Microhardness and SEM after CO(2) laser irradiation or fluoride treatment in human and bovine enamel.

BACKGROUND: It remains uncertain as to whether or not CO(2) laser is able to hinder demineralization of enamel. The possibility to use bovine instead of human teeth on anticariogenic studies with laser has not yet been determined. PURPOSE: To compare the ability of CO(2) laser and fluoride to inhibit caries-like lesions in human enamel and to test whether a similar pattern of response would hold for bovine enamel. STUDY DESIGN: Ninety-six enamel slabs (2 × 2 × 4 mm) (48 from bovine and 48 from human teeth) were randomly distributed according to surface treatment (n = 12): CO(2) laser, 5% sodium fluoride varnish (FV), 1.23% acidulated phosphate fluoride (APF) gel, or no treatment (control). Specimens were subjected to a 14-day in vitro cariogenic challenge. Microhardness (SMH) was measured at 30 µm from the surface. For ultrastructural analysis, additional 20 slabs of each substrate (n = 5) received the same treatment described earlier and were analyzed by SEM. RESULTS: ANOVA and Tukey test ascertained that CO(2) laser promoted the least mineral loss (SMH = 252(a)). Treatment with FV resulted in the second highest values (207(b)), which was followed by APF (172(c)). Untreated specimens performed the worst (154(d)). SEM showed no qualitative difference between human and bovine teeth. APF and control groups exhibited surfaces covered by the smear layer. A granulate precipitate were verified on FV group and fusion of enamel crystals were observed on lased-specimens. CONCLUSIONS: CO(2) laser may control caries progression more efficiently than fluoride sources and bovine teeth may be a suitable substitute for human teeth in studies of this nature.