Effect of Poly-γ-glutamic Acid on Kinetics of Enamel Demineralization in vitro at pH 4.0, 4.5 and 5.0

The aim was to use ion selective electrodes and microhardness studies to measure the effects of poly gamma glutamic acid (PGGA) on the demineralization kinetics of dental enamel subjected to simulated cariogenic continuous challenges at pH values of 4.0, 4.5, and 5.0. A range of concentrations of microbially produced PGGA (1% and 2%) and NaF (0.01%, 0.1%, and 0.5%) was prepared. Sodium fluoride (NaF) was used as positive control and phosphate buffer saline (PBS) solution as negative control. Buffered acetic acid solutions (0.1 M) at pH 4.0, 4.5, and 5.0 were used as demineralizing solutions. Fifty-four orthodontically extracted teeth (each varnished leaving a window of 2 × 2 mm) were pre-treated for 24 h with either the respective concentrations of NaF, or PGGA, and then immersed in demineralizing solutions. The calcium ions released from the PGGA and the NaF pretreated enamel in the demineralizing solutions at different pHs were continuously measured using Ca²⁺ Ion Selective Electrodes (Ca²⁺ ISEs). Subsequently, the teeth were subjected to cross-sectional microhardness (CSMH) to determine the mineral concentration as a function of depth. Ca²⁺ ISE data showed enamel pre-treated with the different concentrations PGGA inhibited demineralization at all pHs, as was seen for the positive controls. Further, microhardness data on the same specimens showed that PGGA and the positive controls had not only protected the surface but also within the body of the lesions. PGGA, similarly to NaF, reduces enamel demineralization under artificial lesion formation conditions, not just at the surface but also within the body of the lesion.