Reconstruction of a Demineralized Dentin Matrix via Rapid Deposition of CaF2 Nanoparticles In Situ Promotes Dentin Bonding.

Dentin bonding based on a wet-bonding technique is the fundamental technique used daily in clinics for tooth-restoration fixation and clinical treatment of tooth-related diseases. Limited bonding durability led by insufficient adhesive infiltration in the demineralized dentin (DD) matrix is the biggest concern in contemporary adhesive dentistry. This study proposes that the highly hydrated noncollagenous protein (NCP)-formed interfacial microenvironment of the DD matrix is the root cause of this problem. Meanwhile, the endogenous phosphate groups of the NCPs are used as pseudonuclei to rapidly induce the formation of amorphous CaF2 nanoparticles in situ in the interfacial microenvironment. The DD matrix is thus reconstructed into a novel porous structure. It markedly facilitates the infiltration of dentin adhesives in the DD matrix and also endows the DD matrix with anticollapsing capability when water evaporates. Whether using a wet-bonding or air-drying mode, the bonding effectiveness is greatly promoted, with the 12 month bonding strength being about twice that of the corresponding control groups. This suggests that the nanoreinforced DD matrix eliminates the dependence of bonding effectiveness on the moisture status of the DD surface controlled only by experiences of dentists. Consequently, this bonding strategy not only greatly improves bonding durability but also overcomes the technical sensitivity of bonding operations of the total-etched bonding pattern. This exhibits the potential to promote dentin bonding and is of great significance to dentistry.

Growth of mineralized collagen films by oriented calcium fluoride nanocrystal assembly with enhanced cell proliferation.

Bone is a highly calcified tissue with 60 wt% inorganic components. It is made up of mineralized collagen fibrils, where the platelet-like hydroxyapatite nanocrystals deposit within the collagen fibrils in an oriented manner. Inspired by the special structure and biological activity of bone, we realize the intrafibrillar mineralization of collagen films with oriented calcium fluoride nanocrystals in vitro. Amorphous calcium fluoride (ACF) precursors are generated by polyacrylic acid through polymer-induced liquid precursor processes. The precursors are ready to infiltrate and fill the gap zones laterally and then diffuse to occupy the whole space inside the collagen longitudinally. Finally, the fully mineralized collagen fibrils exhibit a single-crystal-like structure after transforming precursors to co-oriented nanocrystals under the influence of arranged collagen molecules. Expanding the collagen mineralization from 1D fibrils to 2D films, the growth of mineralized areas on the films with a reaction-limited behavior is found. The kinetic rate of growth is around 0.2-0.3 µm min-1, which depends on the pH of the solution. Furthermore, the mineralized collagen films exhibit an enhanced ability of cell proliferation over the pure collagen matrices. Understanding the mineralization of artificial collagen-based scaffolds may have broad promising potentials for bone tissue regeneration and repair in the future.

EDX-analysis of fluoride precipitation on human enamel.

One mechanism of action for the anticaries effect of topical fluoridation is through precipitation of CaF2. In this in vitro study energy-dispersive x-ray spectroscopy (EDX) is used as a semiquantitative method to detect enamel fluoride-precipitation under the influence of acidic and neutral pH-value and absence or presence of a salivary pellicle. Crowns of 30 human caries-free third molars were quartered into four specimens and the enamel surface ground flat and polished. Two specimens each were stored in human saliva (120 minutes pellicle formation). Teeth were randomly allocated into 6 treatment groups: NaF_a (experimental acidic sodium fluoride; 12500 ppmF-, pH 4.75); NaF_n (experimental neutral sodium fluoride; 12500 ppmF-, pH 7.0); GB_a (acidic gel base; 0 ppmF-, pH 4.75); GB_n (neutral gel base; 0 ppmF-, pH 7.0); AmF-NaF_a (experimental acidic amine/sodium fluoride; 12500 ppmF-, pH 4.75); EG_a (acidic amine/sodium fluoride; Elmex Geleé, CP-GABA GmbH; 12500 ppmF-, pH 4.75). Each gel was applied for 60 seconds to one specimen with and one specimen without pellicle. Two specimens served as controls (no gel, without/with pellicle). Atomic percent (At%) of O, F, Na, Mg, P, Ca was measured by EDX. ∆At% and Ca/P-ratios were calculated. EDX could semi-quantify superficial enamel fluoride-precipitation. Only specimens treated with acidic fluoride gels showed fluoride-precipitation, a salivary pellicle tended to decrease At%F.

Evaluation of Physical Parameters of Novel Licorice Varnish Versus Fluoride and Combination Varnish: An In-Vitro Study.

OBJECTIVES: The aim of this study was to evaluate the physical properties of locally prepared Licorice varnish (LV), commercially available Fluoride varnish (FV) and a Combination of both Varnishes (CV). MATERIAL AND METHODS: LV was prepared using authenticated licorice roots. Commercially available FV (Bifluorid 12) was used as a positive control and CV was prepared in six different concentrations of both varnishes. Conventional antibacterial activity assessment, employing disc diffusion and broth dilution methods, was inconclusive. Therefore a novel assessment method was used, whereby the varnish was directly added to a mixture of Brain Heart Infusion broth with Streptococcus mutans and incubated. Physical parameters such as pH, rate of evaporation, viscosity, film forming ability, and cost incurred for preparation were assessed and compared. RESULTS: FV, LV and CV (except the combination of LV 80% + FV 20%) showed antibacterial activity against Streptococcus mutans. All three varnishes formed films on the tooth surface as confirmed by Scanning Electron Microscopy. Mean pH was in the range of 4-4.5, viscosity 48-52 centipoise (cP), rate of evaporation was 150-160 seconds. They were comparable to each other in the physical parameters tested, except for the shelf life of LV. CONCLUSION: All three varnishes showed antibacterial activity against Streptococcus mutans which was established using an innovative method of antibacterial activity assessment. LV was most economical of all but had a shorter shelf life. The results of this study need to be evaluated through an in vivo study.

Effect of calcium fluoride on the activity of dentin matrix-bound enzymes.

OBJECTIVE: Matrix metalloproteinases (MMPs) and cysteine cathepsins (CCs) are two distinct enzymatic pathways responsible for the degradation of collagen fibrils in demineralized dentin. NaF and KF have been shown to inhibit salivary MMP-2, -9 and CCs. This study investigated the inhibitory effect of calcium fluoride (CaF2) on the dentin matrix-bound MMPs and CCs. DESIGN: Phosphoric acid (10%)-demineralized dentin beams (1 × 2×6 mm) were incubated at 37 °C in an 1 ml of artificial saliva (AS, control), or AS with 6, 12, 24, 48, 120. 179 and 238 mM F containing CaF2 (n = 10/group) for 1, 7 and 21 days. All groups were further incubated in AS only for 6 months. Total MMP activity, dry mass loss, CTX and hydroxyproline (HYP) analyses were performed after each incubation. The beams were examined under scanning electron microscopy (SEM). MMP-2 and MMP-9 activities were screened with gelatin zymography. Data were analyzed by using ANOVA and Tukey HSD tests (p = .05). RESULTS: The total MMP activity was similar for all groups after 21 days and 6 months. After 21 days, the cumulative mass loss and CTX levels were lower compared to control for the CaF2 ≥48 and CaF2≥120 mM, respectively (p < .05). After 6 months, no significant difference was detected in the dry mass loss and CTX compared to the control (p > .05), whereas HYP level was higher with F 24 and 238 mM groups. CaF2-like minerals were observed on the beams under SEM. There was no gelatinase inhibition in zymography. CONCLUSION: CaF2 does not prevent the degradation of demineralized dentin matrices due to the catalytic activity of MMPs and CCs.

Remineralizing effect of a fluoridated gel containing sodium hexametaphosphate: An in vitro study.

OBJECTIVES: To evaluate in vitro the effect of neutral pH topical gels with reduced fluoride concentration (F), supplemented or not with sodium hexametaphosphate (HMP) on the remineralization of dental enamel, using a pH-cycling model. Materials and methods Bovine enamel blocks with caries-like lesions were randomly treated with five gels (n = 24/group): without F/HMP (Placebo); 4500 ppm F (4500F), 4500F plus 9% HMP (4500F + HMP); 9000 ppm F (9000F); and 12,300 ppm F (Acid gel). After pH-cycling, the percentage of surface hardness recovery (%SHR), integrated loss of subsurface hardness (ΔKHN), and concentrations of loosely- (CaF2) and firmly-bound (FA) fluoride formed and retained in/on enamel were determined. The results were analyzed by ANOVA followed by the Student-Newman-Keuls test (p < 0.001). RESULTS: The 4500F + HMP gel promoted the highest %SHR among all groups; the lowest ΔKHN was achieved by 4500F + HMP and Acid gel, without significant differences between these. The Acid gel group presented the highest CaF2 and FA formed and retained on/in enamel (p < 0.001). CONCLUSION: Based on the present results, the addition of 9% sodium hexametaphosphate to a gel with reduced fluoride concentration (4500F) was able to significantly enhance the remineralization of artificial carious lesions in vitro when compared to 4500F, reaching protective levels similar to an acidic formulation with ∼3-fold higher fluoride concentration.

Assessment of Enamel Surface Microhardness with different Fluoride Varnishes-An In Vitro Study.

AIM: This study aimed to assess the microhardness of the enamel surface after fluoride varnish application. MATERIALS AND METHODS: Thymol of 0.1% in distilled water was used to store the collected healthy sixty teeth. The samples were divided into three groups randomly as per the different applica -tion of fluoride varnish. Group A: Fluor protector varnish (FIV) application, group B: Duraphat varnish application and group C: Bifluorid 10 varnish application. The present study followed the pH cycling protocol. Microhardness tester was used to test the microhardness of enamel surface and was expressed as micro-hardness measurements of Vickers hardness number (VHN) which was performed at baseline, on the 3rd day andon 7th day. RESULTS: At baseline, group A samples mean SMH value was 230.64 ± 12.32 which was slightly more than group B with 229.45 ± 10.22 and group C with 230.10 ± 11.45. There was no significant difference showed with the analysis of variance between the groups. On the 3rd day, there was a slight increase in the mean SMH in group A with 235.39 ± 6.44 and no significant difference between the groups was seen statistically. On the 7th day, the group A showed high SMH value of 262.20 ± 4.89 compared to other groups which didn't show a significantly high statistical difference. CONCLUSION: On conclusion, post-application of fluorprotector varnish showed higher enamel surface microhardness compared to Duraphat and Bifluorid 10 varnishes. CLINICAL SIGNIFICANCE: In young children, fluoride varnishes are effectively used as a noninvasive, anti-caries agent in the treatment of initial caries. Therefore, in routine dental practice, the knowledge about different fluoride varnishes is of importance.

In situ effect of the combination of fluoridated toothpaste and fluoridated gel containing sodium trimetaphosphate on enamel demineralization.

OBJECTIVE: This in situ study evaluated the effect of the association of low-F (4500µg F/g) gel containing TMP and FT (1100µg F/g) on enamel demineralization. METHODS: This crossover and double-blind study consisted of five phases of seven days each. Volunteers (n=12) wore palatal appliances containing four enamel blocks. The cariogenic challenge was performed with 30% sucrose solution (six times/day). Treatments were: placebo toothpaste (PT, no fluoride/TMP); 1100µg F/g toothpaste (FT); FT+4500µg F/g+5%TMP gel (FT+TMP gel); FT+9000µg F/g gel (FT+9000 gel) and FT+12,300µg F/g (FT+Acid gel). After topical application of treatments for one min, two blocks were removed for analysis of loosely bound fluoride (CaF2), calcium (Ca), phosphorus (P) and firmly bound fluoride (FA) formed in enamel. After the seven-day experimental periods, the percentage of surface hardness loss (%SH), integrated subsurface hardness loss (ΔKHN), CaF2, Ca, P and FA retained were determined. Moreover, the biofilms formed on the blocks were analyzed for F, Ca, P and insoluble extracellular polysaccharide (EPS) concentrations. RESULTS: FT+TMP gel promoted the lowest%SH and ΔKHN (p<0.001). The highest concentration of CaF2 formed was observed for the FT+Acid gel (p<0.001), followed by FT+9000 gel > FT+TMP gel > FT > PT. CaF2 retained on the blocks was reduced across all groups (p<0.001). Similar values were observed for the Ca/P/F and EPS in enamel and biofilm for all fluoride groups. CONCLUSION: The association of FT+TMP gel significantly reduced enamel demineralization in situ. CLINICAL SIGNIFICANCE: The association of treatments may be an alternative for patients with high caries risk.

Hydroxyapatite decreases cytotoxicity of a glass ionomer cement by calcium fluoride uptake in vitro.

BACKGROUND: Glass ionomer cements (GICs) are widely used in dentistry because of their remineralizing and cariostatic potential induced by fluoride. In vitro studies have reported cell toxicity triggered by GICs; however, the influence of hydroxyapatite (HAp) must be considered. The aim of this study was to evaluate the effect of HAp in decreasing the cytotoxicity of the GIC 3M Vitrebond in vitro. METHODS: Samples of 3M Vitrebond (powder, liquid and light-cured) were incubated in Dulbecco's modified Eagle's medium-Ham's F12 (DMEM-F12) for 24 hours at 37°C. Subsequently, the light-cured medium was treated with 100 mg/mL of HAp overnight. Toxicity of conditioned media diluted 1:2, 1:4, 1:8 and 1:20 was analyzed on human gingival fibroblasts (HGFs) using light microscopy and the fluorometric microculture cytotoxicity assay. The amounts of calcium fluoride (CaF2) were determined by the alizarin red S method. RESULTS: The exposure of HGFs to light-cured induced cell death and morphological changes such as chromatin condensation, pyknotic nuclei and cytoplasmic modifications. Exposure to light-cured treated with HAp, significantly increased cell viability leading to mostly spindle-shaped cells (p<0.001). The concentration of CaF2 released by the light-cured was 200 ppm, although, in the light-cured/HAp conditioned medium, this quantity decreased to 88 ppm (p<0.01). CONCLUSIONS: These data suggest that HAp plays a protective role, decreasing the cytotoxic effect of 3M Vitrebond induced by CaF2.

CO2 laser irradiation enhances CaF2 formation and inhibits lesion progression on demineralized dental enamel-in vitro study.

This study evaluated if Carbon dioxide (CO2) (λ 10.6 µm) laser irradiation combined with acidulated phosphate fluoride gel application (APF gel) enhances "CaF2" uptake by demineralized enamel specimens (DES) and inhibits enamel lesion progression. Thus, two studies were conducted and DES were subjected to APF gel combined or not with CO2 laser irradiation (11.3 or 20.0 J/cm(2), 0.4 or 0.7 W) performed before, during, or after APF gel application. In study 1, 165 DES were allocated to 11 groups. Fluoride as "CaF2 like material" formed on enamel was determined in 100 DES (n = 10/group), and the surface morphologies of 50 specimens were evaluated by scanning electron microscopy (SEM) before and after "CaF2" extraction. In study 2, 165 DES (11 groups, n = 15), subjected to the same treatments as in study 1, were further subjected to a pH-cycling model to simulate a high cariogenic challenge. The progression of demineralization in DES was evaluated by cross-sectional microhardness and polarized light microscopy analyses. Laser at 11.3 J/cm(2) applied during APF gel application increased "CaF2" uptake on enamel surface. Laser irradiation and APF gel alone arrested the lesion progression compared with the control (p < 0.05). Areas of melting, fusion, and cracks were observed. CO2 laser irradiation, combined with a single APF application enhanced "CaF2" uptake on enamel surface and a synergistic effect was found. However, regarding the inhibition of caries lesion progression, no synergistic effect could be demonstrated. In conclusion, the results have shown that irradiation with specific laser parameters significantly enhanced CaF2 uptake by demineralized enamel and inhibited lesion progression.

Effect of ZrO(2) additions on the crystallization, mechanical and biological properties of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics.

A series of ZrO(2) doped MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) bioactive glass-ceramics were obtained by sintering method. The crystallization behavior, phase composition, morphology and structure of glass-ceramics were characterized. The bending strength, elastic modulus, fracture toughness, micro-hardness and thermal expansion coefficient (TEC) of glass-ceramics were investigated. The in vitro bioactivity and cytotoxicity tests were used to evaluate the bioactivity and biocompatibility of glass-ceramics. The sedimentation mechanism and growth process of apatites on sample surface were discussed. The results showed that the mainly crystalline phases of glass-ceramics were Ca(5)(PO4)3F (fluorapatite) and ß-CaSiO(3). (ß-wollastonite). m-ZrO(2) (monoclinic zirconia) declined the crystallization temperatures of glasses. t-ZrO(2) (tetragonal zirconia) increased the crystallization temperature of Ca(5)(PO4)(3)F and declined the crystallization temperature of ß-CaSiO(3). t-ZrO(2) greatly increased the fracture toughness, bending strength and micro-hardness of glass-ceramics. The nanometer apatites were induced on the surface of glass-ceramic after soaking 28 days in SBF (simulated body fluid), indicating the glass-ceramic has good bioactivity. The in vitro cytotoxicity test demonstrated the glass-ceramic has no toxicity to cell.

Evaluation of Streptococcus mutans adhesion to fluoride varnishes and subsequent change in biofilm accumulation and acidogenicity.

OBJECTIVES: The aim of this study was to evaluate Streptococcus mutans adhesion to fluoride varnishes and subsequent change in biofilm accumulation and acidogenicity. METHODS: After producing fluoride varnish-coated hydroxyapatite discs using Fluor Protector (FP), Bifluorid 12 (BIF), Cavity Shield (CASH), or Flor-Opal Varnish White (FO), S. mutans biofilms were formed on the discs. To assess S. mutans adhesion to the discs, 4-h-old biofilms were analysed. To investigate the change in biofilm accumulation during subsequent biofilm formation, the biomass, colony forming units (CFU), and water-insoluble extracellular polysaccharides (EP) of 46-, 70-, and 94-h-old biofilms were analysed. To investigate the change in acidogenicity, pH values of the culture medium were determined during the experimental period. The amount of fluoride in the culture medium was also determined during the experimental period. RESULTS: BIF, CASH, and FO affected S. mutans adhesion (67-98% reduction) and subsequent biofilm accumulation in 46-, 70-, and 94-h-old biofilms. However, the reducing effect of the fluoride varnishes on the biomass, CFU count, water-insoluble EP amount, and acid production rate of the biofilms decreased as the biofilm age increased. These results may be related to the fluoride-release pattern of the fluoride varnishes. Of the fluoride varnishes tested, FO showed the highest reducing effect against the bacterial adhesion and subsequent biofilm accumulation. CONCLUSIONS: Our findings suggest that if the results of these experiments are extrapolable to the in vivo situation, then reduced clinical benefit of using fluoride varnishes may occur with time. CLINICAL SIGNIFICANCE: Fluoride varnish application can affect cariogenic biofilm formation but the anti-biofilm activity may be reduced with time.

Acidulated phosphate fluoride application changes the protein composition of human acquired enamel pellicle.

We evaluated, by proteomic analysis, whether the chemical changes provoked on enamel by acidulated phosphate fluoride (APF) application alter the protein composition of acquired enamel pellicle. Enamel slabs, pretreated with distilled water (negative control), phosphoric acid (active control) or APF solution, were immersed in human saliva for pellicle formation. The adsorbed proteins were extracted and analyzed by liquid chromatography-mass spectrometry/mass spectrometry. Fifty-six proteins were identified, 12 exclusive to APF and 11 to phosphoric acid. APF decreased the concentration of histatin-1, but increased the concentration of S100-A9, which is confirmed by immunoblotting. The findings suggest that APF application changes the acquired enamel pellicle composition.

The evaluation of dentinal tubule occlusion by desensitizing agents: a real-time measurement of dentinal fluid flow rate and scanning electron microscopy.

The aims of this study were to examine changes in dentinal fluid flow (DFF) during the application of a desensitizing agent and to compare the permeability reduction levels among different types of desensitizing agents. A cervical cavity was prepared for the exposure of cervical dentin on an extracted human premolar connected to a subnanoliter fluid flow measuring device under 20 cm of water pressure. The cavity was acid-etched with 32% phosphoric acid to make dentin highly permeable. The different types of desensitizing agents that were applied on the cavity were Seal&Protect as the light-curing adhesive type, SuperSeal and BisBlock as oxalate types, Gluma Desensitizer as the protein-precipitation type, and Bi-Fluoride 12 as the fluoride type. DFF was measured from the time before the application of the desensitizing agent throughout the application procedure to five minutes after the application. The characteristics of dentinal tubule occlusion of each desensitizing agent were examined by scanning electron microscopy. The DFF rate after each desensitizing agent application was significantly reduced when compared to the initial DFF rate before application for all of the desensitizing agents (p<0.05). Seal&Protect showed a greater reduction in the DFF rate when compared to Gluma Desensitizer and Bi-Fluoride 12 (p<0.05). SuperSeal and BisBlock exhibited a greater reduction in DFF rate when compared to Bi-Fluoride 12 (p<0.05). The dentin hypersensitivity treatment effects of the employed desensitizing agents in this study were confirmed through real-time measurements of DFF changes. The light-curing adhesive and oxalate types showed greater reduction in the DFF rate than did the protein-precipitation and fluoride types.

Antibacterial and physical properties of calcium-phosphate and calcium-fluoride nanocomposites with chlorhexidine.

OBJECTIVES: Previous studies have developed calcium phosphate and fluoride releasing composites. Other studies have incorporated chlorhexidine (CHX) particles into dental composites. However, CHX has not been incorporated in calcium phosphate and fluoride composites. The objectives of this study were to develop nanocomposites containing amorphous calcium phosphate (ACP) or calcium fluoride (CaF(2)) nanoparticles and CHX particles, and investigate Streptococcus mutans biofilm formation and lactic acid production for the first time. METHODS: Chlorhexidine was frozen via liquid nitrogen and ground to obtain a particle size of 0.62 µm. Four nanocomposites were fabricated with fillers of: nano ACP; nano ACP+10% CHX; nano CaF(2); nano CaF(2)+10% CHX. Three commercial materials were tested as controls: a resin-modified glass ionomer, and two composites. S. mutans live/dead assay, colony-forming unit (CFU) counts, biofilm metabolic activity, and lactic acid were measured. RESULTS: Adding CHX fillers to ACP and CaF(2) nanocomposites greatly increased their antimicrobial capability. ACP and CaF(2) nanocomposites with CHX that were inoculated with S. mutans had a growth medium pH>6.5 after 3 d, while the control commercial composites had a cariogenic pH of 4.2. Nanocomposites with CHX reduced the biofilm metabolic activity by 10-20 folds and reduced the acid production, compared to the controls. CFU on nanocomposites with CHX were three orders of magnitude less than that on commercial composite. Mechanical properties of nanocomposites with CHX matched a commercial composite without fluoride. SIGNIFICANCE: The novel calcium phosphate and fluoride nanocomposites could be rendered antibacterial with CHX to greatly reduce biofilm formation, acid production, CFU and metabolic activity. The antimicrobial and remineralizing nanocomposites with good mechanical properties may be promising for a wide range of tooth restorations with anti-caries capabilities.

Long-term protective effect of surface sealants against erosive wear by intrinsic and extrinsic acids.

OBJECTIVE: To test sealants to prevent erosive tooth wear caused by extrinsic and intrinsic acids under long-term exposition. METHODS: 144 bovine enamel samples were randomly allocated to twelve groups (1-12). Samples of groups 1, 5 and 9 remained unsealed (positive controls), 2, 6 and 10 were sealed with Silicon Seal Nano Mix and 3, 7 and 11 with Seal&Protect. Groups 4, 8 and 12 were sealed with flowable composite (negative controls). Groups 1-4 were immersed in artificial saliva, 5-8 in hydrochloric acid and groups 9-12 in citric acid for 28 days, respectively. After 1, 2, 4, 7, 11, 14, 21 and 28 days, solutions were renewed and enamel wear was quantified by assignation of (32)P in the solutions. RESULTS: In all immersion solutions, lowest mineral loss was observed for the negative controls whilst highest loss was observed for unsealed positive controls. In artificial saliva and citric acid, the loss from samples sealed with Seal&Protect was not significantly different compared with negative controls whilst loss in groups sealed with Silicon Seal Nano Mix was significantly higher. In hydrochloric acid, loss from samples sealed with Seal&Protect was not different compared with that of negative controls up to 4 days. Except day 1, the mineral loss in the Seal&Protect group was significantly lower compared with that of the Silicon Seal Nano Mix group. CONCLUSION: The tested resin based surface sealant is able to significantly reduce the erosive demineralisation of enamel caused by hydrochloric and citric acid even under long-term exposition.

Clinical evaluation of demineralization and remineralization of intact root surface lesions in the clinic by a quantitative light-induced fluorescence system.

Detection of demineralization of root surface caries is an important issue since preventive approaches prolong tooth life. Quantitative light-induced fluorescence (QLF) has been shown to be useful for the laboratory assessment of demineralization of root surfaces. The aim of this study was to determine the demineralization and remineralization of root surface intact and cavitated caries lesions using a QLF system as a nondestructive in vivo method. Noncavitated and demineralized root surface lesions were detected and scored using the QLF system. Oral hygiene education was given and periodontal cleaning was completed before the remineralization treatment. After obtaining baseline QLF data, the patients were informed about the remineralization treatment. Fluoride varnish was applied to the carious lesions at the baseline visit, and the patients were then reviewed after 1, 2, 3 and 4 weeks, with QLF assessment and fluoride varnish application repeated at each review. Repeated-measures ANOVA (α = 0.05) showed significant differences between ΔQ values at each visit (p < 0.001); ΔQ showed marked decreases at all the cut-off values (15, 20, 25, 30). The changes in ΔQ were not affected by the cut-off value. The ΔQ values of QLF showed differences at all visits. The QLF system was able to detect early root surface caries lesions in vivo. Bifluoride 12 varnish improved mineral levels as shown by the QLF system. The treatment response to chemicals of intact noncavitated root surface carious lesions could be followed nondestructively in the clinic using QLF to quantify remineralization at recall visits. Teeth with root surface caries can be kept by controlling their remineralization.

Fluoride and chlorhexidine release from filled resins.

Resin-based materials that release either fluoride or chlorhexidine have been formulated for inhibiting caries activity. It is not known if the two agents, when incorporated into one material, would interact and affect their release potential. We hypothesized that the ratio of fluoride to chlorhexidine incorporated into a resin, and the pH of the storage medium, will affect their releases from the material. The material investigated contained 23 wt% of filler, and the ratios of calcium fluoride to chlorhexidine diacetate were 8/2, 5/5, and 2/8. The release was conducted in pH 4, 5, and 6 acetate buffers. The results showed that release of either agent increased as the pH of the medium decreased. The presence of fluoride salt substantially reduced the chlorhexidine release, while the presence of a specific quantity of chlorhexidine significantly increased fluoride release. This interaction can be utilized to optimize the release of either agent for therapeutic purposes.

Preparation and properties of nano-sized calcium fluoride for dental applications.

OBJECTIVES: The aim of the present study was to prepare nano-sized calcium fluoride (CaF(2)) that could be used as a labile F reservoir for more effective F regimens and as an agent for use in the reduction of dentin permeability. METHODS: Nano-sized CaF(2) powders were prepared using a spray-drying system with a two-liquid nozzle. The properties of the nano-CaF(2) were studied and the effectiveness of a fluoride (F) rinse with nano-CaF(2) as the F source was evaluated. The thermodynamic solubility product of the nano-CaF(2) solution was determined by equilibrating the nanosample in solutions presaturated with respect to macro-CaF(2). Reactivity of the nano-CaF(2) was assessed by its reaction with dicalcium phosphate dehydrate (DCPD). F deposition by 13.2 mmol/L F rinse with the nano-CaF(2) as the F source was determined using a previously published in vitro model. RESULTS: X-ray diffraction (XRD) analysis showed pattern of low crystalline CaF(2). BET measurements showed that the nano-CaF(2) had a surface area of 46.3m(2)/g, corresponding to a particle size of 41nm. Transmission electron microscopy (TEM) examinations indicated that the nano-CaF(2) contained clusters comprising particles of (10-15) nm in size. The nano-CaF(2) displayed much higher solubility and reactivity than its macro-counterpart. The CaF(2) ion activity product (IAP) of the solution in equilibrium with the nano-CaF(2) was (1.52+/-0.05)x10(-10), which was nearly four times greater than the K(sp) (3.9 x 10(-11)) for CaF(2). The reaction of DCPD with nano-CaF(2) resulted in more F-containing apatitic materials compared to the reaction with macro-CaF(2). The F deposition by the nano-CaF(2) rinse was (2.2+/-0.3)mug/cm(2) (n=5), which was significantly (p<0.001) greater than that ((0.31+/-0.06)mug/cm(2)) produced by the NaF solution. SIGNIFICANCE: The nano-CaF(2) can be used as an effective anticaries agent in increasing the labile F concentration in oral fluid and thus enhance the tooth remineralization. It can also be very useful in the treatment for the reduction of dentin permeability.

Smear layer and surface state affect dentin fluoride uptake.

OBJECTIVES: Polishing generates a smear layer (SL) on in vitro dentin samples that may influence fluoride uptake. We tested two hypotheses: SL increases fluoride uptake in superficial dentin (H1) and decreases fluoride uptake in deeper layers (H2) irrespectively of the amount of fluoride administered. METHODS: Polished bovine dentin with SL present and removed by four methods (5% tannic acid, 20s [TA]; 17% EDTA, 120 s; 38% phosphoric acid, 60s [PA]; and 10s air polishing) was fluoridated with 1200 or 12000 ppm F (NaF) solution (pH 4.0). RESULTS: Scanning electron microscopy (SEM) revealed that aggressiveness of SL removal varied by method from leaving SL patches behind (TA) to collagen exposure (PA). SL increased KOH-soluble and structurally bound fluoride uptake into superficial and deeper layers compared to SL free surfaces (except PA) following 1200 ppm, but not 12000 ppm fluoridation. CONCLUSION: Presence of SL and surface conditions influence dentin fluoride uptake depending on fluoride concentration administered.