Comparison of two film holders for periapical radiography performed by dental students.

A clinical study was done at Howard University, College of Dentistry, to compare the difference in the incidence of radiographic technique faults between two similar intraoral film-holding, beam-aligning, devices in a series of 1,248 radiographs. The primary difference between a conventional Extension Cone Paralleling (XCP-I) film holder and a modified, all-metal, Extension Cone Paralleling (XCP-II) film holder is the incorporation of a collimated rectangular x-ray-beam-restricting plate. This latter film holder possessed an indicator rod attached to the bite block and a metal shield to reduce primary and back-scattered radiation behind the film. In the oral diagnosis clinic, 78 dentulous patients were randomly selected and randomly divided into two groups of 39 patients. One of the two film holders was used separately for the two groups of patients, and a full mouth series of 16 periapical radiographs were made for each patient. The difference in the occurrence of total errors between the two instruments was not statistically significant. However, the conventional instrument was associated with significantly more errors in improper film positioning, while the modified device had significantly more errors in cone cutting (p < 0.01).