Summary of the IADR Cariology Research, Craniofacial Biology, and Mineralized Tissue Groups Symposium, Iguaçu Falls, Brazil, June 2012: Gene-environment Interactions and Epigenetics in Oral Diseases: Enamel Formation and its Clinical Impact on Tooth Defects, Caries, and Erosion

Characteristics of enamel may influence or modulate individual susceptibility to caries and erosion. These characteristics are defined during development, which is under strict genetic control, but can easily be modified in many ways by environmental factors. In the symposium, translational aspects of embryology, biochemistry, and genetics of amelogenesis were presented. The symposium provided unique insight into how basic sciences integrate with clinically relevant problems. The need for improved understanding of risks at the individual level, taking into consideration both environmental exposures and genetic background, was presented. The symposium was divided into four stepwise and interconnected topics as follows: 1) The Many Faces of Enamel Development; 2) Enamel Pathogenesis: Biochemistry Lessons; 3) Environmental Factors on Enamel Formation; and, 4) Genetic Variation in Enamel Formation Genes.

Remineralization of eroded enamel lesions by simulated saliva in vitro

Purpose:

The purpose of this study was to evaluate the effects of two simulated saliva (SS) remineralization solutions comprising different calcium-inorganic phosphate (Ca/P_i) ratios on eroded enamel.

Methods:

3 mm diameter enamel cores were extracted from bovine teeth, mounted in acrylic rods, ground and polished,and initially demineralized with either 0.3% (120 minutes) or 1.0% (30 minutes) citric acid solutions (pH 3.8). Both sets of initially eroded specimens were evaluated for surface microhardness (N=10) and treated with either 0.3 or 1.6 Ca/P_i ratio SS. Groups were first exposed to a seven-day remineralization period and then were cycled in a three-day regimen consisting daily of three rounds of two-hour plus overnight SS treatments and three 10-minute static immersions in demineralization solution. Specimens were assessed using surface microhardness and scanning electron microscopy.

Results:

Initial erosion from 0.3% citric acid led to elliptical-shaped pore openings several microns in length and in depth and contrasted significantly with respect to 1% citric acid. The greatest remineralization was observed from the 0.3 Ca/P_i SS, while the 1.6 Ca/P_i SS produced the least.

Conclusions:

This study demonstrated the nature of remineralization of eroded enamel depends on both initial erosive conditions and the Ca/P_i ratio of simulated saliva.

Erosive potential of different types of grape juices

The purpose of the present study was to evaluate the erosive potential of different types (concentrated and powdered) and commercial brands of industrialised grape juices. The pH of all five fruit drinks was measured at two time points: immediately after preparation and 24 hours later. Sixty specimens of bovine enamel were randomly allocated and immersed in different types of grape juice (n = 10) for 10 minutes four times a day for fifteen days. The enamel alteration was analysed using surface Knoop microhardness (KHN) and surface roughness (Ra) tests at baseline and on the 5(th), 10(th) and 15(th) days of the experiment. Two way ANOVA, Tukey's post hoc and Pearson's correlation tests were used for statistical analysis (α = 5%). The grape juices presented pH values ranging from 2.9 to 3.5. All of the tested juices promoted significant enamel mineral loss (p < 0.05) on the first evaluation (5(th) day of immersion) and produced a significant increase in the mean roughness from the 10(th) day on when compared to the control group (p < 0.05). By the 15(th) day, all of the beverages had produced surface roughnesses that were significantly higher than that of the control group. The results suggest that all grape juices, regardless of their commercial presentation, present erosive potential.