Surface Microhardness of Enamel Exposed to Supplemented and Unsupplemented Artificial Saliva Formulations In Vitro

This in vitro study compared enamel surface microhardness responses to sodium fluoride (NaF), tricalcium phosphate (TCP), and calcium glycerophosphate (CaGP) in an olive leaf extract-containing artificial saliva carrier and to the unsupplemented carrier. A total of 131 human premolars were randomly allocated to NaF (n = 40), TCP (n = 40), CaGP (n = 40), or carrier (n = 11). After 96 h of demineralization, specimens underwent continuous immersion for 28 days. The primary outcome was surface microhardness recovery (ΔVHN), calculated as post-treatment minus post-demineralization Vickers hardness number (VHN). Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) was exploratory (n = 14). Surface hardness increased in all groups. Mean ΔVHN was 105.00 ± 53.00, 138.11 ± 50.40, 102.81 ± 48.46, and 116.98 ± 39.71 for NaF, TCP, CaGP, and carrier, respectively. The TCP formulation showed greater ΔVHN than the NaF and CaGP formulations (Bonferroni-adjusted p = 0.027 and 0.009), but no supplemented formulation showed significantly greater recovery than the carrier after multiplicity correction. Supplementary analysis likewise did not demonstrate a TCP-carrier difference (adjusted p = 0.117). No corrected SEM-EDX stage contrast was significant. These results describe surface mechanical responses of specific formulations at unequal doses under prolonged laboratory exposure. They do not establish incremental benefit over the calcium/phosphate-containing carrier or superior remineralizing efficacy of TCP; complete lesion repair cannot be inferred.