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Objective@#To analyze the impact of the activation mode on the results of space closure in the mandibular arch using a double keyhole loop (DKHL) with a typodont model and reverse engineering technique to provide guidance for clinical treatment. @*Methods@#Nine normal mandibular typodont models after leveling were randomly divided into 3 groups, which then underwent three types of DKHL activation for space closure. Each model was assessed at the initial stage and after the warm water bath, and the images were superimposed to measure the displacement of special crown and root mark points. All statistical analysis of the data was performed using SPSS 19.0@*Results@# After equal activation times, the root retraction of anterior teeth and the crown forward position of posterior teeth in groups activated at the distal loop (conditions 2 and 3) were much greater than those in the group activated horizontally (condition 1). Activation between mesial and distal loops (condition 3) induced significant anterior tooth intrusion, together with elongation and buccal inclination of posterior teeth. The displacement of mark points among the three conditions showed a statistically significant difference. @* Conclusion @# The movement of mandibular anterior and posterior teeth could be flexibly controlled through different DKHL activation modes, which should be chosen carefully according to individual conditions.
ABSTRACT
Background: All-ceramic crown (ACC) preparations are widely used in day-to-day dentalclinical practice. Objectives: This study aimed to evaluate all-ceramic crown preparationsperformed by pre-clinical dental students at the College of Dentistry, Jazan University inSaudi Arabia and to compare the quality of the preparations between male and female groups.Materials and Methods: A total of 95 ivory teeth were prepared by fourth-year dentalstudents (44 males, 51 females). The students prepared a maxillary right central incisor forACC after mounting in the Frasaco typodont arches. Two silicone putty indexes for maxillaryanterior were obtained that extended to cover one or two teeth on either side. The facial indexwas used to provide information about the facial reduction mesio-distally. Another index wasprepared by cutting the silicone in half along the faciolingual midline of the prepared tooth,providing us with incisal, buccal, palatal, and axial reductions, in addition to biplanereduction. The data were encoded into a Statistical Package for Social Sciences program andanalyzed accordingly using Chi-square test. Results: The preparations of ACC for maxillaryanterior teeth were acceptable, ranging within 60%-85% in all criteria, which includedstructural durability, retention, and resistance. The male group was more excellent in incisalreduction (41.0%), whereas the female group was more excellent in axial taper preparations(59.1%), resulting in significant differences between genders in this preparation criteria. Allgender groups showed acceptable tooth preparations in shoulder reductions and location offinish lines, ranging within 57%-89%. Conclusion: The preparations for ACC achieved bythese dental students were considered clinically acceptable. The students clearly understoodthe principles of crown preparation. However, they still require more practice in order tomaster the art of crown preparation.
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OBJECTIVE: To investigate how bracket slot size affects the direction of maxillary anterior tooth movement when en-masse retraction is performed in sliding mechanics using an induction-heating typodont simulation system. METHODS: An induction-heating typodont simulation system was designed based on the Calorific Machine system. The typodont included metal anterior and resin posterior teeth embedded in a sticky wax arch. Three bracket slot groups (0.018, 0.020, and 0.022 inch [in]) were tested. A retraction force of 250 g was applied in the posterior-superior direction. RESULTS: In the anteroposterior direction, the cusp tip of the canine in the 0.020-in slot group moved more distally than in the 0.018-in slot group. In the vertical direction, all six anterior teeth were intruded in the 0.018-in slot group and extruded in the 0.020- and 0.022-in slot groups. The lateral incisor was significantly extruded in the 0.020- and 0.022-in slot groups. Significant differences in the crown linguoversion were found between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the central incisor and between the 0.018- and 0.022-in slot groups and 0.020- and 0.022-in slot groups for the canine. In the 0.018-in slot group, all anterior teeth showed crown mesial angulation. Significant differences were found between the 0.018- and 0.022-in slot groups for the lateral incisor and between the 0.018- and 0.020-in slot groups and 0.018- and 0.022-in slot groups for the canine. CONCLUSIONS: Use of 0.018-in slot brackets was effective for preventing extrusion and crown linguoversion of anterior teeth in sliding mechanics.
Subject(s)
Crowns , Incisor , Mechanics , Tooth Movement Techniques , ToothABSTRACT
Objective To evaluate the effectiveness of Typodont-based table clinic competition (TCC) on undergraduate orthodontic education. Methods Students who have finished basic orthodon-tic courses made diagnosis,treatment strategy and performed orthodontic treatment for malocclusion cases on Typodonts. A self-design questionnaire was employed to investigate their perception to this pedagogy. Results The majority of participants(82.2%-92.9%) highly evaluated Typodont-based TCC. Conclu-sions Typodont-based TCC course is conducive to arousing students' study internets and to promoting association between theory and practice.