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 validity of the Dental Indifference Scale (DIS) (Nuttall, 1996) in a population 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 questionnaire and consented to the collection of data from their dental records. Ten percent of the sample, drawn at random, was asked to complete the questionnaire 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 validity was analyzed by Pearson's correlation, and step-wise multiple regression. RESULTS: The correlation coefficient (Pearson) for the test-retest comparison was 0.43. The correlation coefficient between the DIS-scores and the frequencies of missed dental appointments was 0.24. The Cronbach's Alpha coefficient 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 the variance of the frequency of missed appointments. CONCLUSIONS: The Dental 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 alternative instrument if further work into the hypothesized trait of dental indifference is to be undertaken.