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Non-Metal Clasp Dentures

Course Number: 650


The treatment options currently available to partially edentulous patients include fixed dental prostheses, removable dental prostheses, and implant-supported prostheses.1 Since the last three decades, dental implants have played a significant role in the rehabilitation of the majority of patients, however, not all patients are candidates for implant therapy.2 Removable dental prostheses (RDPs) are still a viable, conservative, and cost-effective alternative for rehabilitation of partially edentulous patients.2-4 RDP’s require minimum tooth preparation and clinical time compared to fixed and implant-supported restorations.2,3,5 The flanges of the RDP aid in providing optimal support to the lip and facial tissues, thereby precluding the need for further surgical interventions.6,7 RDP’s may also be indicated in medically compromised patients who are unable to sit or keep their mouth open for an extended time and those with a restricted mouth opening.

Traditionally, polymethyl methacrylate acrylic (PMMA) resins were used to fabricate the RDP bases and cast metal frames were incorporated as needed to restore the edentulous areas.8 However, the inherent problems associated with the PMMA material such as difficulty in insertion in undercut areas (due to lack of flexibility), brittleness, poor esthetics (due to display of the metal clasps), and allergic reactions to methyl methacrylate monomer affected the success of the RDP’s.9

Thermoplastic denture base materials were introduced in the 1950s to circumvent the problems associated with PMMA resins.8 These materials offer improved esthetics, have superior elasticity, fracture resistance, and flexibility (providing ease of insertion and removal) compared to PMMA resins.8 As opposed to the metal clasps used with an acrylic prosthesis, esthetic and elastic thermoplastic resin clasps, are used to retain the prosthesis, leading to increased patient acceptance.5,8,10 The flexibility (of thermoplastic materials), not only aids in providing enhanced retention and ease of insertion and removal of the RDP but also in decreasing the stress on the abutment teeth.5

The RDP’s fabricated using thermoplastic resin are called metal-free dentures, flexible dentures, non-clasp dentures, clasp-free dentures, and/or non-metal dentures, however, the more appropriate term to designate them is “nonmetal clasp dentures” (NMCDs).11 There is a lack of long-term clinical studies, as well as systematic reviews addressing NMCDs. This course will review the indications, contraindications, limitations, advantages, disadvantages, and designing principles of NMCDs to guide the readers regarding the clinical applications of these prostheses. It will also detail the procedural steps for the fabrication of these prostheses.