Hard Resin Research Articles

Effect of Irradiation Distance of LED on Bulk-Fill Composite Resin Hardness

Introduction: Bulk-fill composite is a restorative material with the advantage of 4 mm thickness application into the cavity and good modulus of elasticity similar to natural teeth. One of the important aspect in composite restoration is polymerization which is a formation of polymer from monomers. One way to achieve a high degree of polymerization is to use Light Emitting Diode (LED) irradiation, which will increase the hardness of the composite resin. Objective: The purpose of this study was to determine the effect of distance between the LED tip with bulk-fill composite surface on the hardness of composite. Methods: Fifteen samples were divided into three groups with irradiation distance of 0 mm, 5 mm, and 9 mm respectively. Samples were made in a cylindrical shape with 6 mm of diameter and 4 mm of height then irradiated with LED for 10 seconds. The samples then immersed in distilled water at 37o for 24 hours. Hardness test was carried out on three different points at the top and bottom each side using Vickers hardness test. Data was analyzed with Shapiro-Wilk and One Way ANOVA. Results: The highest hardness value was obtained in the group with an irradiation distance of 0 mm, while the lowest was in the group with irradiation distance of 9cm, both on the top and bottom surfaces. Increasing the distance between the tip of light curing unit and the composite surface resulted in a significant reduction in the hardness of the composite. Conclusion: There were significant differences in the hardness value of bulk-fill composite in all distance group.

3D-Printable Denture Base Resin Containing SiO2 Nanoparticles: An In Vitro Analysis of Mechanical and Surface Properties.

To evaluate the flexural strength (FS), impact strength (IS), surface roughness (Ra), and hardness of 3D-printed resin incorporating silicon dioxide nanoparticles (SNPs). A total of 320 acrylic specimens were fabricated with different dimensions according to test specifications and divided into a control group of heat denture base resin, and 3 test groups (80/test (n = 10) of unmodified, 0.25 wt%, and 0.5 wt% SNPs modified 3D-printed resin. 10,000 thermal cycles were performed to half of the fabricated specimens. FS, IS (Charpy impact), Ra, and hardness were evaluated and the collected data was analyzed with ANOVA followed by Tukey's post hoc test (α = 0.05). Incorporating SNPs into 3D-printed resin significantly increased the FS, IS (at 0.5%) and hardness compared to unmodified 3D-printed resin (p < 0.001). However, the FS of pure 3D-printed and 3D/SNP-0.50% resin and IS of all 3D-printed resin groups were significantly lower than the control group (p < 0.0001). Hardness of 3D/SNP-0.25% and 3D/SNP-0.50% was significantly higher than control and unmodified 3D-printed resin (p < 0.0001), with insignificant differences between them. The Ra of all 3D-printed resin groups were significantly higher than control group (p < 0.001), while insignificant difference was found between 3D-printed groups. Thermal cycling significantly reduced FS and hardness for all tested groups, while for IS the reduction was significant only in the control and 3D/SNP-0.50% groups. Thermal cycling significantly increased Ra of the control group and unmodified 3D-printed resin (p < 0.001). The addition of SNPs to 3D-printed denture base resin improved its mechanical properties while Ra was not significantly altered. Thermal cycling adversely affected tested properties, except IS of unmodified 3D-printed resin and 3D/SNP-0.25%, and Ra of modified 3D-printed resin.

Influence and Effect of Pyrolysis with Additives in Tantalum Capacitors

In recent years, the demand for tantalum capacitors has been increasing due to the miniaturization of electronic devices. Tantalum capacitors, which use the rare metal tantalum as the capacitor element, are used in electronic devices such as cell phones because they are smaller and have a higher capacity than conventional capacitors. In Japan, there are reports that minerals containing rare elements are being extracted from discarded electronic and electrical equipment to produce medals for the 2020 Tokyo Olympics. In Japan, many used electrical products containing rare elements are discarded, and these metals are called urban mines. The tantalum contained in tantalum capacitors accounts for 40% of the total mass of the sintered material and is expected to be recycled from discarded products. However, tantalum capacitors are covered with a hard mold resin of acrylonitrile-butadiene-styrene (ABS) resin, which is chemically and physically stable. However, due to its nature, ABS resin is difficult to destroy and has not been recycled. In this study, hydrotalcite (HT) (Mg6Al2(OH)16CO3・MH2O) was used to extract tantalum from the sintered tantalum capacitor by pyrolysis. HT was added to the tantalum capacitor and placed in a metal reactor and subjected to pyrolysis at 550℃ in nitrogen to determine if the sintered tantalum was susceptible to fracture. It is presumed that the bromine gas generated from the ABS resin of the tantalum capacitor was trapped by the HT and the mold resin of the capacitor became residual carbon.

Effect of repair methods and materials on the flexural strength of 3D-printed denture base resin.

The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling. Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM). Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone. Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.

Research on adding composite resin to hard resin teeth

Research on adding composite resin to hard resin teeth

Effect of Ethylmethacrylate and Isobutylmethacrylate on Surface Hardness and Surface Roughness of Heat-Cure Ocular Acrylic Resins

Background Acrylic resin is a commonly utilized material in clinical practice, including: maxillofacial prosthesis Interim prostheses, repair dentures, reline, orthodontic equipment, and record bases are only a few examples of possible applications. However, these materials have some drawbacks, for example low mechanical properties. To improve the performance of the acrylic resins, various materials have been incorporated. Purpose: The purpose of this research is to assess the effects of adding different concentrations of copolymers of Ethyl methacrylate (EA) and Isobutyl methacrylate (IBMA) monomers on some of the mechanical properties of acrylic resin such as surface hardness and surface roughness. Approach: 100 samples were made of acrylic resin and were divided into three groups (a control group and two experimental groups). Twenty samples were used for the control group and these samples were divided into ten samples for each group based on the tests performed. While 40 samples per experimental group (IBMA, EMA) were divided into two groups according to the added concentration (1% and 2%). Then, according to the tests performed, each group was divided into two groups with ten samples for each group. Acrylic samples were fabricated with dimensions of 65 mm x 10 mm x 2.5 lengths, width and thickness respectively according to (ADA specification, No.12, 1999). Each specimen was subjected to the surface hardness test and surface roughness test. All data were analyzed using SPSS version 20, One –way ANOVA, LSD and Post Hoc -Tukey test were utilized for detecting the significant differences and multiple comparisons. Results: The control group had the greatest mean value of hardness compared with the experimental group while the EMA 1% group showed the lowest mean value of roughness test compared with the control and other experimental groups. Conclusion: The incorporation of experimental groups (IBMA, EMA) in different concentrations by weight in MMA and PMMA had a decrease slightly of surface hardness of acrylic resins, and the incorporation of EMA 1% by weight in MMA and PMMA had improved surface roughness. In added EMA2%, IBMA 2% enhanced slightly the surface roughness of acrylic resins.

Monitoring of Glycosidically Bound Polyphenols in Hops and Hop Products Using LC-MS/MS Technique

Recent findings have shown that besides bitter acids, several additional hop ingredients contribute to beer bitterness. These belong to the class of polyphenols and are also part of the hard resin fraction of hops. They include the two well-known flavonols, quercetin and kaempferol, widespread in the plant kingdom. On the other hand, the so-called multifidols are more typical to hops as intermediates in the biosynthesis of alpha- and beta-acids. Both of the above mentioned flavonols and the multifidols occur mainly not in their free forms but rather bonded to sugars such as glucose. In our study, the contents of such glycosidically bound polyphenols were determined in a worldwide spectrum of different hop varieties using liquid chromatography in combination with tandem mass spectrometry. In total, more than 500 samples from crops 2020 and 2019, representing 34 different varieties, were analyzed. The detected concentrations (mg/100 g) were dependent on variety, with ranges between of 6–155 for co-multifidol glucoside, 3–60 for ad-multifidol glucoside, 13–87 for quercetin-3-O-glucoside, 5–46 for quercetin-3-O-rutinoside, and 4–35 for kaempferol-3-O-glucoside. Moreover, their fate during large scale hop extraction was investigated. It was confirmed that polyphenol glycosides were not extracted with supercritical carbon dioxide but were extracted with ethanol.

Degradability of bulk-fill resin composites after cyclic immersion in different distilled alcoholic beverages.

To investigate effect of distilled alcoholic beverages on surface hardness, roughness, and erosion of bulk-fill resin composites. Sixty eight specimens of each bulk-fill resin composite (Filtek One Bulk Fill Restorative, SonicFill 2, and Tetric N-Ceram Bulk Fill) were prepared. Baseline data of surface hardness and roughness value were recorded. The specimens were divided into five groups: vodka, whisky, tequila, brandy, and deionized water (served as a control). Specimens were then alternately immersed in 25 ml of a storage agent for 5s and in 25 ml of artificial saliva for 5s over 10cycles. This process was repeated for 14 days. After immersion, specimens were subjected to evaluation of surface hardness, roughness, and erosion on days 7 and 14. The data were statistically analyzed by two-way repeated analysis of variance, Tukey's honestly significant difference, and a t test (p < 0.05). Distilled alcoholic beverages caused significant hardness decrement, roughness and erosion increment (p < 0.05), where the greatest degradation was found in brandy group. Tetric N-Ceram Bulk Fill had the most significant decrement in hardness and increment in roughness and erosion than the other resin composites (p < 0.05). Distilled alcoholic beverages affected hardness, roughness, and erosion of all the bulk-fill resin composites. Regarding the bulk-fill resin composites tested, Filtek One Bulk Fill Restorative was the most appropriate restorative material in patients who consume distilled alcoholic beverages.

Mechanical properties of cured epoxy resin

We study experimentally the influence of mass fraction of L-20 hardener cold cure on mechanical properties of epoxy diane resin ED-20. We measure the hardness, tensile strength, bending strength and impact strength of resin at different values of the hardener mass fraction. It is found that the ratio hardener mass fraction of 1:0.9 leads to the highest values of the hardness, tensile strength, compressive strength and bending strength. The impact viscosity is maximum at the ratio hardener mass fraction of 1:0.8. The optimal ratio of a non-toxic safe hardener to the resin is derived based on obtained mechanical characteristics.

Unique Gelation of Polyethylene Glycol-Modified Lignin in Hot Ethanol and Its Application to the Synthesis of Epoxy Resin with a Large Lignin Content

Glycol lignin is one of the novel lignin derivatives extracted from softwood meal and is expected to be an industrially important organic resource. Here, we show the peculiar aggregation behavior of glycol lignin in ethanol and the production of an ethanol-containing gel. The gel could be simply obtained by stirring glycol lignin powder in hot ethanol for several minutes. Furthermore, the gelled glycol lignin could be easily and homogeneously mixed with a traditional epoxy chemical, bisphenol A diglycidyl ether, in any ratio without any additional solvent and/or heating, resulting in an easy production of epoxy resin using wood-based lignin resources. Since the residual ethanol in the mixture could be easily evaporated before the curing process, thermosetting hard epoxy resin with glycol lignin contents of up to 90 wt % was prepared through the homogeneous mixing with the gel. Quantitative analysis of the equilibrium reaction between ethanol and glycol lignin using a gas adsorption analysis tool was investigated to understand the gelation behavior. It was suggested that the ethanol molecules were stored between polyethylene glycol molecular chains in glycol lignin, which generates a unique chemical character of this novel lignin derivative material.

Occlusal appliance therapy for temporomandibular disorders

Occlusal appliance is a removable device which fits over the occlusal surfaces of the teeth in one arch, devised to provide precise occlusal contact with the opposing teeth. Occlusal appliance is usually made of hard acrylic resin and allows optimum dentition in which condyle may assume in its most orthopedically stable position. Oc-clusal appliance is used to treat various kinds of temporomandibular disorders, including joint and muscle pain, disc derangements, parafunctional habits like bruxism and clenching, and degenerative joint diseases of TMJ.There are various types of occlusal appliances, but stabilization appliance and anterior positioning appliance are most frequently used. Stabilization appliance is fabricated to provide optimum occlusal relationship for the patient. This appliance is indicated for muscle and joint pain disorders and helpful for reducing parafunctional habits like bruxism. Anterior positioning appliance is designed to protrude mandible to a position that is more anterior than the intercuspal position. It is primarily used to treat disc displacement with reduction, intermittent lock and joint noises but some inflammatory disorders including retrodiscitis can be managed with this appli-ance. Occlusal appliance therapy is a successful treatment in reducing symptoms, and many previous reports indi-cates that its success rate is 70-90%. However, controversy exists over the exact mechanism by which occlusal appliance reduce symptoms. Occlusal appliance therapy is reversible, non-invasive therapy and effective therapeutic modalities for tem-poromandibular disorders. For the successful outcome, careful selection of the patient is needed. Also, it should be monitored regularly for the improvement of the disorder and the occurrence of side effects.

Degradation of Soft Epoxy Resin for Cable Penetrations Induced by Simulated Severe Accidents

To obtain the knowledge that contributes to the safer operation of nuclear power plants and their prompt recovery and termination in the event of an accident, soft epoxy resins with rubber-based additives—used as insulators and airtight sealants in electrical penetrations in nuclear power plants—were aged under several simulated severe accident environments with different conditions of heat, gamma rays, and exposure to superheated steam containing no oxygen. Then, changes in structural, dynamic mechanical, mechanical, and dielectric properties were examined. It has been found that this resin becomes hard as a result of cross-linking if aged by irradiation with gamma rays. Since the cross-linking slows down the molecular motions, the glass transition temperature increases, whereas the dielectric permittivity and the dielectric loss factor decrease unless the steam penetrates the sample. Although the sample melts and disappears if directly exposed to superheated steam at 171 °C or 200 °C, the irradiation with gamma rays conducted prior to the steam exposure can mitigate the hydrolysis induced by the steam. Although the soft epoxy resin shows drastic changes in various properties, its properties after the aging approach or exceed the corresponding ones of the non-degraded ordinary hard epoxy resin. Therefore, it seems that using soft epoxy resin according to its purposes would not be a problem.

Structural design to enhance mechanical properties of carbon-fiber-reinforced thermoplastics using colloidal particles and soft and hard resins

Carbon-fiber-reinforced plastics (CFRPs) can facilitate vehicular weight reduction and thus have attracted significant attention in the automobile industry. Currently, a thermosetting resin is commonly used as a CFRP matrix, and carbon-fiber-reinforced thermoplastics (CFRTP) have been widely investigated owing to their low weight and utility in mass production. However, the materials used in vehicles must have high energy absorption, i.e., high residual stress. Herein, the surface modification of carbon fibers with thermoplastic particles were modified to improve the interfacial properties of the carbon fibers and thermoplastic resin and enhance the bending strength of the CFRTP. Furthermore, the energy absorption of the CFRTP was improved by incorporating two different thermoplastic resins into the structure; a high impact strength polymer alloy (HISPAT) provided by Toyota Boshoku that served as a soft layer, and polyamide 6 (PA6), known as engineering plastic, as a hard layer. Furthermore, structural design was improved to enhance the energy absorption and strength of the CFRTP.

The Effect of Red Sirih Leaf Drinking (Piper Crocatum) Towards Resin Violence Composites of Nanofiller in Laboratory of Makassar Working Center

Background. To determine the effect of soaking red betel leaves against the hardness of nanofillercomposite resins. Materials and Methods. The research applied True Experimental Laboratory methodwith one group pretest posttest. The 18 samples of nanofiller composite resin were obtained throughpurposive sampling. The samples were light cured then soaked in red betel leaf solution for 28 minutes.Then, the hardness measurements were performed using VickerHardness Tester. Results. The results ofpaired sample t-test indicated the effect of soaking red betel leaf (p 0.002 &lt;0.05) and sterile aquadest (p0.026 &lt;0.05) on the surface hardness of nanofiller composite resin. Conclusion. The effect of soakingred betel leaves on the surface hardness of nanofiller composite resin was obtained.

Strength and Surface Properties of a 3D-Printed Denture Base Polymer.

This in vitro study evaluated the flexural strength, impact strength, hardness, and surface roughness of 3D-printed denture base resin subjected to thermal cycling treatment. According to ISO 20795-1:2013 standards, 120 acrylic resin specimens (40/flexural strength test, 40/impact strength, and 40/surface roughness and hardness test, n = 10) were fabricated and distributed into two groups: heat-polymerized; (Major.Base.20) as control and 3D-printed (NextDent) as experimental group. Half of the specimens of each group were subjected to 10,000 thermal cycles of 5 to 55°C simulating 1 year of clinical use. Flexural strength (MPa), impact strength (KJ/m2 ), hardness (VHN), and surface roughness (μm) were measured using universal testing machine, Charpy's impact tester, Vickers hardness tester, and profilometer, respectively. Data were analyzed by ANOVA and Tukey honestly significant difference (HSD) test (α = 0.05). The values of flexural strength (MPa) were 86.63 ± 1.0 and 69.15 ± 0.88; impact strength (KJ/m2 )-6.32 ± 0.50 and 2.44 ± 0.31; hardness (VHN)-41.63 ± 2.03 and 34.62 ± 2.1; and surface roughness (μm)-0.18 ± 0.01 and 0.12 ± 0.02 for heat-polymerized and 3D-printed denture base materials, respectively. Significant differences in all tested properties were recorded between heat-polymerized and 3D-printed denture base materials (P < 0.001). Thermal cycling significantly lowered the flexural strength (63.93 ± 1.54 MPa), impact strength (2.40 ± 0.35 KJ/m2 ), and hardness (30.17 ± 1.38 VHN) of 3D-printed resin in comparison to thermal cycled heat-polymerized resin, but surface roughness showed non-significant difference (p = 0.262). 3D-printed resin had inferior flexural strength, impact strength, and hardness values than heat-polymerized resin, but showed superior surface roughness. Temperature changes (thermal cycling) significantly reduced the hardness and flexural strength and increased surface roughness, but did not affect the impact strength.

The Impact of Artificial Aging on the Color Stability and Hardness of Nanocomposite Resin

Objective: This study aimed to investigate the impact of artificial aging on the color stability and hardness of nanocomposite resin.Methods: Four nanocomposite resin materials were used: Filtek Z350 XT (FZ), Synergy D6 (SD), Grandio (GD), and Clearfil Majesty Esthetic (CM). Thirty specimens were created from each material, which were divided into three (A,B,C) groups of 10 specimens each. For each material, the values of visual lightness (L*), degree of redness and greenness (a*), and degree of yellowness and blueness (b*) of the specimens in group A before and after aging, as well as the hardness of the specimens in group B before aging and in group C after aging, were measured. The American Society for Testing and Materials (ASTM) G155 Cycle 1 standard was adopted to test the aging of the specimens. The color difference (ΔE00) value and hardness difference (ΔH) value of the specimens before and after aging were calculated.Results: Aging was found to have an impact on the ΔE00 values of the resin materials in each group (H = 17.6, p = 0.001), and the hardness of the specimens in each group after artificial aging was significantly higher than before aging (p &amp;lt; 0.05). The difference in ΔE00 between the FZ group and the SD, GD, and CM groups was statistically significant (p &amp;lt; 0.05). The FZ group had the highest ΔE00 values. There was no correlation between ΔE00 and the hardness change percentage after aging (r = 0.114).Conclusion: Among the four nanocomposite resins tested in this study, except for Filtek Z350 XT’s ΔE00 values (&amp;gt;1.8) in the clinically unacceptable range, the remaining three kinds of resin ΔE00 values (&amp;lt;1.8) were all in the clinically acceptable range. The hardness of the four nanocomposite resins increased after aging. The results of the present study revealed that there was no correlation between ΔE00 and hardness change percentage in the four nanocomposite resin materials after aging.

Hardness of Resin Cements Polymerized through Glass-Ceramic Veneers.

(1) Background: The aim of this study is to evaluate the hardness of resin cements polymerized through ceramic disks under different process factors (ceramic type and thickness, light-polymerization units and polymerization time); (2) Method: Three types of ceramic blocks were used (IPS e.max CAD; Celtra Duo; VITABLOCS). Ceramic disks measuring 0.5 mm, 1.0 mm and 1.5 mm were cut from commercial blocks. Two resin cements (Rely X Veneer and Variolink Esthetic) were polymerized through the ceramic specimens using distinct light-polymerization units (Deep-cure; Blue-phase) and time intervals (10 and 20 s). Hardness of cement specimens was measured using microhardness tester with a Knoop indenter. Data were statistically analyzed using factorial ANOVA (α = 5%); (3) Results: Mean microhardness of Rely X Veneer cement was significantly higher than that of Variolink Esthetic. Deep-cure resulted in higher mean microhardness values compared to Blue-phase at 0.5- and 1-mm specimen thicknesses. Moreover, a direct correlation was found between polymerization time and hardness of resin cement; (4) Conclusions: Surface hardness was affected by resin cement type and ceramic thickness, and not affected by ceramic types, within evaluated conditions. Increasing light-polymerization time significantly increased the hardness of the cement.

The Effect of Bleach Liquid and Household Cleaner on Surface Hardness and Roughness of Acrylic Base of Orthodontic Appliances

Introduction: The daily use of orthodontic removable plates can interfere with the self-cleansing function of the mouth. Although various techniques have been proposed for cleaning removable orthodontic appliances, there is no consensus on the use of a safe method that preserves the physical properties of the appliance. This study aimed to investigate the effect of using hydrochloric acid (10%, for removal of mineral deposits) and sodium hypochlorite (5.25%, to remove organic matter and discolorations) on surface hardness and roughness of self-cure orthodontic acrylic resins. Materials &amp; Methods: This cross-sectional laboratory study was conducted in the fall of 2017 at Isfahan University of Medical science and Isfahan University of Technology. In this study two orthodontic acrylic resins (Orthocryl® and Acropars®) were used. Eighty samples (12×10×3 mm) from each one were fabricated and divided into four groups (n = 20). Group 1: 15 minutes immersion in household cleaner liquid (Hydrochloric acid, 10%) followed by15 minutes immersion in household bleach liquid (Sodium Hypochlorite, 5.25%). In group 2, immersions were repeated just like group two times and in group 3, were done three times. Group 4 was as control and had no immersion. The surface hardness and roughness of samples were measured. Data were analyzed with Two Way ANOVA and the significance level was set at 0.05. Results: The number of immersion procedures did not significantly affect the surface hardness (p value = 0.958) and surface roughness (p value = 0.657) in the different study groups. There was no significant difference in the surface hardness between the two acrylic resin brands (p value = 0.077); however, Acropars acrylic resin samples exhibited significantly higher surface roughness compared to the Orthocryl acrylic resin samples(p value &lt; 0.001). Conclusion: 15 minutes of immersion in 10% HCl, followed by 15 minutes of immersion in 5.25% NaOCl and repetition of the procedure three times did not significantly affect the surface hardness and roughness of self-cured acrylic resins.

Optimization of performance and exhaust emissions of single-cylinder diesel engines fueled by blending diesel-like fuel from Yang-hard resin with waste cooking oil biodiesel via response surface methodology

The objective of this research was to examine the optimization of performance and exhaust emission of a single-cylinder diesel engine in terms of blending diesel-like fuel (DLF) with waste cooking oil biodiesel (WCOB) and engine speed. This is the first study on the use of pyrolytic oil from Yang hard resin (HY) to investigate the performance of diesel engines. Different mixing ratios of WCOB in diesel-like fuel (DLF) from HY (6–34% Vol) and engine speed (1034–2166 rpm) were used as input factors in the response surface methodology (RSM) model. The experiment was designed using an RSM model with a rotatable central composite design (RCCD). All models obtained from engine performance and emission variables were statistically significant at a 95% level. The interactive results were presented between variables and responses. The DLF-WCOB blends showed a positive impact on both engine performance and exhaust emissions. The desirability approach-based RSM was used to predict the optimal conditions of engine operation whose parameters were predicted to be 23% waste cooking oil biodiesel and 1700 rpm engine speed. The results of brake torque, brake power, BSFC, BTE, CO, CO2, and NOX at optimal parameters were 28.4 Nm, 5.0 kW, 253 g/kWh, 32.99%, 0.48%, 12.53% and 133.4 ppm, respectively. RSM was powerful enough to predict the intended response parameters of this study. The DLF-WCOB (~20%) blend can be used as an alternative diesel engine fuel.

BASIC PROBLEMS WITH THE USE OF RESILIENT DENTURE LINING MATERIALS: LITERATURE REVIEW

Complicated cases in the treatment of totally edentulous patients, as well as in the fabrication of obturators and epitheses, require the use of resilient lining materials (RLMs). These materials have several disadvantages, which is why many dental practitioners do not recommend them. The tendency to breaking the bond between the hard acrylic resin and the resilient liner is a fact with unpleasant consequences, mainly found with the use of cold-curing silicone-based resilient liners. Methods to improve the bond between the hard denture base and the RLM have been the subject of numerous publications. The efforts of the authors are focused in two directions: mechanical or chemical treatment of the denture base or a combination of both. Other commonly discussed problems with the use of RLMs are the difficult and even impossible repair and the retention of oral fluids, fungi and other microorganisms due to the porosity of RLMs. Despite the wide variety of tools offered by different manufacturers, the issue of optimal and high-quality mechanical treatment of the polymerized resilient material has not yet been fully resolved.