Bending moments and types of failure of zirconia and titanium abutments with internal implant-abutment connections: a laboratory study.

PURPOSE: The aim of this study was to examine the bending moments and fracture patterns of different zirconia abutments with internal implant-abutment connections after static loading and to compare their bending moments to those of internally connected titanium abutments. MATERIALS AND METHODS: Three types of customized zirconia abutments (Straumann CARES abutments/Straumann BL implants [T1], Astra ZirDesign abutments/Astra Micro Thread OsseoSpeed implants [T2], Zirabut prototype abutments/Straumann SP implants [T3]) and one type of customized titanium abutment (control group, Straumann CARES abutments/Straumann BL implants [C]) were included. All abutments were one-piece abutments with an internal implant-abutment connection and were customized to the same shape but featured different implant-abutment connection designs. For each group, 20 identical copies of a master abutment were fabricated and fixed on their corresponding implants. Half of the abutments in each group were left unrestored, and the other 10 received glass-ceramic crowns. Static loading was applied at a 30-degree angle to the palatal surface until failure, and bending moments were calculated. The type of failure was characterized visually by dismounting the abutments and by examination of cross-sections of the embedded specimens. The results were analyzed statistically. RESULTS: The mean range of bending moments was higher for the unrestored groups (158.2 to 678.2 Ncm) than for the restored groups (117.9 to 419.4 Ncm). The highest mean bending moments were seen in the control group, both restored and unrestored (419.4/678.2 Ncm). Unrestored, T1 and T2 exhibited significantly higher bending moments than T3. This was also observed in the restored groups. CONCLUSION: Both the abutment material and the implant-abutment connection design affected the bending moments of abutments after static loading. Internally connected zirconia abutments with horizontal mismatch to the implant exhibited significantly higher bending moments compared to those without horizontal mismatch.

Bending moments of zirconia and titanium abutments with internal and external implant-abutment connections after aging and chewing simulation.

OBJECTIVES: To test the fracture load of zirconia abutments with different types of implant-abutment connections after chewing simulation and to compare their bending moments to internally connected identical titanium abutments. MATERIALS AND METHODS: Forty-eight identical customized zirconia abutments with different implant-abutment connections were fabricated for four different test groups: one-piece internal implant-abutment connection (BL; Straumann Bonelevel), two-piece internal implant-abutment connection (RS; Nobel Biocare Replace Select), external implant-abutment connection (B; Brånemark MK III), two-piece internal implant-abutment connection (SP; Straumann Standard Plus). Twelve titanium abutments with one-piece internal implant-abutment connection (T; Straumann Bonelevel) served as control group. After aging by means of thermocycling (5-50°C, 120 s) and chewing simulation (1,200,000 cycles, 49 N load, 1.67 Hz), static load was applied at a 30° angle to the palatal surface until failure. Bending moments were calculated for comparison of the groups. Data were analyzed descriptively and by performing the Kruskal-Wallis test with Bonferroni correction. RESULTS: The mean bending moments of the abutments were 714.1 ± 184.9 N cm (T), 331.7 ± 57.8 N cm (BL), 429.7 ± 62.8 N cm (RS), 285.8 ± 64.4 N cm (B) and 379.9 ± 59.1 N cm (SP). The bending moments of control group T were significantly higher than those of all other groups. The values of group RS were significantly higher than those of group B but within the value range of groups SP and BL. CONCLUSION: The bending moments of the different tested types of zirconia abutments vary with different implant-abutment connections after chewing simulation. The use of a secondary metallic component might have a beneficial influence on the stability of zirconia abutments.