Anatomical modifications of the temporomandibular joint during ageing

Perforation of the temporomandibular joint disc: cadaveric anatomical study

The aim of this human cadaveric study was to investigate the relationship between temporomandibular joint disc perforation and bony changes of the mandibular condyle. Overall, 135 cadaveric mandibles were used (69 male, 66 female; all White). Mean age at death was 78.7 years. Perforation of the disc was investigated. Differences in the area of the perforation according to the different types of bony change (erosion, flattening, osteophyte) were evaluated. Perforation of the disc was observed in 34.8% of all mandibles, occurring unilaterally in 53.2% of cases and bilaterally in 46.8%. The prevalence of perforation was 16.4% in cadavers <80 years old (67 heads) and 52.9% in those ≥80 years old (68 heads) (P < 0.001). Osteophyte formation was always identified along with other bony changes (21.7%) and never in isolation. The area of the perforation was significantly larger in the groups with bony changes (one, two, or three changes) than in the 'no bony change' group. The group with osteophyte formation showed a significantly larger perforated area than the group without osteophyte formation; likewise, the group with flattening showed a significantly larger perforated area than the group without flattening. Osteophytes and flattening are probably secondary bony changes that occur following disc perforation. Based on this study, disc perforation should be suspected when these findings are identified on imaging.

Effect of region-dependent viscoelastic properties on the TMJ articular disc relaxation under prolonged clenching

The disc of the temporomandibular joint (TMJ) is located between the mandibular condyle and temporal bone, and has an important load-bearing and stress absorbing function. The TMJ disc presents viscoelastic characteristics that are largely dependent on its collagen fibre and proteoglycan composition and organization. The purpose of this study is to investigate the possible effects of region-specific dynamic viscoelastic properties on stress relaxation during prolonged clenching. Two finite element models were used to compare the stress distribution within the TMJ disc, namely, one with uniform disc material property and another one with region-specific disc material properties. Similar results were observed in both models with slight differences in the location of maximum stress. Larger stresses were observed in all cases for the model with uniform disc material property. Moreover, the higher values for the model with uniform disc material property appeared in the lateral region, while in the model with region-specific disc properties, these values moved to the lateral and central region. This investigation confirms that both models are sufficiently accurate to investigate stress distribution in the TMJ disc, and, particularly, the model with the region-specific disc material properties ensure better simulations of the TMJ disc behaviour.

Full Facial Allotransplantation Including the Temporomandibular Joints: A Radiologic and Anatomical Cadaveric Study

BACKGROUND

Facial allotransplantation including the temporomandibular joints may improve the functional outcomes in face transplant candidates who have lost or damaged this joint.

METHODS

Linear and angular measurements were taken in 100 dry skulls and mandibles and in 100 three-dimensionally-reconstructed facial computed tomographic scans to determine the variability of the temporomandibular joint, glenoid fossa, and mandible. A vascular study was performed in six fresh cadaveric heads, followed by harvest of the face allograft in three heads. Next, four heads were used for mock transplantation (two donors and two recipients). The full facial allograft included four different segments: a Le Fort III, a mandibular tooth-bearing, and two condyle and temporomandibular joint-bearing segments. Statistical analysis was performed using SAS software.

RESULTS

In only one-third of the skulls, the condylar shape was symmetric between right and left sides. There was a wide variability in the condylar coronal (range, 14.3 to 23.62 mm) and sagittal dimensions (range, 5.64 to 10.96 mm), medial intercondylar distance (range, 66.55 to 89.91 mm), and intercondylar angles (range, 85.27 to 166.94 degrees). This high variability persisted after stratification by sex, ethnicity, and age. The temporomandibular joint was harvested based on the branches of the superficial temporal and maxillary arteries. The design of the allograft allowed fixation of the two condyle and temporomandibular joint-bearing segments to the recipient skull base, preserving the articular disk-condyle-fossa relationship, and differences were adjusted at the bilateral sagittal split osteotomy sites.

CONCLUSION

Procurement and transplantation of a temporomandibular joint-containing total face allograft is technically feasible in a cadaveric model.

Shear Wave Elastography in the Evaluation of Temporomandibular Joint Disorders

We aimed at verifying the usefulness of shear wave elastography in determining the temporomandibular disc stiffness in patients with a temporomandibular disorders (TMDs). The study included 37 patients with confirmed TMDs and 208 healthy volunteers. Patients presented with significantly greater stiffness of the intermediate zone of the disc (region of interest [ROI] 1) and significantly lower stiffness of its anteriorly displaced portion (ROI 3). A receiver operating characteristics analysis indicated that a decrease in the stiffness in ROI 3 less than 8.667 KPa provided 100% sensitivity, 97.3% specificity, 100% positive predictive value (PPV) and 99.5% negative predictive value (NPV) in distinguishing between patients with TMDs and without. Whereas an increase in ROI 1 stiffness to at least 54.33 KPa provided high specificity and NPV, both the sensitivity and the PPV of this predictor equaled zero. Findings suggest that a decrease in anteriorly dislocated disc stiffness less than 8.667 kPa can accurately identify patients with TMDs.

Biometry of the temporomandibular joint using computerized tomography

PURPOSE

In the present study, we performed biometric characterization of the temporomandibular joints (TMJs) of clinically normal subjects.

METHODS

Fifty-one healthy volunteers underwent high-resolution computerized tomography examination of the TMJs in the position of maximal intercuspidation according to a standardized protocol. Frontal and sagittal reconstructions were then performed to obtain measurements and indexes in three planes of space.

RESULTS

Correlations are observed with age, gender, amplitude of mouth opening and presence of dental abrasion. The lateral stability index reflects the degree of mobility of the temporo-discal compartment of the joint. The coverage index reflects how much the mandibular condyle is inserted into the articular fossa and may be related to the risk of occurrence and severity of regressive remodeling phenomena.

CONCLUSIONS

This study supports the interest in examining morphological aspects of the TMJ and performing intra-articular measurements. The biometric examination of the TMJ has important applications in the domain of TMJ pathology.

Apoptosis in displaced temporomandibular joint disc with and without reduction: an immunohistochemical study

Internal derangement (ID) of the temporomandibular joint (TMJ) is due to an abnormal relationship of the articular disc to the mandibular condyle, glenoid fossa and articular eminence. The two most common types of internal derangement are anterior disc displacement with (ADDwR) and without reduction (ADDwoR). Disc displacement is associated with degenerative tissue changes. The histological features of discs from patients with TMJ ID reflect a general remodelling caused by abnormal loading. A correlation has been demonstrated between TMJ ID and apoptosis. Few investigations have addressed the role of apoptosis or caspase activity in TMJ ID. The apoptosis activation process was studied in different areas of discs from 18 patients with ID (both ADDwR and ADDwoR) and four cadavers (controls), with emphasis on the expression of caspase 3, whose activation makes the death process irreversible. The results showed a greater proportion of caspase 3-positive cells in ADDwR and ADDwoR than in control discs. Immunopositivity also varied between disc areas; in particular, in ADDwoR sections labelled cells were significantly more numerous (P < 0.01) in the posterior disc attachment than in the anterior and intermediate bands. In addition, a significantly greater proportion of labelled cells was seen in the anterior (+) and intermediate (++) band of ADDwR compared with ADDwoR discs both bands (P < 0.05). These data suggest the importance of programmed cell death in the progression of TMJ ID.

Impact of postmenopausal osteoporosis on the oral and maxillofacial surgery patient

With aging, there is a loss of skeletal mass in women and men, but the rate of loss accelerates in perimenopausal women. With the loss of bone mass there is increased risk for fracture in the axial and appendicular skeleton. The mandible and maxilla also experience age-related declines in some parameters of architecture and trabecular pattern, but those do not seem to be directly associated with fracture risk. Although the literature is controversial regarding the generalizability of the impact of systemic osteoporosis on the oral/maxillofacial patient, it is prudent to give consideration to an individual patient's osteoporosis status, risk, and anti-osteoporosis therapies when planning oral and maxillofacial surgical procedures.

Factors affecting the variation in the adult temporomandibular joint of archaeological human populations

To elucidate factors that may affect the variation in the bony components of temporomandibular joint (TMJ), a preliminary study was conducted on the temporal articular surface of the TMJ of 30 skulls from Iron Age and medieval populations from Lithuania and a mixed Neolithic and Bronze Age population from the Central Elbe-Saale region (CESR). Using three-dimensional (3D) photos of the skulls, length and width measurements of the TMJ were obtained and compared with external skull measurements. Distinct, random variation between the TMJ values from opposite sides of the cranium were identified as fluctuating asymmetry. ANOVA results suggest significant differences in the length of the TMJ between the population of the CESR and the two Lithuanian populations, but not between the two Lithuanian populations. Environmental factors, including geography, may be responsible for the variation in the TMJ form.