Relationship between restorations and the level of the periodontal attachment.

Two hundred and forty stained extracted teeth with a restoration on one proximal surface and with no restoration on the opposite surface were investigated for the position and quality of the restoration and the position of the periodontal attachment. Only 27% of restorations were of good quality, 60% had overhangs and 13% deficiencies. The mean difference in loss of periodontal attachment (LOA) between the two surfaces for all teeth was 0.36 mm when the distance from the cemento-enamel junction to the periodontal membrane on the unrestored surfaces was subtracted from that on the restored surfaces. If allowance is made for those restorations located apical to the cemento-enamel junction, the LOA difference was 0.18 mm.