Measurement of submucosal forces transmitted to dental implants.

Early loading of dental implants after placement is believed to be a major cause for premature implant failure. If a transitional denture or partial denture is used during the healing period, occlusal forces may be transmitted to the submerged implant, leading to poorly differentiated growth of bone cells and/or potential inhibition of osseointegration at the bone-implant interface. The objective of this study was to develop an experimental model to measure the force transmission and to characterize the effect of selected loading conditions and relief methods on the forces transmitted to the implant. The loading conditions studied included unilateral and bilateral loading of the prosthesis. Forces were measured at two different relief conditions (relief with and without soft liner) and were compared against a control with no relief. The results show that fabrication of the prosthesis with a proper relief at the implant-denture junction can eliminate the submucosal force transmission to the implant on loading the denture both under unilateral and bilateral loading conditions. When a soft liner is used at the relief site, the transmitted force is small, but a finite value is reproducibly recorded. With no relief, the submucosal force transmission is high and may adversely affect the healing process or osseointegration. The experimental model is valuable in measuring and understanding the submucosal forces that are transmitted to the implant by loading the transitional prosthesis, and such measurement may assist in the proper design of the prosthesis for improved clinical durability and for other uses.

Bond strength of permanent soft denture liners bonded to the denture base.

The purpose of this study was to characterize denture and soft liner adhesion and to determine the adhesive and/or cohesive strength of different soft tissue liners bonded to the denture base by use of a new technique. Two groups of five permanent soft liners (dry or exposed to water for 6 months) were tested by use of a tensile mode to characterize the failure characteristics of soft liners bonded to denture base resin. The method differed from previous test methods because of the specimen's ability to align axially during the test. The results indicated significant differences in the bonding of liners to the denture base, and light-cure systems exhibited the greatest amount of stress needed for failure. Low bond strength was observed when the adhesion was poor or when the cohesive strength of the soft liner was low and lead to pure adhesive or cohesive failure. When both adhesive and cohesive bonds were strong, failure occurred at high stresses. Combinations of adhesive and cohesive failures (mixed mode) were also observed in intermediate cases.