Acrylic Specimens Research Articles

Complete denture hygiene solutions: antibiofilm activity and effects on physical and mechanical properties of acrylic resin.

Appropriated denture hygiene is a predictive factor for longevity of rehabilitation treatment and maintenance of the oral mucosal health. Although, disinfectant solutions are commonly used as denture cleansers, the impact of these solutions on acrylic resin-based dentures remain unclear. Objective To evaluate, in vitro, the antibiofilm activity of complete denture hygiene solutions and their effects on physical and mechanical properties of acrylic resin.Methodology For antibiofilm activity measurement acrylic resin specimens were contaminated with Candida albicans, Candida glabrata and Streptococcus mutans. After biofilm growth, the specimens were assigned to the hygiene solutions: Distilled water (Control); 0.2% Sodium hypochlorite (SH); Efferdent Power Clean Crystals (EPC) and 6.25% Ricinus communis (RC). The viability of microorganisms was evaluated by agar plate counts. In parallel, physical, and mechanical properties of the acrylic resin were evaluated after simulating a 5-year period of daily immersion in the previously mentioned solutions. The changes in surface roughness, color, microhardness, flexural strength, impact strength, sorption and solubility were evaluated. Data were compared by ANOVA followed by the Tukey test or Kruskal-Wallis followed by the Dunn test depending on the distribution (α=0.05).Results Regarding antibiofilm action, SH eliminated all microorganisms while EPC and RC exhibited moderate action against S. mutans (p=0.001) and C. glabrata (p<0.001), respectively. Relative to effects on the physical and mechanical properties of the acrylic resin, RC led to higher values of color change (p=0.030), hardness (p<0.001), surface roughness (p=0.006) and flexural strength (p<0.001). Moreover, RC induced the highest values of changes in solubility (p<0.001). EPC promoted greater changes in surface morphology, whereas immersion in SH retained the initial appearance of the acrylic resin surface. All hygiene solutions reduced the impact strength (p<0.05).Conclusion SH presented the most effective antibiofilm activity. In addition, changes on properties were observed after immersion in RC, which were considered within acceptable limits.

Action of disinfectant solutions on adaptive capacity and virulence factors of the Candida spp. biofilms formed on acrylic resin

Understanding the behavior of Candida spp. when exposed to denture disinfectants is essential to optimize their effectiveness. Changes in the virulence factors may cause increased resistance of Candida spp. to disinfectant agents. Objective To evaluate the microbial load, cellular metabolism, hydrolytic enzyme production, hyphae formation, live cell and biofilm quantification of Candida albicans, Candida tropicalis and Candida glabrata after exposure to disinfectant solutions.Methodology Simple biofilms were grown on heat-polymerized acrylic resin specimens, and divided into groups according to solutions/strains: distilled water (control); 0.25% sodium hypochlorite (NaOCl 0.25% ); 10% Ricinus communis (RC 10%); and 0.5% Chloramine T (CT 0.5%). The virulence factors were evaluated using the CFU count (microbial load), XTT method (cell metabolism), epifluorescence microscopy (biofilm removal and live or dead cells adhered), protease and phospholipase production and hyphae formation. Data were analyzed (α=0.05) by one-way ANOVA/ Tukey post hoc test, Kruskal-Wallis test and Wilcoxon test.Results NaOCl 0.25% was the most effective solution. CT 0.5% reduced the number of CFUs more than RC 10% and the control. RC 10% was effective only against C. glabrata. RC 10% and CT 0.5% decreased the cellular metabolism of C. albicans and C. glabrata. Enzyme production was not affected. Hyphal growth in the RC 10% and CT 0.5% groups was similar to that of the control. CT 0.5% was better than RC 10% against C. albicans and C. tropicalis when measuring the total amount of biofilm and number of living cells. For C. glabrata, CT 0.5% was equal to RC 10% in the maintenance of living cells; RC 10% was superior for biofilm removal.Conclusions The CT 0.5% achieved better results than those of Ricinus communis at 10%, favoring the creation of specific products for dentures. Adjustments in the formulations of RC 10% are necessary due to efficacy against C. glabrata. The NaOCl 0.25% is the most effective and could be suitable for use as a positive control.

An in vitro evaluation of tensile bond strength of soft liners bonded to different denture base resins.

Background:Clinically, adhesion failure is the most critical problem because of the failure of the optimal bond between denture base and the soft liner.Objectives:This study was performed to assess the tensile bond strength of two temporary soft liners to different denture base resins.Materials and Methods:Forty-eight blocks with 16 samples each of heat-cured denture base resin of three different types were fabricated from custom-made stainless steel die after de-waxing mold space. Surface roughening of each acrylic resin specimens which bonds with soft liners was done by abrading the surface and to this temporary soft liners (Perma soft denture liner and Pro soft denture liner) were bonded. The universal testing machine was used to test the tensile strength of bonded space. The results were statistically analyzed using the Statistical Software IBM SPSS Statistics for Windows, version 20.0. (Armonk, NY, USA: IBM Corp.) using the Chi-square test, Post hoc Tukey's HSD, and two way ANOVA tests.Results:It was observed that Perma soft was prevalent over Pro-soft denture liner on the basis of tensile bond strength with all three different types of denture base resins. Trevalon HI and acrylic composite exhibited better bond strength results with both Perma soft and GC Pro-soft denture liner as compared to other types of denture base resins.Conclusion:Perma soft had a better bond strength compared to Pro-soft denture liner in bonding modified denture base and conventional resins.

THE EFFECT OF AUTOCLAVE POLYMERIZATION ON THE TENSILE STRENGTH OF VARIOUS DENTURE BASE MATERIALS

Objectives: The aim of this in vitro study was to evaluate the effect of autoclave polymerization method on the tensile strength of the polymethylmethacrylate (PMMA) acrylic denture base resins. Materials and Methods: Total of 60 specimens were fabricated from four different denture base materials such as three heat polymerized dental resins Meliodent, Paladent, and QC-20 and one microwave polymerized resin Acron MC. The tensile strength tests were performed. Results: Acron-MC showed the highest tensile strength value, QC-20, Paladent and Meliodent were followed in order for the control group. Acron MC was significantly different than the other acrylic resins for the control and autoclave polymerization 10 minutes groups (p&amp;lt;0.01). Autoclave polymerized acrylic resin specimens showed higher tensile strength values than the control groups (p&amp;lt;0.01). There was no significant difference between the increasing time of autoclave polymerization methods 10 minutes and 20 minutes (p&amp;gt;0.01) Conclusion: Within the limitations of the study, autoclave polymerization method may provide a stronger alternative to conventional polymerization methods. Autoclave polymerization method provides high temperature that the activation ratio of cross-linking agents (glycoldimethacrylate) can be increased.

Avaliação de soluções antifúngicas de guanidina para resina base de dentadura: um estudo in vitro

Background: The purposes of this study were: (1) to formulate polyhexamethylene guanidine hydrochloride (PHMGH) solutions at different concentrations; (2) to evaluate their antifungal activity against a mature biofilm of Candida albicans on acrylic resins; (3) to evaluate possible effects on acrylic resins flexural strength and surface roughness. Methods: PHMGH solutions were formulated with distilled water and 0.125, 0.250, or 0.5 wt.% of PHMGH. One group without PHMGH was used as control. For antifungal activity analysis, acrylic resin specimens were contaminated with C. albicans. Specimens were immersed in PHMGH solutions or distilled water for 5 or 10 min. Ultimate flexural strength and surface roughness of acrylic resins were evaluated. Results: All PHMGH solutions at 5 or 10 min showed antifungal activity compared to the control group (p

Effect of Some Disinfectant Solutions on the Adherence of Candida albicans to Three Types of Acrylic Resin Denture Base Materials

Objective: Microbial adhesion to denture surface is problematic for denture wearers, especially those with impaired dexterities. This study aimed to evaluate the effectiveness of two plant extracts (clove and Basil) in addition to Chlorhexidine on candida Albicans adherence to (heat, cold, light) activated acrylic denture base materials. &#x0D; Methods: Two herbal extracted clove (Eugenia caryohyllata) and Basil (Ocimum basilicum) were prepared by drying, ground to powder, and extracted with ethanol chlorhexidine gluconate of 0.12% were used as three disinfectant solutions. One hundred and five square acrylic samples were prepared from (heat, cold, and light) activated acrylic resin denture base materials in dimensions of 10×10×2 mm for the study. The disk diffusion test was used to determine the susceptibility of C. Albicans to disinfectant solutions. The adhesion of yeast to the acrylic resin samples was measured with a light microscope by measuring the number of fungal cells in the corners of the square and expressed as no. of cells/mm2. Statistical analysis was done by ANOVA to compare the mean of readings between disinfectant solutions and post-hoc t-test in which the p-value is less than 0.05.&#x0D; Results: Statistically significant differences (p&lt;0.05) of adhesion of C.albicans were found on the surfaces of three types of activated acrylic resin materials with means of 19.18, 46.25, and 26.50 cell/mm2on heat, light, and cold cure respectively and after immersing the specimens on the disinfectant solutions regarding the highest effect of the disinfectant solutions was seen in chlorhexidine gluconate of 0.12% which demonstrate 3.11, 5.89 and 5.43 cell/mm2 followed by Basil with means of 6.75, 13.57 and 10.11 cell/mm2 on heat, light and cold cure acrylic resin specimens correspondingly, then the clove and finally distilled water. &#x0D; Conclusions: Both clove buds and basil leaves extracted solutions exhibited high antifungal activity besides Chlorhexidine on the surface of denture base materials. The highest inhibition zone was seen in Chlorhexidine, followed by Basil, clove, and distilled water, respectively. The number of fungal cell adhesion to the three types of denture base was decreased in the three disinfectant solutions when compared to distilled water (control group).

Antagonistic effect of isolated and commercially available probiotics on the growth of Candida albicans on acrylic resin denture surfaces

Statement of problemBiofilms can be retained on dental prostheses leading to the development of infections. The indiscriminate use of antifungal drugs can result in the development of microorganisms that are resistant to these antimicrobial agents. Whether probiotics are a suitable alternative for reducing the prevalence of oral candidiasis is unclear. PurposeThe purpose of this in vitro study was to evaluate the influence of 6 different live strains of probiotics and 2 commercially available probiotic supplements used for inhibiting the growth of Candida albicans biofilm in heat-polymerized acrylic resin denture base material and to determine whether biofilm byproducts modify the surface of specimens. Material and methodsBiofilms of C. albicans were formed on acrylic resin specimens in the presence of probiotics and quantified by colony-forming units (CFUs), and the surface roughness (Ra) of the specimens was assessed before and after the formation of biofilms. The CFU and roughness data were analyzed by analysis of variance and the Tukey HSD test (α=.05). ResultsA significant decrease in the number (CFU/mL) of C. albicans cells was found when they were cultured with 4 probiotics: B. lactis (P=.045), B. longum (P<.001), L. casei (P<.001), and L. helveticus (P<.001) and with the commercially available probiotic Prolive (P=.05). The Ra of specimens decreased after exposure to different microbial biofilms (P≤.05) except in 3 experimental groups. ConclusionsIn general, the tested probiotics had an antagonistic effect on the growth of C. albicans, and the surface of acrylic resin was altered after exposure to biofilm byproducts.

Development of a Weight-Drop Impact Testing Method for Dental Applications.

For evaluating the impact strength of dental materials, the Izod test or Charpy test has been used, but specimen preparation for these tests is difficult due to the adjustment of a notch on them. By contrast, a weight-drop impact test does not require notched specimens. Therefore, it might be possible to measure the impact strength more accurately than conventional methods. This study aimed to establish appropriate conditions for applying the weight-drop impact test on small specimens of acrylic resin. To determine the most reliable impact fracture energy of acrylic resins, different diameters and thicknesses of PMMA resin specimens, diameters and weights of the striker, and diameters of the supporting jig were compared. For all specimen thicknesses, when the striker diameter was 6–10 mm, the impact fracture energy was constant when the inner diameter of the specimen-supporting jig was 8–10 mm. In addition, the measured E50% value was mostly equal to the median value of the impact fracture energy. Thus, for the weight-drop impact test, this method was effective for material testing of small specimens, by clearly specifying the test conditions, such as the thickness of disc-shaped specimens, the diameter of the striker, and the inner diameter of the specimen-supporting jig.

Double-layered acrylic resin denture base with nanoparticle additions: An in vitro study

Statement of problemWhether the addition of different antifungal nanoparticles to denture base materials may affect physical or esthetic properties of the resulting nanocomposite is unclear. PurposeThe purpose of this in vitro study was to determine how a new method of adding antifungal nanofiller affects the properties of the processed nanocomposite denture base material. Material and methodsHeat-polymerized acrylic resin specimens were prepared according to each test specification. Zirconium dioxide nanoparticles (ZrO2NPs) and silver nanoparticles (AgNPs) were added in 0.5, 1.0, and 1.5% of acrylic resin powder. The specimens were divided into 2 groups according to the acrylic resin packing method: 1 layer packed conventionally in one step and 2 layers packed in 2 steps, first with unmodified acrylic resin and then by a thin layer of modified acrylic resin before the final closure. The control group was made of unaltered acrylic resin in 1 step. Flexural strength (FS), translucency, and surface roughness (Ra) were measured. A microbial assay was performed by using the direct culture and slide count methods. Three-way ANOVA and Tukey post hoc tests were used to identify statistical differences among groups (α=.05). ResultsThe addition of ZrO2NPs and AgNPs in the 1- or 2-layer specimens reduced Candida albicans adhesion (P<.001). In the 1- and 2-layer specimens, FS significantly increased with ZrO2NPs. AgNPs decreased FS only in the 1-layer specimen (P<.001). Surface roughness was not changed for the 1- and 2-layer specimens with ZrO2NPs or the 1-layer specimen with 0.5% AgNPs (P>.05), while other AgNP groups exhibited increased surface roughness (P<.001). AgNPs significantly lowered translucency in the 1- and 2-layer specimens (P<.001), while ZrO2NPs decreased translucency only in the 1-layer specimen (P<.001). ConclusionsThe addition of ZrO2NPs in the double-layer technique decreased Candida adhesion and improved FS without affecting surface roughness, while AgNPs decreased Candida adhesion and FS and increased surface roughness. Both nanofillers decreased the translucency except 0.5% ZrO2NPs, which did not change translucency when applied in 2 layers.

Effect of Cleanser Solutions on the Retention Force of O'ring Attachment: An in Vitro Study.

The aim of this study was to evaluate the effect of cleaning solutions on the retention force of o-ring-type overdenture attachments. The effect of four solutions on nitrile rings were evaluated: Cepacol (C), Cepacol with fluoride (CF), Listerine (L) and 0.05% sodium hypochlorite (SH); deionized water (DW) was used as a control. Matrices containing two implants and abutments and acrylic specimens with the metal capsules were obtained and divided into the groups. A simulation of 90 overnight immersions (8 h) was performed, and the tensile strength value was obtained at the beginning (T0) and in every 30 days (T1, T2 and T3) (n=6). In order to analyze o-ring surface damage after the immersions, a scanning electron microscopy (SEM) was used (n=1). For statistical analysis of the results, analysis of variance (ANOVA) and multiple comparisons with Bonferroni adjustment (test power=1.000; a=0.05) were used. There was a significant difference for the factors time (p<0.001), solution (p<0.001) and for the interaction time × solution (p<0.001). Considering the times of each solution, only for DW there was no significant loss of retention over time. Comparing the solutions in each moment, there was no difference among the solutions in T0. From T1, CF and SH provided less retention than DW (p<0.005). Through SEM it was possible to observe changes in the surface of the CF and SH nitrile o-rings. CF and SH should be avoided due to deleterious action in o-rings.

Surface Microstructure Study of Self Cured Acrylic Resin after Immersion in Arabica Gayo Coffee

The water absorption on self-cured acrylic resin is higher than the heat cured acrylic resin. Incoming water positions itself between the polymer chains and affects the surface microstructure of self-cured acrylic resin. The absorption of liquids such as Arabica Gayo coffee may aggravate the surface structure of self-cured acrylic resins due to their acid content. This study aims to find out the microstructure of self-cured acrylic resin surface after immersed in Arabica Gayo coffee for 2 and 7 days. This study used 5 specimens of self-cured acrylic resin (MeliodentTM) with size 10x10x1,5 mm3. Each specimen was immersed in aquades for 24 hours to reduce the residual monomer and then be given different immersion treatments. The immersion temperature used was 55°C. After immersion, surface microstructure observation was done using Scanning Electron Microscope (JEOL JSM 6510 LA). The images obtained were bubbles after being immersed in aquades for 2 days and more on day 7, micro porous after being immersed in Arabica Gayo coffee for 2 days and more on day 7 than untreated specimens. The conclusion of this study is micro porous formed more on the surface of self-cured acrylic resin along with the duration of self-cured acrylic resin immersion in Arabica Gayo coffee.

Experimental and numerical investigation of difference in diameter enlargement and circularity of micro-holes drilled by flexural spindle head

The flexural bearing or the flexural cartridge allows very nano-meter axial displacement movement, which is frictionless and noiseless. The repeatability of the mechanism obtained is achieved by bending of the load element. The bearing can operate under stringent conditions such as vacuum, elevated temperatures (0–40 °C), and moist conditions. Hence, due to these indigenous properties, these bearings are observed in applications such as linear bearing of linear compressor, flexural bearing electromagnetic linear actuator, and parasitic error-free mechanism. The endorsed capability of obtaining high-level positional accuracy along with repeatability leads to design and development of low-cost flexural cartridge for micro-drilling spindle head. This flexural cartridge provides a linear guideway while feeding inside the test specimen (in micro-drilling operation). The designed head dampens and nullifies the force, acting on the shaft carrying the micro-tool. The designed spindle head carrying the three-leg spiral flexural stack is assembled on the designed machine tool. The run out measured on the spindle shaft is 50 µm. Four test specimens, namely aluminum, brass, acrylic and mild steel, are drilled by three drills of diameter 1 mm, 0.8 mm, and 0.5 mm each. The main objective of the article is to understand the differential analysis of diameter enlargement and circularity between the experimental method and the numerical method. The answers predicted by the experimental method may have second possible value as it depends upon judgment of inscribing the circle/points in the computer-aided design (CAD) environment. This ambiguity is excluded by the MATLAB code, which gives one specific answer. The maximum difference in diameter enlargement for aluminum, brass, acrylic, and mild steel specimens are 3.8 µm, 11 µm, 24.6 µm, and 16.1 µm, respectively, whereas the maximum difference in circularity for the same specimens is 11.8 µm, 1.3 µm, 8.2 µm, and 16.8 µm, respectively. This difference is termed as the |error|.

Antifungal Efficacy and Physical Properties of Poly(methylmethacrylate) Denture Base Material Reinforced with SiO2 Nanoparticles.

To evaluate the effect of the addition of low concentration of silicon-dioxide nanoparticles (nano-SiO2 ) to poly(methylmethacrylate) (PMMA) denture base material on Candida albicans adhesion, surface roughness, contact angle, hardness, and translucency. A total of 150 acrylic disks were fabricated from heat-polymerized acrylic resin and specimens were divided into 3 groups of 50 per test. They were further subdivided into 5 subgroups (n = 10) according to the concentration of nano-SiO2 : control (no addition) and four tested groups modified with 0.05, 0.25, 0.5, and 1.0 wt% nano-SiO2 of acrylic powder. Slide count and direct culture methods were used to measure C. albicans count (CFU/mL). The surface roughness values (Ra ; μm) were determined using a profilometer. The contact angle (o ) measurement was performed by a goniometer using the sessile drop method. Vickers hardness was used to analyze surface hardness. Translucency was measured using a spectrophotometer. Data analysis was conducted through analysis of variance and Tukey's post hoc tests (α = 0.05). Compared to the control group, direct culture and slide count methods illustrated a significant decrease in C. albicans count (p ˂ 0.001) with the addition of nano-SiO2 , and this decrease was correlated with the concentration of nano-SiO2 . The addition of nano-SiO2 significantly decreased the contact angle (p ˂ 0.001), whereas hardness and surface roughness significantly increased (p ˂ 0.001). The addition of nano-SiO2 significantly decreased translucency (p ˂ 0.001), and this decrease was concentration dependent. Addition of low concentration of nano-SiO2 decreased C. albicans adhesion to PMMA denture base resin. Also, low additions of nano-SiO2 have positive effects on contact angle and hardness, whereas surface roughness and translucency were adversely affected at high concentrations.

Effect of aluminum oxide powder reinforcement on degree of conversion, monomer release and flexural strength of heat-cured acrylic resin

Objectives: Effect and correlation of aluminum oxide powder on degree of conversion, residual monomer and flexural properties of heat-cured acrylic resin specimens were studied. Materials and methods: Heat-cured acrylic resin and aluminum oxide powders were used. Specimens of specific dimensions from unreinforced and reinforced acrylic resins using stainless steel plates were prepared. Degree of conversion was determined using FTIR Spectrometer. Released monomer was measured using isocratic high-performance liquid chromatography. Flexural strength was tested using three point-bending test. Results: Aluminum oxide reinforcement showed increased degree of conversion than that of the unreinforced specimens. Released monomer from reinforced specimens was lower than that of unreinforced specimens. Deflection at fracture of reinforced specimens was lower than that of unreinforced specimens. Flexural strength was increased by addition of 2.5 % and 5% aluminum oxide. There was a positive correlation between degree of conversion and flexural strength. There was a negative correlation between degree of conversion and monomer release. Conclusions: Aluminum oxide powder increased degree of conversion and flexural strength but reduced monomer release and deflection at fracture. There was a positive correlation between degree of conversion and flexural strength. There was a negative correlation between degree of conversion and monomer release. Clinical relevance: Aluminum oxide powder could reinforce the week acrylic resin denture base materials. Degree of monomer conversion during processing of acrylic resin denture base materials is very critical in determination of monomer release and mechanical properties of acrylic resin in service.

Antimicrobial effects of photodynamic therapy on Staphylococcus aureus biofilm grown on a specific acrylic resin surface for ocular prostheses.

Photodynamic therapy (PDT) is a treatment for the specific control of oral biofilms. However, its effects on maxillofacial prostheses have been barely explored. In this study, we evaluated the antimicrobial effect of PDT using methylene blue (MB) and laser against a Staphylococcus aureus biofilm developed on the surface of scleral acrylic resin. Sixty-six specimens of acrylic resin designed for ocular prostheses were fabricated in a disk-shaped format (3 × 10 mm). S. aureus biofilm was grown on the surface of the specimens for 24 h and the disks were then treated with MB at different concentrations (25, 50, 75 or 100 μg/mL), with or without PDT (GaAlAs diode laser; 660 nm; 100 mW; 9 J; 321.4 J.cm-2; 3.5 W.cm-2 and 90 s). Control groups were treated with 2% chlorhexidine gluconate (CHX) or phosphate buffered saline. After the treatments, colony forming units (CFU) were counted and the samples were qualitatively evaluated by scanning electron microscopy (SEM). Data were analyzed descriptively and by nested ANOVA and the Tukey test (α = .05). PDT groups with MB concentrations at 75 and 100 μg/mL formed fewer CFU compared to the other groups (P < 0.001) and the 2% CHX group did not form any CFU. SEM images revealed that the surface of the polymers in these groups did not show bacterial colonies. PDT significantly reduced S. aureus biofilm in the scleral acrylic resin when associated with an MB dilution of 75 μg/mL or higher. Thus, PDT can be a promising candidate for disinfecting ocular prostheses.

In vitro evaluation of the effect of different disinfectants on the biofilm of Staphylococcus epidermidis and Staphylococcus aureus formed on acrylic ocular prostheses.

The aim of this study was to evaluate the effect of disinfectants on the biofilm of Staphylococcus aureus and Staphylococcus epidermidis formed on the acrylic surface of ocular prostheses. In this study, 396 acrylic specimens were manufactured (50% for Staphylococcus epidermidis, and 50% for Staphylococcus aureus). For each bacterium, 66 specimens were subjected to biofilm formation on their surfaces for 24 hours, 66 specimens were subjected to biofilm formation on their surfaces for 48 hours, and 66 specimens were subjected to biofilm formation on their surfaces for 72 hours. Then, they were divided into groups according to disinfection method (n = 6): sterile distilled water for 10, 15, 30 min, and 6 hours (control); soap for 30 min (NES30); Opti-Free for 30 min (OPF30) and 6 h (OPF6); Efferdent for 15 min (EFF15); and 0.5%, 2%, and 4% chlorhexidine for 10 min (0.5% CHX10, 2% CHX10, and 4% CHX10). After the treatments, the specimens were vortexed to release the biofilm and the counting of bacterial colonies was performed (CFU/mL). Three-way ANOVA and the Tukey-Kramer HSD test were used (α = 0.05). For Staphylococcus epidermidis, there was no significant difference between NES30, OPF30, and OPF6 with their respective control groups; nor between NES30, OPF30, and OPF6 themselves, regardless of the biofilm development period (P >0.05). For Staphylococcus aureus, there was no significant difference between NES30 and OPF30 with their control group; nor between NES30 and OPF30 themselves, regardless of the biofilm development period (P >0.05). For Staphylococcus aureus, OPF6 showed a significant reduction in the number of CFU/mL when compared with its control group, NES30, and OPF30, regardless of the biofilm development period (P <0.05). For both bacteria, 0.5% CHX10, 2% CHX10,4% CHX10, and EFF15 showed a significant reduction in the number of CFU/mL when compared with their control groups, NES30, OPF30, and OPF6, regardless of the biofilm development period (P <0.05). Therefore, EFF15 and CHX (0.5%, 2% and 4%) were effective in reducing Staphylococcus epidermidis and Staphylococcus aureus on acrylic surfaces. NES30 and OPF (30 and 6) are not recommended.

Tensile bond strength of acrylic and composite denture teeth to milled CAD/CAM resins

Objective: was to evaluate effect of different surface treatment on tensile bond strength of two different types of artificial teeth to CAD/CAM denture base. Materials and Methods: 160 specimens were fabricated and divided into two main groups according to the denture base material. Group (A) for conventional denture base (HCAR denture base) and Group (B) for CAD/CAM denture base. According to the artificial teeth each group of denture base was subdivided into two subgroups, subgroup (I) for conventional acrylic denture teeth and subgroup (II) for composite resin denture teeth. According to the surface treatment each subgroup of artificial teeth were subdivided into four subgroups as following: Subgroup 1: no surface treatment (control group). Subgroup 2: sandblasting with 250 micron alumina particles. Subgroup 3: roughening with diamond bur. Subgroup 4: specimens were treated by dichloromethane. Results: The results showed that Pre-polymerized CADCAM acrylic resin denture bases specimens exhibited non-significant lower bond strength than HCAR denture base specimens (p>0.05), acrylic resin denture teeth demonstrated higher bond strength to denture bases than composite resin denture teeth (p≤0.05). Conclusion: the Pre-polymerized CADCAM acrylic resin denture bases specimens exhibited non-significant lower bond strength than HCAR denture base specimens, and acrylic resin denture teeth demonstrated higher bond strength to denture bases than composite resin denture teeth, the bond strength of the denture teeth treated with both dichloromethane and sandblasting was improved while the bond strength of the denture teeth treated by roughening with diamond bur was decreased.

Antimicrobial activity of effervescent denture tablets on multispecies biofilms.

To investigate the impact of peroxide-based solutions in reducing viability and metabolic activity of multispecies biofilms on denture base acrylic resin surfaces and for removing them from these surfaces. Denture cleansers are effective in reducing monospecies biofilm; however, studies evaluating their action on multispecies biofilms are scarce. Sixty-nine denture base acrylic resin specimens (Ø 15×3mm) were sterilised then contaminated with Candida albicans, Staphylococcus aureus and Pseudomonas aeruginosa to form multispecies biofilms. Biofilms were grown for 24hours; subsequently, specimens were immersed in three different cleansing solutions (n=9): nitradine (NI), fixodent (FX) and phosphate-buffered saline (Control), according to the respective manufacturer's instructions. After applying the hygiene protocols, viability of microorganisms was evaluated by counting colony-forming units and assessing metabolic activity. Moreover, biofilm removal capacity was estimated based on extension of cell-covered areas visualised in fluorescent microscopy micrographics. Microbial counts were solution-dependent; NI was effective against all microorganisms (P<.05). FX exhibited moderate antimicrobial action, reducing P aeruginosa (P<.05) and Saureus (P<.05) viability by approximately 2 logs. Both peroxide-based solutions reduced metabolic activity (P<.001) and biofilm-covered areas on specimen surfaces (P<.001). Under the experimental conditions tested, these results demonstrated that peroxide-based solutions had favourable antimicrobial activity but promoted no broad elimination of aggregated multispecies biofilm. NI might be more suitable as complementary chemical agent for controlling multispecies denture biofilm.

Chemical Composition and Effectiveness of Ocimum basilicum L. Extracts on the Adhesion of Candida albicans and C. dubliniensis on Acrylic Surfaces of Removable Orthodontic Appliances

The outbreak of diseases caused by Candida species is growing. These opportunistic pathogens can produce biofilm on non-biological surfaces, such as removable orthodontic appliances. Over the past two decades, there has been a significant increase in resistance to several types of antifungal drugs. Recently, there is a growing interest in using herbal plants and their extracts as an alternative to antifungal drugs. A common plant is basil, which belongs to Lamiaceae family. This study aimed to determine the effect of basil extracts on the adhesion of C. albicans and C. dubliniensis to acrylic surfaces of removable orthodontic appliances. Basil dried leaves were macerated in ethanol to extract its constituent, and then the extract was dissolved in water and fractioned by other solvents, including n-hexane and ethyl acetate, successively. The minimum inhibitory concentrations (MIC) of the extracts against standard species of Candida were determined by the broth microdilution method based on clinical and laboratory standard institute (CLSI) protocol. Afterward, adherence and biofilm formation tests were done on acrylic specimens in the vicinity of proper concentration of fractions with the help of the Crystal Violet and spectrophotometry method. MIC for ethyl acetate fraction, n-hexane fraction, ethanol crude extract, and the aqueous fraction was 1024, 2048, ≥2048, &gt;2048 µg/ml, respectively. Inhibition of adherence and biofilm formation for Candida albicans and Candida dubliniensis in the vicinity of ethyl acetate fraction was 73% and 78%, respectively. In the vicinity of n-hexane fraction was 65% and 78%, respectively. Two fractions could inhibit the growth, adherence, and biofilm formation of two Candida species.

The Analysis of the Differences between the Influence of Herbal Mouthwashes and the Chlorhexidine Mouthwash on the Physical Characteristics of Orthodontic Acrylic Resin

The present study, intended to compare the effects of immersion in herbal mouthwashes and the Chlorhexidine mouthwash on orthodontic acrylic resin, specifically with regard to alterations in its hardness, roughness and color. Seventy-two specimens of Orthodontic self-cured acrylic resin were used for the experiments. After preparation, specimens were placed in three types of mouthwash including Chlorhexidine 0.2 % (CHX), Persica and Matrica. The changes in microhardness (ΔKNH), Surface roughness (ΔRa) and color (ΔE) were evaluated prior to and following the immersion in mouthwashes. In order to analyze the data, we made use of SPSS version 22. One-Way ANOVA test was used to find the differences between groups. The Tukey test was conducted in the final stage. It was revealed that acrylic resins had lower microhardness when 12 hours after immersion had taken place. There were significant differences after 12h, 24h and 7 days between the groups in the softening of acrylic resins. The reduction in microhardness of acrylic resin with herbal mouthwashes in the three-time intervals was higher than CHX. With regard to increasing surface roughness, the disparity between herbal mouthwashes was insignificant. However herbal mouthwashes significantly increased the value of roughness more than CHX. Changes in color were significantly higher in all mouthwashes. Herbal mouthwashes caused more color variation than CHX. The color, roughness and hardness of acrylic resin undergo changes as a result of being immersed in the mouthwashes. However, the effect of herbal mouthwashes was more than that of CHX.