Periodontal attachment loss assessed by linear and area measurements in vitro.

The aim of the present study was to investigate the relationship between linear and area measurements of periodontal attachment loss, and to determine the root surface area on different tooth-types. Extracted permanent teeth were collected in a national survey including a systematic random sample of 500 Norwegian dentists. The response rate was 70%. Altogether 329 teeth were received, 81 of them (excluding 3rd molars) were subjected to both linear and area measurements of attachment loss. Using a dissecting microscope (10 x), 4 to 8 duplicate linear measurements were recorded per tooth. The areas of both lost and remaining periodontal attachment were measured by a method based on controlled release of Cu and Co metal ions from coatings applied to the root surface. Linear loss of attachment for single-rooted teeth (n = 63) was mean = 44.0% and the area loss mean = 49.2%. The corresponding measurements for multi-rooted teeth (n = 18) were mean = 30.3% and mean = 35.1%, respectively. The correlation between linear and area loss was r = 0.78 for single-rooted and r = 0.75 for multi-rooted teeth (p < 0.01). The lower correlation in multi-rooted teeth is probably due to the more complex root anatomy. It is concluded that there is a strong correlation between linear loss of attachment and area of periodontal support lost for teeth with early to moderate loss of attachment, and that linear measurements tend to underestimate the remaining periodontal attachment.