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8DSS-Promoted Remineralization of Initial Enamel Caries In Vitro Y. Yang, X.P. Lv, W. Shi, J.Y. Li, D.X. Li, X.D. Zhou and L.L. Zhang J DENT RES published online 4 February 2014 DOI: 10.1177/0022034514522815 The online version of this article can be found at: http://jdr.sagepub.com/content/early/2014/02/04/0022034514522815

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XXX10.1177/0022034514522815

Research Reports Biomaterials & Bioengineering

8DSS-Promoted Remineralization of Initial Enamel Caries In Vitro

Y. Yang1, X.P. Lv1, W. Shi2, J.Y. Li1, D.X. Li1, X.D. Zhou1, and L.L. Zhang1* 1

State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, People’s Republic of China; and 2Dental Research Service Center, UCLA School of Dentistry, Los Angeles, California, USA; *corresponding author, [email protected] J Dent Res XX(X):1-5, 2014

Abstract

Introduction

Peptides containing 8 repeats of aspartate-serineserine (8DSS) have been shown to promote the nucleation of calcium phosphate from solution into human enamel. Here we tested the ability of 8DSS to promote the remineralization of demineralized enamel in an in vitro model of artificial early enamel caries. Initial caries lesions were created in bovine enamel blocks, which were then subjected to 12 d of pH cycling in the presence of 25 µM 8DSS, 1 g/L NaF (positive control) or buffer alone (negative control). Absorption of 8DSS was verified by X-ray photoelectron spectroscopy. Mineral loss, lesion depth, and mineral content at the surface layer and at different depths of the lesion body were analyzed before and after pH cycling by polarized light microscopy and transverse microradiography. Mineral loss after pH cycling was significantly lower in the 8DSS samples than in the buffer-only samples, and lesions in the 8DSS samples were significantly less deep. Samples treated with 8DSS showed significantly higher mineral content than buffer-only samples in the region extending from the surface layer (30 µm) to the average lesion depth (110 µm). No significant differences were found between the samples treated with 8DSS and those treated with NaF. These findings suggest that 8DSS has the potential to promote remineralization of demineralized enamel.

D

KEY WORDS: aspartate-serine-serine (8DSS), peptide, demineralization, transverse microradiography, dentin phosphoprotein, dental caries resistance. DOI: 10.1177/0022034514522815 Received August 30, 2013; Last revision January 13, 2014; Accepted January 13, 2014 © International & American Associations for Dental Research

ental caries is one of the most common diseases in the world. It results when the normal equilibrium between de- and remineralization of calcium and phosphate into and out of tooth enamel shifts substantially toward demineralization as a result of acid production when cariogenic bacteria metabolize fermentable carbohydrates (Ehrlich et al., 2009). Remineralization is a natural repair process that can prevent caries lesions from progressing into cavities. In the past 50 yr, investigators have examined a broad variety of agents to promote the remineralization of incipient demineralized lesions (Panich and Poolthong, 2009; Zhang et al., 2009). These agents include amorphous calcium phosphates, xylitol, galla chinensis, casein phosphopeptide–amorphous calcium phosphate, nanohydroxyapatite, gum arabic, cacao bean, liquorice, Brazilian green propolis, tea leaves, and nutmeg (Onishi et al., 2008). The ability of these agents to reduce early dental lesions remains controversial, with several studies failing to demonstrate any significant therapeutic effect (Tellez et al., 2013). Therefore, researchers have long sought to develop useful remineralization agents. Some researchers have focused on remineralizing treatments based on dentin phosphoprotein (DPP). DPP is synthesized by dentin cells and released into the dentin mineralization front; it is a major noncollagenous component of extracellular matrix in dentin (He and George, 2004; White et al., 2007). DPP is involved in several aspects of dentin biomineralization: it nucleates calcification of the dentin matrix; it may help regulate the morphology and growth of hydroxyapatite crystals; and it is a key regulator of mineralized tissue stability. Combining DPP with a solid support, such as agarose beads, induces apatite crystal formation in situ (Lussi et al., 1988). In fact, mixing DPP-coated beads with calcium ions in solution leads to deposition of calcium phosphate on the beads in a Ca:P ratio of 1.33 (Luo et al., 2003). Human DPP contains numerous repeats of the sequence aspartate-serineserine (DSS), which are believed to promote the formation of hydroxyapatite (George et al., 1996). In fact, in vitro studies have shown that DPP can induce the formation of apatite crystals in solutions containing calcium phosphate (Prasad et al., 2010). Evidence suggests that short peptides bearing multiple DSS repeats can reproduce the functions of full-length DPP; these peptides bind with high affinity to calcium phosphate compounds, and when used to coat polystyrene beads, they recruit calcium phosphate to the beads (Yarbrough et al., 2010). Of the multiple-DSS peptides tested so far, a peptide carrying 8 repeats (8DSS) appears to be the most effective at promoting mineral deposition (He et al., 2003; Qiu et al., 2004; Bigi et al., 2006). 8DSS has been shown to promote mineral deposition onto human enamel and improve the surface properties of demineralized enamel (Hsu et al.,

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2011a). This initial work demonstrates the potential of 8DSS as a useful remineralizing agent. To probe this question further, we wanted to examine whether 8DSS works effectively in a system that simulates the cyclic re- and demineralization that occurs in the oral cavity and to verify the remineralization effects of 8DSS quantitatively. Therefore, we measured the effects of 8DSS on remineralization of initial caries lesions in vitro after pH cycling.

Material & Methods Preparation of Materials Bovine permanent incisors without any lesions, cracks, or fluoric mottle were obtained, and a flat uncontaminated surface was created on each incisor with a diamond-coated band saw with continuous water cooling (Struers Minitom, Struers, Copenhagen, Denmark) and water-cooled carborundum discs of waterproof silicon carbide paper (800, 1000, 1200, and 2400 grit; Struers). The blocks were embedded in polymethylmethacrylate and painted with 2 layers of acid-resistant nail varnish, leaving a window (4 × 4 mm) exposed on the labial enamel surface. Before caries lesion formation, surface microhardness (SMH) of the prepared enamel blocks was measured with a microhardness tester (Duramin-1/-2, Struers) and a Knoop indenter at a load of 50 g for 15 s. A total of 120 enamel blocks with an SMH between 320 and 400 Knoop hardness numbers were selected for further study. The nonphosphorylated peptide 8DSS, (Asp-Ser-Ser)8, was dissolved in 50 mM HEPES (pH 7.0) to a final concentration of 25 µM.

Caries Lesion Formation Initial enamel caries lesions were produced in the 120 enamel blocks as described (ten Cate and Duijsters, 1983). The demineralization solution contained 50 mM acetic acid (pH 4.5), 2.2 mM Ca(NO3)2, 2.2 mM KH2PO4, 5.0 mM NaN3 and 0.5 ppm NaF. Blocks were immersed in demineralization solution (4 mL per block) at 37°C for 3 d under continuous, low-speed magnetic stirring (100 rpm). Afterward, the SMH of the samples was measured as described above. A total of 30 enamel blocks with a postdemineralization SMH between 160 and 220 Knoop hardness numbers were selected for subsequent testing. Half the exposed window on each enamel sample was sealed with film and 2 layers of acid-resistant nail varnish, leaving an exposed window of only 4 × 2 mm.

Remineralization Testing All 30 samples were treated to a standard regime of controlled pH cycling (White, 1987). The enamel blocks were alternately immersed in remineralization solution—20 mM HEPES (pH 7.0), 1.5 mM CaCl2, 0.9 mM KH2PO4, 130 mM KCl, 1.0 mM NaN3— and demineralization solution—50 mM acetic acid (pH 4.5), 2.2 mM Ca(NO3)2, 2.2 mM KH2PO4, and 1.0 mM NaN3. During each 24-hr period, blocks were immersed for 23 hr in remineralization solution (4 mL per block) and 1 hr in demineralization

J Dent Res XX(X) 2014 solution (4 mL per block). Blocks were rinsed in distilled deionized water between solution changes. During pH cycling, the 30 blocks were divided into 3 sets of 10, which were treated with 25 µM 8DSS, 1 g/L NaF (positive control), or 50 mM HEPES (pH 7.0) (buffer-only negative control). These treatments were carried out 4 times daily, twice before demineralization (8:00 and 9:00) and twice after demineralization (14:00 and 15:00); during each treatment, blocks were immersed for 5 min (4 mL of solution per block). Samples were rinsed before and after each treatment with distilled deionized water. The pH cycling was performed for 12 d in sealed containers maintained at 37°C with continuous, low-speed magnetic stirring (100 rpm). All solutions were prepared fresh daily.

Polarized Light Microscopy Sections approximately 300 µm thick were cut vertically to the windows on the enamel surfaces with a diamond-coated band saw (Struers). Then all the sections were polished to a thickness of approximately 100 µm, which was verified with a digital micrometer (Mitu-toyo, Tokyo, Japan). Slices were placed on glass microscope slides, immersed in distilled and deionized water, and examined with a polarized light microscope (ECLIPSE ME600L, Nikon, Tokyo, Japan).

Transverse Microradiography Each slice was fixed on Plexiglass slides in a transverse microradiography (TMR) sample holder (Inspektor Research Systems BV, Amsterdam, Netherlands). Then slices were microradiographed alongside an aluminum calibration step-wedge with a monochromatic CuK X-ray source (Philips, Eindhoven, Netherlands) operated at 20 kV and 20 mA and an exposure time of 25 s. Lesion depth, mineral loss, and mineral content at selected depths were analyzed with imaging software (Transversal Microradiography Software 2006, Inspektor Research Systems BV). Ten TMR traces were measured on each slice: 5 traces within areas not exposed to pH cycling and 5 within areas that had been exposed to cycling. Five slices were analyzed from each enamel block. The software calculated the mineral loss in the lesion (vol. % • µm) relative to sound tissue. Lesion depth was determined as the distance from the enamel surface to the point at which mineral content reached 87% that of sound enamel (Xiang et al., 2013).

Statistical Analysis Data were analyzed with SPSS 17.0 (IBM, Chicago, IL, USA). Students paired t test was used to compare mineral loss, lesion depth, and mineral content of the surface layer and lesion body among all the groups before and after pH cycling. Average mineral loss, lesion depth, and mineral content of the surface layer and lesion body after pH cycling were statistically analyzed by analysis of variance, followed by the Student–Newman–Keuls test. The threshold of significance was set at 0.05. Average mineral content at different depths was determined with SPSS 17.0 and plotted with Origin 8.0 (OriginLab, Northampton, MA, USA).

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J Dent Res XX(X) 2014  3 8DSS-Promoted Remineralization

Figure 1. X-ray photoelectron spectroscopy of 8DSS adsorbed to demineralized enamel: (a) the demineralized enamel treated with 8DSS; (b) the demineralized enamel treated with buffer only.

Results The nitrogen present in the peptide bonds and several residues of 8DSS allow the compound to be detected by X-ray photoelectron spectroscopy (Fig. 1), which revealed nitrogen N1s peaks on enamel surfaces exposed to 8DSS solution, though no such peaks were detected on demineralized enamel treated only with buffer. Absorption of 8DSS to the demineralized enamel surface was also observed by atomic force microscopy. The cloudlike masses projecting off the surface of demineralized enamel crystals were found in samples treated with 8DSS but not in either control. Polarized light microscopy (PLM) showed that controlled demineralization produced the expected initial caries lesions before pH cycling and that NaF and 8DSS promoted remineralization after pH cycling. In PLM, the enamel surface layer exhibits negative birefringence and has relatively high mineral content due to remineralization. The lesion body under the surface layer exhibits positive birefringence because of its relatively low mineral content. Before pH cycling, no obvious surface layer was visible in any of our samples, indicating that no remineralization occurred. After pH cycling, a surface layer was clearly visible on enamel treated with 8DSS or NaF but not on enamel treated with buffer only. The samples treated with buffer only looked similar before and after pH cycling, indicating no significant remineralization. The lesions after pH cycling were significantly shallower in the NaF- and 8DSS-treated groups than in the buffer-only group. These results provide direct evidence of remineralization promoted by 8DSS and NaF. Similarly, TMR showed that lesions became significantly shallower after pH cycling in the presence of 8DSS or NaF, whereas lesion depth did not change significantly when only buffer was added during pH cycling (Table). In fact, 8DSS reduced lesion depth to a similar extent as NaF, and both treatments led to similar mineral loss, which was significantly smaller than the loss in buffer-only samples. Mineral deposition was significantly greater in the 8DSS- and NaF-treated samples

Figure 2.  Mineral content (vol. % • µm) vs. depth (µm) for lesions subjected to 12 d of pH cycling, treated daily with 8DSS, NaF, or buffer only, as indicated. Profiles are averages (± SD) per experimental group (for each group, n = 10, 5 scans per specimen) and for all the demineralized enamel, analyzed prior to pH cycling (n = 30, 5 scans per specimen). This figure is available in color online at http://jdr .sagepub.com.

than in the buffer-only samples, not only at the surface layer but also within the lesion body. Figure 2 shows mineral content at different depths before and after pH cycling for all 3 treatment groups. As expected, the buffer-only group showed the lowest mineral content after cycling, similar to the mineral content before cycling. 8DSS samples showed significantly greater mineral content than buffer-only samples at depths of 30 to 110 µm, corresponding to the lesion. These 2 sets of samples showed the greatest differences in mineral content at a depth of 50 µm, whereas the mineral content in both groups was similar at depths beyond 130 µm. At all depths examined, the NaF group showed mineral content similar to that of the 8DSS group.

Discussion This study provides direct in vitro evidence that the DPPderived peptide 8DSS promotes enamel remineralization, suggesting that it has significant potential for remineralizing demineralized enamel. Our results, obtained with bovine enamel in an in vitro system, lay the foundation for optimizing the peptide system and testing it in vivo. DPP contains numerous negatively charged aspartic acid and phosphorylated serine residues (Jonsson and Fredriksson, 1978; Stetler-Stevenson and Veis, 1987). Computational and biochemical studies of the (DSS)3-83-8 repeat sequence of DPP suggest that this region governs the mineral binding and nucleating activity of DPP (George et al., 1996; Veis et al., 1998; Chang et al., 2006). In fact, one study showed that peptides with these repeats, even when nonphosphorylated, bind tightly and specifically to calcium phosphate compounds (Yarbrough et al., 2010), suggesting that the repeat motif on its own might be useful for promoting deposition of calcium phosphate on biological surfaces such as tooth enamel.

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J Dent Res XX(X) 2014

Table.  Mineral Loss, Lesion Depth, and Mineral Content of the Surface Layer and Lesion Body of All Groups before and after pH Cycling Mineral Loss (vol. % • µm) Treatment 8DSS NaF HEPES

Before

Lesion Depth (µm)

After

2436 ± 858 2723 ± 926a 2133 ± 673a a

Before

1561 ± 479 * 1586 ± 475b* 2333 ± 598c b

Surface Layer (vol. %)

After

106 ± 31 122 ± 20d 117 ± 29d d

82 ± 28 * 93 ± 11e* 115 ± 25f e

Lesion Body (vol. %)

Before

After

58 ± 8 59 ± 8g 63 ± 4g

67 ± 5 * 69 ± 4h* 59 ± 3i

g

Before h

After

78 ± 7 74 ± 4j 78 ± 3j j

84 ± 4k* 83 ± 5k* 77 ± 4l

Mean ± SD, n = 10. Different letters in the same column denote that treatments are of significant difference (p < .05). *Denotes significant difference between before and after pH cycling of each treatment (p < .05).

We tested this possibility directly using a peptide with 8 repeats, which has proven more effective than other (DSS)n peptides at promoting remineralization in vitro (He et al., 2003; Qiu et al., 2004). To quantitate rigorously whether 8DSS shows significant remineralizing activity in vitro, we used the gold-standard technique of TMR (ten Cate et al., 1996) to analyze the demineralization and remineralization of enamel after treatment with 8DSS, NaF, or buffer alone. TMR analysis showed that mineral loss, lesion depth, and mineral content of the surface layer and lesion body after pH cycling were similar in samples treated with 8DSS or NaF (Table). PLM results were consistent with the TMR results. These findings suggest that 8DSS promotes remineralization of initial enamel caries lesions. In the meantime, we detected no significant differences in integrated mineral loss or lesion depth before and after pH cycling in the enamel samples treated only with buffer. This lack of demineralization in our negative controls may have been due to our cycling conditions, which did not provide an extremely cariogenic challenge. Therefore, we interpret our results as demonstrating that 8DSS can enhance lesion repair in vitro, but further studies are needed to examine whether it can also reverse lesion progression. Samples treated with 8DSS or NaF showed higher mineral content than samples treated with buffer alone at depths of 30 to 110 µm. Beyond a depth of 130 µm, however, all 3 treatment groups showed similar mineral contents. 8DSS is thought to affect the rates of mineral loss from enamel by adsorbing to the enamel surface and creating a diffusion barrier (Gregory et al., 1991). This barrier may reduce calcium loss, which would explain the higher mineral content in the lesion bodies of our 8DSS-treated samples. DSS peptides bind strongly not only to calcium and phosphate ions (George et al., 1996) but also to the surface of hydroxyapatite (Yarbrough et al., 2010), giving them in essence 2 mineral-binding surfaces. This suggests that DSS peptides adsorbed onto the enamel enhance lesion repair by preventing the dissolution of calcium and phosphate ions from the enamel into the surrounding medium while promoting the capture of these ions from solution and their mineralization into the enamel surface. This dual mechanism may help explain how the 8DSS peptide promoted mineral deposition onto bovine enamel in the present study and how it promoted remineralization of human enamel and improved the surface properties of demineralized enamel in previous work (Hsu et al., 2011a). To the best of our knowledge, the present work is the first demonstration of the use of 8DSS peptides to promote the

remineralization of initial enamel carious lesions. Our findings concur with those of a recent study showing that the same peptide can initiate mineral deposition on human tooth surfaces and enhance the ability of a commercial product to remineralize partially demineralized dentin (Hsu et al., 2011b). Together, these studies strongly suggest that 8DSS has the potential to remineralize demineralized enamel. 8DSS presents several advantages for clinical use. First, it is a short peptide and so may not be an easy target for hydrolytic enzymes in the oral cavity. Second, 8DSS is expected to show minimal toxicity since it is derived from naturally occurring DPP, which also suggests that 8DSS should act by a similar mechanism as full-length DPP. Third, 8DSS binds strongly to calcium phosphate compounds, which may help accelerate the rate of remineralization (Hsu et al., 2011a). Nevertheless, 8DSS is likely to present some disadvantages in the clinic. One predicted challenge is that because the peptide binds calcium, it may lead to calculus formation in the oral cavity. While ensuring that 8DSS is applied locally may help reduce this risk, future work should explore this and other potential disadvantages of 8DSS using in vitro systems that more closely simulate natural processes in the oral cavity, including the presence of biofilms, saliva, acquired pellicle, continuous flow, and surface abrasion. If in vitro studies with enamel lesions confirm the clinical promise of 8DSS, then in vivo studies will be needed to examine its potential as an agent to promote the remineralization of demineralized enamel.

Acknowledgments The authors are grateful for support from the National Natural Science Foundation of China (grants 81000431 and 81271128) and the New Century Excellent Talents University Support Program. The authors also thank the Crest Research Laboratory of Procter & Gamble Technology (Beijing) Co. Ltd. for help with transverse microradiography analyses. The authors declare no potential conflicts of interest with respect to the authorship and/or publication of this article.

References Bigi A, Boanini E, Rubini K, Gazzano M (2006). Hydroxyapatite nanocrystals modified with acidic amino acids. Eur J Inorg Chem 23:4821-4826. Chang S, Chen H, Liu J, Wood D, Bentley P, Clarkson B (2006). Synthesis of a potentially bioactive, hydroxyapatite-nucleating molecule. Calcif Tissue Int 78:55-61.

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J Dent Res XX(X) 2014  5 8DSS-Promoted Remineralization Ehrlich H, Koutsoukos PG, Demadis KD, Pokrovsky OS (2009). Principles of demineralization:modern strategies for the isolation of organic frameworks: part II. Decalcification. Micron 40:169-193. George A, Bannon L, Sabsay B, Dillon JW, Malone J, Veis A, et al. (1996). The carboxyl-terminal domain of phosphophoryn contains unique extended triplet amino acid repeat sequences forming ordered carboxylphosphate interaction ridges that may be essential in the biomineralization process. J Biol Chem 271:32869-32873. Gregory TM, Chow LC, Carey CM (1991). A mathematical model for dental caries: a coupled dissolution-diffusion process. J Res Natl Inst Stand Technol 96:593-604. He G, George A (2004). Dentin matrix protein 1 immobilized on type I collagen fibrils facilitates apatite deposition in vitro. J Biol Chem 279:11649-11656. He G, Dahl T, Veis A, George A (2003). Nucleation of apatite crystals in vitro by self-assembled dentin matrix protein 1. Nat Mater 2:552-558. Hsu CC, Chung HY, Yang JM, Shi W, Wu B (2011a). Influence of 8DSS peptide on nano-mechanical behavior of human enamel. J Dent Res 90:88-92. Hsu CC, Chung HY, Yang JM, Shi W, Wu B (2011b). Influences of ionic concentration on nanomechanical behaviors for remineralized enamel. J Mech Behav Biomed Mater 4:1982-1989. Jonsson M, Fredriksson S (1978). Isoelectric focusing of the phosphoprotein of rat-incisor dentin in ampholine and acid pH gradients: evidence for carrier ampholyte-protein complexes. J Chromatogr 157:235-242. Luo SJ, Li YJ, Wan L, Su Y (2003). The effect of dentin phosphoprotein on inducing mineralization. Zhong Hua Kou Chiang Yi Xue Za Zhi 38:56-58. Lussi A, Crenshaw MA, Linde A (1988). Induction and inhibition of hydroxyapatite formation by rat dental phosphoprotein in vitro. Arch Oral Biol 33:685-691. Onishi T, Umemura S, Yanagawa M, Matsumura M, Sasaki Y, Ogasawara T, et al. (2008). Remineralization effects of gum arabic on caries-like enamel lesions. Arch Oral Biol 53:257-260. Panich M, Poolthong S (2009). The effect of casein phosphopeptideamorphous calcium phosphate and a cola soft drink on in vitro enamel hardness. J Am Dent Assoc 140:455-460.

Prasad M, Butler WT, Qin C (2010). Dentin sialophosphoprotein in biomineralization. Connect Tissue Res 51:404-417. Qiu SR, Wierzbicki A, Orme CA, Cody AM, Hoyer JR, Nancollas GH, et al. (2004). Molecular modulation of calcium oxalate crystallization by osteopontin and citrate. Proc Natl Acad Sci U S A 101:1811-1815. Stetler-Stevenson WG, Veis A (1987). Bovine dentin phosphophoryn: calcium ion binding properties of a high molecular weight preparation. Calcif Tissue Int 40:97-102. Tellez M, Gomez J, Kaur S, Pretty IA, Ellwood R, Ismail AI (2013). Nonsurgical management methods of noncavitated carious lesions. Community Dent Oral Epidemiol 41: 79-96. ten Cate JM, Duijsters PP (1983). Influence of fluoride in solution on tooth demineralization: I. Chemical-data. Caries Res 17:193-199. ten Cate JM, Dundon KA, Vernon PG, Damato FA, Huntington E, Exterkate RA, et al. (1996). Preparation and measurement of artificial enamel lesions, a four-laboratory ring test. Caries Res 30:400-407. Veis A, Wei K, Sfeir C, George A, Malone J (1998). Properties of the (DSS) n triplet repeat domain of rat dentin phosphophoryn. Eur J Oral Sci 106(Suppl 1):234-238. White DJ (1987). Reactivity of fluoride dentifrices with artificial caries: I. Effects on early lesions: F uptake, surface hardening and remineralization. Caries Res 21:126-140. White SN, Paine ML, Ngan AY, Miklus VG, Luo W, Wang H, et al. (2007). Ectopic expression of dentin sialoprotein during amelogenesis hardens bulk enamel. J Biol Chem 282:5340-5345. Xiang CY, Ran JM, Yang QQ, Li W, Zhou XD, Zhang LL (2013). Effects of enamel matrix derivative on remineralisation of initial enamel carious lesions in vitro. Arch Oral Biol 58:362-369. Yarbrough DK, Hagerman E, Eckert R, He J, Choi H, Cao N, et al. (2010). Specific binding and mineralization of calcified surfaces by small peptides. Calcif Tissue Int 86:58-66. Zhang LL, Li JY, Zhou XD, Cui FZ, Li W (2009). Effects of Galla chinensis on the Surface Topography of Initial Enamel Carious Lesion: An Atomic Force Microscopy Study. Scanning 31:195-203.

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8DSS-promoted remineralization of initial enamel caries in vitro.

Peptides containing 8 repeats of aspartate-serine-serine (8DSS) have been shown to promote the nucleation of calcium phosphate from solution into huma...
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