Alveolar Bone Resorption and Atrophy

Alveolar bone is the part of the maxilla and mandible that surrounds and supports the roots of the teeth. It is among the most metabolically active bone in the body, remodelling continuously in response to the forces transmitted through the periodontal ligament. When that bone is destroyed by inflammation or lost through disuse after the teeth are removed, the result is alveolar bone resorption and atrophy — a reduction in the height and width of the tooth-bearing ridge that undermines tooth support and complicates later restoration.

Definition

Alveolar bone resorption and atrophy is the loss of bone height and volume in the tooth-supporting (alveolar) process of the jaws, occurring either through inflammation-driven destruction of bone around the teeth or through atrophy of the residual ridge after teeth are lost.

Scope

This entry covers the two principal pathways by which alveolar bone is lost — inflammatory resorption in periodontal disease and atrophic resorption of the residual ridge after tooth loss — together with the remodelling biology that underlies both. It is a reference description of the process and its mechanisms, not a guide to clinical diagnosis or treatment.

Core questions

• What distinguishes inflammatory alveolar bone destruction from atrophic resorption of the edentulous ridge?
• How does the immune response to the dental plaque biofilm shift bone remodelling toward net resorption?
• Why does the alveolar ridge continue to resorb after the teeth that it supported are gone?

Key concepts

• Alveolar process and periodontal ligament
• Bone remodelling (resorption–formation coupling)
• Osteoclast activation and RANKL signalling
• Inflammatory (periodontitis-associated) bone loss
• Residual ridge resorption after tooth loss
• Disuse atrophy of the alveolar ridge

Mechanisms

Alveolar bone is destroyed when the local balance of remodelling tips toward resorption. In periodontitis, a dysbiotic subgingival biofilm provokes a host inflammatory response in which cytokines and the RANKL pathway drive osteoclast differentiation and activation, producing net loss of the bone around the teeth (Hajishengallis, 2014; Hajishengallis, 2014, Nature Reviews Immunology). This bone loss is therefore mediated by the host immune reaction to bacteria rather than by direct bacterial destruction alone. A second, non-inflammatory pathway operates after teeth are extracted: deprived of the functional loading transmitted through the periodontal ligament, the residual alveolar ridge undergoes progressive atrophic resorption that reduces its height and width over time (Atwood, 1971). The architecture of the periodontal attachment apparatus defines what is protected and what is lost when these processes act (Schroeder & Listgarten, 1997).

Clinical relevance

Loss of alveolar bone is the structural endpoint of periodontal disease and a determinant of how an edentulous ridge will support a prosthesis or implant, so the concept underlies much of restorative and periodontal thinking. This entry explains the process as a body of knowledge; it characterizes how bone is lost and does not prescribe assessment or treatment for any individual.

Epidemiology

Inflammatory alveolar bone loss accompanies periodontitis, one of the most prevalent chronic conditions of the dentition worldwide, with severe forms affecting a substantial minority of adults. Atrophic residual-ridge resorption is a near-universal consequence of tooth loss, progressing at variable rates and contributing to the prosthetic challenges of edentulism.

Seminal works

• hajishengallis-2014
• atwood-1971

Frequently asked questions

Is alveolar bone loss caused directly by bacteria?

Inflammatory alveolar bone loss in periodontitis is driven largely by the host immune response to the dental plaque biofilm — cytokine and RANKL-mediated osteoclast activation — rather than by direct bacterial destruction of bone alone.

Why does the ridge keep shrinking after teeth are removed?

Once teeth are lost, the alveolar bone no longer receives the functional loading transmitted through the periodontal ligament, and the residual ridge undergoes progressive disuse atrophy that reduces its height and width.