Preliminary study on positioning of Damon Q self-ligating brackets in a digital integration model / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study was performed to determine the feasibility of digital virtual positioning of braces in clinical applications.</p><p><b>METHODS</b>We determined the positions of brackets in 28 teeth of 15 cases according to positioning methods that use bracket height or root information. Final status was generated by OrthoRx software. Treatment results were assessed with American board of orthodontics objective grading system (ABO-OGS).</p><p><b>RESULTS</b>The deduction points in the marginal ridge height were significantly decreased after treatment using the two methods (P<0.05). However, no statistically significant difference was found in the deduction points in the marginal ridge height between the two methods (P>0.05). No improvement was found in the deduction points in root parallelism with both methods. No statistical significance was found in the deduction points in root parallelism before and after treatments using both methods. The deduction points in alignment and the three scoring components were significantly decreased after treatment using the two positioning methods. In addition, statistically significant differences were found in the deduction points in alignment between two methods (P<0.05).</p><p><b>CONCLUSION</b>By using OrthoRx software, we achieved effective therapeutic treatment in reconstructing three-dimensional digital modes using two different bracket-positioning methods. The positioning method that used root information is more accurate compared with the bracket height positioning method. This study provides an experimental basis for bracket accuracy in the mouth.</p>

Logistic regression model analysis on Bolton ratio of orthodontic extraction model / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to evaluate the role of Angle's class, overall ratio and anterior ratio in the creation of tooth size discrepancies, and to determine whether any tooth extraction combinations create more severe discrepancies.</p><p><b>METHODS</b>166 dental casts of orthodontic patients were selected randomly. These models were classified according to angle's criterion. Mesio-distal dimensions of mandibular and maxillary teeth were measured before treatment, and subjected to Bolton's analysis. Hypothetical tooth extraction by the following combinations: all the first premolars, all the second premolars, upper first and lower second premolars, and upper second and lower first premolars, was performed on each patient. The measurement results were again subjected to Bolton's analysis to see whether any tooth-size discrepancy had been created. The results were evaluated statistically by means of Logistic regression model.</p><p><b>RESULTS</b>Overall ratio, anterior ratio and extraction models affected mesio-distal tooth size ratio of both maxillary and mandibular teeth in the final stage of orthodontic treatment, Whereas, the results showed no significant difference among these groups of malocclusion.</p><p><b>CONCLUSION</b>The results suggested that dentists should always keep in mind that each patient should be treated individually and should be aware of that other factors also played important roles in determining what teeth, if any, should be removed and the Bolton analyses of all kinds of extraction models should be carried out, as well as the general Bolton analysis.</p>

Hyoid bone position in patients with Angle Class Ⅰ or Class Ⅲ malocclusions and early permenent dentition / 实用口腔医学杂志

Objective:To investigate the hyoid bone position on the cephalometric radiographs of patients with early permenant dentitions and Class I or Class Ⅲ malocclusion.Methods:The cephalometric radiographs were taken in centric occlusion and 16 measures were performed on tracing in 30 cases of Class I malocclusion and 30 of Class Ⅲ, the data were statistically analysed.Results:At-APH and S-APH in Class I malocclusion were shorter than those in Class Ⅲ(P