Millennial drinks: acidity, fluoride content, and enamel softening.

This in vitro study aimed to evaluate the acidity and fluoride content of beverages commonly consumed by millennials and the enamel-softening effect of these drinks on tooth enamel. The study included 13 beverages in 4 categories: energy (sports) drink, flavored sparkling water, kombucha, and other (an unsweetened iced tea, a vegetable-fruit juice blend, and a soft drink). The acidity was measured with a pH/ion meter, and the fluoride concentration was measured with a combined fluoride electrode coupled to the meter (n = 10 measurements per beverage). The Vickers hardness number of extracted molars was measured before and after a 30-minute immersion in 4 representative beverages via 2 immersion protocols (n = 10 per beverage per protocol): (1) immersion in the beverage only and (2) immersion alternating between the beverage and artificial saliva every other minute. The pH and fluoride concentrations of the beverages ranged from 2.652 to 4.242 and from 0.0033 to 0.6045 ppm, respectively. One-way analysis of variance (ANOVA) revealed that all differences between beverages in pH values were statistically significant, as were the majority of differences in fluoride concentrations (P < 0.001). The beverages and the 2 immersion methods significantly affected enamel softening (2-way ANOVA, P = 0.0001 to 0.033). The representative energy drink (pH 2.990; 0.0102 ppm fluoride) caused the greatest enamel softening followed by the representative kombucha (pH 2.820; 0.2036 ppm fluoride). The representative flavored sparkling water (pH 4.066; 0.0098 ppm fluoride) caused significantly less enamel softening than the energy drink and kombucha. A root beer (pH 4.185; 0.6045 ppm fluoride) had the least enamel softening effect. All tested beverages were acidic and had a pH below 4.5; only some contained fluoride. Flavored sparkling water, likely due to its higher pH, caused less enamel softening than the tested energy drink and kombucha. The fluoride content of kombucha and root beer lower their enamel-softening effects. It is imperative that consumers be aware of the erosive potential of beverages they consume.

Simple optical method for measuring free shrinkage.

OBJECTIVES: A simple optical method for measuring polymerization shrinkage of dental composites is compared with an established dilatometer. METHODS: Five restorative composites were used to test the methods: Filtek Supreme Ultra (3M ESPE), Filtek LS (3M ESPE), Premise (Kerr), Gradia Direct (GC), and GC Kalore (GC). Uncured composites were attached to sandblasted silane-treated glass slides. The slides were placed sample side inside a mercury-filled dilatometer (ADAF). The mercury levels were recorded as the materials were light-cured through the glass-slides (40s). Mercury levels, which correlated with volumetric shrinkage, were recorded for 60min (N=6). For the optical method, uncured composite was placed on a smooth silicone platform. A pre-polymerization image was captured under a stereomicroscope, and the specimen was light-cured (40s). Post-polymerization images were captured at 2, 10, 60, and 90min (N=10). Composite outlines were traced to obtain projected surface areas (ImageJ) and volumetric shrinkage was calculated. Results were analyzed using two-way ANOVA (α=0.05) and Pearson Correlation tests. Shrinkage deformation for both methods was modeled using finite element analysis. RESULTS: Volumetric shrinkage at 60min ranged between 1.24% and 2.24% for dilatometer and 1.35-2.68% for optical methods. Optical method shrinkage was consistently higher than the dilatometer (P=.0001), but the ranking of the composites was the same (Pearson Correlation Coefficient 0.9997). Finite element analysis showed that lower shrinkage values of the dilatometer method could be attributed to bonding of its samples. SIGNIFICANCE: The optical method using a general-purpose stereomicroscope and public-domain software is a simple and accurate alternative to measure free shrinkage.