An accessory for use in aiding an oral surgeon to determine the optimum position and angle for a dental implant to be installed in a bone includes a probe assembly having one or more pairs of probe members pivotally mounted to each other about a pivot axis at their centers. Each pair of probe members is configured and dimensioned such that one end of the pair on one side of the pivot axis serves as a probe end to straddle the bone with their tips contacting the bone at opposed contact points thereon, and the opposite end of the pair on the opposite side of the pivot axis serves as a guide end in which the tips of the probe members are automatically located to indicate the thickness of the bone at the pair of opposed contact points. Also described are a kit including a plurality of such accessories, a tool for manually applying such accessories, and a method of using such accessories for use in determining the optimum position and angle for a dental implant.