[Digital subtraction technique in studying the bone quality alterations around dental implants: a comparison study between linear and logarithmic subtraction images]

The aim was to evaluate the efficiency of the digital logarithmic subtraction method in assessing the alteration of bone density around the dental implants; comparison with the digital linear subtraction method. Forty dental implants were set in the posterior mandibles of 40 patients. A standard reference periapical digital Image [A] was taken one-week post-surgical. Three images [B1, B2 and B3] were taken 3 months later. These images were treated separately by digital linear and logarithmic subtractions using Emago advanced/5,3 software; so, 120 linear subtraction and 120 logarithmic subtraction images were obtained. A region of interest [ROI] was determined distal to each implant cervical area and radiographic bone density was obtained. The mean value of the total digital subtraction evaluated by logarithmic subtraction was significantly more compared to what was evaluated by linear subtraction [21.70 +/- 9.36 and 17.24 +/- 8.98 respectively; P<0.000], counter to the mean values of the total change of the digital subtraction [0.58 +/- 0.53 and 1.89 +/- 1.38 respectively; P<0.000] and the percentage of the total change of the digital subtraction [3.41 +/- 6.64 and 13.08 +/- 10.96 respectively; P<0.000] which were less. The digital logarithmic subtraction is a precise method in evaluating the alteration of the bone density.