Marginal accuracy of combined tooth-implant-supported fixed dental prostheses after in vitro stress simulation

Caries, periodontal disease, and peri-implant inflammation caused by deficient marginal adaptation of fixed prostheses are reasons for clinical failure of combined tooth-implant-supported fixed dental prostheses (TISFDP). This in vitro study examined the marginal accuracy in TISFDP after simulated stress in an artificial oral environment.

Twelve three-unit TISFDPs were fabricated using a high noble alloy on models containing a human premolar with an artificial periodontium and an implant. Four three-unit tooth-supported prostheses (TSFDP) represented the control group. The experimental TISFDPs (four per group) were luted with three different cements: group 1, zinc phosphate; group 2, glass ionomer; group 3, self-adhesive resin. The specimens were mechanically loaded (1.2 million cycles/50 N) and thermally cycled (8000 cycles with 5/55 degrees C). The vertical marginal gap was measured before and after cementation, after chewing simulation and after thermal cycling by light microscopy (x 560). The results were subjected to statistical analysis (t-test/one-way analysis of variance/Bonferroni).

Significant increase (P< or =0.05) in the marginal gap was found after cementation within the experimental TISFDPs (implants, 11.7-18.7 microm; teeth, 13.4-24.2 microm) and the control TSFDPs (28.5 microm). Comparison of groups 1 and 2 revealed significant differences for the teeth while comparison of the implants showed significant differences among all groups. Chewing simulation and thermal cycling caused statistically insignificant changes in the marginal gaps of the experimental as well as the control TSFDPs.

The cementation of the TISFDPs with different luting materials caused a specific enlargement of the marginal gap in teeth and implants. Subsequent to simulated oral stress in an artificial oral environment, no significant changes of the marginal accuracy could be found.