A<unk>  is a small, spherical or ovoid calcified mass embedded within or attached to the cementum layer on the root surface of a tooth, or lying free within the periodontal ligament. They tend to occur in elderly individuals. There are 3 types: * Free<unk>  – not attached to cementum * Attached (sessile)<unk>  – attached to the cementum surface (also termed exocementosis) * Embedded (interstitial)<unk>  – with advancing age the cementum thickens, and the<unk>  may become incorporated into the cementum layer They may be visible on a radiograph (x-ray). They may appear singly or in groups, and are most commonly found at the tip of the root. Their size is variable, but generally they are small (about 0.2 mm – 0.3 mm in diameter).<unk> s are usually acellular, and may contain either fibrillar or afibrillar cementum, or a mixture of both.<unk> s are the result of dystrophic calcification, but the reason why this takes place is unclear.<unk> s are thought to form when calcification occurs around a nidus, a precipitating center. Around this nidus they slowly enlarge by further deposition of calcium salts. Examples of how<unk> s are thought to form include: * Calcification due to degenerative changes in the epithelial cell rests of Malassez * Calcification of thrombosed (blocked) capillaries in the periodontal ligament (i.e. a phlebolith) * Microtrauma to Sharpey's fibres causes small spicules of cementum or alveolar bone to splinter into the periodontal membrane Some do not consider these as true<unk> s.
Cementicle
Floor plate
Neuromere
Nuclear bag fiber
Trabectome
Lines of Zahn
Dendrosome
Sebaceous filament