Influence of the surgical technique and surface roughness on the primary stability of an implant in artificial bone with a density equivalent to maxillary bone: a laboratory study

Objective: The aim of this biomechanical study was to assess the effect of surgical technique and surface roughness on primary implant stability in low-density bone.
Material and methods: Eighty screw-shaped (Biocomp^®) implants with machined or etched surface topography were inserted into a low-density bone equivalent. Solid rigid polyurethane blocks (Sawbones^®) with two different bone densities (group A=0.32 g/cm³; group B=0.48 g/cm³) were used that are very similar to the density of the maxilla. The implant sites were prepared either by a press-fit or by an undersized technique. Peak insertion and removal torques were measured using a Digital^® torque gauge instrument.
Results: Independent of the surgical technique used, both implant types showed an increased mean insertion and removal torque value with increasing bone density. Insertion and removal torque values were 54.3±5.3 and 43.5±6.5 N cm for group A and 89.3±7.6 and 55±9.1 for group B, respectively. For group A and B, both implant types showed statistically higher insertion and removal torque mean values for the undersized compared with the press-fit technique ( P <0.01). In addition, etched implants showed statistically higher insertion and removal torque mean values compared with machined implants ( P <0.01).
Conclusion: The placement of etched implants in synthetic bone models using an undersized preparation technique resulted in enhanced primary implant stability; further, a correlation was found between primary stability and bone density of the synthetic bone, implying that in case of an implant site with low bone density, by changing the surgical technique and choosing an implant with an optimal surface roughness, the primary stability can be enhanced significantly.