This article determines the compressive and diametral tensile strength of two titanium-reinforced composites (Bis-GMA-based), Ti-Core and Flexi-Flow cem with titanium and compares their strengths to dentin and commercially available core materials and cements. In addition scanning electron microscope (SEMI photographs were taken of Ti-Core and Flexi-Flow cem with titanium. Compressive and tensile loading was performed on a modifled universal testing apparatus. Ti-Core and Flexi-Flow cem with titanium were measured to have compressive strengths of 41,132 and 41,876 psi and tensile strengths of 5219 and 4930 psi, respectively.Statistically (ANOVA, one-way analysis of variance), these titanium-reinforced composites are stronger in compressive and tensile strength than Ketac-Silver, Flecks zinc cement, Durelon, Ketac-Cem, and GC Miracle Mix. Both titaniumreinforced composite materials approach the compressive and diametral tensile strengths of dentin (43,100 and 6000 psi). SEMs revealed that the titanium was uniformly and homogeneously interspersed within the resin matrix of the material. he use of a composite resin restorative system to T restore teeth due to caries and/or fracture before placement of a crown restoration is well documented in dental literature.'-" Since the development of the dental restorative composite resin system (Bis-GMA-based) by Bowen, researchers have been trying to improve existing composite resin systems and alter their characteristics for improved clinical applications. Studies of fatigue associated with composite resins have shown that there is a strong correlation between fatigue and the compressive and diametral tensile strength of dental composite resin materials. 12.13 The relationship between fatigue and compressive and tensile strength seems to indicate that composite resins with higher compressive and tensile strength will withstand fatigue better and longer.I2 Therefore, a possible way for reducing failure associated with dental composite resins due to age and function is to improve the existing compressive and tensile strengths for these dental restorative materials.Many researchers have found that addition of fillers to resin systems can result in enhanced characteristics
This pilot study compared stress distribution using photoelastic blocks for both vertical loading and oblique loading (26 degrees angle) for four groups of post systems (Flexi-Post, Flexi-Flange, ParaPost and AccessPost dowels). For each group, three test blocks of photoelastic material were prepared with simulated endodontic canals, and the specimens were then photographed. Minimal stresses were observed for all the posts after cementation in the unloaded state. Stress distribution for the Flexi-Post, Flexi-Flange and AccessPost were favourable under vertical loading at 134 N and oblique loadings of 89 N and 134 N. Stress patterns were symmetric over the entire length of these posts. Stress distribution for the ParaPost under vertical loading at 134 N generated stress patterns that were asymmetric with concentration of stresses apically compared to coronally. Stress distribution for the ParaPost during oblique loadings of 89 N and 134 N were asymmetric with stress concentrated apically as compared to coronally. Stress distribution for the Flexi-Post, Flexi-Flange and AccessPost were all favourable under loading conditions studied.
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