Hard tissue repair in idiopathic external resorption of teeth

A histopathological study has been made of 18 erupted and eight unerupted teeth which showed signs of idiopathic external resorption. The findings support the generally accepted theory that osteoclasts are actively involved in the resorptive process, there was no evidence that mononuclear cells were active in this process. The concept that metaplastic hard tissue was deposited on resorbed dentine surfaces, possibly as a means to shield the pulp from the external environment could not be supported from the evidence from this study. When measured, the length of resorption on which metaplastic hard tissues had been deposited, expressed as a percentage of the resorbed area ranged from zero to 69.3 per cent in the 18 erupted teeth. The percentage of metaplastic tissue replacing resorbed tissue in the eight unerupted teeth examined ranged from zero to 55.6 per cent. This study has provided some information on the type of cell responsible for idiopathic external resorption and these findings have been discussed in the light of the results of research of others in this field. The role of metaplastic hard tissue and its function have been evaluated.