Composite Discs Research Articles

Shear Bond Strength of Veneering Composite Versus Different Polyetheretherketone Materials after Various Surface Treatments: An In-vitro Study

Introduction: Polyetheretherketone, also known as PEEK, is a semicrystalline thermoplastic material with many advantages. Since its grey material, it has to veneering with composite resin to enhance its aesthetic appeal. Bonding PEEK and composite veneers poses challenges due to its inert surface. Aim: To assess and compare the Shear Bond Strength (SBS) between various polyetheretherketone materials and veneering composites following various surface treatments. Materials and Methods: The in-vitro study was conducted at KSR Dental College and Hospital in Tiruchengode, Tamil Nadu, India, over a period of three months from December 2022 to February 2023. A total of 108 PEEK discs were prepared for the study, divided into three groups: unfilled PEEK, 30% carbon reinforced PEEK, and 10% carbon + 10% graphite + 10% Polytetrafluoroethylene (PTFE) reinforced PEEK. The specimens underwent different surface treatments, including no treatment, sandblasting with 110 um alumina particles, and acid etching with 98% sulphuric acid. Additionally, 108 composite discs were prepared and bonded to the PEEK specimens using adhesive and resin cement. The bonded specimens were immersed in distilled water for 24 hours, and the Shear Bond Strength (SBS) was determined using a universal testing machine. Statistical analysis was performed using one-way ANOVA, and mean values were compared using posthoc tests. Results: The results indicated significant variation in SBS among the three groups without treatment (p=0.011) and after sandblasting with 110 um alumina (p=<0.001). The 30% carbon reinforced PEEK exhibited the highest SBS regardless of the surface treatments. Conclusion: Among the tested materials, 30% carbon reinforced PEEK demonstrated the highest SBS, regardless of the surface treatments. Acid etching yielded the highest SBS among the various surface treatments, irrespective of the type of PEEK material used.

Abrasive resistance and microhardness of self-adhesive (Surefil one) and conventional bulk fill composites: An- in vitro study.

Aims and objectives: To evaluate abrasive resistance and microhardness of self-adhesive Surefil one and conventional bulkfill composites Beautifil bulk restorative and Filtek one bulk fill restorative. Materials and Methods: For the abrasive resistance test, thirty composite discs (4 mm hieght×8 mm width) in each group (n=10) were fabricated. GI: Beautifil bulk restorative, GII: Filtek One Bulk fill restorative and GIII: Surefil one self-adhesive. By placing the material in a mold in a single increment then curing. A custom-made toothbrush simulator was employed for wear testing. The samples weighted before and after the brushing to measure the weight loss. For the microhardness test, thirty cylindrical specimens (6 mm× 8 mm) (n= 10) were fabricated to assess the microhardness, top and bottom surfaces were tested using Vicker Hardness test. The results were analyized with a one-way ANOVA test, the post-hoc comparisons were examined in Tukey test. Results: Abrasive Resistance results, Surefil one (9.52gr) and Beautifil bulk (4.16gr) showed an increase in weight after brushing, while Filtek one bulkfill (-0.85gr) showed a decrease in weight.Microhardness test results, Beautifil bulk showed the highest number of VH (74.83) followed by Surefil one (70.61) and Filtek one bulkfill (62.95). Conclusion: Beautifil bulk was more resistant to abrasion in comparison to Surefil one self-adhesive and One bulk fill. The great weight loss was observed in One bulk fill. Great weight gain was observed in Surefil one self-adhesive. Beautifil bulk showed the highest VH number compare to Surefil one self-adhesive and One bulk fill. Filtek one bulk fill showed low resistance and low hardness number. Keywords: Bulk fill, Self-adhesive, Abrasive resistance, Microhardness Composite, Surefil one

Effects of Novel Dental Composites on Streptococcus mutans Biofilms.

With the phase-out of amalgam and the increase in minimally invasive dentistry, there is a growing need for high-strength composite materials that can kill residual bacteria and promote tooth remineralization. This study quantifies how antibacterial polylysine (PLS) and re-mineralizing monocalcium phosphate monohydrate (MCPM) affect Streptococcus mutans biofilms and the strength of dental composites. For antibacterial studies, the MCPM-PLS filler percentages were 0-0, 8-4, 12-6, and 16-8 wt% of the composite filler phase. Composite discs were immersed in 0.1% sucrose-supplemented broth containing Streptococcus mutans (UA159) and incubated in an anaerobic chamber for 48 h. Surface biomass was determined by crystal violet (CV) staining. Growth medium pH was measured at 24 and 48 h. Biofilm bacterial viability (CFU), exo-polysaccharide (water-soluble glucan (WSG) and water-insoluble glucan (WIG)), and extracellular DNA (eDNA) were quantified. This was by serial dilution plate counting, phenol-sulfuric acid microassay, and fluorometry, respectively. The biaxial flexural strengths were determined after water immersion for 1 week, 1 month, and 1 year. The MCPM-PLS wt% were 8-4, 8-8, 16-4 and 16-8. The normalized biomass, WSG, and WIG showed a linear decline of 66%, 64%, and 55%, respectively, as the PLS level increased up to 8%. The surrounding media pH (4.6) was all similar. A decrease in bacterial numbers with the 12-6 formula and a significant reduction with 16-8 compared to the 0-0 formulation was observed. The eDNA concentrations in biofilms formed on 12-6 and 16-8 formulations were significantly less than the 0-0 control and 8-4 formulations. Doubling MCPM and PLS caused a 14 and 19% reduction in strength in 1 week, respectively. Average results were lower at 1 month and 1 year but affected less upon doubling MCPM and PLS levels. Moreover, a 4% PLS may help to reduce total biomass and glucan levels in biofilms on the above composites. Higher levels are required to reduce eDNA and provide bactericidal action, but these can decrease early strength.

Effect of saliva of patients with leukemia on surface hardness and roughness of enamel and dental composite resin during chemotherapy regimen: An – Invitro study

Background: Evaluate the surface roughness and hardness of tooth enamel and dental resin composite restoration immersed into saliva collected from leukemia patient. Objective: To evaluate the surface roughness and hardness of tooth enamel and dental resin composite restoration immersed on to saliva collected from 4 types of leukemia patient. Patients and Methods: 30 patients with 4 types of leukemia (Acute lymphoblastic leukemia ALL, Acute myeloid leukemia AML, Chronic lymphocytic leukemia CLL, and Chronic myeloid leukemia CML) were included for taking saliva separately. A total number of 50 enamel specimen and 50 of composite resin disk were prepared and randomly divided into 5 groups of enamel (1,2,3,4, and 5) and 5 groups of composite resin disk (A,B,C,D, and E), surface roughness and hardness were measured and data collected, group A and 1 were immersed in artificial saliva for 7 days as control, group B and 2 immersed into saliva collected from patient with ALL, group C and 3 immersed into saliva collected from patient with AML, group D and 4 immersed into saliva collected from patient with CLL and group E and 5 immersed into saliva collected from patient with CML all group for 7 days then surface roughness and hardness were measured data collected and analyzed and statistically significant regarded at p<0.05. Results: In group A and 1 artificial saliva there were no significant effect on surface roughness and hardness of both enamel and composite resin disk, while surface roughness and hardness of enamel and composite resin significantly changed after immersing in saliva of ALL, AML, CLL, patients and surface roughness of composite resin highly significantly increased after immersing in saliva of CML patients. Conclusion: Saliva of ALL, AML, CLL, and CML seems to significantly changes in mechanical properties of enamel and composite, however saliva of CML highly significantly increase surface roughness of composite resin. Keywords: 4 types’ leukemia, chemotherapy, surface roughness and hardness, enamel, dental composite resin.

Effect of saliva of patients with leukemia on surface hardness and roughness of enamel and dental composite resin during chemotherapy regimen: An – Invitro study

Background: Evaluate the surface roughness and hardness of tooth enamel and dental resin composite restoration immersed into saliva collected from leukemia patient.
 Objective: To evaluate the surface roughness and hardness of tooth enamel and dental resin composite restoration immersed on to saliva collected from 4 types of leukemia patient.
 Patients and Methods: 30 patients with 4 types of leukemia (Acute lymphoblastic leukemia ALL, Acute myeloid leukemia AML, Chronic lymphocytic leukemia CLL, and Chronic myeloid leukemia CML) were included for taking saliva separately. A total number of 50 enamel specimen and 50 of composite resin disk were prepared and randomly divided into 5 groups of enamel (1,2,3,4, and 5) and 5 groups of composite resin disk (A,B,C,D, and E), surface roughness and hardness were measured and data collected, group A and 1 were immersed in artificial saliva for 7 days as control, group B and 2 immersed into saliva collected from patient with ALL, group C and 3 immersed into saliva collected from patient with AML, group D and 4 immersed into saliva collected from patient with CLL and group E and 5 immersed into saliva collected from patient with CML all group for 7 days then surface roughness and hardness were measured data collected and analyzed and statistically significant regarded at p<0.05.
 Results: In group A and 1 artificial saliva there were no significant effect on surface roughness and hardness of both enamel and composite resin disk, while surface roughness and hardness of enamel and composite resin significantly changed after immersing in saliva of ALL, AML, CLL, patients and surface roughness of composite resin highly significantly increased after immersing in saliva of CML patients.
 Conclusion: Saliva of ALL, AML, CLL, and CML seems to significantly changes in mechanical properties of enamel and composite, however saliva of CML highly significantly increase surface roughness of composite resin.

Preparation of apricot kernel shell powder added polyester/calcium carbonate composite discs and investigation of their abrasive properties

Apricot kernel shell is suitable filler for abrasive materials with its strong, hard structure and dense cellulose content. Therefore, within the scope of this study, polyester composite (PE-CAC) discs containing apricot kernel shell powder were prepared in order to prepare abrasive polyester composite discs. In order to prevent these discs from damaging the surface on which they are applied during use, different amounts of calcium carbonate were added into the structure. The chemical structure of the obtained composite discs was confirmed by Fourier transform infrared spectroscopy. Surface morphology and structure were confirmed by scanning electron microscopy technique. The distribution of additives within the composite structures was examined by EDX spectroscopy. The effect of heat generated during the etching process on the composite disc structure was investigated using thermal analysis techniques. The added composite structures were transformed into cylindrical discs with a diameter of 45 mm and a height of 30 mm and were used to remove paint on metallic surfaces. As the amount of apricot kernel shell powder in the composite structure increases, the abrasion efficiency increases. Additionally, as the PE/CaCO3 composite disc application time increased, a significant decrease in surface roughness was observed. Ideal surface roughness was achieved, especially after 10 seconds of application time. As a result, PE/CaCO3 composite discs with apricot kernel additives present an important alternative to existing methods, especially in the cleaning of dirt, rust and paint on metallic surfaces.

Study on micro-turbojet engine with high thrust-to-weight ratio

Micro-turbojet engine refers to a closed cycle gas turbine engine with thrust below 500kg and power below 100kW. The performance indicators of domestic products are relatively low, and the main problems of domestic products are low thrust-to-weight ratio, poor reliability, and low heat resistance. The low working efficiency of the components and the short life limit the performance of the aircraft. In this paper, a micro-turbojet engine with a higher thrust-to-weight ratio and higher heat tolerance has been designed. The hollow centrifugal impeller with a built-in skeleton structure is successfully developed. The integrated design of the evaporation tube guide and shaft sleeve diffuser solves the problems of poor stability and high production cost, reduces the heat loss, and improves the overall efficiency. Ceramic matrix composite integral turbine disk makes the engine achieve breakthroughs in thrust-to-weight ratio, reliability, and heat tolerance. In addition, the engine has been tested to prove its feasibility. This paper may offer a reference for the design of micro-turbojet engine.

Investigation of stresses in a Kevlar (491PR-286) material disc by the Chebyshev pseudospectral method

In this study, a composite disc with Kevlar (491PR-286) material was modeled. Kevlar consists of very strong fibers of very light carbon origin. That is why they are used quite often in unmanned aerial vehicles and spacecraft. The disc has been subjected to thermal stress under a linearly increasing temperature distribution. The temperature limit conditions were applied as 25 °C, 50 °C, 75 °C, 100 °C, and 150 °C. The obtained findings were determined using a computer program, the psedudospectral Chebyshev method, and analytically in three different ways. The main difference between this study and other studies is that it investigates the thermal stresses occurring in circular discs using different methods. The results obtained are compared fairly among themselves and presented with graphs. It was determined that tangential stresses were higher than radial stresses at the studied temperature values. In the analytical study conducted, the radial stresses on the inner and outer surfaces of the disc were determined to be zero for the boundary conditions. Under the increasing temperature distribution from the inner surface to the outer surface, tangential stresses occurred as tensile stress on the inner part of the disc and compressive stress on the outer part. Under the decreasing temperature distribution from the inner surface to the outer surface, tangential stresses are pressed on the inner part of the disc, resulting in a tensile stress on the outer part. It is observed that with increasing temperature, there is an increase in radial and tangential stress values. At the end of the study, it was concluded that Kevlar (491PR-286) material discs can be used at high temperatures.

The influence of core-build up materials on biaxial flexural strength of monolithic strength-gradient zirconia; an in-vitro study

BackgroundSince their introduction, there has been limited research regarding the mechanical properties of novel strength-gradient monolithic zirconia. In addition to that, studies evaluating the effect of different core-build materials on the strength of indirect restorations are scarce. Therefore, the aim of this study was to investigate the effect of using different core build-up materials on biaxial flexural strength of a new monolithic multilayered zirconia material.MethodsForty zirconia discs were fabricated from IPS e.max ZirCAD Prime (Ivoclar Vivadent AG, Schaan, Liechtenstein) and divided into 2 groups (n = 20). Forty composite discs were prepared from Tetric N-Ceram (Ivoclar Vivadent AG, Schaan, Liechtenstein) and MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein). The zirconia discs were adhesively cemented to the 2 types of composite forming 2 groups (Zirconia-Tetric N-Ceram and Zirconia-MultiCore Flow). Biaxial flexural strength was determined using a piston-on-3-ball test. The data were statistically analyzed with an independent t-test for significant differences (p = 0.05).ResultsTetric N-Ceram had significantly higher strength than MultiCore Flow (p < 0.001) but no statistically significant differences were found in strength values between Zirconia-Tetric N-Ceram and Zirconia-MultiCore Flow bilayered samples (p = 0.27).ConclusionsIt was concluded that although the tested composite core materials significantly differ in their biaxial flexural strength values, they had no influence on the biaxial flexural strength of the overlying zirconia.

PEEK surface treatment on surface roughness and bond integrity to composite resin utilizing Er: YAG, Rosebengal activated by PDT, and aluminum trioxide particles

AimsTo evaluate the impact of conditioning protocols, aluminum trioxide (Al2O3), Er:YAG laser (EYL), and Rosebengal (RB), on the surface roughness (Ra) and shear bond strength (SBS) of polyetheretherketone (PEEK) attached to composite restorations. MethodEighty PEEK discs in total were produced and then divided into four groups (n = 20). Group1:Sulfuric acid (SA), Group 2: PDT (RB), Group 3: Al2O3, Group 4 EYL, respectively. The Ra of PEEK discs was evaluated using the surface profilometer. After being luted, the discs were attached to composite resin discs. After that, samples were put to SBS testing on a Universal testing apparatus. A stereo microscope was also used to evaluate the type of breakdown. The data were analyzed using Tukey's test and one-way analysis of variance. ResultsThe SA treated group exhibited the highest Ra. Nevertheless, the RB specimens activated by PDT treatment had the lowest mean Ra score. The group that received the treatment of SA exhibited the highest average score of SBS. In contrast, specimens treated with PDT and activated by RB exhibited the lowest levels of bond fidelity. Cohesive failure emerges as the prevailing kind of fracture within the various groups subjected to testing. ConclusionThe utilization of Al2O3, RB activated by PDT, and EYL shows promise as a viable substitute for Sulfuric acid in enhancing the bond integrity of composite cement and surface roughness in PEEK materials

An In Vitro Study regarding the Wear of Composite Materials Following the Use of Dental Bleaching Protocols.

Composite materials used in dental restorations are considered resistant, long-lasting and aesthetic. As the wear of restorations is an important element in long-term use, the aim of this study was to evaluate the surface condition of nanohybrid and microfilled composite resins, after being subjected to the erosive action of dental bleaching protocols. This paper reflects a comparative study between one nanofilled composite and three microfilled composites used in restorations. For each composite, three sets of samples (under the form of composite discs) were created: a control group, an "office bleach" group with discs bleached with 40% hydrogen peroxide gel, and a "home bleach" group with discs bleached with 16% carbamide peroxide gel. Wear was numerically determined as the trace and the coefficients of friction obtained using a tribometer, the ball-on-disk test method, and two balls: alumina and sapphire. For all composite groups, there were statistically significant differences between the wear corresponding to the control and bleaching groups, for both testing balls. Regarding the composite type, the largest traces were recorded for GC Gradia direct anterior, for all groups, using the alumina ball. In contrast, for the sapphire ball, 3M ESPE Filtek Z550 was characterized by the largest traces. With respect to the friction coefficients, the "office bleach" group recorded the largest values, no matter the composite or the ball type used. The 3M ESPE Valux Plus composite recorded the largest friction coefficients for the alumina ball, and 3M ESPE Filtek Z550 for the sapphire ball. Overall, the "office bleach" group was characterized by higher composite wear, compared to the "home bleach" protocol or control group. Nanofilled composite resins showed superior wear resistance to microfilled resins after undergoing a bleaching protocol.

Evaluating lightweight gear transmission error: a novel nonlinear finite element approach using direct constraint contact algorithm

With the growing demand for lightweight gear transmission systems, composite materials have emerged as a promising solution due to their high specific properties. However, the complexity of designing gear pairs with composite materials necessitates the development of reliable numerical procedures. This study presents a robust numerical approach using a flexible multibody method through the MSC MARC solver to accurately estimate static transmission error (STE) in lightweight gears, considering the nonlinear behavior caused by gear contact. The Finite Element (FE) model uses the Multi-Point Constraint equations (MPCs) to ensure the non-penetration condition considering a node-to-surface contact detection. The proposed method is compared against commercial software for standard gear pair cases, demonstrating its effectiveness in addressing complex structures based on composite materials. The numerical procedure is further applied to analyze hybrid metal-composite gear pairs and compared to a holed one. The results provide insights into the time evolution and harmonic components of STE, highlighting the advantages of hybrid gears in terms of reduced vibrations and noise for the same mass reduction compared to holed gears. Additionally, ply arrangements resulting in quasi-isotropic properties of the composite disc are compared to unidirectional laminates to highlight the fiber orientation effect on the STE results.

Dentin bond strength and antimicrobial activities of universal adhesives containing silver nanoparticles synthesized with Rosa canina extract.

The purpose in the study was to evaluate the effect of biogenic silver nanoparticles (Ag NPs) synthesized by the green synthesis method on dentin bond strength in three different universal adhesives and investigate their antibiofilm activity against Streptococcus mutans (S. mutans). Three different universal adhesives (single bond universal, all-bond universal, and clearfil universal) were used in this study. Ag NPs were synthesized using rose hip (Rosa canina) extract as a reducing and stabilizing agent and they were characterized with STEM, UV-vis spectrophotometer, DLS, and zeta potential. Ag NPs were added to the adhesive resins at a rate of 0.05% (w/w), and their homogeneous distribution in the adhesive was determined using EDX spectrometry. Samples in all groups were tested at baseline-after 5000 and 10,000 thermal cycles. Adhesive composite discs were used for the live/dead analysis of S. mutans, MTT metabolic activity test, lactic acid production, and determination of colony-forming unit (CFU) values (n = 3). Ninety extracted caries-free human third molars were used to determine microtensile bond strength (μTBS) (n = 10). After the universal adhesive was applied to the dentin surface, composite resin (Z550 XT, 3M ESPE, USA) was placed and sections were taken to form a composite-dentin stick of 1mm × 1mm wideness and 8-mm length. The sticks were broken at a rate of 1mm/min under uniaxial tension in a universal testing machine, and the failure modes were determined by SEM. One-way analysis of variance (ANOVA) for antibacterial tests and two-way analysis of variance for μTBS tests were performed (p < 0.05). All universal adhesive groups containing Ag NPs showed higher antibacterial activity than control groups without Ag NPs (p < 0.05). There was a statistically significant difference in the live/dead assay analysis, MTT metabolic activity test, lactic acid production, and CFU values in the thermal cycled Ag NPs groups (p < 0.05). Antibacterial activity decreased in groups containing Ag NPs subjected to 10,000 thermal cycles. The highest lactic acid production 11.06 (± 0.629) and CFUs 7.61 (± 0.304), live bacteria 31.13 (± 0.466), and S. mutans MTT metabolic activity 0.29 (± 0.376) at AU (All-Bond Universal-Ag NPs) 10,000 thermal cycles group. There was no difference in μTBS values between the initial and 5000 thermal cycle groups, there was a difference between the 10,000 thermal cycle groups. The CU (Clearfil Universal-Ag NPs) group subjected to 10,000 thermal cycles showed lower μTBS 11.1 (± 3.2). In conclusion, universal adhesives containing biogenic Ag NPs showed higher antibacterial activity than the control groups and did not reduce the μTBS. Antibacterial universal adhesives can contribute to restoration success in clinical applications by reducing residual bacteria and preventing secondary caries formation.

Effect of Different Mouthwashes on Stain Susceptibility of Resin Composite in Contact with Beverages.

Objectives: This study aimed to investigate the effect of common mouthwashes on the color change of a nanohybrid composite and its further stain susceptibility to Coke and coffee. Materials and Methods: One hundred and fifty composite discs were prepared and initial color values were measured using a spectrophotometer. The specimens were grouped based on the 24h exposure to common mouthwashes including Listerine, chlorhexidine, two types of fluoride mouthwashes (alcohol free and alcohol containing) as well as distilled water as control (N=30). The color change (ΔE1) values were calculated to show the amount of color change caused by mouthwashes. Subsequently, the specimens in each group were subdivided and immersed in the secondary colorant solution (coffee, Coke and, distilled water) for seven days. The total color change (ΔE total) values were obtained to show the stain susceptibility. Statistical analysis was conducted using ANOVA and Tukey's post hoc test. A P-value less than 0.05 was considered statistically significant. Results: The calculated ΔE1 of resin composite was significantly higher for all mouthwash groups than that of the control group; however, all were in the clinically acceptable range. Exposure to Listerine and distilled water caused more staining effects compared to other mouthwashes after immersion in secondary colorant solutions. Regardless of primary mouthwash type, coffee and distilled water caused the highest and the least total discolorations, respectively (P<0.001). Conclusion: All mouthwashes caused a clinically acceptable color change in resin composite; however, further stain susceptibility depended on the mouthwashes but was not higher than distilled water.

PEEK Surface Treatment Using Nd: YAG, Riboflavin Activated by PDT, and Alumina Particles on Surface Roughness, Bond Failure, and Bond Integrity to Composite Resin

Aims: Conditioning protocols, Airborne Particles of Alumina (ABP), Neodymium-Doped Yttrium Aluminium Garnet (Nd: YAG) laser, and Riboflavin (RF), were tested on PEEK disc bonded to composite restorations for surface roughness (Ra) and shear bond strength (SBS). Method and Material: Random sampling was used to divide 80 PEEK discs into four groups for surface conditioning. (n = 20). Group 1: Sulfuric acid (SA); Group 2: PDT (RF); Group 3: Alumina particle ABP; Group 4: NYL. Pretreated PEEK discs were measured for Ra using a surface profilometer. They were luted and bonded to composite resin discs. On Universal testing equipment, SBS was tested. Stereomicroscopes analyzed failure type. Data was analyzed using one-way ANOVA and Tukey’s test. Results: The SA-treated group had the highest Ra (1.411 ±0.043 μm). However, PDT (RF) treated tissues had the lowest mean Ra score (1.299 ± 0.019 μm). Regarding SBS, the SA-treated group (11.83±0.82 MPa) had the highest mean score. PDT (RF) (10.23±0.64 MPa) treated specimens showed the lowest bond integrity values. The most common fracture type in all investigated groups is cohesive failure. Conclusion: Airborne alumina, riboflavin, and Nd: YAG laser could replace PEEK sulfuric acid to improve composite cement bond integrity and surface roughness.

Analytical solution for fractional order temperature distribution in two dimensional multilayer composite circular discs

This article deals with mathematical approach to discuss the time-fractional heat conduction in two dimensional multilayer circular discs. The fractional order heat conduction equation is generated by using caputo time derivative. All the layers of the two dimension multilayer circular are assume to be thermally isotropic and making a perfect thermal contact. The boundary and interface conditions are expressed by the Riemann-Liouville derivative and the combination of first and second kind boundary condition in angular direction of the circular disc and for the third kind boundary condition in the radial direction. This solution is also applicable for composite multiple layers problem with inner radius may be zero. Three multiple layer problem studied numerically and graphically….

Particle size effect of PTFE on friction and wear properties of glass fiber reinforced epoxy resin composites

Self-lubricating spherical plain joint bearings play a crucial role in aerospace equipment, with their performance primarily depending on the self-lubricating materials positioned between the inner and outer rings. As a typical polymer-based self-lubricating material, glass fiber reinforced epoxy resin composites receive high expectations. Polytetrafluoroethylene (PTFE) as an additive can significantly improve the friction and wear performance of glass fiber reinforced epoxy resin composites. The primary objective of the present study is to reveal the effect law of PTFE particle size on friction and wear properties of glass fiber reinforced epoxy resin composites under dry sliding conditions. Hence, the four particle sizes (P1, average < 1 μm; P2, average 12 μm; P3, average 25 μm; P4, 75–180 μm) of PTFE-filled epoxy composites were prepared. The hardness, compressive strength, and compressive modulus of the epoxy resin composites filled with four particle sizes of PTFE were measured. The coefficient of friction (COF) was evaluated using a reciprocating ball-on-disk tribometer, with a GCr15 ball as the stationary part and the composite disc as the reciprocating component. The wear rate was determined using a Mahr profilometer. The results show that the friction coefficients of four PTFE-filled epoxy resin composites have little difference. However, the wear rate of epoxy composite filled with PTFE particles of the large size (RE/P4) is an order of magnitude lower than that of epoxy composites filled with PTFE particles of the other size. The wear morphology of the composites was analyzed by scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The higher wear resistance of RE/P4 can be attributed to it exhibiting a stronger role in anchoring glass fibers (GF), compared to other particle-sized PTFE-filled epoxy resin composite materials.

Effect of Lemon Juice, Apple Cider Vinegar and Green Tea on Microhardness of Nanohybrid resin composite: An In-vitro study

This study aimed to evaluate effect of Lemon Juice, Apple Cider Vinegar and Green Tea on microhardness of nanohybrid resin composite using vickers microhardness tester. Materials and methodology: Forty specimens of nanohybrid resin composite (3M ESPE Filtek Z350 XT) were prepared and polished the prepared discs using sandpaper. Before immersion of prepared composite discs in prepared solutions the baseline data of microhardness of each prepared composite discs were recorded by using Vicker’s microhardness tester. The prepared composite discs were divided into 4 groups (n=10) and alternatively immersed in 25 ml of prepared solutions namely Green tea, Apple Cider Vinegar, Lemon Juice and Artificial saliva for 5 sec and then in 25 ml of artificial saliva for another 5 sec and the procedure was repeated for 10 cycles. After following the above mentioned procedure, artificial saliva was used as storage media for 24 hours. For the next 28 days, this entire process was repeated. The microhardness test was carried out prior to immersion and then at intervals of 7, 14, 21 &amp; 28 days after immersion in respective solutions. Results: Two-way analysis of variance (ANOVA) with repeated measurements was carried out for the obtained data. Artificial Saliva demonstrated highest microhardness values at all time points, followed by Green Tea and Lemon Juice. Apple Cider Vinegar showed the least microhardness values of all the four groups tested. Conclusion: All the beverages significantly reduced surface microhardness of nanohybrid resin composite, especially at the end of 28 days. Immersion in apple cider vinegar caused more reduction in surface hardness over time when compared to other beverages. The outcome on microhardness of nanohybrid resin composite by these beverages on depended upon time the latter was exposed and also the chemical composition of beverages. Keywords: Apple Cider Vinegar, Green Tea, Lemon Juice, Microhardness, Nanohybrid resin composite, Vickers Microhardness Tester

In Vitro Evaluation of the Effects of Different Beverages on the Surface Microhardness of a Single-Shade Universal Composite.

The aim of this in vitro study was to analyze the influence of various beverages on the surface microhardness of a single-shade composite resin. Seventy-five Omnichroma composite discs were fabricated and divided into five subgroups according to the beverages. The groups were Group A: tea; Group B: coffee; Group C: beer; Group D: whisky; and Group E: artificial saliva. The samples were immersed in their respective beverages for 15 minutes per day for 15 days. The Vickers microhardness values were taken before and after the immersion of the composite disc samples in their respective beverages. A one-way analysis of variance (ANOVA) test was conducted using IBM SPSS Statistics software version 23 (IBM Corp., Armonk, New York, USA), with a statistical significance level of 5%. It was observed that there was a reduction in the surface microhardness of the composite resin after immersion in most of the solutions. An increase in the mean percentage change of surface microhardness was observed in the beer group (29%; mean difference = 16.52±12.05), followed by the coffee group (27.2%; mean difference = 15.51±9.28). The least mean percentage change in microhardness was noted in group E, artificial saliva (8.5%; mean difference = 4.81±3.04). The surface microhardness of composite resin can be influenced by the type of beverages used for immersion and the duration of immersion.However, it is important to note that the interaction between composite resin and various beverages is influenced by a complex interplay of multiple variables.

Application of modified articular disc anchorage in treating the perforation and rupture of temporomandibular joint disc.

This study aimed to use modified articular disc anchorage in treating old irreducible temporomandibular joint (TMJ) disc displacement with perforation and rupture, as well as to explore its efficacy. A total of 31 patients (34 sides) with 47 TMJ disc perforations who underwent surgical treatment in the Affiliated Stomatolo-gical Hospital of Nanchang University from January 2018 to December 2021 were selected. According to the location of disc perforation, it has five types: posterior disc perforation (typeⅠ), anterior disc perforation (typeⅡ), lateral disc perforation (type Ⅲ), composite disc perforation, and destruction disc perforation. The modified methods of disc anchoring were divided into two types according to the location of the perforation. TypesⅠandⅢ disc perforation were trea-ted by posterior anchoring method. For posterior ancho-ring, a screw was implanted into the posterolateral side of the condylar neck, and the disc was fixed on the screw by horizontal mattress suture. TypeⅡdisc perforation and compo-site disc perforation combined typeⅡperforation were treated by anterior and posterior double-anchoring method. For anterior anchoring, anchor screws or holes were placed at the anterior edge of the condylar neck, and horizontal mattress suture was performed at the posterior edge of the anterior perforation with an anchor wire. The articular disc was then fixed on the anchor screws or holes. For the posterior anchoring method, it was the same as the previous one. Paired t test was used to analyze the visual analog scale (VAS), maximum interincisal opening (MIO), and TMJ disorder index (CMI) of the patient before surgery and 1, 3, and 6 months after surgery. Disk-condyle position relationship by magnetic resonance imaging and postoperative quality of life in postoperative were analyzed. The incidence of perforation was 41.2% (14/34) in typeⅠ, 11.8% (4/34) in typeⅡ, 8.8% (3/34) in typeⅢ, 29.4% (10/34) in composite type, and 8.8% (3/34) in destruction type. The VAS, MIO, and CMI at 3, 6 months after operation significantly improved compared with those before operation (P<0.05). The effective reduction rate of disc was 96.77% (30/31). The quality of life at 6 months after surgery was 47.22±2.13, and the rate of excellent evaluation was 96.4% (27/28). Modified articular disc anchorage achieves a good curative effect for treating temporomandibular joint disc perforation and rupture. Nevertheless, its long-term effect requires further observation.