Site specificity of citric acid retention after an oral rinse

Erosion of the buccal incisor enamel, most frequent in the upper jaw, has been associated with excessive oral exposure to citric acid-containing foodstuffs. The aim of the study was to determine the retention of citric acid at different sites in the mouth after a standardized exposure. Thirty-four normal subjects rinsed with 95.2 mmol/l (2%) citric acid, pH 2.1, for 5 s. At 1 min 55 s after the rinse a preweighed cotton pellet was used to collect saliva samples from upper labial incisor surfaces (UB), lower labial incisor surfaces (LB) and sublingually (SL). The citric acid concentration was determined enzymatically. The concentrations were (mean +/- SD): 32.12 +/- 19.50, 11.90 +/- 8.60 and 1.52 +/- 1.90 mmol/l in the saliva collected from the UB, LB and SL sites, respectively. Analysis of variance revealed that the citric acid concentration in the upper incisor site differed significantly from that of the lower incisor site (p < 0.001) and the sublingual site (p < 0.001), and that the lower incisor site differed significantly from the sublingual site (p < 0.001). The individuals differed significantly with respect to citric acid retention (p < 0.05). A significant correlation was found between UB and LB sites (r = 0.61, p < 0.05).