Monotonic flexure and fatigue strength of composites for provisional and definitive restorations.
BACKGROUND
Ordinarily, the mechanical strength of composites is characterized by their flexural strength. Information as to the material's fatigue strength is seldom provided.


OBJECTIVE
The purpose of this study was to compare the flexural strength and the resistance to fatigue loading of composites and an acrylic resin for provisional and definitive restorations.


METHODS
Artglass, Colombus, and Targis (composites) and Jet, Protemp II, Protemp Garant, and Provipont DC (provisional restorations) were subjected to mechanical tests. Fatigue tests (MPa) (n = 30 specimens/group) were conducted with the rotating-bending cantilever design. Monotonic flexural strength (MPa) (n = 10) was determined in 3-point bending tests. Fatigue resistance was analyzed via the staircase procedure, and flexural strength was examined by use of the 2-parameter Weibull distribution (confidence intervals at 95%).


RESULTS
The mean fatigue resistances (S(50)) in MPa +/- SD were: Targis, 62.1 +/- 7.0; Artglass, 58.5 +/- 3.7; Colombus, 54.6 +/- 6.2; Provipont DC, 29.5 +/- 3.2; Protemp II, 23.1 +/- 5.3; Jet, 22.8 +/- 8.3; Protemp Garant, 19.6 +/- 4.6. The flexure strengths (Weibull's S(0)) in MPa and their shape parameters (m) were: Colombus, 145.2 (13.1); Targis, 110.3 (7.8); Artglass, 5.9 (5.4); Jet, 150.9 (17.3); Provipont DC, 97.3 (23.8); Protemp II, 57.9 (6.4); Protemp Garant, 54.2 (12.8). The S(50) of Targis was significantly higher than that of Colombus but not different from Artglass. In flexion, the S(0) of Colombus was significantly higher than that of Artglass and Targis. The S(50) ranged between 40% and 60% of the S(0) for the composites and between 15% and 30% for the provisional restorative materials.


CONCLUSIONS
Correlations between monotonic flexure strength and resistance to fatigue loading were weak. Because fatigue tests are considered more pertinent than monotonic tests as to their predictive value, it is concluded that flexure strength data alone may not provide relevant information for long-term clinical performance. The material's resistance to fatigue loading should also be determined.
Scherrer
Susanne S
SS
School of Dental Medicine, University of Geneva, Switzerland. susanne.scherrer@medecine.unige.ch
Wiskott
Anselm H W
AH
Coto-Hunziker
Viviana
V
Belser
Urs C
UC
D000180:Acrylic Resins / Q000737:chemistry*; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D016001:Confidence Intervals; D003793:Dental Restoration, Permanent; D003794:Dental Restoration, Temporary; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D008768:Methylmethacrylates / Q000737:chemistry; D018583:Pliability; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012399:Rotation; D012823:Silicate Cement / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
D000180:Acrylic Resins; D003188:Composite Resins; D005899:Glass Ionomer Cements; D008768:Methylmethacrylates; C106970:Provipont system; C111282:dental polyglass; C069716:Jet, dental resin; D012823:Silicate Cement; D017438:Bisphenol A-Glycidyl Methacrylate; D019904:Polymethyl Methacrylate; C069714:Protemp