Neutralizing effect by resin-based materials containing silane-coated glass fillers.

The aim of this study was to evaluate the fluoride release, neutralizing ability and inhibitory effect on secondary caries of resin-based materials containing a silane-coated glass filler. Resin-based materials containing fluoro-boro-alumino-silicate glass coated by 3-methacryloxypropyltrimethoxysilane or 3-aminopropyltrimethoxysilane were used and resin material containing glass filler without coating was used as a control. The fluoride release and pH value after immersion were measured for 10 weeks. The inhibitory effect was also evaluated. During the initial period, the material with 3-aminopropyltrimethoxysilane gave the greater amount of fluoride release and produced a higher pH value compared with the other materials. However, the neutralizing ability of the material with 3-aminopropyltrimethoxysilane filler became weaker with ageing of the specimens. The mean depth of outer lesions was similar among the three materials. Within the limitations of this study, secondary caries around restorations could not be inhibited even for products showing high fluoride releasing and neutralizing ability.

Fluoride release for restorative materials and its effect on biofilm formation in natural saliva.

This study investigated the influence of natural saliva of varying pH on surface biofilm formation of restorative materials and how this influenced fluoride release. Columnar specimens of glass ionomer cement (GIC), resin modified glass ionomer cement (RMGIC), compomer, giomer and composite, were prepared, matured for 24 h at 37 degrees C and 100% humidity, lapped and then placed in natural stimulated saliva with a pH of 3.8 or 7.1. Fluoride release was determined daily using an ion-selective electrode. The surfaces of selected specimens were observed using Confocal Laser Scanning Microscopy in conjunction with a fluorescent dye. The surface biofilm formation and bacterial growth was most dominant under neutral conditions and on the surfaces of GICs compared with other materials. GICs released significantly higher amounts of fluoride than other materials. The results suggest that the increased fluoride release of GICs did not reduce the amount of bacterial growth and biofilm formation on the surfaces of these materials when stored in natural saliva.

Effect of a desensitizing agent containing glutaraldehyde and HEMA on bond strength to Er:YAG laser-irradiated dentine.

OBJECTIVES: The aim of this study was to investigate whether a desensitizing agent (GLUMA Desensitizer) containing glutaraldehyde and HEMA improved the bond strength and bonding durability of a self-etching primer adhesive to Er:YAG-irradiated dentine. METHOD: Dentine of 120 human molars was exposed by wet grinding on SiC paper for bond strength testing. Thirty specimens each were allocated to the following treatment groups: (1) control; (2) Er:YAG laser irradiation; (3) Er:YAG laser irradiation followed by application of GLUMA Desensitizer; (4) Er:YAG laser irradiation followed by application of GLUMA Desensitizer and 10s rinsing with water. Composite cylinders were bonded to the dentine surfaces with a self-etching priming adhesive system. Tensile bond strengths (TBS) of 10 specimens of each treatment group were measured after 24-h water storage, 6 months water storage and 12 months water storage, respectively, and the failure modes were analyzed. TBS data were statistically treated by two-way ANOVA and Fisher's PLSD test at a significance level of p<0.05. RESULTS: TBSs for the GLUMA-non rinse and GLUMA-rinse groups were significantly higher than for the laser group at 24 h and 12 months. Specimens from the Er:YAG-irradiated dentine group had significantly lower bond strengths than the control group at each storage time. All control specimens showed cohesive fractures in resin close to the bonding interface whereas the Er:YAG laser-irradiated groups showed both dentine cohesive, resin cohesive and dentine-resin mixed failures. CONCLUSION: Application of GLUMA Desensitizer to Er:YAG-irradiated dentine increases the bond strength and durability of the self-etching priming adhesive used.

Effect of fluoride-releasing liner on demineralized dentin.

OBJECTIVE: The aim of this study was to evaluate the remineralization of residual demineralized dentin underneath restorations by fluoride-releasing liners in vitro. METHOD AND MATERIALS: Two glass-ionomer cement liners, Lining Cement (GC) and RK-141A (GC), and two light-cured resin liners with and without 5 wt% NaF were used in this study. The resin liners were made by mixing TEGDMA and bis-GMA. Class 5 cavities were prepared on extracted human premolars. Demineralized dentin was promoted by using a bacterial caries induction system at the cavity floor. Cavities were restored with a resin composite following application of each liner. Specimens were then stored for 4 weeks at 37 degrees C and 100% humidity. After storage, the specimens were cut through the restorations, and axial sections of about 80-microm thickness were prepared. Contact microradiographs were taken, and the radiopacity of the demineralized dentin layer underneath the liner was analyzed. RESULTS: The ratios of radiopacity of demineralized dentin under the fluoride-releasing liners were significantly higher than those under the resin liner without fluoride release. Although the amounts of fluoride release from the glass-ionomer cement liners were lower than that from the resin liner with fluoride release, there were no significant differences in the ratios of radiopacity in demineralized dentin layers among the 3 liners with fluoride release. CONCLUSION: Although the fluoride released from liners can enhance remineralization of demineralized dentin, the amount of fluoride release does not affect the ratio of radiopacity in the remineralized dentin.

Fluoride release and neutralizing effect by resin-based materials.

This study evaluated the fluoride-releasing and neutralizing abilities of resin-based materials containing fluoride in water and aqueous lactic acid. Two composites, containing a low-solubility fluoride component (Heliomolar) and a fluoroalumino-silicate glass (UniFil S), and two giomers, containing surface reaction type prereacted glass-ionomer filler (Beautifil) and full reaction type glass-ionomer filler (Reactmer paste), were used. Resin-modified glass-ionomer cement (Fuji II LC) was used as a control. The fluoride release and pH value in storage medium, after immersion in each material, was measured for 10 weeks. For UniFil S and Beautifil, the amount of fluoride released in acid solution markedly increased compared to storage in water (p<0.05). Although all materials, except Heliomolar, neutralized the storage media, the neutralizing ability of these resin-based materials in acid solution sharply decreased with aging of the specimens, except for Fuji II LC. These results suggest that the nature of fluoride incorporated into resin-based materials affect the fluoride-releasing and neutralizing ability of materials in water and aqueous lactic acid.

Fluoride release from aged resin composites containing fluoridated glass filler.

OBJECTIVES: The aim of this study was to evaluate the fluoride release from aged resin composites containing different types of fluoridated glass filler into both deionized distilled water and lactic acid solution. METHODS: Three resin composites, UniFil S (containing fluoro-alumino-silicate glass filler), Reactmer (containing pre-reacted glass-ionomer filler) and Beautifil (containing both types of fillers) were used. A conventional glass-ionomer cement, Ketac-Fil, was used as a control. Five disk specimens of each material were prepared and aged in water for 10 weeks. After aging, specimens were immersed in deionized distilled water for a further 6 days and then in aqueous lactic acid (pH 4.0) for 2 days. This process was repeated twice more and the specimens were subsequently immersed in water for a further 12 days. Fluoride release was measured every 2 days throughout the post-aging period. RESULTS: The amount of fluoride release for aged UniFil S and Beautifil markedly increased in acid solution compared with water storage. The difference was not so great for aged Reactmer and Ketac-Fil. UniFil S and Beautifil gave significantly greater fluoride release in water following immersion in acid solution (p<0.05, two-way ANOVA and Scheffe's test), but Reactmer and Ketac-Fil showed no such increase in fluoride release after acid immersion. SIGNIFICANCE: These results suggested that the nature of the fluoridated glass filler within a resin composite and the way in which the material interacts with an acidic environment affected the amount of fluoride released.

Effect of two-step adhesive systems on inhibition of secondary caries around fluoride-releasing resin composite restorations in root dentine.

OBJECTIVE: The purpose of this study was to investigate the effect of two-step adhesive systems on secondary caries inhibition around fluoride-releasing materials in vitro. METHODS: Two self-etching primer systems, Clearfil SE Bond (SE) and UniFil Bond (UB), and two one-bottle systems with a total-etch wet-bonding technique, Single Bond (SB) and One-Step (OS), were used prior to placement of resin composites either with (Reactmer) or without (Z100) fluoride release. Class V cavities prepared in extracted human premolars were restored with various combinations of materials: Reactmer/SE, Reactmer/UB, Reactmer/SB, Reactmer/OS, Z100/SE, Z100/UB, Z100/SB and Z100/OS. After storage for 14 days, the restored teeth were incubated in bacterial medium containing sucrose with Streptoccus mutans for 2 weeks. Water sorption and desorption of the adhesives and fluoride release from the resins either coated with adhesive or uncoated were also determined. RESULTS: The one-bottle groups showed higher water sorption and desorption than the self-etching primer groups. Although fluoride release from the Reactmer specimens was suppressed by the adhesive coating, the one-bottle groups allowed significantly higher fluoride release than the self-etching primer groups. On microradiographs, the radio-opaque layers adjacent to the Reactmer restorations were thick and clear, while the layers adjacent to the Z100 restorations were thin and unclear. For the Reactmer restorations, the radio-opaque layers associated with the one-bottle groups were significantly thicker than for the self-etching primer groups. CONCLUSIONS: These results indicated that the use of one-bottle wet-bonding systems for bonding of fluoride-releasing resin composites to dentine may contribute to inhibit secondary caries compared to self-etching primer systems.

Fluoride release and recharge in giomer, compomer and resin composite.

OBJECTIVES: The aim of this study was to examine the fluoride recharging and releasing abilities of resin-based materials containing fluoridated glass filler to determine whether the extent of the glass-ionomer matrix of the material affects these properties. METHODS: Three materials having a different proportion of the hydrogel matrix surrounding the glass filler, namely: Reactmer paste, Dyract AP and Xeno CF, were used for this study. Five disk specimens of each material were placed into distilled/deionized water and the fluoride release measured during 38 days. For fluoride recharge the disks were exposed to 250 ppm F solution for 1 h and the pre- and post-recharge fluoride release were determined using an ion-selective electrode (total fluoride ions) and ion chromatography (free fluoride ions). RESULTS: The amounts of total and free fluoride release from each material at the initial period in descending order were Reactmer paste > Dyract AP > Xeno CF (p < 0.05 ANOVA and Scheffe's test). After fluoride recharge, Reactmer paste showed a greater amount of fluoride release than the other materials. Dyract AP and Xeno CF showed a similar total level of fluoride release after recharging. For Xeno CF the amount of total fluoride released after recharging was significantly greater than that of free fluoride, but there was no significant difference between total and free fluoride released after recharging for Dyract AP (p = 0.05 paired t-test). SIGNIFICANCE: These results suggested that the extent of the glass-ionomer matrix of the glass filler played an important role for fluoride-releasing and recharging abilities of the resin-based materials.

Bonding to root caries by a self-etching adhesive system containing MDPB.

PURPOSE: To evaluate the bonding of an experimental antibacterial fluoride-releasing adhesive system (ABF) to normal and carious dentin in human teeth with Class V root caries. METHODS: Mesiodistal sectioning removed the buccal enamel, superficial dentin and much of the carious dentin in 21 extracted human bicuspids with root surface caries. The surfaces of normal coronal and root dentin, and caries-affected and caries-infected dentin were ground with wet 600-grit SiC paper to create a standardized smear layer. Tooth surfaces were treated with the ABF according to manufacturer's instructions, and then covered with excess resin composite. After immersion in 37 degrees C water for 24 hours, the restored teeth were horizontally sectioned into serial slabs that were trimmed into hourglass shapes to isolate the bonded area to the test substrates, and then their bond strengths were measured by the microtensile bond test, and the interfaces examined by SEM and TEM. The bond strengths were statistically compared with ANOVA and Fisher's PLSD (P < 0.05). RESULTS: The bond strengths of ABF to caries-affected and caries-infected dentin were significantly lower than those to normal coronal and root dentin. SEM micrographs revealed that the hybrid layers in caries-affected and caries-infected dentin were more porous compared to the hybrid layer in normal coronal and root dentin. TEM micrographs showed that bacteria that had invaded the dentin were embedded in this adhesive monomer in caries-infected dentin. CLINICAL SIGNIFICANCE: Although the bond strength of ABF adhesive system to root carious dentin is lower than that of normal dentin, the antibacterial and fluoride-releasing properties of ABF may contribute to prevent caries progression and inhibit secondary caries.

Determination of fluoride ions released from resin-based dental materials using ion-selective electrode and ion chromatograph.

OBJECTIVES: The aim of this study was to investigate the quantities of total and free fluoride ions released from four resin-based composites containing fluoride (Heliomolar (HE), UniFil S (UF), Beautifil (BE) and Reactmer paste (RP)) and one glass ionomer cement (Ketac-Fil Plus Aplicap (KF)). METHODS: Five disk specimens of each material were prepared and the fluoride release was measured at 1, 2, 4, 7, 14, 21 and 28 days. The amounts of total and free fluoride ions released from materials were measured by using an ion-selective electrode (ISE) and ion chromatography (IC). Data were statistically analyzed using a t-test at a significant level of 0.05. RESULTS: For HE, fluoride release is undetectable using the ISE but was detected by the IC method. There were no significant differences in the free and total fluoride ions released from UF and BE (p>0.05). For RP, the free fluoride ions were significantly lower than the total fluoride ions after 4 days (p<0.05). KF showed significant difference between total and free fluoride ions at 7 and 28 days (p<0.05). CONCLUSIONS: The nature of the fluoride incorporated into dental materials affected the amounts of free and total fluoride ions released from materials.

Calbindin D-28k distribution in odontoblasts underneath tertiary dentine in human carious teeth.

OBJECTIVE: The aim of this study was to examine the calbindin D-28k immunoreactivity in carious teeth to know whether this protein may have a function in tertiary dentine formation. METHODS: Human extracted teeth with or without carious lesions were immersion-fixed with Zamboni fixative, demineralized in 4.13% EDTA solution (pH 7.4), frozen-sectioned, and processed for calbindin immunoreactivity and hematoxylin-eosin stain. The intensity of the immunostaining was evaluated by quantitative densitometry. RESULTS: In intact teeth, numerous odontoblasts were aligned underneath the secondary dentine and their cell bodies showed the immunoreactivity. In carious teeth, tertiary dentine had poor- or rich tubular patterns under the carious lesion. Underneath the tubule-poor tertiary dentine, distinct odontoblasts could not be seen at the central site. However, some cells with a flat appearance were located at this site and were immunonegative for calbindin D-28k. On the other hand, columnar odontoblasts were seen at the peripheral site, and their cell bodies and processes showed strong immunoreactivity. Underneath the tubule-rich tertiary dentine, columnar odontoblasts were abundantly distributed, and the strong immunoreactivity was observed in their cell bodies and processes. The immunoreactivity in odontoblasts underneath the tertiary dentine with poor or rich tubular pattern was more intense than that for the secondary dentine in intact teeth (P<0.05). On the other hand, the intensity of the immunoreactivity in odontoblasts was similar underneath the secondary dentine in intact and carious teeth. CONCLUSIONS: The present study demonstrated that calbidin D-28k was actively synthesised by odontoblasts under the carious lesion. These findings may suggest that this protein plays an important role in the tertiary dentine formation.

Effect of fluoride application on tensile bond strength of self-etching adhesive systems to demineralized dentin.

STATEMENT OF PROBLEM: It has been reported that the bond strength of composite to demineralized dentin is lower than that to sound dentin. This can be a problem in the success of so-called sealed restorations. PURPOSE: The aim of this study was to evaluate the effect of fluoride application on the tensile bond strength of self-etching adhesive systems to demineralized dentin. MATERIAL AND METHODS: One hundred twenty extracted bovine incisors were ground flat with 600-grit silicone carbide paper. Ninety teeth were then immersed in acetate buffer (pH 4.0) to form demineralized dentin. These teeth were randomly divided into 3 groups of 30 each: surfaces treated with fluoride solution (Group NF), surfaces treated with fluoride solution followed by a water rinse (Group RF), and control surfaces with no pretreatment (Group C). The remaining 30 teeth comprised a group with normal dentin surfaces (Group S). Each group was further divided into 3 subgroups of 10 each to test the bond strength test of Clearfil SE Bond, Unifil Bond, and Mac-Bond II. Tensile bond strengths (in MPa) were measured with a universal testing machine at a crosshead speed of 0.5 mm/min. Mean bond strengths were analyzed by 2-way analysis of variance and Fisher's PLSD (P =.05). SEM observations of the surfaces before and after priming and at resin-dentin interfaces in each group were performed. Elemental analysis of the dentin surfaces before priming was also carried out. RESULTS: The bond strengths of the adhesives to demineralized dentin in Groups NF, RF, and C were significantly lower than that of the normal dentin in Group S (P <.05). The mean bond strengths of the 3 adhesives in Group NF were higher than those in Groups RF and C, but a significant difference was observed only when Clearfil SE Bond was used (P <.05). In SEM images the open dentinal tubules on the surface and the resin tag formation at the resin-dentin interface were apparent in Group NF but were not observed in Groups RF and C. On elemental analysis, considerable amounts of fluoride and calcium were detected in the surfaces of Group NF. CONCLUSION: Within the limitations of this study, the surface treatment with fluoride solution supported the resin tag formation at the resin-dentin interface and slightly improved the bond strength of the self-etching adhesive systems tested to demineralized dentin. This result indicated that the fluoride treatment to demineralized dentin might contribute to the success of the sealed restoration.

Effects of fluoride release from bis-GMA/TEGDMA resin regulated by gamma-methacryloxypropyltrimethoxysilane on demineralization of bovine enamel.

We previously demonstrated that fluoride release from resins could be regulated by the polysiloxane coating of the fluoride additives. The present study investigated the effects of regulated fluoride release from resin on enamel demineralization in vitro. Bovine enamel cavities were restored with bis-GMA/TEGDMA resins containing 50 wt% NaF powders treated with or without gamma-methacryloxypropyltrimethoxysilane. Specimens were immersed in distilled water that was changed daily to measure the amount of fluoride released over 40 days, and thereafter subjected to pH-cycling. Microradiographic observations were performed to determine total mineral loss (AZ) and lesion depth (Ld) on the enamel. In addition, fluorine distribution was analyzed using EPMA. The resin containing untreated NaF exhibited high-rate and short-term fluoride release, whereas the resin containing treated NaF released low concentrations of fluoride over a longer period. The former showed high fluorine uptake in the adjacent enamel. In contrast, the latter showed high fluorine uptake not only in the adjacent enamel, but also in a wider area of enamel surface. The latter also showed lower AZ and Ld values in the surrounding enamel, indicating a high inhibitory effect on caries formation. Therefore, it is suggested that regulated fluoride release from the resin based on polysiloxane coating is effective in preventing caries formation.

Regulation of NaF release from bis-GMA/TEGDMA resin using gamma-methacryloxypropyltrimethoxysilane.

OBJECTIVES: The aim of this study was to evaluate the feasibility of regulation of NaF release from bis-GMA/TEGDMA resin using gamma-methacryloxypropyltrimethoxysilane (gamma-MPTS). METHODS: NaF powder was treated with gamma-MPTS to form a polysiloxane layer on its surface. The morphology and the composition of the NaF powder treated with gamma-MPTS were evaluated using scanning electron microscopy, infrared spectroscopy, contact angle measurement and X-ray photoelectron spectroscopy. Bis-GMA/TEGDMA resin containing 50 wt% NaF powder was prepared as a model resin and immersed in distilled water at 37 degrees C, and the amount of fluoride released from the resin was measured using a fluoride electrode. The mechanical strength in terms of diametral tensile strength before and after fluoride release was also measured, and statistically analyzed using one-way factorial ANOVA and Fisher's PLSD method. RESULTS: NaF powder was covered with hydrophobic gamma-MPTS delivered polysiloxane. A larger amount of fluoride was released at the initial stage from the resin containing NaF treated with no gamma-MPTS. However, fluoride release terminated in a relatively shorter period. In contrast, we observed a smaller amount of fluoride released for a longer period from the resin containing NaF treated with gamma-MPTS. SIGNIFICANCE: We found that gamma-MPTS treatment is useful for the regulation of NaF release from bis-GMA/TEGDMA resin. The mechanism of slow NaF release may be the formation of a hydrophobic polysiloxane layer on the surface of NaF powder and resulting slow water diffusion to NaF powder.