Effects of Elasticity and Structure of Trabecular Bone on the Primary Stability of Dental Implants
This study evaluated the effects of elastic modulus and cellular characteristics of trabecular bone on the primary stabilities of dental implants. Artificial jawbone models with six values of elastic modulus (137, 123, 47.5, 22, 12.4, and 6.5 MPa) comprising three kinds of trabecular structure (solid rigid, and cellular rigid with closed-cell and open-cell characteristics) were investigated in terms of the peak insertion torque value (ITV), implant stability quotient (ISQ), and Periotest value (PTV) as measured using a torque meter, OsstellTM resonance frequency analyzer, and PeriotestTM electronic device, respectively. All specimens adhered to 2-mm-thick short-fiber-filled epoxy sheets to mimic the cortical shell, and screw-type implants were placed in the models for measuring the implant stability. In general, the ITV, PTV, and ISQ increased with the elastic modulus of cellular trabecular bone. The differences in the primary stabilities of the implants between closed-cell and open-cell bone specimens (12.4 versus 6.5 MPa) were 52% for ITV, 2-fold for PTV, and 8% for ISQ. The regression correlation coefficient (R2) values between the elasticity of trabecular bone with a cellular (closed-cell) structure and ITV, PTV, and ISQ were 0.73 (with linear regression model), 0.93 (with linear regression model), and 0.89 (with logarithmic regression model), respectively. These linear and logarithmic models demonstrate the strong correlations of the elastic modulus of trabecular bone with the obtained ITV, PTV, and ISQ values. Trabecular bone with an osteoporotic structure decreases the primary implant stability. The use of cellular artificial jawbones as experimental models revealed that the elastic modulus and osteoporotic trabecular bone both influence the ITV, PTV, and ISQ primary implant stability parameters. Due to a similarity of trabecular structure, cellular characteristic of artificial bone might be more appropriate for obtaining accurate values of the primary implant stability than solid-bone blocks.