Bone undergoes constant remodeling throughout life. The cellular and biochemical mechanisms of bone remodeling vary in a region-specific manner. There are a number of notable differences between the mandible and long bones, including developmental origin, osteogenic potential of mesenchymal stem cells, and the rate of bone turnover. Collagen, the most abundant matrix protein in bone, is responsible for determining the relative strength of particular bones. Posttranslational modifications of collagen, such as intermolecular crosslinking and lysine hydroxylation, are the most essential determinants of bone strength, although the amount of collagen is also important. In comparison to long bones, the mandible has greater collagen content, a lower amount of mature crosslinks, and a lower extent of lysine hydroxylation. The great abundance of immature crosslinks in mandibular collagen suggests that there is a lower rate of cross-link maturation. This means that mandibular collagen is relatively immature and thus more readily undergoes degradation and turnover. The greater rate of remodeling in mandibular collagen likely renders more flexibility to the bone and leaves it more suited to constant exercise. As reviewed here, it is important in clinical dentistry to understand the distinctive features of the bones of the jaw.

Uncertainty exists regarding sex-, age-and tooth-related cortical and trabecular bone quantity tendencies at the mandibular first molar, a frequent implant recipient site in partially edentulous patients with missing molars. We assessed these tendencies for the mandibular first molar by using computed tomography in patients missing the first molar on one side. Eighty-two subjects were assessed. Cortical and trabecular bones were quantified using computed tomography image reformatting software on a cross-sectional image, including the site of the mandibular first molars on sides with and without the first molar. Bone quantity associations with age and between the sides with and without the first molar were evaluated. Bone quantities were compared according to sex and between the two sides. Great interindividual variations between cortical and trabecular bone quantities were seen in both sexes and on the two sides. Although no sex-related or age-related difference in trabecular bone quantity existed, men demonstrated a greater cortical bone quantity than women; women, but not men, exhibited an age-related decline in cortical bone quantity. Bilateral symmetry of both bone quantities appeared only in women. Cortical bone quantity did not differ between the two sides in either sex, while trabecular bone quantity differed; the side without the first molar had greater values than that with it in women and, to a lesser extent, in men. A computed tomography analysis distinctively measured cortical and trabecular bone quantities and unveiled their sex-related differences in a clinical situation, as specifically designed in this study.

Mandibular bone matrix shows great inter-individual variation and is independent of age and sex, but did not show as strong a relationship with tooth loss as age. Even so, mandibular collagen may represent a unique characteristic of bone matrix and deserves to be further investigated.