The Use of Snyder's Caries Activity Test in Oral Hygiene Effectiveness Monitoring

Dental caries is a rather slowly progressing disease. At least a year is required to evaluate a preventive measure by means of a reduction in the caries incidence. The Snyder's caries activity test, which is based on the acid production by oral bacteria, seemed an attractive short-term assessment tool for hygiene effectiveness. Six subjects used three different hygiene methods and their "caries activity" was measured before and after the hygiene procedures. The results were essentially negative with regard to any hygiene method significantly reducing the caries activity. In all cases, however, an extreme degree of reproducibility was noted in the individual's caries activity. It is concluded that the test is a useful tool for characterizing an individual's caries activity, but the usually employed hygiene methods are not reflected in a changed activity. THE USE OF SNYDER'S CARIES ACTIVITY TEST IN ORAL HYGIENE EFFECTIVENESS MONITORING INTRODUCTION Dental caries is a chronic, slowly progressing disease. This fact, coupled with the apparently multiple causes, has made the study and the control of this disease very difficult. This difficulty is obvious when it is considered that it takes approximately one year for the average young Navy man to develop two discernible new carious lesions. In this period of time it is recognized that many variables could have played a part in the disease and could only be discovered by a most painstakingly precise longitudinal analysis. For this reason, various caries activity tests have been devised with which caries activity may be assessed on a more immediate and short term basis rather than on the basis of having to wait for an enumeration of actual lesions. The attractiveness of such tests is readily apparent in that they could allow for the immediate assessment of preventive measures. Among the tests devised, the Snyder's caries activity test is probably one of the best known. In epidemiological studies it has been shown to be well correlated with other bacteriological counts and with actual carious lesion enumerations.' The test employs selective bacteriological medium for acidogenic microorganisms. A sample of saliva is inoculated into tubes of media and color changes of bromcresol green in the media are read after 24, 48 and 72 hours. The results are read qualitatively as caries activity, either none, slight, moderate or marked. The difficulty of relating oral bacterial tests to individual caries activity assessments has been previously recognized; however, they have been used to demonstrate the effect of caries elimination on the oral flora'* and recently demonstrated the effectiveness of an electric toothbrush in reducing caries activity as measured by the Snyder's test. The idea of using this caries activity test as a tool for assessing the effectiveness of hygiene methods was very attractive. Some preliminary studies using the standard Snyder's test at this laboratory, however, were inconclusive. It was therefore deemed appropriate to attempt some modification of the standard Snyder's test in order to see if it could be used as a monitoring tool for oral hygiene effectiveness. MATERIALS AND METHODS Some preliminary studies at this laboratory had given the impression that changes in the Snyder's caries activity test were too gross to be of any value in showing the effects of hygiene measures. For this reason a pilot study was first undertaken to determine the best quantity of whole saliva to use for the actual effectiveness study. Two subjects known to show positive caries activity with the Snyder's test were used. Salivary samples were collected from each subject in the following manner: The mouth was first rinsed with water; the subject chewed paraffin for 25 chewing strokes (all chewing being done on the same side), and then he was requested to spit, repeat the process and spit again. The first two samples of saliva having thus been discarded, the third sample was then collected in a sterile vial. The paraffin was then removed, the mouth rinsed again, and the entire collection procedure was repeated until four samples had been collected. Prepared Snyder's tubes containing 10 ml of Snyder test agar were inoculated. The saliva was inoculated in the following quantities: 0.2 ml, 0.1 ml, 0.07 ml, 0.04 ml, and 0.02 ml. In the case of subject B, the 0.2 sample was not used in view of his known strongly positive reaction. The medium was melted by placing the tubes in boiling water until melted throughout. The tubes were allowed to cool to 45°C and the saliva sample was added and mixed with the medium. The tubes were allowed to solidify at room temperature, and were then incubated at 37 °C for 72 hours. The saliva samples were collected before the hygienic procedure, after brushing, after using the Water Pik and after brushing and using the Water Pik. This entire program was repeated on three days for each of the two subjects. The results are summarized in Tables I and II. The reduction in Snyder's reaction with the hygienic measures used was significant in both subjects and was particularly dramatic in subject A (Table I). Table I Initial Overall Snyder's Test Activity With Hygiene Procedures Subject A Carles Activity Initial Toothbrush! ng Water Plk Toothbrushl ng and Water PIk 0 0 0 2 21 S! ight 0 h 22 18 Moderate 60 56 36 2 Marked 0 0 0 0 The data from this pilot study were used in planning a more detailed study using six subjects and a slightly different, but more normal hygiene program. Table II Initial Overall Snyder's Test With Hygiene Procedures