Evaluation of three indices for biofilm accumulation on complete dentures.

Objectives: The objective of this study was to evaluate the accuracy and reproducibility of three complete denture biofilm indices (Prosthesis Hygiene Index; Jeganathan et al. Index; Budtz-Jørgensen Index) by means of a computerised comparison method.

Background: Clinical studies into denture hygiene have employed a large number of biofilm indices among their outcome variables. However, the knowledge about the validity of these indices is still scarce.

Materials And Methods: Sixty-two complete denture wearers were selected. The internal surfaces of the upper complete dentures were stained (5% erythrosine) and photographed. The slides were projected on paper, and the biofilm indices were applied over the photos by means of a scoring method. For the computerised method, the areas (total and biofilm-covered) were measured by dedicated software (Image Tool). In addition, to compare the results of the computerised method and Prosthetic Hygiene Index, a new scoring scale (including four and five graded) was introduced. For the Jeganathan et al. and Budtz-Jørgensen indices, the original scales were used. Values for each index were compared with the computerised method by the Friedman test. Their reproducibility was measured by means of weighed kappa. Significance for both tests was set at 0.05.

Results: The indices tested provided similar mean measures but they tended to overestimate biofilm coverage when compared with the computerised method (p < 0.001). Agreement between the Prosthesis Hygiene Index and the computerised method was not significant, regardless of the scale used. Jeghanathan et al. Index showed weak agreement, and consistent results were found for Budtz-Jorgensen Index (kappa = 0.19 and 0.39 respectively).

Conclusion: Assessment of accuracy for the biofilm indices showed instrument bias that was similar among the tested methods. Weak inter-instrument reproducibility was found for the indices, except for the Budtz-Jørgensen Index. This should be the method of choice for clinical studies when more sophisticated approaches are not possible.