Qianyang Xie

Is mandibular asymmetry more frequent and severe with unilateral disc displacement

PURPOSE To investigate the prevalence of mandibular asymmetry (MA) within the symptomatic unilateral anterior disc displacement (ADD) patients, and analyze the influence TMJ factors of the MA severity. METHODS Patients aged under 20 years old with symptomatic unilateral ADD and asymptomatic volunteers with normal disc-condyle relationship diagnosed by magnetic resonance imaging (MRI) were included in this study. Posteroanterior cephalometric radiographs were taken to measure MA. Condylar height, disc length and disc displacement were measured by MRI. The prevalence and severity of MA were compared between the ADD and the control groups. The correlation between the severity of MA with the amount of condylar height shortage, disc deformity and distance of disc displacement were also evaluated within the ADD group. RESULTS There were 165 cases in the unilateral ADD group, and 156 cases in the control group. One hundred and nineteen cases had MA which accounted 72.12% (119/165) in the ADD group; while in the control group, only 25.64% (40/156) exhibited MA. The mean horizontal menton deviation and condylar height shortage in the unilateral ADD group were significantly larger than that in the control group (5.62 mm vs. 4.19 mm; 3.14 mm vs. 1.32 mm, p < 0.01). The severity of MA was significantly correlated with the amount of disc displacement, disc deformity and condylar height shortage (correlation coefficient: 0.80, 0.70, and 0.82). CONCLUSION MA is much more common and severe in young unilateral ADD patients. The severity of MA is correlated with the height of condyle and the status of the disc.

Prevention and Treatment for the Rare Complications of Arthroscopic Surgery in the Temporomandibular Joint

PURPOSE To analyze the rare complications of arthroscopic surgeries in the temporomandibular joint (TMJ) and to investigate the preventive and treating methods. PATIENTS AND METHODS In this study, 2,034 consecutive patients (2,431 joints), diagnosed as TMJ internal derangement, were treated by arthroscopic surgeries when visiting the TMJ clinic at the Ninth Peoples Hospital, School of Medicine, Shanghai Jiao Tong University, between May 2001 and September 2009. The clinical complications were analyzed to investigate cause, prevention, and control measures. RESULTS Of all 2,034 cases, the complications were shown as follows: 5 joint hemorrhages of the lateral pterygoid muscle vascular, injuries of the lateral pterygoid muscle nerve in 5 joints, 3 joints with broken instruments, rejection reaction in 2 joints, and perforation of tympanic membrane in 2 joints. CONCLUSIONS Arthroscopic surgery was a safe and effective method to treat TMJ internal derangement; its complications were limited and acceptable, but an experienced operator was required for this surgical technique.

Is Anterior Disc Displacement Without Reduction Associated With Temporomandibular Joint Condylar Height in Juvenile Patients Younger Than 20 Years

PURPOSE Because disc displacement might be accompanied by degenerative changes in the condyle, this study explored the association between condylar height and anterior disc displacement without reduction in juvenile patients. MATERIALS AND METHODS This was a retrospective cohort study that enrolled a sample of patients younger than 20 years with unilateral disc displacement without reduction. All patients had 2 magnetic resonance imaging records taken from January 2010 to June 2013 (interval, >6 months). Condylar height, disc length, and displacement distance were measured. The predictor variable was joint status (healthy vs affected side), and the outcome variables were changes in condylar height, displacement distance, and disc length over time. SAS 9.13 was used for analysis and the P value was set at .05. RESULTS One hundred twenty-four patients (101 female and 23 male; mean age, 16.4 yr; mean interval, 13.6 months) were included. During the interval, the condylar height of the healthy side increased 0.75 mm, whereas the condylar height of the affected side decreased 0.41 mm. The disc of the affected side was shortened and more anteriorly displaced. CONCLUSION Anterior disc displacement without reduction could be accompanied by a decrease in condylar height in juvenile patients, and the disc might be shortened and more anteriorly displaced.

An Orthodontic Technique for Minimally Invasive Extraction of Impacted Lower Third Molar

PURPOSE To present a novel orthodontic approach for minimally invasive extraction of impacted mandibular third molars (M3s) close to the inferior alveolar nerve (IAN). PATIENTS AND METHODS Eight patients (8 M3s) requiring extraction of M3s were included in this study; there were 2 cases of horizontal impaction, 4 of mesioangular impaction, and 2 of vertical impaction. Cone-beam computed tomogram showed that the roots of impacted M3s in 2 cases interrupted the cortices of the mandibular canal, and those in the other 6 cases were very close to the IAN. Orthodontic treatment was performed in this study. The crowns of 5 impacted teeth were surgically exposed before the application of the orthodontic device, whereas bonding was performed directly to the occlusal surface of the other 3 M3s, which had partially erupted. The opposing maxillary M3s were removed in 3 cases. One-step orthodontic extraction was applied to vertically impacted M3s and 2-step treatment was applied to horizontally or mesioangularly impacted M3s. Success was defined as the separation of the impacted tooth from the IAN as visualized on cone-beam computed tomogram. RESULTS After orthodontic treatment, all impacted M3s were extruded and separated from the IAN (mean, 6.6 months; range, 4 to 10 months), without any neurologic consequences. The average time of extraction was 5 minutes. In all 8 cases, new bone formation occurred distal to the adjacent second molar. CONCLUSION This orthodontic technique may be a minimally invasive approach for the extraction of impacted M3s adjacent to the IAN, with a decreased risk of paresthesias and with osteoperiodontal advantages.

Marsupialization Facilitates Eruption of Dentigerous Cyst-Associated Mandibular Premolars in Preadolescent Patients

PURPOSE The purpose of the present study was to investigate the eruption of dentigerous cyst (DC)-associated mandibular premolars after marsupialization in preadolescents. PATIENTS AND METHODS The present study was a retrospective cohort study of preadolescent patients with DCs who were treated as outpatients at the Department of Oral and Maxillofacial Surgery, Ninth Peoples Hospital, Shanghai Jiao Tong University School of Medicine. For our study, the data from these patients were collected, and the eruption of the premolar teeth, along with related factors, such as the interval to eruption, cusp depth, angulation, cyst size, and eruption space, were analyzed for the cyst group compared with the noncyst control group. RESULTS The mean age of the patients was 9.1 years. All teeth associated with DCs erupted successfully after marsupialization. The follow-up panoramic radiograph showed that the cysts had disappeared and had been replaced by regenerated bone. The initial panoramic radiograph showed the angulation of the teeth in the cyst group had a significantly larger inclination angle than did the teeth in the noncyst group (P < .05). However, no significant difference was found for cusp depth, root formation, or space measurement. The gender, age, cusp depth, angulation, and eruption space were not factors influencing the eruption of the DC-associated tooth for preadolescent patients in the present study. In addition, the cyst-associated teeth took less time to erupt than the teeth in the control group. CONCLUSIONS The results of the present study suggest that DC-associated mandibular premolars can erupt spontaneously after marsupialization in preadolescents.

The effects of static pressure on chondrogenic and osteogenic differentiation in condylar chondrocytes from temporomandibular joint

OBJECTIVE The goal of the study was to investigate the production of collagen, type II, alpha 1 (COL2A1), SOX9, alkaline phosphatase (ALP), runt-related transcription factor 2 (Runx2), Indian hedgehog (Ihh), and periarticular cell-derived parathyroid hormone-related protein (PTHrP) in mandibular condylar chondrocytes under static pressure stimuli. METHODS Mandibular condylar chondrocytes separated from rabbit temporomandibular joint (TMJ) were treated with a static pressure of 100kPa for 0, 1, 2, 3, and 4h by an in-house-designed pressure chamber. A CCK-8 kit was used to analyze the cell viability. The production of COL2A1, SOX9, ALP, Runx2, Ihh, and PTHrP was detected by Western blot or real-time polymerase chain reaction (PCR). Changes in cell morphology were observed by scanning electron microscopy. RESULTS Compared with the control group (0h), the cytoplasmic processes of treated chondrocytes obviously increased and elongated, and the cell viability of pressurized chondrocytes were 91.13% (1h), 103.41% (2h), 103.47% (3h), and 104.94% (4h), respectively. The exposure of condylar chondrocytes to a static pressure of 100kPa for 3-4h resulted in a significant increase in COL2A1, SOX9, ALP, and Runx2. After a static pressure loading of 100kPa, the activation of Ihh and PTHrP was also observed. CONCLUSIONS Mandibular condylar chondrocytes adapt to alterations of the microenvironment. Ihh and PTHrP are sensitive to static pressure. Our findings suggest that static pressure accelerated the chondrogenic and osteogenic differentiation of condylar chondrocytes, which may influence the pathological progress of temporomandibular diseases.

Study on the effects of gradient mechanical pressures on the proliferation, apoptosis, chondrogenesis and hypertrophy of mandibular condylar chondrocytes in vitro

OBJECTIVE To investigate the effects of gradient mechanical pressure on chondrocyte proliferation, apoptosis, and the expression of markers of chondrogenesis and chondrocyte hypertrophy. METHODS Mandibular condylar chondrocytes from 5 rabbits were cultured in vitro, and pressed with static pressures of 50kPa, 100kPa, 150kPa and 200kPa for 3h, respectively. The chondrocytes cultured without pressure (0kPa) were used as control. Cell proliferation, apoptosis, and the expression of aggrecan (AGG), collagen II (COL2), collagen X (COL10), alkaline phosphatase (ALP) were investigated. Ultrastructures of the pressurized chondrocytes under transmission electron microscopy (TEM) were observed. RESULTS Chondrocyte proliferation increased at 100kPa and decreased at 200kPa. Chondrocyte apoptosis increased with peak pressure at 200kPa in a dose-dependent manner. Chondrocyte necrosis increased at 200kPa. The expression of AGG increased at 200kPa. The expression of COL2 decreased at 50kPa and increased at 150kPa. The expression of COL10 and ALP increased at 150kPa. Ultrastructure of the pressurized chondrocytes under TEM showed: at 100kPa, cells were enlarged with less cellular microvillus and a bigger nucleus; at 200kPa, cells shrank with the sign of apoptosis, and apoptosis cells were found. CONCLUSIONS The mechanical loading of 150kPa is the moderate pressure for chondrocyte: cell proliferation and apoptosis is balanced, necrosis is reduced, and chondrogenesis and chondrocyte hypertrophy are promoted. When the pressure is lower, chondrogenesis and chondrocyte hypertrophy are inhibited. At 200kPa, degeneration of cartilage is implied.

Efficacy of the technique of piezoelectric corticotomy for orthodontic traction of impacted mandibular third molars

Our aim was to assess the efficacy of piezoelectric corticotomy for orthodontic traction of mandibular third molars close to the inferior alveolar nerve. Thirty patients with impacted third molars close to the nerve were included in the study, 15 of whom were treated with conventional orthodontic traction and 15 with piezoelectric corticotomy. We recorded duration of treatment including exposure and orthodontic traction, and time to the final extraction. Postoperative complications including trismus, swelling, and pain were also noted. Alveolar bone levels mesial and distal to the second molars were evaluated on cone-beam computed tomographic (CT) images. Students t test was used to assess the significance of differences between the groups. After orthodontic treatments all impacted third molars were successfully removed from the inferior alveolar nerve without neurological damage. The mean (SD) duration of surgical exposure in the piezoelectric corticotomy group was significantly longer than that in the conventional group (p=0.01). The mean (SD) duration of traction was 4 (2.3) months after piezoelectric corticotomy, much shorter than the 7.5 (1.3) months in the conventional group (p=0.03). There were no significant differences in postoperative complications between the groups. There was a significant increase in the distal alveolar height of second molars after treatment in both groups (p<0.01). We conclude that the use of piezoelectric corticotomy allows more efficient and faster traction of third molars with a close relation between the root and the inferior alveolar nerve, although it took longer than the traditional technique.

Does condylar height decrease more in temporomandibular joint nonreducing disc displacement than reducing disc displacement?: A magnetic resonance imaging retrospective study

AbstractThe aim of the study was to compare condylar height changes of anterior disc displacement with reduction (ADDwR) and anterior disc displacement without reduction (ADDwoR) in temporomandibular joint (TMJ) quantitatively, to get a better understanding of the changes in condylar height of patients with anterior disc displacement who had received no treatment, and to provide useful information for treatment protocol. This longitudinal retrospective study enrolled 206 joints in 156 patients, which were divided into ADDWR group and ADDwoR group based on magnetic resonance imaging examination. The joints were assessed quantitatively for condylar height at initial and follow-up visits. Also, both groups were further divided into 3 subgroups according to age: <15 years group, 15 to 21 years group, and 22 to 35 years group. Paired t test and independent t test were used to assess intra- and intergroup differences. The average age of the ADDwR group was 19.65 years with a mean of 9.47 months’ follow-up. The follow-up interval of the patients with ADDwoR was 7.96 months, with a mean age of 18.51 years. Condylar height in ADDwoR tended to decrease more than those in ADDwR, especially during the pubertal growth spurt and with the presence of osteoarthrosis, meaning ADDwoR could cause a severe disturbance in mandibular development. Thus, an early disc repositioning was suggested to avoid decrease in condylar height.

Changes in the temporomandibular joint space after functional treatment of disk displacement with reduction.

AbstractThis study aimed to evaluate the changes of temporomandibularjoint (TMJ) space in the treatment of disk displacement with reduction (DDWR) for class II cases. Forty-two adolescent patients with unilateral DDWR, who were successfully treated by functional appliance, were selected in this study. Magnetic resonance imaging scans were used before treatment (T1), at the start of treatment (T2), and after functional treatment (T3). Compared with the normal joint, the change of joint space index was calculated. The anterior, posterior, and superior joint spaces were analyzed on the largest sagittal plane among T1, T2, and T3. Student’s t-test was used for statistical analysis. The mean treatment period was 10 months (6–16 mo). Functional appliance was effective in eliminating pain and clicking. During the phase of T1, the value of the joint space index of DDWR was significantly higher than that of the control (P < 0.05). There was a significant decrease in the anterior space and an increase in the postsuperior space at T2 (P < 0.01), and then the contrary changes occurred at T3. However, there was a significant increase in the postsuperior space and no significant decrease in the anterior space when T1 and T3 were compared. This study indicates that the TMJ space is well distributed after disk repositioning with functional treatment of DDWR. It is also suggested that the adaptive remodeling in TMJ occurs via functional treatment.