PubMed · 11584510
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T Fujino, M Kobayashi, R G Calderhead. 2001. The computer and simulation surgery.. https://doi.org/10.2302/kjm.50.supplement2_39
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Current techniques for three-dimensional (3D) optical microscopy (deconvolution, confocal microscopy, and optical coherence tomography) generate 3D data by "optically sectioning" the specimen. This places severe constraints on the maximum thickness of a specimen that can be imaged. We have developed a microscopy technique that uses optical projection tomography (OPT) to produce high-resolution 3D images of both fluorescent and nonfluorescent biological specimens with a thickness of up to 15 millimeters. OPT microscopy allows the rapid mapping of the tissue distribution of RNA and protein expression in intact embryos or organ systems and can therefore be instrumental in studies of developmental biology or gene function.
The mechanical behavior of dental enamel has been the subject of many investigations. Initial studies assumed that it was a more or less homogeneous material with uniform mechanical properties. Now it is generally recognized that the mechanical response of enamel depends upon location, chemical composition, and prism orientation. This study used nanoindentation to map out the properties of dental enamel over the axial cross-section of a maxillary second molar (M(2)). Local variations in mechanical characteristics were correlated with changes in chemical content and microstructure across the entire depth and span of a sample. Microprobe techniques were used to examine changes in chemical composition and scanning electron microscopy was used to examine the microstructure. The range of hardness (H) and Young's modulus (E) observed over an individual tooth was found to be far greater than previously reported. At the enamel surface H>6GPa and E>115GPa, while at the enamel-dentine junction H<3GPa and E<70GPa. These variations corresponded to the changes in chemistry, microstructure, and prism alignment but showed the strongest correlations with changes in the average chemistry of enamel. For example, the concentrations of the constituents of hydroxyapatite (P(2)O(5) and CaO) were highest at the hard occlusal surface and decreased on moving toward the softer enamel-dentine junction. Na(2)O and MgO showed the opposite trend. The mechanical properties of the enamel were also found to differ from the lingual to the buccal side of the molar. At the occlusal surface the enamel was harder and stiffer on the lingual side than on the buccal side. The interior enamel, however, was softer and more compliant on the lingual than on the buccal side, a variation that also correlated with differences in average chemistry and might be related to differences in function.
OBJECTIVES: The objective of this study was to quantify the variation in use and type of imaging guides used by community-based specialists and general practitioners during dental implant treatment planning phases. The specific aim of this study was to test the hypothesis that specialists are more likely to use some form of cross-sectional imaging in conjunction with imaging guides during the preoperative assessment of dental implant procedures. STUDY DESIGN: Records from 630 patients with implants (1640 implants) referred for cross-sectional tomography were reviewed. Imaging guide type and implant sites were noted. RESULTS: The distribution of referring dentists by specialty was as follows: general practitioners (42.2%), periodontists (35.1%), oral and maxillofacial surgeons (13.3%), and prosthodontists (7%). Of patients referred for tomograms, 52% were referred without a surgical guide. CONCLUSION: Specialists ordered tomograms in conjunction with imaging guides more often than did general practitioners. Prosthodontists and periodontists preferred to use more restrictive guides than did general practitioners or oral and maxillofacial surgeons.