Xuchen Ma

Long-term efficacy of botulinum toxin type A for the treatment of habitual dislocation of the temporomandibular joint.

Injection of botulinum toxin type A (BTX-A) into the lateral pterygoid muscles is a recently reported treatment for habitual dislocation of the temporomandibular joint (TMJ). We report five cases of dislocation in elderly patients with neurological or other severe systemic disease, and their successful treatment with one injection of BTX-A into the lateral pterygoid muscles. This is a relatively conservative option. Injection into the muscle is straightforward and can be done in outpatients with few complications. We recommend it as the first choice for patients with habitual dislocation and systemic or neurological diseases, particularly in the elderly.

Investigation of the clinical and radiographic features of osteoarthrosis of the temporomandibular joints in adolescents and young adults.

OBJECTIVE The objective of this study was to investigate the clinical and radiographic features of osteoarthrosis (OA) of the temporomandibular joints (TMJOA) in human adolescents and young adults. STUDY DESIGN Patients (n = 4883) with temporomandibular disorders (age, 11 to 30 years) underwent clinical and radiographic examinations. The radiographic findings were classified as erosive bony changes, proliferative changes mainly, including flattening with uneven sclerosis, and osteophytes of the condyle, and bilaterally short condylar processes. In addition, we interpreted the reassessment radiographs of 156 of the patients. RESULTS Seven hundred eleven patients had radiographic signs of OA. The frequency of OA was higher in women (563/3360, 16.8%) than in men (148/1523, 9.7%). Most patients (541/711, 76.1%) with signs of OA showed proliferative changes of OA. Moreover, 56.4% of patients with TMJOA (88/156) remained stable. CONCLUSIONS These results suggest that although OA is an age-related disease, aging is not the crucial factor in the pathogenesis of OA.

Detection accuracy of in vitro approximal caries by cone beam computed tomography images

AIMS To evaluate the diagnostic accuracy of approximal carious lesions among five CBCT systems and to assess the effect of detector types employed by different CBCT systems on the accuracy of approximal caries diagnosis. MATERIALS AND METHODS Thirty-nine extracted non-cavitated human permanent teeth were employed in the study. Seven observers evaluated 78 approximal surfaces of the teeth with respect to caries by the images from the following five CBCT systems: (1) NewTom 9000; (2) Accuitomo 3DX; (3) Kodak 9000 3D; (4) ProMax 3D; and (5) DCT PRO, respectively. The lesions were validated by histological examination. The area under receiver operating characteristic (ROC) curve (A(z)) was used to evaluate the diagnostic accuracy. RESULTS Microscopy of approximal surfaces found 47.4% sound, 39.8% enamel and 12.8% dentin lesions. The differences of A(z) values among the five CBCT systems were not statistically significant (p=0.348). No significant difference was found between the two detector types of CBCT systems (p=0.47). CONCLUSIONS The five CBCT systems employed in the study showed no significant difference in the in vitro approximal caries detection. Neither the detector nor the FOV employed by the CBCT systems has an impact on the detection accuracy of approximal caries.

The detection accuracies for proximal caries by cone-beam computerized tomography, film, and phosphor plates

OBJECTIVES To evaluate the accuracy of cone-beam computerized tomography (CBCT) for the detection of noncavitated proximal caries and to compare the detection accuracies of 2 CBCT imaging systems with those based on plain-film radiographs and phosphor-plate images. STUDY DESIGN Test radiographs of 39 noncavitated unrestored human permanent teeth were obtained with film, phosphor-plate, ProMax 3D, and Kodak 9000 3D imaging systems. Seven observers used a 5-level scale to evaluate test images for the presence of proximal caries. With histologic examination serving as the reference standard, observer performances were assessed with receiver operating characteristic (ROC) curves, and the areas under the ROC curves (A(z) values) for the observers, and modalities were analyzed with a repeated-measures analysis of variance. RESULTS The mean A(z) values for film, phosphor plates, ProMax 3D, and Kodak 9000 3D imaging systems were 0.541, 0.523, 0.528, and 0.525, respectively (P = .763). CONCLUSION For detecting subtle noncavitated proximal caries, the detection accuracy with the CBCT images was little better than chance performance and was similar to that with phosphor plate- and film-based intraoral images.

Clinical and radiologic findings of synovial chondromatosis affecting the temporomandibular joint

OBJECTIVES Our aim was to study the clinical and radiologic findings of synovial chondromatosis (SC) affecting the temporomandibular joint (TMJ) and provide references for diagnosis and treatment. STUDY DESIGN Twenty patients confirmed as SC histopathologically were included in the investigation. Nineteen cases were treated with arthrotomy and 1 case with arthroscopy. The clinical manifestations, radiographic findings, histopathologic features, surgical treatment, and differential diagnosis were combined to study this disease. The SC features of TMJ on magnetic resonance (MR) images were summarized on proton density-weighted (PD) and T2-weighted images. RESULTS Synovial chondromatosis of TMJ occurred more often in women and on the right. Symptoms included preauricular pain, swelling, limitation of mouth opening, crepitations, and deviation on opening. The detection rate of calcified loose bodies was 30% on conventional radiographs and 53.3% on computerized tomography. Multiple small ring-like or tubular signals could be seen on PD and T2-weighted MR images. SC mainly affected the superior joint space; it could involve the inferior space when a perforated or deformed disc was present. SC could extend into intracranial fossa, infratemporal fossa, and lateral pytergoid muscle. CONCLUSIONS The characteristic ring-like signals could be found on MR images of the patients with SC of TMJ. This lesion should be differentially diagnosed with TMJ disorders and preauricular masses. Considering its recurrence and the different behavior of SC in different patients, various treatment strategies should be considered.

Thyroid shields for radiation dose reduction during cone beam computed tomography scanning for different oral and maxillofacial regions

AIMS To evaluate the radiation dose level during cone beam computed tomography (CBCT) scanning for the different oral and maxillofacial regions with and without thyroid collar shielding. MATERIALS AND METHODS Average tissue-absorbed dose for a DCT PRO CBCT was measured using thermoluminescent dosimeter chips in a phantom with or without applying thyroid collars. Effective organ dose and total effective dose were derived using International Commission on Radiological Protection (ICRP) 2007 recommendations. RESULTS The total effective doses for large, middle and small field of view (FOV) were 254.3 μSv, 249.0 μSv and 180.3 μSv, respectively, when no thyroid collar was used. Applying one thyroid collar around the front neck can reduce the total effective doses to 208.5 μSv (18.0% reduction), 149.1 μSv (40.1% reduction) and 110.5 μSv (38.7% reduction), respectively. When two thyroid collars were used around the front and back neck, the total effective doses were reduced to 219.1 μSv (13.8% reduction), 142.0 μSv (43.0% reduction) and 105.5 μSv (41.5% reduction), respectively. CONCLUSIONS Thyroid collar can reduce the radiation dose during CBCT scanning for the oral and maxillofacial regions. The dose reduction becomes more significant when middle or small FOV is chosen.

Dose reduction of cone beam CT scanning for the entire oral and maxillofacial regions with thyroid collars

OBJECTIVE The aim of this study was to evaluate the influence of thyroid collars on radiation dose during cone beam CT (CBCT) scanning. METHODS Average tissue-absorbed dose for a NewTom 9000 CBCT scanner (Quantitative Radiology, Verona, Italy) was measured using thermoluminescent dosemeter chips in a phantom. The scans were carried out with and without thyroid collars. Effective organ dose and total effective dose were derived using International Commission on Radiological Protection 2007 recommendations. RESULTS The effective organ doses for the thyroid gland and oesophagus were 31.0 µSv and 2.4 µSv, respectively, during CBCT scanning without a collar around the neck. When the thyroid collars were used loosely around the neck, no effective organ dose reduction was observed. When one thyroid collar was used tightly on the front of the neck, the effective organ dose for the thyroid gland and oesophagus were reduced to 15.9 µSv (48.7% reduction) and 1.4 µSv (41.7% reduction), respectively. Similar organ dose reduction (46.5% and 41.7%) was achieved when CBCT scanning was performed with two collars tightly on the front and back of the neck. However, the differences to the total effective dose were not significant among the scans with and without collars around the neck (p = 0.775). CONCLUSIONS Thyroid collars can effectively reduce the radiation dose to the thyroid and oesophagus if used appropriately.

Age estimation based on pulp chamber volume of first molars from cone-beam computed tomography images

AIM To establish a method that can be used for human age estimation on the basis of pulp chamber volume of first molars and to identify whether the method is good enough for age estimation in real human cases. MATERIALS AND METHODS CBCT images of 373 maxillary first molars and 372 mandibular first molars were collected to establish the mathematical model from 190 female and 213 male patients whose age between 12 and 69 years old. The inclusion criteria of the first molars were: no caries, no excessive tooth wear, no dental restorations, no artifacts due to metal restorative materials present in adjacent teeth, and no pulpal calcification. All the CBCT images were acquired with a CBCT unit NewTom VG (Quantitative Radiology, Verona, Italy) and reconstructed with a voxel-size of 0.15mm. The images were subsequently exported as DICOM data sets and imported into an open source 3D image semi-automatic segmenting and voxel-counting software ITK-SNAP 2.4 for the calculation of pulp chamber volumes. A logarithmic regression analysis was conducted with age as dependent variable and pulp chamber volume as independent variables to establish a mathematical model for the human age estimation. To identify the precision and accuracy of the model for human age estimation, another 104 maxillary first molars and 103 mandibular first molars from 55 female and 57 male patients whose age between 12 and 67 years old were collected, too. Mean absolute error and root mean square error between the actual age and estimated age were used to determine the precision and accuracy of the mathematical model. The study was approved by the Institutional Review Board of Peking University School and Hospital of Stomatology. RESULTS A mathematical model was suggested for: AGE=117.691-26.442×ln (pulp chamber volume). The regression was statistically significant (p=0.000<0.01). The coefficient of determination (R(2)) was 0.564. There is a mean absolute error of 8.122 and root mean square error of 5.603 between the actual age and estimated age for all the tested teeth. CONCLUSION The pulp chamber volume of first molar is a useful index for the estimation of human age with reasonable precision and accuracy.

Diagnostic accuracy of parotid CT for identifying Sjögren's syndrome

PURPOSE To evaluate the diagnostic accuracy of computed tomography (CT) of the parotid gland for Sjögrens syndrome in comparison with conventional X-ray sialography. METHODS CT scans and X-ray sialography were performed in 34 patients with confirmed Sjögrens syndrome and 22 symptomatic controls without the disease. CT data from 57 asymptomatic controls were included for quantitative analysis. The CT findings of heterogeneity, abnormal diffuse fat tissue deposition, diffuse punctate calcification, swelling or atrophy, nodularity or cystic changes of the parotid gland were analyzed by two independent blinded readers. The correlation between CT and X-ray sialography findings was evaluated. Diagnostic performance and receiver operating characteristics curves were calculated. RESULTS On CT, heterogeneity of the parotid gland was seen in 30/31 (reader 1/reader 2) Sjögrens syndrome patients by the two readers (sensitivity 88.2%/91.2%; specificity 100%/90.9%). Abnormal diffuse fat tissue deposition was seen in 28/28 SS patients by the readers (sensitivity 82.3%/82.3%; specificity 100%/90.9%). Diffuse punctate calcification was seen in 10/12 Sjögrens syndrome patients (sensitivity 29.4%/35.2%; specificity 100%/100%). Stagings of CT findings correlate positively with sialography. The areas under the receiver operating characteristics curves were 0.887 (P=0.000) and 0.908 (P=0.000) for the maximum and standard deviation (SD) of the CT value. CONCLUSIONS Parotid CT is accurate and reliable in the diagnosis of Sjögrens syndrome. Heterogeneity, abnormal diffuse fat tissue deposition, and diffuse punctate calcification are specific for Sjögrens syndrome. CT attenuation analysis is helpful in diagnosis.

Detection accuracy of proximal caries by phosphor plate and cone-beam computerized tomography images scanned with different resolutions.

This study was carried out to assess whether the spatial resolution has an impact on the detection accuracy of proximal caries in flat panel CBCT (cone beam computerized tomography) images and if the detection accuracy can be improved by flat panel CBCT images scanned with high spatial resolution when compared to digital intraoral images. The CBCT test images of 45 non-restored human permanent teeth were respectively scanned with the ProMax 3D and the DCT Pro scanners at different resolutions. Digital images were obtained with a phosphor plate imaging system Digora Optime. Eight observers evaluated all the test images for carious lesion within the 90 proximal surfaces. With the histological examination serving as the reference standard, observer performances were evaluated by receiver operating characteristic (ROC) curves. The areas under the ROC curves were analyzed with two-way analysis of variance. No significant differences were found among the CBCT images and between CBCT and digital images when only proximal enamel caries was detected (p = 0.989). With respect to the detection of proximal dentinal caries, significant difference was found between CBCT and digital images (p < 0.001) but not among CBCT images. The spatial resolution did not have an impact on the detection accuracy of proximal caries in flat panel CBCT images. The flat panel CBCT images scanned with high spatial resolution did not improve the detection accuracy of proximal enamel caries compared to digital intraoral images. CBCT images scanned with high spatial resolutions could not be used for proximal caries detection.