• Vahey, Brendan R.
• Henriques, Bruno
• Sordi, Mariane B.
• Oliveira, Antonio P. Novaes De
• Stanley, Kyle
• Matias De Souza, Júlio César
• Fredel, Márcio C.
• Magini, Ricardo S.

Abstract

<p>Statement of problem: The improved esthetics of ceramic dental prostheses has increased their popularity, although their high elastic modulus and low fracture toughness and tensile strength may reduce the long-term performance of dental prostheses. Purpose: The purpose of this in vitro study was to assess the mechanical integrity of zirconium-lithium silicate glass-ceramic crowns cement- and screw-retained to a titanium implant-abutment after fatigue. Material and methods: Forty titanium implants were placed in polyacetal to mimic bone support. Abutments were tightened to the implants to 20 Ncm by using a digital handheld torque meter. The implant abutment assemblies received a pressed maxillary premolar crown, either lithium disilicate (LD) or zirconium-lithium silicate glass-ceramic (LZS). The specimens (n=10) were subjected to fatigue at 200 N and 5 Hz for 500 000 cycles in a Ringer electrolytic solution (37°C). After fatigue, the crowns were removed to evaluate removal torque values on the implant-abutment connection. The remaining crown-implant-abutment assemblies were cross-sectioned at 90 degrees to the implant-abutment joint for inspection of cracks and the micro-gaps by scanning electron microscopy. Results: Removal torque values before fatigue were recorded at 18 ±1.63 Ncm for the LD group and 18.2 ±0.81 Ncm for the LZS group. After fatigue, the removal torque values decreased significantly (12.8 ±1.6 Ncm for LD, 14.9 ±1.08 Ncm for LZS; P&lt;.05). Micro-gaps at the implant-abutment connections were measured at 0.9 ±0.3 μm before fatigue and at 4.2 ±0.9 μm after fatigue. Cracks were detected at the crown adhesive or at the adhesive-abutment interface for both systems after fatigue. Conclusions: Cement- and screw-retained implant zirconium-lithium silicate glass-ceramic crowns revealed effective fatigue resistance on mean cyclic loading in an electrolyte solution. However, mechanical instability of the crown-adhesive-abutment interfaces and implant-abutment joints was detected after fatigue.</p>

Topics

• scanning electron microscopy
• glass
• glass
• zirconium
• crack
• strength
• fatigue
• cement
• titanium
• Lithium
• tensile strength
• ceramic
• fracture toughness