Promotion of enamel caries remineralization by an amelogenin-derived peptide in a rat model.

OBJECTIVE: An amelogenin-derived peptide has been shown to promote remineralization of demineralized enamel in an in vitro model of initial caries induced by pH cycling. The present study examines whether the peptide exerts similar effects within the complex oral environment in vivo. DESIGN: Specific pathogen-free Sprague-Dawley rats (n=36) were infected with Streptococcus mutans, given ad libitum access to Diet 2000 and drinking water supplemented with sucrose (10%, w/v), and then randomly divided into three groups treated with 25µM peptide solution, 1g/L NaF or deionized water. Molar teeth were swabbed twice daily with the respective solutions for 24days. Then animals were killed, their jaws were removed and caries lesions were analyzed using the quantitative light-induced fluorescence-digital (QLF-D) technique to measure changes in mineral content. To verify QLF-D results, caries were scored for lesion depth and size using the Keyes method, and analyzed using polarized light microscopy (PLM). RESULTS: Mineral gain was significantly higher in teeth treated with peptide or NaF than in teeth treated with water (p<0.05), based on the QLF-D results (ΔF and ΔQ). Incidence of smooth-surface and sulcal caries based on Keyes scores was similar in rats treated with peptide or NaF, and significantly lower in these groups than in rats treated with water (p<0.05). Lesions on teeth treated with peptide or NaF were shallower, based on PLM. No significant differences were observed between molar enamel caries treated with peptide or NaF. CONCLUSIONS: This amelogenin-derived peptide can promote remineralization in a rat caries model, indicating strong potential for clinical use.

[Profit and loss of nutrients in crop-fruit ecosystems].

The analysis on the balance of nutrient's profit and loss in crop-fruit ecosystems of three villges in middle-south Loess Plateau showed that fertilization was the main input of nutrients, of which, chemical fertilizer occupied a larger proportion, while organic manure was relatively insufficient. The quantity of N, P and K spent in interior circulation was far less than that exported from the ecosystem. The ratio of nutrient's output and input in three test villages was differed, but all at a low level.