[A study on the combination of Nance arch and TPA in the use of straight-wire arch orthodontic treatment].

PURPOSE: To evaluate the effect of combination of Nance and TPA on the use of MBT appliance to treat Class II division I malocclusion. METHODS: Nineteen cases of Class II division I malocclusion, aged from 12 to 16 years, underwent Nance arch and TPA in the use of MBT appliance to reinforce molar anchorage. Cephalometric analysis and model measurements were conducted and compared before and after treatment using SAS8.0 software package. RESULTS: The average forward movement of the first maxillary molar was (1.97 ± 0.696)mm, but still less than 1/3 of the extraction space.U1-SN reduced 10.97° ± 3.81°.There was no significant difference in GoGn-Sn angle,ALFH /AFH and posterior dental arch width(P>0.05).The soft tissue profile (Ls-E,Ls-Snpg,Cm-Sn-Ls) was improved remarkably (P<0.01). CONCLUSION: The combination of Nance and TPA might be effective and simple anchorage in three dimensions.

[Dental arch form reverting by four-point method].

PURPOSE: To explore a simple method of reverting individual dental arch form template for wire bending. METHODS: Individual dental arch form was reverted by four-point method. By defining central point of bracket on bilateral lower second premolar and first molar, certain individual dental arch form could be generated. The arch form generating procedure was then be developed to computer software for printing arch form. Four-point method arch form was evaluated by comparing with direct model measurement on linear and angular parameters. The accuracy and reproducibility were assessed by paired t test and concordance correlation coefficient with Medcalc 9.3 software package. RESULTS: The arch form by four-point method was of good accuracy and reproducibility (linear concordance correlation coefficient was 0.9909 and angular concordance correlation coefficient was 0.8419). CONCLUSION: The dental arch form reverted by four-point method could reproduce the individual dental arch form.

[Preliminary clinical study on intrusion of overerupted molars with a removable appliance].

PURPOSE: To evaluate the clinical effect of molar intrusion with a removable appliance and determine its clinical value. METHODS: Seven patients were selected in the study.The clinical effect of intrusion was evaluated,the periodontal attachments and root resorption post-treatment were accessed by models,clinical examination, periapical radiograph analysis via CygnusRay2TM digital X-ray system pre and post-treatment.The data was analyzed using SAS6.12 software package. RESULTS: All the overerupted molars had been intruded successfully within an average time of 3.7 months.Pre and post-treatment model analysis demonstrated the maximum intrusion amount was 3.05mm,minimum 1.03mm and mean 0.58mm per month.Analysis of pre and post-treatment periapical radiographs and periodontal probing depth showed no significant difference in probing depth,distance from cemento-enamel junction to alveolar bone crest,mesial and distal tooth length between pre- and post- treatment (P>0.05). CONCLUSIONS: Molar intrusion with the removable appliance has a significant effect without apparent destruction of the periodontal tissue and root resorption.