[Linear correlation between tooth movement and facial profile change in patients with class â ¡ division 1 malocclusion].

Objective: To investigate the correlation between tooth movement and profile change in patients with class Ⅱ division 1 malocclusion. Methods: Pre- and post-treatment lateral cephalograms of 42 patients [10 males and 32 females, (23.8±6.3) years old, mean treatment time: 1.9 years] with class Ⅱ division 1 malocclusion were collected in Department of Oral & Cranio-Maxillofacial Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine from June 2012 to November 2017. The patients were treated with extraction of four first premolars or two maxillary first premolars. Cephalometric analysis was carried out before and after treatment. Thirty parameters were measured. The changes of soft and hard tissue after orthodontic treatment and their correlations were analyzed using bivariate linear regression. Related factors affecting the upper and lower lip, nasolabial angle (NLA) and mentolabial angle (MLA) were analyzed according to the standardized regression coefficient (Beta). Results: Among all the 30 parameters, 18 parameters were statistically different before and after treatment. After treatment, upper central incisor sagittal distance [(63.87±7.14) mm] and upper lip sagittal distance [(77.73±7.60) mm] were significantly decreased (P<0.05). The changes in 14 parameters after treatment showed linear relationship including strong positive correlation between upper lip sagittal retraction and upper central incisor sagittal retraction (r=0.649, P<0.01). There were moderate positive correlations between upper lip and upper central incisor vertical movement (r=0.544, P<0.01). While the sagittal change of gnathion and the Y-axis angle showed moderate negative correlations (r=0.537, P<0.01). The stepwise multiple linear regression showed that the retraction of upper lip process was correlated with the retraction of upper central incisor, the increase of occlusal plane angle and the increase of upper central incisor angle, which was most correlated with the retraction of upper central incisor (Beta=0.79). The downward displacement of upper lip process was correlated with the downward displacement of upper incisor, the decrease of upper central incisor angle, the decrease of the distance between maxillary first molar and palatal plane, and the increase of occlusal plane angle, which was more correlated with the downward displacement of upper incisor and the increase of occlusal plane angle (Beta=0.59). The downward displacement of lower lip process was correlated with the downward displacement of upper incisor and lower incisor, which was more correlated with the upper incisor (Beta=0.36). Conclusions: The relationship among nose, lips and chin was more coordinated. Incisor retraction had significant influence on lip prominence, and the lower lip position was highly related to the movement of upper incisor in sagittal and vertical dimension after orthodontic treatment in patients with class Ⅱ division 1 malocclusion. However, tooth movement had limited impact on the chin position.

[MRI analysis of the effect on mandibular retrusion with anterior disc displacement treated by using Herbst appliance].

Objective: To investgate the effect of Herbst appliance on the growth and remodeling of the temporomandibular joint (TMJ) in class Ⅱ patients with mandibular retrusion by using MRI. Methods: Between December 2010 and October 2014, 12 class Ⅱ patients (11-16 years old) with mandibular retrusion were chosen. The patients were divided into two groups. The control group included 7 patients (14 joints) with normal disc condyle relationship and the anterior disc displacement (ADD) group included 5 patients (10 joints) with anterior disc displacement. The MRI images of TMJ were measured, including condylar height, joint space index and disc position ratio, before and after the treatment. Results: The condylar height of the patients in the control group was significantly increased (P<0.001) after treatment, and no significant difference in joint space index (P=0.821) and disc position ratio (P=0.146) was found. The joint space index of the patients ([-14.70±8.82]% and [4.90±11.35]%) in ADD group changed significantly (P<0.001) after treatment, and no significant difference in condylar height (P=0.294) and disc position ratio (P=0.120) was found. Conclusions: The normal disc condyle relationship was beneficial to the reconstruction of the condylar process, and the increase of the condylar height. The condyle moved forward in patients with anterior disc displacement after treatment.

Influence of temporomandibular joint disc displacement on mandibular advancement in patients without pre-treatment condylar resorption.

The purpose of this study was to clarify the correlation between pre-treatment anterior disc displacement and mandibular stability after orthognathic and orthodontic treatment among patients with a skeletal class II malocclusion and without pre-treatment condylar resorption. Thirty-seven patients were included (7 male, 30 female). The mean length of follow-up was 6.76±3.06 years. Patients with condylar resorption before treatment were excluded. Magnetic resonance images and lateral cephalometric radiographs were taken before treatment (T0), after treatment (T1), and at follow-up (T2). Patients were classified according to the degree of disc displacement: -10-10° 'normal', 11-50° 'slight to mild', ≥51° 'moderate to severe'. Results showed the condyle moved posterosuperiorly after treatment, and then moved anteriorly to a more concentric location during the long follow-up period. Condylar movement was found not to correlate with disc displacement. The degree of disc displacement before treatment did not correlate with the post-surgical mandibular positional change in either the sagittal or vertical direction. To conclude, the mandibular bilateral sagittal split ramus osteotomy was stable in the long-term after orthognathic and orthodontic treatment. In the absence of pre-treatment condylar resorption, the degree of initial anterior disc displacement did not have a significant influence on the stability of mandibular advancement.

The surgery-first approach in orthognathic surgery: a retrospective study of 50 cases.

The surgery-first approach (SFA), without presurgical orthodontic treatment, has become favoured in the treatment of dentomaxillofacial deformities. This approach has been applied in our institution since 2012. The purpose of this study was to report our experience with the SFA for skeletal malocclusion. Fifty patients with skeletal malocclusions were enrolled in this study (11 bimaxillary protrusion, 27 skeletal class III malocclusion, and 12 facial asymmetry). After orthognathic-orthodontic consultation, suitability for SFA was determined and a treatment plan drawn up. Patients then underwent orthognathic surgery, which included Le Fort I maxillary osteotomy, bilateral sagittal split ramus osteotomy, subapical osteotomy, and genioplasty. Postoperative orthodontic treatment was started after a healing period of 2 weeks. The mean postoperative orthodontic treatment duration was 14.9 months, which is shorter than that of traditional joint orthognathic-orthodontic treatment. In the bimaxillary protrusion group, this was about 19 months, which was longer than for the other groups. After joint orthognathic-orthodontic treatment, a good facial profile and ideal occlusion were achieved. With the advantages of earlier improvements in patient facial aesthetics and dental function, the reduction in difficulty and treatment duration of orthodontic management, and increasing patient acceptance, SFA is regarded as an ideal and valuable alternative for this potentially complicated procedure.

Changes in condylar and joint disc positions after bilateral sagittal split ramus osteotomy for correction of mandibular prognathism.

The effect of combined orthodontic and orthognathic treatment was studied retrospectively in 24 patients with skeletal class III malocclusions with mandibular hyperplasia, particularly the effect on temporomandibular joint (TMJ) disc position. The patients underwent preoperative orthodontic treatment, orthognathic surgery, and postoperative orthodontic treatment. The patients were studied clinically, radiographically with lateral cephalometric radiograph and MRI to locate the position of the TMJ disc in relation to the glenoid fossa. One patient had less pain after treatment, one lost abnormal joint clicking sounds after treatment. There were no TMJ symptoms in 20 of the 24 preoperatively and postoperatively. 48 sagittal MRI images showed that the disc length before treatment was 3.040-12.928 (mean 8.289+/-2.028) and after treatment was 3.699-11.589 (mean 8.097+/-1.966); results were not significant (p>0.05). Maximum disc displacement before treatment was 6.090 (mean 1.383), after treatment it was 11.931 (mean 2.193); results were not significant (p>0.05). The results suggest that combined orthodontic and orthognathic treatment (including bilateral SSRO and rigid internal fixation) can be used safely to correct skeletal class III malocclusion with mandibular hyperplasia without causing additional TMJ symptoms.