Cementoïde

Cementoïde, also spelled cementoide in some languages and sometimes referred to as cementoid, is a histological term used to describe the unmineralized organic matrix secreted by cementoblasts during the formation of cementum on the tooth root. It is analogous to osteoid in bone and represents the initial product of cementogenesis before mineral deposition.

During root development, cementoblasts line the forming surface of cementum and lay down a collagen-rich matrix that remains unmineralized for a period. This cementoid stage provides the scaffold for subsequent mineralization, with hydroxyapatite crystals gradually deposited to form mature cementum. The process occurs as the root surfaces mature and can be observed in developing teeth; cementoid may persist transiently in regions of active apposition.

Compositionally, cementoid is primarily composed of type I collagen and other non-collagenous proteins, along with proteoglycans that contribute to the matrix environment. Once mineralization proceeds, the matrix becomes cementum, which serves to anchor the periodontal ligament via Sharpey's fibers.

Usage and terminology vary by language and historical context. In English-language dental histology, the term cementoid (or cementoid tissue) is commonly used to describe this transient, unmineralized stage; some languages also employ the form "cementoïde." The concept helps distinguish the formative, organic phase of cementum from its mineralized, mature form.

See also: cementum, cementogenesis, osteoid.