Image homogeneity and recording reproducibility with 2 techniques for serial intra-oral radiography

The present study compared recording reproducibility and image homogeneity after applying two techniques for recording of serial intra-oral radiographs: 1) a technique previously described in 1990 based on mechanical fixation between the patient, the film holder, and the x-ray tube; and 2) a newly developed technique which operates with an optical alignment provided by a light beam. Twenty adults participated in the study. Two intra-oral radiographs were taken with a 30-minute time interval of the mandibular premolar/molar and the incisor region in each individual with either of the methods. All radiographs were scanned and digitized. Subtractions were performed between the two radiographs taken of the same individual and region with the same method. The standard deviation (SD) of the histogram defining the distribution of the grey shades in the subtraction image was used as the statistical test parameter. Subtractions were performed with an automated method and using a reference point-based program in order to test recording reproducibility and image homogeneity, respectively. Paired t-tests revealed that the average SDs obtained by the mechanical fixation method and the optical method were not statistically significantly different neither when applying the automated nor the reference point-based subtraction method (P > 0.05). The SDs increased significantly when the automated method was used compared to the reference point-based method (P = 0.001). In conclusion, the optical method and the mechanical method provided images of similar recording reproducibility and homogeneity.