The Influence of Labio-lingual and Mesio-distal Anterior Tooth Dimensions on Inter-arch Relationships: A Modified Anterior Bolton Analysis

Yelena Akselrod Beygelman
Chair of the Supervisory Committee:
Anne-Marie Bollen, Graduate Program Director
Department of Orthodontics

Introduction: Tooth size and morphology of anterior teeth influence inter-arch relationships. The Bolton analysis uses tooth width to calculate a sum of mandibular to maxillary tooth widths ratio necessary for proper occlusion. Several parameters not factored in the Bolton analysis influence occlusion such as tooth thickness. This study sought to use 3D modeling to develop and assess a tooth size analysis that encompasses labio-lingual thickness as well as mesio-distal width of anterior teeth.

Methods: The role of tooth thickness in inter-arch relationships was studied using simulations in a 3D modeling software (SuresmileTM). To develop a new chart of inter-arch ratios based on tooth thickness, a series of simulations were produced with varying tooth thicknesses and widths. The new ratios were evaluated on records from 50 patients.

Results: Findings from the simulations suggest that the ideal tooth thickness remains approximately 2mm if the overall tooth width of the dentition increases and the inter-arch anterior ratio is maintained. The thickness-adjusted anterior mandibular to maxillary tooth ratio ranges from 0.70 to 0.79 depending on the tooth thickness. This thickness-adjusted ratio provides a superior prediction for the sum of anterior tooth width compared to the Bolton analysis.

Conclusions: Tooth thickness does affect inter-arch tooth width ratios and anterior occlusion. A thickness-adjusted ratio can be used to more accurately predict anterior tooth dimensions necessary to achieve proper occlusion.

Bio: Yelena is originally from Ukraine, and moved to the states at a young age. She grew up in Bellevue, Washington and completed her undergraduate education in Biology at the University of Washington. She then moved to sunny Los Angeles to attend the University of California, Los Angeles for her dental degree, where she met her husband, Leo. Keeping up the Team 1 tradition, she got married in the first year of her orthodontic residency program. Yelena is immensely fortunate to have had the opportunity to return home to the Pacific Northwest to pursue orthodontics at the University of Washington. She is forever grateful to the wonderful faculty for sharing their experience, and for their endless support. She would especially like to thank her loving family and husband, who have been by her side through this journey. Three years have flown by, and she will miss the UW Ortho family. Yelena is looking forward to staying in Seattle after graduation and starting her orthodontic career.

Evaluating Changes in the Inter-Occlusal Space During Orthodontic Retention Stage

Veronica M. Toro
Chair of the Supervisor Committee:
Anne-Marie Bollen, Professor and Program Director
Department of Orthodontics

Introduction: This study measured post-treatment changes in the inter-occlusal space one month and three months after comprehensive orthodontic treatment: “settling”, using 3D images. The effects of patients’ demographics and retention were analyzed.

Methods: Intraoral scans were taken at debond, 1-month and 3-months retainer checks for 90 consecutively finished patients. A heat map was created with a 3D Software to measure the inter-occlusal changes. The changes in the total surface area in range, anterior and posterior areas, retainer type (occlusal coverage or not), age, and gender were compared.

Results: The Total Surface Area in range increased the first month (p<0.001) and from 1 month to 3 months (p>0.05). Anterior and posterior teeth experience changes in the inter-occlusal space during the 3-month period. There was an increase in occlusal contacts for patients wearing retainers without occlusal coverage. There was no influence of gender or age.

Conclusions: During the first month after the removal of orthodontic appliances, there is an increase in total surface area in range. The contact surface area of teeth within the -2mm to 0.25mm range of distance between the upper and lower teeth remains constant. Retainers without occlusal coverage allow changes in the inter-occlusal space.

Bio: Veronica was born and raised in San Juan, Puerto Rico with her parents and big sister. Since she was a little girl, she had two passions: dogs (passion she got from her Mom), and straight teeth (which she definitely inherited from her Grandfather and Dad). Following in her Dad’s footsteps, she decided to become an Orthodontist. Veronica completed Dental School at the University of Puerto Rico School of Dental Medicine. In 2014, she was fortunate to join an amazing group of residents at the University of Washington for her Orthodontics Residency. She is grateful for the constant support, encouragement, education, and guidance the UW Ortho family gave her the past 3 years. Veronica is also very thankful for her family; it has been a very long journey, and she could not have done it without their support. Lastly, she would like to thank her Team 5 for all the support and tell them: “Guys, there is no team like ours! Let’s continue being awesome.”

Characterizing the appearance of ex vivo remineralized white spot lesions with a novel peptide

Sherwin Habibi

Background: White spot lesions (WSLs) are unfortunate post-orthodontic sequelae that compromise the final esthetics of treatment, can result in caries, and can persist indefinitely. Current methods to treat WSLs may promote remineralization, but have not demonstrated consistent improvement with respect to the appearance of the lesion.

Purpose: This study explores the remineralizing potential of a novel peptide, amelogenin-derived peptide 5 (ADP5), in comparison with MI Paste Plus (MIPP) and topical fluoride treatment.

Methods: Artificial WSL lesions were created on ex vivo human molars. Teeth were sectioned into samples and randomly assigned to 1 of 4 arms: (1) a daily regimen of ADP5 solution, (2) a daily regimen of MIPP, (3) a daily regimen of 20,000 ppm fluoride solution, and (4) incubation in an artificial saliva control. Samples were treated for a period of 2 weeks. Photographs were taken prior to and after treatment. Two panels comprising 5 dental professionals and 5 laypersons assessed before-and-after pairs of photographs in a blinded fashion. Scanning electron microscopy was performed on most samples after treatment to assess the subsurface lesion microstructure and the effects of treatment.

Results: After creating WSLs, 11 of these were assigned to the ADP5 group, 12 to the MIPP group, 12 to the fluoride group, and 10 to the control group. The mean improvements assessed by the expert panel were 16%, 16%, 15%, and 8% in the ADP5, MIPP, fluoride solution, and control groups, respectively. The mean improvements assessed by the lay panel were 16%, 13%, 16%, and 8%, respectively. Single factor ANOVA revealed no difference in the amount of improvement across the 4 study groups. SEM images were qualitatively assessed. Samples treated with ADP5 showed an appositional layer of approximately 5 m and a subsurface remineralization depth of 25 m. Control samples did not appear to display any apposition or any remineralization. MIPP and fluoride samples were more variable in their presentation, with subsurface remineralization depths ranging from 0 to 25 m in both groups.

Conclusions: Treatment of WSLs with ADP5 did not produce a significantly greater visual improvement when compared to the other treatment groups or the control over the 2-week period. SEM imaging revealed a more consistently achieved penetrative remineralization in ADP5 groups compared to MIPP and fluoride groups, as well as a thin appositional layer that was often present.

Bio: While Sherwin was born in Halifax, Nova Scotia, his family soon after moved to Ottawa, the beautiful capital city of Canada. There, he went through his formative years, instructed martial arts, and completed his undergraduate degree in Biology at Carleton University. Upon graduation, Sherwin was awarded the Governor General’s Academic Medal for the highest academic standing amongst his peers. He then set out for dental school at the University of Toronto, where he enjoyed immersing himself in all that the program and city had to offer. While in dental school, he developed an interest in orthodontics, and was ecstatic to be accepted to UW Orthodontics.

Calling the faculty by their first names was an uneasy adjustment at first, but Sherwin quickly learned that it reflected the department’s collegiality and warmth. Sherwin feels privileged and extremely proud to have been given the opportunity to complete his orthodontic residency here and to be in such a wonderful environment of excellence and encouragement by its incredible faculty, administration, and support staff. He strongly believes in the noble station of teachers, and hopes to, in some capacity, teach up-and-coming generations of students himself in the future. Sherwin treasures the friendships that he has developed here at UW and is looking forward to continuing them as he moves forward in his career.

Sherwin plans to return home to Canada to practice, where he is excited to enhance the smiles and confidence of his patients. He will continue with his other passions of snowboarding, directing and editing videos, and beatboxing!

3-D Comparison of the shape and position of the condyle before and after Class II correction

Sepideh Torkan

Purpose: The aims of this study were to assess the changes in the shape and position of the condyle in the fossa as well as its position relative to the cranial base before and after Class II correction with the Herbst appliance (HA) or headgear (HG), and to also compare any changes to matched Class I cases.

Methods: Patients were divided into four groups, Class II treated with HA and their matched Class I cases, as well Class II cases treated with HG and their matched Class I cases. CBCTs were obtained before and after treatment in all cases. A total of 122 condyles (left and right) from 61 patients were assessed. 242 landmarks were identified on the condyle and fossa, from which 3-D surface meshes were created. 7 relatively stable landmarks were recorded on the skull to assess the position of the condyle relative to cranial base. Length of the mandible was measured on laterals cephalograms rendered from CBCTs. Principal component, generalized Procrustes, and discriminant function analyses were used to assess shape and position changes.

Results: There were no significant changes in the position of the condyle relative to the cranial base before and after treatment. No significant differences were reported in the anteropostserior or vertical position of the condyle relative to the fossa (P=0.71 and P=079 respectively). There were significant changes in the shape of the condyles when Class II untreated cases were compared to controls. Untreated Class II cases had more internal rotation of the mediolateral long axis of the condyles when compared to Class I cases. There were no significant differences in changes in the length of the mandible between Class II and control cases.

Conclusions: The condyles of all untreated patients, whether they were Class I or Class II initially, did not change their position (within the fossa or relative to stable cranial base structures) when assessed at the end of orthodontic treatment.

Bio: Sepi grew up in Iran with her parents and her older brother and sister. She completed dental school in her hometown where she met her husband, Navid. Sepi became increasingly fascinated by orthodontics during her time in dental school. She started a 4-year orthodontics residency right after finishing dental school and worked as an orthodontist for 8 months before deciding to start a new journey and move to the United States. She was very fortunate to get into the school of her dreams; the University of Washington has given rise to a great number of her orthodontic idols. After two residencies and two countries, she is very excited for the next chapter of her life and is looking forward to starting a career as an orthodontist in Seattle where she now calls home. Sepi is proud to finally be in the ranks of UW alumni and is grateful for all the valuable lessons she has learned from her faculty. She would like to thank her husband, Navid, for his unwavering support and unconditional love. This day would not have come without him!

Mouthguards During Orthodontic Treatment: Perspectives of Orthodontists and a Survey of Orthodontic Patients Playing School-Sanctioned Basketball and Football

Neal Bastian 

Purpose: This study’s objectives were to: 1) examine the beliefs and practices of orthodontists about mouthguard use in orthodontic patients, and 2) survey orthodontic patients currently playing school-sanctioned basketball and/or football about mouthguards.

Methods: Fifteen orthodontists were interviewed about mouthguard use in their patients. Patients from 13 of the offices participated in an online survey about mouthguards. Orthodontic patients (11-18 years old) playing organized school basketball (N=53) and/or football (N=22) completed the survey.

Results: Approximately half of the orthodontists surveyed initiated a discussion about mouthguards with their patients. The boil-and-bite type mouthguard was most commonly recommended by the orthodontists. All football players reported using a mouthguard, as mandated by this sport. Basketball does not mandate mouthguard use and only 38% of basketball players reported wearing one. Mouthguard users most commonly reported having a stock type [football (59%), basketball (50%)]. Players who used mouthguards cited forgetting as the most frequent reason for not always using one. Basketball players who never wore a mouthguard reported that hardly anyone on their team wears one (77%), that it might make it hard to breathe or talk (74%), and that they never thought about wearing one (68%). A greater proportion of football (87%) than basketball (32%) players reported that their coach recommended a mouthguard (p<0.0001).

Conclusions: Orthodontists differ in how they approach mouthguard use by their patients, which likely reflects a lack of evidence-based guidelines. The beliefs, recommendations and practices of orthodontists concerning mouthguard use are discussed. Research directions to improve mouthguard use are suggested.

Bio: Neal was born and raised in Mill Creek, Washington.  He received a Bachelor of Science in Exercise Science from Brigham Young University.  He served a mission for his church in Manila, Philippines and is fluent in Tagalog.  After several years away from home, Neal was grateful to return to Seattle to attend dental school at the University of Washington.  Over the last 7 years at UW, Neal and his wife Michelle have seen their family grow from 1 child to adding two children during dental school and now one more on the way!  Neal would like to share his appreciation for his wife for all of her sacrifices and service.  The Bastian family is thrilled to again call Mill Creek home where Neal will be joining Sullivan Orthodontics, in private practice.

Management of overbite with clear aligners

Roozbeh Khosravi

Purpose: Most of the published literature on the management of overbite with the Invisalign® appliance consists of case reports or case-series. This retrospective study of 120 patients sought to assess the nature of overbite changes with the Invisalign® appliance.

Methods: Records were collected from three practitioners, all experienced with the Invisalign® technique. The patients were consecutively treated adults (>18-years-old) who underwent orthodontic treatment only with the Invisalign® appliance. Patients with major transverse or antero-posterior changes or extraction treatment plans were excluded. The study sample included 68 normal overbites, 40 deepbites, and 12 openbites. The median age was 33 years and 70% of the patients were female.

Results: Cephalometric analyses indicated that the deepbite patients had a median overbite opening of 1.5 mm, while the openbite patients had a median deepening of 1.5 mm. The median change for the normal overbite patients was 0.3 mm. Changes in incisor position were responsible for most of the improvement in the deepbite and openbite groups. Minimal changes in molar vertical position and mandibular plane angle were noted.

Conclusion: The Invisalign® appliance appears to manage the vertical dimension relatively well, and the primary mechanism is via incisor movements.

Does initial malocclusion predict the outcome of orthodontic treatment?

Keyvan Sohrabi

Introduction: The assessment of orthodontic treatment outcomes and clinical performance are important goals in orthodontics. This study assessed the improvement of malocclusion in patients treated in University of Washington Graduate Orthodontic Clinic. The relationships between initial severity of the malocclusion, duration of treatment, and final treatment outcomes were also determined.

Methods: Patients who completed treatment during years 2012-2013 were included in this study. Exclusion criteria included complex multidisciplinary patients, phase 1 treatment procedures, and patients with craniofacial problems. PAR index scoring was performed on initial and final models and ABO Cast-Radiographic evaluation on final records. Patient data collected included treatment duration, Angle classification, type of appliances used, treatment strategy, and cephalometric analysis. Data were analyzed with t-test, ANOVA, and multiple linear regression models.

Results: Records from 102 different patients were included in this study. The mean age ± SD of subjects was 16.4 yrs ±9.9 mos. The following types of malocclusion were included: 43% Class I, 33% Class II, and 24% Class III. Average treatment duration for these patients was 23.2 ±5.5 months. Results showed an overall 80 ±23% improvement in PAR. Of all patients treated, 48% were greatly improved, 46% improved, and 6% of the patients did not improve. The analysis showed that the average ABO score for patients after completion of treatment was 19.5 ±8.8. The ABO component garnering the greatest points was occlusal relationship (3.8 ±2.9) and lowest scoring area was found to be interproximal contacts (0.5±1.2). A positive and significant (P<0.0001) relationship was found between initial and final PAR score and the ABO score. A trend was noted for the lower mean final PAR and ABO scores in the extraction group, but this difference between extraction and non-extraction treatments did not reach statistical significance. The mean ABO score for Class I patients was the lowest compared to other categories. The regression model indicated that the initial PAR score and duration of treatment were associated with the ABO score however, age, ANB and SN-MP were not significantly associated with the outcome of treatment.

Conclusion: The majority of patients were treated satisfactorily in the graduate orthodontic clinic. Initial severity of patients and duration of treatment were significantly associated with for the final outcome of treatment.

Assessing the feasibility of yttria-stabilized zirconia in novel designs as mandibular anterior fixed lingual retention following orthodontic treatment.

Matthew Stout

Purpose: To explore the feasibility of yttria-stabilized zirconia (Y-TZP) in fixed lingual retention as an alternative to stainless steel.

Methods: Exploratory Y-TZP specimens were milled to establish design parameters. Next, specimens were milled according to ASTM standard C1161-13 and subjected to four-point flexural test to determine materials properties. Finite Element (FE) Analysis was employed to evaluate nine novel cross-sectional designs and compared to stainless steel wire. Each design was analyzed under the loading conditions to determine von Mises and bond stress. The most promising design was fabricated to assess accuracy and precision of current CAD/CAM milling technology.

Results: The superior design had a 1.0 x 0.5 mm semi-elliptical cross section and was shown to be fabricated reliably. Overall, the milling indicated a maximum percent standard deviation of 9.3 and maximum percent error of 13.5 with a cost of $30 per specimen.

Conclusions: Y-TZP can be reliably milled to dimensions comparable to currently available metallic retainer wires. Further research is necessary to determine the success of bonding protocol and clinical longevity of Y-TZP fixed retainers. Advanced technology is necessary to connect the intraoral scan to an aesthetic and patient-specific Y-TZP fixed retainer.


Cephalometric Analysis and Long-Term Outcomes of Surgical Jaw Advancement in Obstructive Sleep Apnea


Purpose: To describe the posterior airway space and soft tissue changes in patients who received orthodontics and single or dual surgical jaw advancement and to evaluate if there is a correlation between increasing amounts of advancement and long-term reduction in obstructive sleep apnea.

Methods: Records were searched from one oral surgeon and one orthodontist for all patients treated by bilateral sagittal split osteotomy (BSSO) or maxillomandibular advancement (MMA) done in combination with orthodontics. Cephalometric films from pre-treatment, pre-surgery, post-surgery, and final removal of appliances were collected and traced.  Pre-surgical and Post-surgical polysomnography results were collected, specifically the apnea-hypopnea indexes (AHI). The patients were recruited to complete a questionnaire and Epworth Sleepiness Scale (ESS) to assess long-term outcomes from treatment. Descriptive statistics were calculated for all cephalometric measurements and the data was analyzed for change from initial to final measurements with significance level set at P < .05. Linear regressions were performed to find estimates for the final OSA outcomes (AHI and ESS) as a function of mandibular advancement.

Results: Forty-three patients, treated from 1995-2010, were identified for the study. Twenty-nine patients had a complete cephalometric film series. The maxilla and mandible were advanced 5.2 mm and 8.3 mm respectively, with a mean 4 mm increase in posterior airway space. The upper and lower lip protrusion increased by 4.8 mm and 7.6 mm but there was no significant change in relation to the nose-chin line. The soft tissue chin increased by 11.3 mm. Thirty-three patients completed the long-term survey at a mean 6.3 years ± 2.6 (range 2-12 years) after removal of appliances. The majority of patients (90%) reported reduction of their OSA symptoms and were pleased with their facial appearance. 79% of patients would recommend the orthodontic and surgical management of OSA to prospective candidates. 22 patients had initial AHI and final ESS values to assess final ESS score as a function of mandibular advancement. The mandibular advancement regression coefficient was -0.03 statistically and clinically insignificant. Twelve patients had initial and final AHI values to assess final AHI value as a function of mandibular advancement. The regression coefficient of mandibular advancement was 0.05, also statistically and clinically insignificant. No correlation could be found due to the lack of variation of mandibular advancement and limited sample size.

Conclusions: Soft tissue profile characteristics, AP airway dimensions, and skeletal maxillomandibular advancement were significantly increased after MMA. Soft tissue parameters were considerably protrusive but still demonstrate facial harmony. There was no evidence of a linear relationship between greater amounts of mandibular advancement and improvement of OSA outcomes. An advancement threshold could not be evaluated due to the limited sample size. Patients well below the recommended 10 mm advancement had successful objective short-term and subjective long-term reduction in OSA symptoms. Overall, patients were satisfied with their OSA management, facial aesthetics, and would recommend the treatment to others.

Characteristics and Fate of Orthodontic Articles Submitted for publication: An exploratory study of the American Journal of Orthodontics and Dentofacial Orthopedics

Nadia Farjo DMD

Purpose: The orthodontic literature lacks any study that investigates the characteristics and fate of manuscripts submitted to a top journal, such as the American Journal of Orthodontics and Dentofacial Orthopedics (AJO-DO). Having such information could be valuable to authors and editors alike in understanding critical aspects of the review process.

Methods: This exploratory study looked at original articles submitted to the AJO-DO in 2008 and gathered the following information: (1) For rejected articles: main reason for rejection, publication elsewhere, and journal of subsequent publication where applicable; (2) For accepted articles: number/type of revisions and time elapsed to publication; (3) For all articles: study topic, study design, area of origin, and presence of statistically significant findings. Descriptive statistics were used to describe the manuscripts in terms of the above characteristics. Interactions between the above characteristics and rejection/acceptance/publication elsewhere were explored and reported using the Chi-squared test for equality of proportions, with Fisher’s exact test used for samples of five and below. Post-hoc pairwise tests were checked against the Bonferroni correction to account for multiple testing.

Results: Of the 440 original articles submitted to the AJO-DO in 2008, 113 (25.9%) were accepted for publication while 323 (74.1%) were rejected. All accepted articles underwent either major or minor revision before acceptance and were published in an average of 20.9 months (sd=4.9) after acceptance. Of the rejected articles, 137 were subsequently published in 58 different journals with an average time to publication of 22.2 months (sd=10.9) after rejection from AJO-DO. Among articles not accepted by AJO-DO, the top three reasons for rejection were: (1) Poor study design/small sample size (59% of rejected papers); (2) Outdated/Unoriginal topic (41.5%); and (3) Inappropriate for AJO-DO audience (27.2%). Manuscripts rejected for poor study design had the least success in subsequent publication, while those rejected as inappropriate for the AJO-DO had the highest rate of publication elsewhere. Neither study topic nor study design were significantly associated with acceptance to AJO-DO or publication elsewhere except among rejected observational studies, where it was found that cross-sectional studies were most likely to be published elsewhere, and case series had the least success (p=0.002). Area of origin was found to be significantly associated with acceptance to AJO-DO, with articles from USA and Canada most likely to be accepted (p<5×109). An inverse relationship was seen for publication of rejected articles in other journals, where countries with the least publishing success with AJO-DO had the highest rate of publication elsewhere. The presence of statistically significant findings was shown to be significantly associated with acceptance to AJO-DO (p=0.013) but not with publication elsewhere (p=0.77).

Conclusions: Rejection by AJO-DO does not preclude publication elsewhere. Geographic origin is a predictor of acceptance to AJO-DO as well as subsequent journals. Authors aiming to maximize their chance of article acceptance should submit to an appropriate journal, use a well-designed and described study with adequate sample sizes, and emphasize the novelty and relevance of their work.