Bendable vs. angulated dental implants: consideration of elastic and plastic material properties based on experimental implant material data and FEA

Bendable and angulated single-piece implants are used alternatively to screwable abutments in two-piece dental implant designs. Though used frequently, data on the stress distribution within such implants are not available and the question whether the bending contributes to fracture resistance has not been addressed. We used the method of finite element to identify von Mises stresses and maximum stresses in bent and non-bent but angulated implants. Implants with one (e.g. applicable to screw designs) or two (applicable to basal implants) bending areas were the variables under investigation. For bends up to 13 degrees we discovered that if there is only one bend, the maximum stress is in the bent area. If two bends are made in two different bending areas, the maximum stresses are distributed between the two and, if either one of the bent areas is machined, there are no residual stresses within the implant body in this area. The maximum stresses are always located near the base-plates. The absolute value of the maximum stress is higher because no residual stresses are available to compensate stresses that stem from loading. Assuming that all other parameters are equal, bendable (basal) implants show a more even stress distribution along the vertical implant region than identically shaped implants with a machine-angulated area. Bendable basal implants therefore probably resist masticatory forces better than pre-angulated, machined implants, and unbent implants which provide a thin region in the vertical implant area.