Synthesis of ß-tricalcium phosphate by modifying the heating process of a dental casting mold.

This study investigated a novel method for artificial synthesis of ß-tricalcium phosphate (ß-TCP). The binder of the phosphate-bonded investment was replaced with calcium oxide instead of magnesium oxide and sintered in an electric furnace. The water/powder mixing ratio for hardening was determined using preliminary experiments. Thermal analysis was performed to check the thermal behavior of the sample tested. In addition, the fired sample was analyzed using an X-ray diffraction apparatus to identify the compounds after sintering. The hardened sample exhibited multiple compounds, including unreacted components, post which, new compounds were generated by heating. Peaks of calcium pyrophosphate and ß-TCP were confirmed at 800ºC and 1,300ºC, respectively. ß-TCP could be easily synthesized within the limited study by sintering at 1,300ºC both monoammonium phosphate and calcium oxide. Experimental results suggest that ß-TCP can be easily synthesized by simulating the conventional dental casting process.

Fluoride Retention in Root Dentin following Surface Coating Material Application.

This study aimed to use an in-air micro-particle-induced X-ray/gamma emission (in-air µPIXE/PIGE) system to evaluate tooth-bound fluoride (T-F) in dentin following the application of fluoride-containing tooth-coating materials. Three fluoride-containing coating materials (PRG Barrier Coat, Clinpro XT varnish, and Fuji IX EXTRA) and a control were applied to the root dentin surface of human molars (n = 6, total 48 samples). Samples were stored in a remineralizing solution (pH 7.0) for 7 or 28 days and then sectioned into two adjacent slices. One slice of each sample was immersed in 1M potassium hydroxide (KOH) solution for 24 h and rinsed with water for 5 min for the T-F analysis. The other slice did not undergo KOH treatment and was used to analyze the total fluoride content (W-F). The fluoride and calcium distributions were measured in all the slices using an in-air µPIXE/PIGE. Additionally, the amount of fluoride released from each material was measured. Clinpro XT varnish demonstrated the highest fluoride release among all the materials and tended to show high W-F and T-F and lower T-F/W-F ratios. Our study demonstrates that a high fluoride-releasing material shows high fluoride distribution into the tooth structure and low conversion from fluoride uptake by tooth-bound fluoride.

Prevention of Root Caries Using Oxalic Acid.

Certain dentin hypersensitivity treatment materials include oxalic acid to coat dentin surfaces with minerals, while certain organic acids possess a remineralization effect. Herein, an organic acid that inhibits the demineralization and coating of root surfaces was evaluated. Specimens were produced using five non-carious extracted bovines. Four different acids were used: oxalic acid (OA), malonic acid (MA), polyacrylic acid (PA), and succinic acid (SA). Each acid was applied to the root surface and washed using distilled water or a remineralization solution, and the surface was observed using scanning electron microscopy (SEM). All the surfaces of each specimen, barring the polished surface, were covered with wax and immersed in an automatic pH cycling system for two weeks. Dentin demineralization was analyzed using transverse microradiography (TMR) before and after pH cycling. SEM analysis demonstrated that the three acid groups demineralized the dentin surface, whereas the OA group generated crystals covering the dentin surface, even in a distilled water environment. TMR analysis revealed that the OA groups showed significantly lower integrated mineral loss compared with the other groups, even in the distilled water environment. The results suggest that OA generates insoluble calcium oxalate crystals on the dentin and suppresses demineralization even under low saliva conditions.

Inhibition of Demineralization of Dentin by Fluoride-Containing Hydrogel Desensitizers: An In Vitro Study.

Several desensitizers routinely used clinically for dentin hypersensitivity are expected to inhibit demineralization. This study aimed to evaluate the effectiveness of sealing materials in inhibiting demineralization and increasing fluorine (F) uptake by acid-treated root surfaces. Five noncarious extracted human teeth were used to produce specimens. Three different fluoride-containing materials, namely "MS Coat F" (MS), "MS Coat Hys Block Gel" (HS), and CTX2 Varnish (FV), were used herein. Each material was applied to the demineralized root surface. Single sections were obtained from each specimen. All surfaces of each specimen, except the polished surface, were covered with wax and immersed in an automatic pH cycling system for 2 weeks. Fluorine and calcium distributions in the carious lesions of each specimen were evaluated using proton-induced gamma emission (PIGE) and X-ray (PIXE) techniques, respectively. Dentin demineralization was analyzed using transverse microradiography (TMR) before and after pH cycling. µPIXE/PIGE analysis demonstrated that all sample groups showed increased fluoride uptake on the root surface. TMR analysis revealed that both HS and FV showed significantly lower integrated mineral loss values than the control group. All three samples demonstrated a tendency towards increased fluoride uptake from fluoride-containing hypersensitivity desensitizers and a demineralization inhibition effect on root dentin.

Potential of Fluoride-Containing Zinc Oxide and Copper Oxide Nanocomposites on Dentin Bonding Ability.

Despite recent advances in bonding restorations, which are the basis of restorative dentistry, secondary caries are still able to form. Previously, a novel fluoride-containing zinc and copper (ZCF) nanocomposite was introduced to prevent the formation of caries due to its antibacterial activity. In this study, we studied the impact of ZCF nanoparticles on the adhesive strength of bonding restorations through micro-tensile bond strength (µTBS) testing. The impact of antibacterial and matrix metalloproteinase (MMP) inhibitors on the nanoparticles was also examined. The nanocomposites were prepared using a simple one-step homogeneous co-precipitation method at a low temperature. A self-etch adhesive was applied to 10 extracted caries-free human molars with (test group) and without (control group) the ZCF nanoparticles. This was followed by composite resin build-up and µTBS testing, MMP activity assays, and evaluation of the antibacterial effects. The results showed no significant differences in the µTBS between the ZCF and the control groups. However, the ZCF exhibited a significant inhibitory effect against MMP-2, MMP-8, and MMP-9, in addition to an antibacterial effect on Streptococcus mutans. Therefore, the present study demonstrated that the addition of ZCF nanoparticles to adhesive systems can result in MMP inhibition and antibacterial action while maintaining the mechanical properties of the bonding restorations.

In-air micro-proton-induced X-ray/gamma-ray emission analysis of the acid resistance of root dentin after applying fluoride-containing materials incorporating calcium.

This study employed an in-air micro-proton-induced X-ray/gamma-ray emission system to assess the effectiveness of fluoride-containing materials (FCMs) incorporating calcium in preventing root caries. Dentin surfaces of human third molars were coated with one of three FCMs: fluoride-releasing glass-ionomer cement (F7) and experimental materials in which half (P1) or all (P2) of the strontium in F7 was replaced with calcium. Dentin without FCM coating served as the control. Specimens were immersed in saline at 37°C for 1 month, sectioned, and then demineralized. Calcium loss after demineralization was lower in the Ca-substituted groups than in the Ca-unsubstituted groups (p<0.05). Calcium loss was negatively correlated with fluoride uptake (p<0.01). In the F7, P1, and P2 groups, the retraction of the dentin surface was significantly suppressed as compared with the control group. FCMs incorporating calcium improved the acid resistance of root dentin and could help prevent root caries.

Distribution of elements in teeth and inhibition of demineralization by titanium fluoride: Effects of concentration and pH in a titanium fluoride solution.

The purpose of this study was to assess the effects of titanium fluoride (TiF4) concentration and pH on fluoride distribution and demineralization of root dentin surfaces. Concentrations of 0.1%, 1%, and 2% TiF4 (pH 1), 1% TiF4 solution adjusted to pH 4, 5, 6, and 1.35% sodium fluoride (NaF) solution were applied to root dentin surfaces. Each specimen was subjected to pH cycling (pH: 4.5-7.0) for 4 weeks. Lesion depth and calcium, fluorine, and titanium distribution were then evaluated. Our limited study indicates that lesion depth and fluorine and titanium distribution in dentin depend on the concentration of a TiF4 solution. We also found that a 1% TiF4 solution adjusted to a pH 4-6 can reduce demineralization as effectively as a similar concentration of NaF.

Use of new scratch test and tensile test for evaluation of bond strength of selfadhesive flowable resin composite for repair of artificial tooth erosion.

The purpose of this study was to use a new scratch test and tensile test to evaluate the bond strength between artificial erosive enamel or dentin and self-adhesive resin composites as a coating material. Coronal enamel or dentin surface was exposed to an erosive cycle (artificial saliva [AS], pH:7.0 for 6.5 h and acidic carbonated beverages for 5 min, alternated 3 times per day) for the eroded-surface or stored in AS for the remineralized-surface. Two self-adhesive flowable resin composites, Fusio and LLB-CR6 (prototype), and a conventional flowable resin composite, BEAUTIFIL FLOW with self-etching primer system, Clearfil Mega Bond, were applied to enamel or dentin surfaces; and then the bond strengths were measured. For the eroded-surface, there were no significant differences in bonding strength among all materials, as assessed by the new scratch test. Thus, these self-adhesive flowable resin composites might be useful for coating materials on acid-eroded tooth surfaces.

Efficacy of a new filler-containing root coating material for dentin remineralization.

PURPOSE: To evaluate a new root coating material containing surface pre-reacted glass-ionomer (S-PRG) filler for remineralization of demineralized dentin. METHODS: The dentin was exposed on root surfaces of human third molars and demineralized by immersion in demineralization solution for 4 days. The demineralized dentin surface was divided into three areas. The center area was left untreated. The area on one side of the center area was coated with protective wax. The area on the other side was coated with one of four test materials: fluoride-containing S-PRG filler (PRG Barrier Coat: PR), fluoride-containing bonding agent (Bond Force: BF), fluoride-containing glass-ionomer cement as a positive control (Fuji IX EXTRA: EX), or non-fluoride-containing bonding agent as a negative control (Clearfil MegaBond: MB). The samples were stored in remineralization solution for 7 days, and then cut into two slices. The mineral changes, defined as variation in mineral loss between wax-coated area and the central untreated area, were measured in one slice by transversal microradiography. The fluoride concentration was measured in the other slice by µ-particle-induced gamma/X-ray emission. Seven thin specimens (0.25-mm thickness) of each test material were used to determine fluoride ion release from the materials over 21 days. RESULTS: The mineral changes were greatest for EX, followed by PR, with no difference between BF and MB (P> 0.05). Regarding the fluoride concentrations in dentin, there was no difference between EX and PR (P> 0.05). MB had the lowest value (P< 0.01). Fluoride release from EX was largest, followed by PR, with BF showing low fluoride release (P< 0.05). MB had no fluoride release. CLINICAL SIGNIFICANCE: A new coating material with S-PRG filler can be applied in a thin layer on root dentin, which could be especially useful for hard-to-access lesions. This material remineralized demineralized root dentin and had fluoride diffusion characteristics similar to those of glass-ionomer cement in vitro.

A new technique for analyzing trace element uptake by human enamel.

Fluorine (F) and strontium (Sr) are key elements in the de- and remineralization of teeth. To quantitatively analyze the distribution of F and Sr, micro-particle-induced gamma/X-ray emission (PIGE/PIXE) technique was used. The cavities were prepared and filled with the fluoride- and Sr-containing restorative materials (FSCMs) in extracted human molars. The single-section enamel specimens were prepared by slicing from the buccal to lingual surface including the FSCMs. After 5 weeks of automatic pH cycling, the demineralization was calculated by integrated mineral loss (ΔIML) from transverse-microradiography. The distributions of F and Sr were analyzed by the PIGE/PIXE technique. The micro-PIGE/PIXE technique indicated a fluorine uptake difference between the enamel surface and enamel cavity wall. ΔIML of FSCMs were significantly lower than intact enamel. The micro-PIGE/PIXE technique enables measurement of F and Sr uptake from FSCMs into enamel, which would be beneficial for research on caries development and prevention.

Removal of dentin matrix proteoglycans by trypsin digestion and its effect on dentin bonding.

The aim of this study was to investigate the effect of trypsin digestion on removal of chondroitin sulfate proteoglycans (CS-PGs) in demineralized dentin, and subsequent dentin bonding. Bovine dentin fragments were demineralized, treated with or without trypsin, stained with cupromeronic blue, and observed under transmission electron microscopy. Demineralized sections with or without trypsin digestion were also subjected to immunohistochemical analysis with anti-chondroitin-4-sulfate (C4S) monoclonal antibody, 2-B-6. The presence of galactosamine and glucosamine in the trypsin digest was confirmed by amino acid analysis. Bond strength testing was performed on trypsin treated and control specimens where samples were either kept moist or dried and re-wet, then bonded. Bond strength significantly decreased after trypsin treatment (p < 0.05). TEM, immunohistochemical, and amino acid analyses demonstrated that trypsin digestion efficiently removed C4S-PGs from demineralized dentin matrix. This study indicates that the detrimental effects observed on dentin bonding by trypsinization may be due in part to the removal/cleavage of the C4S-PGs, and further underscore the importance of C4S-PGs on dentin bonding.

Fluoride release and uptake by various dental materials after fluoride application.

PURPOSE: To measure the amounts of fluoride released from fluoride-containing materials before and after daily topical fluoride applications. METHODS: A conventional glass-ionomer: Fuji Ionomer Type II (F2); a resin-modified glass-ionomer: Fuji Ionomer Type II LC (LC); two "giomer" materials: Reactmer Paste (RP), and Beautifil (BT); a fluoride-containing resin composite: Unifil F (UF); and a non-fluoride resin composite: AP-X (AP) were used in this study. Each material was filled into a plastic mold, with inner diameter of 9 mm wide x 3 mm high. The specimens were stored in vials filled with 8 ml distilled deionized water for 24 hours at 37 degrees C. The specimens were then removed from the vials and the amount of fluoride released into the water, over the 24-hour period, was measured. The amount of fluoride released was measured by using specific fluoride electrode and an ion-analyzer. These procedures were repeated at Days 2, 3, 7, 14, and 21. After 21 days, all specimens were exposed to 1000 ppm F NaF solution for 5 minutes once a day. This procedure and measurement of fluoride release were continued for 14 days. After 14 days, the specimens were placed in water for 7 days and fluoride release was measured. The results were statistically analyzed using Kruskal-Wallis and Mann-Whitney U-test (P< 0.05). RESULTS: At the 22nd day (1 day after starting fluoride exposure), there was no difference between the F2 and RP, though there were significant differences between the two GICs and the groups BT and UF. After that day, there were significant differences between GIC and the group RP, BT and UF. All materials showed a decrease in fluoride release 7 days after end of the fluoride immersion period. F2, LC, and UF showed no significant difference of fluoride release between Day 21 and 1 day after the end of the fluoride immersion period (P= 0.310: F2 and UF, 0.548: LC). On the other hand, RP and BT revealed lower fluoride release 1 day after the end of the fluoride immersion period as compared to Day 21 (P= 0.075: RP, 1.000: BT). For AP, fluoride release was not detected after the fluoride immersion period.

Prevention of artificial caries: effect of bonding agent, resin composite and topical fluoride application.

This study investigated the effect of fluoride containing resin composites and bonding agents, as well as the topical fluoride (F) application on the inhibition of artificial caries progression by using a pH-cycling model with alternating demineralizing (pH:4.5) and remineralizing (pH:7.0) solutions. Two bonding systems (F-containing bonding system [Reactmer Bond: RB] and non-F containing bonding system [Clearfil SE Bond: SE]), two resin composites, (F-containing [Reactmer Paste: RP] and non-F containing [Clearfil AP-X: AP]) were used. A combination of each bonding agent and a resin composite, RB+RP, RB+AP, SE+RP and SE+AP, was placed in 2 x 3 x 1.5-mm cavities on root dentin of extracted molars (n=96). Specimens were subjected to pH-cycling for 6 or 12 weeks. Half of all specimens were immersed in 0.05% NaF solution for 1 minute once a day as a topical F application. After the pH cycling period, a microradiograph of each specimen was taken, and the outer lesion depth of the artificial caries was measured by means of image analyzing software. The depths of the outer lesions at different periods were analyzed by one-way ANOVA and Sheffe's test at p=0.05. The combination that received F treatment showed reduced lesion depth compared to the same combination without F application. Except for the F application group of 12 weeks, there was no significant difference in lesion depth among each bonding and composite combination (p>0.05). At week 12 with the F application, RB+RP showed the shallowest lesion compared to the other combinations (p<0.05). The results indicated that the F application reduced the progression of artificial caries. Moreover, the combination of fluoride containing bonding agent and restorative material was the most effective for the inhibition of artificial caries progression based on the 12-week experimental period with topical F application.