use of auxiliaries or attachments. At that point in time, fixed appliances were undoubtedly better suited for treatment of moderate to severe malocclusions.10 Even after the second generation’s incorporation of attachments and buttons for the use of inter-maxillary elastics, crown and root movement limitations were still apparent. The appliance has continued to evolve rapidly, however, and is continuously modified in attempt to produce forces comparable to what fixed appliances exert.10 Development of improved attachments and tray material is postulated to have enabled better control of tooth movements that were originally unpredictable, i.e., rotational control, root torqueing, extrusion and closure of extraction spaces.10, 61 At present, the usage of the appliance has broadened to include treatment of complex malocclusions, including surgical cases and those involving extractions.13, 33 61 There is a paucity of literature pertaining to orthodontic treatment with the Invisalign system, even more only a handful related to treatment of open bites. Figure 2.2 Example of maxillary Invisalign aligner62 Invisalign has been suggested as a viable treatment option for mild anterior open bites. It has been hypothesized that the thickness of the aligners across the occlusal surfaces, in concert with masticatory forces, creates an intrusive force in the posterior segments, thus resulting in bite closure.61 Schupp et al.13 presented two case reports of anterior open bite patients treated successfully with Invisalign via a combination of incisor extrusion and molar intrusion. 34 Both cases were reported as stable one year post-treatment, with no noted relapse of the open bite. Apart from bite closure, treatment effects cannot be further assessed in these cases since no cephalometric analysis was presented. Guarneri et al.11 similarly illustrate an 18-month Invisalign treatment that achieved bite closure of a 4 mm open bite in a 35-year-old female via incisor extrusion. The superimposition of their pre- and post-treatment cephalometric tracings reveals the mandibular plane angle remained the same during treatment. This is in agreement with Boyd’s61 findings, as well. Harnick12 concurs that clear aligner therapy, as compared to fixed appliances, provides the biomechanical advantage of vertical control. Nonetheless, caution must be exercised in drawing conclusions from these case reports. As previously noted, it is hypothesized that the biteblock effect of Invisalign makes the system an ideal candidate for open bite treatment, as the thickness of the aligners supposedly contributes a posterior intrusive effect. As Iscan and sarisoy63 found, posterior bite blocks improve open bites by increasing the vertical dimension of the patient, thereby exerting pressure on the mandible’s neuromuscular system.61 The resultant vertical forces act to intrude the buccal segments and lead to a counterclockwise rotation of the mandible. 35 Other studies corroborate that a decrease in mandibular plane angle results from forwards and upward rotation of the mandible after treatment with posterior bite-blocks.64, 65 Invisalign has become increasingly sought after with adult orthodontics and demand for esthetic alternatives on the rise. The subtlety of the appliance appeals to patients, particularly adults who have undergone previous orthodontic treatment with fixed appliances and have no desire for retreatment in braces.61, 66 The appliance is still relatively new to the orthodontic world, however, and there are many unanswered questions concerning its clinical efficacy. Ultimately, the success of the Invisalign system rests in the hands of both the orthodontist and the patient. While patient compliance is essential, clinical expertise and a mastery of the ClinCheck system by the orthodontist plays a crucial role in the overall treatment outcome. As with fixed appliance therapy, each Invisalign treatment plan has a unique set of mechanics and methodologies behind resolving malocclusions. 36 Statement of Thesis The search for effective treatment modalities for anterior open bites continues. Controversy remains over the treatment indications for Invisalign and the complexity of cases that can be treated effectively with this system.67 To date, the majority of published studies pertaining to treatment of open bites with Invisalign are case reports. The lack of sound scientific evidence continues to feed the suspicion of many clinicians towards the appliance. As orthodontists, we are responsible for understanding and embracing the latest technological advancements in our field, albeit cautiously in order to protect our patients. Many patients, who would otherwise not have sought treatment, have considered orthodontic care because of the esthetic, removable nature of Invisalign. Until further investigation is conducted, its clinical potential will remain uncertain. A paucity of scientific data exists regarding treatment of adult anterior open bite patients with Invisalign. The purpose of this study is to conduct a cephalometric evaluation of the vertical effects of nonextraction, anterior open bite treatment in adult patients with the Invisalign system. 37 As such, this study will enable practitioners to consider an alternative treatment modality they can adopt into their orthodontic armamentarium. 38 LITERATURE CITED 1. Mizrahi E. A review of anterior open bite. Br J Orthod. 1978;5(1):21-7. 2. Fields HW, Warren DW, Black K, Phillips CL. Relationship between vertical dentofacial morphology and respiration in adolescents. Am J Orthod Dentofacial Orthop. 1991;99(2):147 -54. 3. Vig KW. Nasal obstruction and facial growth: the strength of evidence for clinical assumptions. Am J Orthod Dentofacial Orthop. 1998;113(6):603 -11. 4. Cangialosi TJ. Skeletal morphologic features of anterior open bite. Am J Orthod. 1984;85(1):28 36. 5. Richardson A. A classification of open bites. Eur J Orthod. 1981;3(4):289-96. 6. Rodrigues de Almeida R, Ursi WJ. Anterior open bite. Etiology and treatment. Oral Health. 1990;80(1):27-31. 7. Nahoum HI. Anterior open-bite: a cephalometric analysis and suggested treatment procedures. Am J Orthod. 1975;67(5):523-21. 8. Ngan P, Fields HW. Open bite: a review of etiology and management. Pediatr Dent. 1997;19(2):91-8. 9. Greenlee GM, Huang GJ, Chen SS, Chen J, Koepsell T, Hujoel P. Stability of treatment for anterior open-bite malocclusion: a meta-analysis. Am J Orthod Dentofacial Orthop. 2011;139(2):154 -69. 10. Hennessy J, E AA-A. Clear aligners generations and orthodontic tooth movement. J Orthod. 2015:1 9. 11. Guarneri MP, Oliverio T, Silvestre I, Lombardo L, Siciliani G. Open bite treatment using clear aligners. Angle Orthod. 2013;83(5):913 -9. 39 12. Harnick DJ. Using clear aligner therapy to correct malocclusion with crowding and an open bite. Gen Dent. 2012;60(3):218 -23. 13. Schupp W, Haubrich J, Neumann I. Treatment of anterior open bite with the Invisalign system. J Clin Orthod. 2010;44(8):501-7. 14. Artese A DS, Nascimento JM, Artese F. Criteria for diagnosing and treating anterior open bite with stability. Dental Press J Orthod. 2011;16(3):136-61. 15. Kim YH. Anterior openbite and its treatment with multiloop edgewise archwire. Angle Orthod. 1987;57(4):290-321. 16. Proffit WR, Mason RM. Myofunctional therapy for tongue-thrusting: background and recommendations. J Am Dent Assoc. 1975;90(2):403-11. 17. Subtelny JD, Sakuda M. Open-bite: Diagnosis and treatment. Am J Orthod. 1964;50(5):337 -58. 18. Kelly JE, Sanchez M, Van Kirk LE. An Assessment of the Occlusion of the Teeth of Children 6 11Years, United States. Vital Health Stat 11. 1973(130):1-60. 19. Worms FW, Meskin LH, Isaacson RJ. Open -bite. Am J Orthod. 1971;59(6):589-95. 20. Zuroff JP, Chen SH, Shapiro PA, Little RM, Joondeph DR, Huang GJ. Orthodontic treatment of anterior open-bite malocclusion: stability 10 years postretention. Am J Orthod Dentofacial Orthop. 2010;137(3):302.e1-8. 21. Graber TM. Thumb- and finger-sucking. Am J Orthod. 1959;45(4):258-64. 22. Straub WJ. Malfunction of the tongue. Am J Orthod. 1960;46(6):404-24. 23. Proffit WR. Equilibrium theory revisited: factors influencing position of the teeth. Angle Orthod. 1978;48(3):175-86. 40 24. Cleall JF. Deglutition: A Study of Form and Function. Am J Orthod. 1965;51:566-94. 25. Linder-Aronson S. Adenoids. Their effect on mode of breathing and nasal airflow and their relationship to characteristics of the facial skeleton and the denition. A biometric, rhino manometric and cephalometro-radiographic study on children with and without adenoids. Acta Otolaryngol Suppl. 1970;265:1-132. 26. Subtelny JD. Oral respiration: facial maldevelopment and corrective dentofacial orthopedics. Angle Orthod. 1980;50(3):147 -64. 27. Bresolin D, Shapiro PA, Shapiro GG, Chapko MK, Dassel S. Mouth breathing in allergic children: its relationship to dentofacial development. Am J Orthod. 1983;83(4):334-40. 28. Ballard CF. Mouth breathing. Proc R Soc Med. 1958;51(4):282-5. 29. Gwynne-Evans E. The so-called adenoid facies. Postgrad Med. 1956;19(3):253-5. 30. Linder-Aronson S. Effects of adenoidectomy on dentition and nasopharynx. Trans Eur Orthod Soc. 1972:177-86. 31. Harvold EP, Tomer BS, Vargervik K, Chierici G. Primate experiments on oral respiration. Am J Orthod. 1981;79(4):359-72. 32. Fields HW, Proffit WR, Nixon WL, Phillips C, Stanek E. Facial pattern differences in long faced children and adults. Am J Orthod. 1984;85(3):217-23. 33. Nanda SK. Patterns of vertical growth in the face. Am J Orthod Dentofacial Orthop. 1988;93(2):103-16. 34. Bjork A. Prediction of mandibular growth rotation. Am J Orthod. 1969;55(6):585 -99. 41 35. Schudy FF. The Control of Vertical Overbite in Clinical Orthodontics. The Angle Orthodontist. 1968;38(1):19-39. 36. Papadaki ME, Tayebaty F, Kaban LB, Troulis MJ. Condylar resorption. Oral Maxillofac Surg Clin North Am. 2007;19(2):223-34, vii. 37. Taibah SM, Feteih RM. Cephalometric features of anterior open bite. World J Orthod. 2007;8(2):145-52. 38. Nahoum HI, Horowitz SL, Benedicto EA. Varieties of anterior open-bite. Am J Orthod. 1972;61(5):486-92. 39. Nahoum HI. Vertical proportions and the palatal plane in anterior open-bite. Am J Orthod. 1971;59(3):273-82. 40. Hapak FM. Cephalometric Apprai sal Of The Openbite Case. The Angle Orthodontist. 1964;34(1):65 72. 41. Sassouni V. A classification of skeletal facial types. Am J Orthod. 1969;55(2):109-23. 42. Schudy FF. Vertical Growth Versus Anteroposterior Growth As Related To Function And Tr eatment. The Angle Orthodontist. 1964;34(2):75-93. 43. Sassouni V, Nanda S. Analysis of dentofacial vertical proportions. Am J Orthod. 1964;50(11):801-23. 44. Richardson A. Skeletal factors in anterior open bite and deep overbite. Am J Orthod. 1969;56(2):114-27. 45. Nanda SK. Growth patterns in subjects with long and short faces. Am J Orthod Dentofacial Orthop. 1990;98(3):247-58. 46. Bishara SE, Augspurger EF, Jr. The role of mandibular plane inclination in orthodontic diagnosis. Angle Orthod. 1975;45(4):273-81. 42 47. Arat M, Iseri H. Orthodontic and orthopaedic approach in the treatment of skeletal open bite. Eur J Orthod. 1992;14(3):207 -15. 48. Endo T, Kojima K, Kobayashi Y, Shimooka S. Cephalometric evaluation of anterior open -bite nonextraction treatment, using multiloop edgewise archwire therapy. Odontology. 2006;94(1):51 -8. 49. Kim YH, Han UK, Lim DD, Serraon ML. Stability of anterior openbite correction with multiloop edgewise archwire therapy: A cephalometric follow-up study. Am J Orthod Dentofacial Orthop. 2000;118(1):43-54. 50. Aras A. Vertical changes following orthodontic extraction treatment in skeletal open bite subjects. Eur J Orthod. 2002;24(4):407 -16. 51. Zafarmand AH, Zafarmand MM. Premolar extraction in orthodontics: Does it have any effect on patient's facial height? Journal of International Society of Preventive & Community Dentistry. 2015;5(1):64-8. 52. Chua AL, Lim JY, Lubit EC. The effects of extraction versus nonextraction orthodontic treatment on the growth of the lower anterior face height. Am J Orthod Dentofacial Orthop. 1993;104(4):361-8. 53. Cusimano C, McLaughlin RP, Zernik JH. Effects of first bicuspid extractions on facial height in high-angle cases. J Clin Orthod. 1993;27(11):594 8. 54. Sherwood KH, Burch JG, Thompson WJ. Closing anterior open bites by intruding molars with titanium miniplate anchorage. Am J Orthod Dentofacial Orthop. 2002;122(6):593 -600. 55. Proffit WR. Contemporary Orthodontics. Canada: Elsevier; 2013. 56. Umemori M, Sugawara J, Mitani H, Nagasaka H, Kawamura H. Skeletal anchorage system for open bite correction. Am J Orthod Dentofacial Orthop. 1999;115(2):166-74. 43 57. Baek MS, Choi YJ, Yu HS, Lee KJ, Kwak J, Park YC. Long-term stability of anterior open-bite treatment by intrusion of maxillary posterior teeth. Am J Orthod Dentofacial Orthop. 2010;138(4):396-8. 58. Remmers D, Van't Hullenaar RW, Bronkhorst EM, Berge SJ, Katsaros C. Treatment results and long term stability of anterior open bite malocclusion. Orthod Craniofac Res. 2008;11(1):32-42. 59. Kucukkeles N, Acar A, Demirkaya AA, Evrenol B, Enacar A. Cephalometric evaluation of open bite treatment with NiTi arch wires and anterior elastics. Am J Orthod Dentofacial Orthop. 1999;116(5):555-62. 60. Frost DE, Fonseca RJ, Turvey TA, Hall DJ. Cephalometric diagnosis and surgical -orthodontic correction of apertognathia. Am J Orthod. 1980;78(6):657-69. 61. Boyd RL. Complex orthodontic treatment using a new protocol for the Invisalign appliance. J Clin Orthod. 2007;41(9):525-47. 62. Align Technology, Inc. The Invisalign website: Align Technology, Inc.; 2015. Available from: www.aligntech.com 2015. 63. Iscan HN, Sarisoy L. Comparison of the effects of passive posterior bite-blocks with different construction bites on the craniofacial and dentoalveolar structures. Am J Orthod Dentofacial Orthop. 1997;112(2):171-8. 64. Barbre RE, Sinclair PM. A cephalometric evaluation of anterior openbite correction with the magnetic active vertical corrector. Angle Orthod. 1991;61(2):93-102. 65. Kalra V, Burstone CJ, Nanda R. Effects of a fixed magnetic appliance on the dentofacial complex. Am J Orthod Dentofacial Orthop. 1989;95(6):467 -78. 66. McKenna S. Invisalign: technology or mythology? J Mass Dent Soc. 2001;50(2):8-9. 44 67. Lagravere MO, Flores-Mir C. The treatment effects of Invisalign orthodontic aligners: a systematic review. J Am Dent Assoc. 2005;136(12):1724 -9. 45 CHAPTER 3: JOURNAL ARTICLE Abstract Objective: The purpose of this study is to evaluate, via cephalometric appraisal, the vertical effects of nonextraction treatment of adult anterior open bites with the Invisalign system. Materials and Methods: Lateral cephalograms of thirty adult anterior open bite patients treated with Invisalign (22 females, 8 males; mean age at start of treatment: 28 years 10 months; range: 16y11m – 54y3m) were collected from three private practitioners. Pre- and post-treatment cephalograms were traced to compare the following vertical measurements: SN to maxillary occlusal plane (SN-MxOP), SN to mandibular occlusal plane (SN-MnOP), mandibular plane to mandibular occlusal plane (MP-MnOP), SN to mandibular plane (SN-MP), SN to palatal plane (SN-PP), SN to gonion-gnathion plane (SN-GoGn), upper 1 tip to palatal plane (U1-PP), lower 1 tip to mandibular plane (L1-MP), mesiobuccal cusp of upper 6 to palatal plane (U6-PP), mesiobuccal cusp of lower 6 to mandibular plane (L6-MP), lower anterior facial height (LAFH), and overbite (OB). Paired t-tests and descriptive statistics were utilized to analyze the data and note any significant changes resulting from treatment. Results: Statistically 46 significant differences were found in overall treatment change for SN-MxOP, SN-MnOP, MP-MnOP, SN-MP, Sn-GoGn, L1MP, L6-MP, LAFH, and OB. Conclusions: The Invisalign system is a viable therapeutic modality for non-extraction treatment of adult anterior open bites. Bite closure was achieved by a combination of lower molar intrusion and lower incisor extrusion. Introduction Open bites pose as one of the more challenging dentofacial deformities in the orthodontic world, as they tend to defy treatment.1-3 Indeed, many researchers contend that vertical discrepancies are more difficult to manage than those in the anteroposterior dimension.4, 5 The complexity of this particular bite stems from both the mechanics needed to treat it and the efforts to combat its high relapse tendency. Due to lack of anterior contact, anterior open bites can lead to excessive wear of the posterior dentition, as the patient lacks anterior disclusion. Impairments with mastication and speech, in addition to dissatisfaction with the esthetics of an open bite, can negatively impact patients on a psychological and emotional level.6 47 The etiology of anterior open bites is one that is complex and multifaceted. It may develop from either oral habits, excessive growth of lymphatic tissues, tongue position, or a genetic predisposition. While growing patients may be treated with interceptive orthodontic appliances, treatment of adult patients presents a more complex picture once growth has ceased and habit-related sequela assume permanence. As Nahoum7 frankly stated: “The diagnosis of a growing child is different from that of an adult. presents us with a fait accompli. The adult There is no hope for improvement without treatment.” Thus, nongrowing patients with anterior open bites are often prescribed a treatment plan involving a combination of surgery and orthodontics.8 Greenlee et al.’s9 meta-analysis on the long-term stability of treatment of anterior open bites found that both surgical and non-surgical correction had success rates greater than 75% (with an 82% mean stability value for patients treated surgically and 75% for patients treated with orthodontics only). This indicates that nonsurgical orthodontics has nearly equal long-term stability outcomes, while overall being a less invasive and more economical option for the patient. Non-surgical adult treatment of anterior open bites involves either extrusion of the 48 anterior segment10 or, less commonly, intrusion of overextruded posterior segments.10-12 The rising popularity of adult orthodontics, and lack of guaranteed stability with both fixed appliance therapy and surgery, has generated impetus to discover more effective treatment modalities for anterior open bites. One alternative practitioners have turned towards is that of clear aligner therapy. Upon arrival to the market, Invisalign was promoted as an esthetic alternative to fixed appliances.13 Initially, it was indicated for low complexity cases, without skeletal discrepancies, mainly involving mild crowding. Since its inception, the appliance has undergone several iterations to improve its ability to achieve proper alignment and occlusion. The Invisalign system has rapidly evolved into what is now its sixth generation; newly incorporated features ostensibly have enabled it to treat more complex malocclusions. Although the literature examining orthodontic treatment with Invisalign is limited, a few investigators have demonstrated its successful management of mild anterior open bites.14-16 The appliance is purported to have a bite block effect and to maintain vertical control, two traits that make it a possible treatment alternative for open bite cases. Unfortunately, the few published studies 49 are case reports that do not adequately evaluate the appliance’s capacity to maintain vertical control, a parameter that is often worsened by the extrusive effects of fixed appliance therapy. Purpose The purpose of this study is to evaluate the vertical effects of non-extraction, adult anterior open bite treatment with the Invisalign system. A cephalometric appraisal will be conducted, as no current studies have assessed the vertical dimension in this manner. It would be beneficial to understand Invisalign’s influence on this dimension in order to understand the appliance’s capacity for vertical control. Materials and Methods Sample Pre-treatment (T1) and post-treatment (T2) lateral cephalograms of thirty adult anterior open bite patients treated with Invisalign were collected from three private practice orthodontists. Anterior open bite was defined as a lack of vertical overlap between the upper and lower incisors. The sample was comprised of 22 females and 8 males, with a mean age of 28.81 years (range: 16y11m – 50 54y3m) at the outset of treatment. No discrimination as to Angle classification of malocclusion was made. The sample consisted of 24 Angle Class I patients and 6 Angle Class II patients. Twenty-four sets of records were obtained from practice A, four sets of records were obtained from practice B, and two sets of records were obtained from practice C. The patient selection criteria were as follows: Patients were all non-growing at the outset of treatment, determined via the cervical vertebral maturation technique No vertical overlap between the upper and lower incisors, with edge-to-edge canines deemed acceptable No extractions of permanent teeth were performed during treatment No orthognathic surgery was performed as a part of treatment The patients were treated exclusively with Invisalign and anteroposterior elastics during treatment Pre- and post-treatment lateral cephalograms were available for each patient 51 Care was taken to ensure that all private practitioners had at least elite provider status, indicating that they treat, at minimum, up to one hundred Invisalign cases per year. The overall goal of each treatment was to achieve overbite reduction in order to attain vertical overlap, or positive overbite, of the maxillary and mandibular incisors. Data Collection Pre-treatment and post-treatment digital and analog lateral cephalograms were collected, scanned, and traced for each patient digitally in the Dolphin Imaging software program (Dolphin Imaging version 11.8 Premium). Thirty- three hard tissue landmarks were identified and traced, in addition to two reference landmarks on each radiograph (Figure 3.1). The mandibular and maxillary occlusal planes were manually traced and all occlusal plane measurements were measured manually. Six linear and six angular measurements were completed (Figure 3.2, Figure 3.3). 52 Figure 3.1. Anatomical landmarks: Sella(1); Nasion(2); Posterior nasal spine(3); Anterior nasal spine(4); U6 mesiobuccal cusp(5); L6 mesiobuccal cusp(6); U1 incisor tip(7); L1 incisor tip(8); Gnathion(9); Menton(10); Inferior gonion(11). 53 Table 3.1. Measurement definitions Measurement Definition SN-MxOP Angle formed by SN and the maxillary occlusal plane (plane drawn through the mesiobuccal cusp tip of the maxillary molar to the upper central incisor tip) SN-MnOP Angle formed by SN and the mandibular occlusal plane (plane drawn through the mesiobuccal cusp tip of the mandibular molar to the lower central incisor tip) MP-MnOP Angle formed by mandibular plane (inferior gonion to menton) and the mandibular occlusal plane SN-PP Angle formed by SN to palatal plane (ANS to PNS) SN-MP Angle formed by SN to mandibular plane (inferior gonion to menton) SN-GoGn Angle formed by SN and the plane drawn through the points inferior gonion and gnathion U1-PP The millimetric distance between U1 tip and the palatal plane (ANS to PNS) L1-GoGn The millimetric distance between L1 tip and the plane drawn through inferior gonion-gnathion U6-PP The millimetric distance between the mesiobuccal cusp tip of the maxillary molar and the palatal plane (ANS to PNS) L6-GoGn The millimetric distance between the mesiobuccal cusp tip of the mandibular molar and the plane drawn through inferior gonion-gnathion LAFH The millimetric distance between ANS and menton OB The vertical millimetric distance from U1 tip to L1 tip 54 Figure 3.2. Cephalometric angular measurements: SN-GoGn(1); SNMP(2); SN-MxOP(3); SN-MnOP(4); SN-PP(5); MP-MnOP(6). 55 Figure 3.3. Cephalometric linear measurements: U6-PP(1); U1PP(2); OB(3); LAFH(4); L1-GoGn(5); L6-GoGn(6). 56 Statistical Methods The data in this study was analyzed via IBM SPSS Statistics 23.0 statistical analysis software (SPSS Inc., Chicago, Illinois). Descriptive statistics and paired t- tests were used to compare the changes between pre- and post- treatment measurements. All digital and manual tracings were performed by the same investigator. To evaluate intra-examiner reliability, 10% of the cephalograms were chosen at random and re-traced; Cronbach’s alpha test was used to determine measurement reliability. Intra-class correlation values of at least 0.80 were considered acceptable in terms of reliability. Results Descriptive statistics (Table 3.2) and paired t-tests (Table 3.3) used to analyze the data revealed that nine of the twelve variables measured were statistically significant in overall treatment change. Statistically significant (p<.01) changes were found in SN-MxOP, SN-MnOP, MP-MnOP, SN-MP, SN-GoGn, LAFH, overbite, and L1-MP. Statistically significant (p<.05) changes were also observed in L6-MP. SN-PP, U1-PP, and U6-PP did not undergo any statistically significant changes. 57 Chronbach’s alpha tests for intra-examiner reliability was above 0.80 for all variables except for overbite (Cronbach’s alpha= 0.63). With regard to accuracy of measurements, overall, the original and repeated measurements were at an adequate level of reliability. Table 3.2. Descriptive statistics of T1 and T2. Measurement SN-MxOP (˚) Pre-treatment (T1) Mean S.D. 18.0 5.0 Post-treatment (T2) Mean S.D. 20.6 5.4 SN-MnOP (˚) 20.7 5.5 16.2 5.6 MP-MnOP (˚) 20.2 5.1 24.7 4.6 SN-PP (˚) 7.8 4.2 7.5 4.7 SN-MP (˚) 40.8 7.2 39.9 6.9 Sn-GoGn (˚) 37.6 7.1 36.7 6.9 LAFH (mm) 74.3 5.3 72.8 5.2 OB (mm) -1.8 1.2 1.5 .9 U1-PP (mm) 30.7 2.8 31.2 2.6 L1-MP (mm) 38.3 2.8 39.1 3.1 U6-PP (mm) 25.4 2.2 25.0 2.3 L6-MP (mm) 31.3 2.5 30.7 2.4 58 Table 3.3. Descriptive statistics of treatment changes. T1-T2 Difference Measurement Mean S.D. Significance SN-MxOP (˚) 2.6** 2.4 <0.001 SN-MnOP (˚) -4.6** 4.2 <0.001 MP-MnOP (˚) 4.5** 3.7 <0.001 SN-PP (˚) -0.3 2.4 0.505 SN-MP (˚) -0.9** 1.5 0.002 Sn-GoGn (˚) -0.9** 1.6 0.006 LAFH (mm) -1.5** 2.8 0.006 OB (mm) 3.4** 1.4 <0.001 U1-PP (mm) 0.5 2.0 0.137 L1-MP (mm) 0.8** 1.2 <0.001 U6-PP (mm) -0.4 1.4 0.118 L6-MP (mm) -0.6* 1.4 0.022 * denotes changes are significant at p<.05 ** denotes changes are significant at p<.01 Table 3.4. Reliability Statistics Variable Cronbach’s Alpha SN-MxOP .958 SN-MnOP .864 MP-MnOP .965 SN-PP .950 SN-MP .983 SN-GoGn .987 LAFH .993 OB .629 U1-PP .837 L1-MP .923 U6-PP .946 L6-MP .825 59 Discussion This study endeavored to evaluate the vertical effects of non-extraction, anterior open bite treatment in adult patients with the Invisalign system. A plethora of evidence lends credence to the idea that skeletal open bite patients tend towards high mandibular plane angles1, and large lower anterior facial heights (LAFH).7, 17, 18 12, 17-19 Schudy20 claimed the main goal of open bite treatment should be to prevent an increased anterior face height and emphasized that molars should not be extruded during treatment. However, the success of anterior open bite treatment is often gauged by positive maxillary and mandibular incisal overlap, which is usually obtained at the expense of adverse sequela. Fixed appliance therapy has a tendency to worsen the vertical dimension in open bite patients, who more often present as hyperdivergent, longfaced individuals.6, 17, 21, 22 Non-surgical options for correction of anterior open bites in adults are limited. It is commonly thought that extractions enable a bite-closing effect by allowing protraction into the extraction space, thereby decreasing the palatomandibular wedge. The literature regarding extraction treatment does not support this idea, however, as several authors have shown that extractions can, in 60 fact, lead to an increased lower anterior facial height23 and a larger mandibular plane angle.24 In actuality, protraction during space closure may cause occlusal movement of the posterior segments, which essentially cancels out the so-called “wedge effect.” Post-treatment increases in lower anterior facial height have been observed in non-extraction treatment as well.25 Anterior segments must be extruded via elastics, or posterior segments intruded, to achieve bite closure with fixed appliances. The multiloop edgewise archwire (MEAW) technique employs anterior elastics to achieve positive overbite, to correct the cant of the occlusal planes, and to address the mesial inclination of posterior teeth.26 Although the technique has proven capable of attaining bite closure, it is mainly via anterior extrusion.27 Previous cephalometric evaluation of the technique revealed insignificant changes in lower anterior face height and in the mandibular plane angle during treatment.27 Another variation of Kim’s26 technique instead uses reverse and accentuated curve NiTi archwires with elastics to achieve anterior extrusion. An appraisal of this method in adult anterior open bite patients found that lower anterior facial height increased significantly post-treatment, while the mandibular plane angle was maintained.28 Neither of 61 these modalities appear to contribute vertical improvements in non-growing patients. Bite closure via extrusion of anterior teeth may not be indicated for all adult patients presenting with anterior open bites. Even more, extrusion of the maxillary incisors is deemed unstable.29 Some investigators believe that maxillary incisor extrusion in adult patients may compromise the periodontal structures, lead to root resorption and ultimately jeopardize smile esthetics.10 Without the use of skeletal anchorage devices, true molar intrusion is very difficult to achieve in adult patients using fixed appliances.30 The use of skeletal anchorage systems for molar intrusion has proven effective with bite closure and resultant decreases in facial height, mandibular plane angle, and occlusal plane angle.10, 30 Unfortunately, the literature in this area is predominately compromised of case reports that lack long-term follow up studies investigating stability. Angular Measurement Changes In this study, the decision to split the occlusal plane angles was made, as Nahoum7 felt it was inaccurate to use one plane in open or deep bite cases and, instead, defined two separate, maxillary and mandibular occlusal 62 planes. SN-MxOP showed a statistically significant mean increase of 2.6˚. Conversely, Sn-MnOP decreased significantly by a mean of 4.6˚, indicating that again the bite closed either by incisor extrusion and/or molar intrusion. MP-MnOP increased significantly by a mean of 4.5˚; this finding indicates a decreased steepening of the mandibular occlusal plane due to bite closure. A statistically significant mean decrease of 0.9˚ in the SNMP angle and mean decrease of 0.9˚ in the SN-GoGn angle was observed, which we can attribute to counterclockwise rotation of the mandibular plane. For the sake of reliability, two mandibular planes were utilized: 1) one plane connecting inferior gonion to gnathion 2) one plane connecting inferior gonion to menton. We would expect to see a higher mean value with SN-MP than we would with SNGoGn, which is the case. However, the mean decreases posttreatment in both planes are equivalent. This rotation was not substantial enough to decrease the MP-MnOP angle, as the treatment effects on the mandibular occlusal plane superseded the skeletal autorotation. SN-PP did not display any significant change, as we might expect in a non-growing patient. 63 Linear Measurement Changes Following significant mandibular plane closure, there was also a statistically significant decrease in the lower anterior facial height by 1.5mm. Overbite increased substantially with a statistically significant mean increase of 3.4mm; this can be attributed to a combination of molar intrusion and incisor extrusion, as 1 mm of molar intrusion can lead to 3mm of anterior bite closure.29 U1-PP increased by a mean of 0.5mm and U6-PP decreased by a mean of 0.4mm. Although this indicates general extrusion of the maxillary incisors and intrusion of the maxillary molars, these changes were not statistically significant. However, L1-MP increased significantly by 0.8mm and L6-MP decreased significantly by 0.6mm. This indicates statistically significant mandibular molar intrusion and mandibular incisor extrusion in this sample. These results reveal that, overall, most of the dental treatment effects were greater in the mandibular arch (Figure 3.4). One possible reason for significant mandibular changes is that IPR was prescribed more in the mandibular arch; this would lead to more mandibular incisor extrusion during retraction and space closure. 64 Figure 3.4. Sample superimposition of patient #12 Green: before; Black: after 65 In this study, Invisalign successfully achieved anterior open bite closure via positive incisal overlap without negatively impacting the vertical dimension. Average treatment time for this sample was 21 months (Table A.1). The changes observed in the vertical parameters displaying statistical significance are indicative of bite closure and decreases in the vertical dimension. As previously noted, fixed appliance therapy has the potential to exert unwanted extrusive forces that may enhance the open bite and consequently worsen the vertical dimension. Additionally, anterior-posterior (AP) elastics used with fixed appliances tend to have extrusive effects that increase the vertical dimension. The majority of our sample presented with an Angle Class I malocclusion, with only six Class II patients. Klein reported control of the vertical, and even a decrease in the vertical dimension (SN-MP), in his study examining Class II correction with Invisalign and elastics.31 This finding was attributed to the constant presence of aligner material. The improvements in the vertical dimension seen in this study are akin to those observed subsequent to molar intrusion in skeletal anchorage cases, i.e. reduction in occlusal plane angle, mandibular plane angle, and lower anterior facial height.10, 30 66 It has been previously postulated that Invisalign exerts a bite-block effect during treatment.32 Most literature on bite-block therapy describes its effectiveness in treatment of children and growing patients. This functional appliance aims to control maxillary vertical skeletal and dental growth primarily by opening the patient past their normal vertical dimension.29 Typically, the amount of acrylic in the first molar area of these bite blocks may range in thickness from 5-10mm; this induces an artificial increase in the vertical dimension, thereby triggering a muscular response that creates a vertical intrusive force in the buccal segments, leading to counterclockwise rotation of the mandible.33 It is unlikely that Invisalign has the ability to exert the same intrusive forces in adults as we observe in children with bite block therapy. The thickness of each Invisalign aligner is 0.030 inches34 (equivalent to 0.76mm) which, when combined intraorally, may not be of adequate thickness to exceed the freeway space considerably enough to create a neuromuscular response. Additionally, functional contact of opposing teeth occurs approximately 18 minutes per day29, which is not of long enough duration to exert a significant intrusive force.35 Intrusive forces from the aligner must be requested by the provider in the 67 ClinCheck and programmed into the trays through the Invisalign technicians. The combined effect of the sequential progression of trays, with judicious selection and placement of attachments, ultimately dictates the amount of intrusion and tooth movement observed clinically. Given the appliance’s relatively recent inception and continual evolution, literature regarding efficacy of tooth movement is lacking. Schupp et al.16 reported 1mm of molar intrusion in their case report but there is not enough substantial evidence to understand how much posterior intrusion Invisalign is capable of achieving. The advantage of Invisalign in treating open bite malocclusion stems mainly from its full occlusal coverage effect. While intruding dentition, adverse or unwanted reciprocal extrusive movements are less likely to occur because of the presence of the aligner.15 Retention in anterior open bites is critical, especially when considering the vertical dimension of facial growth is the last to be completed. Extrusion of the posterior teeth, most commonly the maxillary molars, is cited as the most common cause for anterior open bite relapse in growing patients.29 Retention should therefore incorporate a means to control eruption of the posterior teeth, even in young adults. 68 As adult open bite malocclusions are uncommon and their treatment with Invisalign is a relatively new approach, one limitation of this study was obtaining a large sample size. Additionally, the retrospective nature of this study did not enable control of all treatment variables. Each case was treated with a different ClinCheck set-up that was contingent upon the patient’s specific diagnosis as well as the orthodontic provider’s devised treatment plan. Depending on the treatment warranted, providers may have either primarily requested molar intrusion, or anterior extrusion, or a combination of both. Future studies should incorporate a matched control group treated solely with fixed appliance therapy for further comparison of these modalities’ effects on the vertical dimension. Research focusing on the amount of molar intrusion that can be achieved with the appliance would be of great value. Lastly, prospective investigation lending insight into relapse of open bite cases treated with Invisalign is vastly important in order to appreciate the appliance’s capacity to preserve control of the vertical. 69 Conclusion 1) The Invisalign system is a therapeutic modality that can be effectively employed in non-extraction treatment of adult anterior open bites. 2) Bite closure was achieved by a combination of lower molar intrusion and lower incisor extrusion. 70 Appendix Table A.1. Sample treatment duration Pt # T1 Ceph T2 Ceph 1 5/29/08 12/8/10 Tx time (mo) 18 2 6/21/10 11/10/11 17 3 2/2/11 12/11/12 22 4 10/20/11 4/8/13 18 5 6/28/07 11/18/08 17 6 12/13/06 3/12/09 27 7 2/22/10 6/27/11 16 8 1/12/12 10/7/13 21 9 4/27/11 2/20/13 22 10 5/26/11 2/4/13 21 11 8/23/12 7/28/14 23 12 9/24/12 2/24/14 17 13 7/19/12 11/20/13 16 14 11/14/12 2/10/15 27 15 11/18/12 7/7/14 19 16 2/25/13 12/8/14 22 17 10/10/12 8/5/15 34 18 11/20/12 11/18/14 24 19 11/5/12 7/7/15 32 20 7/9/2009 6/1/11 23 21 10/24/12 6/10/14 20 22 8/9/12 2/3/15 30 23 4/9/13 11/26/14 19 24 2/2/14 1/7/15 11 25 3/04/12 8/20/13 17 26 7/18/11 4/23/13 21 27 7/7/11 2/5/14 31 28 7/8/11 2/6/14 31 29 4/3/12 3/4/14 23 30 10/22/13 9/30/15 23 71 Table A.2. Sample angle classification and crowding 1 Angle Classification Class I Maxillary Crowding Moderate Mandibular Crowding Moderate 2 Class I None None 3 Class I None None 4 Class I Mild Moderate 5 Class I Mild Mild 6 Class I None Mild 7 Class I Mild Mild 8 Class II None Mild 9 Class I Moderate Mild 10 Class I Moderate Moderate 11 Class I Moderate Moderate 12 Class II Mild Mild 13 Class II None None 14 Class I None Mild 15 Class I None Mild 16 Class I None None 17 Class I None None 18 Class II None Moderate 19 Class II None Mild 20 Class I None Mild 21 Class I Mild Mild 22 Class I None Mild 23 Class I Moderate Moderate 24 Class I None None 25 Class I Mild Mild 26 Class I Mild Moderate 27 Class II None Mild 28 Class I Mild Moderate 29 Class I None Mild 30 Class I Mild None Pt # 72 Literature Cited 1. Mizrahi E. A review of anterior open bite. Br J Orthod. 1978;5(1):21-7. 2. Fields HW, Warren DW, Black K, Phillips CL. 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Taibah SM, Feteih RM. Cephalometric features of anterior open bite. World J Orthod. 2007;8(2):145-52. 18. Sassouni V. A classification of skeletal facial types. Am J Orthod. 1969;55(2):109-23. 19. Schudy FF. Vertical Growth Versus Anteroposterior Growth As Related To Function And Treatment. The Angle Orthodontist. 1964;34(2):75-93. 20. Schudy FF. The Control of Vertical Overbite in Clinical Orthodontics. The Angle Orthodontist. 1968;38(1):19-39. 21. Subtelny JD. Oral respiration: facial maldevelopment and corrective dentofacial orthopedics. Angle Orthod. 1980;50(3):147 -64. 22. Sassouni V, Nanda S. Analysis of dentofacial vertical proportions. Am J Orthod. 1964;50(11):801-23. 23. Zafarmand AH, Zafarmand MM. Premolar extraction in orthodontics: Does it have any effect on patient's facial height? Journal of International Society of Preventive & Community Dentistry. 2015;5(1):64-8. 74 24. Cusimano C, McLaughlin RP, Zernik JH. 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Skeletal anchorage system for open bite correction. Am J Orthod Dentofacial Orthop. 1999;115(2):166-74. 31. Klein BM. A cephalometric study of adult mild class II nonextraction treatment with the invisalign system. Master's Thesis, Saint Louis University. 2013. 32. Boyd RL. Complex orthodontic treatment using a new protocol for the Invisalign appliance. J Clin Orthod. 2007;41(9):525-47. 33. Iscan HN, Sarisoy L. Comparison of the effects of passive posterior bite-blocks with different construction bites on the craniofacial and dentoalveolar structures. Am J Orthod Dentofacial Orthop. 1997;112(2):171-8. 75 34. Vlaskalic V, Boyd RL. Clinical evolution of the Invisalign appliance. J Calif Dent Assoc. 2002;30(10):769-76. 35. Proffit WR. Equilibrium theory revisited: factors influencing position of the teeth. Angle Orthod. 1978;48(3):175-86. 76 Vita Auctoris Shuka Moshiri was born on January 11, 1985 in St. Louis, Missouri to Dr.’s Farhad and Fariba Moshiri. preceded by her brother, Dr. Mazyar Moshiri. She is After graduating from John Burroughs high school in 2003, she attended Washington University in St. Louis where she obtained her Bachelor of Arts degree with a major in Psychology. She then moved to Kentucky, where she received her Doctor of Medicine in Dentistry degree at the University Of Louisville School Of Dentistry in 2011. Following her graduation, she completed an advanced year of training at a general practice residency program at Mercy Hospital in St. Louis. In 2013, she began her residency at Saint Louis University’s Orthodontic program with the goal of receiving her Master of Science degree in 2015. After she completes her training, she looks forward to working alongside her father and brother in their St. Louis family orthodontic practice. 77