Mechanical Stability of Screw-Retained Monolithic and Bi-layer Posterior Hybrid Abutment Crowns after Thermomechanical Loading: An In Vitro Study

Abstract

To evaluate the failure-load and survival-rate of screw-retained monolithic and bi-layered crowns bonded to titanium-bases before and after mouth-motion fatigue, 72 titanium-implants (SICvantage-max, SIC-invent-AG) were restored with three groups (n = 24) of screw-retained CAD/CAM implant-supported-single-crowns (ISSC) bonded to titanium-bases: porcelain-fused-to-metal (PFM-control), porcelain-fused-to-zirconia (PFZ-test) and monolithic LDS (LDS-test). Half of the specimens (n = 12/group) were subjected to fatigue in a chewing-simulator (1.2 million cycles, 198 N, 1.67 Hz, thermocycling 5–55 °C). All samples were exposed to single-load-to-failure without (PFM0, PFZ0, LDS0) or with fatigue (PFM1, PFZ1, LDS1). Comparisons were statistically analyzed with t-tests and regression-models and corrected for multiple-testing using the Student–Neuman–Keuls method. All PFM and LDS crowns survived fatigue exposure, whereas 16.7% of PFZ showed chipping failures. The mean failure-loads (±SD) were: PFM0: 2633 ± 389 N, PFM1: 2349 ± 578 N, PFZ0: 2152 ± 572 N, PFZ1: 1686 ± 691 N, LDS0: 2981 ± 798 N, LDS1: 2722 ± 497 N. Fatigue did not influence load to failure of any group. PFZ ISSC showed significantly lower failure-loads than monolithic-LDS regardless of artificial aging (p < 0.05). PFM ISSC showed significantly higher failure loads after fatigue than PFZ (p = 0.032). All ISSC failed in a range above physiological chewing forces. Premature chipping fractures might occur in PFZ ISSC. Monolithic-LDS ISSC showed high reliability as an all-ceramic material for screw-retained posterior hybrid-abutment-crowns.

Influence of ceramic crown design (translucent monolithic zirconia vs. bilayered) of implant‐supported single crowns after mechanical cycling

“…The sample size was determined by the power test focusing on the primary outcome: fracture resistance. The statistical power analysis, based on the study by Spitznagel et al, 16 comparing the fatigue testing fracture resistance of monolithic lithium disilicate to porcelainfused-to-zirconia, revealed that a minimum sample size of n = 9/ group, with a power of 0.97 (effect size d = 1.72), is required for this test, considering an α error probability of 0.05. To ensure an ample sample size, in the present study, the tests were conducted with n = 10/group.…”

“…Despite the methodological variation, previous studies have demonstrated that monolithic zirconia crowns have the lowest chances of chipping, in contrast, bilayered crowns have the highest chance. [14][15][16] Honda et al 14 showed that monolithic screw-retained implant-supported was significantly more fracture-resistant than bilayered crowns. Spitznagel et al 16 showed that porcelain-fused-to-metal, porcelainfused-to-zirconia, and monolithic crown bonded to titanium under thermomechanical cycling, and monolithic crown showed high reliability as an all-ceramic material for screw-retained posterior hybridabutment-crowns.…”

“…[14][15][16] Honda et al 14 showed that monolithic screw-retained implant-supported was significantly more fracture-resistant than bilayered crowns. Spitznagel et al 16 showed that porcelain-fused-to-metal, porcelainfused-to-zirconia, and monolithic crown bonded to titanium under thermomechanical cycling, and monolithic crown showed high reliability as an all-ceramic material for screw-retained posterior hybridabutment-crowns. Sahebi et al 15 evaluated the fracture resistance of monolithic zirconia, porcelain-veneered zirconia, and a control group of porcelain-fused-to-metal under thermocycling and concluded that monolithic zirconia presented higher fracture resistance than the bilayered restorations for screw-cement retained implantsupported restorations.…”

“…Sahebi et al 15 evaluated the fracture resistance of monolithic zirconia, porcelain-veneered zirconia, and a control group of porcelain-fused-to-metal under thermocycling and concluded that monolithic zirconia presented higher fracture resistance than the bilayered restorations for screw-cement retained implantsupported restorations. However, few studies [16][17][18][19] have evaluated fatigue and fracture resistance of translucent monolithic zirconia crowns and the use of CoCr base abutments under chewing simulating.…”