Bingshuang Zou

Objectives: Three-dimensional (3D) imaging is becoming more mainstream with advances in digital technology and reduction in cost. Two-dimensional (2D) imaging has been the standard in orthodontics but it would be beneficial to examine virtual 3D patients for diagnosis, treatment planning, and assessment of growth and treatment outcomes with no use of ionizing radiation. This study aimed to validate the Bellus Arc7 3D facial scanner and test a novel method for integrating intraoral scans with 3D facial images to create a virtual patient. Methods: Part I entailed validation of Bellus Arc7 using the conventional reference standard, the 3dMDface system. Three subjects were selected, and for each 4 images were taken on two occasions one week apart. Images were uploaded, superimposed, and a 3D heat map was generated for comparison using Geomagic Control X processing software. Part II compared a novel merging technique from 14 participants recruited from UBC Graduate Orthodontic Program. For each subject, 5 images were captured (two images using Trios intraoral scanner, one facial scan with Bellus Arc7, and two with Artec Space Spider). The intra-oral scan of the upper dentition and the Arc7 3D facial scans were merged via the transferring of the perioral scan to develop a virtual patient. The reference 3D virtual image from the alignment of the dental scan and Artec Space Spider facial scans was used for comparison. The surface-to-surface root mean square and point-to-point deviation values between the two meshes were analysed. Results: Part I showed the root mean square for Bellus Arc7 as compared to the reference 3dMD to be 1.16 ± 0.41 mm for all three subjects, which is clinically acceptable for soft tissue measurements. Part II showed that relative to the merged Artec Space Spider scans, the root mean square difference of the merged Arc7 scans was 1.52 ± 0.54 mm. For the point-to-point deviations in the dentition there was a relatively wide range of mean differences. Conclusions: The results indicated that creating a 3D patient by merging the dental scan with 3D facial images acquired with Bellus Arc7 is adequate quality for most clinical applications, albeit very technique sensitive.

View record

Objectives: Align Technology Inc introduced its mixed dentition clear aligners in 2018. Since the advent of Invisalign First System (IFS) is relatively new, not much data is available regarding its treatment efficacy and predictability of results. Knowing the success rate of different orthodontic treatment modalities and their limitations is critically important for the success of an orthodontistas a clinician and for patient welfare. The purpose of this study is to determine whether the final achieved tooth movements are coherent with clear aligner ClinCheck predictions in mixed dentition.Methods: This retrospective study consisted of 39 (20 females and 19 males) patients who were consecutively treated with IFS in their mixed dentitions. The mean age was 8.9 years and ranged from 6.9 to 11.2 years, with an average treatment time of 8 months. Pre-treatment, post-treatmentachieved, and post-treatment predicted digital models were superimposed. The predicted and achieved overjet, overbite, intercanine width, intermolar width, and three-dimensional (3D) tooth movements of upper first molars were measured. The differences between the achieved and the predicted tooth movement were tested with either paired t-test or Wilcoxon Signed Rank test.Results: The predicted values for the overbite, intercanine width, and intermolar width were significantly greater than achieved values (P .05). While, in terms of 3D angulation and translation tooth movements, the results showed no statistically significant difference.Conclusions: For treatment in mixed dentition with IFS, predictable outcomes are achieved for 3D tooth movements in maxillary first permanent molars and overjet, however overcorrection is recommended for overbite, intercanine and intermolar width.

View record

Introduction: Maxillary expansion is common in orthodontic practice and there are many different expansion protocols, including Alternating Rapid Maxillary Expansion and Constriction (Alt-RMEC). Objectives: to analyze the dentoalveolar, skeletal and circummaxillary sutural changes, using retrospective Cone Beam Computed Tomography (CBCT) records, to compare 2 different maxillary expansion protocols: conventional Rapid Maxillary Expansion (RME) and Alt-RMEC. Methods: Data was collected from 34 growing Class III (maxillary deficient) patients, aged between 7.2 – 12.5 years old, who were randomly 1:1 allocated to either treatment group. Pre-treatment (T0) and post-treatment (T1) CBCT records were used to measure dentoalveolar, skeletal and circummaxillary sutural variables. Cervical Vertebral Maturation Stage (CVMS) and Mid-Palatal Suture Density (MPSD) ratio were measured using pre-treatment CBCTs. Differences between the two protocols were analyzed using students’ t-tests and linear regression models. Results: both expansion protocols produced pyramidal expansion patterns, both anterior-posteriorly and inferior-superiorly, except at the anterior nasal level where Alt-RMEC resulted in parallel expansion. Alt-RMEC produced statistically and clinically significantly less amount of maxillary 1st molar tipping (P 0.05) and resulted in increased nasal aperture widening (P 0.05) as a result of distraction of multiple midline craniofacial sutures. Males had larger amounts of posterior and middle palatal basal width expansion than females, with sex accounting for 20.0% and 20.5% of treatment change variation. Increasing CVMS and females produced larger amounts of right nasomaxillary suture opening, with both explanatory variables accounting for 34.0% of the variation in treatment change. Age and MPSD ratio were not correlated with any dentoalveolar, skeletal or sutural treatment change. Conclusions: our study found that RME and Alt-RMEC resulted in similar transverse dentoalveolar and skeletal measurements in addition to circummaxillary sutural changes. Aside from Alt-RMEC causing less maxillary 1st molar tipping and increased widening of the nasal aperture, the complexities of the protocol may not justify its use over conventional maxillary expansion in terms of maxillary expansion only. One should continue to consider factors such as age and skeletal maturity, as assessed by CVMS, when considering maxillary expansion in an orthodontic patient.

View record