Heat-polymerized Acrylic Resin Research Articles

Impact of Polymerization Technique and ZrO2 Nanoparticle Addition on the Fracture Load of Interim Implant-Supported Fixed Cantilevered Prostheses in Comparison to CAD/CAM Material.

ZrO2 nanoparticles (ZNPs) have excellent physical properties. This study investigated the fracture load of implant-supported, fixed cantilevered prosthesis materials, reinforced with ZNPs and various polymerization techniques, compared with conventional and CAD/CAM materials. Sixty specimens were made from two CAD/CAM; milled (MIL) (Ceramill TEMP); and 3D-printed (NextDent Denture 3D+). Conventional heat-polymerized acrylic resin was used to fabricate the other specimens, which were grouped according to their polymerization technique: conventionally (HP) and autoclave-polymerized (AP); conventionally cured and reinforced with 5 wt% ZNPs (HPZNP); and autoclave reinforced with 5 wt% ZNPs (APZNP). The specimens were thermocycled (5000 cycles/30 s dwell time). Each specimen was subjected to static vertical loading (1 mm/min) using a universal Instron testing machine until fracture. Scanning electron microscopy was used for fracture surface analyses. The ANOVA showed significant fracture load differences between all the tested groups (p = 0.001). The Tukey post hoc tests indicated a significant difference in fracture load between all tested groups (p ˂ 0.001) except HP vs. HPZNP and AP vs. MIL. APZNP had the lowest mean fracture load value (380.7 ± 52.8 N), while MIL had the highest (926.6 ± 82.8 N). The CAD/CAM materials exhibited the highest fracture load values, indicating that they could be used in long-term interim prostheses. Autoclave polymerization improved fracture load performance, whereas ZrO2 nanoparticles decreased the fracture load performance of cantilevered prostheses.

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

To compare flexural strength, elastic modulus, and surface hardness of computer aided design and computer aided manufacturing CAD-CAM milled, 3D-printed, and heat-polymerized denture base resins. A total of 120 specimens were fabricated from heat-polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D-printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material (n = 20/material) (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3-point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795-1:2013 standards (64 × 10 × 3.3 ± 0.2 mm). The dimensions for hardness test were 15 × 10 × 2.5 ± 0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one-way ANOVA and Tukey post-hoc test (α = 0.05). Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP and then 3D-printed resins (p < 0.001). Withinmilled groups, flexural strength of AvaDent was significantly higher than IvoCad (p < 0.001), while elastic modulus and hardness didn't show significant difference. Within3D-printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (p = 0.595) and significantly with NextDent (p = 0.008). ASIGA also showed significantly the highest hardness among the 3D-printed groups. No significant difference was found between FormLabs and NextDent in flexural strength (p = 0.357), elastic modulus (p = 1.00), or surface hardness (p = 0.987). CAD-CAM milled resins had greater flexural properties and hardness compared to heat-polymerized acrylic resin and 3D-printed resins. Although 3D-printed samples showed the lowest values of tested properties, the flexural strength and modulus were above clinically acceptable values.

&lt;strong&gt;Effectiveness of green tea, bay leaf, and lime peel extracts as toothpastes active agents for extrinsic stain removal on teeth, artificial teeth, and denture base&lt;/strong&gt;

Introduction: Tea consumption causes extrinsic stain formation on teeth and denture surfaces, affecting personal appearance. Herbal plants extract such as green tea, bay leaf, and lime peel are potentially active agents for extrinsic stain removal. This study aimed to analyse the effectiveness of green tea, bay leaf, and lime peel extracts as toothpaste active agents for extrinsic stain removal on teeth, artificial teeth, and denture base. Methods: Twenty-five post-extracted human permanent central incisors, 25 artificial teeth, and 25 heat polymerised acrylic resin denture base (20x20x10mm) were divided into three treatment groups and two control groups. Pictures of all specimens were taken before and after stain induction and after brushing. All specimens were immersed in a tea solution made from 2 grams of tea and 100ml of 100°C boiled water to induce extrinsic stain. The immersion process was repeated every 24 hours for seven days. All specimens were then brushed using an automatic toothbrushing machine for 70 seconds on each surface, 200 grams loads, and five speeds/second. Toothpaste used for brushing were three different active agent toothpaste (treatment groups), no active agent toothpaste, and commercial whitening (control groups). Colour index analysis of the specimen pictures computerised by CIELAB method. The data were analysed by one-way ANOVA (α=0.05). Results: Green tea, bay leaf, and lime peel extract toothpaste and positive control had higher L-values of extrinsic stain removal than essential toothpaste on all specimens. There was a significant difference between green tea, bay leaf, and lime peel extract toothpaste and negative control toothpaste (p&lt;0.05), while no significant difference was found when compared to the positive control toothpaste (p&gt;0.05). Conclusion: Green tea, bay leaf, and lime peel extract toothpaste are effective as extrinsic stain removal on teeth and acrylic resin denture base because of abrasive materials that work together with the active agents such as epigallocatechin-3-gallate (EGCG) in green tea, eugenol in bay leaf, and naringin in lime peel.

The effect of photocatalyst effect of titanium dioxide anatase on heat polymerized acrylic resin plate towards the growth of Candida albicans colonies

Background: In general, removable denture are made from polymethyl methacrylate (PMMA) resin as the base material. This material has a drawback, namely that it is often attached to micro-organisms such as the fungus Candida albicans. Nanoparticle materials such as titanium dioxide (TiO₂) have antimicrobial properties, especially against C.albicans because it has photocata-lytic properties that can inhibit the growth of C.albicans colonies. Objective: To determine the effect of applying titanium di-oxide to heat polymerized acrylic resin (HPAR) plates towards the growth of C.albicans colonies. Methods: A true experimen-tal laboratory study using the HPAR plate as the object of research which was divided into the control group and the 1%, 2%, and 3% titanium dioxide-added groups. Data were analyzed using one-way Anova Welch. Results: There was an effect of add-ing titanium dioxide on the base of HPAR RD towards the growth of C.albicans colonies. Statistical tests showed significant re-sults (p=0.000; &lt;0.05)). In the test between the titanium dioxide 1%, 2%3% and control groups, there were significant diffe-rences. Conclusion: The application of titanium dioxide to the base of HPAR RD reduced the growth of C.albicans colonies.&#x0D;

Decrease in transverse strength of heat polymerized acrylic resin plate after immersion in 15% betel leaf extract (Piper betle Linn.)

The method of chemically cleaning dentures by immersion in an effervescent denture cleanser solution for a long time can affect the transverse strength. Betel leaf extract can be used as a natural disinfectant because it contains essential oils that are antimi-crobial by denaturing cell proteins. This study was intended to examine the decrease in the transverse strength of heat polymeri-rized acrylic resin plates after immersion in 15% betel leaf extract solution. The posttest only control group design study used a sample of 24 HPAR plates, which were divided into 6 groups. The plates were immersed in distilled water for 72 hours to re-duce the residual monomer, immersed in 15% betel leaf extract solution, the positive control group in Fittydent® and the nega-tive control group in aquadest for 1 and 6 hours. The transverse strength was tested using the Universal Testing Machine and the data were analyzed using the one-way Anova test. The results showed the average transverse strength after immersion for 1 hour in 15% betel leaf extract, Fittydent®, and aquadest, respectively, namely 46.512±10.965 MPa, 72.744±22.395 MPa, and 81.522±28.854 MPa; after soaking for 6 hours, respectively, namely 49.171±14.246 MPa, 73.894±25.844 MPa, and 71.860± 17.553 MPa. The LSD test showed that there was a significant difference in transverse strength (p&lt;0.05). It was concluded that the immersion of the HPAR plate in 15% betel leaf extract solution for 1 hour and 6 hours decreased the transverse strength.

The Impact of the Type and Concentration of Different Additives on the Water Sorption of Denture Base Resin

Aims: To evaluate the effect of incorporation of different types and concentrations of additives on water sorption denture base acrylic resin. Materials and Methods: Heat polymerized acrylic resin samples were prepared and divided into two groups; control group (without additives) and experimental group (with additives). The additives were three types of polymers (Styrene Butadiene Rubber (SBR), Poly Ethylene Glycol (PE) and Poly Urethane (PU)) being added with three concentrations 1%, 3% and 5%. SPSS Version 19 was used to analyze and to assess the results of the present study by mean of Descriptive statistics, analysis of Variance (ANOVA) and Duncan multiple range tests at p ≤0.05. Results: The results reveal that there is statistically significant reduction in the amount of water sorption of experimental group as compared to that of control group at p≤ 0.05. The reduction in the amount of water sorption of experimental group is directly proportional to the concentration of incorporate additives. Conclusions: Water sorption of experimental group is less than that of control group. The additives produce statistically significant reduction in the amount of absorbed water of denture base resin and this reduction was directly proportional to the concentration additives material being used.

Water Sorption, Solubility, and Translucency of 3D-Printed Denture Base Resins.

This study aimed to evaluate the water sorption, solubility, and translucency of 3D-printed denture base resins (NextDent, FormLabs, and Asiga), compare them to heat-polymerized acrylic denture base resins, and assess their performance under the effects of thermal cycling. A total of 80 acrylic disc specimens were used in the current study, categorized into four groups (n = 10); in one group, the samples were fabricated conventionally with a heat-polymerizing process (control), while the other three groups were fabricated digitally from different 3D-printed reins (NextDent, FormLabs, and Asiga). Specimens were fabricated according to the manufacturers’ recommendations and immersed in distilled water for 48 h at 37 °C. Data on water sorption, solubility, and translucency measurements (T1) were obtained. All the specimens were subjected to 5000 thermal cycles, and then the measures were repeated using the same method (T2). Data analysis was attained via ANOVA and the post hoc Tukey test (α = 0.05). The type of resin significantly affected the values of water sorption, solubility, and translucency (p < 0.001). The water sorption of 3D-printed resins was increased significantly in comparison to control with or without a thermal cycling effect. In terms of solubility, a significant increase in 3D-printed resins before thermocycling was observed; however, after thermocycling, Asiga had a significantly low value compared to the other groups (p < 0.001). Thermal cycling increased the water sorption and solubility of all tested materials. In comparison to control, the translucency of the 3D-printed resins was significantly decreased (p < 0.001). The translucency was significantly decreased per material in terms of the thermal cycling effect (before and after). NextDent showed significantly low translucency values (p < 0.001) compared to the other groups. All 3D-printed resin groups had higher water sorption and solubility and lower translucency values in comparison to the heat-polymerized resin group. Regardless of resin types, thermal cycling adversely affected all tested properties.

Comparison of shear bond strength of CAD/CAM and conventional heat-polymerized acrylic resin denture bases to auto-polymerized and heat-polymerized acrylic resins after aging

BackgroundThe aim of this study was to investigate the shear bond strength of CAD/CAM and conventional heat polymerized acrylic resin denture bases bonded to self-cured and heat-cured acrylic resins after aging. Material and MethodsA total of 40 cubic specimens were fabricated from conventional heat-polymerized and CAD/CAM denture base resins. Denture base resin specimens in each group were divided into two subgroups (n=10) in which they were bonded to either a heat-cured (HC) or a self-cured (SC) reline resin. Subsequently, the specimens were subjected to thermocycling. Then the shear bond strength (SBS) of specimens was measured using the universal testing machine. After testing, modes of failure were examined using light microscopy. The results were submitted to statistical analysis. ResultsMann-Whitney test showed that in each group of denture base materials, specimens bonded to HC reline resin had significantly higher SBS than those bonded to SC reline resin (P<0.001). Conventional denture base bonded to HC resin exhibited the highest value of SBS. There was no statistically significant differences between the SBS of HC reline resin bonded to conventional and CAD/CAM with regards to SBS (P=0.218). However, the SBS of SC reline resin was significantly higher when bonded to CAD/CAM compared to conventional denture base resin (P<0.001). ConclusionsHeat-cured reline resin showed higher shear bond strength to both CAD/CAM and conventional heat-polymerized denture resin in comparison to self-cured reline resin. Although there was no difference between the bond strength of heat-cured reline resin to CAD/CAM and conventional denture base, self-cured reline material produced stronger bond with CAD/CAM denture base. Key words:CAD/CAM, shear bond strength, reline, denture base resin.

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.

Antifungal Activities and Some Surface Characteristics of Denture Soft Liners Containing Silicon Dioxide Nanoparticles.

ABSTRACTObjective:This study aimed at determining the influence of adding silicon dioxide nanoparticles (nano-SiO2) to soft relining materials on C. albicans adhesion, surface roughness, and contact angle.Materials and Methods:Eighty heat-polymerized acrylic resin disks were constructed and relined by using auto-polymerized acrylic soft liners (COE-SOFT, GC Co., Tokyo, Japan). The specimens were categorized into two groups according to the tests conducted. Group A was composed of 40 specimens for evaluating antifungal activity, and Group B was composed of 40 specimens for testing surface roughness and contact angle. Each group was subcategorized into four subgroups (n = 10) according to the concentration of nano-SiO2 added to the soft-liner powder: control, 0.25%, 0.5%, and 1.0% by weight. The colony forming unit (CFU) was used to assess C. albicans count. A profilometer was used to measure the surface roughness values (Ra; μm). The sessile drop method was used to evaluate the contact angle (o) by using a goniometer. Analysis of variance and Tukey’s post hoc tests (α = 0.05) were used for the data analysis.Results:In comparison with the unmodified group, the 0.25% and the 0.5% nano-SiO2 groups exhibited significantly lower C. albicans counts (P < 0.001), surface roughness (P < 0.001), and contact angles (P < 0.001). The exception was the 1% group, which exhibited higher C. albicans count, surface roughness, and contact angles than lower-concentration nano-SiO2 groups; however, these values in the 1% group were still less than their respective values in the control group.Conclusion:The addition of 0.25% and 0.5% nano-SiO2 to an auto-polymerized acrylic soft liner decreased C. albicans adhesion, surface roughness, and contact angle.

PERBEDAAN JUMLAH KOLONI CANDIDA ALBICANS PADA RESIN AKRILIK DAN NILON TERMOPLASTIK DALAM PERENDAMAN EKSTRAK DAUN SIRSAK

Introduction: Denture stomatitis is a chronic inflammation caused by wearing dentures, mainly caused by Candida albicans. Heat-polymerized acrylic resins are often used as denture bases, but lack the ability to absorb liquids due to their porosity and surface roughness. The basis of the latest dentures is thermoplastic nylon because it is more aesthetically, hypoallergenic and more flexible. Soursop leaf extract contains alkaloids, tannins, flavonoids, and saponins as antifungal. The purpose of this study was to examinate whether there were differences in the number of Candida albicans colonies on heat-polymerized acrylic resin plates and thermoplastic nylon in soursop leaf extract immersion. Materials and Methods: The research design was an experimental pre-post test with control group design, n = 50 plates were divided into 2 groups, heat-polymerized acrylic resin (n=25) and thermoplastic nylon (n=25), divided into 5 groups, 3 treatment groups using 10%,15%,25% soursop leaf extract, Fittident®and aquadest in the control groups. Samples were contaminated with Candida albicans suspension and incubated, counted before immersion for 8 hours, then put in Saboroud’s bath and counted again. Results and Discussions: Wilcoxon test analysis showed significant differences in all groups, except the aquadest group. The Mann-Whitney test showed significant differences between the treatment groups, except between the 25% extract and the Fittident®control group. Also, showed a significant difference in the 15% concentration group between heat-polymerized acrylic resin and thermoplastic nylon. Conclusion:There was a difference in the decrease in the number of Candida albicans colonies on heat-polymerized acrylic resin plates and thermoplastic nylon in soursop leaf extract at a concentration of 15%, while at concentrations of 10% and 25% there was no difference

Antifungal Effects of Herbal Extracts and Fluconazole on Heat-polymerized Acrylic Denture Base Resin as Denture Cleanser: An In Vitro Study

The study aimed to investigate the antifungal effects of herbal extracts and fluconazole on heat-polymerized acrylic denture base resin as a denture cleanser. Several essential oils, such as origanum oil and grape seed oil and commercially available antifungal agent fluconazole were used as denture cleansers and their antifungal efficacy was evaluated using a spectrophotometer. Overall, 68 samples were obtained and were divided into four groups, each containing 17 samples. These samples were immersed in Sabouraud dextrose broth consisting of Candida albicans for 16 hours and later in these antifungal solutions for 8 hours and their antifungal efficacy was measured. Data were subjected to an ANOVA test. Among the study groups origanum oil showed the maximum antifungal activity with a mean optical density at 0.072 ± 0.014 followed by fluconazole (0.094 ± 0.155), and least by grape seed oil (0.190 ± 0.071). Results of this in vitro study showed that origanum oil was more effective than commercially available antifungal agents, and among the tested groups oregano oil was a potential agent in lowering the C. albicans colony. Origanum oil, being a herbal product, can be considered as a denture cleanser and also be used as an effective alternative to commercially available antifungal agents without any side effects.

Comparative Analysis of Abrasive Materials and Polishing System on the Surface Roughness of Heat-Polymerized Acrylic Resins.

Objective The aim of this in vitro experiment was to see how the operator's manual skills, polishing equipment, and abrasive materials affected the surface roughness of denture base resins. Materials and Methods Forty polymethyl methacrylate (PMMA) specimens were created and polished by using two different polishing systems, namely hand and automatic polishing machines. Three operators hand-polished 30 of specimens with eggshell powder and pumice, while 10 were automatically polished ( n = 5). A profilometer was used to determine the average surface roughness (Ra) after polishing. The Ra values for the specimens hand-polished were analyzed by using paired sample testing. The Ra values for all polished specimens were analyzed by using a one-way ANOVA. Differences between the two abrasive materials as well as the polishing system were determined by using the Bonferonni tests ( p = 0.05). Results and Conclusion For the PMMA specimens hand-polished, there was a strong connection in the Ra values. There were also significant variations in the Ra values across the three operators ( p < 0.001). The automated technique created a substantially smoother surface than the traditional technique ( p = 0.001). The greatest Ra values (0.20 µm) were found in specimens polished traditionally by using pumice, whereas the lowest Ra values (0.04 µm) were found in specimens polished mechanically with eggshell powder. The automated polishing system was the most effective polishing method when the Ra values were connected to the level of smoothness.

Evaluation Flexural Strength of PMMA Resins with the Addition of Nanoparticles

The flexural strength of heat cure acrylic resin was investigated by adding different concentrations of TiO2 and ZrO2 nanoparticles to increase its mechanical properties. ZrO2 and TiO2 nanoparticles were added at 1, 3, and 5% concentrations to the powder portion of heat polymerized acrylic resins. A total of 49 samples were prepared in 65 × 10 × 3 mm size. The structural characterisations of all experimental groups were determined by Fourier transform infrared spectroscopy. Flexural strength of the resin specimens was evaluated with a three-point bending test in a universal test machine and then examined under by scanning electron microscope to assess its topographic characteristics. The highest flexural strength value was obtained for 3% TiO2, while the lowest values were obtained for 1% and 5% TiO2. 1% ZrO2 and 3% TiO2 groups showed statistically higher flexural strength values than the control group. The addition of 3% and 5% ZrO2 and 1% and 5% TiO2 showed statistically lower flexural strength than the control group. The addition of ZrO2 and TiO2 nanoparticles for strengthening acrylic resin is directly related to the amount of concentration. The addition of 1% ZrO2 and 3% TiO2 is recommended to strengthen heat cure acrylic resin due to its high flexural strength values.

Polymethylmethacrylate Incorporating Nanodiamonds for Denture Repair: In Vitro Study on the Mechanical Properties.

Objective This study aimed to evaluate the effect of nanodiamond (ND) addition to repair resin with repair gap modifications on the flexural and impact strength of repaired polymethylmethacrylate denture base. Materials and Methods Heat-polymerized acrylic resin specimens ( N = 100/test) were prepared and sectioned to half creating two repair gaps: 2.5- and 0 mm with 45 degrees beveling. They were further divided into subgroups ( n = 20) according to ND concentration (control, 0.25%ND, and 0.50%ND), thermocycling (500 cycles) was done to half the specimens in each subgroup. Flexural strength was tested using 3-point bending test and impact strength was tested by Charpy's impact test. Analysis of variance and post-hoc Tukey's tests were performed for data analysis ( α = 0.05). Scanning electron microscope was employed for fracture surface analysis and ND distribution. Results Before and after thermocycling, the addition of ND significantly increased the flexural strength and elastic modulus in comparison to control group ( p ˂ 0.001), while 0 mm repair gap showed insignificant difference between ND-reinforced groups ( p ˃ 0.05). Regarding impact strength, ND addition increased the impact strength with 0 mm gap in comparison to control and 2.5 mm with ND ( p ˂0.001), while later groups showed no significant in between ( p ˃ 0.05). Comparing thermocycling effect per respective concentration and repair gap, thermocycling adversely affected all tested properties except elastic modulus with 0 mm–0.25 and 0 mm–0.5% and impact strength with 2.5 mm, 2.5 mm–0.25%, 2.5 mm– 0.5% ( p ˃ 0.05). Conclusion ND addition combined with decreased repair gap improved the flexural strength, elastic modulus, and impact strength of repaired denture resin, while thermocycling has a negative effect on denture repair strength.

Influence of Different Beverages on the Color Stability of Nanocomposite Denture Base Materials.

Background The effect of beverages on nanocomposite denture base materials is neglected. Therefore, this study aimed to investigate the influence of different beverages (coffee, tea, cola, and mineral water) on the color stability of nanoparticles-modified denture base materials (DBMs). Materials and Methods A total of 280 specimens (n = 10/group) were prepared from heat-polymerized acrylic resin modified with different concentrations (3% and 7%) of zirconium dioxide (nano-ZrO2), titanium dioxide (nano-TiO2), and silicon dioxide (nano-SiO2) nanoparticles, while 0% was taken as a control. Color change (∆E) of the specimens was evaluated after simulating 6-month immersion time in four commonly used beverages, coffee, tea, cola, and mineral water, as experimental groups. Color stability was measured using a spectrophotometer, and then values were converted to National Bureau of Standards units (NBS units). The one-way ANOVA test was applied to compare color change (ΔE) results followed by Bonferroni's post hoc test (α = 0.05). Results The results showed that the heat-polymerized acrylic resin modified with different types of nanoparticles showed lower color changes after being immersed in beverage solutions compared to the unmodified group (P < 0.001), so the color stability of heat-polymerized acrylic resin was significantly enhanced by the addition of several nanoparticles; nano-ZrO2 showed the lowest ΔE followed by nano-TiO2 and then nano-SiO2. Regardless of the filler type, 3% concentration showed lower mean ΔE than 7% concentration. Regarding the beverage solutions, the greatest color change was found in the coffee group followed by tea and cola, while water showed the least changes. Conclusion Modification of heat-polymerized acrylic resin with certain amounts of nano-ZrO2, nano-TiO2, and nano-SiO2 may be useful in improving color stability.

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.

3D-Printed vs. Heat-Polymerizing and Autopolymerizing Denture Base Acrylic Resins.

The aim of this work was to investigate the effect of two post-curing methods on the mechanical properties of a 3D-printed denture base material. Additionally, to compare the mechanical properties of that 3D-printed material with those of conventional autopolymerizing and a heat-cured denture base material. A resin for 3D-printing denture base (Imprimo®), a heat-polymerizing acrylic resin (Paladon® 65), and an autopolymerizing acrylic resin (Palapress®) were investigated. Flexural strength, elastic modulus, fracture toughness, work of fracture, water sorption, and water solubility were evaluated. The 3D-printed test specimens were post-cured using two different units (Imprimo Cure® and Form Cure®). The tests were carried out after both dry and 30 days water storage. Data were collected and statistically analyzed. Resin type had a significant effect on the flexural strength, elastic modulus, fracture toughness, and work of fracture (p < 0.001). The flexural strength and elastic modulus for the heat-cured polymer were significantly the highest among all investigated groups regardless of the storage condition (p < 0.001). The fracture toughness and work of fracture of the 3D-printed material were significantly the lowest (p < 0.001). The heat-cured polymer had the lowest significant water solubility (p < 0.001). The post-curing method had an impact on the flexural strength of the investigated 3D-printed denture base material. The flexural strength, elastic modulus, fracture toughness, work of fracture of the 3D-printed material were inferior to those of the heat-cured one. Increased post-curing temperature may enhance the flexural properties of resin monomers used for 3D-printing dental appliances.

Evaluation of adaptation of different resins to secure implant supported over denture housings: A scanning electron microscopic study

Eighty heat polymerized polymethyl methacrylate (PMMA) denture base specimens (30×11×8mm) were prepared. Four materials used to retain the housings in the PMMA denture base blocks were autopolymerizing acrylic resin, composite resin, pattern resin and heat polymerizing acrylic resin. The PMMA block containing housing was then seated on a ball abutment-implant analog. Universal testing machine was used to detach the acrylic block-housing assembly from the ball abutment implant analog assembly. Scanning electron images were made to inspect the PMMA denture base-retaining material-housing interfaces for any adhesive failure. Chi square test was used to compare the results of SEM analysis. Highest percentage of adhesive failure of 55% was found in the composite resin group (Group B) at the acrylic denture base-housing retaining material junction (junction 1). Heat polymerizing acrylic resin group (Group D) exhibited 100% adhesive failure at the retaining material-housing junction (junction 2).

Fibre-reinforced and repaired PMMA denture base resin: Effect of placement on the flexural strength and load-bearing capacity

ObjectivesTo measure the effect of placement of glass fibre mesh on the flexural strength and load bearing capacity of repaired polymethylmethacrylate (PMMA) denture base resin. Materials and methodsA total of 150 heat-polymerised acrylic resin specimens were fabricated with dimensions of 5 × 30 × 50 mm for flexural strength testing. Specimens were divided into 5 groups according to repair width and placement of the fibre mesh. Three groups (n = 90) had a repair width of 20 mm (including the control group), and two groups (n = 60) had a narrower repair width of 16 mm. Fibre mesh was either embedded at the neutral (bottom of the repair area) or tension (top of the repair area) zone of the specimen when subjected to flexural strength testing. Half of the specimens from each group were subjected to artificial ageing by thermocycling (5 °C and 55 °C, 30s dwell time) for 10,000 cycles to stimulate 12 months in vivo. All the specimens were stored in distilled water at 37 °C for 24 h prior to testing. The flexural strength of the specimen was obtained by three-point bend testing, and data were statistically analysed using ANOVA and post-hoc analysis (SPSS; significance level p < 0.05). Probability of failure was calculated using Weibull analysis. Scanning electron microscopy analysis was used to identify the mode of failure. ResultsSpecimens repaired with the 20 mm fibre mesh placed in the tension zone showed the highest mean flexural strength (101.33 ± 12.66 MPa) with statistical significance (p = 0.05) to the other groups except for the specimens repaired with the 16 mm fibre mesh placed in the tension zone (p = 0.072). The highest Weibull modulus was found in the thermal cycling group of the specimens with 20 mm repair width repaired with the fibre mesh embedded at the neutral zone (10.01). The lowest Weibull modulus was found in the non-thermal cycling group of the control group (3.15). ConclusionPlacing fibre mesh in the tension zone of a PMMA specimen significantly improved the flexural strength of the repair. Placing the fibre mesh in the neutral zone or the fibre mesh width was short of the lower support rollers resulted in no significant increase in flexural strength compared to the non-reinforced control group. Ageing via thermal cycling resulted in a decrease in flexural strength across all sample groups. This study highlights the importance of recognising the valid repair region and to have the mesh embedded in certain dimensions, otherwise it will have no significant contribution towards the repair and increase of flexural strength of the denture.