The effect of thermomechanical aging on the retention of a conometric system in a chewing simulator

To evaluate the retention force of a novel conometric system after thermomechanical aging. In addition, the conometric system's retention force was compared with that of the cemented implant-retained crowns.

Two systems to retain implant crowns were tested in this study: a conometric system and a cement-retained system. Forty-eight zirconia crowns were fabricated using computer-aided design and computer-aided manufacturing technology. Twenty-four zirconia crowns were cemented onto conometric caps with resin-modified glass ionomer cement, which were then connected with abutments. These specimens were divided into three groups, and each group was subjected to the pull-out test. A-control group: 12 specimens directly subjected to pull-out test; A-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out test; A-repeat group: After the pull-out, the specimens in the aging group (A-aged) were reconnected, and the pull-out test was repeated once more. The remaining 24 zirconia crowns were cemented on standard abutments with zinc phosphate cement, and two groups were formed. C-control group: 12 specimens directly subjected to the pull-out test; C-aged group: 12 specimens subjected to thermomechanical aging followed by pull-out. Scanning electron microscope (SEM) was used to evaluate the surfaces of caps and abutments. To analyze the data, repeated measures, one-way ANOVA, and Bonferroni tests were used (p < 0.05).

The mean retention force value of the A-control group was 148.22 ± 16.37 N. The highest mean retention force value was measured in the A-aged group (204.93 ± 51.67 N), and the lowest mean retention force value was seen in the A-repeated group (77.02 ± 21.48 N). Thermomechanical aging had a significant influence (p < 0.05) on both systems. No significant differences in retention force were found between the thermomechanical aged groups of both systems (p > 0.05). SEM analysis revealed that aging had an impact on the surface of the conometric system's caps and abutments.

The retention force of the conometric system increased significantly following thermomechanical aging. No crown separation occurred during the thermomechanical aging of the conometric system. There was no significant difference in the retention of the conometric and cemented systems after thermomechanical aging.