Effect of SiO2 Nanoparticles Addition on the Flexural Strength of Repaired Acrylic Denture Base

Effect of Different Surface Treatments as Methods of Improving the Mechanical Properties after Repairs of PMMA for Dentures

Denture fractures are a common problem in dental practice, and their repair is considered a first option to restore their functional properties. However, the inter-material resistance may become compromised. Typically, the bond between these materials weakens. Therefore, various surface treatment methods may be considered to enhance their mechanical properties. Poly(methyl methacrylate) (PMMA) heat-polymerized resin (HPR) was used as the repaired material, cold-polymerized material (CPR) for the repairs, and different variants of alumina abrasive blasting (AB), methyl methacrylate (M), ethyl acetate (EA), methylene chloride (CH), and isopropyl alcohol (IA) treatments were applied. Finally, combined surface treatments were chosen and analyzed. Surface morphologies after treatments were observed by scanning electron microscopy and the flexural, shear, and impact strengths were tested. AB and chemical treatment with CH, M, and EA was used to improve all mechanical properties, and further improvement of the properties could be achieved by combining both types of treatments. Varied changes in surface morphologies were observed. Treatment with IA yielded less favorable results due to the low impact strength. The best results were achieved for the combination of AB and CH, but during the application of CH it was necessary to strictly control the exposure time.

Composite Nanomaterials Based on Polymethylmethacrylate Doped with Carbon Nanotubes and Nanoparticles: A Review

Composite polymer materials have high strength and lightness, which makes them attractive for use in a variety of structures and products. The present article contains an overview of modern works devoted to the production of composite materials based on poly(methyl methacrylate) (PMMA) with improved characteristics. The possibility of obtaining such materials can be a key area for creating more efficient and durable products in various industries. Various methods were considered to improve the characteristics of PMMA by doping the polymer matrix with carbon nanotubes (CNTs), graphite, nanohydroxyapatite particles, micro-zirconia nanoparticles, titanium dioxide, etc. The possibilities of using the obtained composite materials in various industries such as aviation, automotive, construction, medical and others are discussed. This article also presents the results of our own research on the mechanisms of interaction of PMMA with single-layer CNTs, leading to the creation of a composite polymer system "PMMA+CNT", achieved using the modern quantum chemical method DFT. This article presents a review of the recent research on the effect of CNTs on the mechanical and electrically conductive properties of nanocomposite materials. The outcomes of this study can be important for the development of science and technology in various fields, from fundamental chemistry to applied scientific research.

Evaluation and Comparison of Mechanical Properties of Heat Polymerized Acrylic Resin After Reinforcement of Different Fibers in Different Patterns: An In Vitro Study

INTRODUCTION

Most denture fractures occur within the mouth due to resin flexural fatigue. For example, the deep labial notch at the high labial frenum causes denture breakage, as can deep scratches and generated processing stresses. The rising cost of annual prosthetic repairs is evidence that the problem of total denture fracture has not been solved. The purpose of this investigation was to evaluate the relative improvement in flexural strength between heat-cured polymethyl methacrylate (PMMA) resin reinforced with glass fibers (GF) and basalt fibers (BF) of varied orientations.

MATERIAL AND METHODS

A total of 150 heat-cured acrylic resin specimens of 65x10x3 mm dimension were prepared, 30 of which were left unreinforced (Group A), 30 of which were reinforced with GF in transverse pattern (Group B), 30 of which were reinforced with GF in meshwork pattern (Group C), 30 of which were reinforced with BF in transverse pattern (Group D), and 30 of which were reinforced with BF in meshwork pattern (Group E). All of the samples were put through flexural strength testing on the universal testing machine. One-way ANOVA and the Tukey-Kramer various correlation test (= 0.05) were used in SPSS for Windows to look at the facts.

RESULTS

The mean flexural strength for Group A was 46.26±2.26 MPa, 64.98±1.53 MPa for Group B, 76.45±2.67 MPa for Group C, 54.22±2.24 MPa for Group D, and 59.02±2.38 MPa for Group E. Flexural strength was impacted by both the kind of BF and GF reinforcement (F = 768.316, P = 0.001).

CONCLUSION

Within the limitation of the current research, BF reinforcement outperforms GF reinforcement and unreinforced heat-cured acrylic resin in terms of flexural strength.

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

PURPOSE

To evaluate the flexural strength (FS), impact strength (IS), surface roughness (Ra), and hardness of 3D-printed resin incorporating silicon dioxide nanoparticles (SNPs).

MATERIALS AND METHODS

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).

RESULTS

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).

CONCLUSION

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.

The Mechanical and Antibacterial Properties of Boron Nitride/Silver Nanocomposite Enhanced Polymethyl Methacrylate Resin for Application in Oral Denture Bases

The introduction of nanomaterials into polymethyl methacrylate (PMMA) resin has been effective for mechanically reinforcing PMMA for application in oral denture bases. However, these methods cannot simultaneously improve the mechanical and antibacterial properties, which limits widespread clinical application. Here, we self-assembled binary nanocomposites of boron nitride nanosheets (h-BNNs) and silver nanoparticles (AgNPs) as nanofillers and incorporated the nanofillers into PMMA. The aim of this study was to achieve antibacterial effects while significantly improving the mechanical properties of PMMA and provide a theoretical basis for further clinical application. We employed scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), Ultraviolet visible spectrum (UV) and atomic force microscopy (AFM) to investigate the microscopic morphology and composition of PMMA containing nanocomposites with different mass fraction. In addition, the content of the h-BNNs/AgNPs was 1 wt%, and the compressive strength and flexural strength of pure PMMA were improved by 53.5% and 56.7%, respectively. When the concentration of the nanocomposite in the PMMA resin was 1.4 wt%, the antibacterial rate was 92.1%. Overall, synergistically reinforcing PMMA composite resin with a multi-dimensional nanocomposite structure provided a new perspective for expanding not only the application of resins in clinical settings but also the research and development of new composite resins.

PMMA-Based Nanocomposites for Odontology Applications: A State-of-the-Art

Polymethyl methacrylate (PMMA), a well-known polymer of the methacrylate family, is extensively used in biomedicine, particularly in odontological applications including artificial teeth, dentures and denture bases, obturators, provisional or permanent crowns, and so forth. The exceptional PMMA properties, including aesthetics, inexpensiveness, simple manipulation, low density, and adjustable mechanical properties, make it a perfect candidate in the field of dentistry. However, it presents some deficiencies, including weakness regarding hydrolytic degradation, poor fracture toughness, and a lack of antibacterial activity. To further enhance its properties and solve these drawbacks, different approaches can be performed, including the incorporation of nanofillers. In this regard, different types of metallic nanoparticles, metal oxide nanofillers, and carbon-based nanomaterials have been recently integrated into PMMA matrices with the aim to reduce water absorption and improve their performance, namely their thermal and flexural properties. In this review, recent studies regarding the development of PMMA-based nanocomposites for odontology applications are summarized and future perspectives are highlighted.

Comparative Effect of Incorporation of ZrO2, TiO2, and SiO2 Nanoparticles on the Strength and Surface Properties of PMMA Denture Base Material: An In Vitro Study

Objective

This study aimed to investigate the effects of nanoparticles (zirconium dioxide (ZrO₂), titanium dioxide (TiO₂), and silicon dioxide (SiO₂)) on the flexural strength, impact strength, hardness, and wear resistance of the acrylic resin denture base material.

Materials and Methods

Acrylic resin specimens were fabricated in dimensions according to American Dental Association (ADA) specifications per test. Specimens were divided according to nanofiller into four groups; unmodified as control, ZrO₂ (Z), TiO₂, (T), and SiO₂ (S) groups. Each one was subdivided into two subgroups according to nanoparticle concentrations; 3% and 7% (Z3, Z7, T3, T7, S3, and S7). A 3-point bending test, Charpy impact test, and Vickers hardness test were used for flexural strength, impact strength, and hardness measurements, respectively. Wear resistance was measured by the differences in surface roughness of tested specimens before and after the wear test. A scanning electron microscope was used to assess nanoparticle specifications and distributions and for fracture surfaces analysis. ANOVA, Bonferroni's post hoc test, and the Kruskal–Wallis test were applied for data analysis (α = 0.05).

Results

Regarding the flexural and impact strength, there was a statistically remarkable increase for all tested groups compared with the control group, except for the T7 and S7 groups (P value <0.001, effect size = 0.893) and (P value <0.001, effect size = 0.759), respectively. There was a statistically significant improvement in the hardness of all tested groups compared with the control group (P value <0.001, effect size = 0.67) except T3 and S3. Regarding wear, a statistically significant enhancement was noticed in the wear resistance of all tested groups (P value <0.001, effect size = 0.685), except for the T7 and S7 groups.

Conclusion

The flexural strength, impact strength, and wear resistance improved with both concentrations of ZrO₂ and low TiO₂ and SiO₂ concentrations. The hardness increased with both concentrations of ZrO₂ and high TiO₂ and SiO₂ concentrations.

Study on the role of nano antibacterial materials in orthodontics (a review)

Nanoparticles (NPs) are insoluble particles with a diameter of fewer than 100 nanometers. Two main methods have been utilized in orthodontic therapy to avoid microbial adherence or enamel demineralization. Certain NPs are included in orthodontic adhesives or acrylic resins (fluorohydroxyapatite, fluorapatite, hydroxyapatite, SiO2, TiO2, silver, nanofillers), and NPs (i.e., a thin layer of nitrogen-doped TiO2 on the bracket surfaces) are coated on the surfaces of orthodontic equipment. Although using NPs in orthodontics may open up modern facilities, prior research looked at antibacterial or physical characteristics for a limited period of time, ranging from one day to several weeks, and the limits of in vitro studies must be understood. The long-term effectiveness of nanotechnology-based orthodontic materials has not yet been conclusively confirmed and needs further study, as well as potential safety concerns (toxic effects) associated with NP size.

Antifungal Activities and Some Surface Characteristics of Denture Soft Liners Containing Silicon Dioxide Nanoparticles

Objective

This study aimed at determining the influence of adding silicon dioxide nanoparticles (nano-SiO₂) to soft relining materials on C. albicans adhesion, surface roughness, and contact angle.

Materials and Methods

Eighty heat-polymerized acrylic resin disks were constructed and relined by using auto-polymerized acrylic soft liners (COE-SOFT, GC Co., Tokyo, Japan). The specimens were categorized into two groups according to the tests conducted. Group A was composed of 40 specimens for evaluating antifungal activity, and Group B was composed of 40 specimens for testing surface roughness and contact angle. Each group was subcategorized into four subgroups (n = 10) according to the concentration of nano-SiO₂ added to the soft-liner powder: control, 0.25%, 0.5%, and 1.0% by weight. The colony forming unit (CFU) was used to assess C. albicans count. A profilometer was used to measure the surface roughness values (Ra; μm). The sessile drop method was used to evaluate the contact angle (^o) by using a goniometer. Analysis of variance and Tukey's post hoc tests (α = 0.05) were used for the data analysis.

Results

In comparison with the unmodified group, the 0.25% and the 0.5% nano-SiO₂ groups exhibited significantly lower C. albicans counts (P < 0.001), surface roughness (P < 0.001), and contact angles (P < 0.001). The exception was the 1% group, which exhibited higher C. albicans count, surface roughness, and contact angles than lower-concentration nano-SiO₂ groups; however, these values in the 1% group were still less than their respective values in the control group.

Conclusion

The addition of 0.25% and 0.5% nano-SiO₂ to an auto-polymerized acrylic soft liner decreased C. albicans adhesion, surface roughness, and contact angle.

Effect of silicon dioxide nanoparticles on the flexural strength of heat-polymerized acrylic denture base material: A systematic review and meta-analysis

Objective

This study evaluated the influence of silicon dioxide (SiO₂) nanoparticles on the flexural strength of heat-polymerized denture base materials.

Background

Nanoparticles have been incorporated into the denture base materials in different proportions to enhance the mechanical properties. Recently, the incorporation of SiO₂ nanoparticles at low concentrations has shown promising outcomes.

Materials and Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) protocol, this study was designed with the following focused question: “Does the addition of SiO₂ nanoparticles improve the flexural strength of heat-polymerized acrylic resins?” The inclusion criteria included in-vitro studies that assessed the flexural strength of SiO₂ nanoparticle-reinforced heat-polymerized acrylic denture base resins tested according to American Dental Association specifications. The database search involved articles published from 2005 to 2020 on PubMed/MEDLINE, Web of Science, Google Scholar, and Scopus using the following keywords: SiO₂, nanosilica, silica oxide, nanoparticles, denture base resin, acrylic resin, polymethyl methacrylate, PMMA, flexural strength, and mechanical properties.

Results

Among 167 studies, five papers fulfilled the inclusion criteria and were added for the data analysis and meta-analysis. Proportions of incorporated SiO₂ nanoparticles ranged from 0.25% to 15% and the reported flexural strength values for the reinforced acrylic resin ranged from 41.25 MPa to 124.56 MPa. The meta-analysis revealed no significant effect on the flexural strength between the unmodified and the SiO₂ nanoparticle-reinforced acrylic resin.

Conclusion

Therefore, No particular concentration of SiO₂ nanoparticles could be recommended for heat-polymerized denture base reinforcement.

Polymethylmethacrylate Incorporating Nanodiamonds for Denture Repair: In Vitro Study on the Mechanical Properties

OBJECTIVE

 This study aimed to evaluate the effect of nanodiamond (ND) addition to repair resin with repair gap modifications on the flexural and impact strength of repaired polymethylmethacrylate denture base.

MATERIALS AND METHODS

 Heat-polymerized acrylic resin specimens (N = 100/test) were prepared and sectioned to half creating two repair gaps: 2.5- and 0 mm with 45 degrees beveling. They were further divided into subgroups (n = 20) according to ND concentration (control, 0.25%ND, and 0.50%ND), thermocycling (500 cycles) was done to half the specimens in each subgroup. Flexural strength was tested using 3-point bending test and impact strength was tested by Charpy's impact test. Analysis of variance and post-hoc Tukey's tests were performed for data analysis (α = 0.05). Scanning electron microscope was employed for fracture surface analysis and ND distribution.

RESULTS

 Before and after thermocycling, the addition of ND significantly increased the flexural strength and elastic modulus in comparison to control group (p ˂ 0.001), while 0 mm repair gap showed insignificant difference between ND-reinforced groups (p ˃ 0.05). Regarding impact strength, ND addition increased the impact strength with 0 mm gap in comparison to control and 2.5 mm with ND (p˂0.001), while later groups showed no significant in between (p ˃ 0.05). Comparing thermocycling effect per respective concentration and repair gap, thermocycling adversely affected all tested properties except elastic modulus with 0 mm-0.25 and 0 mm-0.5% and impact strength with 2.5 mm, 2.5 mm-0.25%, 2.5 mm- 0.5% (p ˃ 0.05).

CONCLUSION

 ND addition combined with decreased repair gap improved the flexural strength, elastic modulus, and impact strength of repaired denture resin, while thermocycling has a negative effect on denture repair strength.

The impact of nanoparticles-modified repair resin on denture repairs: a systematic review

This study aimed to evaluate the effect of nanoparticles on the mechanical properties of acrylic denture repairs. The review was designed following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines. Database search was conducted involving articles published from 2000 to 2020 using the following keywords: PMMA/nanoparticles, denture repair/nanoparticles, and repair strength/nanoparticles. PubMed/MEDLINE, Embase, Google Scholar, Scopus, and EBSCOhost were used to find only those studies used repair resin reinforced with nanoparticles for denture repairs. Due to variations between nanoparticles types, sizes, and testing properties, the quantitative statistical meta-analysis couldn't be conducted. Therefore, a descriptive data analysis was applied. Out of 379 articles, 8 articles were included; three nanoparticles, zirconium oxide (nano-ZrO2), silicon oxide (nano-SiO2), and aluminum oxide (nano-Al2O3) nanoparticles were used as reinforcements to repair resin. Seven studies investigated the effects of 0.25-7.5 wt.% nano-ZrO2 on the mechanical properties of repaired denture bases and reported positive effects with high concentrations. Two studies study investigated 0.25-0.75 wt% nano-SiO2 and found that low % nano-SiO2 concentrations improved repair strength while, one study showed that 1 and 1.5 wt.% nano-Al2O3 increased the flexural strength. Although nanoparticles offer positive effects on the properties of denture repair, inadequate studies exist. Therefore, further investigations are required. Scientific field of dental Science: Prosthodontics.

Effects of SiO2 Incorporation on the Flexural Properties of a Denture Base Resin: An In Vitro Study

Objective  The aim of this study was to evaluate the effects of the addition of low-silicon dioxide nanoparticles (nano-SiO ₂ ) on the flexural strength and elastic modulus of polymethyl methacrylate (PMMA) denture base material.

Materials and Methods  A total of 50 rectangular acrylic specimens (65 × 10 × 2.5 mm ³ ) were fabricated from heat-polymerized acrylic resin. In accordance with the amount of nano-SiO ₂ , specimens were divided into the following five groups ( n = 10 per group): a control group with no added SiO ₂ , and four test groups modified with 0.05, 0.25, 0.5, and 1.0 wt% nano-SiO ₂ of acrylic powder. Flexural strength and elastic modulus were measured by using a 3-point bending test with a universal testing machine. A scanning electron microscope was used for fracture surface analyses. Data analyses were conducted through analysis of variance and Tukey’s post hoc test (α = 0.05).

Results  Compared with the control group, flexural strength and modulus of elasticity tended to significantly increase ( p ˂ 0.001) with the incorporation of nano-SiO ₂ . In between the reinforced groups, the flexural strength significantly decreased ( p ˂ 0.001) as the concentrations increased from 0.25 to 1.0%, with the 1.0% group showing the lowest value. Furthermore, the elastic modulus significantly increased ( p ˂ 0.001) at 0.05% followed by 1.0%, 0.25%, 0.5%, and least in control group.

Conclusion  A low nano-SiO ₂ addition increased the flexural strength and elastic modulus of a PMMA denture base resin.

Antifungal Efficacy and Physical Properties of Poly(methylmethacrylate) Denture Base Material Reinforced with SiO2 Nanoparticles

PURPOSE

To evaluate the effect of the addition of low concentration of silicon-dioxide nanoparticles (nano-SiO₂ ) to poly(methylmethacrylate) (PMMA) denture base material on Candida albicans adhesion, surface roughness, contact angle, hardness, and translucency.

MATERIALS AND METHODS

A total of 150 acrylic disks were fabricated from heat-polymerized acrylic resin and specimens were divided into 3 groups of 50 per test. They were further subdivided into 5 subgroups (n = 10) according to the concentration of nano-SiO₂ : control (no addition) and four tested groups modified with 0.05, 0.25, 0.5, and 1.0 wt% nano-SiO₂ of acrylic powder. Slide count and direct culture methods were used to measure C. albicans count (CFU/mL). The surface roughness values (R_a ; μm) were determined using a profilometer. The contact angle (^o ) measurement was performed by a goniometer using the sessile drop method. Vickers hardness was used to analyze surface hardness. Translucency was measured using a spectrophotometer. Data analysis was conducted through analysis of variance and Tukey's post hoc tests (α = 0.05).

RESULTS

Compared to the control group, direct culture and slide count methods illustrated a significant decrease in C. albicans count (p ˂ 0.001) with the addition of nano-SiO₂ , and this decrease was correlated with the concentration of nano-SiO₂ . The addition of nano-SiO₂ significantly decreased the contact angle (p ˂ 0.001), whereas hardness and surface roughness significantly increased (p ˂ 0.001). The addition of nano-SiO₂ significantly decreased translucency (p ˂ 0.001), and this decrease was concentration dependent.

CONCLUSION

Addition of low concentration of nano-SiO₂ decreased C. albicans adhesion to PMMA denture base resin. Also, low additions of nano-SiO₂ have positive effects on contact angle and hardness, whereas surface roughness and translucency were adversely affected at high concentrations.

Prosthodontic Applications of Polymethyl Methacrylate (PMMA): An Update

A wide range of polymers are commonly used for various applications in prosthodontics. Polymethyl methacrylate (PMMA) is commonly used for prosthetic dental applications, including the fabrication of artificial teeth, denture bases, dentures, obturators, orthodontic retainers, temporary or provisional crowns, and for the repair of dental prostheses. Additional dental applications of PMMA include occlusal splints, printed or milled casts, dies for treatment planning, and the embedding of tooth specimens for research purposes. The unique properties of PMMA, such as its low density, aesthetics, cost-effectiveness, ease of manipulation, and tailorable physical and mechanical properties, make it a suitable and popular biomaterial for these dental applications. To further improve the properties (thermal properties, water sorption, solubility, impact strength, flexural strength) of PMMA, several chemical modifications and mechanical reinforcement techniques using various types of fibers, nanoparticles, and nanotubes have been reported recently. The present article comprehensively reviews various aspects and properties of PMMA biomaterials, mainly for prosthodontic applications. In addition, recent updates and modifications to enhance the physical and mechanical properties of PMMA are also discussed.

Effect of Incorporation of Silver Nanoparticles on the Tensile Bond Strength of a Long term Soft Denture Liner

OBJECTIVES

 This study aimed at assessing the effect of the addition of silver nanoparticles (SNPs) to a silicone soft liner on its tensile bond strength to denture base resin.

MATERIALS AND METHODS

 SNPs were added to Mucopren cold cure soft liner in 0 (control), 0.5, 1, 2, and 3 wt% concentrations and bonded in 120 stainless steel molds with processed heat cure acrylic resin blocks. Liner/resin combination samples were divided into two groups. The first half was stored for 2 days in distilled water at 37°C and then subjected to tensile bond strength, while the other half were thermocycled 3000 times before testing. Mean bond strength, expressed in mega pascals (MPa), was determined in the tensile test with the use of a universal testing machine at a crosshead speed of 5 mm/min.

STATISTICAL ANALYSIS

 Data were analyzed using SPSS via one-way analysis of variance test, t-test, and Tukey's posthoc, at a 95% confidence level (p < 0.05).

RESULTS

 Addition of SNPs and thermocycling both caused a significant reduction in the tensile bond strength of Mucopren to acrylic resin; however, in the thermocycled group, the bond strength increased with the increase in the concentration of SNPs (p < 0.001).

CONCLUSION

 Addition of SNPs to Mucopren soft silicone liner reduces its tensile bond strength to denture acrylic resin.