Inter-examiner Reliability of Resting and Stimulated Salivary Tests

Knowledge of patients' salivary flow rate, pH, and buffering capacity may aid in the assessment of caries risk. However, little is known about the inter-examiner reliability of tests measuring these salivary characteristics.

Objective: To evaluate inter-examiner test reliability for four salivary characteristics (resting pH, stimulated saliva flow rate, pH, and buffering capacity) among six examiners using simple and easy-to-use salivary tests prior to their implementation in a practice-based cohort study.

Methods: Resting and stimulated saliva samples were collected from 40 dental students who had abstained for one hour from smoking, eating, drinking (except water), toothbrushing or using mouthwash. An incomplete-block design was used to assign samples to six trained examiners (3 examiners/sample and 20 samples/examiner). For each test a reliability index was computed [Intraclass correlation coefficient (ICC)].

Results: The assessment of stimulated salivary flow rate demonstrated excellent reliability (ICC=0.95). The resting salivary pH showed adequate reliability (0.71), while the stimulated salivary pH had a very poor ICC (0.09). The buffering capacity test strip had 3 test pads with different acid challenges. The overall stimulated salivary buffering capacity test had poor reliability (ICC=0.37), with very poor reliability of the first and second challenges (ICC= -0.07 and 0.04) and adequate reliability of the third challenge (ICC=0.48).

Conclusions: Two salivary tests had an acceptable performance, while in the other two the small variance in stimulated salivary pH and buffering capacity in dental students may have artificially made the reliability appear low. The low reliability of buffering capacity may additionally have been due to ambiguity in interpretation of test pad colors. Prior to the implementation of a practice-based cohort study on caries risk assessment, further reliability studies with a wider variety of subjects and more explicit directions for recording test pad colors are needed.

Submitted on behalf of Northwest PRECEDENT. NIDCR DE016750 and DE016752