D.J. Epasinghe 1, C.K.Y. Yiu1, M.F. Burrow2 Synergistic effect of proanthocyanidin and CPP-ACFP on root caries remineralization D.J. Epasinghe 1, C.K.Y. Yiu1, M.F. Burrow2 1Paediatric Dentistry and Orthodontics, Faculty of Dentistry, The University of Hong Kong 2Oral Diagnosis and Polyclinic, Faculty of Dentistry, The University of Hong Kong 777 Results: One-way ANOVA indicated that testing solutions/pastes had a significant effect on lesion depth (P<0.05) and mineral loss (P<0.05) Lesion depth was significantly lower in TMP+PA and 1000ppm fluoride groups (P<0.05). Mineral loss was the lowest in TMP+PA group (P<0.05) (Figure 1). Higher mineral deposition was observed in the root caries lesion treated with PA combined with TMP. This indicated better penetration of PA into deeper parts of caries lesion when incorporated with TMP (Figure 2). Two-way ANOVA indicated that the factors “testing solution/pastes” and “lesion depth” had a significant effect on Knoop hardness (P<0.05), with significant interaction between the two factors (P<0.05). Artificial caries lesions treated with TMP+PA showed significantly higher microhardness values at 130μm and 150 μm from the surface (P<0.05) (Figure 3). Remineralizing bands with higher mineral density were observed in TMP+PA group (Figure 4). Discussion: PA has a strong collagen cross-linking effect as well as inhibitory effect on soluble- and collagen-bound proteases (Bedran-Russo et al., 2011). Furthermore, it also has a remineralizing effect in caries lesions by interacting with calcium ions (Xie et al., 2009) Incorporation of PA with TMP may allow slow release of calcium ions in deeper layers of caries lesions, thereby preventing superficial mineral deposition. Although the lesion depth of TMP +PA group was not significantly different from fluoride group, significantly less mineral loss was observed in the TMP +PA group, which was also confirmed by confocal laser scanning microscopy Microhardness was significantly increased in deeper layers of the caries lesion in the TMP+PA group, when compared to PA only or Fluoride only group. This could be attributed to increased mineral deposition by the synergistic effect of TMP and PA as well as cross-linking of collagen by PA via ionic and covalent bonding   Background: Root caries remains a major oral health problem among the elderly. Proanthocyanidin (PA) has recently been shown to have positive effects on remineralization of artificial root caries (Xie et al., 2009). It is advantageous to find methods to enhance the remineralization effect of PA. Objective: This study evaluated the synergistic effect of PA and casein phosphopeptide amorphous calcium fluoride phosphate (CPP-ACFP) on remineralization of artificial root caries. Methods: Root fragments with artificial caries (n=90) were randomly divided into six groups based on remineralization treatments: (i) 6.5% PA, (ii) CPP-ACP (Tooth Mousse, TM), (iii) CPP-ACFP (Tooth Mousse Plus, TMP), (iv) CPP-ACFP (Tooth Mousse Plus, TMP) + 6.5% PA, (v) 1000ppm fluoride and (vi) deionized water (control) Each specimen was immersed in the demineralizing solution for 14 h, testing solutions/pastes for 2 h and remineralizing solution for 8 h. The pH cycling was performed at 37oC for 8 days Specimens were evaluated using transverse microradiography (lesion depth and mineral loss), a microhardness tester (Knoop hardness) and confocal laser scanning microscopy (CLSM) Lesion depth and mineral loss were analyzed using one-way ANOVA; while microhardness was analyzed with two-way ANOVA and Tukey’s test Figure 4. Representative confocal laser scanning microscopy images of artificial caries lesion following pH cycling. A- Control, B- TM, C- TMP, D- TMP + 6.5% PA, E- 6.5% PA, F- 1000ppm Fluoride. Conclusion: The combined use of proanthocyanidin and casein phosphopeptide amorphous calcium fluoride phosphate has a synergistic effect on root caries remineralization by enhancing mineral gain and increasing hardness of the artificial root caries. Figure 1. Effect of treatments on mineral loss and lesion depth of the artificial root caries lesions. References Xie Q, Bedran-Russo A.K, Wu C.D. In vitro remineralization effects of grape seed extract on artificial root caries. J Dent, 2008. 36(11): p. 900-6.. Bedran-Russo A. K, Castellan C. S, Shinohara M. S, Hassan L, Antunes A. Characterization of biomodified dentin matrices for potential preventive and reparative therapies. Acta Biomater, 2011. 7(4): p. 1735-41. Figure 2. Tranverse microradiograph images of artificial root caries lesions after pH cycling. A- Control, B- TM, C- TMP, D- TMP + 6.5% PA, E- 6.5% PA, F- 1000ppm Fluoride. Figure 3. Cross sectional microhardness values of the artificial caries lesions after pH cycling.