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Purpose: To evaluate the effect of chemical, mechanical, and combination surface treatments on the shear bond strength (SBS) of autopolymerizing repair resin to conventional heat-cured, computer aided design (CAD)-computer aided manufacturing (CAM) milled, and three-dimensionally (3D) printed denture base materials., Methods: Specimens were fabricated and divided according to the surface treatment as follows: no surface treatment (control group), monomer treatment (monomer group), resin remover treatment (resin remover group), roughening with 180 FEPA grit abrasive paper followed by monomer treatment (180-grit plus monomer group), and air particle abrasion (air abrasion group). Autopolymerizing resin cylinders were attached before accelerated aging of the specimens in water at 100 °C for 16 h. The SBS was tested using a universal testing machine. Surface roughness was evaluated using a 3D optical profilometer. Scanning electron microscopy (SEM) and stereomicroscopy were used for surface analysis. Data was collected and analyzed using analysis of variance (ANOVA) and Kruskall-Wallis tests (α = 0.05)., Results: The denture base material and surface treatment significantly affected the SBS. The milled Temp Basic Tissue demonstrated the highest SBS values across all surface treatments, whereas the two 3D-printed denture base materials exhibited the lowest SBS values., Conclusions: The bond strength of CAD-CAM-milled denture base resins to autopolymerizing repair resin is comparable to that of heat-cured resins. Surface roughening using air particle abrasion or 180-grit carbide paper can enhance the bond strength of the autopolymerizing repair resin to 3D-printed denture base materials.

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., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Statement of Problem: Denture bases machined from prepolymerized materials have become popular. However, information on the effect of simulated brushing and coffee thermocycling (CTC) on their surface roughness and stainability is lacking., Purpose: The purpose of this in vitro study was to compare the effect of simulated brushing and CTC on the surface roughness (R a ) and stainability of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials and a heat-polymerized denture base material., Material and Methods: Forty disk-shaped specimens were prepared from 3 CAD-CAM denture base resins (AvaDent, AV; Merz M-PM, M-PM; and Polident d.o.o, Poli) and a heat-polymerized polymethylmethacrylate resin (Promolux, CV) (n=10). R a values of the specimens were measured by using a noncontact profilometer after conventional polishing. The color coordinates were also measured over a gray background with a spectrophotometer. Specimens were then consecutively subjected to simulated brushing for 20 000 cycles, CTC for 5000 cycles, and another 10 000 brushing cycles. R a and color coordinates were measured after each interval. Color differences (ΔE 00 ) were calculated by using the CIEDE2000 formula, and the data were analyzed by using 2-way analysis of variance and Tukey honestly significant difference tests (α=0.05)., Results: The time interval had a significant effect on R a (P<.001) as brushing cycles resulted in higher values than those at baseline and after CTC (P<.001). However, the differences between brushing cycles (P=.143) and between the baseline and after CTC (P=.994) were not significant. The interaction between the material type and time interval was significant for ΔE 00 (P=.016). The only significant difference in ΔE 00 values was observed between M-PM and CV after all treatments were completed (P=.029)., Conclusions: Brushing increased the R a of all materials when compared with the baseline. All materials showed similar stainability throughout the brushing and CTC processes. However, M-PM CAD-CAM denture base resin underwent a greater color change after all treatments were completed than conventional denture base resin. All color changes can be considered clinically small, considering reported perceptibility and acceptability thresholds., (Copyright © 2022 Editorial Council for The Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objectives: This study aimed to compare the physical and mechanical properties of four denture base materials: Polyan IC (PA), milled polymethylmethacrylate (PMMA), three-dimensional (3D)-printed resin (3DP), and SR Ivocap (SR)., Methods: Ninety-six samples were prepared and divided into four groups as follows. Group A consisted of 3DP (Asiga DentaBASE, Asiga) fabricated using a manufacturer-recommended 3D printer (Asiga Pro 4k, Asiga). Group B comprised milled PMMA (MP) (Ivotion Base, Ivoclar Vivadent). Group C included PA (BredentSenden), meanwhile, group D involved SR (Ivoclar VivadentSchaan). Cuboid samples (65 mm x 10 mm x 2.5 mm) were used for biaxial flexure strength testing in a universal testing machine (UTM). Cylindrical samples of 20 mm x 40 mm were used for compressive strength testing in a UTM. Additionally, cuboid samples (65 mm x 10 mm x 2.5 mm) were used for Vickers surface hardness testing in a microhardness tester. disk samples (10 mm x 2.5 mm) were employed for color stability testing both in a coffee solution and Coca-Cola, using a digital spectrophotometer. Statistical analyses were performed using one-way analysis of variance and Tukey's post hoc analysis (α=0.05)., Results: MP demonstrated superior compressive strength (p = 0.002) and color stability compared to that exhibited by 3DP (p < 0.001) while displaying similar flexure strength (p = 0.336) and hardness (p = 0.708). MP and PA displayed similar compressive strength (p = 0.081), flexure strength (p = 0.159), and color stability in coke (p = 0.071). However, MP had reduced hardness (p < 0.001) and color stability in coffee (p < 0.001). Moreover, MP demonstrated a higher compressive strength (p < 0.001) than that displayed by SR. However, the flexure strength, hardness, and color stability were similar (p > 0.05). Furthermore, 3DP exhibited comparable compressive strength (p = 0.334) to that of PA but demonstrated significantly lower flexure strength (p = 0.005), hardness (p < 0.001), and color stability (p < 0.001) compared to PA. In comparison to SR, PA had a higher compressive strength (p < 0.001), hardness (p = 0.001), and color stability in coffee (p < 0.001), although they demonstrated similar (p > 0.05) flexure strength and color stability in coke., Conclusions: The MP and PA demonstrated superior compressive strength than that exhibited by the other materials tested. The tested materials had similar flexure strengths, except for PA which demonstrated superiority over the 3DP. Among all tested materials, PA exhibited the highest hardness, while the 3DP was the least color-stable., Clinical Significance: Considering the mechanical properties and color stability, Polyan and milled polymethylmethacrylate are preferred for complete denture fabrication. However, the limited repairability and complex handling of Polyan should be considered., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Aim: This study aimed to evaluate the effect of adding different concentrations of silver nanoparticles (AgNPs) on the flexural strength and microhardness of various denture base materials., Materials and Methods: For this study, a total of 60 specimens were used and divided into equal groups. The first group consisted of heat-cured acrylic resin (Vertex-Germany), while the second group consisted of thermoplastic resin (Breflex 2nd edition, Germany). The samples were created using a split brass mold with dimensions of 65 × 10 × 2.5 mm, in accordance with the specifications of the American Dental Association (specifically No. 12 for flexural and microhardness). Following this, the samples were divided into three groups (A, B, and C) based on different concentrations of AgNPs (0, 2, and 5%). The flexural and microhardness of the samples were assessed using a universal testing machine and the Vickers hardness test, respectively. The data were gathered, organized, and analyzed using statistical methods., Results: The flexural strength findings showed a significant difference between the two groups. Also, there was a considerable decrease in the average value of the acrylic group as the concentrations of AgNPs rose, while the flexural strength of the thermoplastic group notably improved. Regarding microhardness, the results showed a significant difference between the two groups. It showed that the mean value of both groups increased with increasing concentrations of AgNPs., Conclusion: Within the limitations of laboratory testing conditions of this study, it was discovered that AgNPs negatively impact the flexural strength of acrylic resins. Furthermore, an increase in the concentration of AgNPs was found to be directly related to the flexural strength of thermoplastic resin and the microhardness of both groups., Clinical Significance: The concentration of AgNPs has a significant impact on certain mechanical properties of denture base materials, but it is important to consider their potential toxicity. How to cite this article: El-Hussein IG. Effect of Adding Different Concentrations of Silver Nanoparticles on Flexural Strength and Microhardness of Different Denture Base Materials. J Contemp Dent Pract 2024;25(5):417-423.

Purpose: To evaluate the flexural properties of repaired poly(methylmethacrylate) (PMMA) denture base materials for computer-aided design/computer-aided manufacturing (CAD-CAM) and to compare them with heat-activated polymerized PMMA., Methods: A total of 288 specimens (65 × 10 × 2.5 mm) were prepared using both CAD-CAM and conventional blocks and repaired using autopolymerizing and visible-light polymerizing (VLC) materials. Microwave energy, water storage and hydroflask polymerization were applied as additional post-polymerization cycles after the repair process. The flexural strength (FS) of the specimens was evaluated using the three-point bending test. Data were evaluated statistically using 2-way ANOVA followed by Bonferroni's correction to determine the significance of differences between the groups (P ≤ 0.05)., Results: The FS of the denture base materials for CAD-CAM was significantly higher than that for the heat-activated group (P ≤ 0.05). The FS was significantly highest when microwave energy was used for the post-polymerization cycle. The FS values for all groups repaired with VLC resin were significantly lower than for the autopolymerization group (P ≤ 0.05)., Conclusion: The flexural properties of denture base materials for CAD-CAM repaired using autopolymerizing acrylic resins can recover by 50-70%. Additional post-polymerization cycles for autopolymerizing repair resin can be suggested to improve the clinical service properties of repaired dentures.

Objective: This study aims to investigate the influence of post-polymerization (post-curing) conditions on surface characteristics, flexural properties, water sorption and solubility, and cytotoxicity of additively manufactured denture base materials., Methods: The tested specimens were additively manufactured using digital light processing and classified into different post-curing condition groups: submerged in water (WAT), submerged in glycerin (GLY), and air exposure (AIR). An uncured specimen (UNC) was used as a control. The surface topography and roughness were observed. The flexural strength and modulus were determined via a three-point bending test. The water sorption and solubility were subsequently tested. Finally, an extract test was performed to assess cytotoxicity., Results: Different post-curing conditions had no significant effects on the surface topography and roughness (Sa value). Various post-curing conditions also had no significant effects on the flexural strength. Notably, the flexural modulus of the WAT group (2671.80 ± 139.42 MPa) was significantly higher than the AIR group (2197.47 ± 197.93 MPa, p = 0.0103). After different post-curing conditions, the water sorption and solubility of the specimens met the ISO standards. Finally, all post-curing conditions effectively reduced cytotoxic effects., Significances: Post-curing with different oxygen levels improved flexural properties, and flexural modulus significantly increased after the specimens were submerged in water. In addition, water sorption and solubility, and cytocompatibility were optimized by post-curing, irrespective of the post-curing conditions. Therefore, the water-submerged conditions optimized the flexural modulus of the 3D-printed denture base materials., (Copyright © 2024. Published by Elsevier Inc.)

Purpose: To evaluate relevant material properties (flexural strength [σf], elastic modulus [E], water sorption [Wsp] and solubility [Wsl], and biocompatibility) of an additive manufacturing (AM) polymer vs a heat-curing acrylic resin (AR; control) for the manufacture of complete dentures, testing the hypothesis that fabrications from both materials would present acceptable material properties for clinical use., Materials and Methods: The σf, E, Wsp, and Wsl were evaluated according to the ISO 20795-1:2013 standard, and the biocompatibility was evaluated using MTT and SRB assays. Disk-shaped specimens were fabricated and used for Wsp (n = 5), Wsl (n = 5), and biocompatibility (n = 3) testing. For assessment of σf and E, bar-shaped specimens (n = 30) were fabricated and stored in 37°C distilled water for 48 hours or 6 months before flexural testing in a universal testing machine with a constant displacement rate (5 ± 1 mm/minute). Data from σf, E, Wsp, Wsl, and biocompatibility tests were statistically analyzed using Student t test (α = .05). Weibull analysis was also used for σf and E data., Results: Significant differences between the two materials were found for the evaluated material properties. Water storage for 6 months did not affect the flexural strength of the AM polymer, but this material showed inadequate σf and Wsl values., Conclusions: Despite adequate biocompatibility and strength stability after 6 months of water storage, the AM polymer recommended for complete dentures needs further development to improve the material properties evaluated in this study.

Purpose: To investigate the influence of reducing material thickness on flexural properties of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base resins., Materials and Methods: Four CAD-CAM denture base acrylic resin materials were selected; two were made via the subtractive method (AvaDent and IvoCad) and two were made with the additive method (FormLabs and NextDent). One heat-polymerized denture base material was used as a control. Specimens were fabricated with varying thicknesses (n = 10/group): 3.3 mm, 2.5 mm, 2 mm, or 1.5 mm. Flexural strength was evaluated via a three-point bending test. One- and two-way ANOVA were used for data analysis along with Tukey's post hoc comparison (α = 0.05)., Results: Reducing the thickness of materials made via the subtractive method did not influence flexural strength up to 2 mm (p > 0.05). However, the difference was significant at a 1.5 mm thickness (p ˂ 0.001). For materials made via the additive method, NextDent specimens had no significant decrease in flexural strength when the thickness was reduced to 2 mm (p = 0.58). FormLabs specimens showed a significant decrease (p ˂ 0.001), although the values of flexural strength were clinically acceptable. During testing, specimens manufactured via the additive method at a 1.5 mm thickness bent without fracturing and were therefore excluded. All materials showed a reduction in elastic modulus as the thickness decreased (p ˂ 0.001)., Conclusion: Heat-polymerized, AvaDent, and IvoCad materials may be used for denture base fabrication at a minimum thickness of 1.5 mm. FormLabs and NextDent may be fabricated at a 2 mm minimum thickness, with clinically acceptable flexural properties., (© 2022 by the American College of Prosthodontists.)

Objective: Three-dimensional (3D) printing is increasingly being utilised in the dental field because of its time-saving potential and cost effectiveness. It enables dental practitioners to eliminate several fabrication steps, achieve higher precision, and attain consistency in complex prosthetic models. The properties of 3D-printed resin materials can be affected by many factors, including the printing orientation (PO) and insufficient post-curing time (CT). This study aimed to investigate the effect of PO and CT on the mechanical and physical properties of a 3D-printed denture base resin (NextDent)., Methods: 3D-printed specimens were fabricated in 0°, 45°, and 90° POs, followed by three CTs (20, 30, and 50 min). The microhardness was tested using a Vickers hardness test, while the flexural property was evaluated using a three-point bending test. Sorption and solubility were measured after the specimens had been stored in an artificial saliva for 42 days, and the degree of conversion during polymerisation was analysed using Fourier Transform Infra-red (FTIR) spectroscopy., Results: The flexural strength of the material significantly increased (p < 0.05) when the printing orientation was changed from 0° to 90°. A similar increase was observed in the hardness, degree of conversion, and water sorption results. In general, no significant difference (p > 0.05) in any of the tested properties was found when the post-curing times were increased from 20 to 50 min., Significance: The highest physical and mechanical properties of the 3D-printed denture base resin can be obtained by printing vertically (90° angle to the platform base). The minimal post-curing time to achieve ideal results is 30 min, as further curing will have no significant effect on the properties of the material., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: Printing orientation is an important decision in the initial steps of additive manufacturing, affecting printing accuracy and the mechanical properties of printed products. In addition, printing orientation determines the building direction of layers and the layer-by-layer configuration forming the surface geometry., Purpose: The purpose of this in vitro study was to evaluate the effect of printing orientation on the printing accuracy, flexural strength, surface characteristics, and microbial response of 3D-printed denture base resin., Material and Methods: Specimens were printed with denture base polymethyl methacrylate (PMMA) in 3 printing orientations (0, 45, and 90 degrees). The printing error rate, flexural strength, roughness, hydrophilicity, surface energy, and response to Candida albicans (C. albicans) were evaluated., Results: Specimens printed at a 90-degree orientation showed the lowest error rates for length (P<.001), and those printed at a 45-degree orientation showed statistically higher error rates for thickness than those of other groups (P<.001). Flexural strength increased in order of the specimens printed at orientation degrees of 90<45<0 with statistical significance. The 45-degree oriented specimens showed higher roughness and surface energy than those of other groups (P<.001). A higher proportion of C. albicans was found in the specimens printed at orientation degrees of 90<45<0 with statistical significance., Conclusions: Printing orientation significantly influenced the printing accuracy, flexural strength, roughness, and response to C. albicans. Therefore, the printing orientation should be carefully decided to fabricate products with appropriate properties., (Copyright © 2019 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: To compare the antifungal action of two commercially available denture cleaning agents to that of standard clinical solutions, and determine their effects on the polymethyl methacrylate (PMMA) acrylic resin denture surface., Methods: Candida albicans growth was analyzed by colony forming assay, and the methyl thiazolyl tetrazolium (MTT) assay was used to evaluate biofilm formation and cell adhesion. The morphology and roughness of PMMA acrylic resin surface was measured by scanning electron microscopy (SEM) images and stylus method., Results: Clene®, Polident® and 3% NaHCO 3 solutions showed significantly greater antifungal effects in terms of both inhibiting growth and biofilm formation. In addition, Clene® solution prevented adhesion of C. albicans on cell culture plates compared to filter-sterile tap water, whereas other reagents did not have an inhibitory effect. One-month immersion in the different cleaning reagents significantly inhibited fungal adhesion on the PMMA surface Clene®, Polident® and 3% NaHCO 3 showed greater effect compared to PBS and filter-sterile tap water. Finally, none of the cleansing agents significantly affected the morphology and roughness of the PMMA surface., Conclusion: Clene®, Polident® and 3% NaHCO 3 solutions can inhibit C. albicans growth and biofilm formation to some extent on cell culture plates, and significantly inhibit fungal adhesion on the PMMA surface without affecting surface morphology and roughness.

Background: Denture hygiene is an important factor to remove dental plaque and discoloration, to provide optimal oral health, and to prevent denture stomatitis., Aim: The purpose of this study was to evaluate the effect of coffee staining and denture cleaner on the color stability of two differently polymerized (heat and microwave) denture acrylic resin in vitro., Materials and Methods: Two commonly used denture base acrylic resins and effervesecnt tablet form denture cleaner were used in this study. Disc-shaped specimens from each acrylic resin were polymerized according to the manufacturer's instructions (n = 7). Color values were recorded before and after immersion in distilled water (I), denture cleaner (II), coffee (III), and coffee + denture cleaner (IV) with a tristimulus colorimeter using CIEDE2000 color difference formula. Two-way analysis of variance (ANOVA) and Fisher's least significant difference tests were used for multiple comparisons at a 95% confidence level (P < 0.05). Surface topography of the acrylic resin denture base specimens before and after immersion were taken under 500 × magnification., Results: The two-way ANOVA revealed significant interactions between denture base resins and solutions (P < 0.001). Immersion in denture cleaner and coffee solution caused significant color changes in acrylic resin denture bases., Conclusion: Heat- and microwave-polymerized acrylic denture base resins can show different color stability. Immersion in coffee and denture cleaner solutions can cause noticeable color changes., Competing Interests: None

The aim of this study was to investigate the effect of double-modified organoclay on mechanical properties of polymethylmethacrylate (PMMA) denture base resins. An organoclay was further modified via a silanization process using 3-trimethoxysilylpropyl methacrylate (MPS) as a reactive silane coupling agent. X-ray diffraction patterns (XRD), thermogravimetric analysis (TGA), and Fourier-transform infrared spectroscopy (FTIR) confirmed the presence of MPS in the resulting double-modified nanoclay structure. Surface tension of the original and double-modified nanoclays, were determined using contact angle measurements. Results showed that double-modified nanoclay has more organophilic nature due to silanization of the clay edges. Free radical suspension polymerization of methylmethacrylate monomers in the presence of different amounts of double-modified organoclay was performed and PMMA/clay nanocomposites were obtained. Results of dynamic mechanical thermal analysis (DMTA) showed increased storage modulus and glass transition temperature for the resulting nanocomposites with respect to neat PMMA. Higher improvements in storage modulus and glass transition temperature were obtained for nanocomposites containing 0.25 and 0.5 wt% of double-modified nanoclay. TEM observations of the nanocomposite containing 0.5 wt% of double-modified nanoclay showed prevailing exfoliated morphology. Aforementioned nanocomposites with higher mechanical properties were incorporated into a denture base formulation and their mechanical properties were studied using static flexural and fracture toughness tests. According to the results, both reinforced samples showed increased flexural strength, flexural modulus and fracture toughness in comparison to the neat matrix. The average improvements in flexural strength, flexural modulus and fracture toughness were about 30%, 65.8% and 32%, respectively. Scanning electron microscopy (SEM) images of the fracture surface of the resin matrices subjected to static tests showed brittle and ductile surface fracture for neat and reinforced denture base specimens, respectively., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objectives: Resin polymerisation shrinkage reduces the congruence of the denture base with denture-bearing tissues and thereby decreases the retention of conventionally fabricated dentures. CAD/CAM denture manufacturing is a subtractive process, and polymerisation shrinkage is not an issue anymore. Therefore, CAD/CAM dentures are assumed to show a higher denture base congruence than conventionally fabricated dentures. It has been the aim of this study to test this hypothesis., Materials and Methods: CAD/CAM dentures provided by four different manufacturers (AvaDent, Merz Dental, Whole You, Wieland/Ivoclar) were generated from ten different master casts. Ten conventional dentures (pack and press, long-term heat polymerisation) made from the same master casts served as control group. The master casts and all denture bases were scanned and matched digitally. The absolute incongruences were measured using a 2-mm mesh., Results: Conventionally fabricated dentures showed a mean deviation of 0.105 mm, SD = 0.019 from the master cast. All CAD/CAM dentures showed lower mean incongruences. From all CAD/CAM dentures, AvaDent Digital Dentures showed the highest congruence with the master cast surface with a mean deviation of 0.058 mm, SD = 0.005. Wieland Digital Dentures showed a mean deviation of 0.068 mm, SD = 0.005, Whole You Nexteeth prostheses showed a mean deviation of 0.074 mm, SD = 0.011 and Baltic Denture System prostheses showed a mean deviation of 0.086 mm, SD = 0.012., Conclusions: CAD/CAM produces dentures with better fit than conventional dentures., Clinical Relevance: The present study explains the clinically observed enhanced retention and lower traumatic ulcer-frequency in CAD/CAM dentures.

Purpose: The aim of this study was to investigate the effect of gold nanoparticle on the flexural strength of polymethyl methacrylate (PMMA)., Materials and Methods: PMMA specimens (65 mm × 10 mm × 3.3 mm) containing different sizes (45 nm, 55 nm, and 65 nm) and concentrations (0.05% and 0.2%) of gold nanoparticles were prepared, along with a control group containing no added nanoparticles. Flexural strength of all specimens was measured, and one-way ANOVA and Tukey-Kramer post hoc multiple comparisons tests were performed to identify statistical differences between groups., Results: The addition of gold nanoparticles increased the flexural strength of acrylic resin. Significantly greater increases were obtained with lower concentrations (0.05%) when compared to higher concentrations (0.20%)., Conclusion: Differences in concentrations of gold nanoparticles added to PMMA have significantly different effects on PMMA flexural strength, whereas differences in sizes of gold nanoparticles added to PMMA do not significantly affect its flexural strength. Accordingly, adding gold nanoparticles to PMMA may enhance the mechanical properties of denture bases used in clinical practice., Competing Interests: There are no conflicts of interest

Context: Pink colored acrylic does not always satisfactorily replicate the natural gingival color, especially in individuals with pigmented mucosa. In such situation clear acrylic denture base material can be used. Hence, there is a need of a comparative study of the mechanical properties of the clear and pink colored denture base resins., Aims: The aim of this study is to compare the mechanical properties, i.e., tensile, flexural, compressive, and impact strength (IS) of clear and pink colored denture base resins., Settings and Design: This was comparative in vitro study., Materials and Methods: A total of 80 specimens were divided into two groups of 40 specimens each of clear and pink colored acrylic resin. Specimens for testing flexural, tensile, compressive, and ISs of acrylic resin (10 in each group) were divided. A universal testing machine was used for measuring flexural, tensile, and compressive strength (CS) while the Izod/Charpy impact tester was used for IS., Results: The mean tensile strength for clear resin (n = 10) was 30.90 ± 1.663 MPa and that for pink resin (n = 10) was 31.30 ± 8.166 MPa. The mean residual flexural strength for clear resin (n = 10) was 75.60 ± 17.212 MPa, whereas for pink resin (n = 10) was 76.10 ± 14.130 MPa. The mean CS for clear resin (n = 10) was 84.60 ± 2.503 MPa and for pink resin (n = 10) was 85.40 ± 16.222 MPa. The mean IS for clear resin (n = 10) was 11.50 ± 5.104 MPa. While for pink resin (n = 10) was 11.90 ± 1.370 MPa., Conclusions: The results show that clear acrylic resin denture base material has mechanical properties similar to that of pink acrylic resin denture base material., Competing Interests: None

Aim: To Compare and Evaluate the Flexural Strength and Surface Roughness of Lucitone-FRS, Valplast (Flexible Denture Base Materials) and Trevalon (Heat Cure Denture Base Material)., Materials and Methods: Three stainless steel master dies of dimension 65 × 20 × 3 mm were fabricated and were invested in standard metal denture flask. A total of 60 specimens were fabricated with 20 specimens of each type of denture base material. Fabrication of a Heat Cure Acrylic Denture Base Resin Specimen was Done Followed by Fabrication of Flexible Denture Base Resins Specimen. In the same manner, samples were fabricated for Lucitone-FRS, and Valplast. These specimens were further divided into two subsets; containing 10 specimens each from each group. In one subset, Flexural Strength was Measured while in the other subset, Surface Roughness was measured. The Surface Roughness values were measured using a surface testing machine Mitutoyo-SJ-Series 201 (Japan). The flexural strength of specimens was measured using a 3-point bending test device on universal testing machine. All the results were compiled and Analyzed by SPSS software., Results: Flexural strength was found maximum in the VALPLAST and minimum in LUCITONE. Surface Roughness Test was done on total 10 samples of each material, i.e. Lucitone-FRS, Valplast and Trevalon. Results for Surface Roughness Test are Valplast has maximum Surface-Roughness followed by Trevalon and minimum in Lucitone-FRS on both polished and unpolished surface., Conclusion: Trevalon can be ideal in cross-arch stabilization cases and Valplast and Lucitone FRS can be successfully used in cases of small arch complete dentures and removable partial dentures., Clinical Significance: The selection of the right denture base material is imperative as it largely affects the overall clinical outcomes and comforts. Results of the present study would aid the dentist in the selection of ideal denture base materials for specific cases like those requiring Cross Arch Stabilization, Small Arch Complete Dentures, and Removable Partial D entures.

The current study evaluated the effects of autoclave polymerization both with and without glass fiber (GF) reinforcement on the surface roughness and hardness of acrylic denture base material. Ninety disc specimens (30×2.5 mm) were prepared from Vertex resin and divided according to polymerization techniques into a water bath, short and long autoclave polymerization groups. Tested groups were divided into three subgroups according to the GF concentration (0, 2.5, and 5 wt%). Profilometer and Vickers hardness tests were performed to measure surface roughness and hardness. ANOVA and Tukey-Kramer multiple comparison tests analyzed the results, and p≤0.05 was considered statistically significant. Autoclave polymerization significantly decreased the surface roughness and increased the hardness of acrylic resin without GF reinforcement (p<0.05). However, 5 wt% GF addition significantly increased surface roughness and decreased hardness of the autoclave polymerized denture base resin (p<0.05). Surface properties of Polymethyl methacrylate (PMMA) denture base material improved with autoclave polymerization and negatively affected with GFs addition.

Background: Maintaining the oral hygiene of denture wearers is a challenge faced in modern dentistry. Biofilm formed on dentures has been associated with denture stomatitis, malodor, aspiration pneumonia, infectious endocarditis, gastrointestinal infection, and chronic obstructive pulmonary disease., Objective: The purpose of this study was to evaluate the effect of denture cleansers on the surface roughness of hard denture base material., Materials and Methods: A total of 100 heat-cure acrylic resin specimens were fabricated with dimensions 30 mm × 15 mm × 3 mm in length, width, and thickness, respectively. All specimens were distributed into four groups randomly. Three commonly prescribed denture cleansers were used for immersion in this study. Regular tap water was used for immersion in the control group. Surface roughness was determined before immersion and after immersion in denture cleansing solutions using contact profilometer. The data were subjected to statistical analysis using paired t-test, one-way analysis of variance, and Tukey's multiple post hoc test., Results: The change in surface roughness of acrylic samples immersed in Clanden group was statistically significant (P < 0.05) at individual group level. However, the change in surface roughness of acrylic samples after immersion, when compared between the groups, namely, control, Clinsodent, Clanden, and Fittydent, was not statistically significant (P > 0.05)., Conclusion: Within the limitation of this study, the three denture cleansing materials, namely, Clinsodent powder, Clanden tablet, and Fittydent tablet, are safe to be prescribed as denture cleansers., Competing Interests: There are no conflicts of interest

Purpose: The aim of the present investigation was to evaluate the effect of autoclave polymerization method on the mechanical and dynamic mechanical properties of different polymethylmethacrylate denture base materials., Materials and Methods: Three different denture materials were used during the study, two of them were heat polymerizable denture base material (Meliodent and Paladent) and one was microwave polymerizable denture base material (Acron MC). Duncan test was used for the statistical analysis. Statistical analyses were completed using a two-way analysis of variance. Statistical analysis of test results was carried out with a 95% confidence level., Results: Tensile strength was increased with autoclave polymerization regardless of the denture base material type. Paladent specimens with autoclave polymerization (30 min at 60°C and 10 min at 130°C) have the highest average impact strength value. Acron MC specimens have the highest average flexural strength and modulus. Flexural strength improved with autoclave polymerization for both of 10 and 20 min polymerizations for each of Meliodent and Paladent specimens., Conclusions: Autoclave polymerization provided higher polymerization temperatures compared with the conventional heat polymerization. Autoclave-polymerized acrylic resin specimens showed higher tensile strength values; however, this was not the case for the impact test results. Flexural strength of specimens was improved with autoclave polymerization. Glass transition temperature was increased with autoclave polymerization., Competing Interests: There are no conflicts of interest

Statement of Problem: Denture tooth fracture may limit the longevity of dental prostheses. Whether the strength of the denture tooth material is affected by the denture processing technique is unclear., Purpose: The purpose of this in vitro study was to investigate whether the denture processing technique affects the mechanical properties of denture tooth materials., Material and Methods: Two denture processing techniques, injection and compression molding, were tested for 3 types of denture teeth: nanohybrid composite (NHC), interpenetrating network (IPN), and microfiller-reinforced polyacrylic (MRP). Denture teeth were processed by using an injection-molded resin or a compression-molded resin. Unprocessed denture teeth served as the control. After teeth were processed, they were sectioned into rectangular beams for 3-point bend testing (n=20 to 24). Elastic moduli were determined from load deflection and maximum stress from maximum bending load. The results were statistically analyzed by using 2-way ANOVA and multiple comparisons (α=.05)., Results: The processing technique and the type of denture tooth affected both the elastic modulus and the maximum stress. The injection-molded technique resulted in significantly higher (24% to 26%) elastic modulus for NHC and IPN (12% higher in MRP, but not statistically significant) and higher (12% to 17%) maximum stresses for IPN and MRP (3% lower in NHC, but not statistically significant). Compression-molded technique increased the elastic modulus of IPN and NHC by 10% to 17% (3% lower in MRP but not statistically significant), but maximum stresses were not statistically significantly different in any of the tested teeth. Regardless of processing, MRP teeth had the highest elastic modulus (8.0 to 9.2 GPa) but the lowest maximum stresses (97 to 124 MPa), whereas IPN teeth had the lowest elastic modulus (5.5 GPa) but high or highest maximum stress (171 to 192 MPa)., Conclusions: The injection-molded technique significantly increased the elastic modulus of NHC and IPN teeth and significantly increased the maximum stress of IPN teeth. The compression-molded technique did not significantly affect mechanical properties of denture teeth., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Purposes: The purposes of the present study were to examine the pressure transmission area and maximum pressure transmission of thermoplastic resin denture base materials under an impact load, and to evaluate the modulus of elasticity and nanohardness of thermoplastic resin denture base., Methods: Three injection-molded thermoplastic resin denture base materials [polycarbonate (Basis PC), ethylene propylene (Duraflex), and polyamide (Valplast)] and one conventional heat-polymerized acrylic resin (PMMA, SR Triplex Hot) denture base, all with a mandibular first molar acrylic resin denture tooth set in were evaluated (n=6). Pressure transmission area and maximum pressure transmission of the specimens under an impact load were observed by using pressure-sensitive sheets. The modulus of elasticity and nanohardness of each denture base (n=10) were measured on 15×15×15×3mm 3 specimen by using an ultramicroindentation system. The pressure transmission area, modulus of elasticity, and nanohardness data were statistically analyzed with 1-way ANOVA, followed by Tamhane or Tukey HSD post hoc test (α=.05). The maximum pressure transmission data were statistically analyzed with Kruskal-Wallis H test, followed by Mann-Whitney U test (α=.05)., Results: Polymethyl methacrylate showed significantly larger pressure transmission area and higher maximum pressure transmission than the other groups (P<.001). Significant differences were found in modulus of elasticity and nanohardness among the four types of denture bases (P<.001)., Conclusions: Pressure transmission area and maximum pressure transmission varied among the thermoplastic resin denture base materials. Differences in the modulus of elasticity and nanohardness of each type of denture base were demonstrated., (Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

This laboratory study was assessing the nano-mechanical properties (NMP), surface roughness (S a ), and topographic changes caused by ethanol on the surface of heat-polymerized denture base polymers at different time past dough stage. Specimens of heat polymerizing acrylic resin (Interacryl Hot, Interdent, Celje, Slovenia) of size 10×10×3 mm were prepared, wet ground, and polished for uniform smoothness and treated with ethanol in concentrations of 40, 70, and 99.9% for 30, 60, and 120 s and statistical analysis was done. Some statistical significance for S a were highest with 120 s exposure to 40% ethanol. NMP were the highest for specimens treated with 99.9% ethanol concentration for 120 s, on specimens prepared 30 min past the dough stage. This study suggested that heat-polymerized denture base polymers are prone for changes by ethanol which alters mechanical properties and surface topography. Dough time influenced the ethanol resistance.

Silanized aluminum borate whiskers (ABWs) of 4 wt%, silanized zirconium dioxide nanoparticles (nano-ZrO 2 ) of 2 wt% were mixed with polymethyl methacrylate (PMMA) powder to get ZrO 2 -ABWs/PMMA composites. Titanium dioxide (TiO 2 ), silver-supported titanium dioxide (Ag/TiO 2 ), silver-supported zirconium phosphate (Novaron) and tetrapod-like zinc oxide whiskers (T-ZnOw) antibacterial agents of 3 wt% were mixed with ZrO 2 -ABWs/PMMA composites respectively to fabricate standard specimens. Plaque biofilms on the specimens surface were investigated for colony-forming units (CFUs). In addition, cytotoxicity and mechanical behavior were evaluated. Results showed that the CFUs values of S. mutans and C. albican biofilms on the four antibacterial composites surface were all reduced (p<0.05) compared to the blank and control groups. The antibacterial composites did not have an adverse effect on fibroblast growth in this study (p>0.05) except TiO 2 and Ag/TiO 2 groups of undiluted extracts. The flexural strength and surface hardness of Novaron and T-ZnOw groups were increased (p<0.05) compared to the control group.

Statement of Problem: An attachment housing inside an overdenture may weaken the acrylic resin base. The type of housing retaining material may affect the strength of the housing retaining material-acrylic resin base assembly. The effect of different housing retaining materials on the strength of acrylic resin base is unknown., Purpose: The purpose of this in vitro study was to evaluate the effects of different materials used to retain the housing on the flexural strength of a poly(methyl methacrylate) (PMMA) resin base., Material and Methods: Sixty PMMA specimens (64×10×4 mm) were prepared with a clearance inside to allow the insertion of overdenture housings. Five different materials were used for housing orientation: an autopolymerizing composite resin, an acrylic resin reline material, a heat-polymerized PMMA, an autopolymerizing PMMA (n=10), and a control group (n=10) were prepared without any preparation or housing. The specimens were thermocycled 5000 times between 5°C and 55°C. The flexural strength data were analyzed by an analysis of variance using the maximum likelihood estimation method to eliminate the needs for normality within the groups and for equality of variances between the groups. If statistically significant, resolution of the significance factor was obtained by pairwise comparisons using the Tukey adjustment (α=.05)., Results: The fracture values were statistically significantly higher (P<.05) for the control group (90.22 ±12.46 MPa) than the test groups (heat-polymerized, 27.36 ±4.86 MPa), the autopolymerizing material (26.78 ±6.72 MPa), the acrylic resin reline material (16.94 ±4.38 MPa), the Ufigel (16.07 ±3.40 MPa), and the autopolymerizing composite resin (19.37 ±3.13 MPa). Heat- and autopolymerizing PMMA groups were significantly different from acrylic resin-based hard reline materials (P<.05). However, the remaining groups were not significantly different from each other. All fractures included both the PMMA and retaining material except for one of the hard reline groups, which separated from the PMMA., Conclusions: The tested retaining materials significantly reduced the flexural strength of PMMA denture base. The flexural strength of the resin base with housing was significantly higher when PMMA-based retaining materials were used than when acrylic resin-based hard reline materials were used., (Copyright © 2017 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

To develop dental restorative materials with "bio-active" functions, addition of the capability to release active agents is an effective approach. However, such functionality needs to be attained without compromising the basic properties of the restorative materials. We have developed novel non-biodegradable polymer particles for drug delivery, aimed for application in dental resins. The particles are made using 2-hydroxyethyl methacrylate (HEMA) and a cross-linking monomer trimethylolpropane trimethacrylate (TMPT), with a hydrophilic nature to adsorb proteins or water-soluble antimicrobials. The polyHEMA/TMPT particles work as a reservoir to release fibroblast growth factor-2 (FGF-2) or cetylpyridinium chloride (CPC) in an effective manner. Application of the polyHEMA/TMPT particles loaded with FGF-2 to adhesives, or those loaded with CPC to resin-based endodontic sealers or denture bases/crowns is a promising approach to increase the success of the treatments by conferring "bio-active" properties to these materials to induce tissue regeneration or to inhibit bacterial infection.

Aim: Different biomaterials and techniques have been introduced in the field of prosthetic dentistry with the purpose of replacement and rehabilitation of the edentulous areas. Due to their shorter setting time, the light-activated restorative and prosthetic materials have the capability of releasing few amount of cytotoxic materials in the oral cavity. Polymer materials [urethane dimethacrylate (UDMA) and bis-acryl] are assumed to have high mechanical properties. Polymethyl methacrylate (PMMA) offers numerous advantages of being highly esthetic in nature and at the same time being cost-effective. Hence, this study aimed to assess and compare the water sorption and cytotoxicity of light-activated UDMA denture base resin and conventional heat-activated PMMA resin., Materials and Methods: This study included assessment and comparison of water sorption and cytotoxicity of heat-activated PMMA resin and light-activated UDMA denture base system. Fabrication of heat-activated PMMA resin and UDMA specimens was done by investing the wax patterns in stone molds using manufacturer's instructions. Contraction of the specimens was done for assessment of cytotoxicity and water resorption of the UDMA and PMMA resin samples. All the results were analyzed by Statistical Package for the Social Sciences software version 18.0. Chi-square test and one-way analysis of variance tests were used for the assessment of the level of significance; p < 0.05 was taken as significant., Results: Mean lysis score observed in the PMMA and UDMA groups was 0.4 and 0.3 respectively. While observing at the 3 months time, the mean water resorption in the PMMA and UDMA groups was found to be 37.9 and 40.2 respectively. Significant difference in relation to water resorption was observed between the two study groups only at 3 months time., Conclusion: Both materials used in this study are nontoxic. Furthermore, UDMA resin materials exhibited lower water resorption after more than 1 month of time of storage., Clinical Significance: Water resorption is similar for different denture base resin systems till 1 months time.

Background and Overview: Snap-On Smile (DenMat) appliances are tooth-borne overdentures used for a variety of temporary esthetic applications. However, their benefit can be limited in patients with high smile lines and altered gingival architecture because the teeth look too large., Case Description: In this report, the author shows the chairside application of a silicone denture reline material used to recreate gingival anatomy on an overdenture fabricated from crystallized acetyl resin, the material used in a Snap-On Smile appliance. The author shows the gingival application's durability of greater than 2 years in a 78-year-old patient with multiple missing teeth and a severe mandibular ridge deformity. The author tested several commonly available denture reline materials and their bonding agents, which are known to bond to acrylic resin but have not been shown to bond to crystallized acetyl resin. The author observed no candida colonization during the 2-year reporting period., Conclusions and Practical Implications: The author presents a simple and durable chairside technique to reproduce gingival tissue esthetically on Snap-On Smile appliances., (Copyright © 2017 American Dental Association. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate the shear bond strengths of two gingiva-colored materials (an indirect composite material and a denture base acrylic resin) to zirconia ceramics and determine the effects of surface treatment with various priming agents., Methods: A gingiva-colored indirect composite material (CER) or denture base acrylic resin (PAL) was bonded to zirconia disks with unpriming (UP) or one of seven priming agents (n=11 each), namely, Alloy Primer (ALP), Clearfil Photo Bond (CPB), Clearfil Photo Bond with Clearfil Porcelain Bond Activator (CPB+Act), Metal Link (MEL), Meta Fast Bonding Liner (MFB), MR. bond (MRB), and V-Primer (VPR). Shear bond strength was determined before and after 5000 thermocycles. The data were analyzed with the Kruskal-Wallis test and Steel-Dwass test., Results: The mean pre-/post-thermalcycling bond strengths were 1.0-14.1MPa/0.1-12.1MPa for the CER specimen and 0.9-30.2MPa/0.1-11.1MPa for the PAL specimen. For the CER specimen, the ALP, CPB, and CPB+Act groups had significantly higher bond strengths among the eight groups, at both 0 and 5000 thermocycles. For the PAL specimen, shear bond strength was significantly lower after thermalcycling in all groups tested. After 5000 thermocycles, bond strengths were significantly higher in the CPB and CPB+Act groups than in the other groups., Conclusions: For the PAL specimens, bond strengths were significantly lower after thermalcycling in all groups tested. The MDP functional monomer improved bonding of a gingiva-colored indirect composite material and denture base acrylic resin to zirconia ceramics., (Copyright © 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Removable prosthodontics are often associated with mechanical troubles in daily use, such as fracture or deformation. These troubles render prostheses unusable and reduce wearers' QOL. Various reinforcements are used to prevent such problems, but consensus on reinforcement has not been reached. This review aimed to summarise the effects of reinforcement and to propose favourable reinforcement based on material, design and position in the prostheses. Initially, 139 articles were selected by electronic and manual searches. After exclusion of 99 articles based on the exclusion criteria, 40 articles were finally included in the review. Electronic searches were performed for articles published from 2005 to 2015 in PubMed, EMBASE, MEDLINE and Cochrane Library, and manual searches were performed in 10 journals relevant to the topic of removable prosthodontics. For in vitro studies, certain dental alloys and fibres were mainly used. Their forms were different, including complicated forms in dental alloys and various forms in fibres. The materials were examined for mechanical properties like fracture strength, flexural strength and elastic modulus and compared with one another or without reinforcement. There were a few clinical studies and one longitudinal study. Cast metal reinforcement seemed to be most favourable in terms of fracture toughness and stiffness. The most favourable forms differed depending on the prostheses, but placement around thin and deformable areas was effective. However, randomised or longitudinal clinical reports and comparative clinical studies on the use of reinforcement were still lacking and such studies are necessary in the future., (© 2016 John Wiley & Sons Ltd.)

To evaluate the effect of Dentaurum Grid Strengthener on flexural strength and modulus of two types of PMMA, 24 beams (75 mm x 10 mm x 2.5 mm) containing bonded and flattened Grid Strengthener and 24 beams without Grid Strengthener were subjected to a 3-point bending test at 5 mm/min. Flexural strength and modulus were calculated. Data were analyzed with a 2-way ANOVA. The highest mean strength and flexural modulus was measured for reinforced high impact resin (96.2±14.3 MPa and 3425±779 MPa, respectively). For flexural strength and modulus, resin and reinforcement had a significant effect., Clinical Relevance: Independent of the resin used, the incorporation of a grid strengthener increases the strength and modulus, thus the fracture probability of dentures is reduced., (Copyright© 2016 Dennis Barber Ltd.)

Statement of Problem: Poly(methyl methacrylate) (PMMA) obturator bulbs are hard and nonresilient. The relief for these obturators limits the support available for the bulbs and may limit mastication on the side with the resection. Resilient liners may improve mastication by gaining greater support from closer contact with tissues within the defects., Purpose: The purpose of this crossover clinical trial was to compare masticatory function scores of individuals with maxillectomies rehabilitated by using all-PMMA and PMMA obturator bulbs lined with resilient silicone., Material and Methods: Twelve participants with maxillectomies were provided with 2 definitive obturator dentures after initial rehabilitation. One of the obturator dentures had a hollow obturator bulb in all-PMMA, while the other had a hollow-core PMMA with an outer layer of silicone-resilient liner. Participants wore each obturator for a 2-week period without washout. Masticatory function on the rehabilitated sides was assessed by using an adapted Sato questionnaire. Statistical analysis was performed by using paired t test results of mean masticatory function scores (α=.05)., Results: Participants found 98.35% of the foodstuffs easy to masticate on the dentate sides. An average of 60.40% of the participants found the foodstuffs easy to masticate on the rehabilitated sides with the silicone-lined obturators. 18.35% of participants found the foodstuffs easy to masticate with the all-PMMA obturators (P<.05)., Conclusions: Resilient lining of PMMA resin obturator bulbs significantly improved masticatory ability in rehabilitated areas of the mouth., (Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Introduction: As civilization has progressed, there has been continued refinement of materials available for dental practice. The applications of resins have been extended to increased practical uses in numerous areas of prosthetic and restorative dentistry. Certain significant alterations in the technique of manipulation and nature of the dental product have influenced the range of application in dentistry. The present study was done to measure and compare the fracture strength of heat polymerized poly-methyl-methacrylate (PMMA) resin reinforced with fibers of glass, polyaramid, and nylon., Materials and Methods: The present study was conducted in vitro on 40 PMMA denture base resin specimens. Specimens were divided into four subgroups with ten specimens each and tested for transverse strength using universal testing machine., Results: In group I, the transverse strength mean value was 67.82 MPa. In group II, the transverse strength mean value was 59.47 MPa. In group III, the transverse strength mean value was 66.87 MPa, while in group IV, the transverse strength mean value was 66.47 MPa., Conclusion: Incorporation of 4% weight glass fibers in loose form significantly increased the transverse strength of denture base PMMA, while 4% of polyaramid fiber in random distribution significantly increased the transverse strength of denture base PMMA.

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-ZrO 2 ) 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-ZrO 2 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-ZrO 2 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-ZrO 2 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-ZrO 2 , whereas the lowest value was found in the butt group reinforced with 2.5% nano-ZrO 2 . 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-ZrO 2 . The bevel joint demonstrated mainly cohesive failure, whereas the butt joint demonstrated mainly adhesive failure., Conclusion: Incorporation of nano-ZrO 2 into the repair resin improved the flexural strength of repaired denture bases, whereas it decreased impact strength, especially with high nano-ZrO 2 concentrations., Competing Interests: The authors report no conflicts of interest in this work.

Introduction: Denture stomatitis is the most common pathology affecting denture wearers and its main cause is colonisation of dentures with Candida albicans., Objective: This study investigated the effectiveness of two commercial composite surface sealants (Biscover(®) LV and Surface Coat(®)) to reduce C. albicans biofilm colonisation on denture resin, as well as their surface integrity after disinfection cycles with 1% sodium hypochlorite solution., Methods: Heat-cured acrylic resin specimens were manufactured (10 mm × 10 mm × 1 mm). The specimen surfaces were mechanically polished to simulate rough or smooth denture surfaces. Four surface-treatment groups were tested: smooth surfaces [0.3 μm of mean roughness (Ra)]; rough surfaces (3 μm of Ra); rough surfaces treated with Biscover(®) LV; and rough surfaces treated with Surface Coat(®). Specimens of each group were randomly divided to undergo immersion in distilled water or 1% sodium hypochlorite for 30 or 90 cycles each. Specimens of all groups in each immersion solution were tested using a crystal violet (CV) staining assay for biofilm quantification and by scanning electron microscopy for visual analyses of surface integrity and biofilm structure. CV assay data were analysed using one-way analysis of variance (ANOVA) followed by Tukey's multiple comparison test (P < 0.05)., Results: The effectiveness and surface integrity of Biscover(®) LV-treated surfaces were similar to those of smooth surfaces, whereas Surface Coat(®) -treated surfaces presented a similar performance to rough surfaces in all solutions and cycles., Conclusion: These results suggest the possibility of clinical use of Biscover(®) LV for denture coating on surfaces in which mechanical polish is not indicated, such as the fitting surface., (© 2016 FDI World Dental Federation.)

Purpose: The purpose of this study was to investigate the possibilities of utilizing new acrylic denture base materials in resin clasps using three-point flexural tests and cantilever beam tests., Methods: Seven non-metal clasp denture (NMCD) materials and four acrylic denture base materials were used for three-point flexural tests and six NMCD materials and three acrylic denture base materials were used for cantilever beam tests. The flexural strength, elastic modulus, and 0.05% proof stress were measured by three-point flexural tests according to International Organization for Standardization (ISO) 20795-1. And load at 0.5mm deformation, elastic modulus were measured by Cantilever beam tests., Results: For the three-point flexural tests, only materials that met the conditions for both flexural strength and elastic modulus were the polycarbonate Reigning N (REN) and the acrylics Acron (AC), Pro Impact (PI), Procast DSP (PC) and IvoBase High Impact (HI) which are required in ISO 20795-1, Type 3 denture base materials. And for cantilever beam tests there was no significant difference between PI and either EstheShot (ES), EstheShot Bright (ESB), REN or Acry Tone (ACT) in load at 0.5mm deformation, and no significant difference between PI and either Lucitone FRS (LTF), ES, ESB, REN or ACT in elastic modulus., Conclusions: The results thus suggested that some of the acrylic materials used as denture base materials may also be usable for NMCDs, and that the flexural properties of the acrylic material PI resemble those of ES, ESB and ACT, meaning that similar clasp designs may also be feasible., (Copyright © 2015 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.)

Objective: To assess the clinical effects of carbon fiber reinforcement on the "All-on-Four" provisional prostheses., Methods: Provisional prostheses were divided into control group and carbon fiber reinforcing group according to whether carbon fiber reinforcement was used in the provisional prostheses base resin. In our study, a total of 60 patients (32 males and 28 females) with 71 provisional prostheses(28 maxilla and 43 mandible)were enrolled between April 2008 and December 2012 for control group; a total of 23 patients (13 males and 10 females) with 28 provisional prostheses (9 maxillas and 19 mandibles) were enrolled between January 2013 and March 2014 for carbon fiber reinforcing group. The information of provisional prostheses in the patients was recorded according to preoperative examination. We used the date of definitive prosthesis restoration as the cut-off point, observing whether fracture occurred on the provisional prostheses in the two groups. Additionally we observed whether fiber exposure occurred on the tissue surface of the provisional prostheses and caused mucosal irritation. The interface between the denture base resin and the fibers was examined using scanning electron microscopy (SEM)., Results: The age [(57.3 ± 10.1) years vs.(55.1 ± 11.4) years], gender (32 males and 28 females vs. 13 males and 10 females), maxilla and mandible distributions (28 maxillas and 43 mandibles vs. 9 maxillas and 19 mandibles), the number of extraction jaws (46 vs. 23), the average using time [(7.8 ± 1.3) months vs. (7.5 ± 1.1) months], and the opposing dentition distributions of provisional prostheses of the patients showed no significant differences between the control and reinforcing groups. There were 21(29.6%) fractures that occurred on the 71 provisional prostheses in the control group; there was no fracture that occurred on the 28 provisional prosthesesin the carbon fiber reinforcing group. The fracture rate of the carbon fiber reinforcing group was significantly lower than that of the control group (P=0.001). No carbon fiber exposure and mucosal irritation were observed from clinical examination.SEM revealed relatively continuous contact between the fiber and acrylic resin, and the resin particles adhered on the surface of the carbon fibers., Conclusion: The addition of carbon fibers between abutments placed on "All-on-Four" provisional fixed denture base resin may be clinically effective in preventing "All-on-Four" denture fracture and can provide several advantages for clinical use.

Background: Thermoplastic resin polymers are widely used in medicine due to their biostability and hypoallergenic properties, making them a possible alternative to poly-methylmethacrylate (PMMA). The current research examined the microstructure of a rapid injection molding system thermoplastic resin for construction of flexible denture compared with that of heat-cured PMMA., Materials and Methods: A total of 40 disk-shaped specimens (25 mm in diameter and 3 mm in thickness) were prepared and divided into two groups of 20 disks each (group I samples were of thermoplastic acrylic resin while group II was heat-cured PMMA resin)., Results: In group I, thermogravimetric analyzer showed that increasing the temperature up to 169°C resulted in about 1.3% of the material loss, and after that the material remains thermally stable up to 200°C. Group 11 showed 2.24% weight loss at 171°C, and further weight loss (12.025%) was observed on heating to 230°C. Fourier transform infrared (FTIR) spectrophotometer analysis in the range of 400-4000 cm(-1) detected the presence of an amine group (N-H) in group I samples and the presence of methylene group attached to inorganic Si as reinforcement filler (Si-CH3)., Conclusion: Thermoplastic resin displayed excellent thermal stability and the absence of residual monomer within the polymerized material, suggesting its suitability for the fabrication dentures.

It is important to choose an appropriate brush for denture cleaning to prevent damage to the surface properties of prosthetic devices. The purpose of this study was to evaluate the abrasiveness of toothbrushes and denture brushes on boiled and microwave-processed acrylic resins. Specimens of 4 resin brands were prepared (n = 30). Five brands of brushes (n = 6) were used in a toothbrushing machine, first for 17,800 strokes and then for an additional 35,600 strokes (total of 53,400), at a load of 200 g. An analytical balance and a profilometer were used to assess the weight and surface roughness, respectively, before and after 17,800 and 53,400 strokes. Analysis of variance and Tukey tests were used for data analysis (α = 0.05). Weight loss increased with time, while surface roughness remained the same. There were no statistically significant differences among toothbrushes and denture brushes in the resulting weight loss (17,800 strokes, 1.83 mg; 53,400 strokes, 3.78 mg) or surface roughness (17,800 or 53,400 strokes, 0.14 µm). The weight loss values after 53,400 brush strokes indicated that Clássico (2.28 mg) and VIPI Wave (2.75 mg) presented significantly greater abrasion resistance than Lucitone 550 (3.36 mg) and Onda-Cryl (2.85 mg) (P < 0.05). The type of brush and the polymerization method did not influence resin wear after brushing.

Objective: The aim of this study was to evaluate the effect of cycling deflection on the flexural behavior of injection-molded thermoplastic resins., Materials and Methods: Six injection-molded thermoplastic resins (two polyamides, two polyesters, one polycarbonate, one polymethyl methacrylate) and, as a control, a conventional heat-polymerized denture based polymer of polymethyl methacrylate (PMMA) were used in this study. The cyclic constant magnitude (1.0 mm) of 5000 cycles was applied using a universal testing machine to demonstrate plasticization of the polymer. Loading was carried out in water at 23ºC with eight specimens per group (n = 8). Cycling load (N) and deformation (mm) were measured., Results: Force required to deflect the specimens during the first loading cycle and final loading cycle was statistically significantly different (p < 0.05) with one polyamide based polymer (Valplast) and PMMA based polymers (Acrytone and Acron). The other polyamide based polymer (LucitoneFRS), polyester based polymers (EstheShot and EstheShotBright) and polycarbonate based polymer (ReigningN) did not show significant differences (p > 0.05). None of the materials fractured during the loading test. One polyamide based polymer (Valplast) displayed the highest deformation and PMMA based polymers (Acrytone and Acron) exhibited the second highest deformation among the denture base materials., Conclusion: It can be concluded that there were considerable differences in the flexural behavior of denture base polymers. This may contribute to the fatigue resistance of the materials.

A 37 year old male presented with the complaint of a loose and bulky acrylic obturator prosthesis. He had previously tried to using a different acrylic obturator prostheses as well as both cobalt chromium and titanium framework obturators. The most successful previous prosthesis was a titanium based obturator which had performed well prior to a fractured clasp. Accordingly, following an exploration of the available surgical and prosthodontic treatment options, a further tooth borne partial maxillary obturator was provided successfully. The case highlights the relative merits and limitations of the use of cast titanium as a denture base material in partial denture and obturator construction.

Monomer remaining in denture base acrylic can be a major problem because it may cause adverse effects on oral tissue and on the properties of the material. The purpose of this study was to compare the effect of various ultrasonic cleaner frequencies on the amount of residual monomer in acrylic resin after curing. Forty-two specimens each of Meliodent heat-polymerized acrylic resin (M) and Unifast Trad Ivory auto-polymerized acrylic resin (U) were prepared according to their manufacturer's instructions and randomly divided into seven groups: Negative control (NC); Positive control (PC); and five ultrasonic treatment groups: 28 kHz (F1), 40 kHz (F2), 60 kHz (F3) (M=10 min, U=5 min), and 28 kHz followed by 60 kHz (F4: M=5 min per frequency, U=2.5 min per frequency, and F5: M=10 min followed by 5 min per frequency, U=5 min followed by 2.5 min per frequency). Residual monomer was determined by HPLC following ISO 20795-1. The data were analyzed by One-way ANOVA and Tukey HSD. There was significantly less residual monomer in the auto-polymerized acrylic resin in all ultrasonic treatment groups and the PC group than that of the NC group (p<0.05). However, the amount of residual monomer in group F3 was significantly higher than that of the F1, F4, and PC groups (p<0.05). In contrast, ultrasonic treatment did not reduce the amount of residual monomer in heat-polymerized acrylic resin (p>0.05). The amount of residual monomer in heat-polymerized acrylic resin was significantly lower than that of auto-polymerized acrylic resin. In conclusion, ultrasonic treatment at low frequencies is recommended to reduce the residual monomer in auto-polymerized acrylic resin and this method is more practical in a clinical situation than previously recommended methods because of reduced chairside time., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Statement of Problem: In restorative prostheses, color is important, but the choice of color difference formula used to quantify color change in acrylic resins is not straightforward., Purpose: The purpose of this in vitro study was to choose a color difference formula that best represented differences between the calculated color and the observed imperceptible to unacceptable color and to determine the corresponding perceptibility and acceptability threshold of color stability for denture base acrylic resins., Material and Methods: A total of 291 acrylic resin denture base plates were fabricated and subjected to radiation tests from zero to 42 hours in accordance with ISO 7491:2000. Color was measured with a portable spectrophotometer, and color differences were calculated with 3 International Commission on Illumination (CIE) formulas: CIELab, CMC(1:1), and CIEDE2000. Thirty-four observers with no deficiencies in color perception participated in psychophysical perceptibility and acceptability assessments under controlled conditions in vitro. These 2 types of assessments were regressed to each observer by each formula to generate receiver operator characteristic (ROC) curves. Areas under the curves (AUCs) were then calculated and analyzed to exclude observers with poor color discrimination. AUCs were subjected to 1-way ANOVA (α=.05) to deter the statistical significance of discriminability among the 3 formulas in terms of perceptibility and acceptability judgments. Student-Newman-Keuls tests (α=.05) were used for post hoc comparison., Results: CMC(1:1) and CIEDE2000 formulas performed better for imperceptible to unacceptable color differences, with corresponding CMC(1:1) and CIEDE2000 values for perceptibility of 2.52 and 1.72, respectively, and acceptability thresholds of 6.21 and 4.08, respectively., Conclusions: Formulas CMC(1:1) and CIEDE2000 possess higher discriminability than that of CIELab in the assessment of perceptible color difference threshold of denture base acrylic resin. A statistically significant difference exists between perceptibility and acceptability thresholds for denture base acrylic resin., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

In traditional dental implant therapy, the time between implant placement and delivery of the definitive prosthesis can be long and uncomfortable for a patient wearing a conventional removable denture on an atrophied ridge. New clinical protocols, often with tilted implants, are being used to immediately restore mandibular implants with interim restorations, thus shortening the patient's return to function. However, these conversion type interim restorations do not decrease the time to definitive prosthetic rehabilitation. The Ohio State University (OSU) developed an immediate load surgical and prosthetic protocol to compensate for the disadvantages of previous techniques. With this protocol, a custom, definitive, screw-retained metal-resin fixed prosthesis can be delivered 2 to 4 days postoperatively and has been described using 5 implants. This clinical report presents the OSU immediate loading protocol, combined with a tilted implant technique, for the fabrication of a mandibular metal-resin implant fixed complete dental prosthesis (MRIFCDP) in 3 days postoperatively and with only 4 implants. Replacing the mandibular dentition with an immediate load-fixed metal-resin prosthesis by means of the "final-on-four" technique resulted in a custom, definitive, and functional restorative solution immediately after surgery., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Statement of Problem: The optimum selection of denture teeth for patients with a reduced interarch distance has not been established., Purpose: The purpose of this in vitro study was to investigate the influence of denture tooth material and thickness on the fracture resistance of thin acrylic resin denture bases., Material and Methods: Acrylic resin (AC), composite resin (CO), or ceramic (CE) molar denture teeth were embedded in denture base blocks (2.0 mm thick). The distance from the central fossa to the tooth base was 0.5, 1.0, 2.0, or 2.5 mm for AC and CO, and 1.0 mm for CE (n=7), with a total thickness of 2.5 mm for all specimens. Each specimen was placed on a 3-point flexural setup with a shorter (8 mm) or longer (12 mm) support span than the tooth width and vertically loaded. A finite element analysis was performed to assess the stress distributions. The effects of tooth thickness and support span were statistically tested with ANOVA, followed by the Tukey honestly significant difference post hoc test (α= .05)., Results: With the shorter support, the mean fracture load was higher in CO than AC, regardless of the tooth thickness. Under the longer support, the mean fracture load with the CO decreased significantly as the tooth thickness increased, with increased maximum stress. Some CO tooth specimens of 2.0 mm or 2.5 mm thickness failed at the tooth-denture base interface at significantly lower loads than those exhibited by tooth fractures. CE showed minor cracks before bulk fracture., Conclusions: Higher fracture resistance was indicated with CO; however, the resistance decreased as the thickness of the CO tooth increased., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Objective: The purpose of this study was to determine the effects of two denture cleansing methods on 3-D surface roughness, gloss and color of denture base materials., Materials and Methods: Thirty disks from nylon (Valplast) and 30 from heat-polymerized acrylic denture base material (Paladon 65) were made and 10 of each material were immersed in water (control), Val-Clean (peroxide cleanser) and Corega Extradent (peroxide cleanser) plus microwaving for a period simulating 30 days of daily cleansing. 3-D surface roughness, gloss and color parameters were measured before and after cleansing using an interferometric profilometer, a gloss meter and a colorimeter. The results were statistically analysed by regression, paired-t, Mann-Whitney and Kruskal-Wallis tests at α = 0.05 level of significance., Results: The results showed significant differences at baseline in L* and b* parameters between materials (p < 0.01), with a significantly lower gloss (p < 0.05) and higher roughness (p < 0.05) for Valplast. After cleansing, Δϵ* was significantly greater in Valplast than Paladon 65 (p < 0.05). Gloss of both materials decreased significantly within the Corega Extradent plus microwave solution (p < 0.05), while roughness increased significantly only for Paladon 65 (p < 0.05)., Conclusions: Valplast was found to have a significantly lower gloss and a higher roughness than Paladon 65 before cleansing. After cleansing, ΔE* increased more in Valplast than in Paladon 65, gloss of both materials decreased and roughness only of Paladon 65 increased within the Corega extradent plus microwaving method.

Statement of Problem: No study has yet evaluated the strength of complete dentures reinforced with glass fiber meshes with different content and structures., Purpose: The purpose of this study was to compare the reinforcing effects of glass fiber mesh with different content and structures with that of metal mesh in complete dentures., Material and Methods: Two types of glass fiber mesh were used: SES mesh (SES) and glass cloth (GC2, GC3, and GC4). A metal mesh was used for comparison. The complete dentures were made by placing the reinforcement 1 mm away from the tissue surface. A control group was prepared without any reinforcement (n=10). The compressive properties were measured by a universal testing machine at a crosshead speed of 5 mm/min. The results were analyzed with the Kruskal-Wallis test and the Duncan multiple range test (α=.05)., Results: The fracture resistance of the SES group was significantly higher than that of the control, GC4, and metal groups (asymptotic P=.004), but not significantly different from the GC2 and GC3 groups. The toughness of the SES and GC3 groups was significantly higher than that of the others (asymptotic P<.001), but not significantly different from that of the GC4 group., Conclusions: SES and GC3, which have different structures but similar volume content, were the most effective in reinforcing complete dentures. The content of the glass fiber mesh seemed more important than the structures., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)

Recently, monolithic zirconia restorations have received attention as an alternative to zirconia veneered with feldspathic porcelain to eliminate chipping failures of veneer ceramics. In this clinical report, a patient with mandibular edentulism received 4 dental implants in the interforaminal area, and a screw-retained monolithic zirconia prosthesis was fabricated. The patient also received a maxillary complete removable dental prosthesis over 4 anterior roots. At the 18-month follow-up, all of the zirconia cylinders were seen to be fractured, and the contacting abutment surfaces had lost structural integrity. The damaged abutments were replaced with new abutments, and a new prosthesis was delivered with a computer-assisted design and computer-assisted manufacturing fabricated titanium framework with denture teeth and denture base resins. At the 6-month recall, the patient did not have any problems. Dental zirconia has excellent physical properties; however, care should be taken to prevent excessive stresses on the zirconia cylinders when a screw-retained zirconia restoration is planned as a definitive prosthesis., (Copyright © 2015 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.)