Anti-demineralization characteristics of surface pre-reacted glass-ionomer (S-PRG) filler-containing varnishes.

This study investigated the anti-demineralization effects of surface pre-reacted glass-ionomer (S-PRG) filler-containing varnishes. Thirty-five bovine root specimens were divided into five treatment groups, with seven specimens each coated with 1) MI varnish (MIV), 2) F varnish (FV), 3) PRG varnish I (PV), 4) PRG varnish II (with sodium fluoride added, PVF), and 5) acid-resistant nail varnish (Control). A 3×1 mm area of the dentin surface adjacent to each varnish was demineralized for one week at 37°C. Integrated mineral loss (IML) of these lesions was determined by transverse microradiography, as was the amount of fluoride released by each material. IML was significantly lower in the PV and PVF groups than in the Control group, and was significantly lower in the PVF than in the MIV and FV groups. These findings indicated that S-PRG filler-containing varnishes, especially varnish containing sodium fluoride, had superior anti-demineralization effects on root dentin.

Effects of resin-based temporary filling materials against dentin demineralization.

This study investigated the in vitro anti-demineralization effects of resin-based temporary filling materials containing surface prereacted glass-ionomer (S-PRG) filler on dentin. Bovine root dentin specimens with a 3×3 mm experimental surface were divided into four treatment groups: DuraSeal (DU) as a control, S-PRG filler-free temporary material (S0), material containing 10% (S10) and 20% (S20) S-PRG filler. Each material was applied to 3×2 mm of the experimental surface, and the specimens were immersed in 8% methylcellulose gel demineralization system for one week at 37˚C. Mineral profiles and integrated mineral loss (IML) of lesions induced on the surface (3×1 mm) adjacent to the materials were computed by transversal microradiography. S10 and S20 yielded thick surface layers and shallow lesion bodies, with significantly lower IML than DU and S0 (p<0.05, Tukey's test). These findings indicate that temporary filling resin-based materials containing over 10% of S-PRG filler content have anti-demineralization effects on adjacent dentin.

Effect of the coating material on root dentin remineralization in vitro.

PURPOSE: A fluoride-releasing coating material containing surface pre-reacted glass-ionomer (S-PRG) filler has become commercially available. However, there has been no detailed investigation of its remineralization effects at various tooth surface regions. The remineralization effects of S-PRG filler-containing coating material at different sites of demineralized dentin surfaces in vitro were evaluated. METHODS: Baseline lesions were prepared on bovine root dentin surfaces by immersion in demineralization buffer and divided into four groups: (B)--baseline lesion; (P)--S-PRG filler-containing material; (V)--S-PRG filler-free coating material as negative control; and (X)--resin-modified glass- ionomer as positive control. Material was applied to half the lesion surface, then P, V and X were remineralized in a gel system. Mineral profiles, integrated mineral loss (IML) and lesion depth (LD) at four regions, i.e. 1--exposed dentin surface adjacent to the material; 2--at a distance from the material; 3--beneath the material near to the edge; and 4--at a distance from the edge, were analyzed by transversal microradiography. Data were analyzed using ANOVA and Games-Howell test with α = 0.05. RESULTS: B showed typical artificial demineralized lesion. The IMLs of V, P and X at regions 1 and 2, and P and X at region 3 were significantly lower than that of B, however, those of V at region 3 and the other three groups at region 4 were not significantly different from that of B. At region 1, P and X showed significantly lower IMLs than V. At region 2, the IML of X showed significantly lower IML than V. There was no significant difference between P and X. The LD values of V, P and X at all regions were not significantly different from that of B. Fluoride, strontium and silicate ions released from the S-PRG filler would provide a favorable environment for remineralization of the demineralized dentin in P.

Analysis for distinctive activation patterns of pain and itchy in the human brain cortex measured using near infrared spectroscopy (NIRS).

Pain and itch are closely related sensations, yet qualitatively quite distinct. Despite recent advances in brain imaging techniques, identifying the differences between pain and itch signals in the brain cortex is difficult due to continuous temporal and spatial changes in the signals. The high spatial resolution of positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) has substantially advanced research of pain and itch, but these are uncomfortable because of expensiveness, importability and the limited operation in the shielded room. Here, we used near infrared spectroscopy (NIRS), which has more conventional usability. NIRS can be used to visualize dynamic changes in oxygenated hemoglobin and deoxyhemoglobin concentrations in the capillary networks near activated neural circuits in real-time as well as fMRI. We observed distinct activation patterns in the frontal cortex for acute pain and histamine-induced itch. The prefrontal cortex exhibited a pain-related and itch-related activation pattern of blood flow in each subject. Although it looked as though that activation pattern for pain and itching was different in each subject, further cross correlation analysis of NIRS signals between each channels showed an overall agreement with regard to prefrontal area involvement. As a result, pain-related and itch-related blood flow responses (delayed responses in prefrontal area) were found to be clearly different between pain (τ = +18.7 sec) and itch (τ = +0.63 sec) stimulation. This is the first pilot study to demonstrate the temporal and spatial separation of a pain-induced blood flow and an itch-induced blood flow in human cortex during information processing.

Fluoride release and recharge characteristics of denture base resins containing surface pre-reacted glass-ionomer filler.

The flexural strength, flexural modulus, and the amount of fluoride released from four experimental denture base resins containing 5, 10, 20 and 30 wt% surface pre-reacted glass-ionomer (S-PRG) filler added to the powder were evaluated. The mean flexural strength of the experimental resins, except the 30 wt%, and the flexural modulus of all the resins, complied with ISO 1567 requirements. In the 20 wt% resin, the amount of fluoride released in the initial phase was 1.88 microg/cm2/day, after which the level decreased. After recharging in a 9000 ppm fluoride solution for eight hours, the level of released fluoride increased markedly to 40.21 microg/cm2/16 hrs. Our results show that fluoride levels increased as a function of the S-PRG filler content. After the almost completely discharged resins were recharged, similar fluoride release occurred again. These results suggest that denture base resins containing S-PRG filler have great recharge and release capabilities which may assist in preventing root caries of abutment teeth.

Effect of denture base-resin with prereacted glass-ionomer filler on dentin demineralization.

The demineralization of dentin was studied when placed adjacent to one of four experimental denture base-resins. These experimental resins contained polymethylmethacrylate (PMMA) and 0, 5, 10, 20 or 30 wt% surface reaction-type prereacted glass-ionomer (S-PRG) filler, respectively. A dentin thin-section was sandwiched between these resins and subjected to demineralization for 1 wk. Microradiographic analyses showed that the mineral vol% of the surface was increased, and lesion formation was inhibited, in a dose-response relationship with the amount of S-PRG filler. Moreover, the mineral loss decreased, by up to 60%, with an increasing amount of filler. These results indicate that denture base-resins containing S-PRG filler possess a substantial inhibition capability against demineralization, and this may thereby assist in preventing root caries of abutment teeth.

Formation of inhibition layers with a newly developed fluoride-releasing all-in-one adhesive.

This study evaluated the capability of a novel fluoride-releasing, all-in-one adhesive system on forming inhibition layer (radio-opaque layer) as compared with other adhesive systems. Dentin surface was treated with Imperva bond (IB), FL-BOND (FB), Reactmer bond (RE), or FL-BOND S-1 (FS) (which is a novel system). Untreated specimens were categorized as nonbonding group (NB). After storing for 10 days in de-ionized water, the specimens were cut into halves perpendicularly to the pulp chamber and immersed in a buffered demineralizing solution for four days. Longitudinal sections were cut and microradiographed. The width of inhibition layers adjacent to the adhesive surface--at a depth of 50 microm under the demineralization surface--was analyzed. Microradiography revealed distinct inhibition layers adjacent to the experimental surfaces of FB, RE, and FS. No inhibition layers were observed in NB and IB. In particular, the width of the inhibition layer of FS (12.5 microm) was significantly greater than those of FB and RE. These results indicated that a newly developed all-in-one adhesive system, FS, may have a superior ability of forming inhibition layers adjacent to cavity walls, and that it may also protect dentin against further demineralization in case of secondary marginal caries.