Heat-polymerized Polymethyl Methacrylate Research Articles

Comparative evaluation of impact strength of mechanically modified heat polymerized polymethyl methacrylate (PMMA) resin with addition of 0.5, 1, 2 wt% of silver nanoparticles (AgNPs): An in-vitro study.

Polymethyl methacrylate (PMMA) is one of the most widely used denture base material because of favorable esthetics and desirable characteristics such as easy handling. Acrylic resins, although, have some inherent disadvantages such as relatively poor physical and mechanical properties. The objective of the present study was to evaluate and compare the impact strength of unmodified and modified heat cure PMMA-based denture base material with addition of different concentrations of silver nanoparticles (AgNPs) (0.5, 1, 2 wt%). The present in-vitro study comprised of a total of 60 samples allocated to four groups with Group A samples consisting of heat cure acrylic resin without any modification (used as control); Group B samples consisting of heat cure acrylic resin modified with 0.5 wt% of AgNPs; and subsequently, Group C and Group D samples consisting of heat cure acrylic resin modified with 1 wt% and 2 wt% of AgNPs, respectively. The impact strength of the prepared acrylic samples was evaluated using Izod/Charpy Impact Tester, while the values obtained were tabulated and subjected to statistical analysis. Statistical analysis was done using Statistical Package for Social Sciences (SPSS) version 17.0 (SPSS Inc., Chicago, IL, USA), while one-way analysis of variance and Tukey's multiple post-hoc procedures were used for statistical analysis. P < .05 was considered statistically significant. The highest impact strength was found in Group C samples consisting of heat cure acrylic resin modified with 1 wt% of AgNPs to be closely followed by Group B samples consisting of heat cure acrylic resin modified with 0.5 wt% of AgNPs. Group D samples consisting of heat cure acrylic resin modified with 2 wt% of AgNPs, although, revealed relatively lower impact strength compared to Group B and Group C samples. Within the limitations of the present study, it was concluded that the impact strength of mechanically modified heat polymerized PMMA resin was significantly enhanced with addition of varying concentrations of AgNPs, although, it was observed that with an increase in the concentration of AgNPs, a subsequent decrease in the tensile strength of the final polymer material was observed.

Evaluation of shear bond strength of high molecular chitosan nanoparticle incorporated heat polymerized polymethyl methacrylate denture base resin with acrylic resin teeth: An in-vitro study

The present study is conducted to evaluate the shear bond strength of acrylic resin denture teeth to high molecular chitosan nanoparticle incorporated heat polymerized polymethylmethacrylate denture base resin. This comparative study is performed at the Department of Prosthodontics and Crown & Bridge, JSSDCH, Mysuru. 45 samples of acrylic resin blocks of size 8 × 10 × 20 mm were fabricated using mold such that the long axis of crosslinked acrylic resin maxillary central incisor teeth is aligned at 45° to the long side of the specimen to which the ridge lap surface is attached. Among these, 15 samples belong to the control group, 15 samples to the 0.5 % chitosan gel incorporated group, and the remaining 15 samples to the 1 % chitosan gel incorporated group. The test specimens were then subjected to a failure load test using the universal testing machine. The readings were tabulated and statistically analyzed using Mean, Standard deviation, Independent t-test, - way and two-way ANOVA, and Scheffes’ Post hoc test. The statistical analysis reveals that the mean bond strength of acrylic denture teeth to conventional heat cure PMMA denture base material increased from 4.6627 ± 0.54198 MPa to 7.5186 ± 0.57461 MPa and 8.9356 ± 0.63675 MPa upon addition of chitosan at 0.5 % and 1 % concentration, respectively. It can be concluded that The mean shear bond strength of acrylic denture teeth to conventional heat cure PMMA denture base material increased with the addition of chitosan at 0.5 and 1 % concentration. The best shear bond strength was observed with the addition of 1 % chitosan as per the evidence.

Evaluation of Candida albicans biofilm formation on conventional and computer-aided-design/computer-aided manufacturing (CAD/CAM) denture base materials.

The human mouth mucosal surface is colonized by indigenous microflora, which normally maintains an ecological balance among different species. However, certain environmental or biological factors may disrupt this balance, leading to microbial diseases. Candida albicans biofilms are formed on indwelling medical devices and have an association with both oral and invasive candidiasis. This study aimed to compare the amount of adherent C. albicans and the biofilm formed on different denture base materials. The adhesion of C. albicans to denture base materials is widely recognized as the main reason for the development of denture stomatitis. In total, 56 polymethyl methacrylate (PMMA) acrylic resin disc-shaped samples were divided into four groups as follows: 1) chemically polymerized PMMA, 2) heat-polymerized PMMA, 3) computer-aided design and computer-aided manufacturing (CAD/CAM) PMMA in high polish, and 4) CAD/CAM resins in glazed form. The adherent cells and formation of C. albicans strains (562, 1905, 1912, and 1949) biofilm were measured by the 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) method and use of a microplate reader. Moreover, morphological alterations of C. albicans cells were investigated using scanning electron microscopy (SEM). The biofilm formation was significantly lower on CAD/CAM acrylic resins, compared to conventional denture base materials. The obtained results were confirmed by the SEM images of C. albicans biofilms. CAD/CAM PMMA-based polymers may be preferable to inhibit C. albicans biofilm formation and reduce Candida-associated denture stomatitis in long-term use. Based on the findings, the CAD/CAM technique can be used as an efficient technique for denture fabrication as it inhibits microbial accumulation, and consequently, microbial biofilm.

Surface roughness and stainability of CAD-CAM denture base materials after simulated brushing and coffee thermocycling

Statement of problemDenture 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. PurposeThe purpose of this in vitro study was to compare the effect of simulated brushing and CTC on the surface roughness (Ra) and stainability of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base materials and a heat-polymerized denture base material. Material and methodsForty 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). Ra 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. Ra and color coordinates were measured after each interval. Color differences (ΔE00) 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). ResultsThe time interval had a significant effect on Ra (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 ΔE00 (P=.016). The only significant difference in ΔE00 values was observed between M-PM and CV after all treatments were completed (P=.029). ConclusionsBrushing increased the Ra 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.

Translucency parameter and color masking ability of CAD-CAM denture base materials against metal substrates.

To investigate the translucency parameters of traditional, milled, and 3D-printed denture base materials at 3 different thicknesses and the color masking ability of each material against a metallic background between different thicknesses. A traditional heat-polymerizing polymethylmethacrylate (PMMA) (H-Lucitone) material was used as the control group. Two milled pre-polymerized resin blocks (M-Lucitone and IvoBase) and five 3D-printed denture base materials (P-Lucitone, Dentca LP, Dentca OP, Formlabs, and Kulzer) were used as experimental groups. A total of 240 samples, (n = 30, per material) were fabricated to a final specimen dimension of 12×12mm and in thicknesses of 1.0, 2.0, and 3.0mm (n = 10 per thickness/material) according to themanufacturers' recommendations. The color coordinates (L*, a*, b*) in CIELab color space for all specimens placed against a white, black, and metallic background were measured with a spectrophotometer. The translucency parameters (TP00 ) at each thickness and the color differences between 1mm and 2 mm (dE00M1-2 ) and between 2 mm and 3 mm (dE00M2-3 ) against the metallic background were calculated with the CIEDE2000 color matrix. Comparisons between the groups for differences in TP00 were made using One-way ANOVA separately for each thickness. Comparisons of groups and materials for differences in dE00M1-2 and dE00M2-3 were made using Two-way ANOVA and Fisher's Protected Least Significant Differences (α = 0.05). The TP00 decreased with increasing thickness in all 8 material groups. All 3D-printed materials, except P-Lucitone, had higher TP00 than milled pre-polymerized resin materials (M-Lucitone and IvoBase), and traditional heat-polymerizing PMMA (H-Lucitone) material (P<.001) at all thicknesses. In the 1 mm and 2 mm thickness, heat-polymerizing acrylic resin (H-Lucitone) had the lowest TP00 , and in the 3 mm thickness, milled acrylic resin (M-Lucitone and IVOBase) had had lowest TP00 (p < 0.001). All material groups had significantly lower values of dE00M2-3 than dE00M1-2 (p < 0.001). The color differences dE00M2-3 were significantly lower in H-Lucitone, M-Lucitone, P-Lucitone, and IvoBase groups than in other materials, while the color difference of dE00M1-2 was significantly lower in H-Lucitone, P-Lucitone and Dentca LP than other materials (p < 0.001). The results from this study provide clinicians and dental technicians with information regarding the selection of denture base materials to achieve desired color masking outcomes, according to available prosthetic space. Thicker prostheses significantly improved the color masking abilities of denture acrylic resins against a metallic background. In a thickness of 1 and 2 mm, the heat-polymerizing acrylic resin had a lower translucency parameter and better color masking ability. When the prosthesis thickness reached 3 mm, the milled acrylic resin had a lower translucency parameter and better color masking ability. When compared to the heat-polymerizing resin and milled acrylic resin materials, except for one 3D-printing resin (P-Lucitone), the color masking abilities of the remaining 3D-printing resin materials were low, regardless of prosthesis thickness.

Effects of long-term cinnamaldehyde immersion on the surface roughness and color of heat-polymerized denture base resin

Statement of problemCinnamaldehyde has been successfully used for the short-term disinfection of dentures; however, its long-term effects on the surface and color properties of denture base materials remain unknown. PurposeThe purpose of this in vitro study was to evaluate the effects of simulated immersion in cinnamaldehyde for up to 5 years on the surface roughness and color parameters of a heat-polymerized denture resin. Material and methodsEighty Ø10×5-mm disk-shaped specimens were prepared from microwave heat-polymerized polymethylmethacrylate (PMMA) and immersed in 4 solutions (n=20): TW–tap water (control), SH – 0.5% sodium hypochlorite, PX–alkaline peroxide, and CA–cinnamaldehyde (27 μg/mL). The immersion protocol simulated 104 cycles (3.5 months), 913 cycles (2.5 years), and 1825 immersion cycles (5 years) of a daily immersion cleaning protocol, with immersion times ranging from 10 to 20-minutes. Surface roughness (Sa) and the color parameters of CIELab (L∗ a∗ b∗, ΔEab), CIEDE2000 (ΔE00), and the National Bureau of Standards (NBS) were analyzed at baseline (t=0) and after the immersion cycles. The data were analyzed by 2-way analysis of variance (ANOVA) for repeated measures and the Tukey post hoc test (α=.01). ResultsSa was significantly increased in all groups after 1825 cycles compared with baseline (P<.01), regardless of the solution. Only the time factor significantly affected ΔEab, ΔE00, and NBS parameters, which were below the perceptibility and acceptability thresholds. After a simulated 5-year immersion, the surface roughness and color values of CA-treated specimens were not statistically different from those of the other groups (P>.01). ConclusionsCinnamaldehyde solution (27 μg/mL) produced minor effects on the surface roughness and color parameters of a heat-polymerized denture base resin similar to those of 0.5% sodium hypochlorite and alkaline peroxide after a 5-year simulated immersion.

Flexural Properties, Impact Strength, and Hardness of Nanodiamond-Modified PMMA Denture Base Resin.

Purpose Investigate the effect of low nanodiamond (ND) addition and autoclave polymerization on the flexural strength, impact strength, and hardness of polymethylmethacrylate (PMMA) denture base. Methods A total of 240 heat polymerized PMMA were fabricated with low ND concentrations of 0.1%, 0.25%, and 0.5%, and unmodified as control. The specimens were divided equally into group I: conventionally polymerized PMMA by water bath and group II: polymerized by the autoclave. The impact strength, flexural strength, and elastic modulus were tested using the Charpy-type impact-testing machine and three-point bending test, respectively. A scanning electron microscope (SEM) was used to analyze the fractured surfaces. Surface hardness was measured by a hardness tester with a Vickers diamond. The bonding and interaction between the PMMA and ND particles were analyzed by the Fourier-transform infrared (FTIR) spectroscope. ANOVA and post hoc Tukey test were used for data analysis (α = 0.05). Results ND addition significantly increased the flexural strength of groups I and II (p < 0.001, p=0.003); it was highest (128.8 MPa) at 0.25% ND concentration for group I and at 0.1% for group II. Elastic modulus increased at 0.1% ND for both groups (p=0.004, p=0.373), but the increase was statistically significant for group I only. Impact strength showed no significant change with the addition of ND in groups I and II (p=0.227, p=0.273), as well as surface hardness in group I (p=0.143). Hardness decreased significantly with 0.25%ND in group II. Conclusion The addition of ND at low concentration increased the elastic modulus and flexural strength of conventionally and autoclave polymerized denture base resin. Autoclave polymerization significantly increased the flexural strength, impact strength, and hardness of unmodified PMMA and hardness of 0.5% ND group.

Color stability of heat polymerized complete dentures and 3D printed CAD/CAM dentures

Background/aim Color stability of complete dentures is one of the most significant aspects that affect the success of complete dentures (CD) and improve the patient’s quality of life. Therefore, the present clinical crossover research targeted to assess and compare the color stability of conventional heat-polymerized polymethyl methacrylate (PMMA) CDs and three-dimensional (3D)-printed dentures and their effect on the ‘oral health-related quality of life’ (OHRQoL). Patients and methods Twenty completely edentulous patients aged from 45 to 75 received two sets of CDs. The first denture set was polymethyl methacrylate CD (group I), and the patients were instructed to use it for 3 months. Then after 3 months, the patients were instructed to wear the 3D-printed CD set (group II) and use it for another 3 months. The color change of the CD’s base was evaluated at denture insertion after 1 and 3 months using a spectrophotometer. The ‘OHRQoL ’ was used to assess patient satisfaction at the end of the treatment of every denture set. Statistical analysis was accomplished through an independent t test and one-way analysis of variance. Results Regarding the color change of the CD denture base at denture insertion, there was an insignificant distinction between group I and group II (P&gt;0.05). While after 1 and 3 months, group I showed a significant increase in the color change when compared with group II (P&lt;0.05). When comparing the color change in each group during the different follow-up periods, the color change was significantly increased in both groups (P&lt;0.05). In terms of ‘OHRQoL,’ there was a significant distinction between group I and group II (P&lt;0.05). Group II (18.89) scored less than group I (43.42). Conclusion 3D-printed CDs exhibit good color stability when compared with conventional CDs. The OHRQoL revealed that 3D-printed CDs have more patient satisfaction than conventional CDs.

Adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized polymethyl methacrylate with thermocycling

Statement of problemComputer-aided design and computer-aided manufacturing (CAD-CAM) technologies have become popular for manufacturing complete dentures. However, the adhesive strength of resilient liners to the polymers used to fabricate CAD-CAM complete dentures is unclear. PurposeThe purpose of this in vitro study was to determine the adhesive strength of 3 long-term resilient liners to CAD-CAM denture base polymers and heat-polymerized PMMA with thermocycling. Material and methodsA total of 90 specimens were fabricated, 30 per group of denture base material (Lucitone 199, Ivo Base CAD, Denture Base LP). For each denture base polymer, 10 specimens were relined with 1 of 3 resilient liners (Permasoft, Mucopren Soft, Molloplast-B). Five specimens of each group were thermocycled, and the other 5 specimens were stored in distilled water. Subsequently, the adhesive strength of the specimens was assessed by tensile testing. The resulting data were analyzed by using a 3-way analysis of variance (ANOVA) (α=.05). ResultsAfter thermocycling, the adhesive strengths of all the resilient liners were found to be statistically different from each other for the same denture base polymer (P≤.012). Mucopren Soft displayed a high mean ±standard deviation adhesive strength to Lucitone 199 (1.78 ±0.32 MPa), followed by Molloplast-B (1.27 ±0.21 MPa) and Permasoft (0.66 ±0.06 MPa). For Ivo Base CAD, Molloplast-B exhibited a high mean ±standard deviation adhesive strength (1.70 ±0.36 MPa), followed by Mucopren Soft (1.11 ±0.16 MPa) and Permasoft (0.53 ±0.04 MPa). Molloplast-B displayed high mean ±standard deviation adhesive strength to Denture Base LP (1.37 ±0.08 MPa), followed by Mucopren Soft (0.68 ±0.20 MPa) and Permasoft (0.32 ±0.04 MPa). The adhesive strength of the majority of resilient liners not exposed to thermocycling was statistically different from each other for the same type of denture base polymer (P<.001). The only exception was the difference between the adhesive strength of Molloplast-B and Mucopren Soft to Lucitone 199 with mean ±standard deviation values of 1.42 ±0.18 and 1.66 ±0.40 MPa, respectively, (P=.067). Without thermocycling, the mean ±standard deviation adhesive strength to Lucitone 199 of Permasoft (0.57 ±0.02 MPa) was statistically different from that of Molloplast-B and Mucopren Soft (P<.001). Molloplast-B displayed a high mean ±standard deviation adhesive strength to Ivo Base CAD (1.83 ±0.25 MPa), followed by Mucopren Soft (1.26 ±0.19 MPa) and Permasoft (0.58 ±0.08 MPa). Molloplast-B displayed a high mean ±standard deviation adhesion to Denture Base LP (1.76 ±0.23 MPa), followed by Mucopren Soft (0.88 ±0.14 MPa) and Permasoft (0.25 ±0.06 MPa). Only Molloplast-B was significantly adversely affected by thermocycling (P=.009). ConclusionsMolloplast-B displayed high adhesive strength to both CAD-CAM denture base polymers regardless of the storage conditions. Mucopren Soft displayed high adhesion to Lucitone 199. Permasoft presented moderate adhesion to PMMA-based denture bases and low adhesion to DBLP. Combining Permasoft with Denture Base LP should be considered carefully and limited to short-term use. Thermocycling had a detrimental effect on the adhesive strength of Molloplast-B.

Antimicrobial Effect of Polyhexanide on Denture Base and Soft Lining Materials

Objective: Polyhexanide (PHMB; polyhexamethylene biguanide) is a well-known antiseptic agent; however, no data exist for its applicationon denture base and lining materials. In the present in vitro study, the aim was to compare viable bacterial or fungal cell numbers and theiradhesion on different types of denture base and lining materials in diverse concentrations of PHMB.Methods: Light-activated urethane dimethacrylate (UDMA), heat-polymerized polymethyl methacrylate (PMMA), heat-polymerizedpolydimethylsiloxane, and autopolymerizing polyethylmethacrylate discs were prepared for each group (n = 10). 1×108 CFU/mL of all the testedspecies were appended separately to discs, and they were immersed into different PHMB suspensions (0.5%, 1%, 2%, and 5%) for 10 minutes.The antimicrobial activity and number of adherent species on the surface were evaluated.Results: In the PMMA group, all studied species except C. albicans, L. acidophilus, and S. aureus were decreased in various concentrations (p &amp;lt;0.05), and all studied species presented a significant decrease in every concentration of PHMB in the UDMA group (p &amp;lt; 0.01) in comparison to thecontrol. N. sicca, K. pneumoniae, S. pyogenes, S. sanguis, C. pseudotuberculosis, and S. aureus (p &amp;lt; 0.05) were reduced in the heat-polymerizedpolydimethylsiloxane group, while all tested species except B. subtilis were decreased in the autopolymerizing polyethylmethacrylate group incomparison to the control (p &amp;lt; 0.01). Among all tested materials and species, no significant difference was detected in adherent cell number(p &amp;gt; 0.05).Conclusion: PHMB suspension, in various concentrations, can reduce some species of bacterial and yeast cells.

A Comparison of the Surface and Mechanical Properties of 3D Printable Denture-Base Resin Material and Conventional Polymethylmethacrylate (PMMA).

To study the surface and mechanical properties of 3D printed denture-base resin materials and compare them with conventional heat-cured polymethylmethacrylate (PMMA). Three brands of 3D printed denture-base resin materials and one conventional heat-cured PMMA were tested in this study: NextDent 3D printed resin, Dentona 3D printed resin, ASIGA 3D printed resin, and Meliodent conventional PMMA. Sixty specimens (25 × 25 × 3 mm) were fabricated (n=15 per group) to perform the following tests: wettability, surface roughness, and microhardness. One hundred twenty specimens (65 × 10 × 3 mm) were fabricated (n=30 per group) and stored in distilled water at (37 ±1°C) for 7 days. Specimens (N = 15) in each group were subjected to the three-point bending test and impact strength test, employing the Charpy configuration on un-notched specimens. The morphology of the fractured specimens was studied under scanning electron microscope (SEM). Statistical analysis was performed using one-way ANOVA and Tukey-pairwise multiple comparisons with 95% confidence interval. P-values of ≤0.05 were considered significant. The conventional heat-cured specimens demonstrated the highest means of surface roughness (0.23 ± 0.07 μm), Vickers hardness number (18.11 ±0.65) and flexural strength (92.44 ±7.91 MPa), and the lowest mean of contact angle (66.71° ±3.38°). ASIGA group showed the highest mean of contact angle (73.44° ±2.74°) and the lowest mean of surface roughness (0.19 ±0.03 μm). The highest mean of impact strength was recorded in the Dentona group (17.98 ±1.76 kg/m2 ). NextDent specimens showed the lowest means of Vickers hardness number (16.20 ±0.93), flexural strength (74.89 ±8.44 MPa), impact strength (15.20 ±0.69 kg/m2 ), and recorded the highest mean of bending modulus (2,115.80 ±178.95 MPa). 3D printed resin exhibited noticeable differences in surface and mechanical properties between different brands and with conventional heat-polymerized PMMA.

Effect of different disinfection protocols on the surface properties of CAD-CAM denture base materials

Statement of problemWhich disinfection protocol provides optimal water contact angle and microhardness for computer-aided design and computer-aided manufacturing (CAD-CAM) polymethyl methacrylate (PMMA) materials is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of different disinfection protocols (1% sodium hypochlorite, denture cleanser gel, and effervescent tablet) on the water contact angle and microhardness of different CAD-CAM PMMA denture base materials by comparing them with a heat-polymerized PMMA. Material and methodsDisk-shaped specimens (Ø10×2 mm) were fabricated from 3 different CAD-CAM PMMAs—AvaDent (AV), Merz M-PM (M-PM), and Polident (Poli)—and a heat-polymerized PMMA (Vynacron) (CV) (n=21). Three disinfection protocols (1% sodium hypochlorite [HC], denture cleanser gel [GEL], an effervescent tablet [TAB]) were applied to simulate 180 days of cleansing. The water contact angle and microhardness of specimens were measured before and after disinfection and compared by using a 2-way ANOVA (α=.05). ResultsFor water contact angle, material (P=.010) and disinfection protocol (P=.002) had a significant effect. The material (P<.001), disinfection protocol (P=.001), and their interaction (P<.001) significantly affected the microhardness after disinfection. When the condition after disinfection was compared with that before disinfection, the water contact angle increased significantly in all material-disinfection protocol pairs (P≤.025), and microhardness increased significantly in all material-disinfection protocol pairs (P≤.040), except for GEL- (P=.689) or TAB-applied (P=.307) AV, HC-applied M-PM (P=.219), and TAB-applied Poli (P=.159). ConclusionsThe material and disinfection protocol affected the water contact angle of all tested PMMAs after disinfection, resulting in more hydrophobic surfaces for heat-polymerized or CAD-CAM PMMAs. The microhardness of heat-polymerized PMMA was less than that of all CAD-CAM PMMAs after disinfection, regardless of the protocol.

Evaluation of flexural strength and surface hardness of heat activated provisional PMMA resin reinforced with nanoparticles-an in vitro study

The provisional restorations are subjected to vertical, lateral and horizontal forces during function, hence the mechanical properties of the provisional materials to be taken into account before choosing for clinical use. The objectives of the study were to evaluate and compare the flexural strength and surface hardness of heat polymerized provisional polymethylmethacrylate resin reinforced with 2.5% Zirconia, Titanium or Aluminum oxide nano-particles. According to ISO 10477:2018, die was made in 25 mm x 2 mm x 2mm for flexural strength and wheel die in 15 mm diameter and 1mm thickness for hardness test. A total of 160 samples were fabricated and divided into Groups. I- (samples kept in distilled water for 24 hours after fabrication) and Group. II (samples kept in artificial saliva for 2 weeks after fabrication) and subdivided into Group-a(control), samples reinforced with 2.5% Zirconia nanoparticle (Group b), samples reinforced with 2.5%Titanium oxide nanoparticles (Group c), samples reinforced with 2.5% Aluminum oxide nanoparticles (Group d). The flexural strength was evaluated by three-point bending test and the hardness was evaluated using digital Vickers micro hardness tester. The values were statistically analyzed using one way ANOVA and Tukey’s HSD test at significant level P&lt;0&gt; Keywords: Flexural strength, Heat activated PMMA resin, Provisional restoration, Surface hardness.

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

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

CAD/CAM Polimerlerinin (PEEK/PMMA) ve Geleneksel PMMA Materyallerinin Bazı Mekanik Özelliklerinin Değerlendirilmesi: İn Vitro Çalışma

Objective: The present study aims to investigate the mechanical properties of base materials [polymethyl methacrylate (PMMA)/polyether ether ketone (PEEK)] fabricated with computeraided design/computer-aided manufacturing (CAD/CAM) and heatpolymerized conventional base materials. Material and Methods: Two different base polymers milled with CAD/CAM (Yamahachi PMMA Disk and Juvora Dental Disk PEEK) and heat-polymerized acrylic resin (Meliodent PMMA) were used in this study. A total of 120 specimens were prepared with 10 specimens in each subgroup of the test materials. Half of the test specimens were stored in distilled water, while the other half were subjected to a thermal cycle. After the thermal cycle, the flexural strength, elasticity module, and, surface hardness of all test specimens was evaluated. The Mann-Whitney U and Kruskal-Wallis tests were used in the analysis of the data. Results: According to the findings of flexural strength and elasticity module of the test specimens, the highest to lowest value ranking was as follows: CAD/CAM PEEK>CAD/CAM PMMA>heat-polymerized PMMA. In the PMMA group produced with CAD/CAM, surface hardness values were significantly higher in the thermocycle applied test specimens compared to those stored in distilled water (p<0.001). Conclusion: CAD/CAM PMMA and PEEK materials were compared with the heat-polymerized test specimens found to show better mechanical properties.

Flexural Strength of CAD/CAM Denture Base Materials: Systematic Review and Meta-analysis of In-vitro Studies.

ABSTRACTIntroduction:Digital complete dentures fabrication techniques are expanding. This study aimed to review flexural strength (FS) of milled and 3D-printed denture base materials to answer the study question: is FS of computer-aided designing/computer-aided manufacturing (CAD/CAM) denture base comparable to conventional heat-polymerized materials?Materials and Methods:Search was done within different databases for articles published between January 2010 and June 2021 using specific keywords. Articles of in-vitro studies in English language with methods following International Standards Organization standardization/ADA specifications for flexural testing of conventional and CAD/CAM (milled or printed) polymethyl methacrylate (PMMA) materials were included.Results:Out of the 61 studies, 9 were processed for data extraction and only 7 underwent meta-analysis. Two, six, and one study showed high, moderate, and low risk of bias, respectively. Random-effects model was used for analysis and resulted in the average FS of 120.61 MPa [95% confidence interval (CI): 109.81−131.41] and 92.16 MPa (CI: 75.12−109.19) for CAD/CAM milled and heat-polymerized PMMA, respectively.Conclusion:Subtractive CAD/CAM technique of denture fabrication showed satisfactory FS values, whereas additive CAD/CAM method was comparable to conventional heat-polymerized technique with lower value, requiring further investigations and improvement. The clinical use of milled denture bases is an acceptable substitution to heat-polymerized PMMA, making the denture fabrication an easier and faster process.

Radiation attenuation properties of materials used to fabricate radiotherapy prostheses in vitro study.

This study investigates the attenuation of radiation doses by four materials, heat-polymerized, and self-polymerized polymethyl methacrylate (PMMA), putty-type, and injection-type polyvinyl siloxane (PVS) impression material. This in vitro study should aid in the selection of dental materials for radiotherapy prostheses, thereby minimizing the possibility of radiotherapy side effects. Specimens of each type were fabricated as a 5 × 5 cm squares with a thickness of 10 mm. Heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS impression material, and injection-type PVS impression material were selected. A calibration curve was created to determine the association of radiation doses and grayscale value. A linear accelerator was used to irradiate the specimens. The radiation doses above and below the materials were measured using radiochromic film dosimetry. After film irradiation, the pixel scale of color change was used to determine the radiation dose based on the created calibration curve. The results were exported to find average doses to calculate the percentage of the attenuated dose for a comparison of the four materials. The average attenuated doses of heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS, and injection-type PVS were 10.8%, 6.2%, 17.2%, and 14.2% respectively. PVS showed higher attenuating radiation exposure compared with PMMA.

Effectiveness of a Chairside Acrylic Adjustment Cabinet in Reducing Dental Acrylic Debris and Aerosols

AbstractPurposeChairside prosthesis adjustment procedures generate contaminated acrylic particle debris that include visible splatter (particles &gt;50 μm) as well as invisible aerosols (&lt;50 µm). The purpose of this study was to evaluate the effectiveness of a chairside acrylic adjustment cabinet (CAAC) in reducing airborne aerosol particles (&lt;10 µm) and visible acrylic debris, time required for airborne aerosols to return to baseline levels after an acrylic adjustment procedure, and the effect on operatory turnover time.Materials and methodsA total of 40 acrylic adjustment procedures were carried out in a simulated setting with (experiment) and without (control) a CAAC. Standardized acrylic samples of self‐polymerized, and heat polymerized polymethylmethacrylate resins, Triad™ and Fastray™ custom tray materials were evaluated. Airborne aerosol measurements were done using a handheld Lase.r Particle Counter for absolute particle counts of sizes 0.3, 0.5, 1.0, 2.5, 5.0, and 10.0 μm before, during, and immediately after adjustment and 10 minutes postadjustment. Spread of aerosols was assessed at three distinct locations within the dental operatory specific to the provider, the patient, and the caregiver/guest. Visible acrylic debris and operatory turnover time were evaluated immediately postadjustments by a blinded investigator. Repeated measures ANOVA was used to estimate group effect, time effect and interaction between group and time for air particle analysis. Independent samples T‐tests were used for group differences between operatory turnover time, and time for aerosols to return to baseline. Chi‐square test was used for visible surface analysis.ResultsIn the control group, total aerosol particle counts increased from 6542.7 ± 162.6 particles at baseline to 598378.7 ± 586363.2 and 367569.9 ± 432220.8 particles during and immediately postadjustment, respectively. Adjustments made in the experiment group led to significantly reduced aerosol counts during (97738.9 ± 97866.5) and immediately postadjustment (19786.5 ± 14004.9; F = 17.8, p = 0.006). Similar trends were noted for the patient and guest positions. Time for aerosol particles to return to baseline was significantly lower in the experiment group (20.56 ± 14.5 minutes) compared to the control group (37.9 ± 31.96 minutes; p = 0.03). Visible acrylic debris analysis showed a significant decrease of 78% in the experiment group (p &lt; 0.001). No significant differences were noted in operatory turnover time between the two groups (p = 0.61).ConclusionsAcrylic adjustment procedures generated aerosols of particle sizes less than 10 µm and were measured in significant quantities throughout the dental operatory for up to 115 minutes. Chairside acrylic adjustment cabinets significantly decreased airborne aerosols, visible acrylic particle debris, and reduced the time for airborne aerosols to return to baseline levels.

Effect of Low Nanodiamond Concentrations and Polymerization Techniques on Physical Properties and Antifungal Activities of Denture Base Resin.

Background: Denture base resin has some drawbacks. This study investigated the impact of nanodiamonds (ND) and autoclave polymerization on the surface characteristics, translucency, and Candida albicans adherence in polymethyl methacrylate (PMMA) denture base resin after thermocycling. Methods: Heat-polymerized PMMA discs (15 × 2 mm) with a total sample size n = 160 were studied. Specimens were categorized into two main groups (N = 80): conventional water-bath-polymerized PMMA (CP/PMMA) and autoclave-polymerized PMMA (AP/PMMA). Each group was subdivided according to the ND concentration into four groups (n = 20): unmodified PMMA as a control, and 0.1%, 0.25%, and 0.5% ND–PMMA. Scanning electron microscopy (SEM) was used to inspect the morphology of the ND and the ND–PMMA mixtures before heat polymerization. The specimens were exposed to thermal cycling (5000 cycles at 5 and 55 °C), then surface roughness was measured with a non-contact optical interferometric profilometer, contact angle with an automated goniometer, and translucency using a spectrophotometer. Colony-forming units (CFU) were used to determine the adherence of Candida albicans cells to the specimens. ANOVA and Tukey post hoc tests for pairwise comparison were utilized for the statistical analysis (α = 0.05). Results: Surface roughness was significantly reduced with ND addition to CP/PMMA (p ˂ 0.001), while the reduction was not statistically significant in AP/PMMA (p = 0.831). The addition of ND significantly reduced the contact angle, translucency, and Candida albicans count of CP/PMMA and AP/PMMA (p ˂ 0.001). The incorporation of ND in conjunction with autoclave polymerization of PMMA showed significant reduction in all tested properties (surface roughness, contact angle and Candida albicans adherence) except translucency (p = 0.726). Conclusions: ND addition to PMMA and autoclave polymerization improved the surface properties with respect to antifungal activities, while the translucency was adversely affected.

Evaluation and Comparison of the Effectiveness of Physical Methods of Disinfection on Heat-Polymerized Polymethyl Methacrylate – An In-vitro Study

Introduction: The common relationship of Candida and the ample proof that acrylic resin dentures are related to denture stomatitis in the oral cavity, which can range from simple mucosal lesions to a fatal systemic form. The current study aims to assess and compare the efficacy of microwave irradiation and UV radiation in the disinfection of Candida albicans infection in heat-polymerized polymethyl methacrylate.&#x0D; Materials and Methods: A total of 90 specimens were prepared with heat-polymerized acrylic resin, out of which 30 were used for Microwave irradiation, and 30 were used for UV irradiation, and 30 were used for positive control. There were three groups: Group A (Positive Control group); Group B (Microwave irradiation); Group C (UV radiation). After preparing the samples they were chemically sterilized, then infected with C. Albicans, and again Group B is disinfected with Microwave irradiation, Group C is disinfected by UV light and Group A is kept as Positive control without disinfection. Turbidity was measured for each group after re-infection of every specimen in CFU/ml.&#x0D; Results: In the present study, the CFU/ml of Candida albicans in the control group was 2.97x107±0.6 x 107 (P= .000), for microwave irradiation, the mean value was 5.3±11.1 (P= .000), and for UV radiation, the mean value was 19.3±22.9 (P= .003).&#x0D; Conclusion: According to the results of the current study, microwave irradiation (6 minutes at 650W) is more effective than UV radiation (10 minutes each side at 254nm wavelength) of Candida albicans infection on the heat-polymerized acrylic resin in laboratory conditions.