[Comparison of clear aligners and customized lingual appliance for bimaxillary dentoalveolar protrusion: a retrospective study].

PURPOSE: To compare the treatment effects of clear aligners and customized lingual appliance on treating bimaxillary dentoalveolar protrusion patients with first premolar extractions. METHODS: Fifty-four patients with bimaxillary dentoalveolar protrusion treated in Shanghai Ninth People Hospital were involved in the retrospective study. Twenty-five cases used clear aligners and 29 cases used customized lingual appliance. All of them were treated by extracting 4 first premolars and retracting anterior teeth with strong anchorage. The changes of anterior tooth and soft tissue adduction before and after treatment were compared by lateral cephalometric measurements. SPSS 26.0 software package was used for data analysis. RESULTS: The total course of treatment in the clear aligners group (46.32±7.37 months) was about 10.8 months longer than that in the customized lingual appliance group (35.55±5.90 months) (P＜0.05). There was no significant difference in upper incisor retraction, lower incisor inclination and overjet reduction between the two groups(P＞0.05). There were significant differences in upper lip retraction, lower lip retraction, upper incisor torque reduction, and overbite reduction between the two groups(P＜0.05). Customized lingual appliance group showed a significant improvement of lips retraction and overbite reduction in orthodontic treatment. For the correction of overjet, there was no significant difference between the two groups (P=0.337). The data of U1-OP (the distance between edge of the upper central incisor and the functional occlusal plane) was not in normal distribution, and there was no significant difference between the two groups(P=0.184). CONCLUSIONS: The two techniques can both retract the anterior teeth and lips to improve the profile. However, the customized lingual appliance was more effective in improving the soft tissue profile of patients with bimaxillary dentoalveolar protrusion, with shorter treatment course.

[In vitro study of a new lasso device for intra-canal broken instrument removal].

PURPOSE: To collect facial stereo images of different lip protrusion by using three dimensional surface imaging device, and investigate facial aesthetic evaluation and differences between orthodontists, general dentists and laypeople. METHODS: In this study, one college student was recruited to take a three-dimensional image of the natural head and face. The software was simulated with a gradient of 2 mm to make the soft tissue lips move back and forth along the sagittal axis from the VSL line.The movement limit was 6 mm in front of and behind the VSL line. The observers included orthodontists, general dentists and laypeople. The data were analyzed with SAS 9.4 software package,visual analog scoring (VAS) was used for evaluation, and fixed-effect model was used for statistical analysis. RESULTS: The results showed that when the lip was on the VSL line, it got the highest scores amount all three groups and had no significant difference.When the lip became protrusive or retractive, it had negative impact on facial esthetics. There were significant differences in the scores of three groups in every 2mm of lip protrusion and lip retraction(P＜0.05). VAS 5 points or less were used as the unacceptable facial aesthetic score. The results showed that lip protrusion was 4 mm before the VSL line in the orthodontist group and less than 5 in the laypeople group . When the lip protruded 6mm before the VSL line and retracted 4 mm behind the VSL line, the scores of the three groups were lower than 5 points. The results also showed that male evaluation of lip protrusion 2 mm before the VSL line had a lower score than female; On the other hand, female evaluation of lip retraction behind the VSL line above 4mm had a lower score than male. CONCLUSIONS: Lip position has significant effect on facial aesthetics. Different observers had significant differences in the evaluation of lip position on facial aesthetics. It is suggested that orthodontists need more communication with patients in determining the target position of orthodontic treatment to improve treatment satisfaction.

[Assessing the influence of chin prominence on perceived facial aesthetics among three groups of observers].

PURPOSE: To assess the influence of chin prominence on facial aesthetics with 3D images, to investigate the cognitive boundaries of chin prominence among orthodontists, general dentists and laypeople and compare the variance of their cognitive data, in order to provide quantitative reference for selection of clinical treatment. METHODS: A 3D facial image was obtained by 3dMD. The soft tissue pogonion point was altered in 2 mm increments from -10 to 10 mm with Geomagic Wrap 2015, in order to represent retrusion and protrusion of the chin. These images were rated by orthodontists, general dentists and laypeople with VAS scores. Multivariate mixed linear regression was used to analyze the influence of gender, age and chin prominence on VAS scores, and whether there were differences among different groups with SAS 9.4 software package. ANOVA was also applied for comparison of each prominence. RESULTS: This study was composed of 243 subjects, including 90 orthodontists, 101 general dentists and 52 laypeople. Chin prominence had significant effect on VAS scores. VAS scores decreased by 0.8910 for each unit increase in chin retrusion and decreased by 1.0958 for each unit increase in chin protrusion（P<0.01）. Desire for treatment started when chin retrusion exceeded 6 mm in orthodontist group and layperson group, 4 mm in general dentist group, and chin protrusion reached 6 mm in all groups（VAS scores <5）. There was no significant difference in the scores among orthodontists, general dentists and laypeople with the variance of chin prominence, and there was no significant difference in gender and age. CONCLUSIONS: Chin prominence had significant effect on facial aesthetics. Soft tissue pogonion point located on the zero meridian was considered as the most attractive. Treatment needs increased significantly when chin protrusion reached 6 mm or chin retrusion exceeded 6 mm. There was no significant difference in the assessment among orthodontists, general dentists and laypeople.

[Clinical study of ramus implant anchorage for mandibular arch distalization].

PURPOSE: To evaluate the efficiency of ramus implant anchorage for mandibular arch distalization, and determine the feature of tooth movement. METHODS: Six patients were selected to distalize mandibular arch with ramus implant anchorage. Position changes of mandibular first molars and incisors were measured in sagittal and vertical direction to evaluate the amount of molar and incisor distalization and character of tooth movement. SPSS17.0 software package was used for statistical analysis. RESULTS: The average amount of distalization of mandibular first molar was 4.88mm at crown level and 3.1mm at root level, and of mandibular incisor was 5.02mm at crown level and 1.03mm at root level. All of the lower arches were distalized successfully and achieving normal overjet and overbite. CONCLUSIONS: Significant true distalization of lower arch could be obtained by ramus implant as bony anchorage. The method could be used to correct anterior cross bite and mandibular anterior crowding or flaring without extraction.