Unfortunately, the effects of double- or triple-threaded implants on primary stability are known for only a few procedures, such as finite element analysis. An excessive lead angle for these implants may jeopardize their ability to sustain axial load despite faster insertion. Further, when micromotion is compared among implants with different lead angles with the same thread pitch, single-threaded implants demonstrate minimal micromotion, whereas triple-threaded implants show maximum micromotion, with both vertical and horizontal loading. Thus, numerous clinicians believe that double-threaded implants can be inserted faster with greater primary stability compared with single-threaded implants. Thus, double- and triple-threaded implants are used for immediate loading of an implant, and the increase in surface area affords greater primary stability. To date, however, data to confirm these findings have been insufficient. We previously conducted a torque analysis to determine the effects of various thread designs on primary stability. However, we were unable to determine the effects of the double-threaded implants.

Further, we employed an artificial bone model to directly observe the implant/bone interface. This method allowed direct observation of the contact interface between an implant and artificial bone without cutting out the test piece. We were able to match the effect of the torque-time curve by grinding the interface of an implant and artificial bones with the aid of a digital microscope.

This model allows observation of immediate bone damage, characterized by debris and voids during implant placement. This in turn provides critical information about the relation between tissue damage and quantifiable factors associated with primary stability, such as torque and implant stability quotient values (ISQ). Here, we employed this model to measure torque and ISQ, together with direct microscopic observations, to evaluate the primary stabilities of single- and double-threaded implants.