Antibacterial and physical properties of EGCG-containing glass ionomer cements.

OBJECTIVES: To evaluate the effect of the addition of epigallocatechin-3-gallate (EGCG) on the antibacterial and physical properties of glass ionomer cement (GIC). METHODS: A conventional GIC, Fuji IX, was used as a control. EGCG was incorporated into GIC at 0.1% (w/w) and used as the experimental group. Chlorhexidine (CHX) was added into GIC at 1% (w/w) as a positive control. The anti-biofilm effect of the materials was assessed by a colorimetric technique (MTT assay) and scanning electron microscopy (SEM). The leaching antibacterial activity of the materials on Streptococcus mutans was evaluated by an agar-diffusion test. The flexural strength of the materials was evaluated using a universal testing machine and the surface microhardness was measured using a microhardness tester. The fluoride-releasing property of the materials was tested by ion chromatography. RESULTS: The optical density (OD) values of the GIC-EGCG group were significantly decreased at 4h compared with the GIC group, but only a slightly decreased tendency was observed at 24h (P>0.05). No inhibition zones were detected in the GIC group during the study period. Significant differences were found between each group (P<0.05). Compared with the control group, there was a significant increase in the flexural strength and surface microhardness for the GIC-EGCG group (P<0.05). The fluoride ion release was not influenced by EGCG-incorporation (P>0.05). CONCLUSIONS: These findings suggested that GIC-containing 0.1% (w/w) EGCG is a promising restorative material with improved mechanical properties and a tendency towards preferable antibacterial properties. CLINICAL SIGNIFICANCE: Modification of the glass ionomer cements with EGCG to improve the antibacterial and physical properties showed some encouraging results. This suggested that the modification of GIC with EGCG might be an effective strategy to be used in the dental clinic. However, this was only an in vitro study and clinical trials would need to verify true outcomes.

Effect of an 8.0% arginine and calcium carbonate in-office desensitizing paste on the microtensile bond strength of self-etching dental adhesives to human dentin.

PURPOSE: To evaluate in the laboratory the effect of an 8.0% arginine and calcium carbonate desensitizing paste in occluding open dentin tubules and examine the effect of bonding between the adhesive agents and dentin after being treated with the desensitizing paste. METHODS: Two self-etching adhesives were used. Intact human premolars extracted for orthodontic reasons were used within 3 months of extraction. The occlusal enamel was removed and dentin slices were polished. The dentin tubules were opened by etching with a 1% citric acid solution for 20 seconds to simulate a postoperative sensitivity model. Then the specimens were randomly assigned into five groups. Group A: specimens without any treatment (control). Group B: specimens were polished with a slurry (SiO2) for 30 seconds. Groups C, D and E: 8.0% arginine and calcium carbonate desensitizing paste was applied. Specimens in Group C were polished for 3 seconds, and then repeated for another 3 seconds for a total of 6 seconds, according to the manufacturer's instructions: specimens in Group D were polished twice for 9 seconds for a total of 18 seconds; and specimens in Group E were treated for an extended time of 30 seconds. Each group was randomly divided into two sub-groups in order to evaluate the effect on two different adhesive agents. A one-step self-etching adhesive agent (G-Bond) and a two-step self-etching adhesive agent (F1-Bond II) were applied following the manufacturers' instructions. Then microtensile bond strengths of the 10 groups were tested. SEM was used to evaluate the laboratory effect of the desensitizing paste in occluding open dentin tubules. Statistical analysis was carried out using SPSS version 16.0. RESULTS: The SEM observations showed that the 8.0% arginine and calcium carbonate desensitizing paste could occlude the dentin tubules effectively, and thus may have potential benefits in preventing postoperative sensitivity based on the hydrodynamic theory. An extended application time of 18 or 30 seconds showed no adverse effect of the desensitizing paste on the bonding performance to dentin when using self-etching adhesives containing functional monomers such as 4-MET like G-Bond.

Ethanol-wet bonding may improve root dentine bonding performance of hydrophobic adhesive.

OBJECTIVES: The current study aimed to assess ethanol-wet dentine surfaces by atomic force microscopy (AFM), and to evaluate the efficacy of ethanol-wet bonding on root dentine by determining the shear bond strength (SBS) and interfacial nanoleakage expression. METHODS: Flat dentine slices from human premolar roots were randomly grouped into five. All specimens were acid-etched, rinsed, and left moist. They were then treated with 100% ethanol for 0s (control group), 20s (Group 1), 60s (Group 2), three 60s periods (Group 3), or stepwise ethanol application (Group 4). After treatment, each group was bonded either with Adper™ Scotchbond™ Multi-Purpose (Scotchbond) or experimental hydrophobic adhesive. Nano-scale adhesion forces (Fad) were probed by AFM and analysed using one-way ANOVA. The SBS results were analysed using two-way ANOVA. Tukey's test was employed for multiple comparisons. RESULTS: Ethanol-wet protocols significantly decreased the value of Fad (p<0.001). When bonded with Scotchbond, ethanol treatment did not affect the bond strength (p>0.05), but decreased the interfacial nanoleakage. The SBS values of the groups bonded with hydrophobic adhesive varied with different ethanol-wet protocols (p<0.05). Decreased nanoleakage was manifested in all experimental groups, except Group 1. Compared with the classical water-wet bonding with Scotchbond in the control group, Group 4 bonded with hydrophobic adhesive exhibited a significantly higher bond strength (p<0.05). CONCLUSIONS: Ethanol-wet bonding using a stepwise ethanol application protocol may have potential benefits in the root dentine bonding of hydrophobic adhesive.

Synthesis and characterization of triethylene glycol dimethacrylate nanocapsules used in a self-healing bonding resin.

OBJECTIVES: To date, the production of highly durable dentine bonding is still a challenge. Self-healing bonding resins may provide a new direction for the improvement of the bonding durability. The objective of the current study was to synthesize polyurethane nanocapsules encapsulated with the core material triethylene glycol dimethacrylate (TEGDMA) for use as a major component in a self-healing bonding resin. METHODS: TEGDMA nanocapsules were synthesized via interfacial polycondensation in a miniemulsion, and the TEGDMA nanocapsules were then characterized via Fourier-transform infrared (FTIR) spectrometer, field emission scanning electron microscopy (FESEM), and high-performance liquid chromatography (HPLC) to investigate the morphology, the average TEGDMA loading (DL%), and encapsulation efficiency (EE%). The mechanical property of dental adhesive with different concentrations (0, 3, 6, 9, and 12 wt%) of the TEGDMA nanocapsules were also measured, and the cytotoxicity was investigated using an MTT assay. RESULTS: FTIR confirmed that the TEGDMA nanocapsules were successfully synthesized. These nanocapsules showed a high drug load. The bond strength of the dental adhesive incorporated with 9 wt% TEGDMA nanocapsules was significantly higher compared with those of the other groups (P<0.001). Moreover, the biocompatibility of the dental adhesive was not affected by the incorporation of the TEGDMA nanocapsules. CONCLUSIONS: The current study demonstrated the successful synthesis of TEGDMA nanocapsules, and the overall properties of the dental adhesive were not compromised.