Relationships between bone mass and micro-architecture at the mandible and iliac bone in edentulous subjects: a dual X-ray absorptiometry, computerised tomography and microcomputed tomography study

Relationships between bone mass and micro-architecture at the mandible and iliac bone in edentulous subjects: a dual X-ray absorptiometry, computerised tomography and microcomputed tomography study Objectives:  To compare bone volume, bone mineral density, cortical thickness and bone micro-architecture in a series of paired mandibular and iliac bone samples analysed by various imagery techniques to see whether relationships exist between the various techniques and between mandibular and iliac bone. Materials and methods:  Bone samples from the mandible and ilium were harvested in 20 cadavers and analysed by dual energy X-ray absorptiometry (DXA), computerised tomography (CT) on a conventional hospital machine and microCT. Results:  Significant correlations were found between Hounsfield density obtained by CT, and bone mass determined by microCT but not with DXA values. Cortical thickness measurements were well correlated between CT and microCT. No relationships were found between mandibular and iliac bone, when considering mineral density, cortical thickness, bone volume or micro-architecture. Conclusion:  In clinical practice, CT remains the most appropriate routine means for bone qualitative and quantitative evaluation at the mandible. In this ex vivo study, these results confirm that mandibular bone status does not reflect the axial skeletal one and assist in the placement of implants with dental prostheses in old or osteoporotic patients

Mechanical adaptation of trabecular bone morphology in the mammalian mandible

Alveolar bone, together with the underlying trabecular bone, fulfils an important role in providing structural support against masticatory forces. Diseases such as osteoporosis or periodontitis cause alveolar bone resorption which weakens this structural support and is a major cause of tooth loss. However, the functional relationship between alveolar bone remodelling within the molar region and masticatory forces is not well understood. This study investigated this relationship by comparing mammalian species with different diets and functional loading (Felis catus, Cercocebus atys, Homo sapiens, Sus scrofa, Oryctolagus cuniculus, Ovis aries). We performed histomorphometric analyses of trabecular bone morphology (bone volume fraction, trabecular thickness and trabecular spacing) and quantified the variation of bone and tooth root volumes along the tooth row. A principal component analysis and non-parametric MANOVA showed statistically significant differences in trabecular bone morphology between species with contrasting functional loading, but these differences were not seen in sub-adult specimens. Our results support a strong, but complex link between masticatory function and trabecular bone morphology. Further understanding of a potential functional relationship could aid the diagnosis and treatment of mandibular diseases causing alveolar bone resorption, and guide the design and evaluation of dental implants

Non-invasive evaluation of an injectable bone substitute.

Colloguium on Model Driven Acquisition, GRENOBLE, FRANCE, NOV 23-24, 2000Despite the increasing number of techniques for the preservation of bone ridges after dental avulsion, no precise evaluation of alveolar filling has been performed to date. The criteria of available measurement techniques (probes, retroalveolar or panoramic radiography, and lateral teleradiography) are not sufficiently reliable and precise. This study investigated the reliability of evaluation based on CT images in comparison with retroalveolar radiography (the most precise radiographic technique, providing standardised images), direct measurements, and images obtained in scanning electron microscopy. After a preliminary investigation ex vivo, a study was performed in vivo on three beagles. Mandibular premolars were extracted, and the corresponding alveoli were filled with an injectable bone substitute composed of a calcium phosphate mineral load associated with hydroxypropyl methylcellulose. Measurements performed on CT images relative to visual and automatic detection of density changes and studies of density curves provided better precision than those obtained by retroalveolar radiography. (C) 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS

Statistical Analysis of Histomorphological Findings in Medullary Thyroid Carcinoma: Distinction Between the Different Familial Forms of the Disease

A multifactorial analysis of morphological findings was performed on 153 cases of medullary thyroid carcinoma (MTC). The aim of the study was to utilize histological criteria to discriminate between MTC associated with multiple endocrine neoplasia type 2A (MEN 2A) and that associated with the inherited MTC only syndrome. The presence of fusiform cells associated with several other markers seemed to he more predictive of MEN 2A. A comparison of inherited MTC only and sporadic MTC only showed fusiform cells to be significantly less common in inherited MTC only. These results suggest that the inherited MTC only syndrome is a distinct clinical and morphological entity. Further investigations are needed to confirm the finding and understand its implications