title: Effects of framework design and layering material on fracture strength of implant-supported zirconia-based molar crowns.
abstract: OBJECTIVE
  To evaluate the effects of framework design and layering material on the fracture strength of implant-supported zirconia-based molar crowns.
  
  
  METHODS
  Sixty-six titanium abutments (GingiHue Post) were tightened onto dental implants (Implant Lab Analog). These abutment-implant complexes were randomly divided into three groups (n = 22) according to the design of the zirconia framework (Katana), namely, uniform-thickness (UNI), anatomic (ANA), and supported anatomic (SUP) designs. The specimens in each design group were further divided into two subgroups (n = 11): zirconia-based all-ceramic restorations (ZAC group) and zirconia-based restorations with an indirect composite material (Estenia C&B) layered onto the zirconia framework (ZIC group). All crowns were cemented on implant abutments, after which the specimens were tested for fracture resistance. The data were analyzed with the Kruskal-Wallis test and the Mann-Whitney U-test with the Bonferroni correction (α = 0.05).
  
  
  RESULTS
  The following mean fracture strength values (kN) were obtained in UNI design, ANA design, and SUP design, respectively: Group ZAC, 3.78, 6.01, 6.50 and Group ZIC, 3.15, 5.65, 5.83. In both the ZAC and ZIC groups, fracture strength was significantly lower for the UNI design than the other two framework designs (P = 0.001). Fracture strength did not significantly differ (P > 0.420) between identical framework designs in the ZAC and ZIC groups.
  
  
  CONCLUSIONS
  A framework design with standardized layer thickness and adequate support of veneer by zirconia frameworks, as in the ANA and SUP designs, increases fracture resistance in implant-supported zirconia-based restorations under conditions of chewing attrition. Indirect composite material and porcelain perform similarly as layering materials on zirconia frameworks.
authors.affiliation: Department of Fixed Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Kamio
authors.affiliation: Department of Fixed Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Futoshi
authors.initials: F
authors.lastname: Komine
authors.affiliation: Department of Fixed Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Taguchi
authors.affiliation: Department of Fixed Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Iwasaki
authors.affiliation: Department of Preventive and Restorative Sciences, University of Pennsylvania School of Dental Medicine, Philadelphia, PA, USA.
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
authors.affiliation: Department of Fixed Prosthodontics, Nihon University School of Dentistry, Tokyo, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Matsumura
mesh_terms: D017076:Computer-Aided Design; D003442:Crowns; D059605:Dental Implant-Abutment Design; D019094:Dental Prosthesis, Implant-Supported; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D066298:In Vitro Techniques; D008963:Molar; D011897:Random Allocation; D014025:Titanium; D015040:Zirconium
chemical_list: D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide
keywords: dental implant; fracture strength; framework design; indirect composite material; zirconia ceramics