Impact of rectangular collimation on the quality and retake of intraoral radiographs

Intraoral radiograph machines have evolved over the past century, but their design, especially the collimator, has changed little. Although circular collimation is easier to use, it exposes the patient to more radiation. Rectangular collimation reduces this dose by 50% through 60% but increases the risk of experiencing positioning errors. The authors aimed to determine whether the radioprotection benefits outweigh the technical disadvantages.

This retrospective study included intraoral radiographs obtained by dental students with both standard circular collimation and rectangular collimation. Two independent blinded evaluators analyzed the radiographs to identify all types of errors and retakes.

The rates of cone cuts and cone cuts requiring retakes were 20.9% and 5.7%, respectively, with rectangular collimation. These rates were substantially higher than with circular collimation (1.8% and 0.7%, respectively). The differences in the proportion of retakes due to cone cuts between rectangular collimation (27.2%) and circular collimation (36.0%) were not statistically significant. Moreover, the overall retake rate was not significantly different between rectangular collimation (16.9%) and circular collimation (16.7%) (P = .922).

The number of retakes was not significantly higher with rectangular collimation, despite a significant increase in cone cuts. It should be recommended that clinicians with proper training use this type of collimation in conjunction with a positioning device due to the considerable reduction in radiation exposure.

Special attention must be paid to cone positioning and clinical training to fully benefit from the radioprotective advantages of rectangular collimation.