Deep learning for virtual orthodontic bracket removal: tool establishment and application.

OBJECTIVE: We aimed to develop a tool for virtual orthodontic bracket removal based on deep learning algorithms for feature extraction from bonded teeth and to demonstrate its application in a bracket position assessment scenario. MATERIALS AND METHODS: Our segmentation network for virtual bracket removal was trained using dataset A, containing 978 bonded teeth, 20 original teeth, and 20 brackets generated by scanners. The accuracy and segmentation time of the network were tested by dataset B, which included an additional 118 bonded teeth without knowing the original tooth morphology. This tool was then applied for bracket position assessment. The clinical crown center, bracket center, and orientations of separated teeth and brackets were extracted for analyzing the linear distribution and angular deviation of bonded brackets. RESULTS: This tool performed virtual bracket removal in 2.9 ms per tooth with accuracies of 98.93% and 97.42% (P < 0.01) in datasets A and B, respectively. The tooth surface and bracket characteristics were extracted and used to evaluate the results of manually bonded brackets by 49 orthodontists. Personal preferences for bracket angulation and bracket distribution were displayed graphically and tabularly. CONCLUSIONS: The tool's efficiency and precision are satisfactory, and it can be operated without original tooth data. It can be used to display the bonding deviation in the bracket position assessment scenario. CLINICAL SIGNIFICANCE: With the aid of this tool, unnecessary bracket removal can be avoided when evaluating bracket positions and modifying treatment plans. It has the potential to produce retainers and orthodontic devices prior to tooth debonding.

The effect of tooth morphology and vertical bracket positioning on resultant stress in periodontal ligament - a three dimensional finite element study.

INTRODUCTION: The purpose of this study is to evaluate the effect of change in vertical placement of bracket and effect of tooth morphology on stress developed on periodontal ligament with the help of three dimensional finite element modeling. METHODS: A three-dimensional model of the maxillary bone, maxillary right central incisor, lateral incisor and canine was designed based on the average dimensions of the anatomy and morphology given by Wheeler's and standard edgewise bracket with Slot of 0.022″ X 0.028″ inch was designed using the finite element method. Brackets were placed on each tooth, on the mentioned labial surface at variable distances from the cusp tip, and a full size archwire was virtually engaged into the bracket, then optimum orthodontic load of 2N is applied and PDL stress were calculated. RESULTS: The lowest stress values were measured as bracket position changes from crest of teeth to the apical direction. By displacing the bracket gingivally from 1.5 to 6 mm, a 16.2% decrease in stress level for central incisor, for lateral incisor the stress level decrease by 25.8% and for canine the stress level decrease by 21.6% thus our study confirms that variation in vertical bracket position results in change in resultant stress in PDL. CONCLUSION: It can be concluded that the variation in the vertical position of the bracket osn different tooth can have an important effect on the stresses developed in the PDL.

Coordinating bracket torque and incisor inclination : Part 2: Reproducibility and statistical measures of the torque coordination angle (TCA).

PURPOSE: To determine the reproducibility and statistical measures of the torque coordination angle (TCA). METHODS: A total of 107 final cephalograms and corresponding casts were included, all reflecting treatment outcomes that met high qualitative standards, one of them being a Peer Assessment Rating (PAR) score of ≤3. Based on these records, the TCA was measured as a parameter to identify differences related to tooth morphology and bracket position between the torque-relevant reference plane at the bracket base and the long axis of a tooth. All measurements were performed on upper and lower central incisors (U1 and L1). RESULTS: Several reproducibility assessments for the TCA measurements yielded good results, including objectivity at 1.26 ± 0.81° (U1) or 1.41 ± 1.18° (L1), examiner reliability at 1.30 ± 0.97° (U1) or 1.25 ± 0.82° (L1), and method reliability at 1.80 ± 1.13° (U1) or 1.53 ± 1.07° (L1). The statistical measures revealed a high degree of interindividual variability. With bracket placement 4.5 mm (U1) or 4.0 mm (L1) above the incisal edge, the differences between the maximum and minimum TCA values were similarly large in both jaws (21.0° for U1 or 20.0° for L1), given mean TCA values of 24.6 ± 3.6° (U1) or 22.9 ± 4.3° (L1). Moving the bracket placement from 3.5 to 5.5 mm (U1) or from 3.0 to 5.0 mm (L1) changed the mean TCA values by 4.5° (U1) or 3.2° (L1). CONCLUSIONS: The TCA is a suitable cephalometric parameter to identify differences related to tooth morphology and bracket placement. Given its high interindividual variability, the fixed torque value of a specific bracket system should not be expected to produce the same incisor inclinations across patients.

Reliability of clinical crown center to predict marginal ridge leveling.

OBJECTIVE: To evaluate the null hypothesis that there is no difference between the vertical compensation necessary to level the clinical crown centers and that required to level the marginal ridges. MATERIALS AND METHODS: Initial dental casts selected from 200 patients that met the selection criteria were included. The vertical position of the clinical crown center (VPCC) and marginal ridge (VPMR) of posterior teeth were measured in both arches using a digital height gauge with 0.01mm precision. The vertical discrepancy between the clinical crown centers (VDCC) and marginal ridges (VDMR) of adjacent posterior teeth were calculated and compared. The significance level was set at P < .05. RESULTS: In general, vertical discrepancies between VDCC and VDMR were statistically significant (P < .05). Clinically significant differences were observed between the maxillary second premolar and first molar and between the mandibular molars. The VPCC was significantly and positively correlated with patient age. CONCLUSIONS: Differences between VDCC and VDMR showed that the VPCC may not be an accurate predictor of marginal ridge leveling because the vertical compensation necessary to level the VPCCs is not similar to that required to level the marginal ridges, requiring caution in its utilization, mainly in teenagers.

Colagem indireta: uma excelente alternativa para a técnica vestibular / Indirect bonding: an excellent alternative for vestibular technique

A etapa de colagem dos bráquetes é uma fase crítica no tratamento ortodôntico, cabendo exclusivamente ao profissional o correto posicionamento dessas peças. A técnica de colagem indireta vestibular pode auxiliar a colagem dos bráquetes, facilitando a visualização, fornecendo maior precisão e permitindo alcançar tratamentos com maior qualidade. O presente artigo tem como objetivo evidenciar a viabilidade da colagem indireta vestibular na clínica ortodôntica moderna, utilizando uma técnica simplificada (técnica 1) e uma convencional (técnica 2), determinando o tempo e o custo laboratorial de cada uma delas, e apresentando a aplicação clínica da mais viável à Ortodontia moderna. A técnica 1 teve custo e tempo laboratorial menores que a técnica 2. A técnica de colagem indireta representa um excelente recurso para a clínica ortodôntica moderna, cabendo ao cirurgião dentista despender de apenas alguns minutos para realizá-la.

Bracket bonding is a critical step of orthodontic treatment and the professional is the only responsible for the precise positioning of these parts. The indirect vestibular bonding technique can improve the bonding of the brackets, facilitating the visualization, providing high precision and enabling better treatments. The present article aimed to highlight the viability of indirect vestibular bonding in the modern orthodontic clinic, by using one simplified technique (technique 1) and a conventional (technique 2), determining the time and laboratorial cost of each of them, and presenting the most viable clinical application to the modern Orthodontic clinic. Technique 1 had lower laboratorial time and cost in cmparison to technique 2. The indirect bonding technique represents an excellent resource for the modern orthodontic clinic, requiring only a few minutes to be performed by the dental surgeon.

Three-dimensional finite element analysis of the bracket positioning plane in lingual orthodontics / 대한치과교정학회지

This study was performed to investigate the location of the ideal bracket positioning plane in lingual orthodontics using the three-dimensional finite element method. Displacement of the anterior teeth were evaluated according to the vertical and the angular movements of the bracket positioning plane. To achieve the ideal movement of anterior teeth in the lingual central plane, the location of the force application point and the amount of the moment applied to the four incisors were evaluated. As the bracket positioning plane was moved parallel toward the incisal edge, uncontrolled tipping and extrusion of the maxillary and the mandibular incisors were increased. But lingual tipping of the crown was decreased in the maxillary and the mandibular canines. As the bracket positioning plane was inclined toward the incisal edge, lingual tipping was increased in the 6 anterior teeth and extrusion of incisors and intrusion of the canine was also increased. As the retraction hook of the canine bracket was elongated, lingual tipping and extrusion of the central incisor and mesial movement and extrusion of the lateral incisor were increased. In the canine, mesial and labial movements of the crown were increased. When the moment was applied to the 4 incisors of the maxillary and the mandibular arch in the lingual central plane, 280 gf-mm in the maxillary central incisor, 500 gf-mm in the maxillary lateral incisor, 170 gf-mm in the mandibular central incisor and 370 gf-mm in the mandibular lateral incisor produced bodily movement of the individual tooth.

Mandibular clinical arch forms in Koreans with normal occlusions / 대한치과교정학회지

The purpose of this study was to clarify morphologic characteristics between mandibular clinical arch forms in Koreans with normal occlusions. The study included data from 102 Koreans. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth based on mandibular tooth thickness data. Four linear and two proportional measurements were taken. The dental arches were classified into ovoid, square and tapered forms. The frequency distributions of the three mandibular arch form classifications were determined and compared between male and female subjects. No significant differences in arch form size were found between the sexes. However, there were a few differences in molar width. It was useful to classify mandibular clinical arch forms present in normal occlusion samples into ovoid, square and tapered categories. The frequency of the ovoid form was the highest, and that of the square form was the second highest. The tapered arch form was found in less than 10 percent of subjects. No significant differences in their frequency distributions and dimensions were shown between males and females.