title: Effect of airborne-particle abrasion and mechanico-thermal cycling on the flexural strength of glass ceramic fused to gold or cobalt-chromium alloy.
abstract: OBJECTIVE
  To evaluate the effect of airborne-particle abrasion and mechanico-thermal cycling on the flexural strength of a ceramic fused to cobalt-chromium alloy or gold alloy.
  
  
  METHODS
  Metallic bars (n = 120) were made (25 mm × 3 mm × 0.5 mm): 60 with gold alloy and 60 with Co-Cr. At the central area of the bars (8 mm × 3 mm), a layer of opaque ceramic and then two layers of glass ceramic (Vita VM13, Vita Zahnfabrick) were fired onto it (thickness: 1 mm). Ten specimens from each alloy group were randomly allocated to a surface treatment [(tungsten bur or air-particle abrasion (APA) with Al(2) O(3) at 10 mm or 20 mm away)] and mechanico-thermal cycling (no cycling or mechanically loaded 20,000 cycles; 10 N distilled water at 37°C and then thermocycled 3000 cycles; 5°C to 55°C, dwell time 30 seconds) combination. Those specimens that did not undergo mechanico-thermal cycling were stored in water (37°C) for 24 hours. Bond strength was measured using a three-point bend test, according to ISO 9693. After the flexural strength test, failure types were noted. The data were analyzed using three factor-ANOVA and Tukey's test (α= 0.05).
  
  
  RESULTS
  There were no significant differences between the flexural bond strength of gold and Co-Cr groups (42.64 ± 8.25 and 43.39 ± 10.89 MPa, respectively). APA 10 and 20 mm away surface treatment (45.86 ± 9.31 and 46.38 ± 8.89 MPa, respectively) had similar mean flexural strength values, and both had significantly higher bond strength than tungsten bur treatment (36.81 ± 7.60 MPa). Mechanico-thermal cycling decreased the mean flexural strength values significantly for all six alloy-surface treatment combinations tested when compared to the control groups. The failure type was adhesive in the metal/ceramic interface for specimens surface treated only with the tungsten bur, and mixed for specimens surface treated with APA 10 and 20 mm.
  
  
  CONCLUSIONS
  Considering the levels adopted in this study, the alloy did not affect the bond strength; APA with Al(2) O(3) at 10 and 20 mm improved the flexural bond strength between ceramics and alloys used, and the mechanico-thermal cycling of metal-ceramic specimens resulted in a decrease of bond strength.
authors: Department of Dental Materials and Prosthodontics, State University of São Paulo (UNESP), São Jose dos Campos, Brazil.
authors: Luis Gustavo
authors: LG
authors: Oliveira de Vasconcellos
authors: Lucas H
authors: LH
authors: Silva
authors: Luana Marotta
authors: LM
authors: Reis de Vasconcellos
authors: Ivan
authors: I
authors: Balducci
authors: Fernando E
authors: FE
authors: Takahashi
authors: Marco Antonio
authors: MA
authors: Bottino
mesh_terms: D020906:Air Abrasion, Dental; D000537:Aluminum Oxide; D000538:Aluminum Silicates; D002858:Chromium Alloys; D003035:Cobalt; D003722:Dental Alloys; D001840:Dental Bonding; D003799:Dental Stress Analysis; D006047:Gold Alloys; D006358:Hot Temperature; D008422:Materials Testing; D016876:Metal Ceramic Alloys; D018583:Pliability; D017680:Potassium Compounds; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D002858:Chromium Alloys; D003722:Dental Alloys; D006047:Gold Alloys; D016876:Metal Ceramic Alloys; D017680:Potassium Compounds; C016447:feldspar; D003035:Cobalt; D000537:Aluminum Oxide