Reliability and validity of the Dental Indifference Scale in a population of 18-year-olds in Norway

Objectives: The aims of this study were to estimate the reliability and val idity of the Dental Indifference Scale (DIS) (Nuttall, 1996) in a populatio n of 18-yr-olds in Norway. Methods: The DIS-scale was mailed to a sample of 1119 18-yr olds in two Norwegian counties. Nearly 87% completed the questi onnaire and consented to the collection of data from their dental records. Ten percent of the sample, drawn at random, was asked to complete the quest ionnaire a second time, after a time delay of 15 weeks (response rate 83%). The reliability estimation of the sum-scores of DIS was based on Pearson's correlation between test-retest scores and internal consistency (Cronbach' s alpha). The frequency of missed appointments from age 12, recorded in the dental treatment records, was used as the validating criterion. The validi ty was analyzed by Pearson's correlation, and stepwise multiple regression. Results: The correlation coefficient (Pearson) for the test-retest compari son was 0.43. The correlation coefficient between the DIS-scores and the fr equencies of missed dental appointments was 0.24. The Cronbach's Alpha coef ficient for the eight DIS-questions was 0.35 (n=868). Only two of the eight DIS-questions entered the stepwise regression model and explained 15% of t he variance of the frequency of missed appointments. Conclusions: The Denta l Indifference Scale (DIS) was found to have a low reliability and validity in this study population, and it is recommended that it should not be used without further investigation. It may be necessary to design an alternativ e instrument if further work into the hypothesized trait of dental indiffer ence is to be undertaken.