In vitro damping and strain distribution for implant-supported crowns using 5 different CAD-CAM crowns and 3 different luting cements.

Statement Of Problem: Dental implants are particularly susceptible to occlusal overloading because, unlike natural teeth, they lack a periodontal ligament to help absorb occlusal forces. However, studies evaluating the impact of different crown and luting materials on the damping behavior and strain distribution of implant-supported crowns are lacking.

Purpose: The purpose of this in vitro study was to investigate the damping behavior and strain distribution of peri-implant bone associated with 5 different CAD-CAM implant-supported crowns and 3 luting materials.

Material And Methods: A titanium implant was embedded in a plastic tube with epoxy resin and 5 different crown materials (polymethyl methacrylate, resin-infiltrated ceramic, lithium disilicate, titanium, and zirconia) luted to prosthetic abutments with 3 different luting materials (zinc oxide non-eugenol cement, zinc phosphate cement, and adhesive resin cement) and an uncemented condition were tested (n=5). Strain gauges were attached at the crestal and apical levels of the implant model. All specimens were load tested from 0 to 200 N. Slopes of load/time, microstrain/time, and time required to reach the maximum load were examined to represent the damping behavior. Absolute maximum strain (AMS) and its occurrence level were examined to represent the strain distribution. Two-way ANOVA, followed by the Tukey HSD test, were used for statistical analysis (α=.05).

Results: All slopes and times to reach the maximum load in each crown material were statistically similar (P>.05), except for the polymethyl methacrylate group, which showed less steepness in all slopes and more time required to reach the maximum load significantly (P<.05). Both the polymethyl methacrylate group (224.5 ±30.2) and the titanium group (224.0 ±24.3) exhibited significantly higher AMS at the crestal level compared with the resin-infiltrated ceramic group (210.6 ±5.0) (P<.05). The lithium disilicate (218.1 ±15.0) and zirconia groups (217.3 ±14.8) demonstrated comparable AMS values with the others (P>.05). The uncemented group demonstrated steeper slopes and less time required to reach the maximum load compared with the adhesive resin group (P<.05), while slopes and times of the zinc phosphate and zinc oxide non-eugenol groups were comparable (P>.05). The uncemented group (242.7 ±25.3) exhibited significantly higher AMS at the crestal level than the other groups (P<.05).

Conclusions: The crown material significantly affected the damping behavior of peri-implant bone, unlike the luting material. Polymethyl methacrylate with a high damping behavior exhibited high strain at the crestal level. In contrast, resin-modified ceramic with a moderate damping behavior exhibited low strain at the crestal level. Strain at the crestal level could be effectively reduced by approximately 13% through cementation.