Hard Resin Research Articles

Improved Wear Rate Resistance, Compression Strength and Hardness of Polymethylmethacrylate Resin with Orange Peel Powder for Artificial Denture Base

The material utilized for manufacturing artificial dentures should have high-grade mechanical properties in order to resist heavy forces inside the mouth. This study includes investigation of some of the mechanical properties (wear rate resistance, compression strength, and hardness) of the specimens prepared by (hand lay-up) method. The wear behavior experiments were performed on (a pin-on-disk tester) under various factors 5%, 8%, 11%, 14%, 17% weight fraction of orange peel, (10, 15, 20 N) load applied and (5, 10, 15 minutes) sliding time, and analysis these experimentally by using the Taguchi’s experimental design (L9) (MINITAB 16). Tests explicated that the specimens (polymethylmethacrylate - 17% orange peel) composites have the best wear rate resistance, compression strength and hardness shore D (0.040×10-5 cm3/N.mm, 142 MPa, 86 shore D) respectively than other specimens (polymethylmethacrylate - 5%, 8%, 11%, 14% wt. orange peel) and these specimens better than the specimens standard polymethylmethacrylate, which could be attributed to the homogeneous dispersion of orange peel particles in the polymethylmethacrylate resin matrix. The results (signal to noise ratio) showed the factors (17% weight fraction) orange peels, (20 N) load applied, and (5 min) sliding time gives the best wear rate resistance. The results of the analysis of variance showed the sliding time (C) is the essential factor effect on the wear rate resistance followed by (A) weight fraction of orange peels and (B) load applied were less affected on wear behavior rate.

Evaluating antibacterial and surface mechanical properties of chitosan modified dental resin composites.

The antibacterial properties are beneficial and desired for dental restorative composite materials. The incorporation of various antimicrobial agents into resin composites may compromise their physical and mechanical properties hence limiting their applications. The aim of the current study is to evaluate the antibacterial activity and the hardness of microhybrid and flowable resin based composites (RBCs) modified using novel antimicrobial agent chitosan (CS). The antibacterial activity of microhybrid and flowable RBCs modified with 0, 0.25, 0.5 and 1% w/w chitosan (CS) against Actinomyces viscous bacteria was explored using agar diffusion test and direct contact methods. The hardness of control and experimental RBCs was determined by Vickers hardness (VH) tester. The results revealed that control and experimental flowable and microhybrid RBCs did not demonstrate growth inhibition zone in the lawn growth of Actinomyces viscous. The direct contact test revealed that colony forming unit (CFU) count of Actinomyces viscous was comparable among the experimental and control materials. The flowable RBCs containing 1% CS had significantly higher VH compared to control and other experimental flowable RBC groups. The microhybrid RBCs consisting of 0.50% CS exhibited significantly higher VH compared to experimental microhybrid RBC group containing 1% CS.

Influence of silanized silica and silanized feldspar addition on the mechanical behavior of polymethyl methacrylate resin denture teeth

Statement of problemArtificial denture teeth made of polymethyl methacrylate (PMMA) resin have good adhesion to the denture base but are relatively soft and have limited wear resistance during function. PurposeThe purpose of this in vitro study was to evaluate the influence of the addition of 2 inorganic nanofillers on the flexural strength, maximal displacement, elastic modulus, Isolde impact resistance, and Brinell hardness of acrylic resin denture teeth. Material and methodsHeat polymerizing polymethyl methacrylate resin was mixed with silanized silica or silanized feldspar in concentrations of 5 wt%, 10 wt%, and 15 wt%. The first test was conducted after 24 hours of storage in laboratory conditions, and the second assessment was conducted after 3 months of storage in distilled water at 37 °C. The Brinell hardness was evaluated, and the elastic modulus and maximal displacement at fracture were calculated. The flexural strength and Isolde impact resistance were measured with a 3-point flexural test. Acrylic resin specimens without filler addition were used as a control group. Statistical analysis included 2-way ANOVA for independent variables (α=.05) and the Student t test for time-dependent changes (α=.05). These were performed with Statistica 12 software. ResultsThe acrylic resin specimens modified with the addition of silanized feldspar had significantly higher Brinell hardness, elastic modulus, maximal displacement, and flexural strength and also had no adverse effect on Isolde impact resistance compared with the conventional acrylic resin. Silica filler increased the Brinell hardness and elastic modulus of acrylic resins but significantly reduced the flexural strength and Isolde impact resistance.

Orthodontic resin containing bioactive glass: Preparation, physicochemical characterization, antimicrobial activity, bioactivity and bonding to enamel

ObjectivesTo synthesize experimental orthodontic resins used for bracket bonding containing different concentrations of niobophosphate (NbG) and 45S5 glasses. MethodsExperimental resins (Bis-GMA + UDMA + DMAEMA) were developed with two bioactive glasses (NbG and 45S5) in concentrations of 5, 10 and 20 (wt%). An experimental resin without glass and a commercial resin (Transbond XT) were used. Control of pH and ions release (calcium and phosphate) at different pH values (4 and 7) were evaluated in the time intervals of 24 h, 7 d, 14 d and 28 d. Microhardness, bioactivity (SEM, FTIR/ATR) and antibacterial activity of the resins were analyzed. Metal brackets were bonded to premolars (n = 10) with the resins to evaluate shear bond strength (SBS). ResultsThe experimental resins containing 45S5 were capable of raising the pH of the solution and showed high values of calcium and phosphate ions release. Resins containing NbG had a neutralizing potential. The NbG and Transbond resins released only phosphate ions. Transbond XT showed high microhardness values when compared with the experimental 45S5 resins (p < 0.05). Analysis by SEM showed precipitates and FTIR/ATR confirmed the presence of a calcium phosphate-based compound in the resins containing 45S5. There was no difference in SBS between the tested materials (p > 0,05). The resins with presence of bioactive particles showed antibacterial activity. ConclusionWithout compromising the shear bond strength, bioactive glasses showed the capacity to elevate pH, reduce the hardness of experimental resins when compared with Transbond XT and no filler experimental resin.

Histological, Histomorphometrical, and Biomechanical Studies of Bone-Implanted Medical Devices: Hard Resin Embedding

The growing incidence of degenerative musculoskeletal disorders as well as lifestyle changes has led to an increase in the surgical procedures involving implanted medical devices in orthopedics. When studying implant/tissue interface in hard materials (i.e., metals or dense plastics) and/or in large bone segments, the hard plastic embedding of the intact undecalcified tissue envelope with the implant in situ is needed. The aim of this work is to describe the advances and the possibilities of high-temperature methyl methacrylate (MMA) embedding for the histological, histomorphometrical, and biomechanical assessment of bone-implanted medical devices. Unlike routine techniques, undecalcified bone processing histology, using high-temperature MMA, requires a complex and precise sample processing methodology and the availability of sophisticated equipment and software for both sample preparation and analyses. MMA embedding permits the evaluation of biological responses to the presence of implanted medical devices without implant removal, allowing simultaneous qualitative and quantitative histological evaluation, both static and dynamic histomorphometry, and biomechanical analyses not possible with tissue decalcification. MMA embedding, despite being a demanding procedure, is still preferred to other kinds of resin-based embedding because of its peculiar characteristics, which allow the study of samples of big dimensions also implanted with hard materials without reducing the sample or removing the material. Dynamic measurements are allowed together with biomechanical investigations at the bone-biomaterial interface, obtaining a comprehensive and precise evaluation of the safety and effectiveness of medical devices for orthopedic regenerative, reconstructive, and reparative surgery.

Nitrogen-doped hollow carbon spheres with tunable shell thickness for high-performance supercapacitors.

Nitrogen-doped hollow carbon spheres (NHCSs) are well prepared by using Cu2O microspheres as a hard template and 3-aminophenol formaldehyde resin polymer as carbon and nitrogen precursors. The thickness of the carbon shell can be easily controlled in the range of 15–84 nm by simply adjusting the weight ratios of the precursors to Cu2O microspheres, and the Cu2O templates can also be further reused. Physicochemical characterization demonstrates that the obtained NHCSs possess a well-developed hollow spherical structure, thin carbon shell and high nitrogen doping content. Due to these characteristics, when further utilized as electrodes for supercapacitors, the NHCSs with the carbon shell thickness of 15 nm show a high capacitance of 263.6 F g−1 at 0.5 A g−1, an outstanding rate performance of 122 F g−1 at 20 A g−1 and an excellent long-term cycling stability with only 9.8% loss after 1000 cycles at 5 A g−1 in 6 M KOH aqueous electrolyte. This finding may push forward the development of carbon materials, exhibiting huge potential for electrochemical energy storage applications.

Characteristics by filler type of dental hard resin for indirect restorations

Characteristics by filler type of dental hard resin for indirect restorations

The influence of the post-processing method on knoop hardness of photosensitive resins for 3D SLA printer used in Dentistry

Objectives: The aim of this study is to compare the mechanical characteristics of resins for 3D printers with the acrylic resins that have been used in Dentistry, according to the post-processing method. Materials and Methods: Using an SLA 3D printer (Form 2 – Formlabs, Massachusetts, USA), samples (discs) were produced with the printer’s resins, Dental SG®, Dental LT®, Clear®, and Grey®. Samples made of thermopolimerized and auto polymerized acrylic resins were produced as well (Gold Standart parameters). The Knoop Hardness (KH) tests were performed using microdurometer HMV-2 (Shimadzu, Kyoto, Japan). Results: The results showed the Dental SG resin presented the highest KH, compared with thermopolimerized acrylic resin, the Clear and Dental LT resins KH were compared with auto polymerized acrylic resin, and the non-post cured Grey resin (not for intraoral use), as well as the Dental LT resin, showed the lowest KH. Conclusions: Considering the hardness, the printer’s resins are comparable with the acrylic resins established, when the post-processing method is thoroughly followed. The absence of material’s post-processing reduce significantly the material’s hardness. Clinical relevance: Regarding the use of 3D printing in Dentistry, the development of materials adequate for the equipment, biocompatible for intraoral uses, and compatible mechanical proprieties are essential.

Hydrocephalus shunt therapy: current titanium shunt valve implants obstructed by internal tissue proliferations identified as extracellular matrix membranes.

Shunt valves, required for treatment of hydrocephalus, demand for high performance rates and lifelong excellent function. To overcome problems with traditional silicone materials, adjustable and gravity-adapted titanium valves were developed. Even modern shunt valve systems are still subject to occlusion. The aim of the present study was to investigate dysfunctional silicone and titanium valves for presence of cellular and proteinous materials inside the housings by means of histopathology. A total of 19 explanted shunt valves from children between 2 and 182 months of age were investigated following dysfunction. After fixation in formalin and embedding in hard resin, slices were ground to a thickness of 5-30 μ. Besides standard histology, immunohistochemistry was performed using antibodies with markers for microglia, astrocytes, platelets, monocytes, and the proteins laminin, fibronectin, and collagen IV. Traces, layers, and plaques could be demonstrated in every investigated silicone or titanium valve with an implantation time of more than 6 days. Most of the tissue was found adjacent to silicone and titanium surfaces of the inner housing, the adjustment rotor, and ball-in-cone core. Markers for micro and astroglia stained positive in 40-60% of the specimen, mostly demonstrating a proteinous layer positive for laminin (80%), fibronectin (30%), and collagen IV (30%). Tissue reactions with formation of cellular and proteinous matrix components are common in obstructed silicone and titanium shunt valves. The tissue mimics astrocytic repair mechanisms genuine for basilar membrane matrix. The knowledge of these typical arachnoid patterns of colonization is a prerequisite for developing future shunt devices.

Effect of 10% carbamide peroxide bleaching gels on surface hardness of nano filled composite resin

Introduction: Home bleaching is the whitening treatment of vital teeth applied by patients themselves at home under dentist supervision. In clinical condition, several patients who need bleaching treatment already had nano filled composite resin restoration on their teeth. The purpose of this study was to investigate the contact time difference of 10% carbamide peroxide bleaching gels application for home bleaching on the surface hardness of nano filled composite resin activated by Light Emitting Diode (LED). Methods: Total sample in this study was 30 samples, divided into 3 groups. The samples used were nano filled composite resin cylindrical shape with a diameter of 6 mm and a thickness of 2 mm. Group I as the control group was immersed in distilled water, group II was treated with immersion in 10% carbamide peroxide for 4 hours per day, and group III was immersed in 10% carbamide peroxide for 6 hours per day. The duration of treatment was 14 days for all groups. Data were analysed using Kruskal-Wallis with Mann-Whitney test and the p-value = 0.05. Results: The result of one-way Kruskal-Wallis with Mann-Whitney test showed that there were significant difference between the control group and the groups applied with 10% carbamide peroxide for 4 hours and 6 hours per day with the p-value 0.00 (p &lt; 0.05). Conclusion: Application of 10% carbamide peroxide decreasing the surface hardness of nano filled composite resins activated by LED.Keywords: Nano filled composite resin, carbamide peroxide, composite resin hardness, Light Emitting diode (LED).

3D Helical Micromixer Fabricated by Micro Lost‐Wax Casting

AbstractMicromixers produced by micro fabrication techniques have attracted attention for micro total analysis systems and lab‐on‐a‐chip applications in point‐of‐care testing. However, the fabrication and setup of micromixers have become more complex and more difficult. Considering the practical use of micromixers in medical and industrial applications, their designs can be simplified while maintaining high mixing efficiency. Rapid prototyping, represented by 3D printing having micro‐scale resolutions, is one promising technology to replace conventional fabrication methods such as soft lithography. Here, a 3D helical micromixer fabricated by micro‐scale lost‐wax casting is reported. The molds for lost‐wax casting are fabricated by fine 3D printing of a hard wax resin which can be removed from a polydimethylsiloxane block just by heating and washing with water, and a fine and smooth structure is realized. The optimized helical micromixer fabricated by lost‐wax casting promotes mixing efficiency compared with other micromixers. In addition, a monolithic microchannel having the helical 3D bridge structure is presented in this study. The demonstration is an important advancement toward the industrial applications of micromixers fabricated by micro‐scale 3D printing. The ability to fabricate complex structures can simply lead to the creation of more sophisticated mixers in the future.

The effects of intrinsic and extrinsic acids on nanofilled and bulk fill resin composites: Roughness, surface hardness, and scanning electron microscopy analysis.

The objective of this study was to examine the effects of extrinsic or intrinsic acids on nanofilled and bulk fill resin materials in vitro. A total of 90 disks were prepared using dental restorative material (Filtek Z350XT, GrandioSO, Filtek Bulk Fill, X-tra fil). Thirty disks of each material were sub-divided into three groups (n = 10) that were immersed for 7 days in deionized water (DW), 5% citric acid (CA-pH 2.1), or 0.1% hydrochloric acid (HCl-pH = 1.2). Surface hardness and roughness (stylus profilometer by Ra parameter) analysis were performed before and after immersion. Morphological changes were evaluated by scanning electron microscopy. The data were analyzed by two-way ANOVA and Tukey's test (α = 0.05). All tested materials did not show significant differences in the effects of the DW, CA, or HCl solutions on surface roughness (p = .368). Likewise, the hardness loss was not affected by the solutions tested (p = .646), but there was a difference in the resin type (p = .002). Filtek Bulk Fill resin hardness was less affected, while Filtek Z350XT and GrandioSO presented the most hardness loss after 7 days of solution immersion. In terms of this experimental study, the results demonstrate the effectiveness of the mechanical properties (roughness and hardness surface) of nanofilled and bulk fill resin materials to resist erosion from extrinsic and intrinsic acids, therefore being potential candidates for dental applications.

Surface Treatment Of Nanozirconia Fillers To Strengthen Dental Bisphenol A-Glycidyl Methacrylate-Based Resin Composites.

PurposeTo investigate the effects of nanozirconia fillers conditioned with 10-methacryloyloxydecyl dihydrogen phosphate (MDP) with or without zirconium hydroxide precoating on bending strength, Vickers hardness, and translucence of dental resin composites.MethodsWe obtained nanozirconia fillers coated with different concentrations of Zr(OH)4 using wet-chemical synthesis. We analyzed coating quality by observing electron-diffraction patterns using transmission electron microscopy. We conditioned zirconia fillers, with or without prior Zr(OH)4-coating, using MDP-containing primers and evaluated the formation of chemical bonds using nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). We then performed three-point bending-strength tests, Weibull analysis, Vickers hardness, and translucence-parameter analysis with or without addition of different concentrations of zirconia using untreated zirconia fillers as controls.ResultsWe achieved desirable Zr(OH)4 coating using 5 mmol/L zirconium chloride. NMR and XPS analysis detected stronger Zr–O–P peaks on MDP-conditioned zirconia fillers with prior Zr(OH)4-coating compared with MDP-conditioned fillers alone, suggesting that MDP bonding with zirconia was enhanced by zirconium hydroxide. Our three-point bending-strength tests revealed that increasing levels of untreated zirconia fillers decreased the three-point bending strength of the resin composites, while MDP-conditioned zirconia fillers with or without prior Zr(OH)4 coating improved three-point bending strengths. Adding 5 wt% and 7.5 wt% MDP-conditioned zirconia fillers with prior Zr(OH)4 coating achieved the highest three-point bending strength. Furthermore, addition of zirconia fillers decreased the translucence of silica-based resin composites.ConclusionMDP conditioning with prior Zr(OH)4 coating is recommended for treating nanozirconia fillers of resin composites.

Atlas of Normal Microanatomy, Procedural and Processing Artifacts, Common Background Findings, and Neurotoxic Lesions in the Peripheral Nervous System of Laboratory Animals.

The ability to differentiate among normal structures, procedural and processing artifacts, spontaneous background changes, and test article-related effects in the peripheral nervous system (PNS) is essential for interpreting microscopic features of ganglia and nerves evaluated in animal species commonly used in toxicity studies evaluating regulated products and chemicals. This atlas provides images of findings that may be encountered in ganglia and nerves of animal species commonly used in product discovery and development. Most atlas images are of tissues from control animals that were processed using routine methods (ie, immersion fixation in neutral-buffered 10% formalin, embedding in paraffin, sectioning at 5 µm, and staining with hematoxylin and eosin) since these preparations are traditionally applied to study materials produced during most animal toxicity studies. A few images are of tissues processed using special procedures (ie, immersion or perfusion fixation using methanol-free 4% formaldehyde, postfixation in glutaraldehyde and osmium, embedding in hard plastic resin, sectioning at 1 µm, and staining with toluidine blue), since these preparations promote better stabilization of lipids and thus optimal resolution of myelin sheaths. Together, this compilation provides a useful resource for discriminating among normal structures, procedure- and processing-related artifacts, incidental background changes, and treatment-induced findings that may be seen in PNS tissues of laboratory animals.

Production of gasoline-like-fuel and diesel-like-fuel from hard-resin of Yang (Dipterocarpus alatus) using a fast pyrolysis process

Production of gasoline-like-fuel and diesel-like-fuel from Yang (Dipterocarpus alatus) hard resin (HY) was studied for use as a fuel for engines using a fast pyrolysis process. HY was pyrolyzed in a semi-continuous reactor at pyrolysis temperatures of 450 °C, 500 °C, 550 °C and 600 °C. For each pyrolysis temperature, height of the reflux condenser (RC) was changed between 0 m (non-reflux condenser, NRC) and 1 m. Bio-oil products from each pyrolysis condition were distilled into light fuel and heavy fuel to find the optimal fuel production conditions. Fuel obtained from the optimal conditions as pyrolysis temperature 500 °C and a 1 m RC was measured for density, viscosity, heat value, distillation and corrosion compared to commercial fuels. Under these conditions, HY 100 wt% produced 55.22 wt% of fuel, separated into 17.81 wt% light fuel and 37.41 wt% heavy fuel with total specific energy consumption 6.78 kWh/kg. Using RC increased the amount of distilled products. Characteristics of heavy and light fuels were similar to standard fuels as DLF (diesel-like-fuel) and GLF (gasoline-like-fuel) respectively.

Effects of different discoloration challenges and whitening treatments on dental hard tissues and composite resin restorations

ObjectivesTo compare the relative effects of cigarette smoke (CS), electronic cigarette (EC), red wine, coffee, and soy sauce on the color of enamel, dentin, and composite resin restorations, as well as the effects of whitening treatments. MethodsSeventy premolars with composite restorations were exposed to CS, EC aerosol (a novel EC device with MESH™ technology [P4M3 version 1.0, Philip Morris International]), red wine, coffee, and soy sauce for 56 min/day for 15 days. Two whitening sessions with 6% and 35% hydrogen peroxide (H2O2) were performed on the exposed samples. Teeth exposed to CS and EC aerosol were also brushed with whitening toothpaste for 3 weeks. Color match of resin restorations was assessed, and color changes were compared after exposure and after whitening treatments. ResultsDiscolorations in enamel, dentin, and composite resin were observed in the order of red wine > CS > soy sauce > coffee > EC. Color mismatch between enamel and resin restorations occurred only in red wine and CS groups. Brushing with whitening toothpaste removed discoloration caused by EC aerosol; H2O2 treatments were necessary to eliminate discolorations caused by coffee and soy sauce. Discolorations of dentin and resin restorations could not be completely removed by whitening treatments, and color mismatch remained in teeth exposed to red wine and CS. ConclusionRed wine and CS cause significant tooth discoloration and color mismatch in enamel and resin restorations that are not reversible by whitening treatments. Tooth discoloration associated with EC aerosol was minimal and could be removed by brushing with whitening toothpaste. Clinical significanceRed wine drinkers and cigarette smokers have increased risks for tooth discoloration and color mismatch between enamel and composite resin restorations. Whitening treatments may not be effective in correcting the color mismatch. Tooth discoloration associated with EC aerosol is minimal.

Beneficial Effects of Ethyl-Cyanoacrylate Coating Against Candida Albicans Biofilm Formation.

The aim of this study was to verify whether modifications made in a hard chairside reline resin by an ethyl-cyanoacrylate adhesive, ECA (Super Bonder®, Loctite, Itapevi, SP, Brazil) would be able to inhibit or reduce Candida albicans biofilm formation on its surface, comparing to a commercial surface sealant (BisCover®, Bisco, Schaumburg, USA). Reline resin specimens were fabricated and randomly divided into 6 groups (n=8): CG (control group), no surface treatment; ECA1, ECA coating on the surface before sterilization; ECA2, ECA coating after sterilization; ECA3, ECA incorporated in the resin bulk; DPE1, BisCover® coating before sterilization; DPE2, BisCover® coating after sterilization. Specimens were inoculated with C. albicans SC5314 (1x107 cells/mL) and incubated for 24 h. Then, the biofilm were stained with LIVE/DEAD® BaclightTM L7007 Kit and analyzed by Confocal Laser Scanning Microscopy. The images were evaluated by bioImageL® v.2.0 software and total biovolume (µm3), viable cells (%), and covered area (%) were calculated. Data were statistically analyzed by Kruskal-Wallis and Dunn tests (p<0.05). Results showed that ECA-coated groups presented better results, reducing C. albicans biofilm formation. Acquired images revealed that these groups (ECA1 and ECA2) presented a reduced number of cells, mostly in yeast form (less pathogenic), while the other groups presented higher number of cells, mostly in hyphae form (more pathogenic). Based on these findings, a beneficial effect of Super Bonder® coating reline resins surface could be demonstrated, suggesting a promising way to prevent fungal biofilm formation on dentures.

Adhesion potential of relining materials to polyamide and PMMA-based denture base materials: effect of surface conditioning methods

This study evaluated the bond strength of relining materials to different denture base materials polyamide and polymethylmethacrylate denture base materials after various surface conditioning methods. Denture base resin specimens (N = 128; n = 8 per group) (10 × 10 × 2.5 mm3) were fabricated out of injection-moulded thermoplastic polyamide resin (POL) (Deflex) and heat-polymerized polymethylmethacrylate (PMMA, Dura Dent) (HC). The specimens were randomly divided into 4 main groups according to different surface conditioning methods: (a) No conditioning, control (C), (b) grinding with green stone (G), (c) application of primer (V), (d) silica coating with Al2O3 particles coated with SiO2 (Rocatec) (R). Half of the specimens in each group received auto-polymerized hard relining resin (GC, GC Reline Hard) and the other half PMMA based relining resin (SC, Dura Dent). After thermocycling (×5000), the bonded specimens were tested under tensile forces (0.5 mm/min). Data (MPa) were analyzed using Mann–Whitney U and Kruskal–Wallis tests (alpha = 0.05). Bond strength of relining resins were significantly higher to PMMA than to POL, regardless of the conditioning method (p < 0.05). While R positively affected the bond strength results (p < 0.05) (4.99 ± 1.65–3.27 ± 1.31), application V or G did not show significant effect to POL-relining resin adhesion. After R conditioning, bond strength values were significantly higher in HC-GC group (7.48 ± 2.32) than POL-GC group (3.27 ± 1.31) (p < 0.05). Adhesion of auto-polymerized relining materials to thermoplastic polyamide or polymethylmethacrylate denture resins could be improved after surface conditioning with silica-coating.

Histology Strategies for Medical Implants and Interventional Device Studies

Histology of medical devices poses a variety of unique challenges. Comprehensive histologic assessment of medical devices often requires spatial context and high-quality retention of the device-tissue interface. However, the composition of many medical devices is often not amenable to traditional paraffin embedding and thus alternative specialized methodologies such as hard resin embedding must be used. Hard resin embedding requires specialized laboratory technical expertise and equipment, and the fixation techniques and resin composition used markedly impact the feasibility of immunohistochemistry. For the continuity of spatial context during histologic evaluation, additional imaging methods such as macrophotography, radiography, micro-Computerized Tomography (microCT), or magnetic resonance imaging (MRI) can be used to guide sectioning and to complement histologic findings. Although standardized approaches are scarce for medical devices, important considerations specific to medical device histology are discussed, including general specimen preparation, special considerations for devices by organ system, and the challenges of immunohistochemistry. Histologic preparation of medical devices must be thoughtful, thorough, and tailored to achieve optimal histologic outcomes for complex, valuable, and often limited implant specimens.

Comparison of the Water Sorption and Solubility of Four Reline Acrylic Resins after Immersion in Food-Simulating Agents.

Objectives:Water sorption and water solubility adversely affect the mechanical properties and biocompatibility of the denture material. This study aimed to evaluate the water sorption and solubility of three direct hard reline acrylic resins and a heat-curing one after immersion in food-simulating agents.Materials and Methods:This study was performed on four groups of samples (n = 10 per group). The samples were made of three direct hard reline acrylic resins (TDV Cold Liner Rebase, Tokuyama Rebase II Fast, GC Reline Hard) and a heat-curing one (Meliodent). Each group was divided into four subgroups (n = 10) to undergo 7-day immersion in distilled water, 75% ethanol/water, 0.02 N citric acid, and heptane. Water sorption and solubility were calculated according to Oysaed and Ruyter formula. The statistical analyses were done by using SPSS software (version 22). Kruskal–Wallis H Test and Dunn's test were used to detect any significant difference among the groups (P < 0.05).Results:The median range of water solubility and water sorption values were −0.87–4.92 and 3.75–27.25 μg/mm3, respectively. The median solubility and sorption values of different resins differed significantly in the same solution (P < 0.05). Besides, immersion in different solutions caused significant differences in the median solubility and sorption values of each reline material (P < 0.05), except for Meliodent whose solubility was not significantly affected by different solutions (P = 0.16).Conclusions:Water sorption and solubility values of the tested hard reline resins were within the range of International Standards Organization 1567:1999. Given the low sorption and solubility values, these hard reline materials can be safely used in clinical situations.