The accuracy of the Schei ruler: a laboratory investigation

A study has been carried out to assess the accuracy of the Schei ruler for measuring the amount of alveolar bone loss from radiographs. A dried human mandible was used for the purpose of this study. A preliminary test was conducted to achieve a standard radiographic technique. Two sets of radiographs were taken of anterior and posterior segments after successive modification of the height of the alveolar bony crest. These heights were measured directly and also by means of the Schei ruler for each stage, using first the root length, and secondly, the total tooth length, as references for obtaining the percentage of remaining alveolar bone. There are two points which may be concluded from this investigation: 1. The ruler proved to be a sensitive tool for measuring the amount of alveolar bone loss as well as being efficient in this application because of its simplicity and ability to give direct readings of the percentage of the bone lost (or remaining). 2. The use of the total tooth length as a reference for the percentage bone loss, overcomes the difficulties of locating other reference points.