Yake Wang

Spectrophotometric evaluation of the optical influence of core build-up composites on all-ceramic materials.

OBJECTIVES To evaluate the optical influence of core build-up composites on the resultant color of ceramic-composite combinations, and analyze the color difference of ceramic-composite combinations to Vita Lumin shade guide with the same nominal shade. METHODS Thirty ceramic specimens, with a standardized thickness, were made from three all-ceramic materials (Empress2, In-Ceram, Vita Mark 2). Nominal shades A1 and A3 of the Vita Lumin shade guide were selected. Fifty disc-shaped composite specimens were fabricated using ten colors of core build-up composites. The combinations of ceramic and resin specimens were used to simulate the all-ceramic restorations. The colors of the combinations and A1/A3 shade tabs were measured with a spectrophotometer. The results were converted to CIE L*a*b* and CIE L*C*H* values, then color differences (DeltaE) and translucency parameters (TP) were calculated for each combination and ceramic material. Mean DeltaE values were analyzed with three-way ANOVA and Turkeys multiple comparison tests were used to evaluate the within-group effect of the shades of the composites. The corrections between the DeltaEs and TPs were evaluated using a linear analysis. RESULTS Color differences were significantly influenced by the composite shade, ceramic system, and ceramic shade (P<0.001). Mean color differences were 7.023, 8.290, and 6.347 for In-Ceram, Empress2 and Mark2 system, respectively. DeltaE values were significantly associated with the TP values. SIGNIFICANCE The color of underlying core composite has a significantly influence on the resultant color of an all-ceramic restoration. The use of the Vita Lumin shade guide does not accurately achieve the intended color duplication.

Epigallocatechin-3-gallate (EGCG) enhances the therapeutic activity of a dental adhesive

OBJECTIVES The purpose of this study was to evaluate the antibacterial potential and physicochemical properties of a dental adhesive incorporated with epigallocatechin-3-gallate (EGCG) in different concentration over time. METHODS EGCG was incorporated at a ratio of 100, 200, and 300 μg/ml into a dental adhesive. The effects of the cured adhesives on the growth of Streptococcus mutans were determined by direct contact test immediately or one month later and by scanning electron microscopy (SEM), respectively. Microtensile bond strength (μTBS) test was used to test the mechanical property of the adhesives immediately or six months later. The degree of conversion (DC) of the adhesives was evaluated by Fourier transform infrared spectroscopy (FTIR). RESULTS Compared with negative control, the 200 μg/ml and 300 μg/ml EGCG-incorporated dental adhesive were found to exhibit inhibitory effect on the growth of S. mutans. The μTBS of the EGCG-incorporated dental adhesive was higher than the control. The DC of the adhesive system was not affected by the addition of EGCG. CONCLUSIONS 200 μg/ml EGCG incorporated dental adhesives could accomplish therapeutic goals that play in antimicrobial function whilst keeping the durability of resin-dentine bond.

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 pretreatment with calcium- containing desensitizer on the dentine bonding of mild self-etch adhesives

Desensitizing agents are frequently applied to sensitive teeth and may affect subsequent resin bonding. The current study aimed to evaluate the bonding performance of two self-etch adhesives containing functional monomers to dentine pretreated with three new calcium-containing desensitizers. No desensitizer was applied in the control group. Groups 1, 2, and 3 were treated with an arginine-calcium carbonate-containing polishing paste, a casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-containing paste, and an experimental hydroxyapatite paste, respectively. G-Bond and Clearfil S(3) Bond were used for bonding after desensitizer treatments. The microtensile bond strength (μTBS) was tested (n = 20 beams per group) and failure mode distribution was analyzed. Scanning electron microscopy was used to observe the occlusion of dentinal tubules. The mean (±SD) μTBS values, expressed in MPa, of groups 1, 2, and 3 and the control group were, respectively, 30.81 (7.79), 44.41 (8.02), 31.49 (6.13), and 41.40 (8.67) for G-Bond and 39.63 (9.59), 32.55 (7.86), 37.50 (8.60), 27.90 (6.52) for S3 Bond. Most failures were recorded as adhesive failure (69.375%), instead of cohesive failure or mixed failure. The dentinal tubules were seldom plugged in group 2, but were mostly occluded in groups 1 and 3. Two-way anova indicated that desensitizer application in association with a compatible adhesive system should be used when endeavoring to control hypersensitivity without adverse interference in bonding.

Effect of intracanal dentine wettability on human dental pulp cell attachment

AIM To evaluate the effect of intracanal dentine wettability on human dental pulp cell (HDPC) attachment after application of endodontic irrigants. METHODOLOGY Twenty extracted human premolar teeth with straight canals were sectioned at the apical and coronal thirds of each root, and the remaining mid-root portions were bisected longitudinally. After polishing, the specimens were divided into two groups for wettability and cell attachment measurements, respectively. The intracanal surface wettability was assessed by atomic force microscopy after a rinse of H(2) O (control), 5.25% sodium hypochlorite (NaOCl), 17% ethylenediaminetetraacetic acid (EDTA) and MTAD (n = 5). Additionally, HDPCs were seeded onto the irrigated root canal dentine and the cell attachment was evaluated by calcein-CAM and propidium iodide (PI) dying under fluorescence microscope (n = 5). Data were analysed by means of one-way anova and LSD test. RESULTS Compared with the control group, 5.25% NaOCl, 17% EDTA and MTAD treatment significantly increased surface wettability (P < 0.001). The rank order of adhesion force was MTAD >17% EDTA >5.25% NaOCl > H(2) O. The highest average numbers of viable HDPCs were observed on the root canals irrigated with MTAD, followed by the 17% EDTA group (P < 0.001), and the lowest average numbers of viable cells were detected in the 5.25% NaOCl and H(2) O groups. CONCLUSIONS Surface wettability was affected by the irrigants. Increasing in wettability produced higher levels of HDPC attachment to irrigated dentine.

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. Tukeys 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.

Effects of chlorhexidine on bonding durability of different adhesive systems using a novel thermocycling method

BACKGROUND The purpose of this study was to evaluate the influence of chlorhexidine on the bonding durability of etch-and-rinse and self-etch adhesive systems using the polymerase chain reaction (PCR) thermocycling method. METHODS Twenty freshly extracted intact human third molars were ground and bonded with either an etch-and-rinse adhesive (Single-Bond) or a self-etch adhesive (G-Bond). Specimens were either left untouched or placed in PCR tubes filled with three thermocycling mediums: water, chlorhexidine or silicone oil. Thermocycling (5000 cycles) was done using the PCR programme at temperatures of 5 °C and 55 °C. The microtensile bond strength (μTBS) was evaluated and interfacial nanoleakage was assessed by scanning electron microscopy before and after thermocycling. RESULTS Significant differences were detected among groups kept in different media after thermocycling. For Single-Bond, both the chlorhexidine and silicone oil groups could preserve the μTBS (p < 0.001). For G-Bond, μTBS of the chlorhexidine and water groups were significantly decreased (p < 0.05). No obvious increase in silver deposition was observed in specimens incubated in water after thermocycling, less silver penetration was found in specimens incubated in chlorhexidine. CONCLUSIONS In this experimental model, chlorhexidine was found to preserve bonding durability in Single-Bond but have no significant effects on G-Bond.

Effect of silane pretreatment on the immediate bonding of universal adhesives to computer-aided design/computer-aided manufacturing lithium disilicate glass ceramics

The aim of this study was to investigate the effect of silane pretreatment on the universal adhesive bonding between lithium disilicate glass ceramic and composite resin. IPS e.max ceramic blocks etched with hydrofluoric acid were randomly assigned to one of eight groups treated with one of four universal adhesives (two silane-free adhesives and two silane-containing adhesives), each with or without silane pretreatment. Bonded specimens were stored in water for 24 h. The shear bond strength (SBS) of the ceramic-resin interface was measured to evaluate bond strength, and the debonded interface after the SBS test was analysed using field-emission scanning electron microscopy to determine failure mode. Light microscopy was performed to analyse microleakage and marginal sealing ability. Silane pretreatment significantly and positively influenced SBS and marginal sealing ability. For all the universal adhesive groups, SBS increased and the percentage of microleakage decreased after the pretreatment. Without the pretreatment, SBS and the percentage of microleakage were not significantly different between the silane-containing universal adhesive groups and the silane-free groups. Cohesive failure was the main fracture pattern. The results suggest that additional silane pretreatment can effectively improve the bonding strength and marginal sealing of adhesives to lithium disilicate glass ceramics. The bonding performance of silane-containing universal adhesives without pretreatment is similar to that of silane-free adhesives.

Effect of chemical interaction on the bonding strengths of self-etching adhesives to deproteinised dentine

OBJECTIVES The present study examined (1) the chemical interaction between three self-etching adhesives and sodium hypochlorite (NaOCl)-deproteinised dentine, and (2) the influence of NaOCl treatment on bond strength of self-etching adhesives with/without adhesive functional monomers to dentine. METHODS Caries-free dentine disks (control) and those treated with 5.25% NaOCl for 60s were prepared. Xeno V (no functional monomers), G-Bond (containing 4-MET) or S3 Bond (containing 10-MDP) were applied to the NaOCl-treated dentine and either left without further treatment, or rinsed with 100% ethanol or distilled water. Attenuated total reflection (ATR) spectroscopy and field-emission scanning electron microscopy (FE-SEM) were used to evaluate the affinity of functional monomers with deproteinised dentine. Chemical interaction between the functional monomers and deproteinised dentine was evaluated using thin-film X-ray diffraction (TF-XRD). Microtensile bond strength (MTBS) was used to evaluate the mechanical property of the adhesives, either immediately or after thermo-cycling (5-55°C) for 10,000 cycles. RESULTS According to the ATR and FE-SEM results, G-Bond and S3 Bond showed stronger affinity to deproteinised dentine than Xeno V even after rinsing with water. TF-XRD showed that chemical interaction between S3 Bond and deproteinised dentine occurred by formation of 10-MDP-Ca salt. Both deproteinisation and thermo-cycling adversely affected the MTBS of Xeno V (P<0.05) but deproteinisation had no significant influence on S3 Bond. CONCLUSIONS When bonding to NaOCl-treated dentine, self-etch adhesives containing functional monomers (10-MDP) can maintain immediate and aged bond strengths after 10,000 thermal cycles.

Expression of Pannexin3 in human odontoblast-like cells and its hemichannel function in mediating ATP release

OBJECTIVE The aim of this study is to investigate the expression of pannexin3 (Panx3) in human odontoblast-like cells (hOBs) and its hemichannel function in mediating ATP release. METHODS RT-PCR and immunofluorescence analysis were used to detect the expression of pannexins (Panxs) in human dental pulp tissue and cultured cells. To determine the role of Panx3 in ATP release, hOBs were infected with Panx3-overexpression lentivirus, Panx3-shRNA lentivirus or control lentivirus and then stimulated with cold buffer. Intracellular ATP was monitored using quinacrine, and then semi-quantitatively analyzed. In the meantime, the ATP release was quantitatively analyzed using the bioluminescence method when the cells were exposed to cold stimulus. RESULTS Panx3 mRNA and protein were found in dental pulp tissue and cultured cells. Upon cold stimulus, intracellular ATP was released into the extracellular space. Overexpression of Panx3 accelerated ATP release, whereas inhibition of Panx3 suppressed this process. CONCLUSION Panx3 hemichannel is expressed in human odontoblast-like cells and mediates ATP release into the extracellular space.