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.


Photos of Moore Thesis Day 2016