Histology of Cementum

Histology of Cementum

• Cementum is a tissue covering the tooth root
• It's part of the periodontium, crucial for tooth attachment
• Students should be able to describe the composition and structure of cementum, differentiate between its two main types (acellular and cellular) and their distribution, and relate structure to function.
• Understand the clinical relevance of cementum in health and disease.

Analogy for Location

• An ice cream cone analogy demonstrates how cementum occupies the space around the tooth root

Cementum in Relation to the Periodontium

• Cementum connects the tooth root to the alveolar bone
• It's a key component of the periodontium, which anchors the tooth in the jaw
• Features like dentine, pulp canals, and alveolar bone are all part of the same complex system

Why Study Cementum?

• Understanding cementum is crucial for dental health and disease prevention (in health)
• Knowing about root caries and periodontal disease requires understanding cementum's role
• Good oral hygiene practices will be improved from understanding dental diseases
• Treatment and prevention are related to cementum function.

Acellular and Cellular Cementum Composition and Structure

• Cementum is mainly composed of inorganic (mostly hydroxyapatite) and organic materials
• Collagen fibers (primarily type 1) are important organic components
• Non-collagenous proteins and water are also present

Overview of Structural Features

• Acellular cementum lacks cells, while cellular cementum contains cementocytes
• Acellular cementum is primarily found on the cervical region of the tooth root, and Cellular cementum predominantly forms in the apical third.
• Fibres within acellular cementum are primarily extrinsic, while those within cellular cementum can be both intrinsic and extrinsic

Acellular Cementum

• Primarily covers the cervical and middle third of the root
• The first-formed layer of cementum
• Adjacent to the dentin, forming the dento-cementum junction (CDJ)
• It forms slowly during and after teeth emergence,
• Contains extrinsic collagen fibers
• No cells present.

Acellular Cementum Distribution

• Acellular afibrillar cementum (AAC) covers the enamel and dentin portion of the cervical region
• Acellular extrinsic fibers cementum (AEFC), the predominant acellular type, is crucial for supporting and anchoring the tooth.

Acellular Cementum Functions

• Supports and anchors the tooth in the alveolar socket
• Extrinsic fibers (Sharpey's fibers) connect to the periodontal ligament and alveolar bone
• Fibers are oriented perpendicular to the root surface

Cellular Cementum

• Also known as secondary cementum
• Forms quickly compared to primary cementum
• Contains cementocytes that are trapped within a cementoid layer, a mineralized matrix.
• Contains intrinsic fibers that are parallel to the root surface
• Over time, extrinsic fibers are also found

Cellular Cementum Cells

• Cementoblasts - form cementum
• Cementocytes - found in cellular cementum and originate from cementoblasts
  • Cementocytes are trapped within the matrix during cementum development

Cellular Cementum Distribution

• Cellular intrinsic fiber cementum (CIFC) is found in the apical third of the roots
• It is often absent in those with single-rooted teeth.
• Cellular mixed stratified cementum (CMSC) is a variant of CIFC containing both intrinsic and extrinsic fibers.
• CMSC makes up most of the bulk of cellular cementum over time.

Cellular Cementum Functions

• Adaptation - reshapes the root, adjusting for tooth movement and drift ,or following tooth extractions.
• Deposition of cementum at the apex maintains occlusion, compensating for occlusal wear. It is thicker in teeth at the back of the mouth (posterior teeth).

Cellular Cementum Functions 2

• Anatomical repair: The ability to repair resorbed or fractured root surfaces.
• Functional repair: Maintaining the periodontal ligament width during periodontal disease (PDL) healing.

Distribution of Cementum

• Acellular cementum tends to be thicker in the cervical region of the root.
• Cellular cementum tends to be thicker in the apical part of the root.
• Molar teeth have a thicker, and more extensive, cellular cementum compared to incisor teeth. This is due to the greater occlusal forces on the molar teeth.

Clinical Significance Functions

• Cementum is closely linked to many clinical aspects of dental health and disease
• Understanding its properties relates to its involvement in periodontal disease

Cementum over the Lifecourse

• Cementogenesis (the formation of cementum) continues throughout life.
• As we age, the thickness, hardness, and mineral content of cementum increase.

Cemento-Enamel Junction (CEJ)

• The relationship between cementum and enamel at the CEJ varies between and within teeth.
• Overlap, gap, and meet conditions can describe the different relationships

Structural Abnormalities

• Hypercementosis: Excessive cementum deposition, creating thicker roots.
• Causes can be from trauma,inflammation, systemic conditions such as Paget's disease. or idiopathic (of unknown cause).
• This can complicate tooth extractions.

Summary

• Cementum has a variety of roles, from anchoring teeth to adapting over time.
• It is crucial for determining how healthy teeth function and are maintained over a lifetime.