Polymethyl Methacrylate Specimens Research Articles

Evaluation of early bacterial adhesion on CAD/CAM dental materials: an in situ study.

The aim of this research was to determine if there are differences in early bacterial adhesion among CAD/CAM dental materials after 24h exposure in the oral environment. One hundred twenty specimens were prepared according to the manufacturer's recommendations and divided into six groups: RBC (resin-based composite), PMMA (polymethyl methacrylate), PEEK (polyether ether ketone), ZP (zirconia polished), ZG (zirconia glazed), and cobalt-chromium alloy (CoCr alloy). Twenty healthy participants were instructed to carry an intraoral device with six specimens, one per group, for 24h. Thereafter, real-time polymerase chain reaction (qPCR) and scanning electron microscopy (SEM) analyses enabled quantification and 2D view of biofilm formed on the specimens' surfaces. Kruskal-Wallis test and Dunn's post hoc analysis were used for inter-group comparison and data were presented as median (minimum-maximum). RBC specimens accumulated less bacteria, in comparison with ZG (p = 0.017) and PEEK specimens (p = 0.030), that dominated with the highest amount of adhered bacterial biofilm. PMMA, CoCr, and ZP specimens adhered more bacteria than RBC (p > 0.05), and less than ZG (p > 0.05) and PEEK (p > 0.05). The bacterial number varied considerably among participants. The obtained results enable a closer view into the susceptibility of CAD/CAM materials to microorganisms during the presence in the oral environment, which can be beneficial for a proper selection of these materials for a variety of dental restorations.

Surface Roughness of Polyetheretherketone Printed by Fused Deposition Modeling: A Pilot Study Investigating the Impact of Print Layer Thickness and Polishing Method

Polyetheretherketone is a high-performance thermoplastic polymer that can be used in 3D printing by fused deposition modeling, and is a promising material for dental applications. Some printing parameters are sensitive and can influence the properties of the printed object. Thus, this work aims to evaluate the influence of the print layer thickness on the surface roughness of polyetheretherketone before and after polishing and to verify the effectiveness of the polishing method used, as well as to compare it with the results obtained using polymethyl methacrylate as the control group. Specimens with different impression layer thicknesses were printed with polyetheretherketone (Group A—0.1 mm and Group B—0.3 mm). Additionally, a control group with polymethyl methacrylate specimens was milled. Roughness evaluation was conducted using a contact profilometer after the specimens had been printed (before polishing). Then, silicon carbide sandpaper was used to polish the surface, and the roughness was reassessed. Differences were observed between specimens regarding the print layer thickness and the roughness, with the 0.3 mm layer thickness showing the lowest roughness values. The results of this pilot study suggest that the surface roughness of fused deposition modeling printed polyetheretherketone is influenced by print layer thickness, with the lowest roughness seen at a thickness of 0.3 mm.

Mechanical properties and wear performance of denture base polymethyl methacrylate reinforced with nano Al2O3

Polymethyl methacrylate (PMMA) has been widely used as a material in dentistry. The deterioration of pure PMMA denture teeth is a significant issue that can alter the vertical dimensions of dentures. This study investigates the effect of aluminum oxide (Al2O3) nano-ceramic addition as reinforcements into the heat-cure acrylic resin denture teeth. The PMMA was reinforced with Al2O3 concentrations of 1, 3, 5, and 10 wt.%. The PMMA without ceramic addition is produced for comparison purposes. The color change, densification, microhardness, and compressive properties of the produced PMMA resin and its composites were investigated to detect the effect of Al2O3 nano ceramic addition on the physical and mechanical properties. Furthermore, the microstructure was also performed using scanning electron microscopy (SEM) analysis. A chewing simulator was utilized to conduct two-body wear testing, employing a human enamel antagonist. The wear behavior of the PMMA and their composites were assessed by measuring the weight loss after submitting them to 37,500 cycles. The SEM microstructure analysis revealed sound specimens of PMMA reinforced with 0, 1, 3, and 5 wt.% Al2O3 without any porosity and micro defects using the applied production procedures. In contrast, the aggregated sites and propagation of cracks were detected for the PMMA/10 wt.% Al2O3 specimen. The densification and hardness properties of the produced PMMA composites improved with increasing the Al2O3 additions. The microhardness of PMMA/10 wt.% Al2O3 improved by around 233% compared to the PMMA matrix. The higher compressive properties were detected for the PMMA/5 wt.% Al2O3 composite specimen with ultimate compressive strength (UCS) of 54.75 MPa and yield strength (YS) of 45.6 MPa and improved than the PMMA matrix by around 98 % and 117 %, respectively. In addition, incorporating Al2O3 nano-ceramic particles into a PMMA matrix revealed a significant improvement in the wear resistance of the produced composites compared to the PMMA matrix.

Fracture behavior in blasting under different static stresses and high stress unloading

AbstractIn this paper, the effects of static stresses on the blast‐induced crack in polymethyl methacrylate specimens with an empty hole were investigated by caustic system. The propagation behavior and re‐initiation process of blast‐induced crack under initial static stress and high stress unloading were investigated. The results show that when the direction of the empty hole is perpendicular to the static stress, the static stress reduces the length of the main crack. However, when the static stress is very high, the length of main cracks does not decrease. In addition, the static stress reduces the crack velocity and dynamic stress intensity factor (DSIF) and suppresses the increase of DSIFs and crack velocity due to reflected wave. The crack arrested under high stress unloading propagates again in the later stage. Moreover, the duration of high stress unloading lasts approximately 1 ms.

Enhanced antimicrobial efficacy of chlorhexidine-encapsulated halloysite nanotubes incorporated in presurgical orthopedic appliances: an in vitro, controlled study.

Presurgical infant's orthopedic appliances (PSIOs) play an increasingly crucial role in the interdisciplinary management of neonatal CLP, aiming to improve and maintain adequate nasolabial aesthetics, followed by primary lip/nasal surgery in both unilateral and bilateral CLP cases. The use of PSIOs in cleft lip and palate patients can lead to contamination with oral microflora, acting as a potential reservoir for infectious microorganisms. Acrylic surfaces might provide retention niches for microorganisms to adhere, and inhabit, which is difficult to control in immunocompromised patients, thus predisposing them to increased infection risks. The objective of this multi-assay in vitro study was to investigate the effects of incorporating chlorhexidine-loaded halloysite nanotubes (CHX-HNTs) fillers on the morphological, cytotoxic, release, and antimicrobial characteristics of self-cured acrylic polymethyl methacrylate (PMMA) material used in pre-surgical orthopedic appliances. Disk-shaped PMMA specimens were prepared with varying proportions of CHX-HNTs. A control group without any addition served as a reference, and four experimental samples contained a range of different concentrations of CHX-HNTs (1.0, 1.5, 3, and 4.5 wt%). The antimicrobial efficacy was assessed using an agar diffusion test against common reference microorganisms: Candida albicans, Staphylococcus aureus, Streptococcus pneumoniae, and Streptococcus agalactiae. Cytotoxicity was examined using the L929 cell line (mouse fibroblasts) through a (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide, MTT) cell viability assay. The release kinetics of CHX were monitored using UV-spectral measurements. The statistical analysis used a one-way ANOVA followed by Tukey's post hoc test. The integration of CHX-HNTs in PMMA exhibited a substantial dose-dependent antifungal and antibacterial effect against microorganisms at tested mass fractions (1.0 to 4.5 wt%). CHX release was sustained for up to 60 days, supporting prolonged antimicrobial activity. Furthermore, no significant cytotoxicity was determined in the L929 fibroblast cell line (control), indicating the biocompatibility of the CHX-HNTs-enhanced PMMA. Incorporating CHX-HNTs in PMMA successfully enhanced its antimicrobial properties, providing sustained CHX release and superior antimicrobial efficacy. These findings demonstrate the potential of antimicrobial nanoparticles in dental therapies to improve therapeutic outcomes. However, rigorous further clinical trials and observational studies are warranted to validate the practical application, safety, and efficacy. This study has the potential to make a major impact on the health of infants born with cleft lip and palate by helping to reduce the prevalence of infectious illnesses. The incorporation of CHX-HNTs into PMMA-based appliances is a novel promising preventive approach to reduce microbial infections.

Antifungal Effect and Durability of Chitosan Oligosaccharide Coating on Heat-cured Polymethylmethacrylate Surface

This study aimed to investigate the antifungal effect against Candida albicans (ATCC® 10231) and the durability of chitosan oligosaccharide (COS) coated on heat-polymerized polymethylmethacrylate (PMMA). The various concentrations of COS solution, 0.5, 1 and 2-fold of minimum fungicidal concentration (0.5, 1 and 2 MFC) were prepared and applied to PMMA specimens treated with sandblasting (SB), application of 3-aminopropyltriethoxysilane (APS), and a combination of both procedures (SB&APS). The toothbrush abrasion test was done to evaluate the remaining COS (n=10). The antifungal effect was determined through the colony count method (n=3). The number of fungal colonies was recorded at 16 and 48 hours. Data were analyzed using two-way and one-way ANOVA at the 95% confidence level. The result of the toothbrush abrasion test revealed that COS concentration and surface treatment affected coating durability. APS and SB&APS groups showed a high percentage of COS and significantly differed from SB groups (P = 0.00). For the antifungal effect, coatings with 1 MFC and 2 MFC demonstrated no difference, but coating with 0.5 MFC differed from others (P = 0.00). At 16 and 48 hours, PMMA coated with 1 MFC and 2 MFC by APS and SB&APS methods inhibited C.albicans. COS can be coated onto PMMA using APS and can inhibit C.albicans. With further development, this method could be applied to treat denture stomatitis alternatively to conventional antifungal drugs. Keywords: Candida albicans, Chitosan, Oligochitosan, Polymethylmethacrylate, Silanes

The effect of hydrofluoric acid treatment on the repair strength of polyamide denture base materials: An in vitro study.

Although polymethylmethacrylate (PMMA) dentures can be repaired using autopolymerizing acrylic resin, achieving it using polyamides is difficult. This study aimed to achieve acceptable bond strength using autopolymerizing acrylic resin by applying surface treatments to the polyamide denture base material. Thirty-six disc-shaped samples (27 polyamide, 9 PMMA) were prepared. Based on the surface treatment applied, the polyamide samples were divided into three groups: No surface treatment (n=9), tribochemical silica coating+silane coupling agent (n=9), and 9% hydrofluoric acid+tribochemical silica coating+silane coupling agent (n=9). PMMA specimens received no surface treatment. Polyamide and PMMA surfaces had auto-polymerizing acrylic resin bonded on them, and then a shear bond strength test was performed between them after aging. The Kruskal-Wallis test was used, and statistical significance was set at p<0.05. PMMA had the highest shear bond strength, the untreated polyamide group had the lowest shear bond strength, and the difference was significant (p<0.05). The group treated with 9% hydrofluoric acid, tribochemical silica coating, and silane coupling agent exhibited the highest shear bond strength of the polyamide groups, and the bond strength in this group was comparable to the PMMA specimens (p>0.05). The polyamide denture repair strength can be improved by 9% hydrofluoric acid, tribochemical silica coating, and silane coupling agent application to the polyamide surface.

The Effect of Preloaded Compressive Stress and Curvature of Defect on Blast-Induced Fracture Behavior by Caustic and Numerical Models

In this study, the effects of preloaded uniaxial compressive stress and defect (prefabricated by laser cutting) curvature on blast-induced cracks and stress wave propagation were investigated in polymethyl methacrylate (PMMA) specimens using caustics theory. Based on the mathematical relationship between stress and optics, the fracture behavior (the propagation path, dynamic stress intensity factors (DSIFs), propagation velocity, initiation angle of the main crack, and damage degree between the defect and the blasthole) was calculated and analyzed quantitatively. The results show that the preloaded stress could mainly restrain the main crack propagation in the horizontal direction and reduce the initiation angle and damage degree at the defects. Meanwhile, the crack initiation position of the positive curvature defect was not at the end of the defect. In addition, the curvature of the defect significantly affected the blast-induced fracture compared to preloaded stresses. Comparing the main crack with other curvature defects, the DSIFs, velocity, crack arrest time, crack length, and horizontal offset distance of the main crack with negative curvature defect were the largest. The variation in the full stress field in the specimen under blasting and preloaded stress was simulated by a numerical model. The results show that the curvature of the defect has a significant effect on tensile waves at the end of defects, and the tensile stress from high to low was C-25, C0, and C25, in that order.

The influence of lemongrass essential oil addition into heat cured acrylic resin against Candida albicans adhesion

Background: For decades, the use of naturally accessible materials in treating human disease has been widespread. The goal of this study was to determine the anti-fungal effectiveness /of the lemongrass essential oil (LGEO) versus Candida albicans (C. albicans) adhesion to polymethylmethacrylate (PMMA) materials. Material and methods: LGEO's anti-fungal activity was tested against C. albicans adhesion using the following concentration of LGEO in PMMA monomer (2.5 vol. %, 5 vol. % LGEO) selected from the pilot study as the best two effective concentrations. A total of 40 specimens were fabricated for the candida adherence test and were subdivided into four equal groups: negative control 0 vol. % addition, experimental with 2.5 vol. % and 5 vol. % of LGEO addition and positive control with 1.4 wt. % nystatin addition. The sterile PMMA specimens were incubated at room temperature for 1 hr in sterile tubes with a sabouraud dextrose broth (SDA) in which a small amount of the yeast was isolated and suspended; under the inverted light microscope, the examination was done. The data were evaluated using a one-way ANOVA test, which showed a significant result at p&lt; 0.05. Results: The findings of the C. albicans adherence test exposed a considerable reduction in the number of C. albicans cells adhering to PMMA after adding 2.5 vol. % and 5 vol. % LGEO compared to specimens from the negative control and positive control groups at p&lt; 0.05. Conclusion: Adding LGEO into a heat-cure acrylic material can result in a denture base material with anti-fungal properties versus C. albicans microorganisms. The experimental group 5 vol. % LGEO additive showed the best anti-fungal activity

Antibiofilm properties of silver nanoparticles incorporated into polymethyl methacrylate used for dental applications.

Acrylic resins used in dental and biomedical applications do not have antimicrobial properties, their surface is susceptible to colonization of microorganisms. The aim of this study was to evaluate the antibiofilm properties of silver nanoparticles (AgNPs) deposited in a polymethyl methacrylate (PMMA) surface against a Staphylococcus aureus biofilm. The PMMA was impregnated with AgNPs by using the in-situ polymerization method. To determine the solubility of the incorporated silver (Ag+) atomic absorption spectrophotometry was used (AAS) at 24 h, 48 h, 7 days, and 30 days. Thirty specimens of PMMA with AgNPs and without NP (control group) were assembled in the CDC Biofilm Bioreactor system with a cell suspension of S. aureus. The specimens were removed at 6, 12, 24, 48, and 72 h to determine the viability profile and quantify the Arbitrary Fluorescence Units (AFU). The AgNPs showed an irregular and quasispherical shape with an average size of 25 nm. AAS analysis demonstrated a low solubility of Ag+. The formation of the S. aureus biofilm increased as the evaluation periods continued up to 72 h. The experimental group showed poor growth, and a decrease in the intensity of the fluorescence demonstrated a statistically significant inhibition of the formation of the biofilm (P < 0.05) in relation to the control group at 6, 12, 24, 48, and 72 h. AgNPs incorporated into PMMA decreased the growth and maturation of S. aureus biofilm.

Effect of titanium oxide nanoparticles on polymerization reaction of heat and microwave cured polymethylmethacrylate: in vitro study

BackgroundTitanium Oxide Nanoparticles (TiO2NPs) have been introduced to polymethyl methacrylate (PMMA) denture base to enhance its mechanical, physical, and biological performance.ObjectivesThis research aimed to assess the effect of adding TiO2NPs on the degree of polymerization and morphological characterization of heat and microwave cured PMMA.Materials and methodsFabrication of PMMA specimens which were categorized according to the curing technique into heat cured (group I) and microwave cured (group II). Each group was subdivided into two subgroups A and B according to the addition of TiO2NPs. A total number of 24 specimens were fabricated. Each subgroup contains 6 specimens. The specimens were characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis (EDX). The polymerization reaction of specimens was assessed by Attenuated Total Reflection Fourier-Transform Infra-Red Spectroscopy (ATR-FTIR). Results were statistically analyzed using an independent T-test and one-way ANOVA. The significance level was set at p < 0.05.ResultsSEM/EDX revealed that TiO2 NPs appeared as bright areas in the matrix of both groups. The matrix showed organic impurities and minute internal cracks, but group IIB (microwave-cured PMMA with TiO2NPs) showed higher organic impurities than heat-cured PMMA. The FTIR revealed that the addition of 3% by weight TiO2NPs decreased the degree of polymerization of both heat and microwave-cured PMMA but the decrease was insignificant (p > 0.05).ConclusionsIncorporation of 3% by weight TiO2NPs does not significantly affect the degree of polymerization of both heat and microwave-cured PMMA. Hence, denture materials can benefit from the advantages of the TiO2NPs without any alterations to their structures.Graphical abstract

Using Peek as a Framework Material for Maxillofacial Silicone Prosthesis: An In Vitro Study.

There are often bonding problems between acrylic resins and silicone. PEEK (polyetheretherketone), which is a high-performance polymer, has great potential for the implant, and fixed or removable prosthodontics. The aim of this study was to evaluate the effect of different surface treatments on PEEK to be bonded to maxillofacial silicone elastomers. A total of 48 specimens were fabricated from either PEEK or PMMA (Polymethylmethacrylate) (n = 8). PMMA specimens acted as a positive control group. PEEK specimens were divided into five study groups as surface treatments as control PEEK, silica-coating, plasma etching, grinding, or nano-second fiber laser. Surface topographies were evaluated by scanning electron microscopy (SEM). A platinum-primer was used on top of all specimens including control groups prior to silicone polymerization. The peel bond strength of the specimens to a platinum-type silicone elastomer was tested at a cross-head speed of 5 mm/min. The data were statistically analyzed (α = 0.05). The control PEEK group showed the highest bond strength (p < 0.05) among the groups. No statistical difference was found between control PEEK, grinding, or plasma etching groups (p > 0.05). The lowest bond strength was seen in the laser group, which was not statistically different from silica-coating (p > 0.05), and statistically different from control PEEK, grinding, or plasma groups (p < 0.05). Positive control PMMA specimens had statistically lower bond strength than either control PEEK or plasma etching groups (p < 0.05). All specimens exhibited adhesive failure after a peel test. The study results indicate that PEEK could serve as a potential alternative substructure for implant-retained silicone prostheses.

Comparative Evaluation of Flexural and Impact Strength of Denture Base Acrylic Resin using Different Processing Methods - An in-vitro Study

Background: One of the chief limitations of Polymethylmethacrylate denture base material is its inadequate mechanical property. Different processing methods of Polymethylmethacrylate have varying influences on the mechanical properties of denture base material. Aim: The aim of our in-vitro study was to comparatively evaluate the flexural and impact strength values between CAD-CAM, Compression-molded and Injection- molded Polymethylmethacrylate specimens. Materials and methods: A total of 66 acrylic rectangular specimens of ISO Standardization (64 x10 x3.3mm) were fabricated. This study was conducted between three groups: Group I (n=22)-CAD-CAM Milled specimens (Ruthinium, India), Group II (n=22)- Compression-molded specimens (Dental Products of India, Chennai), Group III (n=22)- Injection-molded specimens (SR- Ivocap High Impact, Ivoclar Vivadent). Flexural strength was evaluated using four-point bend test and Impact strength by IZOD Impact tester. Kruskal Wallis unpaired test was used to compare the mean values between groups and Mann Whitney U test was used to carry out pair wise comparison. Results: Flexural strength of CAD-CAM samples were found to be statistically highest followed by injection molded specimens. Conversely, Impact strength of injection- molded specimens were highest followed by CAD-CAM specimens. Flexural as well as impact strength values were found to be least among compression-molded specimens. Conclusion: CAD-CAM specimens exhibited higher flexural strength whereas Injection-molded specimens had the highest impact strength.

Mechanical properties of CAD/CAM polylactic acid as a material for interim restoration

Statement of problemBiomaterials, including polymethyl methacrylate (PMMA) and bisacrylate, have been widely used as conventional interim materials and may exhibit cytotoxicity or systemic toxicity. PurposeThis study was designed to compare the mechanical properties of polylactic acid (PLA) as an alternative to conventional dental polymers for computer-aided design and manufacturing (CAD/CAM). Material and methodsFour groups (n = 20 per group) of CAD/CAM polymers were assessed. Specimens of PLA (PLA Mill) and PMMA (PMMA Mill) for subtractive manufacturing, PLA for fused deposition modeling (PLA FDM), and bisphenol for additive manufacturing by stereolithography (Bisphenol SLA) were fabricated into 2-mm-wide, 2-mm-thick and 25-mm-long specimens using a milling machine, an FDM printer, and an SLA printer, respectively.The flexural strength (FS) and elastic modulus (EM) were calculated. The surface roughness and Shore D hardness were analyzed with a 3D optical surface roughness analyzer and a Shore durometer, respectively. ResultsPLA Mill showed the lowest FS (64.9 ± 8.28), followed by PLA FDM (104.27 ± 4.42 MPa), PMMA Mill (139.2 ± 20.95 MPa), and Bisphenol SLA (171.56 ± 15.38 MPa), with statistically significant differences. PLA FDM showed the highest EM, followed by PLA Mill, Bisphenol SLA, and PMMA Mill. Significant differences were observed not only between PMMA Mill and Bisphenol SLA but also between PLA FDM and PLA Mill. The lowest Shore D hardness was observed for PLA FDM, followed by PLA Mill, PMMA Mill, and Bisphenol SLA, which showed the highest value among the 4 groups, with significance. The highest values for the surface roughness parameters were observed for PLA Mill, and the lowest were observed for Bisphenol SLA. ConclusionsAmong the tested CAD/CAM polymers, Bisphenol SLA was the most durable material, and the mechanical properties of PLA FDM were within the clinically acceptable range.

Experiments and discrete element simulations of crack initiation angle of mixed-mode I/II in PMMA material

Complex crack configuration causing mixed-mode I/II usually occurs in various situations in engineering, and it is difficult to accurately predict the direction of crack initiation by theory. In fact, there is a great difference between the finite-plate theoretical prediction and the experimental results. To investigate the effects of crack configuration on crack initiation angle, new brittle polymethyl methacrylate (PMMA) specimens were designed. Multiple sets of fracture experiments of mixed-mode I/II were performed systematically to obtain the crack initiation angle of PMMA specimens. The variation of the crack initiation angle with the size ratio was obtained experimentally, which indicated that the crack initiation angle increases with the increase of the size ratio. As a supplement to the physical experiments, corresponding numerical simulations were carried out based on the Discrete Element Method. Firstly, the material parameters of the numerical simulation were calibrated by reproducing the failure process of the sample in the experiment. Then, the numerical modeling and calculation were carried out for the samples that are inconvenient to process in the experiment. Combining the results of both experiment and numerical simulation, a prediction formula for the crack initiation angle was obtained. Furthermore, the effects of symmetry factor and preexisting crack length on the tensile capacity and the crack initiation angle were investigated by simulation systematically. By adjusting the crack configuration parameters, the direction of crack initiation can be artificially controlled, which is of great importance for ensuring engineering safety.

Rapid Prototyping of Multi-Functional and Biocompatible Parafilm®-Based Microfluidic Devices by Laser Ablation and Thermal Bonding.

In this paper, we report a simple, rapid, low-cost, biocompatible, and detachable microfluidic chip fabrication method for customized designs based on Parafilm®. Here, Parafilm® works as both a bonding agent and a functional membrane. Its high ultimate tensile stress (3.94 MPa) allows the demonstration of high-performance actuators such as microvalves and micropumps. By laser ablation and the one-step bonding of multiple layers, 3D structured microfluidic chips were successfully fabricated within 2 h. The consumption time of this method (~2 h) was 12 times less than conventional photolithography (~24 h). Moreover, the shear stress of the PMMA-Parafilm®-PMMA specimens (0.24 MPa) was 2.13 times higher than that of the PDMS-PDMS specimens (0.08 MPa), and 0.56 times higher than that of the PDMS-Glass specimens (0.16 MPa), showing better stability and reliability. In this method, multiple easily accessible materials such as polymethylmethacrylate (PMMA), PVC, and glass slides were demonstrated and well-incorporated as our substrates. Practical actuation devices that required high bonding strength including microvalves and micropumps were fabricated by this method with high performance. Moreover, the biocompatibility of the Parafilm®-based microfluidic devices was validated through a seven-day E. coli cultivation. This reported fabrication scheme will provide a versatile platform for biochemical applications and point-of-care diagnostics.

Comparing different data processing methods for determining a Prony series from Dynamic Mechanical Analyzer frequency data

AbstractThis study focuses on using a dynamic mechanical analyzer (DMA) for obtaining frequency domain data suitable for constructing an accurate Prony series for a viscoelastic material. Polymethyl methacrylate (PMMA) specimens were used in each experiment, following the ASTM D4000 and ASTM D5023 standards. The experiments were completed using a frequency range of 1 to 100 Hz at multiple temperatures to capture the long‐term behavior via time–temperature superposition. Prony series were fit to the data from these experiments, and used to establish the time domain viscoelastic modulus of PMMA. The effect of the fitting function, material soak time, noise, and reference temperature selection were each investigated for their effect on the Prony series. The raw data may be processed via four paths, which are then compared for statistical error. The most accurate path resulted in a cumulative error of 2.1% for the storage modulus and 26% for the loss modulus. The impact of these errors on the tip displacement of a reference cantilever beam subject to axial loading for 15 years is a variation of over 25%.

Effect of alkynyloxy derivatives of lawsone as an antifungal spray for acrylic denture base: An in vitro study

ObjectiveThe purpose of this study was to (i) synthesize and develop an alkynyloxy derivative of lawsone as an antifungal spray and (ii) assess the antifungal spray’s effectiveness in reducing the viability of Candida albicans (C. albicans) on polymethylmethacrylate (PMMA) specimens. MethodsLawsone methyl ether (LME) and its derivative, 2-(prop-2-ynyloxy)naphthalene-1,4-dione (compound 1) were synthesized and characterized. The synthetic compounds were screened for antimicrobial activities against C. albicans using the microtiter broth dilution method to determine the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). Compound 1 was further formulated as an antifungal spray in three concentrations (100, 200, and 400 μg/mL). C. albicans biofilms were developed for 48 h on PMMA specimens. The efficacy of using an antifungal spray for 1 and 3 min to remove biofilm was assessed using colony counting and scanning electron microscopy (SEM). Chlorhexidine gluconate (CHX), polident®, and distilled water were used as positive and negative control cleansing solutions, respectively. ResultsLME and compound 1 showed comparable inhibition against C. albicans with a MIC of 25 μg/mL and MFC of 50 μg/mL. For immediate treatment, C. albicans was not detected on PMMA specimens when expose to 2% CHX and compound 1 (100, 200, and 400 μg/mL) antifungal spray for 3 min. However, after recolonization, a small number of viable cells were observed in denture soaked in compound 1 antifungal spray for 3 min group. Following recolonization, polident® and distilled water had comparable viable cell counts of C. albicans to the no treatment group. Scanning electron microscope (SEM) images revealed that CHX, polident®, and compound 1 caused cell damage in various forms. ConclusionDenture spray containing synthetic alkynyloxy derivative of lawsone is a promising antifungal agent for C. albicans biofilm removal from the PMMA surface.

Effect of polishing methods on the surface roughness of different temporary restorative materials

Aim: The purpose of this study was to evaluate the effects of different polishing methods on the surface roughness of temporary prosthetic restorations. Methodology: In this study, 200 specimens were obtained from Structur 2, Imident, FSM Duo CAD, and Han Temp Crown. All specimens were sanded with 400-, 800-, and 1000-grit silicon carbide. Next, the specimens were divided into five subgroups (n = 10). The specimens in first group were sanded with 1200-, 1600-, and 2000-grit silicon carbide sandpaper. The second group was polished with an aluminum oxide-containing disc. The third group was polished with a diamond-containing pad. A glaze bond was applied to the specimens in the fourth group. The fifth group was glazed with a coat of nano-filled resin. Then, the surface roughness of all specimens was measured with a profilometer. A two-way ANOVA test was performed using SPSS 20.0. Finally, the microstructures of the surfaces were examined by a scanning electron microscope at 5000× magnification. Results: Statistically significant results were obtained between the temporary materials and polishing methods in terms of surface roughness (p &lt; 0.05). For the polishing method, the highest surface roughness values were observed in the control group (0.50 ± 0.15). The lowest surface roughness values were observed in the Equia Forte GC coat group (0.25 ± 0.10). Among the temporary crown materials, the highest roughness was observed in Imicryl specimens. (0.45 ± 0.17), while the least roughness was the polymethyl-methacrylate (PMMA) specimens (0.17 ± 0.10). Conclusion: Surface polishing and finishing procedures might positively affect the surface roughness of temporary materials. Furthermore, materials made via computer-aided design and computer-aided manufacturing (CAD-CAM) demonstrate structural advantages and may be preferable. How to cite this article: How to cite this article: Kavut İ, Uğur M, Tanrıkut ÖO. Effect of polishing methods on the surface roughness of different temporary restorative materials. Int Dent Res 2022;12(3):149-57. https://doi.org/10.5577/intdentres.2022.vol12.no3.7 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Effect of Nano Ceramic Coating on Color Perceptibility and Acceptability of Polymethylmethacrylate: In Vitro and Clinical Study.

The effect of a novel nano-ceramic coating (TiO2) using an atomic layer deposition (ALD) technique on the surface of polymethyl methacrylate (PMMA) material was investigated. The patients' and clinicians' perception and acceptance of the PMMA color with TiO2 coating were also examined. In vitro color measurement was performed on thirty specimens (light, original, and dark pink) before and after TiO2 coating. Patients' and clinicians' perception and acceptance of color changes on PMMA were measured and compared. Descriptive and analytic statistics were analyzed (a = 0.05). TiO2 films were successfully deposited on the PMMA specimen by the ALD technique. Color changes after TiO2 coating were observed on all three PMMA shades, significantly higher than the established 50:50% perceptibility threshold, but below the established 50:50% acceptability threshold. The percentage of patients that perceived a color difference after TiO2 coating were 83.3%, 63.9%, and 77.8% for light, original, and dark pink, respectively. The percentages of clinicians that were satisfied with the color difference were 96.4%, 80%, and 69.2% for light, original, and dark pink, respectively. Color changes after TiO2 coating were observed, but below the acceptable threshold. The clinical survey demonstrated that a color difference was perceived but was clinically acceptable. In general, laypeople have lower perception and higher acceptance of changes in PMMA color than clinicians.