An in vitro Study of the Adherence of Oral Bacterial Species to Human Tooth Enamel With and Without Commercial Mouthwash

by: Peter Frye

In this study, the adherence capabilities of S. salivarius and N. sicca to human tooth enamel were examined. It was proposed that S. salivarius and N. sicca may have differing adherence capabilities, resulting in a differing number of bacteria adhering to the enamel surface. This study also examined the adherence of these bacterial species in the presence of the cetylpyridinium chloride-containing mouthwash Cepacol^®. It was proposed that in the presence of Cepacol^®, the adherence of both bacterial species would be significantly reduced.

Relatively caries-free extracted molars and premolars were obtained from Rochester-area dental offices. Thirty were washed in dH₂0, the roots were removed and the teeth were halved and sectioned into 1.0mm thick sections. 50.0ml of saliva was collected by expectoration, diluted with and equal amount of SIB, and clarified by centrifugation for 25 minutes at 15,000g. The thirty tooth sections were divided into three groups of ten: Control, N. sicca and S. salivarius. These groups were treated with saliva and incubated at 37° C for 10 minutes. The groups were then divided in half into groups of five, so that one half would be treated with Cepacol^®, and the other would not. N. sicca and S. salivarius suspensions were added to the designated groups in 24-plate well, and the controls had SIB added in place of the suspensions. To the groups designated for Cepacol^®, 0.5 ml was added to each well. The tooth sections were incubated at 37° C for 60 minutes. The suspensions were removed and replaced with SIB, and shaken at 150RPM. About 0.3 ml of the SIB solution was plated using the spread plate technique on TSA blood agar plates and the plates were incubated at 37° C for 12 hours. The CFU’s were counted following incubation. It was found that the N.sicca groups had significantly higher average CFU counts than S. salivarius both before (Mann-Whitney U= 23.0; df=1; P=0.026) and after (Mann-Whitney U= 25.0; df=1; P=0.008) Cepacol^® treatment. It was found that the groups treated with Cepacol^® had significantly lower average CFU counts than the groups not treated N. sicca:(Mann-Whitney U= 0.0; df= 1; P=0.009), S.salivarius : (Mann-Whitney U=0.0; df= 1; P= 0.007). The results found supported the proposals of the study.

Research Advisor: Beverly J. Brown, Ph.D., Nazareth College