The effects of gum chewing, four oral hygiene procedures, and two saliva collection techniques, on the output of bacteria into human whole saliva

Abstract

Six healthy dentate individuals collected a 5-min sample of unstimulated whole saliva (UWS) and dilutions were plated out on blood agar and grown anaerobically for 48 h. The output of bacteria into saliva (counts/min) was calculated as the product of counts/ml and ml/min. The individuals repeated the collections at intervals of up to 7 h after (1) rinsing with water, (2) eating a meal plus tooth brushing, (3) a thorough dental prophylaxis, or (4) tongue brushing and scraping. They also collected saliva at intervals while chewing gum for 20 min, as did 10 individuals who chewed gum for 2 h. The original six individuals also collected UWS under “drooling” (no oral movements) and “spitting” conditions. Six edentulous individuals not wearing their dentures collected UWS before and after a water rinse. With the four oral hygiene procedures, bacterial outputs fell initially and then rose again, but a repeated-measures ANOVA revealed no significant differences in the effects of the four procedures. Gum chewing caused initial marked increases in the outputs of bacterial and epithelial cells, but these fell with time and reached a plateau after about 10 min at outputs above those in UWS. Samples collected by spitting contained up to 14 times more bacteria than those collected by drooling. Bacterial output by edentulous individuals did not differ from that in those with teeth. It is concluded that bacteria from the teeth and gingival crevices normally make only a small contribution to those in saliva, that various oral hygiene procedures have similar effects on bacterial output into saliva, and that saliva collection conditions should be standardized and specified.