Differences between the temporal and mandibular components of the temporomandibular joint in topographic distribution of osseous degenerative features on cone-beam computerized tomography.

BACKGROUND/PURPOSE: Temporomandibular joint osteoarthritis (TMJOA) pathology is characterized by degenerative changes of the subchondral bone. The topographic distribution of osseous degenerative changes in TMJ is not clear. This study aimed to evaluate the topographic distribution of osseous degenerative features in the TMJ by using cone-beam computerized tomography (CBCT). MATERIALS AND METHODS: The CBCT images of 26 female patients diagnosed to have TMJOA were retrieved from the database of the National Taiwan University Hospital. The images of left and right TMJs were evaluated independently by 2 examiners. The evaluated degenerative features included surface erosion, subcortical cysts, subcortical sclerosis, and osteophytes in the mandibular condyle and temporal component of the TMJ. The topographic distribution at different portions in the mandibular condyle and temporal component of the TMJ was statistically analyzed. RESULTS: Significant differences in the topographic distribution of the osseous degenerative features were observed (a) between the mandibular condyle and the temporal component and (b) between the anterior/central portion and posterior portion of the temporal component. No significant differences were observed in the topographic distribution of the TMJOA features in the condyle, except for surface erosion between the central and lateral portion of the condyle. CONCLUSION: The results suggest that the mandibular condyle and temporal component react differently in TMJ osseous degeneration, with the condyle being more vulnerable than the temporal component. Mandibular activities that require the mandibular condyle to function outside the fossa may be more destructive to the health and integrity of the TMJ.

The advantage of cone-beam computerized tomography over panoramic radiography and temporomandibular joint quadruple radiography in assessing temporomandibular joint osseous degenerative changes.

BACKGROUND/PURPOSE: The clinical diagnosis of temporomandibular joint (TMJ) degenerative joint disease (DJD) is based primarily on radiographic features of the condyle and articular eminence. The purpose of this study was to compare the reliability, sensitivity, and specificity of using plain radiography to that of cone-beam computerized tomography (CBCT) in identifying different types of osseous degenerative features in the TMJ condyle. MATERIALS AND METHODS: The panoramic radiography (PANO), TMJ quadruple radiography (TMJQR) and CBCT images of 29 patients' TMJs were retrieved from a computer database and independently evaluated by a young oral surgeon and a senior TMD specialist. The examiners diagnosed osseous degenerative features on the radiographic images. The radiologist-assisted CBCT diagnoses were used as a reference standard and the reliability, sensitivity, and specificity of using the three radiographic modalities were statistically analyzed. RESULTS: There were cases of indeterminate diagnoses using the PANO and TMJQR due to superimposition from surrounding structures, but none using CBCT. Reliability was generally poor when using PANO and TMJQR for detecting osseous degenerative features of the TMJ condyle but good to excellent when using CBCT. The sensitivity and specificity in the use of PANO and TMJQR were typically below acceptable, but the levels were generally satisfactory when using CBCT. CONCLUSION: CBCT is superior to plain radiographic modalities for diagnosing osseous degenerative features of TMJs with regard to indeterminate cases, reliability, sensitivity, and specificity. It is recommended that CBCT can be used as an effective tool in identifying TMJ osteoarthritis.

Effects on craniofacial growth and development of unilateral botulinum neurotoxin injection into the masseter muscle.

INTRODUCTION: The effects of botulinum neurotoxin type A (BoNT/A) on masseter muscles, when injected for cosmetic purposes (volumetric reduction) or treatment of excessive muscle activity (bruxism), have been investigated. However, the full anatomic effects of treatment are not known, particularly with respect to the mandible and relevant anthropometric measurements. The intent of this study was to use unilaterial BoNT/A injections to induce localized masseter atrophy and paresis and then to measure the effects of muscle influence on craniofacial growth and development. METHODS: Growing male Wistar rats, 30 days old, were studied. The experimental group consisted of 8 rats. One side of the masseter muscle was injected with BoNT/A and the other side of the masseter muscle was injected with saline. The side with BoNT/A belonged to 1 group and the side with saline was the sham group. Three rats without injections was the control. After 45 days, the masseter muscles were dissected and weighed. Dry skulls were prepared, and anthropometric measurements determined. RESULTS: One-way ANOVA showed that the animals maintained their weight in both groups; however, the muscles injected with BoNT/A were smaller than the sham or control muscles. Anthropometric measurements of the bony structures attached to the masseter muscle showed a significant treatment effect. CONCLUSIONS: After localized masseter muscle atrophy induced by BoNT/A injection, alterations of craniofacial bone growth and development were seen. The results agree with the functional matrix theory that soft tissues regulate bone growth.

Radiolocalized sentinel lymph node biopsy in squamous cell carcinoma of the oral cavity and analysis of various parameters.

BACKGROUND: Sentinel lymph node (SLN) biopsy seems to be a method that solves the problem of neck management with oral squamous cell carcinoma. Using blue dye methods for detection of neck SLNs from the surface of the operative field seems difficult; therefore, we used radiolocalization alone to detect and extract sentinel nodes. Aside from the various histological and clinical parameters examined in this procedure, we also determined whether they had any clinical significance in relation to the detection of SLNs during the operation. METHODS: Enrolled subjects had preoperative clinical N0 stage squamous cell carcinoma of the oral cavity and had received an unfiltered (99m)Tc sulfur colloid peritumoral injection. Localization of the SLNs was performed by using lymphoscintigraphy and a handheld gamma probe. RESULTS: In total, 28 oral squamous cell carcinoma patients were included in this prospective study. Sixty-four SLNs in 27 patients were identified by this method. The identification rate was 96.4%. No false-negative predictions of SLN were noted among any of the patients studied. The numbers of the SLNs found during the operation were larger in patients with positive findings than those with negative findings (P < .05 by the Mann-Whitney U-test). CONCLUSIONS: SLN radiolocalization provided an acceptable identification rate. The cases of positive findings for metastasis seemed to statistically have more SLNs than did those with negative findings, but more evidence is needed to prove this point. Therefore, SLN biopsies for extracting all possible high-risk nodes may be conducive for oral squamous cell carcinoma surgery.

Evaluation of loading conditions on fatigue-failed implants by fracture surface analysis.

PURPOSE: The goal of this study was to determine the relationship between fracture surface morphology and applied stress level for dental abutment screws loaded in cyclic fatigue. If a correlation between fracture surface and load level can be determined, then the fracture surface analysis could be used as a tool to assess the mechanism by which a screw failed and the magnitude of the load at which it failed. MATERIALS AND METHODS: Test implants were loaded with static and cyclic forces. In the cyclic test, the load versus the number of cycles was plotted as a curve for biomechanical analysis. The fracture surfaces of the failed screws were observed and recorded using scanning electron microscopy (SEM). RESULTS: Two fracture phases, a smooth region and a rough region, were observed on the fracture surface. After identifying the boundary between the 2 regions, the smooth region ratio (SRR), the ratio of the smooth phase area to the area of the whole fracture surface, was measured using digitized SEM images. The mean SRRs were 0.60 +/- 0.03, 0.66 +/- 0.03, and 0.75 +/- 0.03 when the tested implants were subjected to dynamic loading of 60%, 55%, and 50% ultimate failure loading (UFL), respectively. Linear relationships were found between the SRR values and loading magnitude and between SSR and number of cycles. DISCUSSION: The smooth area on the fracture surface can be used to assess the load conditions and internal stress of fatigue-fractured implants. CONCLUSIONS: These results demonstrate that fracture surface analysis of fractured implants has the potential to become a useful indicator for assessing implant fracture mechanisms.