Responses of jawbone to pressure

Objective: To provide a literature review of bone resorption of edentulous jaws focusing on responses to pressure. Background: After the extraction of all teeth in a jaw there is a continuous reduction of the residual ridge. The individual variation of bone resorption is great, and the aetiology is complex and not yet well understood. Materials and methods: A search of the literature published up to May 2003 on bone resorption and pressure was performed using PubMed/Medline. Results: Animal studies have demonstrated that excessive and constant pressure induces bone resorption. Recent experimental research has indicated that bone resorption is a pressure‐regulated phenomenon with a lower threshold for continuous than for intermittent pressure. Clinical studies have suggested that residual ridge resorption is due more to the effects of denture wearing than to disuse atrophy. However, the results of leaving out dentures at night are not conclusive. Nor does the literature offer any strong evidence for the so‐called combination syndrome, which has been described as a result of unfavourable loading. Clinical studies using multivariate analyses indicate that female gender and systemic factors may be of greater importance than oral and denture factors. Implant‐supported prostheses have a bone preserving effect rather than the continuing resorption under complete dentures. Conclusions: The best way to reduce bone resorption is to avoid total extraction, preserve a few teeth and fabricate overdentures. In edentulous jaws, placement of implant‐supported prostheses will lead to less bone loss and may even promote bone growth. To increase our knowledge of residual ridge resorption extended experimental, clinical and statistical methods will be needed, preferably including collaboration between dental and medical researchers.