Fracture resistance of implant-supported monolithic crowns cemented to zirconia hybrid-abutments: zirconia-based crowns vs. lithium disilicate crowns

Abstract

PURPOSEThe aim of this in vitro study was to investigate the fracture resistance under chewing simulation of implant-supported posterior restorations (crowns cemented to hybrid-abutments) made of different all-ceramic materials.MATERIALS AND METHODSMonolithic zirconia (MZr) and monolithic lithium disilicate (MLD) crowns for mandibular first molar were fabricated using computer-aided design/computer-aided manufacturing technology and then cemented to zirconia hybrid-abutments (Ti-based). Each group was divided into two subgroups (n=10): (A) control group, crowns were subjected to single load to fracture; (B) test group, crowns underwent chewing simulation using multiple loads for 1.2 million cycles at 1.2 Hz with simultaneous thermocycling between 5℃ and 55℃. Data was statistically analyzed with one-way ANOVA and a Post-Hoc test.RESULTSAll tested crowns survived chewing simulation resulting in 100% survival rate. However, wear facets were observed on all the crowns at the occlusal contact point. Fracture load of monolithic lithium disilicate crowns was statistically significantly lower than that of monolithic zirconia crowns. Also, fracture load was significantly reduced in both of the all-ceramic materials after exposure to chewing simulation and thermocycling. Crowns of all test groups exhibited cohesive fracture within the monolithic crown structure only, and no abutment fractures or screw loosening were observed.CONCLUSIONWhen supported by implants, monolithic zirconia restorations cemented to hybrid abutments withstand masticatory forces. Also, fatigue loading accompanied by simultaneous thermocycling significantly reduces the strength of both of the all-ceramic materials. Moreover, further research is needed to define potentials, limits, and long-term serviceability of the materials and hybrid abutments.

Strength and aging resistance of monolithic zirconia: an update to current knowledge

“…According to Rohr et al [74], the use of resin cements with high compressive strength was found to be correlated linearly to fracture resistance and flexural strength of implant-supported monolithic zirconia crowns. Elshiyab et al [90] proved that after 5 years equivalent chewing simulation, implant retained monolithic zirconia crowns survived, although their resistance to fracture had decreased.…”

“…The highest resistance was observed for zirconia crowns. All specimens survived the mastication simulation.N/AThermal and mechanical cycling 5000 cycles, 5°-55 °C, waterMechanical loading 100 N, 12 × 10 5 cycles.Sarıkaya et al (2018) [87]- BruxzirFracture strength, crosshead speed 1 mm min −1 (crowns: force applied on buccal and lingual cusps, FPDs: force applied on occlusal connector area).- No fractures during chewing simulationN/A- Incoris TZIAging: thermocycling (10,000 cycles /5–55 °C / dwell time = 60 s / transfer time = 10 s,- Bruxzir crowns and FPDs presented significantly higher fracture strength compared to Incoris TZIDual axis chewing simulator with a total of 1,200,000 cycles.- No significant difference in fracture strength of crowns and FPDs fabricated from BruxzirWeigl et al (2018) [85]Zirkon BioStar HTFracture strength, crosshead speed 1 mm min −1 - All 0.5 mm crowns exceeded 900 N.N/AAging: chewing simulation (1,200,000 cycles, 50 N, f = 1.6 Hz))− 0.2 mm adhesively cemented control crowns exceeded 900 N.Thermal cycling (2 × 3000 between 5 °C and 55 °C, 2 minutes for each cycle)Elshiyab et al (2018) [90]-Zenostar ZrFracture strength, crosshead speed 1 mm min −1 - Monolithic lithium disilicate crowns presented lower fracture strength compared to monolithic zirconiaN/A- IPS e.max- CADAging: fatigue by chewing simulation with 1.2 million cycles + thermal cycling at 5–55 °C in distilled water (5118 thermal cycles with 60 s dwell time for each cycle, 15 s pause time).- All crowns presented a reduction in fracture strength following fatigue aging.Yin et al [89](2019)A3 12 T, Liaoning Upcera, Benxi, ChinaFracture strength, crosshead speed 1 mm min −1 After polishing the crown presented higher fracture strengths than after adjustment of occlusal contactNot calculated but observed in the diffraction patterns depending on the polishing methodDifferent polishing protocols were evaluated. Cementation using resin cement.Chewing simulation with cyclic loads between 2 and 300 N, frequency 1 Hz (100,000 cycles)Elsayed et al (2019) […”

The Micro-Shear bond strength of different cements to commercially pure titanium

“…Thus, the hybrid abutment is developed by combining the Ti strength and the esthetic nature of ceramic materials (8). Drawing upon previous statements, the clinical success of the hybrid abutment depends on the cementation technique used to create a link between the ceramic and the metal (Ti).…”

Influence of crown and hybrid abutment ceramic materials on the stress distribution of implant-supported prosthesis

“…The proposal of using an hybrid abutment is very interesting so that unitary crowns with a great ceramic volume would have similar aesthetic characteristics to the adjunctive teeth, which is not always possible with conventional abutments 5,6 . Hybrid abutment are suggested to present mechanical properties similar to titanium abutments 4,7,8 and promising durability and strength after long-term 9 .…”