The purpose of this study was to evaluate the influence of storage temperature and flask agitation on the water sorption (WS) and solubility (SL) of simplified adhesive systems. Seventy-two disc-shaped specimens were prepared according to the adhesive system (water/ethanol-based: Adper Single Bond 2; and water-based: One Coat Bond SL) and experimental conditions tested (mechanical agitation and storage temperature). Statistical analysis (3-way ANOVA, alpha=5%) found significantly greater WS and SL means for the water/ethanol-based system when compared to the water-based. Irrespective of factors studied, significant differences in WS and SL were noted between cold and room temperatures, with greater values been obtained at 1°C, and lower ones at 20°C. Agitation provided increased WS for both materials at all temperatures, but did not affect their SL. The mechanical agitation of the flask may negatively affect the dynamics of diffusion of simplified adhesive systems, even at extremely cold or warm temperatures.
To investigate the influence of different fabrication methods of three-unit reinforced polyetheretherketone composite (PEEK/C) fixed dental prostheses (FDPs) on fracture load. Forty-five three-unit anatomically supported PEEK/C FDPs were fabricated as follows: i. milled using a CAD/CAM system from an industrially fabricated PEEK/C blank, ii. pressed from industrially fabricated PEEK/C pellets, and iii. pressed from granular PEEK/C. Fracture load was measured and data were statistically analysed (p<0.05). CAD/CAM fabricated FDPs (2,354 N) presented a higher mean fracture load than those pressed from granular PEEK/C material (1,738 N) (p<0.001). CAD/CAM milled FDPs and those pressed from PEEK/C-pellets showed spontaneous and brittle fractures near the pontic without deformation of the FDP. In contrast, granulate pressed FDPs showed some plastic deformation without fracture. CAD/CAM fabricated FDPs, and FDPs pressed from PEEK/C pellets showed higher Weibull moduli compared to FDPs pressed in granular form. Industrial pre-pressing of blanks (CAD/CAM/pellet) increased the stability and reliability of PEEK restorations.
Radiopacity is an important property of composite materials for clinical diagnosis. For seven direct composites (Aelite LS Posterior, Aelite All-Purpose Body, Quadrant Universal LC, Clearfil Majesty Posterior, Clearfil Majesty Esthetic, Filtek Ultimate Dentin, IPS Empress Direct Dentin) and six indirect composites (Ceromega, Epricord, Estenia C&B, Tescera, Signum Ceramis, Solidex), diskshaped specimens (N=260, n=10 per group) were fabricated for two thicknesses at 1 and 2 mm. Average radiographic density of each composite material was calculated. Radiopacity values of specimens were expressed in equivalent thickness of aluminum using the calibration curve. Data were analyzed using one-way and two-way ANOVA, followed by Tukey’s HSD test (α=0.05). Radiopacity was significantly affected by resin composite type (p<0.05) and thickness (p<0.001). All composites, except Epricord (1.22–1.84), had higher radiopacity values than dentin (1.23–2.24). IPS Empress Direct (5.58–9.38) and Estenia C&B (5.49–9.16) showed significantly higher radiopacity (p<0.05) than the other materials including enamel and dentin.
The clinical applicability of CAD/CAM-fabricated zirconia copings is tested using working models made from four different highstrength Type IV gypsum materials. Each of the four materials was used to fabricate 15 zirconia copings. Precision of fit was measured with a digital electron microscope using the silicone replica technique. The mean and standard deviation of each reference point were analyzed using the one-way analysis of the variance (ANOVA) and Tukey’s honest significant difference (HSD) tests (α=0.05). The overall marginal and internal fits of the zirconia copings were as follows: GS (GS: Grey Stone) group: 91.43 μm, LS (LS: Light green Stone) Group: 87.89 μm, RS (RS: Red Stone) Group: 88.75 μm, BS (BS: Beige Stone) Group: 82.78 μm. There were no significant differences between the mean adaptations of the gypsum varieties (p>0.05). This confirmed that the type of gypsum material used does not determine the precision of fit of a prosthesis.
The aim of this study was to evaluate and compare the effects of resin infiltration and sealant type on enamel surface properties and Streptococcus mutans adhesion to artificial enamel lesions. Artificial enamel lesions were produced on the surfaces of 120 enamel specimens, which were divided into two groups: Group A and Group B (n=60 per group). Each group was further divided into four subgroups (n=15 per subgroup) according to sealant type: Group I–Demineralized enamel (control); Group II–Enamel Pro Varnish; Group III–ExciTE F; and Group IV–Icon. In Group A, hardness and surface roughness were evaluated; in Group B, bacterial adhesion was evaluated. Icon application resulted in significantly lower surface roughness and higher hardness than the other subgroups in Group A. In Group B, Enamel Pro Varnish resulted in lowest bacterial adhesion, followed by Icon. This study showed that resin infiltration of enamel lesions could arrest lesion progress.
Dentin hypersensitivity is treated using materials that occlude the dentinal tubules or release potassium ions that induce nerve desensitization. In this study we formulated a novel varnish containing potassium chloride and fluoridated hydroxyapatite and evaluated its physical properties and cytotoxicity. Potassium ion release from the varnish was measured. Dentin permeability was evaluated by measuring the hydraulic conductance of etched dentin discs treated with the varnish. The direct contact test and MTT assay were performed to evaluate the varnish’s cytotoxicity. We found that the varnish released potassium ions over 6 h, and demonstrated a statistically higher reduction in dentin permeability compared to commercial fluoride varnish or control. Dentin disc scanning electron microscopy images demonstrated occluded dentinal tubules in the novel varnish group after brushing. The cytotoxicity tests indicated the varnish was biocompatible with gingival and pulpal fibroblasts. We propose the novel varnish is a potential material for use in hypersensitivity management.
This in vitro study compared the shear bond strength (SBS) and adhesive remnant index (ARI) of two systems for bonding orthodontic brackets to enamel. The first system involved a self-etching primer (Beauty Ortho Bond, BO) containing surface pre-reacted glass filler. The second involved a primer applied with phosphoric acid etching (Transbond XT, TX). Ninety-six extracted human premolars were divided into eight groups: Group I (TX/direct bonding), Group II (TX/indirect bonding), Group III (BO/direct bonding), and Group IV (BO/indirect bonding). Groups V-VIII were identical to Groups I–IV, respectively, but were also subjected to 1,500 thermal cycles between 5 and 55°C. ARI was scored by binocular microscopy. SBS was analyzed by three-way ANOVA and the Bonferroni test. ARI was analyzed by the chi-squared test. The BO groups showed lower SBS and ARI results than the TX groups. SBS was significantly influenced by the primer material, bonding technique, and thermal cycling.
If impression materials could be immersed in disinfectant solutions for a longer period, then this form of disinfection would be easier to incorporate into dental preparation procedures. This study investigated the dimensional changes in stone models resulting from immersion of medium-viscosity hydrophilic addition-type silicone rubber impression material in disinfectant solutions for 30 min and 24 h. Impressions of a master die designed to simulate a full crown preparation with adjacent teeth were immersed in 2% glutaraldehyde and 0.55% ortho-phthalaldehyde solutions. The dimensional changes in the mesiodistal and buccolingual dimensions in the stone models were then measured using a three-dimensional coordinate system. It was found that the dimensional changes in the stone models caused by immersion of the impression materials were less than 15 μm. Immersion in 2% glutaraldehyde or 0.55% ortho-phthalaldehyde for 24 h was as clinically acceptable for medium-viscosity hydrophilic addition-type silicone rubber impressions as immersion for 30 min.
Ag-loaded mesoporous bioactive glass (Ag-MBG) powders were synthesized and characterized. The ions release of Ag-MBGs in Tris-HCl and the pH stability of simulated body fluids after immersing Ag-MBGs were tested. Root canals were inoculated with Enterococcus faecalis for 4 weeks, and the antibacterial activity of MBGs, Ag-MBGs and calcium hydroxide against E. faecalis biofilm were evaluated. Results showed that Ag-MBGs possessed highly ordered mesoporous structure with silver nanoparticles deposited in the mesopores, which enabled a sustained Ag ionsreleased. The biofilms treated with Ag-MBGs showed a significant structural disruption compared with MBGs. These results indicated that Ag-MBGs possess a potent antibacterial effect against E.faecalis biofilm in root canal, and the antibacterial activity was induced by the release of Ag ions from Ag-MBGs.
The purpose of this study was to evaluate the microtensile bond strength (µTBS) of a newly developed resin cement, ECD-89 (ECD, Tokuyama Dental, Tokyo, Japan) to dentin and to observe the interfacial micromorphology by comparing with two commercial resin cements, Multilink Automix (MA, Ivoclar Vivadent AG, Schaan, Liechtenstein) and Panavia F2.0 (PF, Kuraray Noritake Dental, Tokyo, Japan). Flat dentin surfaces of human third molars were exposed using #600 SiC. After application of primer and cement to the dentin surface, each cement was applied and cured with light (light condition) or without light (dark condition). The teeth were sectioned to obtain beams (1 mm×1 mm) after 24 h of water storage. The mean bond strengths and SDs (MPa) were: ECD: 68.6±14.9, MA: 39.2±18.9, PF: 39.4±18.5 and ECD: 54.5±22.4, MA: 36.7±15.6, PF: 13.4±4.46 when cured in light and dark condition, respectively. In both conditions, ECD-89 showed statistically higher µTBS than the others.
The influence of monomer content on the viscoelasticity, water sorption and solubility of experimental fluorinated soft lining materials was investigated. Changes in the viscoelastic properties of the materials were also examined after thermal cycling. Four fluorinated soft lining materials containing different amounts of methoxy diethylene glycol methacrylate (MDGMA) and tridecafluorooctyl methacrylate (13FMA) were prepared. The viscoelastic displacement for specimens containing 13FMA was found to be less than that without 13FMA (p<0.05), and the values tended to decrease with increasing 13FMA content. Reduction of the MDGMA content and addition of 13FMA caused a decrease of water sorption and solubility (p<0.05). Thermal cycling was found to affect the viscoelastic deformation of the specimens without 13FMA and those specimens with relatively large amounts of 13FMA.
An appropriate physical support provided by scaffolds creates a supportive environment that directs proliferation and differentiation of stem cells. However, it is difficult to homogenously inoculate stem cells into the inner part of scaffolds at high cell densities. In this study, mesenchymal stem cells were seeded into a hydroxyapatite/poly (D, L-lactic-co-glycolic acid) (HAP/PLGA) scaffold that had enough mechanical strength and porous 3-D structure. With an aid of a filter paper placed under the bottom of a HAP/PLGA block, the cells suspended in a culture medium flowed from the top to the bottom through interconnected pores in the scaffold, and distributed almost homogenously, as compared to cell distribution near the surface of the block by the conventional method using centrifugation or reduced pressure. This simple method with a filter paper may be useful in preparation of cell-scaffold complexes for tissue engineering.
The aim of this study was to evaluate the effects of different surface preparation methods on the shear bond strength (SBS) of orthodontic metal brackets to aged nano-hybrid resin composite surfaces in vitro. A total of 100 restorative composite resin discs, 6 mm in diameter and 3 mm thick, were obtained and treated with an ageing procedure. After ageing, the samples were randomly divided as follows according to surface preparation methods: (1)Control, (2)37% phosphoric acid gel, (3)Sandblasting, (4)Diamond bur, (5)Air-flow and 20 central incisor teeth were used for the control etched group. SBS test were applied on bonded metal brackets to all samples. SBS values and residual adhesives were evaluated. Analysis of variance showed a significant difference (p<0.001) between the groups. Sandblasted group had the highest SBS value (12.85 MPa) in experimental groups. The sandblasting surface treatment is recommended as an effective method of bonding orthodontic metal brackets to nano-hybrid composite resin surfaces.
Influences of contamination and cleaning methods on the bonding of resin cement to zirconia ceramics were examined. Airborne particle-abraded zirconia (IPS e.max ZirCAD) specimens were contaminated with saliva and cleaned with tap water (SC) or by application of 37% phosphoric acid (PA), Ivoclean (IC), or additional airborne particle abrasion (AB). Specimens without contamination served as controls. After application of Monobond Plus to the surface of the specimens, resin cement was mixed and inserted into a mold. Surface free energies of the specimens were determined by measuring contact angles. Surface treatment and storage conditions significantly influenced bond strength, while there was no significant interaction between the two factors. Surface free energies of the SC and IC groups were significantly lower than those of the other groups. Additional AB of saliva-contaminated zirconia increased the strength of bonding with the resin cement as well as increased surface free energy.
Optical coherence tomography (OCT) is an interferometric imaging technique. This study aimed to employ OCT to evaluate four different resin-based materials including a coating containing glass-ionomer filler and calcium, a giomer, and two fluoride-releasing self-etch resins. The coating and its underlying and adjacent enamel were monitored using swept-source OCT (center wavelength: 1330 nm) at baseline, after 5,000 thermal cycles, and after 1, 4 and 7 days of demineralization (pH 4.5). The coatings showed different thicknesses (60–250 micrometers) and various levels of structural and interfacial integrity. OCT could detect a demineralization inhibition zone adjacent to the edge of the fluoride- and calcium-releasing material. Localized demineralization was occasionally observed under thinner coatings. Protection of susceptible enamel surfaces by thin resin-based bioactive coatings provides protection from demineralization. OCT can be used to non-destructively monitor the integrity of such coatings, as well as enamel changes beneath and adjacent to them.
The purpose of this study is to detect the effect of gallic acid (GA) on hydroxyapatie crystal growth and find the mechanism of the regulation. We evaluated the morphology of HAP crystals grown under various amounts of GA (0, 0.05, 1, and 4 gL−1). Subsequently, the chemical composition, crystal size and the morphology were investigated via the energy-dispersive X-ray spectrometer, attenuated total fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction analysis, transmission electron microscope and scanning electron microscopy. In all groups, the Ca/P ratio was closed to 1.67. In the absence of GA, crystals did not arrange, while in the presence of GA, crystals tended to form spherules. The size of the crystals decreased with the concentration of GA increased. These results indicated the role of GA on the growth and morphology of hydroxyapatite crystals, which might be the key mechanism for gallic acid regulating the mineralization.
Most orthodontic equipment is fabricated from alloys such as stainless steel, Co-Cr and Ni-Ti because of their excellent elastic properties. In recent years, increasing esthetic demands, metal allergy and interference of metals with magnetic resonance imaging have driven the development of non-metallic orthodontic materials. In this study, we assessed the feasibility of using three super engineering plastics (PEEK, PES and PVDF) as orthodontic wires. PES and PVDF demonstrated excellent esthetics, although PEEK showed the highest bending strength and creep resistance. PEEK and PVDF showed quite low water absorption. Because of recent developments in coloration of PEEK, we conclude that PEEK has many advantageous properties that make it a suitable candidate for use as an esthetic metal-free orthodontic wire.
The purpose of this study was to investigate the influence of superhydrophilic treatments of titanium on the behavior of osteoblastlike cells. Superhydrophilic specimens were prepared with sandblast and acid-etching (DW), oxygen plasma (Plasma) and ultraviolet light (UV), and were stored in distilled water for 3 days immediately after these treatments. Specimens stored in air for 3 weeks were used as a control Air group. Initial cell attachment, proliferation, alkaline phosphatase activity, and osteocalcin secretion of mouse osteoblast-like cells MC3T3-E1 were enhanced more on superhydrophilic groups than were Air specimens. On confocal laser scanning microscope images of cell morphology, the expression of actin filaments was observed on the superhydrophilic groups, whereas relatively little actin filament expression was seen on the Air surfaces on all culture periods. These results indicate that DW, Plasma, or UV treatment has potential for the creation and maintenance of superhydrophilic surfaces and the enhancement of the initial attachment, proliferation, and differentiation of osteoblast-like cells.