The elastic moduli have not been reported for cancellous bone from the edentulous mandible. Accurate values are needed for finite element modeling of the mandible. The aim of this study was to determine elastic modulus values in three orthogonal directions for cancellous bone taken from an edentulous jaw and to relate these values to apparent density and volume fraction. Seven samples were obtained from the edentulous mandible of a 74-year-old female. Young's modulus was determined by compression testing of cubes cut with the faces aligned with the anatomic axes. Bone volume fraction averaged 0.33 (SD 0.14) and apparent density averaged 0.55 g/cc (SD 0.29). Young's modulus was greatest in the mesio-distal direction (mean 907 MPa, SD 849 MPa), followed by the bucco-lingual (mean 511 MPa, SD 565 MPa) and infero-superior direction (mean 114 MPa, SD 78 MPa). The infero-superior direction was less than the bucco-lingual (P = 0.03) and mesio-distal (P = 0.002). The mesio-distal and bucco-lingual directions could not be shown to be different (P = 0.32). This suggests a model of transverse isotropy for cancellous bone in the jaw, where the symmetry axis is along the infero-superior (weakest) direction.
Objectives: To compare the diagnostic accuracy of conventional film, unenhanced direct digital and inversion grayscale direct digital imaging in the detection of approximal caries. Methods: 150 approximal surfaces of extracted permanent molars and premolars were selected for the study on the basis of varying lesion depth. The teeth were radiographed using Ektaspeed Plus film; digital images were made with a Schick CMOS-APS sensor. 7 examiners evaluated 58 randomized images of each modality. Histological sectioning of the teeth was used to verify the presence and extent of decay. Results: No significant difference was found between the diagnostic accuracies of the three imaging modalities (P ¼ 0.226). Analysis of the diagnostic accuracy of the three modalities on lesion depth showed no statistically significant interaction; however, the main effect of the lesion depth was significant (P , 0.001, h 2 ¼ 0.936). Conclusions: The overall diagnostic accuracy of the three modalities in the detection of approximal carious lesions was comparable. All three modalities performed poorly in the detection of enamel lesions.
Intravenous bisphosphonate (BP) therapy has become the standard of care for the treatment of cancers that metastasize to bone. BPs are associated with osteonecrosis of alveolar bones, a condition known as osteonecrosis of the jaw (ONJ). The incidence or pathogenesis of ONJ is largely unknown. The lesions are characterized by areas of exposed necrotic bone that do not heal after 8 weeks in the absence of radiation to the head and neck. ONJ lesions have been recalcitrant to conventional therapies. Lesions in cancer patients treated with BPs develop in association with periodontal disease, tooth extraction and/or in association with increased mechanical force due to partial/complete dentures. We hypothesized that intravenous BPs in cancer patients impair normal bone remodeling, thereby increasing the incidence of osteonecrotic lesions and that these lesions can be detected using cone beam computerized tomography (CBCT). From CBCTs taken at the University of Missouri at Kansas City School of Dentistry, 26 subjects had a cancer diagnosis and were on BP therapy. From these 26 subjects, 18 presented visible, exposed necrotic bone. We observed both sclerotic and radiolucent lesions. Lesions could be detected and measured in reconstructed images where most were found to expand to large areas of the bone. We were able to identify necrotic bodies or ‘involucrums’ within the ONJ lesions, suggesting that this could be the mechanism for the formation of a clinically visible sequestrum. We propose that CBCT can potentially identify and follow the progression of both pre- and postclinical lesions in ONJ patients, allowing better diagnosis and assessment of disease status.
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