ABSTRACT
Objective:To explore the influence of the veneering porcelain thickness on the compressive strength of zirconia all-ceramic crown.Methods:25 zirconia basement crowns with the thickness of 0.5 mm were made by CAD-CAMsystem,and then were divided into 5 groups randomly with the veneering porcelain thickness of 0.5(A),1.0(B),1.5(C),2.0(D)and 2.5 mm(E)respectively. The compressive strength of the samples was measured by a testing machine.Statistical analysis was conducted by SPSS13.0 software. The microstructure of the fractured bonding interface of the specimens was observed by scanning electron microscope(SEM).Results:The compressive strength in group A,B,C,D and E were:(1 279.96 ±42.85)N,(2 235.44 ±50.14)N,(2 216.38 ±48.97)N, (2 169.22 ±60.40)N and (2 028.70 ±47.37)N respectively(A or E vs B,C or D,P 0.05;C vs D,P >0.05).SEMobservation found that in group A and E the bonding interface was uneven and loose,the cracks and spores in veneering porcelain appeared more and larger,and had a more intensive distribution.Conclusion:When the veneering porce-lain is too thick or too thin,the compressive strength of zirconia all-ceramic crown decreases,the thickness of the veneering porcelain should be controled in an appropriate range.
ABSTRACT
BACKGROUND:Based on variational principle and weighting technology of three-dimensional finite element method, human teeth with a complex morphology can be modeled, which helps to understand the stress distribution of dental hard tissue and prosthesis during the dynamic repair process. OBJECTIVE:To comprehensively analyze the three-dimensional finite element studies concerning biomechanics of dental prostheses, focusing on the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. METHODS:A computer-based search of PubMed (1993-04/2012-09), China Academic Journal Network Publishing Database (2001-2008), and VIP (2001-2008) was performed by the first author to retrieve articles concerning the effects of metal crown, porcelain thickness, root canal preparation and fil ing on the tooth stress. The keywords were“porcelain-fused-to-metal, finite element method, stress analysis, root canal”in English and Chinese. Articles with repetitive contents or meta-analysis were ruled out. Then 40 articles were suitable for further analysis.RESULTS AND CONCLUSION:Finite element method has important significance to establish high-fidelity and high-accuracy models in oral medicine, thereby providing effective biomechanical information for the root canal treatment and post-treatment repair. Scholars continue to explore the stress distribution of dental prostheses during chewing. This review summarizes the stress changes of post and core crowns, supporting reference for further research. Three-dimensional finite element method can be used to build nonlinear three-dimensional finite element models with anisotropic biomechanical characteristics, and can gradual yimprove the transition from static analysis to a dynamic analysis, truly achieving accurate simulation of oral biology and dental morphology as wel as chewing function of the teeth.