Relationship between Biological Apatite Alignment and Hemi-occlusion in Rabbit Mandibular Cortical bone

Morioka

et al. 2015

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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.

Section: Introductionmentioning

confidence: 99%

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

Iwata

Morioka

et al. 2015

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“…It has been reported that BAp crystal alignment exhibits resistance to compressive stress and the c-axis of BAp crystals is basically aligned with the orientation of collagen fiber bundles 19) , a finding with which our results were generally in accord. BAp crystal alignment in the mandible basically exhibits single-axis dominance in the mesial-distal direction (direction of the long axis), but directly beneath the tooth crowns the level of alignment with the mesial-distal direction decreases, and the crystals become predominantly aligned in the masticatory direction 24,40) . It has been suggested that cortical bone tissue reflects the in vivo compressive stress distribution in the location of the bone concerned, and that this may change the preferential alignment direction.…”

Section: Discussionmentioning

confidence: 99%

Micro/nanostructural Characteristic Changes in the Mandibles of Rats after Injection of Botulinum Neurotoxin

Kusaba

Kitamura

et al. 2021

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Our objective was to perform a quantitative evaluation of changes in the micro/nanostructural characteristics of entheses in rats with reduced masticatory muscle functional pressure, with the aim of elucidating the mechanism whereby masticatory muscle functional pressure contributes to growth and development of the mandible from a biomechanical perspective. Male Wister rats aged 4, 11, 18 and 25 weeks were divided into a Botox group injected with a botulinum toxin serotype A formulation to reduce muscle function (BTX) and a control group (CTRL). They were euthanized 6 weeks later and bone quality at the masseter insertion at the mandibular was analyzed. In the BTX group, the number of fibrous chondrocytes at entheses was significantly lower than in the CTRL group at all ages. The diameter of collagen fiber bundles in rats in the BTX group injected with BoNT/A during their growth phase was significantly smaller than that of rats in the CTRL group. In the mandibles of rats in the CTRL group the preferential alignment was consistent with the orientations of the muscle and tendon, but in growing rats treated with BTX, it was less closely aligned with the orientations of the muscle and tendon.

“…Ogai et al reported that eliminating occlusal force diminishes the BAp alignment in the occlusal direction and increases BAp alignment in the mesiodistal direction of the alveolar part 20,21) . In the present study, differences in the loading applied via premolars and molars were believed to be responsible for differences in BAp orientation in the mesiodistal direction.…”

Section: Bap Orientationmentioning

confidence: 99%

Alignment of Biological Apatite Crystallites in Premolar and Molar Region in Cortical Bone of Human Dentate Mandible

Mitsui

Yamashita

et al. 2016

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The mandible exists in a unique mechanical environment subjected to occlusal force and other functional pressures. In dentulous humans, differences in occlusal force and position are believed to be closely linked to the mandible's structural characteristics. The mechanical environment that this bone occupies is difficult to evaluate qualitatively, and it is therefore assessed indirectly by quantitative determination of bone mineral density (BMD). However, in order to understand the loading environment of the human mandible, we must also evaluate local bone quality. In the present study, we therefore sought to identify the structural properties of each tooth in the dentulous human mandible by qualitatively evaluating the crystalline orientation of biological apatite (BAp) as a marker of bone quality. After dividing the area from the alveolar ridge to the apical foramen surrounding the first and second premolar and molar regions of the Japanese dentulous mandible, we measured BAp crystalline orientation and BMD at a total of 4 sites including 2 on the buccal side and 2 on the lingual side. As a result, the orientation of BAp crystallites showed a significant difference between premolar and molar regions, namely preferred orientation in a direction vertical to the occlusal plane (Y-axis) was high for the premolar region and low for the molar region (p < 0.01). These findings indicated that quantitative evaluation of BAp crystallite orientations in the mandibular cortical bone has been revealed to be an effective parameter regarding the local loads that are applied to the human mandible. It was suggested that the distribution map of BAp crystallite orientations in the mandibular cortical bone based on this study would be valuable for planning the prosthodontic treatment in molar and/or premolar regions.