A finite element analysis of the effects of different skeletal protraction and expansion methods used in class III malocclusion treatment

This study aims to carry out an in-silico examination of the different skeletal advancement methods used in the treatment of maxillary retrusion patients. Computed tomography images of a young adolescent patient with maxillary retrusion were processed using three-dimensional medical image processing software to obtain a patient-specific model. Three different treatment scenarios were envisaged for the finite element analysis. In the first scenario, rapid maxillary expansion (RME) and face mask (FM); in the second, bone-assisted maxillary advancement and RME, and in the third, hybrid hyrax+mentoplate combination method were used. The hyrax screw was activated by 0.25mm in each model, with a force of 500g in the first scenario and 250g in the second and third scenario for each side. Von Mises stresses and the initial displacements were evaluated when different maxillary protraction methods were applied. We found that similar stress distributions were observed in the skull where the methods of RME/FM model and bone-assisted maxillary advancement were used. These stresses were higher than the hybrid hyrax+mentoplate combination method. When the displacement values were compared, anterior movement was found in the maxilla in the bone-supported model to include the middle face, while maxillary anterior movement of maxilla was detected on the Le Fort 1 level with the hybrid hyrax+mentoplate combination method. Dentoalveolar anterior movement was detected in the RME/FM model. Given the obtained stress distributions and displacement values, it has been observed that the bone-assisted maxillary advancement method provides more skeletal efficiency than the RME/FM and the hybrid hyrax+mentoplate combination methods. [Med-Science 2018; 7(4.000): 898-904

Histomorphometric Evaluation of the Effects of Various Diode Lasers and Force Levels on Orthodontic Mini Screw Stability

Objective: The purpose of this study was to evaluate the effects of different laser dose and force levels on the stability of orthodontic mini screws used for anchorage, by histomorphometric analyses. Background data: Low-level laser therapy speeds up blood flow, improves the mechanism of the revitalization processes, reduces the risk of infection, boosts metabolic activities, and accelerates the healing of the damaged tissue. Although there are many research studies about low-level laser therapy applications in a variety of areas, no investigations were found concerning mini screw stability using various laser dose levels with different force level applications. Methods: Seventeen New Zealand white rabbits were used. A total of 68 cylindrical, self-drilling orthodontic mini screws were threaded at the fibula. Experimental subjects were divided into six groups; force application was not performed in the first three groups, whereas 150g of force was applied via nickel-titanium closed-coil springs placed between two mini screws in the other three groups. Measurements of the initial torque values (10 Ncm) were manipulated by a digital portable torque gauge. Various low-level laser doses were applied to the groups during the postoperative 10 days. After 4 weeks, bone-to-implant contact and cortical bone thickness were histomorphometrically analyzed. Results: In the 150g force plus 20 J/cm(2) dosage group, the highest bone-to-implant contact values were observed. (p<0.05) There were no statistically significant correlations between cortical bone thickness and bone-to-implant contact values; on the other hand, no significant difference was found among the same groups in terms of cortical bone thickness values (p>0.05). Conclusions: Low-level laser therapy was noticed to induce the mini screw-bone contact area. Low-level laser therapy may be a supplementary treatment method to increase the stability of the orthodontic mini screw