Bone support as per cent of tooth length. A methodological study.

A technique is presented for calculating the amount of bone support as a percentage of the total tooth length measured on intra oral x-ray pictures. An evaluation was made of differences in total tooth length of 1128 teeth recorded in 1979 and in 1989. The differences found in the ten year period were minimal (0.3%). Between 1979 and 1989 0.7% or 2 mm of the bone support was lost. The accuracy obtainable by the use of measurements from x-ray pictures taken by trained personnel was found to be satisfactory. This indicate that the method could be of value for comparison of changes in mesial and distal bone support over a period of time. The advantages of using bone support measurements instead of attachment level measurements are several: ease of reevaluation of initial values, the patient does not have to be present the whole time, and properly trained dental assistants can make the measurements.