Aim To understand the frequency of use and training of IOTN amongst dental registrants working in primary and secondary care. To ascertain which factors influence 'accuracy' of IOTN amongst dental registrants.Method Participants were asked to complete a short questionnaire at the same time as scoring the IOTN for 14 cases. The questionnaire was developed by the authors of this study to understand registrants' place of work, frequency of use of IOTN and training undertaken in IOTN. Multiple linear regression analysis was used to reveal which predictor factors best described a registrant's knowledge of IOTN.Results The mean kappa scores were the highest for participants working in secondary care (K = 0.68) when compared to those solely working in primary care. The SO and GDP groups were found to be the groups with the largest proportion of participants using IOTN on a daily basis. Only the participants that used the IOTN everyday achieved an acceptable mean DHC K >0.60. There is an increasing trend of mean DHC kappa scores evident with increasing frequency of use of IOTN. All participants had received training in the use of IOTN with the majority (n = 181/229) having their last episode of training within the last five years. The majority of the training received in IOTN was classified as being verifiable (n = 154/229) with the remainder classifying their training as non-verifiable. Two predictor variables were found to have a significant influence on the DHC kappa scores, which included registrant group and place of work. Only one of the predictor variables had a statistically significant influence on the AC kappa scores, which was the type of CPD, with participants who had received non-verifiable CPD having a lower kappa scores.Conclusion Place of work, frequency of use of IOTN and registrant group were the main factors which were found to influence accuracy of use of IOTN. This study has highlighted a need for greater support in terms of resources, training and tools to help dental registrants use the IOTN more accurately to an acceptable level.