Considering that Galla chinensis extract (GCE) solution has a low pH, which might dissolve dental enamel, we
investigated the effects of elevation of pH on GCE stability, and on its anti-caries properties.
of GCE solutions, either in H2O (pH less than 4.0) or when buffered at pH 5.5, 7.0 and 10.0, was assessed from UV-VIS spectra.
Inhibition of enamel demineralization was determined in a pH-cycling set up, comprising treatments with either GCE solutions
or negative control buffers and acid and neutral buffer immersions. Demineralization was assessed by calcium in the acetate
buffers. To determine antimicrobial properties, polymicrobial biofilms were formed after saliva inoculation on glass surfaces
which were treated after 48 h. Treatment output parameters were lactic acid formation and viability, the latter by colony
forming unit (CFU) counts.
At pH 7.0 and higher GCE solutions changed colour and absorption spectra in
UV-VIS, indicative of chemical changes. Regarding enamel demineralization, significant inhibitions (P < 0.05) were found
for all GCE treatments when compared with corresponding controls. In polymicrobial biofilms, GCE reduced the acid production,
compared with the negative controls (P < 0.05). However, this difference was only significant at the lower pH values.
solutions were unstable under neutral and alkaline conditions. pH did not significantly influence the inhibiting effect of
GCE on enamel demineralization. However, GCE was not effective on polymicrobial biofilms at alkaline pH (8.5). To avoid enamel
damage due to acidic treatment, GCE solutions should be used at about pH 5.5.