Effect of implant connection and restoration design (screwed vs. cemented) in reliability and failure modes of anterior crowns

Amilcar C. Freitas, Estevam A. Bonfante, Eduardo P. Rocha, Nelson R.F.A. Silva, Leonard Marotta, Paulo G. Coelho

Research output: Contribution to journalArticlepeer-review


The mechanical performance of cemented or screw-retained implant-supported crowns with an internal or external configuration is yet to be understood. This in vitro study evaluated the effect of screw-retained and cement-retained prostheses on internal and external implant-abutment connections. Thereby, the reliability and failure modes of crowns were investigated. Eighty-four implants (Emfils; Colosso Evolution system) were divided into four groups (n=21 each): screw-retained and internal connection (Si), screw-retained and external connection (Se), cement-retained and internal connection (Ci), and cement-retained and external connection (Ce). Ti-6Al-4V abutments were torqued (30Ncm) to the implants, and maxillary central incisor metal crowns were torqued (30Ncm) or cemented (Rely X Unicem; 3M-ESPE) and subjected to accelerated life-testing in water. Use-level probability Weibull curves and reliability for 50,000 cycles at 150 N were calculated. The β values for Si (1.72), Se (1.50), Ci (1.34), and Ce (1.77) groups indicated that fatigue/damage accumulation accelerated their failure. The Ci group presented the highest reliability, the Se group presented the lowest reliability, and Si and Ce groups presented intermediate reliability. Screw-retained restorations presented mainly abutment fracture. Cement-retained restorations resulted in failures of the screw in the Ce group, but implant/screw fracture in the Ci group.

Original languageEnglish (US)
Pages (from-to)323-330
Number of pages8
JournalEuropean Journal of Oral Sciences
Issue number4
StatePublished - Aug 2011


  • Cement-retained
  • Fractography
  • Implant-supported prostheses
  • Reliability
  • Screw-retained

ASJC Scopus subject areas

  • General Dentistry


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