The Regeneration of the Periodontal Ruffini Endings

Abstract

This review highlights the morphology, neuroplasticity and regeneration of the periodontal Ruffini endings, essential mechanoreceptors in the periodontal ligament. The periodontal Ruffini endings are characterized by expanded axon terminals filled with a number of mitochondria and by the presence of terminal or lamellar Schwann cells. Many experimental studies have revealed that periodontal Ruffini endings have high potential for neuroplasticity, confirmed by intense immunoreactivity for several markers such as low affinity neurtropin receptor (p75-NGFR) and growth associated protein-43 (GAP-43) even in mature periodontal ligament. The periodontal Ruffini endings could regenerate by 14 days after injury of inferior alveolar nerve, faster than the Ruffini endings in other tissues. Previous immunocytochemical studies have shown expression of immunoreactivity for trkB, a high affinity neurotrophic factor receptor, in the periodontal Ruffini endings, suggesting brain derived neurotrophic factor (BDNF) is a candidate for neurotrophins involved in the regeneration of the periodontal Ruffini endings. Our recent immunocytochemical and quantitative analyses on BDNF-deficient mice have revealed the involvement of BDNF in the regeneration of the periodontal Ruffini endings. Further investigations are needed for clarifying the involvement of other neurotrophins and their molecular mechanism of the regeneration processes of the periodontal Ruffini endings.