Histology of Cementum Quiz (ODS Learning Outcomes)

Cementum Composition and Structure

• Cementum is a specialized connective tissue covering the root surfaces of teeth.
• It's composed of 45-50% hydroxyapatite crystals, crucial for its mineral hardness.
• The remaining 50-55% is organic material, primarily collagen Type I fibers, along with minor amounts of other types (III, V, VI, XII, XIV).
• Non-collagenous matrix proteins and water are also present.
• The critical pH for hydroxyapatite is 6.7.

Types of Cementum and Distribution

• Acellular Cementum: This type is further divided:
  • Acellular afibrillar cementum (AAC): Found exclusively in the cervical region, lacks collagen fibers and unknown function.
  • Acellular extrinsic fiber cementum (AEFC): The dominant form of acellular cementum, responsible for supporting and anchoring the tooth. Collagen fibers extend into the periodontal ligament, attaching to Sharpey's fibers.
• Cellular Cementum (Secondary Cementum): Derived from cementoblasts that become trapped in the matrix.
  • Cellular intrinsic fiber cementum (CIFC): Predominantly in the apical third of roots and inter-radicular regions. Lacks extrinsic fibers and has intrinsic fibers parallel to the root.
  • Cellular mixed stratified cementum (CMSC): A subset of CIFC containing both intrinsic and extrinsic fibers, becoming the primary form of cellular cementum.
• Cellular cementum forms quickly compared to its acellular counterpart.

Cementum Structure and Function

• Acellular Cementum Function:
  • Provides support and anchorage by connecting to the periodontal ligament via collagen fibers.
• Cellular Cementum Function:
  • Adaption: Allows root reshaping in response to tooth movement (drifting, occlusal wear). Increased cellular cementum deposition is noticed in posterior teeth where post-eruptive movements are more common. Resorption followed by cementum formation helps repair previously damaged root surfaces.
  • Repair:
    • Anatomical repair: Repairs resorbed or fractured root surfaces.
    • Functional repair: Maintains the health of the periodontal ligament (PDL) during periodontal disease.

Clinical Significance of Cementum in Health and Disease

• Hypercementosis: Excessive cementum deposition, notably towards the apex.
• Etiology:
  • Local factors: Trauma or inflammation
  • Systemic factors: Paget's disease
  • Idiopathic: Unknown cause
• Clinical implications:
  • Affects single or multiple teeth.
  • Often asymptomatic.
  • Can create problems during extractions.