In dental implantology axially symmetrical implant caps are increasingly used. In addition to bio-compatible material and an appropriate form of the implant a sufficient bearing arrangement for the implants is particularly decisive to guarantee the success of treatment. One of the main problems consists in the judgement of the bone alveolar ridge width because the covering mucosa may mask the real width. As a sure method ridge mapping is recommended for determining alveolar ridge width. In order to carry out ridge mapping a modified pair of bone compasses is introduced.