The Effect of Multiple Firing on the marginal gap and internal fit of Zirconia Frames to Dental Implant abutments

Today, the use of all-ceramic restorations in dental implants has increased due to proper structural characteristics and excellent esthetics. For more beauty, zirconia frames might be exposed to repetitive firing cycles due to their unfavorable color, leading to increased lack of restoration compliance. Given the effects of marginal gap on inflammation around fixtures and implant failure, this study aimed to evaluate the effects of porcelain multiple firings on marginal gap and internal fit of zirconia frames to dental implant abutments.
In total, 40 abutments were selected and divided into four groups. In the first group, zirconia frames were fabricated at 0.4 mm diameter. The frames were cemented and marginal gap was measured after thermal cycles (magnification: 40X). In addition, the space between the abutment and crown, which was cut with a diamond disc, was measured in order to measure internal fit values (magnification: 40X). While the phases were similarly carried out for the second, third, and fourth groups, the samples were porcelain-fused for two, four, and six times before cementing the implant crown to the abutment, respectively. Moreover, the final porcelain thickness was estimated to be 2 mm, followed by the evaluation of the marginal gap parameters and internal fit values.
In this study, the marginal gap value was reported to be 52-69 micrometers, while the internal fit value was 17-26 micrometers. In terms of marginal gap and internal fit of zirconia frames, no significant difference was observed in the samples after porcelain firing cycles, compared to those with no firing.
According to the results, zirconia was not significantly affected by porcelain firing cycle due to its high mechanical properties, as well as high strength and complete sintering. Moreover, no significant difference was observed in the compliance of zirconia frames with dental implant abutments after multiple firing cycles.