Effectiveness of Denture Cleansers on Candida albicans Biofilm on Conventionally Fabricated, Computer-Aided Design/Computer-Aided Manufacturing-Milled, and Rapid-Prototyped Denture Base Resins: An In Vitro Study.

INTRODUCTION: Conventionally fabricated denture base resins have been used for over 150 years. Newer denture base resins can provide a superior fit and may be customized to the patient's characteristics, but the literature on their cleansibility remains limited. The oral cavity can be a hub for thousands of microflora. The maintenance of complete dentures by edentulous patients depends not only on the maintenance of the patient but also on the material used, biofilm adherence, and polishability. MATERIALS AND METHODS: Cuboid specimens of 10 × 5 × 2 mm were designed using the Meshmixer version 3.5 software (Meshmixer, Australia). The standard tessellation (STL) file was imported and sent for printing (NextDent, Netherlands) (Group 1), milling in polymethyl methacrylate (PMMA) (Ivotion, Ivoclar, Schaan, Liechtenstein) (Group 2), and wax milling (Upcera, China), followed by flasking, counter flasking, and packing using heat-cured acrylic resin (DPI, India) (Group 3). The obtained specimens were polished using pumice and sterilized using a UV sterilization unit. The specimens were then immersed in a suspension of candida broth. After three days of biofilm formation, a colony count was performed and noted as colony-forming units per milliliter (CFU/mL). Specimens were treated using Secure denture cleansing tablets (Ghent, New York), table salt (iodized table salt, Tata, India), Clinsodent (ICPA, Mumbai, India), and Polident denture cleansing powder (Polident, Ontario, Canada). A colony count was done after treatment, and the data were tabulated. Statistical analysis was done using SPSS software to compare the efficiency of denture cleansers in all three groups, and statistical significance was set at 0.05. The Kolmogorov-Smirnov test was done to confirm the normality of the data, followed by a one-way analysis of variance (ANOVA) test to compare the efficiency of denture cleansers on the removal of candida colonies. RESULTS: Milled denture base resins showed a significantly lower colony count when compared to printed and conventionally fabricated denture base resins. The denture cleansers showed high efficacy in all groups, with the most significant being Secure, which showed a mean difference ranging from 8.114 to 9.887 CFU/mL, followed by Clinsodent, showing a mean of 6.699-9.863 CFU/mL, followed closely by Polident, showing 4.964-7.114 CFU/mL, followed by table salt, being 5.254-8.920 CFU/mL. The 95% confidence interval confirmed statistical significance. CONCLUSION: The highest candida colony count was demonstrated by the conventional, followed by rapid prototyping, and was least with milled denture base resins. Following treatment with denture cleansers, Secure demonstrated almost complete eradication of colonies, making it the most effective option. Salt exhibited the lowest efficiency, followed closely by Polident and Clinsodent, and the most effective was Secure denture cleanser.

An in vitro evaluation of bond strength and failure behavior between 3D-printed cobalt-chromium alloy and different types of denture base resins.

OBJECTIVES: This study aimed to evaluate the shear bond strength and failure behavior between cobalt-chromium (Co-Cr) alloy and different types of denture base resins (DBRs) over time. METHODS: Seventy-two disk-shaped specimens (8 mm in diameter and 2 mm in thickness) were manufactured using a selective laser melting technology-based metal 3D printer. Three types of DBRs were used: heat-cure (HEA group), cold-cure (COL group), and 3D-printable (TDP group) DBRs (n = 12 per group). Each DBR specimen was fabricated as a 5 mm × 5 mm × 5 mm cube model. The specimens of the TDP group were manufactured using a digital light processing technology-based 3D printer. Half of the DBRs were stored in distilled water at 37 °C for 24 h, whereas the remaining half underwent thermocycling for 10,000 cycles. Shear bond strength was measured using a universal testing machine; failure modes were observed, and metal surfaces were evaluated using energy dispersive spectrometry. RESULTS: The shear bond strength did not differ between the DBR types within the non-thermocycled groups. Contrarily, the TDP group exhibited inferior strength compared to the HEA group (P = 0.008) after thermocycling. All three types of DBRs exhibited a significant decrease in the shear bond strength and an increased tendency toward adhesive failure after thermocycling. CONCLUSIONS: The bond strength between 3D-printable DBRs and Co-Cr alloy was comparable to that of heat-and cold-cure DBRs before thermocycling. However, it exhibited a considerable weakening in comparison to heat-cure DBRs after simulated short-term use. CLINICAL SIGNIFICANCE: The application of 3D-printable DBR in metal framework-incorporated removable partial dentures may be feasible during the early phase of the treatment. However, its application is currently limited because the bond strength between the 3D-printable DBR and metal may weaken after short-term use. Further studies on methods to increase the bond strength between these heterogeneous materials are required.

Removal of an Atypical Foreign Body Using Flexible Bronchoscopy Under Local Anesthesia.

While uncommon among adults, the act of inhaling a foreign object is a grave incident that might potentially endanger one's life or result in substantial repercussions. A 43-year-old patient with a history of asthma and epilepsy from infancy appeared with worsening respiratory distress and the presence of purulent secretions one week following an epileptic seizure. The chest X-rays and abdominal ultrasound revealed no anomalies. A bronchoscopy performed with local anesthesia enabled clear vision of the foreign object, and its removal was successfully executed, eliminating the need for a more invasive procedure. Bronchoscopy is crucial for both diagnosis and treatment, particularly in cases where there is a suspicion of inhalation of a foreign object that cannot be seen on X-rays. However, X-rays can still be useful for detecting radiopaque foreign objects or for identifying indirect symptoms of their existence.

[Effect of printing orientation on physical and mechanical properties of 3D printing prosthodontic base resin materials].

OBJECTIVE: To analyze the influence of forming direction on the surface characteristics, elastic modulus, bending strength and fracture toughness of printed parts and the relationship between forming direction and force direction, and to provide scientific basis and guidance for the clinical application of oral denture base resin materials. METHODS: The 3D printing technology was used to print denture base resin samples. The shape and size of the samples referred to the current standard for testing conventional denture base materials. The samples used for physical performance testing were cylindrical (with a diameter of 15 mm and a thickness of 1 mm) and printed at different angles along the Z axis (0°, 45°, 90°). Scanning electron microscope was used to observe the microscopic topography of the different samples. The color stability of different samples was observed by color stabilizer. The surface roughness of the samples was analyzed by using surface roughness tester. The Vickers hardness was measured to analyze the hardness of the samples. The samples used for mechanical performance testing were rectangular (elastic modulus and bending strength: A length of 64 mm, a width of 10 mm, and a height of 3.3 mm; fracture toughness: A length of 39 mm, a width of 8 mm, and a height of 4 mm), divided into two groups: W group and H group. The W group was printed from the bottom up along the Z axis with the length × width as the bottom surface parallel to the X, Y axis plane, while the H group printed from the bottom up along the Z axis with the length × height as the bottom surface parallel to the X, Y axis plane. The forming angles of both groups were equally divided into 0°, 45°, and 90°. The elastic modulus, bending strength and fracture toughness of different samples were studied through universal mechanical testing machine. SPSS 22.0 software was used for statistical analysis. RESULTS: The microscopic topography and roughness of different samples were closely related to the printing direction, with significant differences between the 0°, 45°, and 90° specimens. The 0° specimens had the smoothest surface (roughness < 1 µm). The surface of the 45° specimen was the roughest (roughness>3 µm). The microhardness of the 0° sample was the best [(196.13±0.20) MPa], with a significant difference compared with the 90° sample [(186.62±4.81) MPa, P < 0.05]. The mechanical properties of different samples were also closely related to the printing direction. The elastic modulus, bending strength, and fracture toughness of the 45° samples in the W group were the highest compared with the other groups. The results of elastic modulus showed that in the H group, the 45° specimens had the highest elastic mo-dulus, which was significantly different from the 0° and 90° specimens (P < 0.05). The elastic modulus of 0° and 45° specimens in the W group were higher than those in 90° specimens (P < 0.05). The bending strength results showed that there was no significant difference between the specimens from dif-ferent angles in the H group. The bending strength of the 90° specimens in the W group was the smallest, and there was a significant difference between 90° and the 0° and 45° specimens (P < 0.05); And the bendind strength of the 0° and 45° specimens in the W group was significantly higher than that of the 0° and 45° specimens in the H group (P < 0.05). The fracture toughness results showed that the fracture toughness of the H group specimens was lower than 1.9 MPa m1/2, which was specified in the denture base standard. The 45° samples in the W group were the highest, with significant differences compared with the 0° and 90° samples (P < 0.05). And the 90° samples of the W group specimens were lower than 1.9 MPa m1/2. And the fracture toughness of the 45° specimen in the W group was significantly higher than that of all the specimens in the H group (P < 0.05). CONCLUSION: The 0° samples had relatively better physical properties. The 45° samples had the best mechanical properties. But the fracture toughness of specimens (H group and 90° samples of W group) did not yet meet clinical requirements. That indicated that the characteristics of the 3D printing denture base resin were affected by the printing direction. Only when the performance of the printed samples in all directions met the minimum requirements of the standard, they could be used in clinical practice.

Comparative Analysis of Strength of Differently Activated Denture Base Materials Including Recent Acetal Resin-Based Biodentaplast.

AIM AND OBJECTIVES: The aim of this study is to comparatively analyse the compressive and tensile strength of different types of record base materials made of different materials and processing techniques. MATERIALS AND METHODOLOGY: The compressive and tensile strength of 4 types of injection moulded materials were compared with a control of conventional compression moulded material. Twenty test specimens (10 tensile and 10 compressive) were fabricated from each material. A test was done using the Instron 3382 (Norwood, MA, USA) universal testing machine. RESULTS: Compressive and tensile test values showed significant differences between the record base resin groups tested for both compressive and tensile strength tests (p=0.00). The mean tensile strength value was greatest for Group V (66.0 MPa) and lowest for Group III (41.9MPa) and the mean compressive strength value was greatest for Group I (74.5 MPa) followed by Group V (70.2 MPa) and lowest for Group III (10.8 MPa). CONCLUSION: Injection moulded acetal resin showed the highest tensile strength value; it was comparable to that of conventional compression moulded polymethyl methacrylate (PMMA). Compression moulding is reported to have the highest compressive strength values followed by injection moulded acetal resin material. Injection moulded acetal resin material attributed to its advantages and superior strength value, can be used as a material of choice in various clinical scenarios.

Mechanophysical and Anti-Adhesive Properties of a Nanoclay-Containing PMMA Denture Resin.

Poly(methyl methacrylate) (PMMA) is commonly used for dental dentures, but it has the drawback of promoting oral health risks due to oral bacterial adhesion. Recently, various nanoparticles have been incorporated into PMMA to tackle these issues. This study aims to investigate the mechanophysical and antimicrobial adhesive properties of a denture resin by incorporating of nanoclay into PMMA. Specimens were prepared by adding 0, 1, 2, and 4 wt % surface-modified nanoclay (Sigma) to self-polymerizing PMMA denture resin. These specimens were then evaluated using FTIR, TGA/DTG, and FE-SEM with EDS. Various mechanical and surface physical properties, including nanoindentation, were measured and compared with those of pure PMMA. Antiadhesion experiments were conducted by applying a Candida albicans (ATCC 11006) suspension to the surface of the specimens. The antiadhesion activity of C. albicans was confirmed through a yeast-wall component (mannan) and mRNA-seq analysis. The bulk mechanical properties of nanoclay-PMMA composites were decreased compared to those of pure PMMA, while the flexural strength and modulus met the ISO 20795-1 requirement. However, there were no significant differences in the nanoindentation hardness and elastic modulus. The surface energy revealed a significant decrease at 4 wt % nanoclay-PMMA. The antiadhesion effect of Candida albicans was evident along with nanoclay content in the nanocomposites and confirmed by the reduced attachment of mannan on nanoclay-PMMA composites. mRNA-seq analysis supported overall transcriptome changes in altering attachment and metabolism behaviors on the surface. The nanoclay-PMMA materials showed a lower surface energy as the content increased, leading to an antiadhesion effect against Candida albicans. These findings indicate that incorporating nanoclay into PMMA surfaces could be a valuable strategy for preventing the fungal biofilm formation of denture base materials.

Fracture toughness, work of fracture, flexural strength and elastic modulus of 3D-printed denture base resins in two measurement environments after artificial aging.

OBJECTIVES: To investigate the fracture toughness (KIC), work of fracture (WOF), flexural strength (FS) and elastic modulus (E) of four additively manufactured denture base resins in two different measurement environments after artificial aging. METHODS: Rectangular specimens in two different dimensions (n = 480) were 3D-printed with four denture base resins: Denture 3D+ (DEN; NextDent), Fotodent Denture (FOT; Dreve ProDiMed), Freeprint Denture (FRE; Detax), V-Print dentbase (VPR; VOCO)). KIC, WOF, FS and E were measured after (1) water-storage (37 °C; KIC = 7 d; FS = 50 h); (2) water-storage + hydrothermal-aging (20 min, 0.2 MPa, 134 °C); (3) water storage + thermocycling (10,000 cycles, 5/55 °C) in two measurement environments (i) air-23 °C and (ii) water-37 °C. For FS, fracture types were classified, and relative frequencies determined. Univariate ANOVA, Kruskal-Wallis, Mann-Whitney U, and Spearman's correlation were calculated (p < 0.05, SPSS V.27.0). Weibull modulus (m) was calculated using the maximum likelihood estimation method. RESULTS: DEN showed the highest KIC (5/6 groups), WOF and highest corresponding m (1/6 groups), while FRE presented the highest FS (2/6 groups) and E values. Hydrothermal-aging and thermocycling reduced KIC and WOF, FS and E, and the number of FS fracture pieces. For 6/8 groups, hydrothermal aging resulted in lower FS than thermocycling. Measurement in air-23 °C led to higher FS for 7/12 groups and a more brittle fracture behavior. A positive correlation between KIC and FS was observed. SIGNIFICANCE: With measurements in air-23 °C resulting in higher FS than reported in water-37 °C, the measurement environment should be adapted to the clinical situation to allow valid predictions on the mechanical behavior of denture base resins when in situ.

Effect of printing orientation on physical and mechanical properties of 3D printing prosthodontic base resin materials / 北京大学学报(医学版)

Objective:To analyze the influence of forming direction on the surface characteristics,elastic modulus,bending strength and fracture toughness of printed parts and the relationship between forming direction and force direction,and to provide scientific basis and guidance for the clinical applica-tion of oral denture base resin materials.Methods:The 3D printing technology was used to print denture base resin samples.The shape and size of the samples referred to the current standard for testing conven-tional denture base materials.The samples used for physical performance testing were cylindrical(with a diameter of 15 mm and a thickness of 1 mm)and printed at different angles along the Z axis(0°,45°,90°).Scanning electron microscope was used to observe the microscopic topography of the different sam-ples.The color stability of different samples was observed by color stabilizer.The surface roughness of the samples was analyzed by using surface roughness tester.The Vickers hardness was measured to ana-lyze the hardness of the samples.The samples used for mechanical performance testing were rectangular(elastic modulus and bending strength:A length of 64 mm,a width of 10 mm,and a height of 3.3 mm;fracture toughness:A length of 39 mm,a width of 8 mm,and a height of 4 mm),divided into two groups:W group and H group.The W group was printed from the bottom up along the Z axis with the length × width as the bottom surface parallel to the X,Y axis plane,while the H group printed from the bottom up along the Z axis with the length × height as the bottom surface parallel to the X,Y axis plane.The forming angles of both groups were equally divided into 0°,45°,and 90°.The elastic modulus,bending strength and fracture toughness of different samples were studied through universal mechanical testing machine.SPSS 22.0 software was used for statistical analysis.Results:The microscopic topogra-phy and roughness of different samples were closely related to the printing direction,with significant differences between the 0°,45°,and 90° specimens.The 0° specimens had the smoothest surface(roughness＜1 μm).The surface of the 45 ° specimen was the roughest(roughness＞3 μm).The microhardness of the 0° sample was the best[(196.13±0.20)MPa],with a significant difference com-pared with the 90° sample[(186.62±4.81)MPa,P＜0.05].The mechanical properties of different samples were also closely related to the printing direction.The elastic modulus,bending strength,and fracture toughness of the 45° samples in the W group were the highest compared with the other groups.The results of elastic modulus showed that in the H group,the 45° specimens had the highest elastic mo-dulus,which was significantly different from the 0° and 90° specimens(P＜0.05).The elastic modulus of 0° and 45° specimens in the W group were higher than those in 90° specimens(P＜0.05).The bending strength results showed that there was no significant difference between the specimens from dif-ferent angles in the H group.The bending strength of the 90° specimens in the W group was the smallest,and there was a significant difference between 90° and the 0° and 45° specimens(P＜0.05);And the bendind strength of the 0° and 45° specimens in the W group was significantly higher than that of the 0° and 45° specimens in the H group(P＜0.05).The fracture toughness results showed that the fracture toughness of the H group specimens was lower than 1.9 MPa m1/2,which was specified in the denture base standard.The 45° samples in the W group were the highest,with significant differences compared with the 0° and 90° samples(P＜0.05).And the 90° samples of the W group specimens were lower than 1.9 MPa m1/2.And the fracture toughness of the 45° specimen in the W group was significantly higher than that of all the specimens in the H group(P＜0.05).Conclusion:The 0° samples had rela-tively better physical properties.The 45° samples had the best mechanical properties.But the fracture toughness of specimens(H group and 90° samples of W group)did not yet meet clinical requirements.That indicated that the characteristics of the 3D printing denture base resin were affected by the printing direction.Only when the performance of the printed samples in all directions met the minimum require-ments of the standard,they could be used in clinical practice.

Evaluation of Impact Strength and Flexural Strength of Polyether Ether Ketone vs. Computer-Aided Design/Computer-Aided Manufacturing Polymethyl Methacrylate Denture Base Materials: An In-Vitro Study.

OBJECTIVE: The objective is to comparatively assess the impact strength and flexural strength of polyether ether ketone (PEEK) vs. computer-aided design/computer-aided manufacturing (CAD/CAM) polymethyl methacrylate denture base material. METHODS: A total of 90 samples were fabricated with traditional heat cure PMMA, PEEK, and CAD/CAM PMMA and divided into three groups of 30 samples each. The impact strength of all the samples was measured using an Izod impact tester with a pendulum in the air at 23±2°C. A three-point bending test was used in a Universal Testing Machine to assess the flexural strength of all the samples. The impact strength and flexural strength mean values were computed using a one-way ANOVA test. RESULT: Impact strength and flexural strength of PEEK (IS=10.22±1.25 kJ/m2 and FS=120±8.0 MPa) is almost identical to CAD/CAM PMMA sample (IS=9.595±3.313 kJ/m2 and FS=118.11±5.00 MPa) whereas for conventional heat cure PMMA (IS=4.00±.011 kJ/m2 and FS=75.4±4.50 MPa) the values are least among the three. CONCLUSION:  PEEK or CAD/CAM PMMA share almost identical and superior mechanical properties, and both can be used as better alternatives for complete denture fabrication rather than using conventional heat cure PMMA.

Influence of denture brushing on the surface properties and color stability of CAD-CAM, thermoformed, and conventionally fabricated denture base resins.

PURPOSE: To assess the influence of denture brushing on the surface roughness, hardness, and color stability of conventional, thermoformed, and CAD-CAM denture base materials. MATERIALS AND METHODS: Seven different denture base materials were included in this study; conventional heat-polymerized acrylic resin (PMMA) served as control, polyamide, acetal, two categories of milled acrylic discs (AvaDent and IvoCad), and two categories of 3D-printed resins (NextDent and FormLabs). The specimens were constructed according to manufacturers' instructions and then subjected to simulated brushing (20,000 cycles). According to the brushing method, the specimens were split into three groups, no brushing, brushing with water, and brushing with toothpaste. Surface roughness, hardness, and color change were evaluated before and after brushing. Collected data were analyzed using ANOVA, and post-hoc Tukey's tests (α = 0.05). RESULTS: A significant difference was noted between the surface roughness of the tested materials before and after denture brushing (p < 0.05), and milled resin showed the least Ra values. Denture brushing with water significantly increased the Ra of PMMA (p = 0.004) and IvoCad (p = 0.032), while brushing using toothpaste did not show a significant increase. The brushing protocols did not alter the hardness of tested materials except that of PMMA (p = 0.001). The color stability of the tested materials showed comparable results with both brushing protocols. CONCLUSION: The tested properties showed variations between the types of denture base resins. Hardness and color stability of CAD-CAM and thermoformed denture base resins were not altered by denture brushing and showed comparable results with both brushing methods. Surface roughness was the only property that showed alteration after denture brushing.

3D-printed nanocomposite denture base resin: The effect of incorporating TiO2 nanoparticles on the growth of Candida albicans.

PURPOSE: To develop a biocompatible denture base resin/TiO2 nanocomposite material with antifungal characteristics that is suitable for 3D-printing denture bases. MATERIALS AND METHODS: TiO2 nanoparticles (NPs) with a 0.10, 0.25, 0.50, and 0.75 weight percent (wt.%) were incorporated into a commercially available 3D-printed resin material. The resulting nanocomposite material was analyzed using Lactate dehydrogenase (LDH) and AlamarBlue (AB) assays for biocompatibility testing with human gingival fibroblasts (HGF). The composite material was also tested for its antifungal efficacy against Candida albicans. Fourier transform infrared (FTIR) and Energy Dispersive X-ray Spectroscopy (EDX) mapping were conducted to assess the surface coating and the dispersion of the NPs. RESULTS: LDH and AB assays confirmed the biocompatibility of the material showing cell proliferation at a rate of nearly 100% at day 10, with a cytotoxicity of less than 13% of the cells at day 10. The concentrations of 0.10, 0.25, and 0.50 wt.% caused a significant reduction (p < 0.05) in the number of candida cells attached to the surface of the specimens (p < 0.05), while 0.75 wt.% did not show any significant difference compared to the control (no TiO2 NPs) (p > 0.05). FTIR and EDX analysis confirmed the presence of TiO2 NPs within the nanocomposite material with a homogenous dispersion for 0.10 and 0.25 wt.% groups and an aggregation of the NPs within the material at higher concentrations. CONCLUSION: The addition of TiO2 NPs into 3D-printed denture base resin proved to have an antifungal effect against Candida albicans. The resultant nanocomposite material was a biocompatible material with HGFs and was successfully used for 3D printing.

The mechanical properties of 3D printed denture base resin incorporating essential oil microcapsules.

Purpose: The aim of this study was to investigate the mechanical properties of three-dimensional (3D) printed denture base resin incorporating microcapsules containing plant essential oils. Materials and Methods: Denture base specimens containing up to 3% w/v essential oil microcapsule powders (MCPs), i.e., eucalyptus, geranium, lavender, menthol, and tea tree, in two resins (Detax and NextDent 3D+) were 3D printed using two printers (Asiga and NextDent 5100). The dispersion and interaction of the MCPs in the resin were assessed by SEM while the mechanical properties of the incorporated denture base including flexural strength (MPa), flexural modulus (MPa), Vickers hardness (VHN), and surface roughness (Ra) were also subsequently evaluated. Statistical analysis of any differences in mean values was determined using a two-way ANOVA with Tukey's post hoc testing (α = .05). Results: The spherical shape of the MCPs was maintained during the mixing and polymerization/printing process. However, the Detax-Asiga group showed significant agglomeration of the MCPs even at the lowest MCP concentration levels (0.5% w/v). Overall, as the microcapsule concentration increased, the mean flexural strength decreased, though the menthol MCP groups remained compliant with the ISO standard. The flexural modulus and harness remained relatively unchanged, and the flexural modulus complied with the ISO standard regardless of the MCP concentration. Surface roughness increased with the addition of the MCPs but also remained below that required for clinical acceptance. Conclusion: Incorporation of microencapsulated plant essential oils into 3D printed denture base resin was successfully achieved. While incorporation negatively influenced flexural strength and surface roughness, little effect on flexural modulus and Vickers hardness was demonstrated.

Flexural Properties of Heat-Polymerized PMMA Denture Base Resins Reinforced with Fibers with Different Characteristics.

Polymethylmethacrylate (PMMA) has been the most-widely used denture base material in prosthetic dentistry for the last 80 years. It is still one of the best alternatives when new methods are inapplicable. Due to the lack of some physical inadequacies occurring during cyclic use and accidental situations, various reinforcement strategies such as using nanoparticles, wires, fibers, and meshes have been investigated and reported. In this study, it was aimed to conduct a comparative investigation of the effect of fiber additives with different characteristics on the flexural properties of heat-cured PMMA denture base resins. Glass fibers (GFs), polypropylene fibers (PPFs), and carbon fibers (CFs) having 3, 6, and 12 mm lengths and 0.25, 0.50, and 1.0% concentrations (v/v) were used for the reinforcement of PMMA denture base resins. The flexural properties (flexural strength, flexural modulus, and maximum deformation) were determined using a three-point bending test, and three-way ANOVA analyses with Bonferroni corrections were performed on the test results. The morphologies of the fracture surfaces were analyzed using scanning electron microscopy. All three fibers exhibited reinforcement in the flexural strength (p < 0.001) and flexural modulus (p < 0.001) regardless of their length and concentration. The group with 1.0% 12 mm CF-reinforced PMMA exhibited the greatest flexural strength (94.8 ± 8.8 MPa), and that with 1.0% 3 mm GFs displayed the lowest flexural strength (66.9 ± 10.4 MPa) among the fiber-reinforced groups. The greatest value of the flexural modulus was displayed by the 1.0% 3 mm CF-reinforced resin (3288.3 ± 402.1 MPa). Although the CF-reinforced groups exhibited better flexural properties, CFs are not favorable for use as reinforcement in practice due to the dark gray discoloration of the denture base resin. It was concluded that PPF is a promising material for the reinforcement of heat-cured PMMA denture base resins.

Effects of Smokeless Tobacco on Color Stability and Surface Roughness of 3D-Printed, CAD/CAM-Milled, and Conventional Denture Base Materials: An In Vitro Study.

Tobacco consumption in its different forms can affect the optical and surface properties of dental materials that are used in the oral cavity. Thus, the present study was conducted to evaluate the effects of two commercially available smokeless tobacco products on the color stability and surface roughness of denture base resins that were fabricated using three different techniques (CAD/CAM milling, 3D printing, and conventional heat polymerization). A total of 126 denture base resin specimens were fabricated using the three different manufacturing techniques (n = 42 each). Specimens from each group were further subdivided into three subgroups (n = 14 each) and immersed in three different immersion media (a khaini suspension, a tabbaq suspension, and artificial saliva). The differences in color and surface roughness were assessed according to data that were collected and statistically analyzed using SPSS version 24.0. The tabbaq smokeless tobacco was found to cause greatest changes in color and surface roughness; the effect was observed to be highest in the 3D-printed specimens followed by the conventional heat-polymerized and CAD/CAM milled specimens. The mean changes in color and surface roughness were the highest for the tabbaq smokeless tobacco followed by the khaini smokeless tobacco and the artificial saliva. Statistically significant (p-value < 0.05) differences were observed among all techniques and suspensions. We concluded that the mean changes in color and surface roughness were significantly higher for the 3D-printed dentures compared to the conventional heat-polymerized and CAD/CAM-milled dentures. Thus, the results of the present study strengthened the concept that tobacco in any form can lead to changes in the color and surface roughness of denture base materials.

The stain resistant effect of an ultraviolet curable coating material on denture base resin.

This study aimed to evaluate the effects of an ultraviolet (UV) curable coating material on denture base resin. The results of the three-point bending test showed no significant difference between treated and untreated specimens, suggesting that the UV curable coating material did not compromise the physical strength of denture base resin. The surface free energy measurement and the surface analysis with atomic force microscopy revealed superhydrophilicity and a regularly arranged structure on the coating surface, improving wettability. Moreover, untreated specimens were significantly discolored in the staining test. However, specimens treated with the UV curable coating material showed no significant difference in color with slight staining, suggesting excellent antifouling ability. Therefore, the UV curable coating material used in this study could contribute to simplifying hygiene without altering the physical properties of denture base resins.

Chemical characterization of silanized silver nanoparticles impregnated in poly (methyl methacrylate) resin: An in vitro study.

Aim: The intention was to determine the chemical interaction of silanized AgNPs with PMMA by Fourier transform infrared (FTIR) spectroscopy. Settings and Design: In-vitro comparative study. Materials and Methods: This study is composed of four groups - 0.75% AgNP, 1.0% AgNP, 1.5% AgNP impregnated with PMMA, and nonimpregnated PMMA as control. The chemical nature of silanized AgNPs was studied using FTIR study. Results: The results showed the appearance of new peak between 1727/cm and 1436/cm, i.e., 1636.476/ cm, 1645.886/cm, and 1646.885/cm, representing the C = C stretch in the experimental groups, i.e., 2, 3, and 4, respectively. This peak confirms that coupling agent has chemically interacted with PMMA. Conclusion: It can be concluded that the AgNPs coated with the silane coupling agent TMSPM has chemically reacted with PMMA.

Water sorption, water solubility, degree of conversion, elastic indentation modulus, edge chipping resistance and flexural strength of 3D-printed denture base resins.

OBJECTIVES: To investigate the water sorption (wsp), water solubility (wsl), degree of conversion (DC), elastic indentation modulus (EIT), edge chipping resistance (ECR) and flexural strength (FS) of 3D-printed, milled and conventionally polymerized denture base resin materials. METHODS: Specimens (N = 540) were 3D-printed (NextDent Denture 3D+ (DEN), Fotodent Denture (FOT), Freeprint Denture (FRE), V-Print dentbase (VPR)), cut (Ivotion Base (IVO)) and molded (PalaXpress (PAL)) in three geometries. Wsp,wsl,DC, EIT, ECR and FS were tested initially (24 h, 37 °C, H20) and after additional aging (5000 thermal cycles, 5/55 °C). Data were analyzed with Kolmogorov-Smirnov, univariate ANOVA, Kruskal-Wallis, Mann-Whitney U test and Spearman's correlation (p < 0.05) RESULTS: Most 3D-printed denture base resins showed higher wsp (25.31-37.94 µg/mm3) and wsl (0.08-8.27 µg/mm3), but also higher EIT (3.11-4.09 GPa) and FS (60.81-99.57N/mm2) values than the control groups. DEN and VPR showed high DC (89.36-93.53%), EIT (3.77-4.09 GPa) and FS (79.65-99.57N/mm2), while FOT showed low wsp (25.31-27.35 µg/mm3) and wsl (1.01-3.87 µg/mm3) values. In all materials, the examined parameters were affected by aging. SIGNIFICANCE: Although 3D-printed denture base resins showed promising results with regard to the observed DC and FS, only FOT and FRE surpassed the threshold values defined by the ISO norms.

Flexural Properties and Hardness of CAD-CAM Denture Base Materials.

PURPOSE: To compare flexural strength, elastic modulus, and surface hardness of computer aided design and computer aided manufacturing CAD-CAM milled, 3D-printed, and heat-polymerized denture base resins. MATERIALS AND METHODS: A total of 120 specimens were fabricated from heat-polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D-printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material (n = 20/material) (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3-point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795-1:2013 standards (64 × 10 × 3.3 ± 0.2 mm). The dimensions for hardness test were 15 × 10 × 2.5 ± 0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one-way ANOVA and Tukey post-hoc test (α = 0.05). RESULTS: Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP and then 3D-printed resins (p < 0.001). Within milled groups, flexural strength of AvaDent was significantly higher than IvoCad (p < 0.001), while elastic modulus and hardness didn't show significant difference. Within 3D-printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (p = 0.595) and significantly with NextDent (p = 0.008). ASIGA also showed significantly the highest hardness among the 3D-printed groups. No significant difference was found between FormLabs and NextDent in flexural strength (p = 0.357), elastic modulus (p = 1.00), or surface hardness (p = 0.987). CONCLUSION: CAD-CAM milled resins had greater flexural properties and hardness compared to heat-polymerized acrylic resin and 3D-printed resins. Although 3D-printed samples showed the lowest values of tested properties, the flexural strength and modulus were above clinically acceptable values.

Effect of Denture Cleanser on the Physico-Mechanical Properties of Injection-Molded Thermoplastic Polyamides Denture Base Material: A preliminary Study.

Objectives: This study aimed to assess the color stability, surface roughness, and flexural properties of the injection-molded thermoplastic polyamide Vertex ThermoSens denture base resin following a 3-minute immersion in Polident 3-minute denture cleanser. Methods: Sixty specimens (Vertex ThermoSens) were processed and divided into two main groups (n = 30) based on the type of test. Group 1 was further subdivided into two subgroups (n = 15): the control group immersed in distilled water (G1DW) and the test group immersed in Polident cleanser solution (G1PD). Group 2 was divided into three subgroups: a non-immersed group (G2None), a group immersed in distilled water (G2DW), and a group immersed in Polident cleanser solution (G2PD). Color change (∆E) and surface roughness measurements were conducted for group 1, and flexural modulus (E) test was performed for group 2. The CIE Lab* formula was utilized to calculate ∆E. An optical 3D surface analyzer and a three-point bending test were employed for surface roughness and E assessments, respectively. Data were subjected to statistical analysis using a paired-sample t-test for differences within each group before and after immersion. Furthermore, independent-sample t-tests and one-way ANOVA were conducted to analyze differences between groups. A significance level of P < 0.05 was considered. Results: The results revealed a slight, statistically insignificant (P > 0.05) ∆E in all color components (L*, a*, b*) after immersion in distilled water. However, after immersion in the denture cleanser, only the L* component exhibited a statistically significant ∆E (P = 0.002), which was slight in magnitude. Additionally, a significant difference was found in the ∆E between G1DW and G1PD, with G1PD showing a higher change (P = 0.007). A significant increase in surface roughness after immersion was observed in G1PD (P = 0.017), with a notable difference between G1DW and G1PD. However, the E remained unaffected (P = 0.537). Conclusion: Denture cleansers have the potential to modify the properties of thermoplastic polyamide resin. Further research is needed to explore the clinical implications of these observed changes on denture performance.

Assessment of Tensile Bond Strength of a Soft Liner to the Denture Base Resin with Different Surface Treatments: An In Vitro Study.

AIM: The aim of the current research was to evaluate the tensile bond strength of a soft liner to the denture base resin with different surface management techniques. MATERIALS AND METHODS: Dies made up of stainless steel and having dimensions of 40 × 10 × 10 were used to fabricate polymethyl-methacrylate resinous blocks. To make sure of the regularity of the soft liner in the test, dies made up of stainless steel and having dimensions of 10 × 10 × 3 were fabricated to serve as spacers. These acrylic resinous blocks were allocated to three groups depending upon the particular surface management technique as: group I-Absence of surface treatment (Control), group II-Surface management with methyl methacrylate (MMA) monomer, and group III-Surface management with Phosphoric acid. All the samples underwent thermocycling at 5° centigrade and 55° centigrade in two water baths for 500 cycles at a dwell tenure of 30 seconds in every bath to reproduce the oral circumstances. The samples were then subjected to testing in the universal testing machine for evaluation of the tensile strength. RESULTS: The highest tensile strength was noted in the soft liner with denture base resin that was subjected to treatment with a monomer having a mean score of 1.88 ± 0.11 in pursuit by surface management using phosphoric acid at 1.16 ± 0.90 as well as the control group at 0.94 ± 0.02 in that order. There was a statistically noteworthy disparity amid the three dissimilar surface management techniques with a p-value <0.001. There was a statistically noteworthy differentiation amid group I vs group II as well as group II vs group III with a p-value <0.001. However, there was no statistically significant disparity amid group I vs group III with p-value >0.001. CONCLUSION: The current research arrived at the conclusion that the samples subjected to treatment with MMA monomer exhibited higher and noteworthy bond strength than those attained by additional surface management techniques for soft lining of the denture base resins. CLINICAL SIGNIFICANCE: Soft denture lining materials play a pivotal position in contemporary prosthodontic practice as they possess the ability to restore the health of swollen as well as deformed mucosal tissues. They are comfortable in those individuals who are unable to endure pressure from occlusal forces, like in a situation of residual ridge resorption, sore tissues, and ridges that attain a knife-edge shape. Failing bond causes delamination of the reliner and therefore lack of adaptability of the denture to the oral mucosal tissues. For this reason, superior bonding to the denture base beneath is critical for the clinical triumph of relining agents.