Fracture resistance of implant-supported screw- versus cement-retained porcelain fused to metal single crowns: SEM fractographic analysis

Dent Mater. 2007 Mar;23(3):296-301. doi: 10.1016/j.dental.2005.10.013. Epub 2006 Mar 24.

Abstract

Objectives: The present in vitro study aimed at evaluating the fracture resistance of both implant-supported screw- and cement-retained porcelain fused to metal (PFM) single crowns. A scanning electron microscope (SEM) evaluation of the mode of failure of the specimens was also performed.

Methods: Forty PFM premolar-shaped identical single crowns were realized. The restorations were divided into two groups: cement-retained (group 1) and screw-retained (group 2) prostheses. Compressive loading tests and SEM fractographic analyses were performed. The data were statistically analysed by means of the Student's t-test, with a confidence interval of 95%.

Results: The mean fracture load value was 1657 (+/-725) N in group 1 and 1281 (+/-747) N in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.115). The mean work at maximum load value was 0.775 (+/-0.619) J in group 1 and 0.605 (+/-0.526) J in group 2; the statistical analysis pointed out no significant differences between the two groups (p=0.355). All the samples were affected by cohesive fractures of the porcelain. Screw-retained crowns showed microcracks at the level of the occlusal access to the screw and extensive fractures in the whole thickness of the ceramics. On the contrary, cement-retained restorations were affected by less wide paramarginal fractures of the porcelain.

Significance: A stronger implant-prosthetic connection was noticed in cemented restorations group than in screw-retained single crowns. Even though negatively influenced by the presence of the occlusal access to the screw, the metal-ceramics bond can be considered predictable in both the implant-prosthetic connection systems analysed.

Publication types

  • Comparative Study

MeSH terms

  • Cementation
  • Compressive Strength
  • Crowns*
  • Dental Implants, Single-Tooth*
  • Dental Prosthesis Retention / instrumentation
  • Dental Prosthesis Retention / methods*
  • Dental Prosthesis, Implant-Supported*
  • Dental Restoration Failure*
  • Dental Stress Analysis
  • Metal Ceramic Alloys
  • Microscopy, Electron, Scanning

Substances

  • Metal Ceramic Alloys