Comparison of the effects of different rapid maxillary expansion techniques on craniofacial structures: a finite element analysis study.

AIM: To compare the effects of three different maxillary expansion appliances with five different types of expansion modalities on stress distribution and displacement on the maxilla and its adjacent craniofacial structures using the finite element method (FEM). MATERIALS AND METHODS: Cone-beam computed tomography data of a patient with maxillary transverse deficiency were rendered into a three-dimensional model of craniomaxillary structures. The expansion appliances included tooth-borne, hybrid, and bone-borne expanders. Five different expansion modalities were applied to each expander [conventional Rapid Maxillary Expansion (RME) (type 1), midpalatal suture cortico-puncture-assisted RME (type 2), LeFort l cortico-puncture-assisted RME (type 3), surgically assisted RME (SARME) without pterygomaxillary junction (PMJ) separation (type 4), and SARME with bilateral PMJ separation (type 5)]. The numerical and visual data were analyzed. RESULTS: The highest amount of stress accumulation on teeth was found in the tooth-borne and hybrid groups. On the other hand, more stress concentration on the maxilla was observed in the bone-borne group. SARME cuts with PMJ separation increased total movement by reducing the stress on the midpalatal suture in all groups. While types 1, 2, and 3 were similar in terms of the amounts of displacement, types 4 and 5 increased the total amount of displacement in all groups. The total amounts of displacements from the highest value to the lowest value for the anterior and posterior maxilla were in the bone-borne, tooth-borne, and hybrid groups. CONCLUSIONS: SARME cuts were effective in reducing stress on the teeth, but the cortico-puncture application affected neither the stress values on the teeth nor the transverse displacement in the tooth-borne expanders. Surgical procedures such as SARME and corticotomy should be used with bone-borne devices to improve the outcomes of maxillary expansion procedures.

Apical Root Resorption of Endodontically Treated Teeth after Orthodontic Treatment: A Split-mouth Study.

Objective: The influence of pulp status on orthodontically induced root resorption has attracted attention. The purpose of this study was to compare orthodontically induced root resorption in endodontically treated teeth and their contralateral vital teeth in a split-mouth design. Methods: The sample included 173 patients who had at least one endodontically treated tooth, and their vital contralateral teeth served as the control group before the completion of orthodontic treatment. Apical root resorption measurements were performed by the comparison of digital panoramic X-ray images obtained at the beginning and at the end of the orthodontic treatment. Kruskal-Wallis, Mann-Whitney U, and Wilcoxon tests were used for statistical analysis. Results: There was no statistically significant difference in apical root resorption between the endodontically treated teeth and the contralateral teeth (p>0.05). Sex and tooth type had no effect on apical root resorption both in the endodontically treated teeth and the contralateral vital teeth (p>0.05). Orthodontic treatment with extraction caused more apical root resorption in the vital teeth than in the endodontically treated teeth (p<0.05). The quality of the endodontic treatment had no significant influence on apical root resorption (p>0.05). Conclusion: Endodontic treatment does not produce greater apical root resorption compared with the vital teeth.