Mechanical integrity of cement- and screw-retained zirconium-lithium silicate glass-ceramic crowns to Morse taper implants

J Prosthet Dent. 2018 Nov;120(5):721-731. doi: 10.1016/j.prosdent.2018.01.028. Epub 2018 Aug 7.


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<.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.

MeSH terms

  • Bone Screws*
  • Ceramics / chemistry
  • Crowns*
  • Dental Cements / chemistry*
  • Dental Implant-Abutment Design*
  • Dental Materials / chemistry
  • Dental Porcelain / chemistry
  • Dental Stress Analysis*
  • In Vitro Techniques
  • Materials Testing
  • Microscopy, Electron, Scanning
  • Titanium / chemistry
  • Torque
  • Zirconium / chemistry


  • Dental Cements
  • Dental Materials
  • lithia disilicate
  • Dental Porcelain
  • Glass ceramics
  • Zirconium
  • Titanium