The Reinforcement Effect of Nano-Zirconia on the Transverse Strength of Repaired Acrylic Denture Base

Impact of Nanoparticle Addition on the Surface and Color Properties of Three-Dimensional (3D) Printed Polymer-Based Provisional Restorations

This study aimed to evaluate and compare the impact of additives such as ZrO2 and SiO2 nanoparticles (ZrO2NP or SiO2NP) on the hardness, surface roughness, and color stability of 3D printed provisional restorations. Two hundred samples in total were printed using 3D printed resins (ASIGA, and NextDent). Each resin was modified with ZrO2NPs or SiO2NPs in two different concentrations (0.5 wt% and 1 wt%), while one group was kept unmodified (n = 10). Disc-shaped (15 × 2.5 mm) samples were designed and printed in accordance with the manufacturer's recommendation. Printed discs were evaluated for color changes through parameters CIELAB 2000 system (ΔE00), hardness using Vickers hardness test, and surface roughness (Ra) using a noncontact profilometer. After calculating the means and standard deviations, a three-way ANOVA and Tukey post hoc test were performed at α = 0.05. The addition of ZrO2NPs or SiO2NPs to ASIGA and NextDent resins significantly increased the hardness at a given level of concentration (0.5% or 1%) in comparison with pure (p < 0.001), with no significant difference between the two modified groups per resin type (p > 0.05). The highest hardness value was detected in 1% ZrO2NPs with 29.67 ± 2.3. The addition of ZrO2NPs or SiO2NPs had no effect on the Ra (p > 0.05), with 1% ZrO2NPs showing the highest value 0.36 ± 0.04 µm with NextDent resin. ZrO2NPs induced higher color changes (∆E00), ranging from 4.1 to 5.8, while SiO2NPs showed lower values, ranging from 1.01 to 1.85, and the highest mean ∆E00 was observed in the 1% ZrO2NPs group and NextDent resin. The incorporation of ZrO2NPs and SiO2NPs in 3D printed provisional resins increased the hardness without affecting the surface roughness. The optical parameters were significantly affected by ZrO2NPs and less adversely affected by SiO2NPs. Consequently, care must be taken to choose a concentration that will improve the materials' mechanical performance without detracting from their esthetic value.

Influence of inorganic nanoparticles on dental materials' mechanical properties. A narrative review

Inorganic nanoparticles have been widely incorporated in conventional dental materials to help in improving their properties. The literature has shown that incorporating nanoparticles in dental materials in different specialties could have a positive effect on reinforcing the mechanical properties of those materials; however, there was no consensus on the effectiveness of using nanoparticles in enhancing the mechanical properties of dental materials, due to the variety of the properties of nanoparticles itself and their effect on the mechanical properties. This article attempted to analytically review all the studies that assessed the effect of different types of inorganic nanoparticles on the most commonly used dental materials in dental specialties such as polymethyl methacrylate, glass ionomer cement, resin composite, resin adhesive, orthodontic adhesive, and endodontic sealer. The results had shown that those inorganic nanoparticles demonstrated positive potential in improving those mechanical properties in most of the dental materials studied. That potential was attributed to the ultra-small sizes and unique physical and chemical qualities that those inorganic nanoparticles possess, together with the significant surface area to volume ratio. It was concluded from this comprehensive analysis that while a definitive recommendation cannot be provided due to the variety of nanoparticle types, shapes, and incorporated dental material, the consensus suggests using nanoparticles in low concentrations less than 1% by weight along with a silane coupling agent to minimize agglomeration issues and benefit from their properties.

Nanotechnology Innovations Transforming Oral Health Care and Dentistry: A Review

Nanotechnology has revolutionized dentistry by transforming how oral health care is conceptualized, delivered, and maintained. Harnessing nanomaterials and advanced clinical instruments has opened new avenues for precision and innovation across various aspects of dental care. Nanotechnology offers the potential for precise pain management, tooth restoration, and alleviating dental hypersensitivity. Nanomaterials can occlude exposed dentinal tubules, enhancing patient comfort and overall oral well-being. Orthodontic therapy is also revolutionized by nanomaterials with shape memory properties, enabling rapid and more efficient tooth movement. The development of groundbreaking products and therapeutic alternatives is supported by ongoing research efforts, enabling the formation of dental implants, fillings, and prosthetic devices that closely mimic natural tooth characteristics. Nano-delivery systems are being devised for precise drug delivery within the oral cavity, ensuring optimal therapeutic outcomes with minimal side effects. The integration of nanotechnology in dentistry represents a groundbreaking evolution beyond the conventional boundaries of oral health care, enabling the development of innovative diagnostic techniques and improved oral well-being.

Advances of plant and biomass extracted zirconium nanoparticles in dental implant application

Nanoparticles are minimal materials with unique physicochemical features that set them apart from bulk materials of the same composition. These properties make nanoparticles highly desirable for use in commercial and medical research. The primary intention for the development of nanotechnology is to achieve overarching social objectives like bettering our understanding of nature, boosting productivity, improving healthcare, and extending the bounds of sustainable development and human potential. Keeping this as a motivation, Zirconia nanoparticles are becoming the preferred nanostructure for modern biomedical applications. This nanotechnology is exceptionally versatile and has several potential uses in dental research. This review paper concentrated on the various benefits of zirconium nanoparticles in dentistry and how they provide superior strength and flexibility compared to their counterparts. Moreover, the popularity of zirconium nanoparticles is also growing as it has strong biocompatibility potency. Zirconium nanoparticles can be used to develop or address the major difficulty in dentistry. Therefore, this review paper aims to provide a summary of the fundamental research and applications of zirconium nanoparticles in dental implants.

Advanced materials and technologies for oral diseases

Oral disease, as a class of diseases with very high morbidity, brings great physical and mental damage to people worldwide. The increasing burden and strain on individuals and society make oral diseases an urgent global health problem. Since the treatment of almost all oral diseases relies on materials, the rapid development of advanced materials and technologies has also promoted innovations in the treatment methods and strategies of oral diseases. In this review, we systematically summarized the application strategies in advanced materials and technologies for oral diseases according to the etiology of the diseases and the comparison of new and old materials. Finally, the challenges and directions of future development for advanced materials and technologies in the treatment of oral diseases were refined. This review will guide the fundamental research and clinical translation of oral diseases for practitioners of oral medicine.

The Effect of Different levels of a Network Reinforced System and Curing Methods on Properties of Different Acrylic Resin Denture Base Materials

Aims and objective

This study aimed to compare the effect of the addition of light-cured fibre SES mesh at different levels (near the polished surface, at the middle, and near the tissue surface) within different acrylic resin denture base materials on the transverse strength and the surface hardness.

Materials and Methods

One hundred and twenty samples were prepared from three types of acrylic resin denture base materials (high impact heat cured, cross-linked heat cured, and microwaved cured acrylic resins) to test the transverse strength and surface hardness. The samples were divided into four groups: Group1(samples without fibre reinforcement, Control group, n = 30); Group 2 (samples reinforced using SES mesh network near the tissue surface of the acrylic resin sample, n = 30); Group 3 (samples reinforced using SES mesh network near to the polished surface of the acrylic resin sample, n = 30); Group 4 (samples reinforced using SES mesh reinforced network at the middle of the acrylic resin sample, n = 30). The data were statistically analyzed using one-way ANOVA and Tukey's post hoc test at a 0.05 level of significance (SPSS software, version 19.0).

Results

One-way ANOVA showed a significant difference in the mean values of transverse strength between all levels of fibre mesh applications and without fibre mesh reinforcement (P < 0.05). Tukey's post hoc test showed that mesh-reinforced fibre in Group 4 had the highest mean value, while the control group showed the lowest mean value. One-way ANOVA showed a significant difference in the mean surface hardness values between cross-linked heat-cured and microwave-cured acrylic resins (P< 0.05). There was no significant difference in the mean surface hardness values between all levels of fibre mesh applications and without fibre mesh reinforcement for high-impact heat-cured acrylic resin (P ˃ 0.05).

Conclusions

SES-reinforced glass fibre mesh at different levels significantly increased the transverse strength for different acrylic resin materials but had less effect on the surface hardness for all types of acrylic resin materials.

Synthesis and Biomedical Applications of Zirconium Nanoparticles: Advanced Leaps and Bounds in the Recent Past

Many synthetic routes manufacture zirconium nanoparticles in metal oxide, nitride, and other combination forms. Coupled with other variables such as concentration, pH, and form of precursor used, the various synthetic methods support synthesizing the zirconium metal oxide nanoparticles with changed features. Various synthetic methods were studied, such as sol-gel, hydrothermal, laser ablation, and precipitation. All have different synthetic routes, different precursors and solvents were sued, and the product was characterized by SEM, TEM, photo luminance spectroscopy, UV-absorption spectroscopy, and powder X-ray diffraction. X-ray diffraction determined the crystal structure by identifying the crystal shape, arrangement of atoms, and spacing between them. SEM and TEM studied the particle size and morphology of nanoparticles. UV-visible absorption spectroscopy and PL spectroscopy were used for the determination of optical properties of nanoparticles. Zirconium oxide nanoparticles have many applications in the medical field. The review study primarily focuses on the efficient combination of zirconium dioxide with other additive materials and functionalization techniques used to improve the material's properties, assisting the use of the material in hip arthroplasty and bone tissue applications. The development of sophisticated near-infrared (NIR) absorbing small molecules for useful phototheranostic applications was discussed in this paper.

The Effect of Salinized Nano ZrO2 Particles on the Microstructure, Hardness, and Wear Behavior of Acrylic Denture Tooth Nanocomposite

The wear of acrylic denture teeth is a serious problem that can change the vertical dimensions of dentures. This study evaluates the effect of adding salinized nano ZrO₂ particles on the microstructure, hardness, and wear resistance of acrylic denture teeth. Heat polymerizing polymethyl methacrylate resin was mixed with salinized ZrO₂ at concentrations of 5 wt.% and 10 wt.%. Acrylic resin specimens without filler addition were used as a control group. SEM/EDS analyses were performed and the Vickers’ hardness was evaluated. Two-body wear testing was performed using a chewing simulator with a human enamel antagonist. After subjecting the samples to 37,500 cycles, both height loss and weight loss were used to evaluate the wear behavior. The microstructural investigation of the reinforced-denture teeth indicates sound nanocomposite preparation using the applied regime without porosity or macro defects. The addition of zirconium oxide nanofillers to PMMA at both 5% and 10% increased the microhardness, with values of up to 49.7 HV. The wear mechanism in the acrylic base material without nanoparticle addition was found to be fatigue wear; a high density of microcracks were found. The addition of 5 wt.% ZrO₂ improved the wear resistance. Increasing the nanoparticles to 10 wt.% ZrO₂ further improved the wear resistance, with no microcracks found.

Nanoparticles in Prosthetic Materials: A Literature Review

The commonly used prosthodontic materials are resins, ceramics, metals and silicones. A comprehensive review of literature was completed about the incorporation of nanomaterials in prosthetic dentistry using PubMed and Google Scholar databases. This was supplemented with a manual search of selected journals. English language articles in peer- reviewed journals were selected. Current literature reveals that incorporation of nanomaterials has significantly improved the properties of the prosthetic materials within the clinically acceptable ranges. There appears to be a need for a standardization for these in vitro studies carried out to evaluate their physical, mechanical and antimicrobial properties

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.

Impact of ZrO2 nanoparticles addition on flexural properties of denture base resin with different thickness

PURPOSE

This study aimed to evaluate the effect of incorporating zirconium oxide nanoparticles (nano-ZrO₂) in polymethylmethacrylate (PMMA) denture base resin on flexural properties at different material thicknesses.

MATERIALS AND METHODS

Heat polymerized acrylic resin specimens (N = 120) were fabricated and divided into 4 groups according to denture base thickness (2.5 mm, 2.0 mm, 1.5 mm, 1.0 mm). Each group was subdivided into 3 subgroups (n = 10) according to nano-ZrO₂ concentration (0%, 2.5%, and 5%). Flexural strength and elastic modulus were evaluated using a three-point bending test. One-way ANOVA, Tukey's post hoc, and two-way ANOVA were used for data analysis (α = .05). Scanning electron microscopy (SEM) was used for fracture surface analysis and nanoparticles distributions.

RESULTS

Groups with 0% nano-ZrO₂ showed no significant difference in the flexural strength as thickness decreased (P = .153). The addition of nano-zirconia significantly increased the flexural strength (P < .001). The highest value was with 5% nano-ZrO₂ and 2 mm-thickness (125.4 ± 18.3 MPa), followed by 5% nano-ZrO₂ and 1.5 mm-thickness (110.3 ± 8.5 MPa). Moreover, the effect of various concentration levels on elastic modulus was statistically significant for 2 mm thickness (P = .001), but the combined effect of thickness and concentration on elastic modulus was insignificant (P = .10).

CONCLUSION

Reinforcement of denture base material with nano-ZrO₂ significantly increased flexural strength and modulus of elasticity. Reducing material thickness did not decrease flexural strength when nano-ZrO₂ was incorporated. In clinical practice, when low thickness of denture base material is indicated, PMMA/nano-ZrO₂ could be used with minimum acceptable thickness of 1.5 mm.

Core-shell nanoparticles based on zirconia covered with silver as an advantageous perspective for obtaining antimicrobial nanocomposites with good mechanical properties and less cytotoxicity

Antimicrobial nanoparticles perform a vast and promising strand of applications, among which, the silver ones stand out due to their broad antimicrobial spectrum. However, their toxicological potential in addition with their not always satisfying mechanical properties limit their wider application. In this sense, the use of core-shell systems can generate materials with improved properties. Thus, the goal of the present work was to obtain zirconia-silver core-shell nanoparticles and, after that, evaluate their properties in systems based on poly(lactide) PLA. Systems containing silver nanoparticles (AgNP), zirconium oxide (ZrNP), a physical mixture of both particles and core-shell nanoparticles (Core-shell NP) were evaluated. The Core-shell NP were characterized by dynamic light scattering (DLS), Energy Dispersive X-Ray (EDX), transmission electronic microscopy (TEM), and antimicrobial activity. The nanocomposite films were evaluated by Fourier transform infrared analysis (FTIR), thermogravimetric analysis (TGA), nano-hardness, tensile strength test, cytotoxicity, and antimicrobial activity. The results obtained from the DLS and EDX analyses confirmed the obtaining of systems covered with silver. Through the TEM analysis, the formation of the core-shell structure with a diameter of about 100 nm was observed. The films containing core-shell NP presented antimicrobial activity with a profile correspondent to the one observed for AgNP. As for cytotoxicity, these particles proved to be less cytotoxic and achieved higher values of hardness (10%), modulus (40%), and toughness (28%) than those observed for AgNP, and these properties were lower than those observed for ZrNP. The core-shell NP also exhibited even greater antimicrobial activities, less cytotoxicity, and largest elastic modulus (17%) than the physical mixture of the particles.

Antifungal Activity of Denture Base Resin Containing Nanozirconia: In Vitro Assessment of Candida albicans Biofilm

Objective

To evaluate the antimicrobial effects of different concentrations of zirconium dioxide nanoparticles (nano-ZrO₂) reinforcement of poly(methyl) methacrylate (PMMA) on surface roughness and C. albicans biofilm.

Methods

20 heat-polymerized acrylic resin discs were conventionally made and divided into 4 groups (n = 5) according to nano-ZrO₂ concentration: control (0% filler) and 3 experimental groups (2.5% (Z2.5), 5.0% (Z5.0), and 7.5% (Z7.5)). An optical profilometer was used for surface roughness evaluation, followed by Candida adherence assay. Specimens were sterilized, then immersed in cultured yeast (C. albicans), and incubated at 37°C for 48 hours. After that, discs were rinsed before extracting the clustered pellets of Candida. The attached C. albicans was counted using the direct method after spreading on agar media and incubating for 48 hours. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test at α = 0.05.

Results

Surface roughness was significantly increased with all modified groups compared with control (P < 0.01), which showed the lowest roughness value (0.027 ± 0.004 μm). There was no significant difference in the roughness value among reinforced groups (2.5, 5.0, and 7.5%) (P > 0.05), with Z7.5 showing the highest roughness value (0.042 ± 0.004 μm). Candida count was reduced as the nano-ZrO₂ increased but not significantly (P=0.15).

Conclusions

The addition of different concentrations of nano-ZrO₂ particles to PMMA increased the surface roughness compared with control; in contrast, insignificant reduction of C. albicans biofilm was detected.

Nanoparticles in Dentistry: A Comprehensive Review

In recent years, nanoparticles (NPs) have been receiving more attention in dentistry. Their advantageous physicochemical and biological properties can improve the diagnosis, prevention, and treatment of numerous oral diseases, including dental caries, periodontal diseases, pulp and periapical lesions, oral candidiasis, denture stomatitis, hyposalivation, and head, neck, and oral cancer. NPs can also enhance the mechanical and microbiological properties of dental prostheses and implants and can be used to improve drug delivery through the oral mucosa. This paper reviewed studies from 2015 to 2020 and summarized the potential applications of different types of NPs in the many fields of dentistry.

Closed Repair Technique: Innovative Surface Design for Polymethylmethacrylate Denture Base Repair

PURPOSE

This study aimed to evaluate the repair strength of a newly introduced repair technique involving zero-gap repair width.

MATERIALS AND METHODS

A total of 36 rectangular prism specimens with dimensions of 64 × 10 × 3.3 mm were prepared from heat-polymerized acrylic resin. Nine specimens were kept intact. The other specimens were sectioned into halves and modified to create repair gaps of 2.5-mm beveled (2.5B) as control, 0-mm beveled (ZB), and 0-mm inverse bi-beveled (ZIBB). The ZIBB group was prepared with a V-shaped internal groove on both halves (repair tunnel), while the intaglio and cameo surfaces were kept intact except for two small holes at the cameo surface for repair resin injection. The 2.5B and ZB groups were repaired conventionally while the ZIBB group was repaired by injecting repair resin into the tunnel through one of the holes until excess material oozed from the other hole. Repaired specimens were thermally cycled at 5 and 55°C for 10,000 cycles with 1 min dwell time. A 3-point bending test was conducted using a universal testing machine for flexural strength and elastic modulus measurement. Kruskal-Wallis/Mann-Whitney tests and ANOVA/post hoc Tukey tests were applied for data analysis (α = 0.05).

RESULTS

The flexural strength of repaired specimens was substantially lower than that of intact specimens, and significant differences were present between repaired groups (p ˂ 0.05). ZB and ZIBB had higher flexural strength (p ˂ 0.001) and elastic modulus (p ˂ 0.05) than 2.5B. Among the ZB and ZIBB groups, ZB showed the highest flexural strength, and ZIBB had the highest elastic modulus.

CONCLUSION

The closed repair technique improved the flexural strength and elastic modulus of repaired acrylic denture base.

Nanometals in Dentistry: Applications and Toxicological Implications-a Systematic Review

Nanotechnology is a vital part of health care system, including the dentistry. This branch of technology has been incorporated into various fields of dentistry ranging from diagnosis to prevention and treatment. The latter involves application of numerous biomaterials that help in restoration of esthetic and functional dentition. Over the past decade, these materials were modified through the incorporation of metal nanoparticles (NP) like silver (Ag), gold (Au), titanium (Ti), zinc (Zn), copper (Cu), and zirconia (Zr). They enhanced antimicrobial, mechanical, and regenerative properties of these materials. However, lately, the toxicological implications of these nanometal particles have been realized. They were associated with cytotoxicity, genotoxicity altered inflammatory processes, and reticuloendothelial system toxicity. As dental biomaterials containing metal NPs remain functional in oral cavity over prolonged periods, it is important to know their toxicological effects in humans. With this background, the present systematic review is aimed to gain an insight into the plausible applications and toxic implications of nano-metal particles as related to dentistry.

Influence of artificial aging and ZrO2 nanoparticle-reinforced repair resin on the denture repair strength

Background

The purpose of this study was to evaluate the effect of aging process on the tensile strength (TS) of repaired acrylic denture base using ZrO2 nanoparticles (nano-ZrO2)-reinforced autopolymerized resin.

Material and Methods

A total of 240 heat-polymerized acrylic resin specimens (n=10) were prepared and sectioned creating 2 mm-repair-gap. Autopolymerized acrylic resin, pure and modified with 2.5, 5, and 7.5wt% nano-ZrO2 were used for specimens repair. TS of repaired specimens were measured using the universal testing machine after water immersion at 37oC for 2, 7 and 30 days. At each time interval, half the immersed specimens underwent thermo-cycling aging process (5000 cycles at 5/55°C) before TS testing. One-way ANOVA and Tukey-Kramer multiple-comparison tests were used for data analysis at α=0.05.

Results

Aging process for all groups showed significant differences in TS between unreinforced and nano-ZrO2 reinforced groups (p<0.05). Within immersed nano-ZrO2-reinforced specimens, 5% group immersed for 30-days showed the highest significant TS value (p<0.05). With regards to thermocycling, 5% group showed the highest TS values after 2-days and 30-days groups while after 7-days, significant differences were found between 2.5% group and 5% and 7.5% groups (p<0.05). SEM images analysis displayed the ductile fracture type for nano-ZrO2 reinforced groups.

Conclusions

In summary, 5.0%-nano-ZrO2 addition to repair resin showed an improvement in tensile strength of repaired acrylic resin with different aging processes. Key words:Acrylic resins, denture repair, tensile strength, thermocycling, water storage, zirconium oxide nanoparticle.

Impact of different surface treatments and repair material reinforcement on the flexural strength of repaired PMMA denture base material

This study assessed the impact of surface treatments and repair resin reinforcement with zirconium oxide nano-particles (nano-ZrO₂) on flexural strength (FS) of repaired denture base. A total of 320 heat-polymerized acrylic resin specimens were prepared and sectioned creating 2-mm gap. According to repair surface treatment, specimens were distributed into four groups: I) methyl methacrylate (M); II) alumina-blasted (AB); III) AB+silane coupling agent (SC); and IV) AB+methacrylate based composite bonding agent (MA). Groups were subdivided into 4 (n=20) according to nano-ZrO₂ concentration (0, 2.5, 5, 7.5 wt%). Half the specimens were thermo-cycled before testing. FS was determined by three-point bending test. Statistical analysis was done using ANOVA and Tukey-Kramer multiple comparison tests, with α=0.05. Alumina-blasting+(SC) or (MA) significantly increased FS of repaired specimens compared to control (p<0.05). All surface-treated specimens combined with nano-ZrO₂ reinforced repair resin significantly increased FS.

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

Objective  The objective of this study was to evaluate the effect of nano-SiO ₂ addition on the flexural strength (FS) of repaired acrylic denture base.

Materials and Methods  Heat-polymerized acrylic resin specimens were fabricated in dimensions of (65 × 10 × 2.5 ± 0.1 mm ³ ) and then sectioned and prepared, creating repair gap with butt (90 degrees) and bevel (45 degrees) repair surface designs forming two main groups according to joint design. Further subdivision was done into four groups ( n = 10) according to nano-SiO ₂ concentration: one unmodified group and three modified groups (0.25, 0.5, and 0.75 wt %) in the autopolymerized repair resin. Each pair of a specimen was assembled in a mold and repaired according to manufacturer’s recommendations.

Statistical Analysis  Three-point bending test was done to measure FS, followed by scanning electron microscope (SEM) examination for fracture surface analysis. Data were analyzed using ANOVA and Tukey’s post hoc test (α = 0.05).

Results  The addition of nano-SiO ₂ significantly improved FS of repaired acrylic resin in comparison to the unmodified group ( p ˂ 0.05). For butt joint, significant differences between nano-SiO ₂ reinforced groups were noticed ( p ˂ 0.05), while reinforced beveled groups did not differ significantly ( p ˃ 0.05). Bevel design remarkably increased FS compared with butt design per respective filler concentration. From the SEM images, improved FS was presented with a homogeneous distribution of nano-SiO ₂ within polymethyl methacrylate.

Conclusion  Nano-SiO ₂ addition to repair resin and 45 degree-beveled repair surface increased FS of repaired acrylic resin.

Comparative Effect of Glass Fiber and Nano-Filler Addition on Denture Repair Strength

PURPOSE

To evaluate and compare the effects of glass fiber (GF), Zirconium oxide nanoparticles (nano-ZrO₂ ), and silicon dioxide nanoparticles (nano-SiO₂ ) addition on the flexural strength and impact strength of repaired denture base material.

MATERIALS AND METHODS

Heat-polymerized acrylic resin specimens were fabricated. All specimens were sectioned centrally and beveled creating 2.5 mm repair gap except for 10 controls. Specimen grouping (n = 10/group) was done according to filler concentration of 0%, 0.25%, 0.5%, and 0.75% of auto-polymerized acrylic powder. Modified resin was mixed, packed in the repair gap, polymerized, finished and polished. Three-point bending test and Charpy type impact testing were done. Data were analyzed using one-way-ANOVA and Post-Hoc Tukey test (α = 0.05).

RESULTS

All additives significantly increased flexural strength and impact strength (p < 0.05). Within the modified subgroups, no significant differences were found for GF. Significant increase for nano-ZrO₂ and significant decrease for nano-SiO₂ as the concentration of additive increased were noted for both flexural strength and impact strength. Highest flexural strength was found with 0.75%-nano-ZrO₂ (69.59 ± 2.52MPa) and the lowest was found with 0.75%-nano-SiO₂ (53.82 ± 3.10MPa). The 0.25%-nano-SiO₂ showed the highest impact strength value (2.54 ± 0.21 kJ/m² ) while the lowest impact strength value was seen with 0.75%-nano-SiO₂ (1.54 ± 0.17 kJ/m² ).

CONCLUSION

Nano-filler effect was concentration dependent and its addition to repair resin increased the flexural and impact strengths. The incorporation of 0.75%-ZrO₂ or 0.25%-SiO₂ into repair resin proved to be a promising technique to enhance repair strength and avoid repeated fractures.

Reinforcement of PMMA Denture Base Material with a Mixture of ZrO2 Nanoparticles and Glass Fibers

This study is aimed at evaluating the hybrid reinforcement effects of zirconium oxide nanoparticles (nano-ZrO₂) and glass fibers (GFs) at different ratios on the flexural and impact strengths of a polymethylmethacrylate (PMMA) denture base. A total of 160 specimens were fabricated from heat-polymerized acrylic resins using the water bath technique. For the control group, the specimens did not receive any additions; for the test group, different concentrations of nano-ZrO₂/GFs at 5% of the PMMA polymer were added. The concentrations of nano-ZrO₂/GFs were as follows: 5%–0%, 4%–1%, 3%–2%, 2.5%–2.5%, 2%–3%, 1%–4%, and 0%–5%. The flexural strength was measured using the three-point bending test. The impact strength was measured using the Charpy impact test. Results were tabulated and analyzed using one-way analysis of variance (ANOVA) and the Tukey–Kramer multiple comparison test (p ≤ 0.05). The flexural and impact strengths of PMMA-nano-ZrO₂ + GF composites were significantly improved when compared with those of pure PMMA (p < 0.05). The maximum flexural strength (94.05 ± 6.95 MPa) and impact strength (3.89 ± 0.46 kJ/m²) were obtained with PMMA (2.5%)/nano-ZrO₂ + 2.5% GF mixtures and could be used for removable prosthesis fabrication.

Impact Strength and Dimensional Accuracy of Heat-Cure Denture Base Resin Reinforced With ZrO2 Nanoparticles: An In Vitro Study

Background:

Polymerization shrinkage and fracture are the two common trouble shoots with denture base resins. Polymerization shrinkage affects the dimensional accuracy and fit of the prosthesis. The effect of zirconia (ZrO₂) nanoparticles on polymerization shrinkage is not documented yet.

Purpose:

The aim and objective of this study were to evaluate the impact strength and dimensional accuracy of heat-cured poly methyl methacrylate (PMMA) on reinforcement with ZrO₂ nanoparticles.

Materials and Methods:

Conventional heat-cure denture base resin (control) and the polymer reinforced with 3, 5, and 7 wt% of ZrO₂ nanoparticles were prepared and used in this study. Forty bar-shaped specimens were prepared and tested for impact strength using Charpy’s type impact tester. Forty denture bases were fabricated and checked for dimensional accuracy by measuring the distance between the denture base and the cast in two different sections using the travelling microscope.

Results:

The impact strength decreased with increased concentration of ZrO₂ and found to be least at 7 wt% concentration (2.01 ± 0.26 J/mm²). The distance between the denture base and the cast significantly decreased both in the posterior palatal seal region (0.060 ± 0.007 cm) and mid-palatine section region (0.057 ± 0.006 cm) with ZrO₂ nanoparticles reinforcement and was found to be least at 7 wt% concentration.

Conclusion:

Reinforcement of heat-cured PMMA with ZrO₂ nanoparticles significantly increased the dimensional accuracy and decreased the impact strength.

The effects of adding various ratios of zirconium oxide nanoparticles to poly(methyl methacrylate) on physical and mechanical properties

The aim of the present study is to evaluate the transverse strength, modulus of elasticity, surface roughness, hardness, and water sorption/solubility of nanoparticle zirconium oxide (nano-ZrO₂) added to heat-cured poly(methyl methacrylate) (PMMA) after thermocycling. The specimens were divided into four groups according to the ratio of nano-ZrO₂ addition to heat-cured PMMA; group 1: 5% nano-ZrO₂; group 2: 10% nano-ZrO₂; group 3: 20% nano-ZrO₂, and group 4 (control): PMMA without nano-ZrO₂. A statistically significant decrease in transverse strength was observed by all additional rates of nano-ZrO₂ compared with group 4 (control; P < 0.025). When hardness results were evaluated, groups 1 and 2 showed statistically higher values compared with groups 3 and 4 (P < 0.025). The surface roughness of group 3 was statistically higher than the other groups (P < 0.025), but it was within the clinically acceptable limits. As the nano-ZrO₂ addition rate increased, water sorption/solubility values of the specimens also increased. Although nano-ZrO₂ addition had an adverse effect on some mechanical and physical properties of heat-cured PMMA, it increased hardness values, implying that the addition of nano-ZrO₂ would contribute positively to some mechanical properties of PMMA denture base material when nano-ZrO₂ was homogeneously distributed in PMMA.

The implications and applications of nanotechnology in dentistry: A review

The emerging science of nanotechnology, especially within the dental and medical fields, sparked a research interest in their potential applications and benefits in comparison to conventional materials used. Therefore, a better understanding of the science behind nanotechnology is essential to appreciate how these materials can be utilised in our daily practice. The present paper will help the reader understand nanoscience, and the benefits and limitations of nanotechnology by addressing its ethical, social, and health implications. Additionally, nano-applications in dental diagnostics, dental prevention, and in dental materials will be addressed, with examples of commercially available products and evidence on their clinical performance.

Effect of zirconium oxide nanoparticles addition on the optical and tensile properties of polymethyl methacrylate denture base material

Background

Polymethyl methacrylate (PMMA) is widely used for the fabrication of removable prostheses. Recently, zirconium oxide nanoparticles (nano-ZrO₂) have been added to improve some properties of PMMA, but their effect on the optical properties and tensile strength are neglected.

Objective

The aim of this study was to investigate the effect of nano-ZrO₂ addition on the translucency and tensile strength of the PMMA denture base material.

Materials and methods

Eighty specimens (40 dumbbell-shaped and 40 discs) were prepared out of heat-polymerized acrylic resin and divided into four groups per test (n=10). The control group for each test included unreinforced acrylic, while the test groups were reinforced with 2.5, 5, and 7.5 wt% nano-ZrO₂. Acrylic resin was mixed according to manufacturer’s instructions, packed, and processed by conventional method. After polymerization, all specimens were finished, polished, and stored in distilled water at 37°C for 48±2 hours. Tensile strength (MPa) was evaluated using the universal testing machine while the specimens’ translucency was examined using a spectrophotometer. Statistical analysis was carried out by SPSS using the paired sample t-test (p≤0.05). A scanning electron microscope was used to analyze the morphological changes and topography of the fractured surfaces.

Results

This study showed that the mean tensile strength of the PMMA in the test groups of 2.5%NZ, 5%NZ, and 7.5%NZ was significantly higher than the control group. The tensile strength increased significantly after nano-ZrO₂ addition, and the maximum increase seen was in the 7.5%NZ group. The translucency values of the experimental groups were significantly lower than those of the control group. Within the reinforced groups, the 2.5%NZ group had significantly higher translucency values when compared to the 5%NZ and 7.5%NZ groups.

Conclusion

The addition of nano-ZrO₂ increased the tensile strength of the denture base acrylic. The increase was directly proportional to the nano-ZrO₂ concentration. The translucency of the PMMA was reduced as the nano-ZrO₂ increased.

Clinical significance

Based on the results of the current study, the tensile strength was improved with different percentages of nano-ZrO₂ additions. However, translucency was adversely affected. Therefore, it is important to determine the appropriate amount of reinforcing nano-ZrO₂ that will create a balance between achieved properties – mechanical and optical.

A Comparative Evaluation of Effect of Reinforced Autopolymerizing Resin on the Flexural Strength of Repaired Heat-polymerized Denture Base Resin before and after Thermocycling

Aims and Objective:

Denture fractures are a common problem in clinical practice. Despite the use of different reinforcement materials (metal wires, metal plates, and various types of fibers) for denture repairs, recurrent fractures are still common. The purpose of this study was to compare the maximum flexural loads of the heat-polymerized denture base resin when repaired with autopolymerizing resin reinforced with relatively smaller diameter metal wires and glass fibers, before and after thermocycling.

Materials and Methods:

Heat polymerized rectangular specimens were fabricated and repaired with autopolymerized resin and different reinforcement materials. Stainless steel wires, coaxial wires, beta-titanium wires, and glass fibers were used as reinforcement materials. Metal wires were sandblasted before placing in the center of the specimen along with autopolymerizing resin. Control specimens were repaired without any reinforcements. Intact heat- and self-cure specimens were also prepared for comparison. Half of the specimens of each group were subjected to thermocycle stressing (5°C and 55°C, 30 s dwell time) for 2000 cycles. All the specimens, nonthermocycled as well as thermocycled, were then tested for flexural strength by using 3 point flexural test in Lloyd's Universal testing machine at 5 mm/min crosshead speed. The maximum flexural loads (N) for each specimen were recorded. The readings, thus obtained, were subjected to statistical analysis using two-way ANOVA and Tukey's multiple comparison test.

Results:

The metal wire reinforcements increased the flexural strength of repaired specimens, whereas, glass fiber reinforcement produced slightly lower flexural strength when compared to those of control specimens, i.e., repair without any reinforcement. The highest flexural strength was demonstrated by specimens repaired with coaxial wire reinforcements (50.01 and 43.77 N before and after thermocycling, respectively). The increase in flexural strength with the use of stainless steel wire (45.12 and 41.56 N) and beta-titanium wire reinforcements (45.54 and 42.61N) was insignificant.

Conclusions:

Coaxial wire reinforcement produced significantly higher flexural loads than control. Increase in strength with stainless steel wire and beta-titanium wire was insignificant, whereas glass fiber reinforcement reduced the strength.

Inhibitory effect of zirconium oxide nanoparticles on Candida albicans adhesion to repaired polymethyl methacrylate denture bases and interim removable prostheses: a new approach for denture stomatitis prevention

BACKGROUND

Despite drawbacks, cold-cured acrylic resin is still the most common material used in denture repair. Zirconia nanoparticles were among the reinforcements added to increase the strength of the resin. The effect on Candida due to the addition of zirconia nanoparticles to the resin has not been investigated.

PURPOSE

The aim of this study was to evaluate the effect of zirconia nanoparticles added to cold-cured acrylic resin on Candida albicans adhesion.

MATERIALS AND METHODS

A total of 120 acrylic resin specimens with dimensions measuring 22×10×2.5 mm3 were prepared and divided into two equal groups. One group (repair) comprised heat-polymerized specimens that were sectioned at the center and prepared to create a 2 mm repair area that was repaired with cold-cured resin reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. The second group contained intact cold-cured acrylic resin specimens reinforced with 0% wt, 2.5% wt, 5% wt, and 7.5% wt zirconia nanoparticles. Specimens were incubated at 37°C in artificial saliva containing C. albicans, and the effect of zirconia nanoparticles on C. albicans was assessed using two methods: 1) a slide count method and 2) a direct culture test. Variations in the number of living Candida were observed in relation to the different concentrations of zirconia nanoparticles. Analysis of variance (ANOVA) and post hoc Tukey's tests were performed for data analysis. If the P-value was ≤0.05, then the difference was considered as statistically significant.

RESULTS

It was found that C. albicans adhesion to repaired specimens was significantly decreased by the addition of zirconia nanoparticles (P<0.00001) in comparison with the control group. Intact cold-cured groups and groups repaired with cold-cured resin reinforced with 7.5% wt zirconia nanoparticles showed the lowest Candida count. Tukey's test showed a significant difference between the repaired group and the intact cold-cured group, while the later demonstrated a lower Candida count.

CONCLUSION

The addition of zirconia nanoparticles to cold-cured acrylic resin is an effective method for reducing Candida adhesion to repaired polymethyl methacrylate (PMMA) denture bases and cold-cured removable prosthesis.

CLINICAL SIGNIFICANCE

Based on the results of the current study, zirconia nanoparticles have an antifungal effect, which could be incorporated in the repair material for repairing denture bases and in PMMA removable prostheses as a possible approach for denture stomatitis prevention.

Flexural Strength of Polymethyl Methacrylate Repaired with Fiberglass

OBJECTIVES

The purpose of this experimental study was to discover a method to increase the strength of repaired polymethyl methacrylate (PMMA) samples.

MATERIALS AND METHODS

In this experimental study, 40 specimens with the dimensions of 65×10×2.5mm³ were fabricated using heat-curing acrylic resin. Sixteen specimens were repaired with fiberglass and self-curing PMMA, while 16 samples were repaired with self-curing PMMA. Eight specimens were left intact as the control group. Afterwards, the flexural strengths of the repaired and intact specimens were measured by three-point bending test in a universal testing machine. Data were analyzed with one-way analysis of variance (ANOVA) and Tukey's HSD and LSD tests. The level of significance was set at P<0.05.

RESULTS

The mean flexural strength of the samples repaired with fiberglass was higher than that of the other repaired samples. However, the difference was statistically significant only with respect to the Meliodent group (P=0.008).

CONCLUSIONS

Impregnated fiberglass could be used in the repair of denture bases to improve the flexural strength. In terms of the fracture site, it can be concluded that the lower flexural strength of the auto-polymerizing acryl compared to that of the heat-curing type was the main reason for the occurrence of fractures, rather than the weak bond between heat-curing and auto-polymerizing acrylic resins.

PMMA denture base material enhancement: a review of fiber, filler, and nanofiller addition

This paper reviews acrylic denture base resin enhancement during the past few decades. Specific attention is given to the effect of fiber, filler, and nanofiller addition on poly(methyl methacrylate) (PMMA) properties. The review is based on scientific reviews, papers, and abstracts, as well as studies concerning the effect of additives, fibers, fillers, and reinforcement materials on PMMA, published between 1974 and 2016. Many studies have reported improvement of PMMA denture base material with the addition of fillers, fibers, nanofiller, and hybrid reinforcement. However, most of the studies were limited to in vitro investigations without bioactivity and clinical implications. Considering the findings of the review, there is no ideal denture base material, but the properties of PMMA could be improved with some modifications, especially with silanized nanoparticle addition and a hybrid reinforcement system.

Influence of incorporation of ZrO2 nanoparticles on the repair strength of polymethyl methacrylate denture bases

BACKGROUND

Repeated fracture of the denture base is a common problem in prosthodontics, and it represents a nuisance and a time sink for the clinician. Therefore, the possibility of increasing repair strength using new reinforcement materials is of great interest to prosthodontists.

AIM OF THE STUDY

This study aimed to evaluate the effects of incorporation of zirconia nanoparticles (nano-ZrO₂) on the flexural strength and impact strength of repaired polymethyl methacrylate (PMMA) denture bases.

MATERIALS AND METHODS

One hundred eighty specimens of heat-polymerized acrylic resin were fabricated (90 for each test) and divided into three main groups: one control group (intact specimens) and two groups divided according to surface design (45° bevels and butt joints), in which specimens were prepared in pairs to create 2.5 mm gaps. Nano-ZrO₂ was added to repair resin in 2.5 wt%, 5 wt%, and 7.5 wt% concentrations of acrylic powder. A three-point bending test was used to measure flexural strength, and a Charpy-type test was used to measure impact strength. Scanning electron microscopy was used to analyze the fracture surfaces and nano-ZrO₂ distribution. The results were analyzed with a paired sample t-test and an unpaired t-test, with a P-value of ≤0.05 being significant.

RESULTS

Incorporation of nano-ZrO₂ into the repair resin significantly increased flexural strength (P<0.05). The highest value was found in the bevel group reinforced with 7.5% nano-ZrO₂, whereas the lowest value was found in the butt group reinforced with 2.5% nano-ZrO₂. The impact strength values of all repaired groups were significantly lower than those of the control group (P<0.05). Among repaired groups, the higher impact strength value was seen in the butt group reinforced with 2.5% nano-ZrO₂. The bevel joint demonstrated mainly cohesive failure, whereas the butt joint demonstrated mainly adhesive failure.

CONCLUSION

Incorporation of nano-ZrO₂ into the repair resin improved the flexural strength of repaired denture bases, whereas it decreased impact strength, especially with high nano-ZrO₂ concentrations.