The current paper reviews the curing mechanisms found in resin-based materials used in dentistry. Historical aspects of dental products and the associated curing mechanisms are reviewed. In ...comparison with common industrial procedures, curing methods employed for dental materials are relatively limited because of the need to polymerize quickly in the oral cavity at an ambient temperature. Heat-cure and self-cure dental resins utilize benzoyl peroxide initiator alone with a tertiary amine co-initiator. At present, most dental restorative composites use a camphorquinone-amine complex initiation, visible light-cure, one-component systems, although alternative photoinitiators have been researched and developed. A multiple curing mode in a dual-cure material is a complex combination of various initiation systems. The use of aryl sulfinic acid sodium salt to overcome adverse chemical interactions between simplified adhesives and self- or dual-cure composites is based on another self-cure polymerization mechanism, sulfinic acid-initiated polymerization, proposed by Hagger in 1948. The sodium salt of aryl sulfinic acid reacts with an acidic monomer in simplified adhesives, and is believed to produce radicals. Clinically, it is important to try to optimize the degree of conversion of resin-based materials using proper manipulation and adequate light-curing techniques to ensure the best outcome for materials used to restore teeth.
This
study was conducted to evaluate the shear bond strength of "non-self-adhesive" resin to dental zirconia etched with hydrofluoric acid (HF) at room temperature and to compare it to that of ...air-abraded zirconia. Sintered zirconia plates were air-abraded (control) or etched with 10%, 20%, or 30% HF for either 5 or 30 min. After cleaning, the surfaces were characterized using various analytical techniques. Three resin cylinders (Duo-Link) were bonded to each treated plate. All bonded specimens were stored in water at 37 °C for 24 h, and then half of them were additionally thermocycled 5000 times prior to the shear bond-strength tests (
= 12). The formation of micro- and nano-porosities on the etched surfaces increased with increasing concentration and application time of the HF solution. The surface wettability of zirconia also increased with increasing surface roughness. Higher concentrations and longer application times of the HF solution produced higher bond-strength values. Infiltration of the resin into the micro- and nano-porosities was observed by scanning electron microscopy. This
study suggests that HF slowly etches zirconia ceramic surfaces at room temperature, thereby improving the resin-zirconia bond strength by the formation of retentive sites.
Abstract Introduction This study examined a clinically feasible protocol for improving hydrolytic stability using a 2-step silanization including a nonorganofunctional silane. Methods The surfaces of ...24 D.T. Light-Posts (Bisco Inc, Schaumburg, IL) were polished and assigned to the following 4 groups: M: 1-step silanization with Monobond-S (MS) (Ivoclar Vivadent, Schaan, Liechtenstein); BM: 2-step silanization with 5% 1,2-bis(triethoxysilyl)ethane and then MS; and HM and HBM: 1-step and 2-step silanization, respectively, after 24% H2 O2 etching. Four resin composite cylinders (RelyX Unicem; 3M ESPE, St Paul, MN) were bonded on each surface according to a microshear testing protocol. All bonded samples were stored in water at 37°C for 24 hours, and half of them were then thermocycled 5000 times before microshear testing ( n = 12). The failure modes were evaluated under an optical and scanning electron microscope. Water contact angles were measured on the post surfaces before and after silanization to estimate surface hydrophobicity. The results were statistically analyzed using 2-way analysis of variance and the Tukey test. Results The bond strengths for the BM and HBM groups were significantly higher than the M and HM groups at 5000 thermocycles ( P < .05), whereas no significant differences were found between the 4 groups before thermocycling ( P > .05). All debonded samples showed some fractured fibers. No significant difference in the hydrophobicity was found between the 1-step and 2-step silanized post surfaces ( P > .05). Conclusions The 2-step 1,2-bis(triethoxysilyl)ethane/MS treatment has potential as a silanization procedure for enhancing the hydrolytic stability of the fiber post/resin composite interface.
This study compared the microstructures and mechanical properties of nickel–chromium–molybdenum (Ni–Cr–Mo) alloys prepared from a single alloy with an identical composition using two new digital ...processes (selective laser melting (SLM) and soft metal milling (SMM)) and conventional lost-wax casting (LWC). Disc specimens were used to study the microstructures via various analytical methods, while dumbbell-shaped specimens were subjected to tension to determine the mechanical properties (n = 6). The SLM and SMM alloys showed a higher number of large and small pores, respectively, than the LWC alloy. A face-centered cubic (γ)-phased matrix was indexed for all three resultant alloys. The SLM and SMM alloys also showed more homogeneously distributed elements and finer grains (in particular, ultrafine grains in the SLM alloy) when compared to the LWC alloy. Meanwhile, the LWC alloy showed a statistically higher yield strength than the other two alloys (p < 0.001). Notwithstanding, all three resultant Ni–Cr–Mo alloys satisfied the ISO 22674 standard criteria for type 5 materials (yield strength: >500 MPa; percentage elongation: >2%; and elastic modulus: >150 GPa).
A preliminary tensile test was performed to evaluate the mechanical properties of cobalt-chromium (Co-Cr) alloys fabricated by three new manufacturing processes: metal milling, milling for soft ...metal, and rapid prototyping (n=6). For comparison, the three alloy materials were also used to fabricate specimens by a casting procedure. In all groups tested, the proof strength and elongation were over 500 MPa and 2%, respectively. The milled soft alloy in particular showed a substantially greater elongation, whereas the alloy fabricated by rapid prototyping exhibited a higher proof strength.
The purpose of this study was to investigate the effect of activation time for the hydrolysis of dental silane primers on resin bonding to ceramic. Two commercial two-part silane primers (Bis-Silane, ...BS; Tokuso Ceramic Primer, TCP) were tested. Leucite-reinforced glass-ceramic (IPS Empress CAD) surfaces were used as the bonding substrates. The degree of hydrolysis of each mixed silane was observed at five specified times (immediately, 10 min, 30 min, 1 h, and 2 h after mixing) using Fourier transform infrared (FTIR) spectroscopy. Prior to resin (Duo-Link) bonding, the polished ceramic surfaces were pretreated with silanes that were activated in two different ways: an 'in-solution' or 'on-surface' activation, at the specified times. All bonded specimens were stored in water at 37 °C for 24 h prior to tensile bond strength (TBS) testing (n = 12). A one-bottle silane (Monobond-S, MS) was also tested. The FTIR analysis showed that the hydrolysis proceeded gradually for 2 h in the BS, but the initial hydrolysis halted in the TCP. When the BS was further hydrolyzed up to 2 h, the TBS values significantly increased up to 30 min (p < 0.001) with no further significant increases (p > 0.05) regardless of the activation method used. For TCP, there were no significant differences in TBS as a function of activation time (p > 0.05). The fractographic analysis of the debonded surfaces was consistent with the TBS data. In conclusion, a lengthened activation time was effective for the BS in enhancing resin bonding efficacy to the ceramic.
This study aimed to investigate the efficacy of cleaning solutions on saliva-contaminated zirconia in comparison to air-abrasion in terms of resin bonding.
For saliva-contaminated airabraded ...zirconia, seven cleaning methods)-no contamination (NC), water-spray rinsing (WS), additional airabrasion (AA), and cleaning with four solutions (Ivoclean IC; 1.0 wt% sodium dodecyl sulfate SDS, 1.0 wt% hydrogen peroxide HP, and 1.0 wt% sodium hypochlorite SHC)-were tested. The zirconia surfaces for each group were characterized using various analytical techniques. Three bonded resin (Panavia F 2.0) cylinders (bonding area: 4.5 mm(2)) were made on one zirconia disk specimen using the Ultradent jig method four disks (12 cylinders)/group; a total of 28 disks. After 5,000 thermocycling, all specimens were subjected to a shear bond strength test with a crosshead speed of 1.0 mm/minute. The fractured surfaces were observed using an optical and scanning electron microscope (SEM).
Contact angle measurements showed that groups NC, AA, IC, and SHC had hydrophilic surfaces. The X-ray photoelectron spectroscopy (XPS) analysis showed similar elemental distributions between group AA and groups IC and SHC. Groups IC and SHC showed statistically similar bond strengths to groups NC and AA (P>.05), but not groups SDS and HP (P<.05). For groups WS, SDS, and HP, blister-like bubble formations were observed on the surfaces under SEM.
Within the limitations of this in vitro study, some of the cleaning solutions (IC or SHC) were effective in removing saliva contamination and enhancing the resin bond strength.
Ti6Al4V substrates were electrochemically deposited with nano-crystalline hydroxyapatite (HA) from aqueous electrolytes. Cathodic HA coatings were obtained when the electrolyte was stirred using ...ultrasonic vibration. Two current densities of 20 mA/cm
and 50 mA/cm
were employed. Polarization and electrochemical impedance spectroscopy (EIS) were the techniques used to estimate the corrosion of coatings in simulated body fluid (SBF). The results indicate good corrosion resistance for the coating obtained at 50 mA/cm
from ultrasonic stirring of the electrolyte.
•A novel antibacterial porous hydroxyapatite scaffold was developed.•Chlorhexidine-loaded albumin nanoparticles were coated with polyethylenimine.•The nanoparticles were well immobilized on the ...scaffold via charge interaction.•The nanoparticle-immobilized scaffold was effective against S. mutans.
A novel antibacterial hydroxyapatite (HAp) scaffold was developed by immobilizing chlorhexidine (CHX)-loaded human serum albumin (HSA) nanoparticles on its surface via surface charge interaction using polyethylenimine (PEI). The CHX-loaded HSA nanoparticles were fabricated using a desolvation method, coated with PEI molecules (PEI-CHX-HSA), and immobilized via charge interaction on the scaffold surface. The PEI-CHX-HSA nanoparticles were observed to be well-dispersed on the scaffold surface. The agar diffusion test showed a clear inhibition zone of Streptococcus mutans around the nanoparticle-immobilized scaffold. The antibacterial activity of the scaffold was also confirmed in the S. mutans adhesion study using scanning electron and fluorescent microscopy. The results suggest that the HAp scaffold with immobilized PEI-CHX-HSA nanoparticles showed effective drug releasing behavior and antibacterial activity against S. mutans.
Incorporating bioactive molecules into synthetic ceramic scaffolds is challenging. In this study, to enhance bone regeneration, a magnesium phosphate (MgP) ceramic scaffold was incorporated with a ...novel indene compound, KR-34893. KR-34893 induced the deposition of minerals and expression of osteoblast marker genes in primary human bone marrow mesenchymal stem cells (BMSCs) and a mouse osteoblastic MC3T3-E1 cell line. Analysis of the mode of action showed that KR-34893 induced the phosphorylation of MAPK/extracellular signal-regulated kinase and extracellular signal-regulated kinase, and subsequently the expression of bone morphogenetic protein 7, accompanied by SMAD1/5/8 phosphorylation. Accordingly, KR-34893 was incorporated into an MgP scaffold prepared by 3D printing at room temperature, followed by cement reaction. KR-34893-incorporated MgP (KR-MgP) induced the expression of osteoblast differentiation marker genes in vitro. In a rat calvaria defect model, KR-MgP scaffolds enhanced bone regeneration and increased bone volume compared with MgP scaffolds, as assessed by micro-computed tomography and histological analyses. In conclusion, we developed a method for producing osteoinductive MgP scaffolds incorporating a bioactive organic compound, without high temperature sintering. The KR-MgP scaffolds enhanced osteoblast activation in vitro and bone regeneration in vivo.
PDF
