Resistance of ten contemporary adhesives to resin-dentine bond degradation

OBJECTIVES: To evaluate resin-dentine bond degradation after 1 year of water storage. METHODS: Human dentine surfaces were bonded with two etch-and-rinse self-priming adhesives (Single Bond/SB and Prime & Bond NT/PBNT), three 2-step self-etching adhesives (Clearfil SE Bond/SEB, Resulcin Aqua Prime/RES and Non-Rinse Conditioner with Prime & Bond NT/NRC-PBNT), and five 1-step self-etching adhesives (Etch & Prime 3.0/EP, Prompt L-Pop/PLP, Solist/SOL, Futurabond/FUT and AQ Bond/AQ). Adhesives were applied according to manufacturers' instructions. Composite build-ups were constructed and the bonded teeth were stored (24 h, 6 months, 1 year) in distilled water at 37 degrees C. After storage, the intact teeth were sectioned into beams and all specimens were tested for microtensile bond strengths (MTBS). ANOVA and multiple comparisons tests were applied at alpha = 0.05. Fractographic analysis of debonded beams was performed using scanning electron microscopy. RESULTS: SB, PBNT and SEB attained the highest MTBS, regardless of the storage period. A significant decrease in MTBS was observed after 6 months for SOL. After 12 months the only groups that did not reduce bond strength were SB and SEB. Bonded specimens in NRC-PBNT, RES and FUT produced pre-testing failures after 12 months, and MTBS could not be measured. CONCLUSIONS: The resistance of resin-dentine bonds to degradation is material-dependent. When the enamel-resin interface is preserved, the etch-and-rinse adhesives and the mild 2-step self-etch adhesive SEB exhibited the best resin-dentine bond durability. Those tested self-etching adhesives having a pH < or 1 and using water or acetone as solvent attained catastrophic bond failure after 1 year of water storage.     

Dentine remineralization induced by two bioactive glasses developed for air abrasion purposes

Objectives

The present study aimed to evaluate dentine remineralization through a 7-day period of artificial saliva (AS) storage induced by bioactive glass 45S5 (BAG) and by bioactive glass modified with soda-lime spherical glass.

Methods

Partially demineralized dentine disks were treated by BAG or the spherical-glass modified bioactive glass (M-BAG) and subsequently immersed in AS for 7 days. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) was used to quantitatively analyse the mineral variation of the dentine surface by calculating the spectra parameters. X-ray diffraction (XRD) and energy-dispersive X-ray analysis (EDX) were performed on completely demineralized dentine to confirm the apatite formation. The roughness of the dentine surface was evaluated by atomic force microscopy (AFM) and the morphology was also examined by scanning electron microscopy (SEM).

Results

ATR-FTIR showed a significant increase of the mineral matrix area ratio in dentine specimens treated with the two bioactive glasses subsequent to 7 days of AS storage. The XRD spectrum exhibited apatite growth and mineral elements could be found on completely demineralized samples analysed by EDX after remineralization treatments. The dentine specimens treated with bioactive glass showed lower roughness, and most of the dentinal tubules appeared completely occluded during the AFM and SEM examination.

Conclusions

Although the concentration of bioactive glass in the M-BAG is 60% of that contained in the original version, both formulations have similar potential in dentine remineralization. These bioactive powders developed for air-abrasive use may be considered as innovative bioactive materials for therapeutic remineralization of dental hard tissues.     

MMPs activity and bond strength in deciduous dentine–resin bonded interfaces

Objectives

To determine effect of ageing on deciduous dentine–resin interfaces bond strength and the metalloproteinases (MMPs) activity at the hybrid layer compared to permanent dentine.

Methods

Microtensile bond strength (MTBS) tests were performed in human deciduous and permanent dentine after 24 h, 3 and 6 months using an etch and rinse adhesive. C-terminal telopeptide concentrations (ICTP) were calculated, in order to determine MMPs mediated collagen degradation at the hybrid layer.

Results

The highest MMPs-mediated collagen degradation values occurred in phosphoric acid demineralized dentine, ICTP values were similar for deciduous and permanent dentine after 1 week. Resin infiltration decreased collagen degradation in both dentins and ICTP values were similar to those attained by for untreated dentine. In resin infiltrated and untreated dentine specimens collagen degradation was always higher for deciduous dentine. At 24 h, MTBS was higher in permanent dentine. After ageing MTBS decreased and performed similarly in both dentins.

Conclusions

Higher collagenollytic activity is found in deciduous than in permanent dentine. At 24 h, collagen cleavage by MMPs at the hybrid layer is higher in deciduous dentine leading to a lower MTBS.

Clinical significance

The presence of resin monomers reduced collagen degradation when applied on demineralized dentine, but exerted protection was lower in deciduous dentine.     

Influence of air-abrasion executed with polyacrylic acid-Bioglass 45S5 on the bonding performance of a resin-modified glass ionomer cement

The aim of this study was to test the microtensile bond strength (μTBS), after 6 months of storage in PBS, of a resin-modified glass ionomer cement (RMGIC) bonded to dentine pretreated with Bioglass 45S5 (BAG) using various etching and air-abrasion techniques. The RMGIC (GC Fuji II LC) was applied onto differently treated dentine surfaces followed by light curing for 30 s. The specimens were cut into matchsticks with cross-sectional areas of 0.9 mm(2). The μTBS of the specimens was measured after 24 h or 6 months of storage in PBS and the results were statistically analysed using two-way anova and the Student-Newman-Keuls test (α = 0.05). Further RMCGIC-bonded dentine specimens were used for interfacial characterization, micropermeability, and nanoleakage analyses by confocal microscopy. The RMGIC-dentine interface layer showed no water absorption after 6 months of storage in PBS except for the interdiffusion layer of the silicon carbide (SiC)-abraded/polyacrylic acid (PAA)-etched bonded dentine. The RMGIC applied onto dentine air-abraded with BAG/H(2)O only or with BAG/PAA-fluid followed by etching procedures (10% PAA gel) showed no statistically significant reduction in μTBS after 6 months of storage in PBS. The abrasion procedures performed using BAG in combination with PAA might be a suitable strategy to enhance the bonding durability and the healing ability of RMGIC bonded to dentine.     

Effect of surface preparation on the bond strength of heat-polymerized denture base resin to commercially pure titanium and cobalt-chromium alloy

The aim of this study was to investigate the bond durability of heat-polymerized denture base resin to cast CP Ti and Co-Cr alloy. The alloy specimens were divided into five groups: 1) airborne-particle abraded with 50 μm alumina (SAND), 2) Rocatec tribochemical silica coating system (RO), 3) air-abraded followed by application of Epricord Opaque Primer (EP), 4) air-abraded followed by application of Super Bond C&B liquid (SB), 5) air-abraded followed by application of Alloy Primer (AL). Heat-polymerized denture resin was applied to the bonding area and polymerized according to the manufacturer's instructions. The halves of all specimens were thermocycled up to 10,000 cycles. Before thermocycling SB and AL showed significantly higher shear bond strengths than SAND, RO, EP for both metals. The shear bond strength of AL group after thermocycling was significantly higher than that of the other groups.     

化学交联在牙本质粘接修复中的应用及展望

牙本质混合层裸露胶原水解变性是导致树脂粘接修复失败的主要原因。化学交联作用可增加混合层胶原纤维间或纤维内的分子键或氢键结合,提高胶原的机械性能及抗酶解能力,从而改善树脂牙本质粘接修复的耐久性。因此,本文针对化学交联改善树脂牙本质粘接耐久性的机制及其应用效果作一分析探讨。     

A ZnO-doped adhesive reduced collagen degradation favouring dentine remineralization

Objectives

The objective of the study was to determine the efficacy of a ZnO-doped etch and rinse adhesive in decreasing MMPs-mediated collagen degradation at the resin–dentine hybrid layer, and increasing bonding stability.

Methods

C-terminal telopeptide concentrations (ICTP) were determined after 24 h, 1 wk and 4 wk in human dentine beams. Dentine was treated: (1) 37% phosphoric acid for 15 s (PA), (2) PA-etched dentine infiltrated with Single Bond (SB), (3) PA-etched dentine infiltrated with ZnO doped SB (ZnO particles – 10 wt% – were added to the bonding resin) (ZnO–SB), and (4) Clearfil SE Bond primed-dentine was infiltrated with Clearfil SE bonding resin (CSE). Microtensile bond strength (MTBS) was assessed for the different groups at 24 h and after 3 months. Debonded dentine surfaces were studied by scanning electron microscopy.

Results

MMPs-mediated collagen degradation occurred in demineralized dentine (PA). Resin infiltration decreased collagen degradation. The lowest collagen degradation was found for Zn-doped SB, followed by CSE. When these adhesives were applied, ICTP values did not change throughout the study period. At 24 h, similar MTBS was attained for all adhesives. Only SB decreased MTBS after three months.

Conclusions

Addition of ZnO particles to SB produced a reduction in dentine collagen degradation and increased resin–dentine bonds durability. In Zn-doped adhesive interfaces, a calcium phosphate layer and tubular occlusion was encountered at the debonded interface.

Clinical significance

ZnO particles addition into the bonding resin of SB makes a breakthrough to prevent the hybrid layer degradation and to preserve its bonding efficacy overtime.     

One-bottle self-etching adhesives applied to dentine air-abraded using bioactive glasses containing polyacrylic acid: An in vitro microtensile bond strength and confocal microscopy study

ObjectivesThe aim of this study was to test the microtensile bond strength (μTBS) of two “simplified” self-etching adhesives bonded to air-abraded dentine using experimental bioactive glass powders containing polyacrylic acid.MethodsSound dentine specimens were air-abraded using a pure Bioglass 45S5 (Bioglass) powder or two Bioglass powders containing different concentration of polyacrylic acid (PAA: 15 wt% or 40 wt%). The bonding procedures were accomplished by the application of two self-etching adhesives (CS3: Clearfil S3 Bond; Kuraray, Osaka, Japan or GB: G Bond; GC Ltd. Tokyo, Japan). The resin-bonded specimens were cut in beams (0.9 mm²) and the μTBS testing was performed after 24 h or 6 months of phosphate buffer solution (PBS) storage. The results were statistically analysed by three-way ANOVA and Student–Newman–Keuls test used (α = 0.05). Further bonded-dentine specimens were used for the confocal microscopy interfacial characterisation and micropermeability analysis.ResultsThe CS3 adhesive system achieved higher μTBS than those attained in the specimens bonded with GB both after 24 h and 6 months of PBS storage. The CLSM analysis performed after 6 months of PBS storage indicated severe micropermeability within the bonded-dentine interfaces created using GB applied onto dentine air-abraded with Bioglass/PAA-15 and Bioglass/PAA-40. Conversely, CS3 exhibited no dye penetration (micropermeability) at the resin–dentine interface.ConclusionIt is possible to affirm that air-abrasion procedures performed using pure Bioglass or Bioglass containing 15 wt% PAA do not interfere with the immediate bonding performance of self-etching adhesives. However, the durability of the bonded-dentine interfaces created subsequent air-abrasion procedures using bioactive glasses will depend also upon the chemical composition of the self-etch adhesive systems.     

The influence of experimental bioactive glasses on pulp cells behavior in vitro

ObjectivesTo assess in vitro the effect of experimental mesoporous BAG, on human dental pulp cells (hDPCs) behavior in terms of cytocompatiblity and bioactivity via mineralization potential.MethodsFine (FP) and large particles (LP) of a fixed BAG composition named 0NaMBG have been elaborated by a sol-gel process. In vitro assessment was achieved on cultured primary hDPCs using indirect contact. The effect of the concentration of 800 μg/mL on cell metabolic activity and cytotoxicity were examined by performing Alamar blue and crystal violet assays. Alizarin Red staining was used to detect and quantify the formation of mineralized nodules and ALP activity was colourimetrically quantified. The expression of Odontogenic markers: DMP-1 and osteopontin (OPN) expression and cell morphology was evaluated by confocal microscopy.ResultsAccording to the Alamar blue and crystal violet assay, 0NaMBG samples were non-cytotoxic. Cells treated with 0NaMBG particles expressed higher metabolic activity than control cells, especially for LP. Both FP and LP significantly increased both extra and intra cellular ALP activity. hDPCs exhibited good cell spreading and adhesion in the presence of FP and LP extracts by confocal imaging. Further, Alizarin red S assay demonstrated more mineralization nodules and significant enhancement of the extracellular calcium deposition when cells were interfaced with both FP and LP compared to the control cells. Moreover, LP extracts enhanced the production and secretion of odontogenic markers: dentin matrix protein 1 (DMP-1) and osteopontin.SignificanceLP have a higher surface area and pore volume, which could explain their greater bioactivity in contact with pulp cells. The clinical relevance of these findings implicate that 0NaMBG could be used as fillers in dental therapeutic materials suitable for dentin and/or pulp tissues preservation.     

An in vitro comparison of adhesive systems to seal pulp chamber walls

AIM: To compare in vitro the sealing properties of five different dentine adhesive materials (Prime&Bond NT (PBNT); Prompt L-Pop (PLP); Clearfil SE Bond (CSEB); Scotchbond Multi Purpose Plus (SMPP); EBS-Multi (EBSM)) inside the pulp chamber. METHODOLOGY: Seventy-five recently extracted human molar teeth were used. The roof of the pulp chambers and roots were removed under water cooling. Pulp tissue was removed, and the canal orifices were sealed. The pulp chambers were then treated with 5% sodium hypochlorite (NaOCl) for 1 min. The teeth were randomly divided into five groups of 15 teeth each. Adhesive systems were applied to the pulp chamber walls according to the manufacturers' instructions. The samples were connected to Plexiglass plates, and a fluid filtration method was used for quantitative evaluation of leakage. Measurements of fluid movement were made at 2-min intervals for 8 min. The quality of seal of each specimen was measured immediately, after 24 h, 1 week and 1 month. The data were statistically analysed by repeated-measurements multivariate anova, Friedman test, Wilcoxon signed rank test, Kruskal-Wallis of one-way anova and Mann-Whitney U-tests. The pulp chamber wall with and without NaOCl and resin-dentine interfaces of specimens were observed under a scanning electron microscope (SEM). RESULTS: The leakage values of the materials were significantly different at different measurement periods. In all groups, leakage values decreased with time (P < 0.05). PBNT and PLP had the least leakage during immediate measurements (P < 0.05). After 1 month, leakage of all adhesive systems was not significantly different (P < 0.05). SEM observation of pulp chamber walls demonstrated that the irregular dentine surface without smear layer was present in the nontreated group. However, NaOCl application removed the collagen fibrils leaving the dentine surface smooth. At resin-dentine interfaces of specimens, no hybridization zone was observed. CONCLUSIONS: None of the materials had created a perfect seal to the pulp chamber walls. PBNT and PLP had better sealing over the short term, but over the long term, there were no differences between the materials.     

Micropermeability of current self-etching and etch-and-rinse adhesives bonded to deep dentine: a comparison study using a double-staining/confocal microscopy technique

Water sorption decreases the mechanical properties and the bond strengths of resin-bonded dentine. The aim of this study was to evaluate the micropermeability of several self-etching and etch-and-rinse adhesives. Optibond FL, Silorane, Scotchbond 1XT, G-Bond, and DC-Bond were bonded under simulated pulpal pressure. A 10 wt% solution of ammoniacal silver nitrate and a 1 wt% solution of rhodamine B were injected into the pulp chamber at 20 cm of water pressure. The dentine–adhesive interfaces were examined using a confocal scanning microscope. Micropermeability was detected in all the adhesives. DC-Bond, G-Bond, and Scotchbond 1XT showed voids along the resin-bonded interface. Silorane and Optibond FL showed an adhesive layer that was free from water trees and micropermeability. The double staining technique is a method that gives accurate results in the study of the resin-dentine micropermeability. Each class of adhesive has a different distribution of micropermeability. The higher the micropermeability, the higher the risk of defects at the resin–dentine interface, which may represent the pathway for hydrolytic and enzymatic degradation of resin–dentine bonds over time.     

Cytotoxicity of 45S5 bioglass paste used for dentine hypersensitivity treatment

Objectives

45S5 bioglass mixed with 50% phosphoric acid has been suggested to treat dentine hypersensitivity and incipient enamel caries. This study is going to evaluate the biocompatibility of using the aforementioned technique with the rat pulpal cells.

Methods

The relative cytotoxicity of 45S5 bioglass on rat dental pulp cells was compared to the cytotoxicity of a temporary filling material (Caviton; GC, Japan), Type 1 glass ionomer cement (Fuji I; GC, Tokyo, Japan) and commercial desensitising agent (SuperSeal; Phoenix Dental, Fenton, MI, USA) using a transwell insert model. Cell viability was measured by means of a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The number of viable cell counts were compared using one way ANOVA (p < 0.05). The morphological alterations of the pulp cells were observed directly by phase contrast microscope.

Results

The results of this study indicated that cell viability recorded by the 45S5 bioglass paste group did not differ significantly from those of the Caviton, glass ionomer or superseal, moreover pulpal cells microscopic analysis revealed that 45S5 bioglass elicited minimal toxic effect.

Conclusions

45S5 bioglass paste can serve as a biocompatible material that can potentially be used safely on dentine.     

Bioactive effects of a calcium/sodium phosphosilicate on the resin-dentine interface: a microtensile bond strength, scanning electron microscopy, and confocal microscopy study

This study evaluated, through microtensile bond strength (μTBS) testing, the bioactive effects of a calcium/sodium phosphosilicate (BAG) at the resin-dentine interface after 6 months of storage in phosphate buffer solution (PBS). Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) were also performed. Three bonding protocols were evaluated: (i) RES-Ctr (no use of BAG), (ii) BAG containing adhesive (BAG-AD), and (iii) BAG/H (3) PO (4) before adhesive (BAG-PR). The dentin-bonded specimens were prepared for μTBS testing, which was carried out after 24 h or 6 months of storage in PBS. Scanning electron microscopy ultramorphology analysis was performed after debonding. Confocal laser scanning microscopy was used to evaluate the morphological and nanoleakage changes induced by PBS storage. High μTBS values were achieved in all groups after 24 h of storage in PBS. Subsequent to 6 months of storage in PBS the specimens created using the BAG-AD bonding approach still showed no significant reduction in μTBS. Moreover, specimens created using the BAG-AD or the BAG-PR approach showed an evident reduction of nanoleakage after prolonged storage in PBS. The use of BAG-containing adhesive may enhance the durability of the resin-dentine bonds through therapeutic/protective effects associated with mineral deposition within the bonding interface and a possible interference with collagenolytic enzyme activity (matrix metalloproteinases) responsible for the degradation of the hybrid layer.     

Comparison of bioactive glass, mineral trioxide aggregate, ferric sulfate, and formocresol as pulpotomy agents in rat molar

Abstract –  Bioactive glass (BAG) is often used as a filler material for repair of dental bone defects. Although there is evidence of osteogenic potential of this material, it is not clear yet whether the material exhibits potential for dentinogenesis. Hence, the aim of the present study was to evaluate BAG as a pulpotomy agent and to compare it with three commercially available pulpotomy agents such as formocresol (FC), ferric sulfate (FS), and mineral trioxide aggregate (MTA). Pulpotomies were performed in 80 maxillary first molars of Sprague Dawley rats, and pulp stumps were covered with BAG, FC, FS, and MTA. Histologic analysis was performed at 2 weeks and then at 4 weeks after treatment. Experimental samples were compared with contra-lateral normal maxillary first molars. At 2 weeks, BAG showed inflammatory changes in the pulp. After 4 weeks, some samples showed normal pulp histology, with evidence of vasodilation. At 2 weeks, MTA samples showed some acute inflammatory cells around the material with evidence of macrophages in the radicular pulp. Dentine bridge formation with normal pulp histology was a consistent finding at 2 and 4 weeks with MTA. Ferric sulfate showed moderate inflammation of pulp with widespread necrosis in coronal pulp at 2 and 4 weeks. Formocresol showed zones of atrophy, inflammation, and fibrosis. Fibrosis was more extensive at 4 weeks with evidence of calcification in certain samples. Among the materials tested, MTA performed ideally as a pulpotomy agent causing dentine bridge formation while simultaneously maintaining normal pulpal histology. It appeared that BAG induced an inflammatory response at 2 weeks with resolution of inflammation at 4 weeks.     

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pre-treated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). Results: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after NaOClaq immersion. Conclusions: Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups. Key words:CAD/CAM ceramic, alumina, zirconia, resin cement, surface pre-treatment, sandblasting, silica-coating, chemical aging, bond degradation, microtensile bond strength.     

Activation of Transient Receptor Potential Ankyrin 1 and Vanilloid 1 Channels Promotes Odontogenic Differentiation of Human Dental Pulp Cells

IntroductionTransient receptor potential ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) are thermosensitive channels that play an important role in thermal sensation or tooth pain by regulating intracellular Ca²⁺ concentration that is essential for pulp tissue repair. The aim of this study was to evaluate the role of TRPA1 and TRPV1 channels in the odontogenic differentiation of human dental pulp cells (HDPCs).MethodsHDPCs were isolated from healthy human intact third molars and cultured in odontogenic differentiation medium. Gene and protein expression levels of TRPA1 and TRPV1 channels during the odontogenic differentiation of HDPCs were evaluated by real-time quantitative polymerase chain reaction and Western blot analysis. HDPCs were then treated with channel agonists or antagonists, and the expression levels of odontogenic markers dentin sialophosphoprotein (DSPP) and osteopontin (OPN) were examined. Alkaline phosphatase activity and alizarin red staining were also conducted to detect mineralization levels.ResultsConsistent with the mineralization degree and DSPP and OPN expression, messenger RNA and protein expression of TRPA1 and TRPV1 channels was up-regulated during the odontogenic differentiation of HDPCs. The application of TRPA1 or TRPV1 agonists increased the mineralized nodules of alizarin red staining and alkaline phosphatase activity and up-regulated the messenger RNA and protein expression of DSPP and OPN, respectively, with the highest values reached on the seventh day (P < .05). On the contrary, the mineralization level and DSPP and OPN expression could be suppressed by using the antagonists of these 2 channels.ConclusionsTRPA1 and TRPV1 channels not only showed up-regulated expression along with the odontogenic differentiation of HDPCs but also could affect the odontogenic differentiation by regulating intracellular Ca²⁺ concentration.     

Potential Roles of Bone Morphogenetic Protein 9 in the Odontogenic Differentiation of Dental Pulp Cells

IntroductionThe differentiation of dental pulp cells (DPCs) plays an important role in the repair of dental pulp injury. Bone morphogenetic protein 9 (BMP9) is one of the most effective BMPs to induce the differentiation of stem cells. However, the role of BMP9 in promoting the odontogenic differentiation of DPCs and dentinogenesis is worth knowing.MethodsFluorescence in situ hybridization and immunohistochemistry staining were performed to detect the BMP9 expression in human dental pulp. BMP9 was overexpressed in human DPCs (hDPCs), and the mineralization of hDPCs was tested by alkaline phosphatase staining and alizarin red staining. The expression of odontogenic differentiation-related genes was examined by quantitative real-time polymerase chain reaction and western blotting. The subcutaneous transplantation experiment was performed to test the odonto-induction ability of BMP9 in vivo. The rat direct pulp-capping experiment was performed to test the function of BMP9 in promoting dentin formation.ResultsBMP9 showed an increased expression in odontoblast layer at both the mRNA and protein levels. BMP9 enhanced the mineralization and induced the expression of odontogenic differentiation-related genes in hDPCs. More mineralized nodules, and increased expression of dentin sialophosphoprotein (DSPP) and dentin matrix protein-1 (DMP1) were detected in the beta-tricalcium phosphate scaffold/cells composites of BMP9 group compared with the control group. Meanwhile, there was thicker reparative dentin formation in the BMP9 group in the rat pulp exposure experiment.ConclusionsBMP9 participates in the process of DPC differentiation and promotes DPC mineralization and dentinogenesis. BMP9 might be a potential therapeutic target in the repair of dental pulp injury.     

Impact of different pretreatments and aging procedures on the flexural strength and phase structure of zirconia ceramics

ObjectiveTo test the impact of zirconia pretreatment and aging on flexural strength and phase structure.MethodsFor flexural strength measurements, 180 3Y-TZP_0.25 specimens were fabricated and pretreated: (i) air-abraded (105-μm alumina, 0.25 MPa), (ii) air-abraded (50-μm alumina, 0.25 MPa), (iii) air-abraded (30-μm silica-coated alumina, 0.28 MPa) (iv) non-pretreated. Each pretreated group (n = 15) was aged: (a) hydrothermal (134 °C, 0.23 MPa, 2 h) (b) in a mastication simulator (1,200,000×, 5/55 °C) and (c) not aged. The fractured specimens were stored dry for 5 years (23 °C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP_0.25 (n = 12) and 3Y-TZP_0.05 (n = 8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4 MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffé post hoc test and partial-eta-squared (?_p²) (α = 0.05).ResultsThe highest impact on flexural strength was exerted by the pretreatment (η_P² = 0.261, p < 0.001), followed by interactions between pretreatment and aging (η_P² = 0.077, p = 0.033). Non-pretreated and non-aged specimens showed the lowest monoclinic percentage. Hydrothermal aging and 5 years of storage at room temperature increased the monolithic percentage of 3Y-TZP_0.25. The highest phase transformation was observed in groups air-abraded with 105-μm alumina particles. Increasing pressure during the air-abrading process increased the content of the monoclinic phase in zirconia surfaces.SignificanceAir-abrasion with 30-μm silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP_0.25 and 3Y-TZP_0.05. For air-abrasion using alumina powder lower pressure should be used.     

Microtensile bond strength to root canal vs pulp chamber dentin: effect of bonding strategies

PURPOSE: The aim of this in vitro study was to compare the microtensile bond strength (MTBS) between root canal and pulp chamber dentin with two bonding strategies (self-etching primer and total-etch technique). MATERIALS AND METHODS: The pulp chamber of four human canines was accessed and the pulp chamber and root canal prepared with spiral drills. The teeth were cut into halves parallel to the long axis of the tooth and randomly assigned to two groups: Clearfil SE Bond + AP-X(SE) (Kuraray) and SingleBond + Filtek Z250(SB) (3M ESPE). After 24 h in water storage, the specimens were cut perpendicular to the root into 1.0-mm slices with a low-speed diamond saw. Specimens were trimmed to obtain hourglass shapes with a bond area of 1.0 mm2 (n = 12). Three specimens were obtained from the cervical root canal dentin (R) and from the coronal pulp chamber dentin (C). The MTBS was measured in a Bencor device with an Instron machine at a crosshead speed of 0.5 mm/min. The data was analyzed with two-way ANOVA and Tukey LSD post hoc (p < 0.05). RESULTS: MTBS in MPa (mean +/- SD) were: SB.C = 25.3 (+/-6.5)a; SB.R = 16.9 (+/-6.0)b; SE.C = 16.9 (+/-3.4)b; SE.R = 16.8 (+/-5.3)b. Means with the same letter are not statistically different at p < 0.05. When data were pooled for "dentin region", coronal pulp chamber dentin resulted in statistically higher bond strengths than root canal dentin (p < 0.013). CONCLUSION: Bonding to pulp chamber dentin seems to be more predictable than to root canal dentin. In the former region, the total-etch technique may result in a higher bond strength.     

Bone healing with niobium-containing bioactive glass composition in rat femur model: A micro-CT study

ObjectiveThe aim of this study is to investigate bone healing ability of niobium-containing bioactive glasses in rat femur model with quantitative and qualitative measurements through x-ray computed microtomography.MethodsNiobium-containing bioactive powders and scaffolds were produced by sol–gel route (BAGNb). Glasses without niobium addition were produced as well (BAG). Five groups were used: BAGNb powders, BAG powders, BAGNb scaffolds, BAG scaffolds and, as a control group, autogenous bone was used. Materials were implanted in the femur of male rats (Wistar Lineage n = 10) and the healing was observed after 15, 30 and 60 days. After the post-operative times, samples were scanned by X-ray microcomputed tomography where morphometric measurements and the mineral density were assessed in image software.ResultsNo postoperative complications were observed after surgery. BAGNb glasses presented higher mineral deposition, which was observed in the relative volume of bone and the mineral density when compared BAG groups. In these parameters, no statistical difference was found between BAGNb and autogenous bone. The BAGNb powders presented a higher amount of mineralized tissue when compared to BAGNb scaffolds. The analysis of trabecular structure showed lower trabecular formation in synthetic materials when compared to autogenous bone.SignificanceNiobium-containing bioactive glasses promoted bone formation comparable to that of the autogenous bone without compromising the quality of the formed bone.