Carol A. Bibb

Relationship of TMJ Articular Soft Tissue to Underlying Bone in Young Adult Condyles

This investigation used a histological model to study the relationship of articular soft-tissue thickness and contour to the underlying bone in the TMJ condyle of young adults. The usefulness of selected dental and demographic factors in the prediction of the articular soft-tissue thickness and contour was also tested. One sagittal histological section was studied from the lateral, central, and medial thirds of 53 left mandibular condyles. Outline tracings of the articular and compact bone surface were divided into anterior, superior, and posterior sectors for the study of curvature measured by the overlaying of a template of a harmonic series of arcs. The thickness and composition of the articular tissues were measured in each sector by light microscopy. The fibrous connective tissue layer always maintained the articular surface, even in the absence of a cartilage layer. The histological character, including the presence or absence of cartilage, rather than the overall tissue thickness, was considered to be a more useful marker of functionally stimulated changes in the joint. Articular soft-tissue thickness was not related to surface deviation in form and was not correlated with age in this young adult sample. Reduced soft-tissue thickness in the anterior part of the condyle was more common in cases with lack of molar support. Dental attrition was not a useful predictor of soft-tissue thickness. Compact bone contour correlated with soft-tissue contour in the superior (r = 0.816) and posterior (r = 0.808) sectors, explaining only 64% of the variance, but not in the anterior sector (r = 0.265). Thicker or thinner articular soft tissue was not predictable by the underlying compact bone contour or thickness. Therefore, the clinician should not automatically assume that the radiographic osseous image represents the actual articular surface.

Serial variation in histological character of articular soft tissue in young human adult temporomandibular joint condyles

Histological variation was studied in serial sections, in contrast to previous studies which have generalized from representative sections. The sample consisted of consecutive serial sagittal sections from the central third of nine condyles, plus an accompanying stone cast showing the intact articular surface before sectioning. The thickness of the articular soft tissue and its fibrous connective tissue and cartilage components was measured, and the presence of undifferentiated mesenchymal (UM) cells was assessed by low-power light microscopy. Components of variance analysis showed that section-to-section variation in thickness was of the same order as differences between joints, each explaining approx. 50% of the variance in both connective tissue and cartilage thickness. The fibrous connective tissue contributed as much to the overall variation in soft tissue thickness as did the cartilage component (SD 0.0946 versus 0.0909 mm for the superior sector). Serial UM cell variability was common, and the UM cells were often distributed in islands rather than uniformly across the articular tissue. Condyles with the greatest surface irregularity were characterized by greater serial variability in fibrous connective tissue thickness, more frequent absence of cartilage, and more areas of UM cell depletion. These results suggest that serial variation in histological character may be more important than mean values in the description of surface contours and articular tissue relations in the temporomandibular joint. This should influence the design of future investigations.

The Relationship of Undifferentiated Mesenchymal Cells to TMJ Articular Tissue Thickness

Undifferentiated mesenchymal (UM) cells, the progenitor cells of the cartilage layer, have been assigned a significant role in TMJ articular tissue maintenance. This was based on reports of UM cell reduction with increased soft-tissue thickness for the condyle and temporal component. However, the strength of this inverse relationship was not presented and remained unclear. The purpose of the present study was to assess the strength of the correlation between UM cell presence and soft-tissue thickness in young adult TMJs at autopsy. Sagittal histological sections from the central thirds of 50 joints were evaluated with respect to articular soft-tissue thickness, histological character, and UM cell presence in the condyle and temporal component. The superior sector ofthe condyle and the articular eminence showed the greatest variability in soft-tissue thickness and were the only areas to show localized UM cell absence. The eminence was the only location to show an inverse relationship between soft-tissue thickness and UM cell presence, and this was consistent in both an ANOVA (p = 0.0016) and a Spearman correlation analysis. However, the strength of this correlation was only moderate (rho = -0.52), and no such relationship was observed in any other location. This study suggests that the relationship between UM cell presence and soft-tissue thickness is more complex than previously hypothesized and that the contribution of UM cells to articular tissue maintenance has been overstated, while other biological processes were overlooked.

Contour mapping of the TMJ temporal component and the relationship to articular soft tissue thickness and disk displacement

The osseous architecture of central sagittal histologic sections of the temporal component of 51 temporomandibular joints of young adults at autopsy was studied to determine if this predicted the thickness of the overlying articular soft tissue and disk displacement. Geometric groupings of fossa-eminence shapes were generated using a hierarchical cluster analysis of the osseous fossa-eminence sigmoid curve, size, and slope. Six cluster groups were evolved and tested for relationship to soft tissue thickness measured at the eminence crest, mid-point of the eminence slope, closed pack location of the condyle, the inflection point, and the depth of the fossa. Soft tissue thickness at the inflection point and depth of the fossa was remarkably constant between cluster groups. Increased soft tissue thickness at the eminence crest and lower part of the posterior slope was weakly correlated to a flatter eminence slope and curve, explaining 10% to 20% of the variance (r2). There were no relationships between the parameters studied to the fossa curvature. An ANOVA showed no statistical difference in the posterior slope angle between the categories of disk position (p = 0.715) or to the six cluster groupings. The results suggest that the osseous contours seen on radiographs may not accurately predict the actual articular surface of the temporal component.

Temporomandibular joint comparative imaging: Diagnostic efficacy of arthroscopy compared to tomography and arthrography

This comparative imaging study of the TMJ was conducted to examine the diagnostic data obtained from arthroscopy as compared to data from tomography and arthrography. Six joints from cadaver material were imaged by each technique and subsequently dissected. Each technique had value, but none was comprehensive. Tomography was the technique of choice for imaging osseous changes. Double joint space arthrotomography was useful for examining articular disk position and morphology. Diagnostic arthroscopy, through direct visualization of surface morphology, showed localized surface pathosis, such as synovitis; provided data on the location and size of disk perforations; and contributed reliably to a diagnosis of disk displacement on the basis of associated pathosis such as stretching of the posterior attachment.

Relationship of articular soft tissue contour and shape to the underlying eminence and slope profile in young adult temporomandibular joints

This study examined whether the overall shape of the articular soft tissue overlying the posterior slope and articular eminence of the temporal bone could be predicted by the underlying osseous contour in a histologic model of 51 central sagittal sections of young adult temporomandibular joints. Articular soft tissue and bone contours were traced, and osseous landmarks identified on the basis of joint geometry. Soft tissue thickness measurements were made under low power light microscopy. Seven categories of articular soft tissue pattern were identified. The soft tissue uniformly followed the osseous contour in only one (14%). A progressive increase in soft tissue thickness from the middle of the posterior slope to the articular crest was the most common pattern (35%) but did not describe most of the sample that was more asymmetric. Pattern was poorly predicted by the shape and slope of the temporal bone outline or by dental factors that describe anterior guidance and did not relate to disk displacement. The articular soft tissue compensated for flatter eminence slopes and osseous irregularities and maintained an intact surface. This study has clinical implications for radiographic interpretation of disk space, condyle translation pathways, and the integrity of the functional articular surface.