Effects of the 3D bone-to-implant contact and bone stiffness on the initial stability of a dental implant: micro-CT and resonance frequency analyses.

This study investigated the effects of bone stiffness (elastic modulus) and three-dimensional (3D) bone-to-implant contact ratio (BIC%) on the primary stabilities of dental implants using micro-computed tomography (micro-CT) and resonance frequency analyses. Artificial sawbone models with five values of elastic modulus (137, 123, 47.5, 22, and 12.4 MPa) comprising two types of trabecular structure (solid-rigid and cellular-rigid) were investigated for initial implant stability quotient (ISQ), measured using the wireless Osstell resonance frequency analyzer. Bone specimens were attached to 2 mm fibre-filled epoxy sheets mimicking the cortical shell. ISQ was measured after placing a dental implant into the bone specimen. Each bone specimen with an implant was subjected to micro-CT scanning to calculate the 3D BIC% values. The similarity of the cellular type of artificial bone to the trabecular structure might make it more appropriate for obtaining accurate values of primary implant stability than solid-bone blocks. For the cellular-rigid bone models, the ISQ increased with the elastic modulus of cancellous bone. The regression correlation coefficient was 0.96 for correlations of the ISQ with the elasticity of cancellous bone and with the 3D BIC%. The initial implant stability was moderately positively correlated with the elasticity of cancellous bone and with the 3D BIC%.

Variations in bone density at dental implant sites in different regions of the jawbone.

The survival rate of dental implants is markedly influenced by the quality of the bone into which they are placed. The purpose of this study was to determine the trabecular bone density at potential dental implant sites in different regions of the Chinese jawbone using computed tomography (CT) images. One hundred and fifty-four potential implant sites (15 in the anterior mandible, 47 in the anterior maxilla, 55 in the posterior mandible, and 37 in the posterior maxilla) were selected from the jawbones of 62 humans. The data were subjected to statistical analysis to determine any correlation between bone density (in Hounsfield units, HU) and jawbone region using the Kruskal-Wallis test. The bone densities in the four regions decreased in the following order: anterior mandible (530 +/- 161 HU, mean +/- s.d.) approximately equal anterior maxilla (516 +/- 132 HU) > posterior mandible (359 +/- 150 HU) approximately equal posterior maxilla (332 +/- 136 HU). The CT data demonstrate that trabecular bone density varies markedly with potential implant site in the anterior and posterior regions of the maxilla and mandible. These findings may provide the clinician with guidelines for dental implant surgical procedures (i.e., to determine whether a one-stage or a two-stage protocol is required).

Effects of implant surface roughness and stiffness of grafted bone on an immediately loaded maxillary implant: a 3D numerical analysis.

This study investigated the effects of the stiffness of a maxillary sinus graft and the surface roughness of an immediately loaded implant using a non-linear three-dimensional finite element (FE) analysis (3D). Six FE models were created, including two stiffness values of grafted bone (345 and 3450 MPa of elastic modulus) and three conditions of implant-bone interfaces (Frictional coefficient of 0.3 for machined surface, 0.45 for rough implant surface and a bonded implant-bone interface for an osseointegrated implant). Computer tomographic images of a human skull were used to construct a posterior maxillary model. All implants were designed via the computer aided design software with a spiral threaded configuration. Three loading scenarios were investigated for each of the six models; axial loading and lateral loadings at 30 degrees and 60 degrees . The results showed that a 60 degrees lateral loading has scored the highest level of bone stresses among the three loading conditions. Immediately loaded implants with 0.3 frictional coefficient have suffered the highest bone stresses which were higher than those with bonded interface by about 57%. Increasing the frictional coeffecient to 0.45, however, did not show any benefits in reducing the peak bone stress. Raising the stiffness of grafted bone diminished the bone stress by about 10% in both the immediately loaded and the osseointegrated implants. It was also noted that increasing graft stiffness and implant surface roughness reduced the sliding at the implant-bone interface which may improve the implant stability and long-term survival.