Search

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.

Objective: The effects of unilateral increased occlusal vertical dimension (iOVD) on bilateral craniofacial, mandibular and alveolar development in growing rats were investigated via cone‐beam computed tomography (CBCT). The role of Wnt/β‐catenin signalling in this process was examined. Materials and Methods: Forty‐eight female Sprague–Dawley rats were randomly allocated into unilateral iOVD and sham groups. At 2, 4 and 8 weeks, the rats were scanned via CBCT to analyse cranial, maxillary, mandibular and dental morphology. Changes in temporomandibular joint (TMJ) cartilage histology and Wnt/β‐catenin signalling were assessed by histochemical and immunohistochemical staining and qRT–PCR. Results: Dorsal cephalograms revealed that the mandible in the iOVD group tilted approximately 4° to the right. Unilateral iOVD had little effect on cranial and maxillary growth but inhibited mandibular growth (mandibular length and ramal height), especially on the deviated side (DS). Moreover, unilateral iOVD increased the length of the lower incisors and decreased the height of the molars on the DS. Unilateral iOVD induced bilateral osteoarthritis‐like changes in the bilateral TMJ condylar cartilage and activated Wnt/β‐catenin signalling in the condylar cartilage, especially on the contralateral side (CLS). Conclusion: Occlusion with unilateral iOVD induced mandibular deviation, significantly inhibited mandibular growth and produced compensatory changes in the alveolar bone. In the iOVD group, the mandibular body length and ramal height were greater on the CLS than on the DS. Moreover, the greater β‐catenin protein expression in the TMJ condylar cartilage on the CLS than on the DS may account for the difference in asymmetrical mandibular development. [ABSTRACT FROM AUTHOR]