Influence of alcopops and microorganisms on dental enamel in vitro

Objectives: The aim of the present in-vitro study was to examine the erosive effect, which different alcopops (Jim Beam Black&Cola, Bacardi Breezer Orange) or acidic microbial metabolites produced by Streptococcus mutans 10449 or Streptococcus oralis H1, alone or in combination, might cause on enamel of surgically removed wisdom teeth.

Methods: 24 dental crowns were cut into 5 slices and fixed with light curing composite in 12-well plates, exposing an average enamel area of 20mm². After disinfection, enamel samples were incubated at 37^oC in an anaerobic atmosphere with 2.5 ml of an acidic beverage (24h) and then with Schaedler broth inoculated with one of the streptococci (24h) or first with Schaedler broth freshly inoculated with one of the streptococci (24h) and then with one of the acidic beverages (24h) (n=6). Control samples were incubated in saline. Afterwards, the amounts of released calcium from enamel were determined using a colorimetric assay (Randox, Krefeld, Germany) and expressed in mg/dl/20mm². A descriptive statistical analysis of the data (non-parametrical test for related samples, Wilcoxon test, p<0.05) was performed. Enamel surfaces were visually analyzed in a SEM (DSM 962, Zeiss, Oberkochen, Germany). Results: Incubation of enamel slices with various acidic alcoholic beverages led to a time- and substrate-dependent calcium release. Incubation first with an alcopop and a subsequent colonization with streptococci led to an amount of released calcium (median) by the bacteria of 2.07-3.76mg/dl/20mm² versus 0.21-1.11mg/dl/20mm² when surfaces were exposed to bacteria first. The differences were in each case statistically significant (p=0.028). Scanning electron micrographs revealed different patterns of surface changes according to the order of exposure.

Conclusion: If erosive lesions caused by acidic beverages are already present on dental surfaces, microbial acid production can enhance the damage.