Is there any difference between the British and Japanese de?nitions of the mandibular cortical index (MCI) on panoramic radiographs? A pilot study

Objectives To assess the reproducibility of the mandibular cortical index (MCI) on panoramic radiographs among British and Japanese observers, and to investigate the difference between the British and Japanese observers in the definition of MCI.Methods Three observers, a Japanese oral radiologist, a British oral radiologist, and a British prosthodontist, classified the inferior cortex of the mandible on a set of 100 duplicated films of randomly selected panoramic radiographs twice, 2 weeks apart, using the MCI. The kappa index for intra- and interobserver agreement was calculated for the three observers.Results The kappa index for intraobserver agreement was moderate (0.56) to perfect (0.86) for the three observers. Interobserver agreement between the Japanese and the British oral radiologists was moderate at the first reading (kappa, 0.59) and substantial at the second (0.61). Interobserver agreement between the prosthodontist on the one hand and each of the oral radiologists on the other was fair (0.35, 0.38) at the first reading, but moderate (0.43, 0.60) at the second reading. The prosthodontist tended to overestimate the MCI compared with either of the oral radiologists.Conclusion Our results suggest that the definition of MCI used by Japanese observers is basically similar to that used by British observers, although some improvements in the definition of MCI would be necessary for clinical dental practice.