Objective: The aim of this study was to investigate the effect of a formal calibration process on the reproducibility of occlusal caries detection using the ICDAS-II by a group of experienced dentists and a group of undergraduate students who had initially learned the ICDAS-II system via a commercially available computer program. Method: Six undergraduate dental students and three experienced dentists were trained in the use of ICDAS-II using a commercially available computer program. The students and dentists then assessed the occlusal surfaces of 120 permanent molars twice, with a 2-week interval between the first and second assessments, using the ICDAS-II. Later both groups participated in a formal calibration process after which they repeated the previous assessment protocol for the same sample of teeth.

Results: Intra-examiner Cohen's kappa values for occlusal caries scores after learning the ICDAS-II via the computer program ranged from 0.56-0.66 for students and 0.63-0.78 for dentists. After formal calibration, intra-examiner kappa values ranged from 0.68-0.78 for students and 0.72-0.77 for dentists. Calibration improved each student's intra-examiner reproducibility, and one of the three dentists' intra-examiner reproducibility. Five of the six students were able to achieve comparable intra-examiner reproducibility to the dentists after calibration (K≥0.72). Inter-examiner Cohen's kappa values after learning the ICDAS-II via computer program ranged from 0.37-0.62 for students and 0.47-0.58 for dentists. After formal calibration, inter-examiner kappa values ranged from 0.43-0.75 for students and 0.51-0.61 for dentists.

Conclusion: A formal calibration session on detection of occlusal caries using ICDAS-II had a greater effect on the intra- and inter-examiner reproducibility for this group of students than for this group of dentists.