The increased occurrence of
dental erosion from self-induced
vomiting in
bulimia nervosa is not linearly associated with the frequency or the duration of
vomiting. Possible changes in the buffering and lubricating role of saliva in
bulimia nervosa and their relationship to erosion have not been previously investigated.
Chewing-gum-stimulated salivary flow rate, pH,
bicarbonate concentration and viscosity were compared between two groups of
vomiting bulimics and with 10 healthy controls. One bulimic group (n = 9) had pathological
tooth wear present according to the criteria of the
Tooth Wear Index and the other bulimic group (n = 10) did not. The influence of salivary pellicle on enamel
acid dissolution by
perchloric acid was also assessed by an enamel biopsy method.
Bicarbonate was measured in a Natelson microgasometer. Both the bulimic groups had mean initial 3-min flow rates and overall 9-min flow rates significantly lower (p < 0.01) than the healthy subjects. The mean pH values were not significantly different between the two bulimic groups or the control group. However, the mean
bicarbonate concentration in both bulimic groups was significantly less (p < 0.01) than in the control group. The mean salivary viscosity of 7.4 centipoise (cP), measured by a DV1 Brookfield viscometer, was significantly greater (p < 0.05) in the pathological
tooth-wear-present group than in the
tooth-wear-absent group (4.5 cP) and the control group (4.1 cP). Slightly more
calcium was released from the pellicle-free surface in both groups but this was not statistically significant, whilst the dissolved
calcium in enamel biopsies was significantly lower (p < 0.05) in the
tooth-wear-present group.