Evaluation of post-surgical stability in skeletal class II patients with idiopathic condylar resorption treated with functional splint therapy.

PURPOSE: To assess postsurgical stability of mandibular advancement combined with orthodontic treatment, following functional splint therapy, in patients with idiopathic condylar resorption (ICR). PATIENTS AND METHODS: Sixteen patients who were treated with functional splint therapy followed by orthognathic surgery combined with orthodontic treatment between 2010 and 2017 were included in this retrospective study. The primary outcome variable was skeletal stability, measured on the y-axis to point B (y-axis-B). Cephalometric analysis, including measurement of temporomandibular joint spaces, was carried out on serial magnetic resonance images (MRI) prior to orthognathic surgery (T0), immediately after surgery (T1), and after at least 1 year of follow-up (T2). The differences in the data between time points were compared using statistical analyses. RESULTS: All patients obtained an esthetic facial profile after orthognathic surgery, with normal occlusion as well as normal protrusive and laterotrusive excursion after treatment. Mean advancement of the mandible immediately following surgery (y-axis-B, T1 - T0) was 7.28 ± 5.79 mm. This was the only skeletal measurement that showed a sagittal positional change of the mandible. Mean backward movement (T2 - T1) was -1.04 ± 2.35 mm (p2 = 0.116). Thirteen out of 16 patients experienced no postsurgical relapse or less than 2 mm of mandibular backward movement (81.25%), while two out of 16 patients showed more than 2 mm of mandibular backward movement (12.5%). CONCLUSIONS: Patients who underwent mandibular advancement combined with orthodontic treatment, following functional splint therapy, exhibited a stable mandibular position at the 1-year follow-up. This study indicated that functional splint therapy prior to orthognathic surgery for mandibular advancement may be a good adjuvant treatment for ICR patients.

Growth pattern and physiological characteristics of the temporomandibular joint studied by histological analysis and static mechanical pressure loading testing.

OBJECTIVE: The aim of this study was to investigate the age-related changes in the articular disc, condyle, condylar fibrocartilage, and subchondral bone of the temporomandibular joint (TMJ) in rabbits. METHODS: Female New Zealand white rabbit aged 1, 4, 12, and 32 weeks were obtained. Each age group comprised 5 rabbits and was subjected to chondrocyte culture, histological assessment of the articular disc length, assessment of the anteroposterior diameter of the condyle, measurement of the fibrocartilage thickness, and assessment of the subchondral bone architecture. The production of Collagen, type II, alpha1 (COL2A1); SOX9; Collagen, type X, alpha1 (COL10A1); and Runt-related transcription factor 2 (Runx2) was detected via western blot. Six rabbits at the ages of 12 and 32 weeks were sacrificed for the mechanical pressure loading test (75 kPa, 3 days). Changes in the condyles after pressurization were observed via scanning electron microscopy and evaluated by micro-CT. RESULTS: Significant enlargement of the condyle occurred from 4 to 12 weeks of age (p = 0.003); however, the length of the articular disc increased significantly from 1 to 12 weeks of age (p < 0.005). A rapid decrease in the cartilage thickness but an increase in the subchondral bone density occurred from 1 to 4 weeks of age and from 4 to 32 weeks of age in rabbit, respectively (p < 0.05). The expressions of COL2A1 and SOX9 gradually decreased from 1 to 32 weeks of age. The protein expressions of COL10A1 and Runx2 were maintained at a high level at 4-12 weeks of age. After static mechanical pressure loading, the damage and reduction in the bone mineral density (BMD) in the12-week-old group was greater than those in the 32-week-old group. CONCLUSIONS: An inconsistency between the condyle and articular disc during growth and development may be a causal factor for temporomandibular disorders TMDs in adolescents. Our findings suggest that the response of the adult condyle to the mechanical pressure is significantly greater than that of the adolescent condyle; however, with regard to reconstruction, the situation is reversed, which may influence the pathological progress of TMDs.

A Retrospective Cohort Study of Risk Factors for Descending Necrotizing Mediastinitis Caused by Multispace Infection in the Maxillofacial Region.

PURPOSE: Descending necrotizing mediastinitis (DNM) has been the most common life-threatening complication of multispace infection (MSI) in the maxillofacial region owing to the lack of a timely diagnosis and treatment. We assessed the clinical characteristics and diagnosis of odontogenic MSI and evaluated the risk factors for DNM caused by MSI. PATIENTS AND METHODS: We performed a retrospective cohort study of inpatients with MSI in the maxillofacial region from January 2012 to October 2016. The patients were classified into a non-DNM group and a secondary DNM group. The information collected included gender, age, systemic comorbidities, source of maxillofacial infection, computed tomography imaging data, and laboratory test results. Univariate analysis (t test and χ2 test, or the Fisher exact test) and logistic regression analysis were applied. RESULTS: A total of 296 patients were included. The mortality was 6.3%. On univariate analysis, the following factors were statistically significant: gender (P = .001); age (P = .003); source of infection (P = .004); number of affected spaces (P < .001); involvement of the parotid space (P < .001), submandibular space (P < .001), subgingival space (P < .001), pterygomandibular space (P < .001), parapharyngeal space (P < .001), and retropharyngeal space (P < .001); and percentage of neutrophils (P < .001). On multivariate analysis, the parapharyngeal space (P = .008), source of infection (P = .037), and number of affected spaces (P < .001) were statistically significant. CONCLUSIONS: Glandular infection, parapharyngeal space involvement, and the presence of multiple affected spaces were risk factors for DNM. Clinicians should vigilantly watch for these factors during clinical treatment and effective measures taken to prevent the occurrence of DNM as soon as possible.

Internal Jugular Vein Thrombosis With Serious Cervical Necrotizing Fasciitis.

Internal jugular vein thrombosis (IJVT) is a rare complication of cervical necrotizing fasciitis (CNF) which may lead to life threat. This article reports a patient with severe CNF complicated with IJVT, and combined with the literature to analyze the diagnosis and treatment of CNF and IJVT.

Diagnosis and Treatment of Gorham-Stout Disease in Maxillofacial Regions.

PURPOSE: This study was aimed to investigate the clinical features, imaging examination, and treatment of the patients with Gorham-Stout disease (GSD) in maxillofacial region, so as to improve the understanding of GSD. METHODS: The medical records of the patients with GSD who were referred to Shanghai Ninth People's Hospital from January 2010 to May 2016 were reviewed. Their ages, lesion location, imaging results, laboratory examination results, treatment, and therapeutic effects were analyzed. RESULTS: A total of 4 cases were included (males 2, females 2). The average onset age was 40 years. GSD attacked the mandible in 2 cases; mandible and temporal bone in 1 case; and mandible, temporal bone, and zygoma in 1 case. All cases were examined by computed tomography (CT), which showed bone resorption and atrophy of soft tissue in involved region. Four patients were given alendronate for treatment. All of them had no significant signs of progress after treatment. CONCLUSIONS: GSD can affect one single bone or multiple bones in maxillofacial region. The diagnosis mainly depends on the imaging examinations. Enhanced CT or magnetic resonance imaging is advocated for differential diagnosis of this disease. Alendronate was used with apparent good effect in these patients.

Risk Factors Affecting the Prognosis of Descending Necrotizing Mediastinitis From Odontogenic Infection.

PURPOSE: Descending necrotizing mediastinitis (DNM) is a serious complication of head and neck infections and has an excessively high mortality rate owing to the lack of understanding of DNM. We assessed the clinical characteristics, diagnosis, treatment, and outcomes of odontogenic DNM and evaluated the risk factors affecting the prognosis of DNM to provide an up-to-date overview for clinical practice. MATERIALS AND METHODS: We performed a retrospective cohort study, enrolling a sample of patients with DNM due to odontogenic infection who had been referred from January 2013 to December 2016. The patients were classified into surviving and deceased groups. The primary predictors in the present study were the presence of multiple comorbidities, complications, demographic data (age, gender), laboratory tests (white blood cell count, percentage of neutrophils), and time (duration before diagnosis, length of hospital stay). The primary outcome variable was the patient outcome (dead or alive). The continuous variables were evaluated using Student's t test or the t test, and the categorical and binary variables were compared using the χ2 test or Fisher exact test. RESULTS: A total of 81 patients (68 men, 13 women; median age of 57.2 ± 12.2 years) were included. The mortality was 4.9%. The most frequent cause of DNM was periapical periodontitis (66.7%). The lower posterior molars were involved in 39.5% of the cases. Treatment consisted of antibiotic therapy, aggressive transcervical mediastinal drainage (n = 74), and thoracotomy (n = 7). The associated risk factors for mortality were complications (P < .005) and severe sepsis or septic shock (P < .001) on bivariate analysis. CONCLUSIONS: Septic shock and complications were the risk factors that correlated with a poor prognosis. A timely diagnosis and use of aggressive mediastinal drainage are fundamental to reducing the incidence of complications and the development of septic shock in odontogenic DNM patients.

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.

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

The 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.

Will unilateral temporomandibular joint anterior disc displacement in teenagers lead to asymmetry of condyle and mandible? A longitudinal study.

PURPOSE: To evaluate the change of morphological symmetry of the temporomandibular joints (TMJ) during natural course of unilateral juvenile anterior disc displacement (UJADD) by comparing the ipsilateral joint with the contralateral side; and to analyse its effect over mandibular asymmetry (MA). PATIENTS AND METHODS: This study is a self-control longitudinal study. Consecutive UJADD cases with no history of TMJ infection, injuries to the jaws, or congenital, developmental and systematic disorders that may affect the craniofacial growth were collected and followed for at least 6 months. Patients' age at both first visit and revisit was recorded. Pictures of magnetic resonance imaging (MRI) were selected to measure the differences between bilateral condylar height, disc length and condyle-disc distance, and comparison of the measurements before and after follow-up were made. Meanwhile, posteroanterior cephalometric radiographs (PA) were taken and deviation of menton from facial midline was measured before and after follow-up. Severity of MA was divided into 4 stages according to menton deviation: Non-MA (<2 mm), Minor-MA (≥2 mm, <4 mm), Medium-MA (≥4 mm, <6 mm), and Major-MA (≥6 mm). The constituent ratio of MA was evaluated and correlation between TMJ morphological change and asymmetry of the mandible was analysed. RESULTS: Forty four patients were included, with a mean follow-up of 12.22 months. The average age was 16.31 years old (range, 10-20 years) at first visit. Significant progression of disc displacement was found: condyle-disc distance increased, disc shortened and difference between bilateral condylar heights increased. Along with this, occurrence of MA increased from 86.36% to 93.18%, and average menton deviation increased from 5.58 mm to 7.74 mm after follow-up. The correlation coefficient (CC) of increase of condylar height difference and development of MA was 0.681 (p < 0.05). Also, increase of menton deviation was significantly related to age of the patients (CC = -0.760, p < 0.05). CONCLUSION: The results show that UJADD result in asymmetric growth bilateral TMJs, especially condylar height, which was much shorter on the ipsilateral side. In the same time, MA got worse during the natural course of UJADD. It is concluded that UJADD was one of the major causative factors of MA.

Results of radiological follow-up of untreated anterior disc displacement without reduction in adolescents.

Our aim was to assess the progression of disease without treatment in adolescents with non-reducible anterior disc displacement (ADD) using serial magnetic resonance images (MRI). We retrospectively reviewed all patients under the age of 20 years who had unilateral non-reducible ADD and had had two MRI during a period of 6 months with no intervention. A total of 124 patients (101 female and 23 male) with a mean (range) age of 16 (10-20) years had 2 MRI at least 6 months apart (mean (range) 14 (6-47) months). At the initial visit there was a significant difference between the involved and the non-involved sides in the incidence of condylar degeneration and effusion (p=0.0001). The effusion significantly decreased despite the lack of intervention, the amount of disc deformation significantly increased (p=0.003), and the degree of condylar degeneration increased from 61%-69%, but this did not differ significantly. We conclude that during the period of observation there was a significant reduction in the incidence of effusion and significant increase in disc deformation. Whilst there was an increase in the changes on the condylar surface, this was not significant.

Multi-Space Infections in the Head and Neck: Do Underlying Systemic Diseases Have a Predictive Role in Life-Threatening Complications?

PURPOSE: To assess the incidence, risk factors, treatment, and outcomes of life-threatening complications of multi-space infections (LCMIs) in the head and neck. PATIENTS AND METHODS: This was a retrospective cohort study that enrolled a sample of patients with multi-space infections who were referred from February 2006 through July 2014. The patients were classified into LCMI and non-LCMI groups. The primary predictor in this study was underlying systemic disease. The primary outcome variable was LCMI. Univariate analyses were used for data statistics. RESULTS: A total of 549 patients were included, and an LCMI was found in 66 patients (12.20%). Descending mediastinitis was the most frequent LCMI (n = 37; 56.06%), followed by airway obstruction (n = 27; 40.91%), pneumonia (n = 12; 18.18%), pericarditis (n = 6; 9.09%), intraorbital infection (n = 2; 3.03%), multiple organ failure (n = 2; 3.03%), intracranial infection (n = 2; 3.03%), and sudden cardiac death (n = 1; 1.52%). Twelve patients with LCMI died during treatment. Elderly patients with an underlying systemic disease more commonly developed an LCMI. CONCLUSIONS: Multi-space infections in the head and neck can cause several life-threatening complications, and the morbidity of LCMI is considerable. Older age and underlying systemic disease can increase the risk of an LCMI.

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.

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

This 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.

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.

Pigmented villonodular synovitis of the temporomandibular joint with intracranial extension.

Pigmented villonodular synovitis is an uncommon benign tumor-like proliferative lesion with an undetermined origin. Involvement of the temporomandibular joint is uncommon. Although pigmented villonodular synovitis is a benign lesion, it can grow with an aggressive pattern, and it extends extra-articularly in most of the reported cases, about one-third of them exhibiting intracranial involvement. The authors reported an additional case of a 47-year-old woman with intracranial extension, who had a history of joint pain and trismus. The preoperative diagnosis was made with arthroscopy. The lesion was completely excised via preauricular approach and condylotomy. The bone defect was covered by the pedicled temporalis myofascial fat flap. The patient has been symptom-free for 40 months postoperatively.

Comparison of multi-space infections of the head and neck in the elderly and non-elderly people, part II: the influencing factors of the outcomes.

OBJECTIVE: This study aims to identify significant predictors of 3 outcomes in the aged patients and non-elderly with multi-space infections of the head and neck: the number of incisions, the length of hospital stay, and complications. PATIENTS AND METHODS: A retrospective study was conducted on 242 patients receiving treatment for severe multi-space infections of the head and neck region. Study variables were categorized as demographics, clinical parameters, and laboratory values. The outcome variables were the number of incisions, length of hospital stay, and complications. Multivariate linear and logistic regression techniques were used to measure associations between study variables and the outcome variables. Statistical analyses of the results between groups were performed using the Student t test and χ. RESULTS: Multivariate analyses, controlling for confounding variables, indicated that the number of spaces affected was a predictor of the number of incisions and complications in the elderly group. In the non-elderly group, the number of spaces affected was a predictor of the number of incisions and length of hospital stay. Admission blood glucose level and admission white blood cell count were the predictors of complications in the non-elderly. CONCLUSION: This study identifies different study variables as predictors of outcomes in treating multi-space infections of the head and neck in the elderly and non-elderly group. The number of spaces affected is the most important predictor.

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.

Disc positions and condylar changes induced by different stretching forces in the model for anterior disc displacement of temporomandibular joint.

OBJECTIVE: The aim of this study was to compare the disc positions and condylar changes induced by different stretching forces in the modified animal model for anterior disc displacement (ADD) of the temporomandibular joint. METHODS: In the experimental group, 30 rabbits were equally divided into 3 subgroups and underwent surgical ADD via different stretching forces: group A with 0.5 N, group B with 1 N, and group C with 2 N. In the sham group, 6 rabbits underwent the same surgery without the disc being pulled anteriorly. The diagnosis of ADD was made when the anterior band of the disc was located anteriorly to the articular eminence. Histologic and radiographic changes of the condyles were observed under light microscopy and micro-computed tomography scanning 1 week after surgery. RESULTS: The success rates of ADD were both 100% in groups B and C and 70% in group A. The correlations between the stretching force and severity of ADD, the stretching force and severity of cartilage changes, and the severity of ADD and cartilage changes were statistically significant (P < 0.01). The most advanced ADD and severest condylar changes were induced in group C. Condylar remodeling and scleroses were found in micro-computed tomography scans. CONCLUSIONS: The rabbit model for ADD has been successfully established in this study, which is feasible and minimally invasive. The stretching force of at least 1 N could induce the disc displaced successfully. Larger stretching force would induce severer ADD and condylar degenerative changes.

Ruptured disc after arthroscopic repositioning in the temporomandibular joint: a retrospective magnetic resonance imaging study.

Our aim was to explore the incidence of rupture after arthroscopic repositioning of the disc of the temporomandibular joint (TMJ) by reviewing magnetic resonance images (MRI) of the TMJ taken before and after operation, and to investigate correlations retrospectively. We studied 247 patients with anterior disc displacement of the TMJ, and categorised them into 3 groups based on the postoperative MRI. The first group comprised those whose disc ruptured after repositioning, the second those who had a possible rupture of the disc after repositioning, and the third had no rupture of the disc after repositioning. Age, sex, duration of symptoms, maximum incisal mouth opening, whether the anterior disc displacement was unilateral or bilateral, and the Wilkes stage, were included in the analysis. The incidence of rupture (5/247) was 2%. Weak points at the intermediate zone of the disc were found in 4 of the 5 joints. The patients whose discs ruptured were significantly younger than the other 2 groups (p=0.001). There was no statistically significant difference in preoperative duration of symptoms and mouth opening among the groups. The proportions of unilateral and bilateral disc displacement (p=0.047) and Wilkes stage (p=0.027) differed among the 3 groups. The Wilkes stages was significantly more advanced in the ruptured group than in the other 2 groups (p=0.027) with 4/5 being bilateral. The weak point in the intermediate zone of the disc on MRI could be a sign of rupture. Teenagers and young adults with anterior disc displacement without reduction, particularly those in whom it is bilateral, are at a higher risk of a rupture after repositioning of the disc by arthroscopy.

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 People's 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.