OHSU

Research: Class of 2012

Cardall, S.” Reproducibility and Validity of Tooth Measurements Made from a 3D Digital Model Scanner Compared to Plaster Models. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2012

ABSTRACT:

Introduction: Improvements in computer technology have led to advances in orthodontic diagnosis by allowing the creation, manipulation, and measurement of virtual dental models. The Ortho Insight 3D laser scanner software is unique in offering the ability to automatically measure tooth widths, rather than relying on manually identified tooth landmarks. The purpose of this study was to determine the reproducibility and validity of tooth width measurements made from virtual models using automatic and manual measurements relative to direct caliper measurements from plaster models.

Materials and Methods: Tooth widths and Bolton Discrepancy measurements were made from 48 models (24 maxillary, 24 mandibular) that were measured 5 times using each of the 3 methods. The effect of crowding was also investigated by selecting models having mild (0-4.5 mm), moderate (4.6-9 mm), or severe crowding (> 9 mm; n=16 of each). Descriptive statistics were calculated for each method and method error was determined by the Dahlberg formula.  Intra-rater and inter-rater reliability were evaluated using several statistical analyses, and results from the three measurement methods were analyzed using Analysis of Variance (ANOVA) and Bland-Altman plots. 

Results: Measurement standard deviations averaged 0.12 mm for automatic virtual models, 0.16 mm for manual virtual models and 0.20 mm for plaster models. Mean differences between methods were 0.04 mm for automatically-measured vs. manually-measured virtual models, 0.13 mm for automatically-measured virtual vs. plaster models, 0.17 mm for manually-measured virtual vs. plaster models. By tooth type, molar measurements had the highest variance (0.20 mm automatic, 0.24 mm manual, 0.33 mm plaster). The Bolton 6-6 measurements had the highest overall variance (0.59 mm automatic, 1.38 mm manual, 1.59 mm plaster). Intra-rater paired t-tests showed significant differences for 4 of 7 plaster model examiners, while method error was low for 6 of 7 plaster model examiners. Inter-rater paired t-tests showed significant differences for 5 of 7 plaster model examiners. Pearson correlation coefficients were >0.999 and concordance correlation coefficients were >0.998 for each method regardless of crowding. Repeated-measures ANOVA found no significant differences by measurement method, arch, and crowding group. 

Conclusion: Teeth measured automatically and manually from virtual models using the Ortho Insight 3D scanner were found to have similar clinical acceptability relative to each other and measurements made directly from plaster models.

Castilla, A. “Measurement and Comparison of Bracket Transfer Accuracy of 5 Different Indirect Bonding Techniques”. Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2012

ABSTRACT:

Introduction: The objective of this study was to measure and compare the bracket transfer accuracy of 5 different indirect bonding (IDB) techniques in 3 planes of space (mesio-distal, occluso-gingival, and facio-lingual).

Materials and Methods: Five IDB techniques were studied: DS (Quick IDBSTM), DVF (Sondhi technique), HVF (Moskowitz technique), PVSP (Kalange technique), and SVF (modified Thomas technique). Brackets were bonded on 25 identical stone models called working models. IDB trays were fabricated over these working models (n=5 for each IDB technique) and used to transfer the brackets to another set of 25 identical stone models called patient models. The mesio-distal (M-D), occluso-gingival (O-G), and facio-lingual (F-L) position of each bracket on both working and patient models was measured using digital photography (M-D and O-G) and digital calipers (F-L). Paired T-tests were performed to compare the working and patient model bracket positions. Analysis of Variance (ANOVA) was performed to compare the bracket transfer accuracy between the 5 IDB techniques for various groups of teeth, including the entire arch, separated by 3 directions.

Results: The DVF technique had the highest number of teeth (6), while the HVF technique had the lowest number of teeth (1) with statistically significant differences (P < .05) in bracket position between working and patient models. With the exception of tooth 21 (UL1) for the SVF technique, all statistically significant (P< .05) differences in bracket position were 0.26 mm or less and 81% of them were 0.15mm or less. When comparing the 5 different techniques for all teeth grouped, the bracket transfer accuracy was comparable for the DS, PVSP, and HVF techniques in all directions. However, both the DVF and SVF techniques were significantly (P < .05) less accurate in the O-G direction when comparing the accuracy for all teeth grouped, as well as when comparing the accuracy for anterior teeth only.  

Conclusion: When comparing the 5 different techniques with all teeth grouped, the bracket transfer accuracy was comparable for the DS, PVSP, and HVF techniques in each of the 3 directions. The DVF and SVF techniques were significantly less accurate than the other 3 techniques in O-G bracket transfer accuracy when comparing the techniques for all teeth combined, as well as for anterior teeth.

Senestraro,S. “Resin Infiltration of White Spot Lesions: A Randomized Prospective Clinical Trial”.  Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2012

ABSTRACT:

Introduction: The purpose of this randomized single-blind clinical trial was to assess the aesthetic improvement and changes in area of post-orthodontic white spot lesions (WSL) restored with resin infiltration.

Materials and Methods: A total of 20 post- orthodontic patients with WSL on maxillary anterior teeth were selected from the Oregon Health & Science University orthodontic clinic.  One tooth per patient was randomly assigned to the control group (n=20) and the remaining teeth assigned to the treatment group (n=46). Teeth in the treatment group were treated using a resin infiltration technique (ICON Etch; DMG America, Englewood, NJ). Photographic images of the teeth were made at the start of the treatment appointment (T1), at the end of the appointment (T2), and 8 weeks later (T3). Orthodontists blinded to treatment evaluated the photographs for POWSL changes T1 to T2 and T1 to T3 using a visual analog scale (VAS).  WSL area was measured at each time point using morphometric software. VAS and area measurement data was analyzed using ANOVA.

Results: The mean VAS ratings for teeth treated with resin infiltration were significantly greater than mean ratings for control teeth at T2 and T3 (p<0.001).  The mean WSL percent reduction for teeth treated with resin infiltration, 61.8% at T2 and 60.9% at T3 (p<0.001), were very highly significantly greater than mean percent reduction for control teeth (showed no change).

Conclusion: Resin infiltration significantly improves the clinical appearance and reduces the size of WSL formed during orthodontic treatment.

Wilson, D. “The Effect of Facial Attractiveness on Orthodontic Treatment Outcome”
Thesis submitted in partial fulfillment of M.S. in Orthodontics, Oregon Health & Science University, December 2012

ABSTRACT:

Introduction: Recent studies have documented the influence of patient appearance on medical treatment. We sought to investigate the influence of patient facial attractiveness on orthodontic treatment outcome. Additionally, we explored associations between facial attractiveness and patient age, gender, compliance, oral hygiene, case complexity, perceived case complexity, orthodontist satisfaction with treatment outcome, and treatment duration.

Materials and Methods: Treatment records from 45 Angle Class 1 orthodontic patients between 10 and 20 years of age, treated by 45 orthodontists (one patient/orthodontist) were obtained. Treating orthodontists were surveyed regarding complexity, compliance, and oral hygiene (1=routine/poor, 7=complex/excellent). Patients’ radiographs and models were assessed using the American Board of Orthodontics Discrepancy Index (DI) and Objective Grading System (OGS) where lower scores equal superior outcome. Thirty orthodontists rated treatment photographs for facial attractiveness using a Visual Attractiveness Scale (VAS) vis-à-vis same-gender reference photos. After calculating bivariate correlations between mean VAS attractiveness ratings, patient demographics, treatment-related variables and OGS scores, we used step-wise multiple regression analysis to determine if pre-treatment attractiveness predicted OGS outcome scores. Control variables included patient age, gender, hygiene and DI, which were selected a priori and entered first into the model.

Results: VAS scores were significantly associated with OGS scores (r= -0.45, p= .002).  In Step 1 of regression analysis, only hygiene was significant in predicting OGS score (B= -3.29, p= 0.005; R2= 0.244), however, adding pre-treatment VAS scores significantly improved prediction of OGS scores (R2 = 0.363, F-change p= 0.011; VAS b= -0.46, p= 0.011 and hygiene b= -3.01, p= 0.006). VAS scores were not significantly associated with treatment time, DI, perceived case complexity, compliance, hygiene, or satisfaction with treatment outcome.

Conclusion: These results suggest that orthodontic treatment outcome is significantly influenced by patient facial attractiveness, as well as patient home hygiene.