Abstract: The insert is held in place by surrounding plastic filling material and improves resistance to abrasion. Bonding to the filling material is improved by impregnation of the insert with a wetting agent or filling material. The insert may be made by extruding a porcelain paste into the desired crossection segments. Porosity of the fired material is obtained by mixing a volatile binder, such as polyethelene glycol, with the ceramic powder. Acid treatment is also disclosed for providing the desired porosity.