[Effect of semi-fixed Twin-block appliance on temporomandibular joint remodeling].

PURPOSE: To evaluate quantitatively the effect of semi-fixed Twin-block appliance on the temporomandibular joint remodeling during the Class II malocclusion treatment. METHODS: Twenty two Class II division 1 patients treated with semi-fixed Twin-block appliance were included. Pre- and post-orthopedic treatment cephalometric data were analyzed with SPSS13.0 software package for paired t test. RESULTS: The mandibular condylar growth was directed superiorly(2.7mm) and posteriorly (3.6mm) (P<0.01), the glenoid fossa was displaced in a inferior(1.5mm) (P<0.01) and posterior (0.8mm)(P<0.05) direction, the effective TMJ changes showed a pattern similar to condylar growth in a superior(4.2mm) and posterior(2.7mm) direction(P<0.01), the mandibular rotation was slightly clockwise(P>0.05). CONCLUSIONS: The application of semi-fixed Twin-block appliance shows its effectiveness on patients' compliance and the remodeling in temporomandibular joint, contributing to the correction of sagittal jaw relationship discrepancy.

[A comparison of rapid palatal expansion and Damon appliance on non-extraction correction of dental crowding].

PURPOSE: To compare the effect of rapid palatal expansion (RPE) and Damon technique on the correction of dental crowding with non-extraction approach. METHODS: 19 adolescent patients with non-extraction orthodontic treatment were reviewed. They had Class I skeletal pattern and moderate crowding. Nine subjects were treated with RPE followed by straight wire appliance, and 10 subjects were treated with Damon appliance only. The dental casts and cephalometric radiophotographs were measured before and after the treatment. The difference between two groups was analyzed for Student's t test with SPSS15.0 software package. RESULTS: Upper and lower inter-canine width increased 2.9mm and 1.3mm respectively in RPE group (P<0.05), while there was no significant change in Damon group. A significant posterior expansion of upper and lower arch width was noted in both RPE and Damon groups (P<0.05). The increase in upper inter-bicuspid width and lower inter-molar width was comparable in two groups. The upper inter-molar width in RPE group expanded 5.3mm, which was significantly larger than that of 3.1mm in Damon group(P<0.05). The increase in lower inter-bicuspid width in Damon group, on the other hand, was larger than that of RPE group (4.5mm vs. 1.5mm). (P<0.05) Both groups showed buccal tipping of bicuspids and molars, with more extend of bicuspid tipping in Damon group (P<0.05). The maxillary base width increased 2.1mm in RPE group, which was significantly larger than that of 0.6mm in Damon group (P<0.05). The upper and lower incisors in Damon group were tipped forward by 9.2 degrees and 7.5 degrees respectively, while the change in RPE group was not significant (P<0.05). CONCLUSION: Both RPE and Damon technique can successfully increase the arch width and correct moderate dental crowding with non-extraction approach. Damon appliance protrudes the upper and lower incisors and expands the dental arch by buccal tipping of bicuspids and molars. RPE expands the maxillary base along with the whole upper dental arch and could maintain the incisors in upright position.

[The preliminary study of the treatment timing for rapid maxillary expansion].

PURPOSE: The aim of this study was to find the treatment timing of rapid maxillary expansion by investigating the relationship among the chronologic age, dental age, skeletal age and treatment effect of rapid maxillary expansion. METHODS: A sample of thirty patients who required rapid maxillary expansion was selected. The patients ranged in age from 11 to 14 years, with the mean age being 12.30 years. Assessment of the skeletal age was made with a hand radiograph before treatment. The posteroanterior cephalograms, occlusal radiograph of the maxilla were taken at the time of pretreatment and post-treatment. Paired t test and multiple regression analysis were used for statistical analysis. RESULTS: The results showed that the effects of rapid maxillary expansion were different even though the chronologic ages were similar. A negative correlation was found between the skeletal age and the expansive effect. Regressive coefficient was -6.440, P value was 0.045. There was a significant negative correlation between the dental age and the expansive effect. The regressive coefficient was -1.289, P value was 0.000. The expansive effect was on the decrease while the second maxillary molars erupted continuously. CONCLUSION: It is proposed that rapid maxillary expansion could be used successfully before the second maxillary molars erupt. The optimal orthopedic effect could be attained.

[Non-extraction approach using RPE to correct Angle Class I malocclusion with moderate crowding: A cephalometric study].

PURPOSE: To study cephalometric changes in Angle Class I malocclusion with moderate crowding treated orthodontically without extraction using rapid palatal expansion (RPE). METHODS: 9 patients with Angle Class I moderate crowding were orthodontically treated with a non-extraction approach using RPE and fixed edgewise appliances.The cephalometric analysis was performed at T1(pretreatment), T2(3 months after RPE) and T3(fixed retention period after active treatment). RESULTS: Lateronasal width, maxillary width, upper and lower first molar width significantly increased after rapid expansion (T1-T2) and after active treatment (T1-T3) with the significant difference in upper first molar width between T2 and T3. Total facial height, upper anterior facial height, the inclination of palatal plane and Y axis increased significantly (T1-T2, T1-T3). There were significant differences in the inclination of mandibular plane among T1, T2 and T3. CONCLUSION: Maxillary transverse width could increase using RPE. Rapid palatal expansion might not result in the anteroposterior changes.

[A clinical study of the changes of condylar position in class division 2 deep-bite patients after orthodontic treatment].

OBJECTIVE: To observe the effects of orthodontic treatment on the changes of condylar position in Class division 2 deep-bite patients. METHODS: 11 patients with Class division 2 deep-bite malocclusion were orthodontically treated, the changes of condylar position were evaluated by means of 3D-CT and Sam-diagnostic articulator. RESULTS: With the increase of inclination of upper incisors and opening bite, there were statistically significant changes of condylar longitudinal distance and condylar height in both sides, and retruded contact position-intercuspal position(RCP-ICP) discrepancy was significantly reduced. CONCLUSION: The condylar position in division 2 deep-bite patients could be orthodontically changed, moving anterior-inferiorly and approaching RCP.