Periodontium Anatomy Review

Gingiva and Periodontium Overview

• Oral mucosa encompasses all soft tissues within the mouth.
• Divided into three areas:
  • Masticatory mucosa (gingiva, hard palate)
  • Lining mucosa (alveolar mucosa, other membranes)
  • Specialized mucosa (dorsum of tongue)

Surface Characteristics of Gingiva

• Normal healthy gingiva presents as coral pink.
• Papillary contour: pointed, filling interproximal spaces; typically blunt in older individuals.
• Marginal contour appears scalloped in a mesiodistal view, sloping coronally.
• Texture is stippled, giving it an “orange peel” appearance, found only in attached gingiva.
• Firmly consistent, tightly bound to teeth and underlying bone.

Mucogingival Junction

• Acts as the demarcation between attached gingiva and alveolar mucosa.
• Remains stable throughout life; absent on palate due to the firm binding of mucosa to bone.

Alveolar Mucosa and Interdental Papilla

• Alveolar mucosa located apically to attached gingiva, characterized by loose connection and mobility.
• Interdental papilla occupies space between neighboring teeth, critical for early periodontal disease diagnosis. Its shape varies:
  • Anterior: pyramidal
  • Posterior: peaked with gingival col

Gingival Sulcus

• Depth ranges from 2-3 mm.
• Bounded by the tooth surface, junctional epithelium (JE), and sulcus epithelium.

Tooth Eruption

• Continuous tooth eruption occurs throughout life with two types:
  • Active eruption involves upward movement of the tooth towards the occlusal plane.
  • Passive eruption results in the exposure of the crown due to separation of the JE.

Biologic Width

• Defined as the distance from the alveolar bone crest to the margins of the periodontal attachment (total of 3 mm):
  • Gingival sulcus: 1 mm
  • Junctional epithelium: 1 mm
  • Alveolar crest fibers: 1 mm

Gingival Connective Tissue

• Composed of lamina propria containing collagen, reticular fibers, and some elastic fibers.
• Structured in two layers: papillary layer and reticular layer.

Junctional Epithelium

• A cuff-like band of non-keratinized epithelium around the tooth, ranging from 0.025 to 1.35 mm in length.
• Provides a seal at the base of the sulcus, with varying permeability to fluids and inflammatory cells.

Principal Fibers of Gingiva

• Dentogingival: Provide gingival support.
• Alveologingival: Attach gingiva to underlying bone.
• Circular Group: Maintain contour of marginal gingiva.
• Other groups (transseptal, dentoperiosteal, semicircular, transgingival, intergingival) serve specific functions in tooth alignment and support.

Periodontal Ligament (PDL)

• Fibrous connective tissue attaching teeth to alveolar bone.
• Thickness ranges from 0.1 to 0.25 mm, varying with age and eruption stage.
• Contains principal fibers grouped by direction and function, including alveolar crest group, horizontal group, oblique group, and others.

cellular Types in PDL and Cementum

• Undifferentiated mesenchymal cells can develop into various cell types like fibroblasts and osteoblasts.
• Main functions of PDL include mechanical support, formation, nutrition, and sensory perception.

Cementum Classification

• Classified as acellular or cellular, with significant distinctions in formation timing, composition, and presence of cementocytes.
• Acellular cementum is primarily composed of Sharpey’s fibers and forms before teeth reach occlusal plane.
• Cellular cementum forms post-eruption and features incremental lines indicating growth phases, with cementocytes residing within.

Ankylosis and Root Resorption

• Ankylosis involves fusion of cementum and alveolar bone with obliteration of PDL, potentially leading to functional issues.
• Root resorption, primarily physiologic, occurs in deciduous teeth and can happen due to inflammation or trauma.### Cementum Repair
• Epithelium growth into resorption areas hinders cementum repair.

Enamel-Cementum Relationship

• Space between enamel and cementum with dentin exposure is 5-10%.
• End-to-end relationship between enamel and cementum is observed in 30% of cases.
• Cementum overlaps enamel in 60-65% of cases.

Developmental Anomalies

• Anomalies in cementogenesis may include:
  • Enamel projections
  • Enamel pearls
  • Hypercementosis
  • Cementicles

Hypercementosis

• Also referred to as cementum hyperplasia.
• Can occur in teeth that lack antagonists due to excessive eruption.
• Teeth with periapical irritation from pulp disease may develop hypercementosis to compensate for fibrous attachment loss.

Physiologic Mesial Drift

• Continuous migration of teeth in a mesial direction observed.
• Bone resorption on the mesial side of the alveolus coincides with tooth positioning.
• Bone formation occurs on the distal side, indicating activity alteration.
• Compression leads to bone resorption while tension accelerates bone formation.

Supporting (Basal) Bone

• Resorption caused by reduced functional requirements of the alveolar bone.
• Loss of occlusal function results in disuse atrophy of bone structure.

Disuse Atrophy

• Increased functional demand enhances bone density, while excessive demands lead to decreased density.

Defects in the Alveolar Process

• Dehiscence refers to a dipping of the crestal margin, resulting in root exposure.

Cemental Spikes

• A form of hypercementosis characterized by clumping of cementicles and calcification of Sharpey’s fibers.
• Can result from excessive tension due to orthodontic appliances or occlusal forces.