Reliability of the magnification method for localisation of ectopic upper canines.

OBJECTIVE

To evaluate the reliability of the magnification method for localisation of palatally placed canines.

METHODS

Panoramic radiographs were taken of subjects, aged 10 to 12 years, with unerupted upper permanent canines. Two periapical radiographs (horizontal parallax method) were then used to identify 36 sublects with one palatally placed canine. Differences in the sizes of crowns of the canines on the panoramic radiographs were used to identify which tooth was palatally placed. The observer was blinded to the side with the palatally placed canine. The parallax and magnification results were tabulated, and the sensitivity and specificity of the magnification method calculated.

RESULTS

The magnification method was found to have a sensitivity of 75 per cent; specificity of 100 per cent; positive predictive value of 100 per cent; negative predictive value of 80 per cent; and an accuracy of 87.5 per cent, in localising palatally placed canines.

CONCLUSION

The magnification method, which uses the side-to-side difference in the magnification of the crowns of ectopic canines on panoramic radiographs, is adequate for initial assessment of canine position. The magnification method did, however, accurately identify canines that were not palatally placed. Additional radiographs may be required to accurately localise an ectopic canine.