Psychological stress as a determinant of protein levels and salivary-induced aggregation of Streptococcus gordonii in human whole saliva. 
Several pathologies of the oral cavity have been associated with stress, so we investigated salivary-induced aggregation during psychological stress.  In addition, salivary total protein, alpha-amylase, and secretory immunoglobulin A (s-IgA) were assessed.  In this longitudinal study, 28 dental students provided unstimulated whole saliva during 10 minutes before an academic examination and subsequently 2 weeks and 6 weeks later in a nonstress situation.  The effect of whole saliva on the aggregation of Streptococcus gordonii (HG 222) was determined spectrophotometrically.  The results shows a significant stress-mediated increase of salivary total protein concentration, alpha-amylase activity, amylase/protein ratio, alpha-amylase output, s-IgA concentration, and s-IgA output.  There was also a trend for increased total protein output, whereas salivary flow rate was unchanged.  The aggregation of S. gordonii in whole saliva collected before examination was 13.1%, whereas the aggregation in whole saliva collected during nonstress was 23.3%.  This reduction was statistically significant (p < .01).  Furthermore, the decrease in bacterial aggregation was related to the increase in state-anxiety (p < .05).  The reduction in aggregation of S. gordonii under stress was not correlated with changes in salivary flow rate, s-IgA concentration, total protein concentration, or alpha-amylase activity.  These results suggest that acute psychological stress exerts its influence on both salivary composition and salivary function.  Reduced bacterial aggregation may be a contributing factor in the often reported relationship between stress and impaired oral health.