The Effect Of Cement Thickness And Elasticity Modulus On The Stress Distribution At Cement Layer Of The Implant Crown Using 2D Finite Element Approaches

The retention force of the implant crown were often affected by the abutment height、the converge angles and the bonding materials. When the abutment height were less than 3.5mm or the converge angles were large than 6°different bonding materials were used to strengthen the retention force of the impant crown.The reason cement layer were destroyed often caused by stress level in the cement layer,and could eventually led to the crown fell off.The retention force could be strengthened by decreasing the stress level at the cement layer. Using the finite element approaches to analysis the effect of different cement thickness and elasticity modulus on the stress distribution at cement layer provide us biomechanical basis for strengthen the retention force in clinic treatment.Part1 The effect of Zinc Polycarbonoxylate cement thickness on the stress distribution at cement layer of the implant crown using 2D finite element approachesMaterials and methods: Finite element models were established of the Zinc Polycarbonoxylate cemented implant crown. Four different thicknesses of cement layer(20μm、50μm 、80μm、150μm) were modeled. The mesh were refined at the adhesive layer and the adjacent parts. After mesh refinement,the adhesive layer grid reaches 1 u m, 2.5 u m, 4 um, 8μm, The mesh has been optimal after being calculated.100N Tensile Strength force were set to the models imitating the tensile test. The application point acting on the the top of tooth crown at the midpoint. Analysing the maximum tensile stress、 shear stress the distribution of stress in the adhesive layer in fifferent circumstance.Results: 1:The stress level at the cement layer were different with different cement thickness.2: The maximum tensile stress were 19.43mpa、7.41mpa、19.38mpa、23.83 mpa and the maximum shear stress were 14.62mpa、9.13mpa、9.26mpa、9.54 mpa when the cement thickness were at 20μm、50μm 、80μm、150μm.The stress level were at the lowest level when the cement were at 50μm.Conclusion:1The stress concentration area were different with the difference of the cement layer,The rentention force could be strengthened when the cement thickness was 50μm.Part2 The effect of elasticity modulus of three different adhesives materials on the stress distribution at cement layer using 2D finite element approachesMaterials and Methods:The implant crown models with 50 μm cement thickness were established. 100 N tensile force were set to the models refer to the part1.The stress level at the cement layer were analysised when three different adhesive materials were used.Results: Different bonding materials of the cement layer had different stress level in the cement layer. The maximum tensile stress、shear stress and the von mises stress were as follows: Zinc Polycarbonoxylate Cement :7.41 mpa,9.13 mpa,23.95 mpa,resin cement: 7.44 mpa,9.99 mpa,24.94 mpa, zinc phosphate: 11.67 mpa,11.81 mpa,26.41 mpa,Zinc phosphate had the largest stress level.Conclusions: The greater the elastic modulus of adhesive materials, the greater the stress level of the cement layer.Summary:The 2D finite models of the implant crown were established,the stress level at the cement layer were analysised.we got follow conclusions 1:The retention force of the implant crown could be stregthened when the cement thickness of the Zinc Polycarbonoxylate cement were at 50μm.2:The stress level at the cement layer had a close relationship with the elasticity modulus of the adhesive materials.