Cement And Dentin PDF

# Cement and Dentin Cement and dentin are mineralized supporting tissues. Their mineralization levels are different. They do not contain blood vessels and cannot be reconstructed, but their thickness can increase over time. Bone tissue also is a mineralized supporting tissue. It contains blood...

# Cement and Dentin Cement and dentin are mineralized supporting tissues. Their mineralization levels are different. They do not contain blood vessels and cannot be reconstructed, but their thickness can increase over time. Bone tissue also is a mineralized supporting tissue. It contains blood vessels, and it is reconstructed throughout life, and its thickness can increase. Despite similarities between dentin and cement, there is a greater structural similarity between cement and bone. Both are mineralized at the same level, and their cells - cementocytes and osteocytes - are similar. There are no cell bodies in dentin, only odontoblast projections. ## Cement Cement is layered and its layers run parallel to the surface. Sharpey's fibers, which are embedded sections of the root's fibril bundles (5a), are a major component of cement. They run almost perpendicular to the surface and extend deep into cement. The connection between the root and cement is analogous to the periosteum's connection to bone. The term Sharpey's fibers refers to embedded sections of the root's fibril bundles, which are located close to the tooth, embedded in cement and the peripheral sections embedded in alveolar bone. Layered cement building is visible in the growth lines (3b) similar to those in enamel and dentin. These lines indicate the different speeds of formation of cement, like all other hard tissues. ### Cement types - **Acellular Cement** (3c) coats the dentin and is acellular. It's found in several places, including the apical third of the root. - **Cellular Cement** (3d), which is located on top of the acellular cement, is significantly thicker than the acellular cement. - **Cementocytes (4)** resemble osteocytes. They have projections, mainly directed towards the root. - **Cementocytes Renewal** does not occur, which means that the cementocytes do not renew. Consequently, cement cells in the inner layers often show signs of degeneration. - **Cementocytes Similarity** - Cementocytes are similar to osteocytes. They sit in lacunae (6), like osteocytes, and their projections are located in fine canals (6a), similar to osteocyte projections. When osteocytes extend their projections, they do so in a somewhat even manner in all directions, but the majority of cementocytes' projections face the root (5). The reason for this "alignment" of projections is probably that cementocytes are provided nutrients from the root. - There are many vessels in bone tissue and there are distributed evenly. Therefore, the cell projections point in all directions. - **Degeneration** - Cementocytes in the deepest layers show a sign of degeneration with age. This is probably not due to aging alone, but also due to difficult nutrient supply. The cement becomes thicker, and the distance between the root and the deepest cells increases. ## Dentin - **Primary Dentin** forms during tooth development - **Secondary Dentin** is formed naturally by the body during life - **Tertiary Dentin** is formed as a result of mechanical and irritative impacts on the crown of a tooth. Tertiary dentin ('irritation dentin') is formed on the dentin surface in the pulp. ## Pulp - **Pulp Definition** Pulp is a connective tissue that fills the crown's pulp chamber and root canal. - **Pulp Composition** Pulp contains connective tissue cells (3), collagen fibrils, and amorphous basic substance. - **Pulp Cells** The only cells that differ from other connective tissue cells of the human body are odontoblasts (4b), which form a layer on the dentin surface and have projections that extend deep into the dentin canals. Odontoblasts are prismatic during development. Later, only prismatic odontoblasts (4b) are present in the crown pulp, while in the root pulp they are cubical (4b) or flat(4c) - **Odontoblast Similarity** Odontoblasts resemble connective tissue cells. ## Odontoblast Form The odontoblast form (prismatic, cubical, or flat) is related to the cell's activity. 1. When they are actively generating protein that deposits as the dentin matrix, they acquire an elongated and tall form. 2. When their activity decreases, they might flatten. ## Weil's zone Weil's zone (8), which is a cell-poor zone, is located in the odontoblast layer. 1. The zone is about the same width as the odontoblast layer. 2. It includes capillary loops (9), which reach the odontoblasts, as well as the subodontoblastic nerve plexus (10), from which fibers extend between the odontoblasts. ## Pulp Blood Supply Pulp is supplied by a small artery (11), which passes through the apical foramen. The foramen is also crossed by veins (12), lymphatic vessels (13), and nerves (14). The pulp artery (11) continues to the incisal part of the crown pulp and distributes branches along the way. ## Pulp Artery The pulp artery is an arteriole (Fig. 41) and a great example of an anatomical end artery. This means it's the only artery supplying a tissue. If the pulp artery is damaged, the pulp will lose its blood supply and die. The pulp artery sends out branches as mentioned above throughout the pulp, but most branches depart towards the incisal in the crown pulp. All of these branches extend towards the subodontoblastic zone, ending in capillary loops (9). ## Pulp Nerve Supply Nerve fibers in the pulp are grouped into five to ten nerve fiber bundles during their transition through the apical foramen. Most nerve fibers in the pulp are