Bone remodeling to maintain osseointegration between the bone and implant is absolutely essential to ensure favorable results and long-term stability in implant treatment [1, 2]. Bone remodeling requires that various stresses generated around the bone caused by the occlusal load applied to the implant be within an appropriate range. The concentration of stress at the bone-implant interface, caused by overloading, has been reported to result in bone resorption [3–5]. The stress generated in the implant will vary depending on the placement and the nature of the loading of the implants. Gunne et al. [6] stated that the allocation of the occlusal load was affected by the placement of the implant and the geometric form of the prosthetic device. When implants are being embedded, in contrast to the placement of three implants in a straight line, the term “offset placement” is used for a technique in which the central implant is shifted to the side. Rangert et al. [7] reported that in a patient missing three molars, straight placement of the three implants reduced the load to 67 % of that present when two implants were embedded to make a bridge configuration, while offset placement reduced the load to 33 %. However, they did not discuss the specific method they used to calculate the distribution of the load.

The usefulness of offset placement has been studied by geometric analysis, photoelasticity testing, strain gauging, finite element analysis (FEA), and several other techniques [8–19]. However, each type of analysis has its own disadvantages [19], and few studies have been carried out under ideal conditions. Therefore, it is necessary to evaluate the usefulness of offset placement objectively, by using multiple analyses, so as to eliminate the disadvantages of the individual analyses.

Hence, the purpose of the present study was to clarify the biomechanical effects, such as reduction in strain and displacement of implant, of offset placement on the peri-implant bone in edentulous posterior mandibles, by comparative investigation using FEA and model experimentation with strain gauges.