3D EVALUATION OF MICROGAPS AT THE IMPLANT-ABUTMENT CONNECTION BEFORE AND AFTER THERMODYNAMIC CYCLING.

Purpose: To analyze the microgap changes between hybrid-abutment crowns made of two materials and three internal taper connec9on implants with different connection designs before and after thermodynamic loading.

Materials and methods: A total of 30 implants-10 each of Straumann Bone Level Implant-RC (STR); GC AADVA Implant (AAD); and Astra-Tech OsseoSpeed EV (AST)-were included in this laboratory study. Each implant had an internal taper connection, but their designs were slightly different. Five hybrid-abutment crowns were fabricated using a lithium disilicate ceramic (LD), and five were fabricated using polymethylmethacrylate (PMMA) with CAD/CAM technologies for each implant system, providing six sample groups STR-LD, AAD-LD, AST-LD, STR-PMMA, AAD-PMMA, and ASTPMMA. The microgap volume was measured using micro-CT images obtained before and after thermodynamic loading equivalent to 4 months of clinical use. Student t test, one-way ANOVA, and Tukey test were used for comparisons.

Results: The greatest microgap volume increase was recorded (3.405% ± 1.567%) in the AST-LD group, and the lowest increase (0.45% ± 0.373%) was in the STR-PMMA group. A statistically significant difference in microgap increase was not detected among PMMA and LD groups: for STR-LD/STR-PMMA (t test: P = .273); for AAD-LD/AAD-PMMA (t test: P = .374); and for AST-LD/AST-PMMA (t test: P = .268). However, the difference in the microgap increase between the different implant systems was statistically significant.

Conclusions: The microgap between hybrid-abutment crowns and implants increased after short-term thermodynamic cycling. Hybrid-abutment crowns with different elastic modulus showed similar microgap increase. The geometric shape of the connection influenced the microgap increase.