A comparison of the masticatory function between two different types of implant supported prostheses and complete denture for fully edentulous patients

Abstract

For over 3 decades and since the preliminary studies on osseointegration, dental implants have been used extensively for the rehabilitation of completely and partially edentulous patients. Dental treatment with implants appears to provide many benefits for the edentulous patient as well as a significant oral function improvement and increased patient satisfaction. Fewer complaints, increased satisfaction, and higher ratings with regard to masticatory comfort and ability compared to conventional denture wearer have been all reported. Improvement attributed to the dental implant in an objective function appears to depend on the type of implant support for the denture. The implant supported denture can be divided by type of prosthesis (fixed or removable) or material for the teeth (porcelain or resin). The early form of implant prosthesis for edentulous patients was fixed dental prostheses referred by Zarb, which consisted of attached denture teeth with heatpolymerized acrylic resin to a cast metal substructure. More recently, metal ceramic fixed partial dentures are more frequently used. The latter type of prosthesis needs 8 implants because it is restored as a separated unit compared to the former splinted type with 5 to 6 implants. It is reported that the number and positioning of implants have an influence on force transfer and subsequent stress distribution around implants. The increase in number improves the biomechanical implants behavior, especially when subjected to bending forces. Distribution and magnitude of occlusal forces on implants carrying fixed prostheses was investigated while supported by 5 6 and 3 4 implants. Higher forces were observed with a decreasing number of implants. It is also reported that the type of prosthesis can affect implant loading mode. Loading of the extension parts of the prostheses, commonly used in the former type of prosthesis, caused a hinging effect. This in turn, induced considerable compressive forces on the implants closest to the location of load application and lower compressive or tensile forces on other implants. Regardless of its design, an implant-prosthesis complex transmits occlusal forces to the peri-implant bone. Therefore, the force absorption quotient of the prosthesis material has been a topic of research interest. Skalak envisaged that the use of acrylic resin teeth would be useful for shock protection on implants and recommended the use of acrylic resin as the material of choice for the occlusal surfaces of implant prostheses. The resiliency of resin was suggested as a safeguard against the negative effects of impact forces of the bone-implant interface. The literature, however, is inconclusive on its effect on shock absorption. In fact acrylic resins are burdened with technical and subjective disadvantages. For example, due to their low wear resistances, premature contacts often occur after several months of prosthesis delivery. Conversely, gold and porcelain surfaces are not considered to provide adequate