title: 3-Year Randomized Controlled Prospective Clinical Trial on Different CAD-CAM Implant Abutments.
abstract: BACKGROUND
  Zirconia abutments were introduced to restore esthetic regions and showed sufficient stability to support implant restorations. Nonetheless, to date the observation periods are shorter than those of titanium abutments.
  
  
  OBJECTIVE
  To assess the survival of implant crowns supported by computer aided design-computer aided manufacturing (CAD-CAM) abutments after 3 years.
  
  
  METHODS
  Fifty-six patients were selected for this prospective clinical study. Each patient received at least 1 titanium implant for a total of 89 fixtures. A two-stage surgical technique and no additional soft or hard tissue graft were used. The implants were randomly divided into 3 groups receiving different CAD-CAM abutments: titanium, titanium nitride, and zirconia. Zirconia or metal-ceramic crowns were used as final restorations. Cementation was the baseline and the restorations were checked after 6 months, 1, 2, and 3 years, assessing any mechanical complication. Statistical analyses were performed to evaluate the 3-year success rates.
  
  
  RESULTS
  Five failures were reported in the zirconia group; all the failed restorations showed fractures of the abutment connection. Four failures occurred in posterior regions and one more occurred while screwing the abutment. Titanium and titanium nitride abutments had significantly higher 3-year success rates than zirconia abutments (p < .05).
  
  
  CONCLUSIONS
  Atlantis titanium and titanium nitride abutments showed optimal clinical performances after 3 years. Conversely, Atlantis zirconia abutments should be avoided to restore posterior regions.
authors.affiliation: Professor and Chair, Department of Prosthodontics and Dental Materials, University of Siena, Siena, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Ferrari
authors.affiliation: PhD Student, Department of Prosthodontics and Dental Materials, University of Siena, Siena, Italy.
authors.forename: Maria Gabriella
authors.initials: MG
authors.lastname: Tricarico
authors.affiliation: Assistant Professor, Department of Prosthodontics and Dental Materials, University of Siena, Siena, Italy.
authors.forename: Maria Crysanti
authors.initials: MC
authors.lastname: Cagidiaco
authors.affiliation: Research Professor, Department of Prosthodontics and Dental Materials, University of Siena, Siena, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vichi
authors.affiliation: Professor and Chair, Department of Dentistry, University "Vita Salute San Raffaele" of Milan, Milan, Italy.
authors.forename: Enrico Felice
authors.initials: EF
authors.lastname: Gherlone
authors.affiliation: Professor and Chair, Department of Neurosciences, Reproductive and Odontostomatological Sciences, University "Federico II" of Naples, Naples, Italy.
authors.forename: Fernando
authors.initials: F
authors.lastname: Zarone
authors.affiliation: Research Professor, Department of Prosthodontics and Dental Materials, University of Siena, Siena, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Sorrentino
mesh_terms: D017076:Computer-Aided Design; D059605:Dental Implant-Abutment Design; D006801:Humans; D011446:Prospective Studies; D011475:Prosthesis Failure
keywords: clinical trial; computer aided design-computer aided manufacturing; implant abutment; prosthodontics; zirconia