cementoid

Cementoid is a term used in dental histology to describe an immature, mineralizing matrix secreted by cementoblasts during tooth root formation. It is functionally part of the cementum formation process, but in histologic terms it denotes a matrix that has not yet matured into fully organized cementum. Cementoid can be observed as a glassy, eosinophilic layer adjacent to the developing root surface, and may contain scattered lacunae with cementoblast-like cells. Unlike mature cementum, cementoid often lacks the well-defined lamellar structure and extensive insertion of Sharpey's fibers that characterize mature cementum.

Formation and maturation: Cementoblasts secrete an organic matrix rich in collagen and non-collagenous proteins; mineral deposition then converts this matrix into calcified tissue. With ongoing maturation, cementoid thickens and mineralizes into cementum; under some conditions the process may remain arrested, leaving a persistent immature zone.

Clinical relevance: Cementoid is primarily of descriptive value in routine histology and developmental biology. It is not a distinct disease, though abnormal cementoid formation can be encountered in developmental anomalies or in response to injury where repair processes recapitulate cementum formation.

See also: Cementum, Cementoblast, Periodontal ligament, Tooth development.