EVALUATION OF A SIMPLE MODIFIED RADIOGRAPHIC ALIGNMENT SYSTEM FOR ROUTINE USE

RADIOGRAPHIC FRAMES USED FOR LONGITUDINAL STUDIES may be in part unrea dable for measuring crestal bone change. Sites may not be present on t he film, or the measurement reliability may be compromised because of dissimilar geometry. Several techniques used to address this problem a re expensive, time-consuming, and require great skill. For the present study a commercially-available alignment system was simply modified b y addition of a reference pin in the bite block, facilitating the repo sitioning of the film holder for a second exposure. This study determi ned the ability of the modified instrument to: 1) improve the geometri cal correspondence between serial radiographs; and 2) reduce the frequ ency of missed sites in the film. Two pairs of x-rays were taken for e ach of 40 subjects, 1 pair with the standard alignment instrument of a n assigned site and 1 pair with the modified instrument of the contral ateral site. Measurements of alveolar bone height were performed using the ''side by side'' technique. The modified instrument yielded signi ficantly smaller measurement differences and a significantly better ge ometrical correpondence than the conventional system (P<0.05). Also, t he modified instrument yielded significantly greater (P<0.01) readable sites (86%) as compared to the conventional instrument (62%). The sim ply-modified instrument facilitates the correct interpretation of seri al radiographs.