Comparison of Strains for Splinted and Nonsplinted Implant Prostheses Using Three-Dimensional Image Correlation

Purpose: This study aimed to analyze and compare strain distribution patterns for splinted and nonsplinted restorations for dental implants with an internal conical connection. Materials and Methods: Two stereolithic acrylic resin models were created using computed tomographic scan data from a patient missing all mandibular molar teeth. Two implants were placed in the right side of two mandibular models using a computer-generated surgical guide and appropriate protocol. The first model received 5 3 13-mm implants, and the second received 5 3 11-mm implants. Three splinted and three nonsplinted sets of gold screw-retained prostheses were created to fit the implants on each of the two stereolithic models. The 3D image correlation technique was used for full-field measurement of strains using commercial image correlation software and a pair of high-resolution digital cameras, which provided a synchronized stereo view of the models during the experiment. Static loads of up to 203 N were applied in vertical and oblique directions. Strain distribution data were compared for major and minor strains. A mixed-models analysis of variance was done to evaluate all main effect and two-way interactions for each strain, and P values were corrected for multiple comparisons using the step-down Bonferroni adjustment. Results: Evidence of increased load sharing for the splinted prostheses compared to the nonsplinted prostheses was shown. Strain distribution data represented by the ratio of anterior and posterior peak strains were not statistically different for the splinted and nonsplinted prostheses for either implant length. Conclusions: Splinted prostheses generated more uniform strain distributions; however, the strain distribution data were not statistically different from that seen for the nonsplinted prostheses. This suggests that splinting may not be significant for internally connected implants when the crown-to-implant ratio is less than 1. However, clinical corroboration of these findings is required. Keywords: crowns, dental implants, splinting, strains