![]() ![]() If an uncut tooth flares outwardly all around, its entire axial aspect can be prepared into a one-plane reduction abutment. The abutment frustum would be compared to and fit inside, an imaginary, ideal, zero TOC cylinder abutment. Geometrically, this shape is a frustum or a “three-dimensional trapezoid,” with the top part truncated and planed instead of pointy. Hence, the axial aspect of a real-life abutment is typically prepared into a conical shape that converges in a gingival to occlusal direction. ![]() The gingival aspect of such teeth could perhaps be shaped into a cylinder, while the occlusal aspect perhaps cannot. Some teeth have a naturally converging emergence profile or feature a supra-coronal concavity or require two-plane reduction. However, it is generally impossible, even when using microscopes, for a dentist to shape the axial aspect of the PFDP abutment into a cylinder. If an abutment can be shaped into a cylinder, it is generally shaped into an oblique, generalized cylinder, since a tooth is usually inclined at a non-right angle and its perimeter at the cementoenamel junction is usually not circular. There are several types of cylinders: with a “right, circular” cylinder, the axis of the cylinder is at a right angle to a circular cylinder base with an “oblique, circular” cylinder, the base of the cylinder is a circle, but the cylinder axis is not at a right angle to the base with an “oblique, generalized” cylinder, the base is a circumscribed shape, but not a circle and the cylinder axis is not at a right angle to the base. Image credit: "Serial sections of the 44 dpn mouse mandibular first molar were stained with (a–d) H&E, (e–h) TB and (i–l) AB-NFR" by Brian L Foster is licensed under CC BY-NC-ND 4.TOC may alternatively be defined as the extent to which the axial aspect of the abutment differs in angle from an imaginary, ideal cylinder shape, where the axial aspect of the abutment is prepared as a cylinder and the base perimeter of this cylinder is the perimeter of the most apical aspect of the axial aspect of the abutment. Legend: AEFC: acellular extrinsic fiber cementum, CIFC = cellular intrinsic fiber cementum, H&E, TB and AB-NFR: different tissue stains. Protein: Collagen and glycoprotein mixtureįigure 4.14: Summary of the histology of mouse tooth and periodontal tissues using various staining techniques. Protein: Amelogenins and Enamelins (not collagen) * = denotes significant variation in percentages found in the literature depending on whether cementum is measured by weight or volume, or whether the CDJ is included or not. Bone tissue is highly vascular-compact bone contains central canals and perforating canals, whereas in spongy bone the space between bony trabeculae is filled with red bone marrow or highly vascular adipose connective tissue. ![]() ![]() Bone tissue is almost entirely ECM, summarized in Table 4.1. Bone tissue can either be compact and made of osteons, or spongy bone made of trabeculae. These cells become trapped inside lacunae between layers of bone tissue, and differentiate ← into osteocytes. Jump to the digestive system/tooth unit.īone tissue ← is deposited in layers by osteoblasts. Childs, Ph.D., FAAA at the University of Arkansas for medical sciences. Tieman, Ed.D., at the University of Kentucky ( we linked to this in the previous chapter as well) The definitions and clinical considerations of these tissues are covered in chapters on the development of these tissues (Chapters 8 through 11)įor more practice using histology images, we share these useful links This chapter briefly covers the histology of the hard tissues enamel, dentin, cementum and bone, as well as the soft tissues of pulp and the PDL. 4 Histology of tooth and periodontal tissuesįigure 4.1: Histology and illustration of compact bone tissue, highlighting cells and layers of ECM. ![]()
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