In-vitro investigation on the protective effect of glycomacropeptide against acid erosion of tooth enamel

Tooth enamel is built of crystalline calcium phosphate fixed into a protein matrix. When acid comes into contact with tooth surface it encourages demineralisation and erosion of tooth enamel. Eroded tooth with small cavities becomes vulnerable to the attack of microflora present in dental plaque on tooth surfaces and increases the risk of tooth decay. It has been reported that dental erosion and caries among children and adults have an increasing trend. It is thought that changes in drinking habit and more interest in consumption of soft drinks could be a possible reason for this dental health problem.

To reduce the risk of dental erosion several studies were carried out and some research indicated that milk proteins and peptides have anti-erosive and anti-caries effect. In this category casein phosphopeptides (CPP) a tryptic hydrolysate of casein was widely studied to reduce dental problems. In addition, glycomacropeptide (GMP), a hydrophilic part of κ-casein released in whey, was of interest. In this study, attempts were made to reduce the mineral dissolution of enamel using GMP and GMP fractions during different acid contact times. To simulate the mineral dissolution of enamel hydorxyapatite (HA, calcium phosphate) was used. At different experiments HA was treated with GMP prior to exposure to 0.1M citrate buffer at different pH levels of 2.5-4.5. The level of dissolved calcium and phosphate into citrate buffer was measured by atomic absorption spectroscopy and Allen's colorimetric method, respectively. The erosive effect of soft drinks was investigated using orange juice and coca-cola containing GMP and its protection level was determined by measuring the amount of dissolved minerals in soft drinks compared to a control. To examine the protective effect of the GMP from acid attack on enamel surface, human enamel was studied by scanning electron microscopy. This study showed that GMP could reduce dental erosion and act better than CPP at low pH (3.0). This protective effect of GMP against mineral dissolution of enamel could be due to its attachment to the surface, its amino acid sequence and glycosylation level and/or to the overall net charge of the peptide.