Prosthesis Made of an Onlay -Type Rest with High Retentive Force (Cap Clasp)

Abstract

The “Cap clasp” is a retainer which exerts its retentive force through an onlay-type rest covering the occlusal surface and a part of the crown. This case report pertains to evaluation of the usefulness of a cap clasp used as a retainer in cases of temporomandibular arthrosis or bite raising. Abstract Patients: Case 1, a 28-year-old male with malocclusion (molar open bite) associated with temporomandibular arthrosis. After splint therapy, a metallic splint made of cap clasps for the lower molars of both sides was prepared for this patient. Case 2 was a 58-year-old male in whom adequate denture space was not available when preparing a partial denture, because of a deep overbite. This case was treated by bite raising, with cap clasps serving as the retainer. Case 3 was a 48-year-old woman in whom the dental arch size differed between the maxilla and mandible and with malocclusion of the left molars. In this case, treatment with an ordinary clasp denture was difficult. After insertion of an immediate denture using a Starbuck splint, a metal base denture combined with cap clasps was applied. Discussion: The greatest advantage of a cap clasp lies in that it does not necessitate preparation of the tooth and allows the existing crown and bridge to be utilized as an abutment tooth. Retainers made using cap clasps are expected to be useful when bite raising is attempted, because of their high supporting ability and retentive force. They also offer promise as a means of reversible and permanent treatment of temporomandibular arthrosis. Conclusion: Dentures and metallic splints prepared with a cap clasp serving as a retainer fit well into the oral cavity of patients, provide excellent occlusal sup-port, and are retained for long periods of time.