Effect of a Calcium Carbonate-Based Dentifrice on in situ Enamel Remineralization

The Synergistic Effect of High Intensity Focused Ultrasound on In-vitro Remineralization of Tooth Enamel by Calcium Phosphate Ion Clusters

Background

Remineralization of dental enamel is an important intervention strategy for the treatment of demineralized lesions. Existing approaches have limitations such as failure to adequately reproduce both the ideal structural and mechanical properties of the native tooth. The ability of ultrasound to control and accelerate the crystallization processes has been widely reported. Therefore, a new approach was explored for in-vitro enamel remineralization involving the synergistic effect of high-intensity focused ultrasound (HIFU) coupled with calcium phosphate ion clusters (CPICs).

Methods

The demineralized enamel was treated with CPICs, with or without subsequent HIFU exposure for different periods (2.5, 5, and 10 min). The specimens were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. The surface hardness and crystallographic properties of the treated specimens were evaluated using Vickers microhardness testing and X-ray diffraction (XRD), respectively.

Results

SEM revealed distinct, organized, and well-defined prismatic structures, showing clear evidence of remineralization in the combined CPIC/HIFU treatment groups. AFM further revealed a decrease in the surface roughness values with increasing HIFU exposure time up to 5 min, reflecting the obliteration of interprismatic spaces created during demineralization. The characteristic Raman band at 960 cm-1 associated with the inorganic phase of enamel dominated well in the HIFU-treated specimens. Importantly, microhardness testing further demonstrated that new mineral growth also recovered the mechanical properties of the enamel in the HIFU-exposed groups. Critical to our aspirations for developing this into a clinical process, these results were achieved in only 5 min.

Conclusion

HIFU exposure can synergise and significantly accelerate in-vitro enamel remineralization process via calcium phosphate ion clusters. Therefore, this synergistic approach has the potential for use in future clinical interventions.

Unveiling the mechanism of an amelogenin-derived peptide in promoting enamel biomimetic remineralization

Amelogenin and its derived peptides have exhibited excellent efficacy in promoting enamel biomimetic remineralization. However, little is known about their specific action mechanisms. Herein, by combining experiments and computer simulation, the mechanism of an amelogenin-derived peptide QP5 in regulating enamel biomimetic remineralization is unveiled for the first time. In experiments, peptide QP5 was separated into (QPX)5 and C-tail domains, the interactions of peptide-minerals in nucleation solution and the regulation of peptide on enamel biomimetic remineralization were explored. QP5 exhibited an unordered conformation when mineral ions existed, and it could adsorb on minerals through its two domains, thereby inhibiting spontaneous nucleation. The remineralized enamel regulated by C-tail showed better mechanical properties and formed more biomimetic crystals than that of (QPX)5, indicating the C-tail domain of QP5 played an important role in forming enamel-like crystals. The simulation results showed that the conformation of QP5 changed greatly, mainly exhibiting β-bend, β-turn, and coil structures, and it eventually adsorbed on enamel through negatively charged residues of the C-tail domain, then captured Ca2+ from solution to promote enamel remineralization. This study improved the evaluation methods of the mechanism of biomimetic peptides, and laid a theoretical basis for the amelioration and clinical transformation of peptide QP5.

Synthesis and Characterization of Bioactive Glass and Zinc Oxide Nanoparticles with Enamel Remineralization and Antimicrobial Capabilities

BACKGROUND

We investigated the effect of bioactive glass and zinc oxide nanoparticles on enamel remineralization, as well as their antimicrobial effect on cariogenic microbes. This is the first study that investigated the properties of bioactive glass and zinc oxide nanoparticles with mixed materials.

METHODS

Fluoride gel (F), bioactive glass microparticles (µB), bioactive glass nanoparticles (nB), zinc oxide nanoparticles (Z), and a mixed suspension of nB and Z (nBZ) were prepared and characterized by scanning and transmission electron microscopy, zeta potential measurement, X-ray diffraction, and acid buffering capacity testing. Further, we performed a remineralization cycle test of 28 days, and nanoindentation testing was carried out during the immersion period, and then the enamel surfaces were examined using scanning electron microscopy. Additionally, the antimicrobial effects of the sample suspensions were evaluated by measuring their minimum microbicidal concentrations against various cariogenic microbes.

RESULTS

Our results revealed that nB had a near-circular shape with an amorphous structure and a considerably large specific surface area due to nanoparticulation. Additionally, nB possessed a rapid acid buffering capacity that was comparable to that of μB. In the remineralization test, faster recovery of mechanical properties was observed on the enamel surface immersed in samples containing bioactive glass nanoparticles (nB and nBZ). After remineralization, demineralized enamel immersed in any of the samples showed a rough and porous surface structure covered with mineralized structures. Furthermore, nBZ exhibited a broad antimicrobial spectrum.

CONCLUSIONS

These results demonstrated that bioactive glass and zinc oxide nanoparticles have superior demineralization-suppressing and remineralization-promoting effects.

Influence of salivary acquired pellicle on colour changes and minerals content of dentine after application of silver diamine fluoride followed by potassium iodide

PURPOSE

This study evaluated whether the presence of the salivary acquired pellicle (AP) had any effect on the dentin's darkening and on the caries arresting effect after the use of SDF + KI, in a cariogenic challenge.

METHODS

Human dentin specimens were standardised, submitted to artificial caries lesion formation, and divided into five groups (n = 20): C: control group-no treatment, SDF: 38% SDF, APSDF: SDF 38% and AP, KISDF: 38% SDF and KI, and APKISDF: 38% SDF, KI and AP, that were submitted to pH cycling. Colour evaluation (CIE L*a*b* system) and surface hardness were performed before and after the treatments/pH cycling.

RESULTS

SDF and APSDF groups showed no difference in colour. KISDF and APKISDF groups showed significantly different colours than the groups without KI. SDF, APSDF, and APKISDF groups had less mineral loss than C and KISDF. SDF, APSDF, and APKISDF revealed significantly greater mineral recovery, compared to KISDF and C.

CONCLUSION

The AP did not influence the dentin´s colour after SDF + KI, but had a protective role in modulating the dentin´s mineral gain/loss. KI used after SDF decreased the dentin´s darkening, and did not interfere with the dentin de/remineralization process.

A novel amelogenesis-inspired hydrogel composite for the remineralization of enamel non-cavitated lesions

Enamel non-cavitated lesions (NCLs) are subsurface enamel porosity from carious demineralization. The developed enamel cannot repair itself once NCLs occurs. The regeneration of mineral crystals in a biomimetic environment is an effective way to repair enamel subsurface defects. Previously, an amelogenin-derived peptide named QP5 was proven to repair demineralized enamel. In this work, inspired by amelogenesis, a novel biomimetic hydrogel composite containing the QP5 peptide and bioactive glass (BG) was designed, in which QP5 could promote enamel remineralization by guiding the calcium and phosphorus ions provided by BG. Also, BG could adjust the mineralization micro-environment to alkalinity, simulating the pH regulation of ameloblasts during enamel maturity. The BQ hydrogel composite showed biosafety and possessed capacity for enamel binding, ion release and pH buffering. Enamel NCLs treated with the BQ hydrogel composite showed a higher reduction in lesion depth and mineral loss both in vitro and in vivo. Moreover, compared to the hydrogels containing only BG or QP5, groups treated with the BQ hydrogel composite attained more surface microhardness recovery and color recovery, exhibiting resistance to erosion and abrasion of the remineralization layer. We envision that the BQ hydrogel composite can provide a biomimetic micro-environment to favor enamel remineralization, thus reducing the lesion depth and increasing the mineral content as a promising biomimetic material for enamel NCLs.

Comparison of calcium-based technologies to remineralise enamel subsurface lesions using microradiography and microhardness

Assessment of enamel subsurface lesion remineralisation is essential for the evaluation of novel remineralisation technologies. The gold standard to assess subsurface mineral gain of enamel lesions is transverse microradiography (TMR). However, some studies have utilised surface microhardness (SMH) to evaluate efficacy of remineralisation agents. The aim of this study was to assess remineralisation of enamel subsurface lesions using TMR and SMH after in vitro treatment with calcium-containing technologies, and to test correlation between the TMR and SMH measurements. The parameters obtained from the TMR and SMH analyses of enamel subsurface remineralisation were not significantly correlated. Furthermore, the enamel subsurface remineralisation as measured by TMR was significantly correlated with the water-soluble calcium concentration of the remineralisation products. Scanning electron microscopy revealed surface precipitates formed by specific remineralisation treatments obfuscated accurate assessment of remineralisation by SMH. It was concluded that TMR is a more appropriate method for analysis of enamel subsurface remineralisation, and that SMH values of remineralised enamel should be interpreted with caution. Using TMR the level of remineralisation (%R) by the different technologies was CPP-ACP/F (31.3 ± 1.4%); CPP-ACP (24.2 ± 1.4%); CaSO₄/K₂HPO₄/F (21.3 ± 1.4%); f-TCP/F (20.9 ± 1.0%); Nano-HA/F (16.3 ± 0.3%); Nano-HA (15.3 ± 0.6%) and F alone control (15.4 ± 1.3%).

Two-in-one strategy: a remineralizing and anti-adhesive coating against demineralized enamel

Tooth enamel is prone to be attacked by injurious factors, leading to a de/remineralization imbalance. To repair demineralized enamel and prevent pulp inflammation caused by biofilm accumulation, measures are needed to promote remineralization and inhibit bacterial adhesion on the tooth surface. An innovative material, poly (aspartic acid)-polyethylene glycol (PASP-PEG), was designed and synthesized to construct a mineralizing and anti-adhesive surface that could be applied to repair demineralized enamel. A cytotoxicity assay revealed the low cytotoxicity of synthesized PASP-PEG. Adsorption results demonstrated that PASP-PEG possesses a high binding affinity to the hydroxyapatite (HA)/tooth surface. In vitro experiments and scanning electron microscopy (SEM) demonstrated a strong capacity of PASP-PEG to induce in situ remineralization and direct the oriented growth of apatite nanocrystals. Energy dispersive X-ray spectroscopy (EDS), X-ray diffraction analysis (XRD) and Vickers hardness tests demonstrated that minerals induced by PASP-PEG were consistent with healthy enamel in Ca/P ratio, crystal form and surface micro-hardness. Contact angle tests and bacterial adhesion experiments demonstrated that PASP-PEG yielded a strong anti-adhesive effect. In summary, PASP-PEG could achieve dual effects for enamel repair and anti-adhesion of bacteria, thereby widening its application in enamel repair.

Remineralization of enamel caries by an amelogenin-derived peptide and fluoride in vitro

Dental caries is one of the most common oral diseases in the world. This study was tantamount to investigate the combinatory effects of an amelogenin-derived peptide (called QP5) and fluoride on the remineralization of artificial enamel caries. The peptide QP5 was synthesized and characterized, and the binding capability of the peptide on hydroxyapatite (HA) and demineralized tooth enamel surface was analysed. Then, the mineralization function of the peptide and fluoride was studied through the spontaneous mineralization testing and remineralization on enamel caries in vitro. First, the novel peptide QP5 could bind on the hydroxyapatite and demineralized tooth enamel surfaces. Second, QP5 can transitorily stabilize the formation of amorphous calcium phosphate and direct the transformation into hydroxyapatite crystals alone and in combination with fluoride. In addition, compared to blocks treated by peptide QP5 alone or fluoride, the sample blocks showed significantly higher surface microhardness, lower mineral loss and shallower lesion depth after treatment with a combination of QP5 and fluoride at high or low concentrations. The peptide QP5 could control the crystallization of hydroxyapatite, and combinatory application of peptide QP5 and fluoride had a potential synergistic effect on the remineralization of enamel caries.

Fluoride Penetration and Clearance Are Higher in Exopolysaccharide-Containing Bacterial Pellets

Extracellular polysaccharides (EPS) could increase the penetration of fluoride through dental biofilm, reducing its cariogenicity. We measured the concentration of fluoride in EPS-containing (EPS+) or not-containing (EPS-) Streptococcus mutans bacterial pellets resembling test biofilms, before and up to 60 min after a 0.05% NaF rinse in situ. Fluoride penetration and clearance were higher in EPS+ bacterial pellets. The data suggest that EPS enhances fluoride penetration, but also accelerates fluoride clearance from dental biofilms.

Anti-biofilm and remineralization effects of chitosan hydrogel containing amelogenin-derived peptide on initial caries lesions

In this study, we have designed a more clinically powerful anti-caries treatment by applying the amelogenin-derived peptide QP5 to the antibacterial carrier material chitosan in a hydrogel (CS-QP5 hydrogel), and characterized its effects on the inhibition of a cariogenic biofilm and the promotion of the remineralization of the initial caries lesions. The results indicated that the CS-QP5 hydrogel sustainably inhibited the growth of the Streptococcus mutans biofilm, lactic acid production and the metabolic activity over a prolonged period of time. Moreover, the CS-QP5 hydrogel promoted the remineralization of early enamel lesions, which were indicated by surface micro-hardness (, polarized light microscopy and transverse microradiography. In conclusion, the CS-QP5 hydrogel shows good potential for caries control in the clinic because of its antibacterial effects as well as the remineralization of initial enamel carious lesions even in a biofilm model over a prolonged period of time.

A statherin-derived peptide promotes hydroxyapatite crystallization and in situ remineralization of artificial enamel caries

In situ remineralization of hydroxyapatite on a human tooth enamel surface induced by anti-caries bioactive components is an alternative restorative strategy against dental caries. In this study, a novel biomimetic peptide DE-11, inspired by the salivary phosphoprotein statherin, was developed, and it showed beneficial potentials for the restoration of demineralized tooth enamel in vitro. The peptide DE-11 contained the initial six-peptide sequence of N-terminus of statherin extended by a mineralization hydrophilic tail composed of consecutive acidic amino acids capable of adsorbing calcium and phosphate ions. A strong adsorption capacity of DE-11 to hydroxyapatite was confirmed through Langmuir adsorption isotherm experiment and confocal laser scanning microscopy. Then, the nucleation and crystallization of hydroxyapatite due to DE-11 was characterized by scanning and transmission electron microscopy and selected-area electron diffraction. Moreover, the ability of DE-11 to promote the remineralization of initial enamel caries lesions was further evaluated. Initial lesions were created in bovine enamel blocks, which were then exposed to the peptide solution and finally immersed in artificial saliva. After 7 days, a higher percentage of surface microhardness recovery, a lower mineral loss, a shallower lesion depth, and a higher mineral content were found on the surface of the lesion body in the DE-11 group as compared to that in the negative group using surface microhardness testing, polarized light microscopy, and transverse microradiography; this indicated that DE-11 could induce in situ remineralization of hydroxyapatite on the demineralized enamel surface. Overall, these findings suggest that DE-11 is highly promising as a restorative biomaterial for enamel remineralization in the anti-caries applications.

A novel biomimetic peptide inspired by salivary statherin was developed and exhibited beneficial potentials in promoting remineralization of hydroxyapatite on tooth enamel surface, providing a desirable alternative restorative strategy against dental caries.

Frequency of Fluoride Dentifrice Use and Caries Lesions Inhibition and Repair

The clinical relevance of the frequency of fluoride dentifrice (FD) use on enamel caries is based on evidence. However, the relative effect of FD on reduction of demineralization or enhancement of remineralization is unknown and the effect of frequency on root dentine caries has not been explored. The aim of this double-blind, crossover, in situ study, which was conducted in 4 phases of 14 days each, was to evaluate the relationship between the frequency of FD use and enamel and root dentine de- and remineralization. Eighteen volunteers wore palatal appliances containing enamel and root dentine slabs, either sound or carious. Biofilm accumulation on the slab surface was allowed, and 20% sucrose solution was dripped 3 or 8 times per day on the carious and sound slabs, respectively. Volunteers used FD (1,100 μg F/g) in the frequencies 0 (fluoride-placebo dentifrice), 1, 2 and 3 times per day. The demineralization and remineralization that occurred in sound or carious slabs was estimated by the percentage of surface hardness loss (%SHL) or recovery (%SHR). Loosely (CaF2) and firmly (FAp) bound fluoride concentrations were also determined. The relationship between the variables was analyzed by linear regression. The %SHL, CaF2 and FAp concentrations were a function of the frequency of FD use for enamel and dentine, but the %SHR was a function of the frequency of FD use only for enamel (p < 0.05). The results suggest that demineralization in enamel and root dentine is reduced in proportion to the frequency of FD use, but for remineralization the effect of the frequency of FD use was relevant only to enamel.

Potential of an amelogenin based peptide in promoting reminerlization of initial enamel caries

OBJECTIVE

In this study we give a preliminary study of a rationally designed small peptide, which is based on the enamel matrix protein amelogenin, to investigate its effect on remineralization of initial enamel caries lesions.

DESIGN

A novel peptide was designed and synthesized to investigate its effects on the remineralization of initial enamel carious lesions during pH cycling that simulates intra-oral conditions. Initial lesions were created in bovine enamel blocks, which were then pH-cycled for 12 days in the presence of 25μM peptide, 1g/L NaF (positive control), 50mM HEPES buffer(negative control). Before and after pH cycling, enamel blocks were analyzed by surface microhardness testing, polarized light microscopy and transverse microradiography.

RESULTS

Percentage of surface microhardness recovery (SMHR%) after pH cycling was significantly higher in peptide group than HEPES group. Lower lesion depth and less mineral mineral loss were found in peptide or NaF treatment groups after the cycling, and were significantly different to HEPES group. No significant differences were observed between the blocks treated with peptide and those treated with NaF.

CONCLUSSION

This study provides in vitro evidence that this amelogenin based peptide promotes enamel caries remineralization, offering a promising remineralizing biomaterial in initial enamel carious treatment.

Effectiveness of fluorescence-based methods to detect in situ demineralization and remineralization on smooth surfaces

This study aimed to evaluate the effectiveness of fluorescence-based methods (DIAGNOdent, LF; DIAGNOdent pen, LFpen, and VistaProof fluorescence camera, FC) in detecting demineralization and remineralization on smooth surfaces in situ. Ten volunteers wore acrylic palatal appliances, each containing 6 enamel blocks that were demineralized for 14 days by exposure to a 20% sucrose solution and 3 of them were remineralized for 7 days with fluoride dentifrice. Sixty enamel blocks were evaluated at baseline, after demineralization and 30 blocks after remineralization by two examiners using LF, LFpen and FC. They were submitted to surface microhardness (SMH) and cross-sectional microhardness analysis. The integrated loss of surface hardness (ΔKHN) was calculated. The intraclass correlation coefficient for interexaminer reproducibility ranged from 0.21 (FC) to 0.86 (LFpen). SMH, LF and LFpen values presented significant differences among the three phases. However, FC fluorescence values showed no significant differences between the demineralization and remineralization phases. Fluorescence values for baseline, demineralized and remineralized enamel were, respectively, 5.4 ± 1.0, 9.2 ± 2.2 and 7.0 ± 1.5 for LF; 10.5 ± 2.0, 15.0 ± 3.2 and 12.5 ± 2.9 for LFpen, and 1.0 ± 0.0, 1.0 ± 0.1 and 1.0 ± 0.1 for FC. SMH and ΔKHN showed significant differences between demineralization and remineralization phases. There was a negative and significant correlation between SMH and LF and LFpen in the remineralization phase. In conclusion, LF and LFpen devices were effective in detecting demineralization and remineralization on smooth surfaces provoked in situ.

Microstructure and nanomechanical properties of enamel remineralized with asparagine-serine-serine peptide

A highly biocompatible peptide, triplet repeats of asparagine-serine-serine (3 NSS) was designed to regulate mineral deposition from aqueous ions in saliva for the reconstruction of enamel lesions. Healthy human enamel was sectioned and acid demineralized to create lesions, then exposed to the 3 NSS peptide solution, and finally immersed in artificial saliva for 24h. The surface morphology and roughness were examined using scanning electron microscopy (SEM) and atomic force microscopy (AFM), respectively. X-ray diffraction (XRD) was used to identify the phases and crystallinity of the deposited minerals observed on the enamel surface. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used to quantitatively analyze the mineral variation by calculating the relative integrated-area of characteristic bands. Nanohardness and elastic modulus measured by nanoindentation at various treatment stages were utilized to evaluate the degree of recovery. Biomimetic effects were accessed according to the degree of nanohardness recovery and the amount of hydroxyapatite deposition. The charged segments in the 3 NSS peptide greatly attracted aqueous ions from artificial saliva to form hydroxyapatite crystals to fill enamel caries, in particular the interrod areas, resulting in a slight reduction in overall surface roughness. Additionally, the deposited hydroxyapatites were of a small crystalline size in the presence of the 3 NSS peptide, which effectively restrained the plastic deformations and thus resulted in greater improvements in nanohardness and elastic modulus. The degree of nanohardness recovery was 5 times greater for remineralized enamel samples treated with the 3 NSS peptide compared to samples without peptide treatment.

In situ effect of a dentifrice with low fluoride concentration and low pH on enamel remineralization and fluoride uptake

Since the anticaries effect of a dentifrice with low fluoride concentration and low pH is unknown, the aim of the present study was to evaluate in situ the enamel remineralizing ability of this type of formulation. A double-blind crossover design employing 3 phases of 45 days was conducted. Six adult volunteers wore palatal devices containing 6 previously demineralized human dental enamel slabs, which were subjected 3 times a day to one of the following treatments: non-fluoridated dentifrice (negative control); dentifrice containing 1, 100 microg F/g, pH 7.0 (positive control); dentifrice containing 550 microg F/g, pH 5.5 (experimental). At the end of each phase, enamel remineralization was assessed in terms of cross-sectional microhardness, and loosely as well as firmly bound fluoride formation was determined on the enamel surface. Fluoridated dentifrices were more effective than the negative control in forming loosely and firmly bound fluoride on enamel (P < 0.05). However, the positive control formed more loosely bound fluoride than the other treatments (P < 0.05). Microhardness analysis showed that the fluoridated dentifrices were more effective than the negative control (P < 0.05) in remineralizing dental enamel, although no statistically significant difference was observed between them. Thus, the experimental dentifrice was shown to be effective in remineralizing dental enamel, and this may be attributable to its ability to form firmly bound fluoride on enamel.

Effect of compounds of Galla chinensis on remineralisation of initial enamel carious lesions in vitro

OBJECTIVE

To evaluate the effect of compounds of Galla chinensis on the remineralisation of initial enamel carious lesions in vitro.

METHODS

Sixty bovine enamel blocks with early lesions were prepared and randomly divided into six treatment groups. The lesions were subjected to a pH-cycling regime for 12 days. Each daily cycle included 4x1min applications with one of six treatments; 1000ppm F aq. (as NaF, positive control); deionized water (negative control); or 4000ppm aqueous solutions of four G. chinensis extracts (GCEs); GCE, GCE-B, GCE-B1, or GCE-B2. Surface enamel microhardness was measured on the enamel blocks before and after demineralisation, and after pH-cycling, and percentage surface microhardness recovery (%SMHR) was calculated. The enamel specimens were then sectioned (thickness ca. 80microm) and examined by polarized light microscopy.

RESULTS

All samples rehardened significantly compared to baseline. Fluoride had a significantly greater effect than all other treatments. In the GCEs groups, %SMHR was significantly greater than DDW for the GCE, GCE-B and GCE-B1 groups. There was no significant difference between the GCE-B2 group and DDW. Polarized light microscopy showed that the thickness of the surface layer increased obviously in all specimens including NaF group, GCE group, GCE-B group and GCE-B1 group. Negative birefringent band appeared in the lesions body and the depth of the lesions was obviously reduced.

CONCLUSION

The present study has demonstrated the potential of three GCEs (GCE, GCE-B and GCE-B1) to effect net rehardening of artificial carious lesions under dynamic pH-cyclic conditions.

Effect of xylitol:sorbitol on fluoride enamel demineralization reduction in situ

OBJECTIVES

To evaluate if sugar alcohols would reduce enamel demineralization enhancing the fluoride (F) effect.

METHODS

A crossover in situ study was conducted in four phases, during which 10 volunteers were submitted to one of the treatments: (I) Distilled and deionized water, as a negative control; (II) F (226 microg F/ml as NaF; concentration used in commercial mouthrinse); (III) X:S (xylitol:sorbitol 1:3; final concentration 1.6M; 28% of sugar alcohols) and (IV) F+X:S (same final concentration that groups II and III). The volunteers wore palatal appliances containing four bovine enamel blocks of known surface microhardness (SMH), covered with a 'test plaque' of mutans streptococci, which were immersed during 1 min in one of the allocated treatment solutions simultaneously that the volunteers rinsed their mouths with the same solution. After the rinsing the appliances were put in the mouth and after 20 min a cariogenic challenge was made with 20% sucrose solution during 1 min. After further 45 min the 'test plaque' was collected for F analysis, enamel SMH was again determined and the percentage of change in relation to baseline was calculated; F uptake in enamel was also determined.

RESULTS

With respect to all the analyses made, the group F+X:S did not differ from the F treatment (p>0.05) and the groups treated with F and F+X:S differed from the negative control (p<0.05).

CONCLUSIONS

The results suggest that xylitol:sorbitol may not enhance the effect of fluoride present in mouth rinse on the reduction of enamel demineralization.

The short-term in situ model to evaluate the anticariogenic potential of ionomeric materials

OBJECTIVES

Aiming to contribute to the study of mechanisms involved in the anticariogenic properties of dental materials, this study assessed the suitability of a short-term in situ model to evaluate the anticariogenic potential of ionomeric materials.

METHODS

The study used a 3-phase crossover, double blind design, and in each phase eight volunteers wore palatal appliances containing four enamel blocks restored with one of the following materials: composite resin (CR-Z250) (negative control), a conventional glass ionomer cement (GIC-Ketac-Fil) or a resin-modified GIC (RM-GIC-Vitremer). The restored blocks were covered with a "test plaque" of S. mutans, placed in palatal appliances and a cariogenic challenge was made during 1 min with 20% sucrose solution. After 45 min, test plaque was collected for fluoride (F) analysis. Enamel surface microhardness was previously determined at one side of the restoration and the percentage of surface microhardness change (%SMC) in relation to baseline (other side) was calculated. F concentration in enamel was also evaluated.

RESULTS

Split-plot ANOVA showed a statistically lower %SMC on enamel around the ionomeric materials than around the CR (p<0.05). This result was supported by a statistically higher F concentration in test plaque (P<0.001) and in enamel (P<0.001) restored with the ionomeric materials when compared to the CR.

CONCLUSIONS

The results suggest that the short-term in situ model tested is useful for studying the anticariogenic potential of dental materials that release fluoride.