were tried, including ivory , glass balls, ground rubber , ox cartilage , Terylene wool , gutta-percha , Dicora, polyethylene chips, polyvinyl alcohol -formaldehyde polymer sponge (Ivalon), Ivalon in a polyethylene sac, polyether foam sponge (Etheron), polyethylene tape (Polystan) or strips wound into a ball, polyester (polyurethane foam sponge) Silastic rubber,