Alignment of Biological Apatite Crystallites in Posterior Cortical Bone of Human Edentulous Mandible

Abstract

The mandible is a unique bone with a two-layered structure comprising the alveolar area that holds the teeth and the base of the mandible. When teeth are lost, the alveolar area is quickly resorbed, and the internal structure of the mandible changes greatly. Quantitative assessment of changes in the bone microarchitecture that occur with tooth loss is thus imperative. We therefore quantitatively assessed bone mineral density (BMD) and biological apatite (BAp) crystalline orientation in human edentulous mandibles and elucidated the structural characteristics of human edentulous mandibles. Japanese edentulous mandibles were divided into samples with a high and well-rounded alveolar area and thin cortical bone in the alveolar area (α-type), thick cortical bone (β-type), and those with a low and flat alveolar area (γ-type). BMD and BAp crystalline orientation were measured in the alveolar area and base of the mandible of the site corresponding to the first molar (the region of interest). Although BMD did not differ by site, comparisons of the different types revealed that BMD was high in the α-type and low in the β-and γ-types. BAp crystalline orientation in the alveolar area was observed in the vertical direction to the virtual occlusal plane (Y-axis) and buccalingual direction (Z-axis) in the α-type, whereas weak preferential orientation in the mesiodistal direction (X-axis) was observed in the β-and γ-types. BAp crystals in the base of the mandible showed uniaxial preferential alignment along the X-axis in all three sample types (p < 0.05). These findings demonstrate that most of the human edentulous mandible develops long bone-like characteristics with resorption of the alveolar area and that orientation in the alveolar area varies with morphological changes in the alveolar bone.

Alignment of Biological Apatite Crystallites in Peri-Implant Bone of Beagles

“…In the present experiment, no preferential alignment was seen in any direction at any of the sites in partially edentulous jawbones. The present ndings are in agreement with the study by Iwata et al which reported that preferential alignment in the alveolar regions is lost due to tooth extraction 23) . Another report found that in the cranium, tooth extraction not only affected alveolar region morphology but also orbital and nasal cavity morphology as well as zygomatic bone morphology 26) .…”

“…Morioka et al and Furuya et al also used this method for detailed analysis of BAp crystallite alignment in human jawbone and reported that dentate mandibles exhibit a double structure on a nanoscale 21,22) . Furthermore, Iwata et al examined BAp crystallite alignment in edentulous jawbone and found that the preferential alignment of alveolar bone formed around the teeth was lost 23) . However, few papers have discussed the nanoscale properties of jawbone around loaded implants.…”

A paradigm shift for bone quality in dentistry: A literature review

“…This is well explained using mandibular bone that is subject to complicated mechanical environments. The cortical bone portion apart from the tooth, such as corpus mandibulae, essentially exhibits a unidirectional preferential BAp c-axis orientation along the mesiodistal axis [20,74,76]. Conversely, the portion located beneath the tooth exhibits preferential BAp c-axis orientation along the biting axis (Fig.…”