Clasp retention and composites: an abrasion study

An in vitro test for screening the abrasion resistance and abrasivity of composite resins when used to provide tooth undercuts for removable partial denture clasps is described. In the present study nine composite resins were tested against wrought stainless steel round clasps. The results indicated that the abrasion of any of the composites tested was unlikely to cause a noticeable loss of retention in the clinical situation. However, there was marked abrasion of the clasps by two of the composites which would be likely to be clinically relevant.