Continuing dental education in radiation protection: knowledge retention following a postgraduate course

Objective: To evaluate medium-term knowledge retention of dental personnel following attendance at a postgraduate course in radiation protection. Subjects and methods: Knowledge was measured using identical pre- and post-course validated single best-answer multiple-choice instruments, administered immediately before and after training and at follow-up at 6 or 12 months. These comprise 16 questions each with 5 choices. The range of possible scores was from 0 to 16, and scores were scaled to percentages. Participants were predominantly dental practitioners, but a minority consisted of dental care professionals (dental nurses, hygienists and therapists). Of 285 participants, 272 (95.4%) completed both pre- and post-course questionnaires. One hundred and seventeen (43%) of these also completed the follow-up test, but only 109 (40%) individuals could be linked to the original course. Results: Mean (standard deviation) pre-, post-course and follow-up-corrected percentage scores were 39.1 (16.1), 74.6 (16.9) and 58.9 (22.7), respectively. There was attrition in knowledge at follow-up: the average increase in adjusted score after training was 35.5 points, but only 56% of this was retained at follow-up. Paired t-tests confirmed that the mean score at follow-up was firmly intermediate between the pre- and post-course scores. Of the 109 participants, 7 (6%) achieved a satisfactory score pre- training, 82 (75%) immediately post- training and 41 (38%) at follow-up. There were gross differences between the levels of performance achieved for the eight subject areas tested. Conclusion: Immediate post- course assessments have indicated that current postgraduate courses in radiation protection are effective. However, a substantial amount of knowledge is lost by 6-12 months following course attendance. To achieve long-term knowledge retention, early or repeated reinforcement may be necessary.