Preparation of ZnO Nanoparticle/Acrylic Resin Superhydrophobic Coating via Blending Method and Its Wear Resistance and Antibacterial Properties

Herein, a facile method for the preparation of an acrylic resin-based superhydrophobic coating is provided. Firstly, ZnO nanoparticles were modified with silane to obtain hydrophobic ZnO, which was then homogeneously blended with acrylic resin. Subsequently, the mixture was sprayed on an aluminum sheet to form a cured coating. The surface composition and morphology of the coating were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The hydrophobicity, wear resistance, and antibacterial properties of the prepared samples were tested. The optimized hydrophobicity was achieved with 10 wt% modification agent and resin-to-ZnO mass ratio of 1:4, exhibiting contact and sliding angles of 168.11° and 7.2°, respectively. Wear resistance was insufficient with a low resin content, while it grew with the increase in the resin content. However, when the resin content was excessively high, the hydrophobicity was reduced because the resin could wrap the modified ZnO nanoparticles and decrease the number of hydrophobic groups on the surface. Compared with the pure acrylic resin coating, the ZnO nanoparticle/acrylic resin superhydrophobic coating demonstrated a significant enhancement in the antibacterial properties.     

Minimum Radiant Exposure and Irradiance for Triggering Adequate Polymerization of a Photo-Polymerized Resin Cement

This study aimed to establish the minimum radiant exposure and irradiance to trigger an adequate polymerization of a photo-polymerized resin cement. In total, 220 disc-shaped specimens (diameter of 10 mm and thickness of 0.1 mm) were fabricated using a photo-polymerized resin cement (Variolink N-transparent, Ivoclar Vivadent). To investigate the minimum radiant exposure, the specimens were polymerized with radiant exposures of 1, 2, 3, 4, 5, 6, and 18 J/cm² (n = 20). During polymerization, the irradiance was maintained at 200 mW/cm². To investigate the minimum irradiance, the specimens were polymerized with irradiances of 50, 100, 150, and 200 mW/cm² (n = 20). During polymerization, the radiant exposure was maintained at the previously determined minimum radiant exposure. The Vickers microhardness (HV) and degree of conversion (DC) of the carbon double bond of the specimens were measured to determine the degree of polymerization of the specimens. The results were analyzed using one-way analysis of variance (ANOVA) and Tukey’s test (p < 0.05). In the investigation of the minimum radiant exposure, the HV and DC of the specimens polymerized with a radiant exposure from 1 to 5 J/cm² were significantly lower than those with 18 J/cm² (all p < 0.05). However, no significant difference in HV and DC was found between the specimens polymerized with 6 J/cm² and 18 J/cm² (p > 0.05). In the investigation of the minimum irradiance, the specimens polymerized with an irradiance of 50 mW/cm² had significantly lower HV and DC than the specimens polymerized with an irradiance of 200 mW/cm² (p < 0.05). However, no significant difference in the HV and DC was found among the specimens cured with irradiances of 100, 150, and 200 mW/cm² (p > 0.05). In conclusion, the minimum radiant exposure and irradiance to trigger an adequate polymerization of the light-cured resin cement were 6 J/cm² and 100 mW/cm², respectively.     

Review on Polymer,Ceramic and Composite Materials for CAD/CAM Indirect Restorations in Dentistry—Application,Mechanical Characteristics and Comparison

The aim of this review article is to present various material groups, including ceramics, composites and hybrid materials, currently utilized in the field of CAD/CAM. The described technology is amongst the most important in modern prosthetics. Materials that are applicable in this technique are constantly tested, evaluated and improved. Nowadays, research on dental materials is carried out in order to meet the increasing demand on highly aesthetic and functional indirect restorations. Recent studies present the long-term clinical success of restorations made with the help of both ceramic and composite materials in the CAD/CAM method. However, new materials are developed and introduced that do not have long-term in vivo observations. We can outline a monolithic polymer-infiltrated ceramic network and zirconia teeth support that show promising results to date but require further assessment. The materials will be compared with regard to their mechanical and clinical properties, purpose, advantages and limitations.     

Intravascular stents: a new technique for tissue processing for histology, immunohistochemistry, and transmission electron microscopy

Background—Study of the vascular response to stent implantation has been hampered by difficulties in sectioning metal and tissue without distortion of the tissue stent interface. The metal is often removed before histochemical processing, causing a loss of arterial architecture. Histological and immunohistochemical sections should be 5 µm with an intact tissue stent interface.
Objectives—To identify the most suitable cutting and grinding equipment, embedding resin, and slides for producing thin sections of stented arteries with the stent wires in situ for histological, immunohistochemical, and transmission electron microscopic (TEM) analyses.
Methods—20 balloon stainless steel stents were implanted in the coronary arteries of 10 pigs. Twenty eight days later the stented arterial segments were excised, formalin fixed, embedded in five different resins (Epon 812, LR white, T9100, T8100, and JB4), and sectioned with two different high speed saws and a grinder for histological, immunohistochemical, and TEM analyses. Five stented human arteries were obtained at necropsy and processed using the best of the reported methods.
Results—The Isomet precision saw and grinder/polisher unit reliably produced 5 µm sections with most embedding resins; minimum section thickness with the horizontal saw was 400 µm. Resin T8100, a glycol methacrylate, enabled satisfactory sectioning, grinding, and histological (toluidine blue, haematoxylin and eosin, and trichromatic and polychromatic stains) and immunohistochemical analyses (α smooth muscle actin, von Willebrand factor, vimentin, proliferating cell nuclear antigen, and CD68 (mac 387)). T9100 and T8100 embedded stented sections were suitable for ultrastructural examination with TEM. Stented human arterial sections showed preserved arterial architecture with the struts in situ.
Conclusion—This study identified the optimal methods for embedding, sawing, grinding, and slide mounting of stented arteries to achieve 5 µm sections with an intact tissue metal interface, excellent surface qualities, histological and immunohistochemical staining properties, and suitability for TEM examination. The technique is applicable to experimental and clinical specimens.

Keywords: stents; resin; histology; immunohistochemistry; transmission electron microscopy     

Surface roughness of acrylic resins submitted to mechanical and chemical polishing

Surface roughness is extremely important as it influences micro-organism accumulation and consequently oral health. The aim of the present study was to evaluate the influence of mechanical polishing (MP) and chemical polishing (CP) on surface roughness of four heat-cured denture base acrylic resins. Twenty sample discs were prepared for each of the following acrylic resins: Classico (CL), QC 20 (QC), Acron MC (AC) and Onda Cryl (ON). The first two are boiling cured resins and the latter two are microwave cured. After curing and deflasking, samples were ground and subdivided into two groups: MP, which received pumice slurry, chalk powder, soft brush and felt cone, at a bench vice; and CP, which received fluid specifically for chemical polisher. Surface roughness was measured using a Surf Corder SE 1700 rugosimeter. Data collected were statistically analysed by analysis of variance followed by Tukey's test. Surface roughness means in mum were: CL-MP: 0.0350; CL-CP: 0.2298; QC-MP: 0.0307; QC-CP: 0.1792; AC-MP: 0.0312; AC-CP: 0.2700; ON-MP: 0.0321; ON-CP: 0.2949. It can be concluded that MP produced significantly smoother surfaces than CP and that surface roughness because of MP was not influenced by acrylic resin type, whereas this was not true of CP.     

Effect of fiber position and orientation on fracture load of fiber-reinforced composite

OBJECTIVES: The aim of this study was to determine the effect of fiber position and orientation on the initial and final fracture loads of fiber-reinforced composite (FRC). METHODS: Test specimens made of two indirect particulate composites (BelleGlass HP, Kerr, Orange, CA) or (Targis, Ivoclar Vivadent, Amherst, NY) were reinforced with ultra high molecular weight polyethylene (UHMWPE) fiber ribbon (Connect, Kerr, Orange, CA), woven E-glass fibers (Vectris Frame, Ivoclar Vivadent, Amherst, NY) or unidirectional R-glass fibers (Vectris Pontic, Ivoclar Vivadent, Amherst, NY). Fibers were placed with different positions, orientations or geometry into the rhombic test specimens (2 x 2 x 25 mm3). Control specimens did not contain fiber reinforcement. The test specimens (n=6) were stored in distilled water for 1 week at 37 degrees C before testing in a three-point loading test to determine the initial and final fracture load values. RESULTS: Initial failure loads varied from 22.6 to 172.1 N. The lowest value resulted from one UHMWPE reinforcement fiber located in diagonal orientation and the highest from two unidirectional glass fiber reinforcements, one located on the tension side and the second on the compression side. SIGNIFICANCE: Position and fiber orientation influenced the load to initial and final failure, and specimen deflection. Tension side reinforcement was most effective in increasing the load to initial and final fracture.     

玻璃离子夹层对光固化复合树脂修复楔形缺损疗效的影响

目的 :探讨玻璃离子夹层在光固化复合树脂修复楔形缺损中的效果。方法 :选择个体条件基本相同的楔形缺损患牙 ,以光固化复合树脂分别采用玻璃离子夹层和直接充填 2种方法修复 ,共 2 2 5例 6 6 3个牙。结果 :所有牙齿治疗后 8～ 2 4个月随访复查 ,两组有效率分别为 90 .4 %和 70 .6 % ,有显著性差异(P <0 .0 1)。结论 :用玻璃离子夹层技术修复楔形缺损比直接用光固化复合树脂修复疗效更理想。     

Longevity of a resin-modified glass ionomer cement and a polyacid-modified resin composite restoring non-carious cervical lesions in a general dental practice

BACKGROUND: Long-term prospective survival studies of resin-modified glass ionomer cements (RMGICs) and polyacid-modified resin composites (compomers) placed in non-carious cervical lesions (NCCLs) are lacking from general dental practice. Short-term studies have shown an unsatisfactory clinical performance for several materials. METHODS: One practitioner placed 87 compomer (Compoglass, Vivadent-Ivoclar) and 73 encapsulated RMGIC (Fuji II LC, GC Int.) restorations in NCCLs for 61 adults. Compoglass was placed using SCA primer, and Fuji II LC using GC Dentin Conditioner. No cavity preparation was undertaken. The Kaplan-Meier method was used for estimating the cumulative survivals for those restorations that were replaced, with the probability level set at alpha = 0.05 for statistical significance. RESULTS: Restorations were judged unsatisfactory (by the practitioner and the subjects) because of surface and marginal loss of material (68.8 per cent), dislodgement (18.8 per cent) and discoloration (12.4 per cent), these modes being similar for both materials (P = 0.35). Unsatisfactory restorations were replaced in 121 (75.6 per cent) instances. After periods of up to five years, cumulative survival estimates were 14.9 (5.8 Standard Error) per cent for Compoglass and zero per cent for Fuji II LC (P = 0.74). Median survivals were 30 months for Compoglass and 42 months for Fuji II LC. CONCLUSION: Both materials had high long-term unsatisfactory performances when placed in non-prepared NCCLs in a general dental practice.     

Microwave Pressure Chamber Processing of a Denture Repair Polymer

Most denture base repairs are made using a chemically activated acrylic resin polymer for reasons of cost and expediency. Heat-activated polymers are not typically used because they require a custom split cast gypsum mold, longer polymerization time, and higher laboratory fees. Repairs made using a chemically activated polymer compared with a heat-activated polymer generally have reduced transverse strength, poorer color stability, increased water sorption, and weak bond strength to existing acrylic resin. A method of utilizing a microwave polymer in a commercially available microwave flask is described. This technique allows denture base repairs to be made with a heat-activated polymer in a manner similar to that of chemically activated repairs.     

Effect of tooth-related factors on the shear bond strengths obtained with CO2 laser conditioning of enamel

Carbon dioxide (CO₂) lasers are capable of producing surface irregularities in human enamel which resemble those resulting from etching of enamel with orthophosphoric acid. This report presents the results of a laboratory study which examined the effect of selected tooth-related variables on shear bond strength between a current generation bonding agent (Scotchbond MultiPurpose) and acid-etched or laser-conditioned human enamel. There were no significant differences in shear bond strength between human maxillary central incisor teeth, first premolars, and third molars in either the acid etch or laser-conditioned groups. Polishing of enamel to give a flat surface increased the shear bond strength obtained with acid etching, but did not alter significantly bond strengths achieved with laser conditioning. There was a tendency for a higher bond strength with acid etching, but not with laser conditioning, in porcine molar enamel compared with human molar and bovine incisor enamel. In terms of the mode of operation of the laser, the repetitively pulsed mode resulted in a two-fold improvement in shear bond strength compared with the single pulse mode. These results indicate that shear bond strengths in the order of 10 MPa can be obtained reliably on human teeth using laser conditioning with pulsed modes in the absence of any other preparation of the natural enamel surface.