Effect of phosphoric acid containing polyvinylpyrrolidone as protective etchant for dentin bonding.

STATEMENT OF PROBLEM: Phosphoric acid is commonly used in dentistry as an etchant but can result in excessive demineralization of dentin, a major contributor to the instability of dentin-bonded restorations. Nevertheless, research on the development of etchants that can reduce acid damage is sparse. PURPOSE: The purpose of this in vitro study was to investigate the effects of polyvinylpyrrolidone-modified phosphoric acid on the dentin bonding of an etch-and-rinse adhesive. MATERIAL AND METHODS: Protective etchants were prepared by adding polyvinylpyrrolidone to 35% phosphoric acid aqueous solutions: the 3 concentrations were 0.5% (P0.5% group), 1% (P1% group), and 2% (P2% group) w/v. The treatment agent of the control group (C) was 35% phosphoric acid gel. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), microhardness, microtensile bonding strength (µTBS), nanoleakage, and in situ zymography were used to evaluate the appearance of the protective etchant on dentin bonding. The results were analyzed with a 1-way ANOVA test (α=.05). RESULTS: SEM showed no obviously exposed collagen fiber in the P1% and P2% groups. FTIR showed less demineralization of the dentin surface, and microhardness was higher after treatment with the protective etchant (P<.05). The µTBS of P1% (70 ±9.2 MPa) was the highest, and group C (44 ±5.8 MPa) was the lowest in all groups (P<.05). Moreover, there was weaker MMP activity in the P1% and P2% groups (P<.05). CONCLUSIONS: This study demonstrated that the protective etchant effectively reduced demineralization, enhanced bond strength, and reduced nanoleakage and enzyme activity within the hybrid layer.

Polyvinylpyrrolidone as a primer for resin-dentin bonding.

OBJECTIVE: This study aimed to investigate the effects of polyvinylpyrrolidone (PVP)-containing primer (PCP) on dentin bonding. METHODS: PVP and anhydrous ethanol were used to prepare the PCPs, which were prepared at concentrations of 0.5%, 1%, and 2% (w/v). These PCPs were subsequently applied to the dentin surface, denoted as E1, E2, and E3, respectively. In the control group, no primer was applied. Following the treatment, the dentin surfaces were subjected to analysis using Fourier-transform infrared spectroscopy (FTIR), and the micro-tensile bond strength (MTBS) was evaluated. The failure mode, nanoleakage, and bonding longitudinal section were observed utilizing scanning electron microscopy (SEM). Additionally, the effect of PCPs on matrix metalloproteinases (MMPs) activity was analyzed through an in situ zymography test. Data were subjected to statistical analysis using ANOVA tests (α = 0.05). RESULTS: Significant alterations in the infrared resonances associated with collagen cross-linking within the collagen matrix were observed across all PCP groups. The application of PCP demonstrated a noteworthy enhancement in micro-tensile bond strength (MTBS) compared to group C (p < 0.05). Notably, group C exhibited the lowest MTBS (41 ± 7.7 MPa), whereas group E2 demonstrated the highest MTBS (66 ± 11.9 MPa). Even after undergoing aging, the MTBS of the PCP groups remained superior to that of group C (p < 0.05). The resin tag length in the PCP groups was found to be greater than that of group C, and the occurrence of nanoleakage was comparatively lower in the PCP groups, both before and after aging. Additionally, PCP exhibited a dose-dependent inhibition of matrix metalloproteinases (MMPs) activity, which was statistically significant (p < 0.05). CONCLUSIONS: The utilization of PCP Primer exhibits notable enhancements in bond strength, mitigates nano-leakage, and suppresses enzyme activity within the hybrid layer.

Formulating an altered dentin substrate to improve dentin bonding.

STATEMENT OF PROBLEM: Secondary caries is a major factor in the failure of dental restorations. However, studies on the fabrication of acid-resistant and antibacterial dentin to improve dentin bonding are sparse. PURPOSE: The purpose of this in vitro study was to compare the effects of 2 types of fluoride-containing etchants on dentin bonding and explore the feasibility of formulating an altered dentin substrate to improve dentin bonding. MATERIAL AND METHODS: NaF-containing and SnF2-containing etchants were developed by adding sodium fluoride and stannous fluoride to a 35% phosphoric acid aqueous solution. Two groups (N1 and N2) containing NaF, 10 and 30 mg/mL respectively, and 2 groups (S1 and S2) containing SnF2, 18.6 and 55.8 mg/mL respectively, were formulated. The etchant of the control group (C) was 35% phosphoric acid gel. Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), Fourier transform infrared spectroscopy (FTIR), microhardness, antierosion, and antibacterial tests were performed on the treated dentin. Moreover, the microtensile bond strength (µTBS) of each group was tested, and the fracture mode was determined after testing. Statistical analysis was performed with the 2-way ANOVA test (α=.05). RESULTS: The exposed collagen fiber was observed in group C, and minerals were formed on the dentin in the experimental groups. SEM, FTIR, and the microhardness test indicated more remineralization in the SnF2-containing etchant groups. The µTBS of S1 (77.5 ±10.36 MPa) was the highest in all groups, and group C (38.5 ±9.01 MPa) was the lowest. Moreover, the antierosion and antibacterial properties of the S2 group were the best among all groups (P<.05). CONCLUSIONS: Compared with NaF-containing etchant, SnF2-containing etchant could improve the dentin substrate, increase remineralization, improve bonding strength, and enhance antibacterial ability, especially by increasing resistance to acid erosion.

Surface-modified Ti3C2 MXene nanosheets for mesenchymal stem cell osteogenic differentiation via photothermal conversion.

In the field of bone tissue engineering, the practical application of growth factors is limited by various factors such as systemic toxicity, instability, and the potential to induce inflammation. To circumvent these limitations, the use of physical signals, such as thermal stimulation, to regulate stem cells has been proposed as a promising alternative. The present study aims to investigate the potential of the two-dimensional nanomaterial Ti3C2 MXene, which exhibits unique photothermal properties, to induce osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) via photothermal conversion. Surface modification of Ti3C2 MXene nanosheets with PVP (Ti3C2-PVP) was employed to enhance their colloidal stability in physiological solutions. Characterization and cellular experiments showed that Ti3C2-PVP nanosheets have favorable photothermal properties and biocompatibility. Our study demonstrated that the induction of photothermal stimulation by co-culturing Ti3C2-PVP nanosheets with BMSCs and subsequent irradiation with 808 nm NIR significantly promoted cell proliferation, adhesion and osteogenic differentiation of BMSCs. In conclusion, the results of this study suggest that Ti3C2-PVP is a promising material for bone tissue engineering applications as it can modulate the cellular functions of BMSCs through photothermal conversion.

Bonding effect of a Zr/Si coating prepared on zirconia using a sol-gel method.

STATEMENT OF PROBLEM: Zirconia has been widely used as a dental prosthetic material. However, bonding to zirconia is challenging, and whether a Zr/Si coating would improve bonding is unclear. PURPOSE: The purpose of this in vitro study was to prepare a Zr/Si coating on zirconia ceramics using a sol-gel method and to determine whether the bonding to resin is improved. MATERIAL AND METHODS: Presintered zirconia specimens were prepared and divided into 5 groups: 4 experimental groups with ratios of the binary sol-gel precursor (zirconium oxychloride/tetraethoxysilane) set as 2:1 (Z2), 1:1 (Z1), 0.5:1 (Z0.5), and 0.25:1 (Z0.25) and Group C as the control group. In addition to surface roughness measurements, scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and X-ray diffraction (XRD) were carried out to characterize the surface. Each group was divided into 2 subgroups according to whether a silane coupling agent was applied. Half of the bond specimens were stored in deionized water for 24 hours; the remaining half were aged using 5000 thermocycles. The shear bond strength (SBS) of resin bonded to specimens was tested for the initial and durable bond strength, and the bonding interface was also observed by SEM after debonding. Data were subjected to 1-way ANOVA and the post hoc Tukey honestly significant difference test (α=.05). RESULTS: The Zr/Si coating formed on zirconia ceramics. Z0.5 had the greatest mean ±standard deviation roughness (2.13 ±0.15 µm) and had the highest silicon content (21.7 ±0.21%). t-ZrO2, m-ZrO2, c-SiO2, and ZrSiO4 were detected by XRD in Z1. The SBS values were decreased by aging but were significantly increased by Zr/Si coating, especially for Z0.5, with the application of silane (initial: 22.92 ±2.79 MPa; aged: 9.91 ±0.92 MPa). CONCLUSIONS: The Zr/Si coating significantly improved the initial and aged bond strength, and the optimal Zr/Si ratio of the sol-gel appeared to be 0.5:1.

Biological properties of hydroxyapatite coatings on titanium dioxide nanotube surfaces using negative pressure method.

Titanium (Ti) exhibits superior biocompatibility and mechanical properties but is bioinert, while hydroxyapatite (HA) possesses excellent osteogenesis and is widely used for the modification of Ti surface coatings. However, the synthesis of homogeneous and stable HA on metallic materials is still a major challenge. In this study, porous titanium dioxide nanotube arrays were prepared on Ti surface by anodic oxidation, loaded with calcium and phosphorus precursors by negative pressure immersion, and HA coating was formed by in situ crystallization of calcium and phosphorus on the surface by hydrothermal heating. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and bonding strength were conducted to confirm the surface characteristics of each group. The cell proliferation, mineralization degree, and alkaline phosphatase (ALP) activity of MC3T3-E1 cells on samples were calculated and compared in vitro experiments. Cylindrical samples were implanted into rat femurs to evaluate biocompatibility and osteogenesis in vivo. The results showed that HA crystals successfully synthesized in TiO2 nanotubes, enhancing the bonding strength of HA coating and Ti substrate under negative pressure. Moreover, HA coating on Ti substrate remarkably enhanced cell proliferation and osteogenic differentiation activity in vitro, and improved new bone formation as well as osseointegration in vivo.

Polycrystalline particulates synthesized on zirconia for enhanced bioactivity: An in vitro study.

Zirconia is a promising material for dental implant with its excellent biocompatibility, good mechanical properties, and esthetic effect similar to natural teeth. To improve the bioactivity and osteogenic properties of zirconia, pre-sintered zirconia discs were divided into C, T3 , T5 , and T7 group. Group C was as control. T3 , T5 , and T7 groups were soaked in hydrofluoric acid (HF) for 30, 50, and 70 s, respectively. Then, they were placed into CaCl2 solution and heated in NaOH solution. After sintering, the samples were characterized by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction, which confirmed the ZrO2 polycrystalline particulates in situ synthesized on the treated sample discs. The surface roughness of the treated samples was increased with the prolonged of acid treatment time (p < .05), while the three-point bending strength did not decrease significantly (p > .05). MC3T3-E1 cells were cultured on zirconia discs to evaluate the bioactivity and osteogenic effect of modified zirconia. The living&dead fluorescence staining and CCK-8 assay showed that the specimens were non-toxic and significantly promoted cell proliferation. In addition, the cell proliferation was enhanced with the increase of zirconia surface roughness. Polycrystalline particles modified zirconia were beneficial to cell spreading. After osteogenic induction, MC3T3-E1 cells inoculated on modified zirconia exhibited higher alkaline phosphatase activity, mineralization activity and up-regulated osteogenesis-related gene expression. Above all, in situ synthesized polycrystalline particulates significantly improve the biological activity of zirconia, which will promote the widespread application of zirconia implants.

Etch-mineralizing treatment to improve dentin bonding.

Objectives This study aimed to investigate the effect of etch-mineralizing solution as a dentin treatment agent on dentin bonding. Methods This study designed four kinds of etch-mineralizing solutions (EMs) by adding sodium fluoride in 35% phosphoric acid aqueous solution with four different concentrations (5, 10, 20, and 30 mg/ml), and named F1, F2, F3 and F4, respectively. 35% phosphoric acid gel treatment was the control group. SEM, EDS, FTIR and microhardness tests were performed on the treated dentin. Shear bond strength was measured before and after aging. Nanoleakage was also evaluated. Fracture mode was researched after SBS testing. The antibacterial properties of treated dentin were also investigated through live/dead staining of biofilms. Results The smear layer was removed and mineralization substances were observed on the dentin surface and tubule, and no obvious collagen fibers were observed compared with the control group. FTIR spectrums showed that the ratios of phosphate/collagen on EMs treated dentin surfaces were significantly increased (P < 0.05). F2 group had the highest bonding strength (32.14 ± 7.33 MPa) and microhardness (66.08 ± 10.58), while the control group had the lowest bonding strength (21.81 ± 4.03 MPa) and microhardness (42.34 ± 7.08) (p < 0.05), and excellent bonding strength caused more cohesive fracture. Experimental groups showed less nanoleakage than group C (P < 0.05). Moreover, experimental groups had better antiaging performance and antibacterial properties than the control group (p < 0.05). Conclusion EMs treatment not only improved dentin bonding and antibacterial ability, but also remineralized dentin with autologous mineral elements. Clinical significance The treatment provides a novel therapeutic strategy for obtaining ideal dentin bonding strength and prolonging the longevity of the restoration.

Enhanced osteogenic activity of titania-modified zirconia implant by ultraviolet irradiation.

Zirconia is a superior implant material owing to its high mechanical strength, durable corrosion resistance, superior aesthetic effect and excellent biocompatibility. However, the bioactivity of zirconia surfaces remains a great challenge for implant osseointegration. A titania (TiO2) coating was innovatively synthesized on the surface of zirconia by infiltration in a suspension of zirconium oxychloride and titania for dense sintering. Subsequently, the coating was subjected to ultraviolet (UV) light to enhance the biological inertness of zirconia. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and contact angle analysis were conducted to confirm the surface characteristics. Afterwards, in vitro assessments of cell adhesion, proliferation and osteogenic differentiation of MC3T3-E1 cells were performed. Zirconia samples were implanted into rat femurs to assess biocompatibility and host tissue response in vivo. Micro-CT evaluation and histological testing were conducted. After UV irradiation, the content of hydroxyl groups and hydrophilicity of TiO2-modified zirconia were significantly increased. The results of in vitro experiments showed that TiO2-modified zirconia subjected to UV light could promote cell proliferation and spreading, enhance ALP activity and the degree of mineralization, and upregulate osteogenesis-related genes. Furthermore, in vivo assessments confirmed that UV-irradiated TiO2-modified zirconia implants maximized the promotion of osseointegration. TiO2-modified zirconia after UV treatment will have broad clinical application prospects in improving the osseointegration of zirconia implants.

Mechanical and antibacterial properties of polymethyl methacrylate modified with zinc dimethacrylate.

STATEMENT OF PROBLEM: Polymethyl methacrylate (PMMA) has been widely used for denture base resin. However, concerns associated with PMMA, such as poor mechanical strength, high roughness, and porosity promoting microbial adhesion have been voiced; appropriate modification of PMMA denture base resin may improve its clinical application. PURPOSE: The purpose of this in vitro study was to investigate the effect of zinc dimethacrylate (ZDMA) modification on the mechanical and antibacterial properties of PMMA. MATERIAL AND METHODS: ZDMA at different mass fractions was mixed into PMMA as the experimental group, and unmodified PMMA was the control group. X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and the degree of conversion (DC%) were applied for characterization. Mechanical properties were measured with the 3-point bend test (n=10). The Streptococcus mutans biofilm model was used to investigate the antibacterial property by using colony-forming unit counts, metabolic activity, live/dead staining, quantitative real-time PCR (qRT-PCR), and SEM (n=5). The cell counting kit (CCK)-8 test was used to evaluate cytotoxicity. Data were subjected to analysis of variance and the post hoc Tukey honestly significant difference test (α=.05). RESULTS: SEM-EDS and XRD analysis revealed successful ZDMA incorporation into the PMMA matrix. DC% increased with the mass fraction of ZDMA, and no significant differences in DC% values were found among each tested group (P=.554). ZDMA mass fraction at 1 wt%, 2.5 wt%, and 5 wt% enhanced its mechanical properties, but those at 7.5 wt% and 10 wt% were reduced. The results of antibacterial experiments showed that ZDMA-modified PMMA displayed antibiofilm capabilities. Quantitative real-time PCR indicated that the expression levels of tested genes were significantly suppressed and that CCK-8 test indicated no cytotoxicity. CONCLUSIONS: ZDMA-modified PMMA exhibited antibacterial properties without its mechanical properties being affected. ZDMA is a potential metal crosslinking monomer for the modification of PMMA denture base resin.

Biological activity of titania coating prepared with zirconium oxychloride and titania on zirconia surface.

Zirconia is recognized as a promising dental implant material because of its good biocompatibility, sufficient mechanical strength, minimal ion release and aesthetic effects similar to natural teeth. However, the limitations of inert surface of zirconia affect the long-term efficacy of zirconia implants. To enhance the osseointegration of zirconia implants, titania (TiO2) coating is prepared on the zirconia surface by immersion in a mixed zirconium oxychloride (ZrOCl2) and TiO2 suspension in a water bath. The surface and longitudinal section morphology are observed by scanning electron microscopy (SEM). The chemical composition is evaluated through energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The roughness and hydrophilicity of zirconia surface are also examined. A three-point bending test is conducted on the samples to explore the effect of this surface treatment on the mechanical strength of zirconia. Vickers hardness measurements are performed to evaluate the gradient change of the longitudinal section of the zirconia substrate. The MC3T3-E1 cells are seeded on zirconia discs, and a LIVE/DEAD double-staining test is conducted to detect the cytotoxicity of the TiO2 coating. The cell morphology is studied through fluorescence microscope. The degrees of cell proliferation, mineralization and alkaline phosphatase (ALP) activity are calculated and compared. Detection of the mRNA expression of osteogenic differentiation-related markers is performed by RT-PCR. A TiO2 coating is generated on the zirconia surface and significantly improves the surface roughness and hydrophilicity while not adversely affecting the mechanical strength of zirconia. The hardness of the zirconia substrate shows a gradient change. The TiO2 coating can promote proliferation, spreading and osteogenic differentiation of MC3T3-E1 cells. These findings suggest that modifying the surface of zirconia with a TiO2 coating may have a favourable osteogenic effect.

RNA-seq reveals correlations between cytoskeleton-related genes and the osteogenic activity of mesenchymal stem cells on strontium loaded titania nanotube arrays.

Strontium loaded titania nanotube arrays (NTSr), as well as titania nanotube arrays (NT), have been regarded as effective coatings to promote bone regeneration on titanium implants, but an understanding of the full extent of early processes affected by such surface modifications is absent. To address this limitation, we performed RNA sequencing (RNA-seq) of Sprague-Dawley rat bone marrow mesenchymal stem cells (rBMMSCs) cultured on unmodified titanium sheets (Con), NT and NTSr specimens. By pairwise comparisons we found that NT and NTSr shared a majority of differentially expressed genes. The Gene Ontology (GO) analysis revealed that NT and NTSr up-regulated a bunch of genes that are annotated to the cytoskeleton. The results were supported by immunofluorescent, transmission electron microscopy (TEM) and western blotting assays. By inhibiting the cytoskeleton through pharmacological agents, the activities of alkaline phosphatase (ALP) on NT and NTSr were also suppressed. Informed by these results, we concluded that NT and NTSr specimens reorganized the cytoskeleton of cultured cells that may play a crucial role in osteogenic lineage commitment.

In Situ Synthesized Particulates on a Zirconia Ceramic Surface and Their Effect on Bonding to Porcelain.

PURPOSE: To explore the effect of in situ synthesized particulates on a zirconia surface on the bonding properties between zirconia and porcelain. MATERIALS AND METHODS: Presintered yttrium-stabilized tetragonal zirconia (Y-TZP) was cut into slices and bars and polished with 1,200-grit silicon carbide abrasive paper. Samples were randomly divided into six groups (C, I1, I3, I5, I7, and I9) according to immersion time in hydrofluoric acid solution (0, 10, 30, 50, 70, and 90 seconds, respectively). Then, the samples were placed in calcium chloride solution for 90 seconds and dipped in sodium hydroxide solution at 80°C for 2 hours. After sintering, the surface topography and roughness were examined. After the porcelain was fired, the bonding interface was observed, and cross-sectional microhardness was measured. The shear bond strength of the zirconia to porcelain was evaluated, and failure modes were classified. A 3-point bending test was applied to confirm the effects of the treatment on the mechanical properties. The above data were statistically analyzed. RESULTS: Polycrystalline particulates were synthesized on the zirconia surface. The surface roughness values increased as the immersion time of the samples in hydrofluoric acid increased. The cross-sectional microhardness decreased gradually in the experimental groups. Group I7 showed an elevated bond strength (27.02 ± 2.44 MPa). Mainly mixed failure mode was obtained in the experimental groups. The Weibull characteristic strength for the experimental groups was higher than that of group C. The flexural strengths were not significantly different among the groups. CONCLUSIONS: In situ synthesized polycrystalline particulates on zirconia could effectively improve the bonding between zirconia ceramics and porcelain without significantly decreasing the mechanical properties.

Improvement of Pit-and-Fissure Sealant Bonding to Enamel with Subpressure Treatment.

This research evaluated the effects of subpressure on the shear bond strength (SBS) of 80 specimens with flat enamel surfaces and on AgNO3 microleakage of 40 specimens with flat enamel surfaces and 40 specimens with 1 mm deep cavities before and after thermocycling. The enamel of 168 specimens was grounded to a flat surface. Two types of sealants (E and H) were selected. Sealants were applied to enamel surface (88 specimens, group F) either subjected or not to subpressure. The bonding interfaces were observed using scanning electron microscopy (SEM) and the SBS was examined using a universal testing machine before and after thermocycling. The failure mode was also analyzed. For the microleakage test, 80 specimens were grouped as group A (original enamel flat surface) and group B (a round cavity of 1 mm in depth) (40 per group). Sealants were applied to the teeth either subjected or not to subpressure. The specimens were submitted to a microleakage protocol with AgNO3 and analyzed before and after thermocycling. Statistical analysis was performed for the data. The results showed that subpressure eliminated voids on the interface between the enamel and sealants and significantly enhanced specimens' SBS. Although thermocycling reduced SBS significantly, specimens under subpressure after thermocycling still showed higher SBS than specimens under nonsubpressure before thermocycling. The subpressure groups showed a lower microleakage level compared to nonsubpressure groups, though thermocycling caused deeper silver infiltration. In addition, different sealants showed no significant effect on the SBS and microleakage performance. Overall, subpressure application improves sealant bonding and retention rate and has potential to prevent secondary caries.

Ca-P spots modified zirconia by liquid precursor infiltration and the effect on osteoblast-like cell responses.

Ca-P spots modified zirconia by liquid precursor infiltration and the cell responses were investigated. Pre-sintered zirconia specimens were immersed in Ca-P precursor solution. After dense sintering, scanning electron microscopy showed Ca-P spots were formed on the zirconia and anchored with zirconia substrates. The distribution density was increased with the extension of immersion time. Energy dispersive spectrometer confirmed the stoichiometric Ca/P ratio was about 1.67. After hydrothermal treatment, Ca-P spots turned into rod crystals where diffraction peaks of tricalcium phosphate and hydroxyapatite were detected by X-ray diffraction, and Ca2+ and PO43- release decreased slightly (p>0.05). There was no significant decrease on three-point bending strength (p>0.05). Osteoblast-like MC3T3-E1 cells attached and spread well and showed higher proliferation on Ca-P spots modified zirconia (p<0.05), though its initial alkaline phosphatase activity was not significant high (p>0.05). In conclusion, Ca-P liquid precursor infiltration is a potential method to modify the zirconia ceramics for improving bioactivity.

Improvement of Total Etching Dentin Bonding with Subpressure.

This study aimed to investigate the effects of subpressure on the bond properties of total-etching adhesive to dentin. Thirty-six caries-free premolars were sectioned parallel to the occlusal plane and randomly divided into four groups (n = 9): a control group (C, no treatment) and three subpressure groups, which were treated under 0.8, 0.6 or 0.4 bar after applying adhesives, named S8, S6 and S4, respectively. Afterward, resin was bonded to the dentin surface, and 27 beams (1.0 mm × 1.0 mm) of each group were sectioned. One was selected to observe the bonding interface from each group by SEM. Each group was divided into two subgroups (n = 13): 24 hours of water storage (I) and 10,000 thermocycling (A). The microtensile bond strength (µTBS), failure modes and nanoleakage expression were evaluated. SEM results showed that the subpressure groups had longer and denser resin tags. The µTBS of the subpressure groups was higher than that of the control group (p < 0.05). The subpressure groups were dominated by mixed failure, whereas main interfacial failure appeared in group C. The subpressure groups showed less silver deposition than the control group (p < 0.05). The subpressure technique may remarkably improve bonding strength and decrease nanoleakage on total-etching bonding.

The effect of subpressure on the bond strength of resin to zirconia ceramic.

OBJECTIVE: This study was conducted to investigate the effect of subpressure on the bond strength of resin to zirconia ceramic. The subpressure would create a pressure gradient which could clean out the bubbles in the adhesives or bonding interface. METHODS: Twenty-eight pre-sintered zirconia discs were fabricated. Half of them were polished (group P, n = 14), and the rest were sandblasted (group S, n = 14). After sintered,the surface roughness of the zirconia discs was measured. Then, they were randomly divided into two subgroups (n = 7). The groups were named as follows: PC: P + no additional treatments; PP: P + 0.04 MPa after application of adhesives; SC: S + no additional treatments; and SP: S + 0.04 MPa after application of adhesives. Resin columns were bonded to the zirconia specimens to determine shear bond strength (SBS). The bonding interfaces were observed and the fracture modes were evaluated. Statistical analysis was performed on all data. RESULTS: The surface roughness of group S was significantly higher than that of group P (P<0.05). The SBS values were PC = 13.48 ± 0.7 MPa, PP = 15.22 ± 0.8 MPa, SC = 17.23 ± 0.7 MPa and SP = 21.68 ± 1.4 MPa. There were significant differences among the groups (P<0.05). Scanning electron microscopy (SEM) results showed that the adhesives of group SP and PP were closer and denser to the zirconia ceramic than that of group PC and SC. The proportion of the mixed fracture mode significantly increased after adding subpressure (P< 0.05). CONCLUSION: Subpressure can improve the shear bond strength of resin to zirconia ceramics and increase micro-infiltration between the adhesives and the zirconia ceramics, especially on the rough surfaces.

Effect of airborne-particle abrasion of presintered zirconia on surface roughness and bacterial adhesion.

STATEMENT OF PROBLEM: Factors associated with implant periodontal disease of zirconia restorations such as surface roughness remain largely unknown. PURPOSE: The purpose of this study was to investigate how airborne-particle abrasion before sintering affects roughness and bacterial adhesion on the surface of zirconia. MATERIAL AND METHODS: Thirty presintered zirconia specimens were divided into 6 groups of 5 after being polished with silicon carbide paper (1200 grit). A different surface treatment was applied to each group (no treatment [group Ct] and 120-µm alumina abrasion for 5, 8, 10, 12, and 15 seconds [A5s, A8s, A10s, A12s, and A15s]), and the specimens were then densely sintered. The mean centric linear roughness (Ra) was measured, and the 3D measurement of surface roughness (3D roughness) was determined. The number of colony forming units (CFUs) of Streptococcus mutans adhering to the surface was also examined. One-way ANOVA was used for data analysis (α=.05). RESULTS: Airborne-particle abrasion before sintering significantly increased surface roughness. Group A8s, A10s, A12s, and A15s showed statistically significant higher CFU/mL than did group A5s (P<.05). No difference was found in CFU/mL between group Ct and A5s (P=.230). CONCLUSIONS: Airborne-particle abrasion before sintering is a useful method of increasing the surface roughness of zirconia. Ra < 0.58 µm is necessary to inhibit the adherence of S. mutans to zirconia.

Effect of sandblasting on surface roughness of zirconia-based ceramics and shear bond strength of veneering porcelain.

This study aims to investigate the effect of sandblasting on the surface roughness of zirconia and the shear bond strength of the veneering porcelain. Pre-sintered zirconia plates were prepared and divided into four groups. Group A were not treated at all; group B were first sandblasted under 0.2 MPa pressure and then densely sintered; group C and D were sintered first, and then sandblasted under 0.2 MPa and 0.4 MPa pressures respectively. Surface roughness was measured and 3D roughness was reconstructed for the specimens, which were also analyzed with X-ray diffractometry. Finally after veneering porcelain sintering, shear bond tests were conducted. Sandblasting zirconia before sintering significantly increased surface roughness and the shear bond strength between zirconia and veneering porcelain (p<0.05). Sandblasting zirconia before sintering is a useful method to increase surface roughness and could successfully improve the bonding strength of veneering porcelain.

[Comparison of bonding properties of five adhesives in primary dentin].

OBJECTIVE: To evaluate the microtensile bond strength (µTBS) of five dentin adhesives and their respective fracture modes. METHODS: The flat dentine surfaces of 75 primary teeth were randomly divided into five groups,which was treated with FL-BondII(group A), Clearfil Protect Bond(group B), Clearfil SE Bond(group C), Adper(TM) Easy One(group D), and Single Bond 2(group E) respectively. The µTBS was determined with microtensile tester and the fracture mode was observed by scanning electron microscope(SEM). RESULTS: The mean µTBS for group A,B,C,D and E was (28.3 ± 2.2), (32.4 ± 2.5), (38.3 ± 2.8), (32.9 ± 3.4) and (23.2 ± 1.9) MPa respectively. There was significant difference between group C and group A,E (P < 0.01), and no significant difference between group C and group B,D. There was no significant difference between group A and group E (P > 0.05). The SEM indicated that there was no significant difference in the fracture mode. CONCLUSIONS: The bonding property of Clearfil Protect Bond is equivalent to Clearfil SE Bond and Adper(TM) Easy One, superior to Single Bond 2 and more suitable for primary dentin bonding .