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

Benzyldimethyldodecyl Ammonium Chloride-Doped Denture-Based Resin: Impact on Strength, Surface Properties, Antifungal Activities, and In Silico Molecular Docking Analysis

Candida albicans (C. albicans) adhering to denture-based resins (DBRs) is a known cause of denture stomatitis. A new approach to prevent denture stomatitis is to include antimicrobial substances within DBRs. Here, we examined the mechanical performance and antifungal properties of DBRs containing benzyldimethyldodecyl ammonium chloride (C12BDMA-Cl) as an antimicrobial compound. C12BDMA-Cl is a quaternary ammonium compound, and its antifungal properties have never been investigated when combined with dental acrylic resin. Therefore, we modified a commercially available heat-polymerized acrylic DBR to contain 3 and 5 wt.% of C12BDMA-Cl. Unmodified DBR was used as a control group. Specimens were prepared using the conventional heat processing method. The specimen's flexural strength, elastic modulus, microhardness, and surface roughness were evaluated. C. albicans biofilm was grown on the specimens and assessed via colony-forming units (CFUs) and scanning electron microscopy (SEM). In silico molecular docking was applied to predict the potential C12BDMA-Cl inhibition activity as an antifungal drug. The 3% C12BDMA-Cl DBR demonstrated antifungal activities without a deterioration effect on the mechanical performance. SEM images indicated fewer colonies in DBR containing C12BDMA-Cl, which can be a potential approach to managing denture stomatitis. In conclusion, C12BDMA-Cl is a promising antifungal agent for preventing and treating denture stomatitis.

Repair strength of 3D-printed denture base resins: Effect of surface treatment and repair material type

PURPOSE

The aim of the study was to investigate the effect of surface treatment and repair materials on the flexural strength of repaired 3D-printed denture base resins after thermal aging.

MATERIALS AND METHODS

Bar-shape specimens (64 × 10 × 3.3 mm) were designed as intact (control) specimens while repair specimens were printed in sections with 2.5 mm space for repair material. Printing was performed with either ASIGA or NextDent denture base material. In each material, one group received no surface treatment, while other repair groups were subjected to one of three surface treatments: (1) monomer application, (2) aluminium oxide particles-abrasion, or (3) both methods (aluminum oxide particles-abrasion and monomer application). Pairs were fixed in a customized mold then repaired with either autopolymerizing acrylic resin or flowable composite (n = 9). Repaired specimens were incubated for 48 h at 37°C in distilled water and then subjected to thermal cycling (5000 cycles). A 3-point bending test was used to evaluate the flexural strength using a universal testing machine, and mode of failure determined followed by fractured surface analysis using scanning electron microscope. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05).

RESULTS

Both resin materials showed a significant decrease in the flexural strength of repaired specimens when compared to control ones (p < 0.001). Groups with no surface treatment had significantly lower flexural strength than those with surface treatment (p < 0.001). Groups treated with monomer application, and with aluminum oxide particles abrasion plus monomer application had similar flexural strength values (p > 0.05), which were higher than those treated with aluminum oxide particles abrasion alone (p < 0.001). Specimens repaired with composite resin showed higher flexural strength than those repaired with auto-polymerized resin (p < 0.05) however, specimens treated with aluminum oxide particles abrasion alone had similar values for both repair materials (p = 0.95). Adhesive failure was dominant in all repaired groups with auto-polymerized while cohesive and mixed were dominant with composite repair groups.

CONCLUSION

Surface treatment improved the repair strength of 3D-printed denture base resins. Using composite resin for repair shows better strength with dominant cohesive and mixed failure suggesting that surface treatment and composite repair are suitable procedures for 3D-printed denture base repair.

Mapping the research landscape of nanoparticles and their use in denture base resins: a bibliometric analysis

BACKGROUND

Nanoparticles are increasingly used in dentistry for various applications, including enhancing the mechanical properties of denture base resins. This study aimed to comprehensively review and analyze the research landscape of nanoparticles and their effect on the flexural strength of denture base resins to identify key research areas and trends and to highlight the importance of collaboration between authors and institutions.

METHODS

A Bibliometric Analysis was conducted using the Keywords "Nanoparticle*" AND "Denture*" OR "CAD/CAM." The literature search from the WOS database was restricted to the publication years 2011 to 2022.

RESULTS

Key findings encompass an increase in research publications but a decline in citations. Saudi Arabia, China, and Iraq led this research, with specific institutions excelling. Notable journals with high impact factors were identified. Authorship patterns show variations in citation impact. Additionally, keyword analysis revealed that current research trends offer insights into influential authors and their networks.

CONCLUSIONS

The analysis of nanoparticles and denture base resins reveals a dynamic and evolving landscape that emphasizes the importance of collaboration, staying current with research trends, and conducting high-quality research in this ever-evolving domain.

Effect of addition of titanium dioxide nanoparticles on the antimicrobial properties, surface roughness and surface hardness of polymethyl methacrylate: A Systematic Review

Background: Polymethyl Methacrylate (PMMA) denture-base resins have poor surface properties that facilitates microbial adhesion causing denture stomatitis. This systematic review aims to evaluate the effect of different sizes and percentages of titanium dioxide nanoparticles (TiO2NP) on the antimicrobial property, surface roughness and surface hardness of PMMA denture base resin.  Methods: A systematic search of English peer-reviewed articles, clinical trial registries, grey literature databases and other online sources was performed using the PRISMA-S Guidelines for In-Vivo and In-Vitro studies. Qualitative data synthesis was performed to analyse sample dimensions, acrylic used, treatments of nanoparticles, methods used for testing and effect of size and percentage of nanoparticle. Risk of bias assessment was done using modified Cochrane risk of bias tool. Results: Out of 1376 articles, 15 were included. TiO 2NP of size less than 30 nm was most frequently used. Both antimicrobial property and surface hardness improved irrespective of the size of the added TiO 2NP. Three studies reported increase in the surface roughness with less than 50 nm TiO 2NP.  3% TiO 2NP was most frequently used. On increasing the percentage, three studies reported an increase in antimicrobial property, while two studies found no change. With TiO 2NP greater than or equal to 3%, six studies reported an increase in surface hardness, while two reported increase in surface roughness. Large methodological variations were observed across studies. All studies except one were of moderate quality. Conclusions:   On addition of TiO 2NP to heat polymerized PMMA, the antimicrobial property and surface hardness improved irrespective of the size of the TiO 2NP, however, addition of nanoparticles less than 50 nm increased the surface roughness. Increasing the percentage of TiO 2NP increased the surface hardness but did not always increase the antimicrobial property. Addition of 3% TiO 2NP provided optimum results with regards to antimicrobial effect and surface hardness, but increase in the surface roughness.

Effect of Particle Sizes and Contents of Surface Pre-Reacted Glass Ionomer Filler on Mechanical Properties of Auto-Polymerizing Resin

Herein, the mechanical properties of an auto-polymerizing resin incorporated with a surface pre-reacted glass ionomer (S-PRG) filler were evaluated. For this, S-PRG fillers with particle sizes of 1 μm (S-PRG-1) and 3 μm (S-PRG-3) were mixed at 10, 20, 30, and 40 wt% to prepare experimental resin powders. The powders and a liquid (powder/liquid ratio = 1.0 g/0.5 mL) were kneaded and filled into a silicone mold to obtain rectangular specimens. The flexural strength and modulus (n = 12) were recorded via a three-point bending test. The flexural strengths of S-PRG-1 at 10 wt% (62.14 MPa) and S-PRG-3 at 10 and 20 wt% (68.68 and 62.70 MPa, respectively) were adequate (>60 MPa). The flexural modulus of the S-PRG-3-containing specimen was significantly higher than that of the S-PRG-1-containing specimen. Scanning electron microscopy observations of the specimen fracture surfaces after bending revealed that the S-PRG fillers were tightly embedded and scattered in the resin matrix. The Vickers hardness increased with an increasing filler content and size. The Vickers hardness of S-PRG-3 (14.86–15.48 HV) was higher than that of S-PRG-1 (13.48–14.97 HV). Thus, the particle size and content of the S-PRG filler affect the mechanical properties of the experimental auto-polymerizing resin.

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.

Repair Bond Strength of Conventionally and Digitally Fabricated Denture Base Resins to Auto-Polymerized Acrylic Resin: Surface Treatment Effects In Vitro

Denture base fracture is one of the most annoying problems for both prosthodontists and patients. Denture repair is considered to be an appropriate solution rather than fabricating a new denture. Digital denture fabrication is widely spreading nowadays. However, the repair strength of CAD-CAM milled and 3D-printed resins is lacking. This study aimed to evaluate the effect of surface treatment on the shear bond strength (SBS) of conventionally and digitally fabricated denture base resins. One l heat-polymerized (Major base20), two milled (IvoCad, AvaDent), and three 3D-printed (ASIGA, NextDent, FormLabs) denture base resins were used to fabricate 10 × 10 × 3.3 acrylic specimens (N = 180, 30/resin, n = 10). Specimens were divided into three groups according to surface treatment; no treatment (control), monomer application (MMA), or sandblasting (SB) surface treatments were performed. Repair resin was bonded to the resin surface followed by thermocycling (5000 cycles). SBS was tested using a universal testing machine where a load was applied at the resin interface (0.5 mm/min). Data were collected and analyzed using ANOVA and a post hoc Tukey test (α = 0.05). SEM was used for failure type and topography of fractured surfaces analysis. The heat-polymerized and CAD-CAM milled groups showed close SBS values without significance (p > 0.05), while the 3D-printed resin groups showed a significant decrease in SBS (p < 0.0001). SBS increased significantly with monomer application (p < 0.0001) except for the ASIGA and NextDent groups, which showed no significant difference compared to the control groups (p > 0.05). All materials with SB surface treatment showed a significant increase in SBS when compared with the controls and MMA application (p < 0.0001). Adhesive failure type was observed in the control groups, which dramatically changed to cohesive or mixed in groups with surface treatment. The SBS of 3D-printed resin was decreased when compared with the conventional and CAD-CAM milled resin. Regardless of the material type, SB and MMA applications increased the SBS of the repaired resin and SB showed high performance.

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.

Influence of ZrO2 Nanoparticle Addition on the Optical Properties of Denture Base Materials Fabricated Using Additive Technologies

This study investigated the translucency of 3D-printed denture base resins modified with zirconium dioxide nanoparticles (ZrO₂NPs) under thermal cycling. A total of 110 specimens were fabricated and divided into 3 groups according to the materials, i.e., heat-polymerized resin, and 3D-printed resins (NextDent, and ASIGA). The 3D-printed resins were modified with 0, 0.5, 1, 3, and 5 wt.% of ZrO₂NPs. All the specimens were subjected to 5000 thermal cycles. The translucency was measured using a spectrophotometer. The results showed that the heat-polymerized resin had considerably higher translucency than the 3D-printed resins. Compared to the unmodified group, the translucency decreased significantly after adding 5% ZrO₂NPs to NextDent and 3% ZrO₂NPs to ASIGA resins. The highest translucency was achieved for NextDent by adding 0.5% ZrO₂NPs and for ASIGA without any ZrO₂NPs. It was found that the average concentration level in ASIGA was significantly higher than that in NextDent. These findings revealed that 3D-printed resins have lower translucency than heat-polymerized acrylic resin, and adding ZrO₂NPs at low concentrations did not affect the translucency of the 3D-printed resins. Therefore, in terms of translucency, 3D-printed nanocomposite denture base resins could be considered for clinical applications when ZrO₂NPs are added at low concentrations.

Medical and Dental Applications of Titania Nanoparticles: An Overview

Currently, titanium oxide (TiO₂) nanoparticles are successfully employed in human food, drugs, cosmetics, advanced medicine, and dentistry because of their non-cytotoxic, non-allergic, and bio-compatible nature when used in direct close contact with the human body. These NPs are the most versatile oxides as a result of their acceptable chemical stability, lower cost, strong oxidation properties, high refractive index, and enhanced aesthetics. These NPs are fabricated by conventional (physical and chemical) methods and the latest biological methods (biological, green, and biological derivatives), with their advantages and disadvantages in this epoch. The significance of TiO₂ NPs as a medical material includes drug delivery release, cancer therapy, orthopedic implants, biosensors, instruments, and devices, whereas their significance as a dental biomaterial involves dentifrices, oral antibacterial disinfectants, whitening agents, and adhesives. In addition, TiO₂ NPs play an important role in orthodontics (wires and brackets), endodontics (sealers and obturating materials), maxillofacial surgeries (implants and bone plates), prosthodontics (veneers, crowns, bridges, and acrylic resin dentures), and restorative dentistry (GIC and composites).

Effect of Reinforced Self-Cured Acrylic Resin on Flexural Strength

Introduction

The aim of this study was to determine the effect on the flexural strength of the self-cured acrylic resin by incorporating short E-glass fiber (SEGF) and ultra-high-molecular-weight polyethylene (UHMW-PE) filler in the acrylic resin.

Methods

Fifty-six rectangular (64 × 10 × 3.3 mm³) (ISO standard 20795–1:2013) self-cured acrylic resin specimens were fabricated and divided into seven groups per test, according to the percent by weight of SEGF and UHMW-PE filler (n = 8). Each testing group entails a control group and an addition of 1% and 2% SEGF, 1% and 2% UHMW-PE, 0.5% SEGF/UHMW-PE, and 1% SEGF/UHMW-PE. A three-point bending test was conducted to obtain the flexural strength of each specimen. The fractured surfaces of the specimens were evaluated, and a scanning electron microscope view was taken. Test results were statistically analyzed with one-way ANOVA and Tukey HSD tests (p value<0.05).

Results

The flexural strength of self-cured acrylic resin with the addition of 1% SEGF and 1% SEGF/UHMW-PE (50.93, 46.13 MPa) was significantly higher than that of the control group (41.72 MPa) (p < 0.05). Nonetheless, the addition of 1% UHMW-PE (39.34 MPa) showed the lowest flexural strength, significantly lower than other experimental groups, except the control group.

Conclusion

The addition of 1% SEGF significantly improves the flexural strength of the self-cured acrylic resin denture base.

3D-Printed Nanocomposite Denture-Base Resins: Effect of ZrO2 Nanoparticles on the Mechanical and Surface Properties In Vitro

Due to the low mechanical performances of 3D-printed denture base resins, ZrO2 nanoparticles (ZrO2NPs) were incorporated into different 3D-printed resins and their effects on the flexure strength, elastic modulus, impact strength, hardness, and surface roughness were evaluated. A total of 286 specimens were fabricated in dimensions per respective test and divided according to materials into three groups: heat-polymerized as a control group and two 3D-printed resins (NextDent and ASIGA) which were modified with 0.5 wt.%, 1 wt.%, 3 wt.%, and 5 wt.% ZrO2NPs. The flexure strength and elastic modulus, impact strength, hardness, and surface roughness (µm) were measured using the three-point bending test, Charpy’s impact test, Vickers hardness test, and a profilometer, respectively. The data were analyzed by ANOVA and Tukey’s post hoc test (α = 0.05). The results showed that, in comparison to heat-polymerized resin, the unmodified 3D-printed resins showed a significant decrease in all tested properties (p < 0.001) except surface roughness (p = 0.11). In between 3D-printed resins, the addition of ZrO2NPs to 3D-printed resins showed a significant increase in flexure strength, impact strength, and hardness (p < 0.05) while showing no significant differences in surface roughness and elastic modulus (p > 0.05). Our study demonstrated that the unmodified 3D-printed resins showed inferior mechanical behavior when compared with heat-polymerized acrylic resin while the addition of ZrO2NPs improved the properties of 3D-printed resins. Therefore, the introduced 3D-printable nanocomposite denture-base resins are suitable for clinical use.

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.

The Influence of Various Photoinitiators on the Properties of Commercial Dental Composites

The aim of this article was to compare the biomechanical properties of commercial composites containing different photoinitiators: Filtek Ultimate (3M ESPE) containing camphorquinone (CQ); Estelite Σ Quick (Tokuyama Dental) with CQ in RAP Technology^®; Tetric EvoCeram Bleach BLXL (Ivoclar Vivadent AG) with CQ and Lucirin TPO; and Tetric Evoceram Powerfill IVB (Ivoclar Vivadent AG) with CQ and Ivocerin TPO. All samples were cured with a polywave Valo Lamp (Ultradent Products Inc.) with 1450 mW/cm². The microhardness, hardness by Vicker's method, diametral tensile strength, flexural strength and contraction stress with photoelastic analysis were tested. The highest hardness and microhardness were observed for Filtek Ultimate (93.82 ± 17.44 HV), but other composites also displayed sufficient values (from 52 ± 3.92 to 58,82 ± 7.33 HV). Filtek Ultimate not only demonstrated the highest DTS (48.03 ± 5.97 MPa) and FS (87.32 ± 19.03 MPa) but also the highest contraction stress (13.7 ± 0.4 MPa) during polymerization. The TetricEvoCeram Powerfill has optimal microhardness (54.27 ± 4.1 HV), DTS (32.5 ± 5.29 MPa) and FS (79.3 ± 14.37 MPa) and the lowest contraction stress (7.4 ± 1 MPa) during photopolymerization. To summarize, Filtek Ultimate demonstrated the highest microhardness, FS and DTS values; however, composites with additional photoinitiators such as Lucirin TPO and Ivocerin have the lowest polymerization shrinkage. These composites also have higher FS and DTS and microhardness than material containing CQ in Rap Technology.

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.

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.

Assessing Fracture Toughness and Impact Strength of PMMA Reinforced with Nano-Particles and Fibre as Advanced Denture Base Materials

Statement of Problem: Polymethyl methacrylate (PMMA) denture resins commonly fracture as a result of the denture being dropped or when in use due to heavy occlusal forces. Purpose: To investigate the effects of E-glass fibre, ZrO₂ and TiO₂ nanoparticles at different concentrations on the fracture toughness and impact strength of PMMA denture base. Materials and Methods: To evaluate fracture toughness (dimensions: 40 × 8 × 4 mm³; n = 10/group) and impact strength (dimensions: 80 × 10 × 4 mm³; n = 12/group), 286 rectangular tested specimens were prepared and divided into four groups. Group C consisted of the PMMA specimens without any filler (control group), while the specimens in the remaining three groups varied according to the concentration of three filler materials by weight of PMMA resin: 1.5%, 3%, 5%, and 7%. Three-point bending and Charpy impact tests were conducted to measure the fracture toughness and impact strength respectively. Scanning Electron Microscope (SEM) was utilised to examine the fractured surfaces of the specimens after the fracture toughness test. One-way analysis of variance (ANOVA) followed by Tukey post-hoc tests were employed to analyse the results at a p ≤ 0.05 significance level. Results: Fracture toughness of groups with 1.5 and 3 wt.% ZrO₂, 1.5 wt.% TiO₂, and all E-glass fibre concentrations were significantly higher (p < 0.05) than the control group. The samples reinforced with 3 wt.% ZrO₂ exhibited the highest fracture toughness. Those reinforced with a 3 wt.%, 5 wt.%, and 7 wt.% of E-glass fibres had a significantly (p < 0.05) higher impact strength than the specimens in the control group. The heat-cured PMMA modified with either ZrO₂ or TiO₂ nanoparticles did not exhibit a statistically significant difference in impact strength (p > 0.05) in comparison to the control group. Conclusions: 1.5 wt.%, 3 wt.% of ZrO₂; 1.5 wt.% ratios of TiO₂; and 1.5 wt.%, 3 wt.%, 5 wt.%, and 7 wt.% of E-glass fibre can effectively enhance the fracture toughness of PMMA. The inclusion of E-glass fibres does significantly improve impact strength, while ZrO₂ or TiO₂ nanoparticles did not.

Comparison of Mechanical Properties of PMMA Disks for Digitally Designed Dentures

In this study, the physical properties of a custom block manufactured using a self-polymerizing resin (Custom-block), the commercially available CAD/CAM PMMA disk (PMMA-disk), and a heat-polymerizing resin (Conventional PMMA) were evaluated via three different tests. The Custom-block was polymerized by pouring the self-polymerizing resin into a special tray, and Conventional PMMA was polymerized with a heat-curing method, according to the manufacturer’s recommended procedure. The specimens of each group were subjected to three-point bending, water sorption and solubility, and staining tests. The results showed that the materials met the requirements of the ISO standards in all tests, except for the staining tests. The highest flexural strength was exhibited by the PMMA-disk, followed by the Custom-block and the Conventional PMMA, and a significant difference was observed in the flexural strengths of all the materials (p < 0.001). The Custom-block showed a significantly higher flexural modulus and water solubility. The water sorption and discoloration of the Custom-block were significantly higher than those of the PMMA-disk, but not significantly different from those of the Conventional PMMA. In conclusion, the mechanical properties of the three materials differed depending on the manufacturing method, which considerably affected their flexural strength, flexural modulus, water sorption and solubility, and discoloration.

Flexural Strength and Hardness of Filler-Reinforced PMMA Targeted for Denture Base Application

The aim of this work was to evaluate the flexural strength and surface hardness of heat-cured Polymethyl methacrylate (PMMA) modified by the addition of ZrO₂ nanoparticles, TiO₂ nanoparticles, and E-glass fibre at different wt.% concentrations. Specimens were fabricated and separated into four groups (n = 10) to measure both flexural strength and surface hardness. Group C was the control group. The specimens in the remaining three groups differed according to the ratio of filler to weight of PMMA resin (1.5%, 3%, 5%, and 7%). A three-point bending test was performed to determine the flexural strength, while the surface hardness was measured using the Vickers hardness. Scanning Electron Microscope (SEM) was employed to observe the fractured surface of the specimens. The flexural strength was significantly improved in the groups filled with 3 wt.% ZrO₂ and 5 and 7 wt.% E-glass fibre in comparison to Group C. All the groups displayed a significantly higher surface hardness than Group C, with the exception of the 1.5% TiO₂ and 1.5% ZrO₂ groups. The optimal filler concentrations to enhance the flexural strength of PMMA resin were between 3–5% ZrO₂, 1.5% TiO₂, and 3–7% E-glass fibre. Furthermore, for all composites, a filler concentration of 3 wt.% and above would significantly improve hardness.

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.

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.