Alginate Impression Material Reinforcement Using Polymethyl Methacrylate as Organic Filler

The effect of thermoforming on the tear strength of ethylene vinyl acetate (EVA) mouthguard material (Bioplast®) has not been widely investigated. The present study compared the tear strengths of non-processed and processed EVA specimens in various thicknesses. Two groups of EVA sheet (non-processed and processed) in three different thicknesses of 3, 4 and 5 mm were used in specimen fabrication. The processed EVA sheets were achieved by forming the EVA sheet on the cylindrical stone model with the pressure-molding device (Biostar®). Twelve of tear strength specimens of non-processed and processed group in each thickness were prepared following the modified ASTM D 624-00 guideline. The tear strength test was conducted using universal testing machine (Lloyd® 1K series) with the speed of 500 mm/min. The mean thickness and tear strength of the non-processed and processed specimens in each thickness were compared using independent T-test. The differences in the mean tear strength for each thickness of non-processed and process specimens were determined using one-way ANOVA. The mean tear strength and mean thickness of processed EVA specimens was significantly lower than the non-processed EVA specimens for every thickness (P ≤ 0.05). There was no significant difference in the mean tear strength of EVA specimens among each thickness in both non-processed and processed groups. It can be concluded that the thermoforming process has the significant effect on the tear strength of the EVA mouthguard material formed by pressure molding device in every thicknesses. The tear strength of processed specimens were significant lower than the non-processed. Thus, it is more relevant for testing properties of the processed mouthguard material that the mouthguard material before processing.

Maxillofacial prosthetic materials exhibit a range of qualities that vary considerably, including the hardness and stiffness of alloys and polymers, as well as the flexibility of elastomers and soft polymers. Silicone elastomers are the primary materials employed for maxillofacial prostheses due to their physical properties, which allow for adaptation to the movement of soft tissue. They also exhibit exceptional tensile and tear strength across a broad temperature range. Silicone elastomers can be classified according to the vulcanization process: High-temperature vulcanization (HTV) silicones, and Room temperature vulcanization (RTV) silicones. The addition of nanoparticle enhances thermal and tear strength of maxillofacial silicon.This study estimates the influence of addition tantalum oxide nanoparticle on thermal conductivity and tear strength after addition on maxillofacial silicone. Tantalum oxide nanoparticles were added into VST-50F platinum silicone elastomer at two weight percentages: 1wt% and 1.5wt%. 60 specimens were prepared and classified into two groups: one control group for each property and two experimental groups. All collected data underwent statistical analysis by one-way ANOVA and Bonferroni's multiple comparison test, with significance set at p < 0.05. The Shapiro-Wilk test and Bartlett's test were employed to assess the normality and homogeneity of the data, respectively. The one-way ANOVA test found a very significant difference between all groups, while Bonferroni's test revealed a highly significant difference between the control and experimental groups. Thermal conductivity test found no significant difference between the 1wt% and 1.5wt% groups, however the tear strength test was highly significant. The addition tantalum oxide nano particles improve tear strength and thermal conductivity.

Changes in color and other physical properties of silicone facial prosthesis are the main reasons for its replacement. The purpose of this study was to investigate the effect of time passage on some physical properties such as tensile strength, modulus of elasticity, elongation at break, tear strength, hardness, color stability, and contrast ratio (CR) of 2 silicone facial elastomers after being sealed in glass containers and kept in the dark for 1 year. Specimens from 2 silicone elastomers (Silasto 30 and Premium 2) were made and stored in the dark. Tensile and tear strength tests were conducted according to International Organization for Standardization specification nos. 37 and 39, respectively, in a universal testing machine. Shore A hardness was measured according to the American Society for Testing Materials specification D 2240. Color changes (ΔΕ*) were determined in the CIE L*a*b* system using a tristimulus colorimeter, and CR also was calculated. Data were analyzed by paired and unpaired t-tests at a significance level of α = 0.05. Elongation at break, modulus of elasticity, and hardness were significantly changed, whereas changes in CR were observed only in 1 of the 2 elastomers. Tensile and tear strengths were not significantly changed for both of them. Within the limitations of this study, color changes (ΔΕ) were unacceptable. Most of the physical properties studied were significantly affected because of time passage. Mechanical and physical properties of silicone maxillofacial elastomers can be changed with time passage (natural aging in the dark). The average time of replacing a facial prostheses is 6 to 18 months; thus, it is important that the findings of this study covered a period of 12 months. Time passage seems to be a critical factor contributing to the overall deterioration of a silicone maxillofacial elastomer.

Variability of physical properties across hides and skins requires careful consideration when manufacturing goods from leather. Therefore, an understanding of the extent of this variation and its nanostructural basis is useful. Tear strength tests were performed on ovine leather from a grid of 81 positions on skins. Synchrotron small-angle X-ray scattering measurements were made from three positions on the skin, from 26 skins. The X-ray structural measurements are compared with tear strengths of the samples. It is found that the thickness normalized tear strength does not vary greatly between different positions on the skin, in contrast to bovine hides. There is more variation between different skins than within the same skin. The collagen fibril orientation and orientation index, which has previously been shown to be correlated with tear strength, do not vary significantly between the different sampling positions in ovine skins. The collagen fibril orientation varies through the thickness of the skin in a consistent way. The consistency of collagen orientation in ovine leather between different positions on the skin is in marked contrast to bovine hides and informs the use of ovine leather for manufacturing applications.

Disinfection of polyvinyl siloxane impression material using ozone gas, 0.1% riboflavin, glutaraldehyde, and microwave irradiation and their effect on physical properties.

Impression materials, impression trays, and poured stone cast have been said to be the main source of cross infection between patients and dentists. However, it was observed that disinfection of the impression is not performed systematically in routine dental practice. Disinfection of alginates either by immersion or spray technique was found to cause dimensional inaccuracies, although with proper disinfection of alginates there were small dimensional changes. A variety of fluoride releasing products designed for topical use is currently available. Following their use, varied amount of fluoride is systemically absorbed depending on the fluoride concentration and the manner of its use. The objective of this study was to evaluate the effect of addition (0%, 0.25%,0.5%,1%, 2%, 3%, 4% ) of (NaF) as a self-disinfection to alginate impression material powder and its effect on setting time, tear strength, dimensional change and accuracy of alginate impression materials. Materials and methods: A total No. of (700) specimen were used in this study.These specimens were divided into (5) main groups according to the tests used. Each of the four main groups contain (70) specimen divided into 7 subgroups (ten specimens to be tested for each (7)concentrations which is composed of six percentages of NaFwith alginate powder (0.25%,0.5%,1%, 2%, 3%, 4% )and one for control (0% NaF) , while the fifth group (Microbiological test) contain 420 specimen were divided between Streptococcus mutans and Candida albicans as (120) specimen for each one that was subdivided into three subgroups (specimens taken before impression casting, specimensafter pouring of alginate with stone andspecimens of stone were taken from the casts) in which it contain the same subgroups of the other concentrationsof (NaF) to test its efficacy against (Streptococcus mutans and Candida albicans). Results: Tear strength for all experimental impression materials was greater than those of the control products. There were no statistically significant differences between the dimensional change tests and also reproduction of detail test.With regard to setting time of the impressions, statisticallyreduction were seen between the control and experimental groups of alginate impression materials that contain (NaF). Self-disinfection of alginate impression material containing NaF showed a significant reduction in the count of cell forming unit of microorganism s immediately after impressions were made. Conclusion: In cooperation of specific concentrations of (NaF) as a disinfectant in alginate dental impression produced a significant reduction of contamination, also they caused non-significant effect on dimensional stability, detail reproduction and significant increase in tear strength. Therefore it is recommended as step in preventing cross

Natural rubber-poly(methyl methacrylate) interpenetrating polymer networks—morphology and mechanical properties

Background: Alginate impression is a common dental polymeric material, presented as powder to be mixed with water. Aim: 1. To analyze the effect of alginate powder/water ratio variation on viscosity, tear strength and detail reproduction by in vitro tests, and 2. To evaluate this variation’s effect on patients’ impressions. Materials and methods: Two commercial alginate products were mixed in different viscosities. Viscosity was measured by a viscometer. For the tear strength test, V-shaped specimens were used. For detail reproduction, a die with three scribed lines was used. Clinical dental impressions were examined by stereomicroscope. Results: The alginate specimens mixed with a higher powder/water ratio showed a higher viscosity and tear strength compared to those with a lower powder/water ratio. Both alginate mixtures reproduced two scribed lines in a detail reproduction test. On the other hand, no clear clinical difference was detected when examining dental impressions mixed with a different powder/water ratio. Conclusion: Although increasing the powder/water ratio of mixed alginate raised the resultant viscosity and tear strength by an in vitro test, clinically, no clear difference in tearing was detected. Detail reproduction was minimally affected by the variation in powder/water ratio.

The ideal maxillofacial prosthesis should have fine and thin boundaries that bind with the surrounding facial structures and possess high tear strength. This study aims to determine the best percentages of nanofiller (TiO2) and intrinsic pigment (silicone functional intrinsic) that could be mixed in as additives to improve the tear strength of Cosmesil M511 and VST50F silicone elastomers with the least effect on their hardness. In this in vitro experimental study, a total of 80 samples, 40 for each elastomer, were fabricated. Each elastomer sample was split into two equal groups to test for tear strength and Shore A hardness. Each group consisted of 20 samples, including 10 control samples without additives and 10 experimental samples with additives (mixtures of 0.2 wt% nano-TiO2+ 0.25 wt% intrinsic pigment and 0.25 wt% nano-TiO2+ 0.25 wt% intrinsic pigment for the Cosmesil M511 and VST50F silicone elastomers, respectively). Two-way ANOVA and Tukey test were used for comparison; P < 0.05 was considered statistically significant. Significant differences in tear strength were found among all tested groups (P < 0.05). The tear strength of the experimental subgroups significantly increased compared with the control subgroups (P < 0.05). Significant differences in Shore A hardness were also observed among all tested groups (P < 0.05) except between the experimental subgroups of both materials, where a nonsignificant difference was obtained (P > 0.05). Incorporation of select percentages of TiO2 nanofiller and intrinsic pigment into Cosmesil M511 and VST50F silicone elastomers yields improvements in tear strength with a slight increase in hardness.

Objective To evaluate and compare the stability of the open trayimpression coping within the set impression while attaching the lab analog when polyether (PE) heavy body and polyvinyl siloxane (PVS) putty impression materials were used and the implant platform was placed sub-gingivally at three different depths. Methods Two impression materials, PE and PVS, and custom-made plexiglass models with embedded single implants to simulate implant positioning depths of 0 mm, 2 mm, and 4 mm, sub-gingivally, were used in the study. Open tray impressions were made after attaching impression coping to theimplant embedded in themodel. Implant lab analog was attached to the impression coping in the set impression, and its stability was measured using a universal testing machine. Forty-two open tray impressions were madein six groups, with seven impressions in each group. Descriptive statistics such as mean and standard deviation were calculated. A comparison of the meanstability between the two impression materials at each depth was done using an independent t-test.Comparison of the mean stability between the three different subgingival implant depths in each material was done by one-way ANOVA with the Scheffe multiple comparison test (post-hoc analysis). The level of significance was set at p<0.05. Results The stability of the impression coping was measured as the force in Newtons required for the displacement of the analog attached to the impression coping embedded in the set impression. PEwith the embedded impression coping at a depth of 0 mm gave the highest mean stability value (4.37+/-0.41), and the least mean stability was offered by PVS with the embedded impression coping at 4 mm depth (1.88+/-0.37). When an independent t-test was done to compare the mean stability values of PE and PVS,there was a statistically significant difference at0 mm, 2 mm, and 4 mm. On doing one-way ANOVA to compare the mean stability between the different depth groups, there was a statistically significant difference between the three depth groups in PE and PVS. Scheffe multiple comparison tests (post-hoc analysis) revealed a statistically significant difference between 0 mm, 2 mm, and 4 mm subgingival depths of the impression coping placement in bothPE and PVS. Conclusion The accuracy of the master cast is an important determinant for the precise fit and long life of the final prosthesis. In the case of maxillary anterior implant placements where deep subgingival placement of the implant platform is needed for aesthetic and functional reasons, the impression material should be selected carefully to ensure the stability of the impression coping. Among the materials included in the present study, the PE impression material offered the maximum stability for impression coping compared to PVS.

The aim of this study was to evaluate the effects of a new irrigant solution on the post space cleaning and the adhesive resistance of fiber posts. Eighty roots of bovine teeth were randomly allocated into eight groups (n=10 for each group). Evaluations were performed in two different time points for each irrigant. The irrigants included a control group with distilled water (DW), 2.5% NaOCl and 17% EDTA (SH), 1% peracetic acid (PA), and 5% boric acid and 1% citric acid (EX). The time points were 24 hours (I-immediate) and 6 months (D-delayed). The push-out test was performed using a universal testing machine with a 5 kN load cell operating at a crosshead speed of 0.5 mm/minute. The dentinal cementation system was analyzed using a laser confocal microscope (LSM5, Zeiss, Jena, Germany), and incidence of residue on radicular dentin was evaluated by scanning electron microscopy (SEM). The incidence of residue was evaluated by the Kruskal-Wallis test and push-out bond strength and dentin penetrability were evaluated via a one-way analysis of variance (ANOVA) and Tukey tests (α=0.05). The EX irrigation protocol demonstrated the lowest incidence of residue on the dentin surface (p<0.05), independently of the evaluated third. In the cervical and the middle post thirds, EXI, EXD, SHI, and SHD groups exhibited similar push-out bond strength values (p>0.05). EXI, EXD, PAI, and PAD exhibited the greatest dentinal penetrability of the cementation system in all the post thirds (p<0.05). A solution containing 5% boric acid and 1% citric acid can be a promising irrigant for radicular post space cleaning. It has adequate potential for cleaning the dentin surface without interfering with the adhesive interface between the dentin and the cementation system.

IntroductionThe denture bases fabricated from polymethylmethacrylate (PMMA) have some disadvantages, such as surface prone to microbial growth and biofilm accumulation, which contributes to the onset and dissemination of infections among denture wearers. Therefore, the purpose of this in vitro study was to evaluate the flexural strength, hardness, and antimicrobial effect of denture base resin incorporated with 0.05% and 0.1% silver nanoparticles (AgNPs) of Aloe barbadensis miller (aloe vera), Morinda citrifolia (noni), and Boesenbergia rotunda (finger root).Materials and methodsA total of 84 PMMA samples were used and were divided into three groups. Flexural strength tests were performed on Group 1 PMMA blocks. Group 2 involved hardness testing of PMMA blocks, whereas Group 3 involved antimicrobial activity. Each group was subsequently split into seven subgroups with differing concentrations of AgNPs: Sub Group 1: control (no AgNPs), Sub Group 2: 0.05% aloe vera AgNPs, Sub Group 3: 0.1% aloe vera AgNPs, Sub Group 4: 0.05% noni AgNPs, Sub Group 5: 0.1% of noni AgNPs, Sub Group 6: 0.05% finger root AgNPs, and Sub Group 7: 0.1% finger root AgNPs. The flexural strength was evaluated using a universal testing machine (Instron 8801). Surface hardness was measured using a Vickers tester (Tukon 1102). For the antimicrobial activity analysis, the samples were incubated in a suitable culture broth containing Candida albicans for 24 hours. Microbial colony count (colony-forming unit (CFU)/mL) was estimated to evaluate the microbial adhesion to the surface of the denture base materials.Statistical analysisThe flexural strength, hardness, and CFU between the groups were analyzed using one-way analysis of variance (ANOVA) followed by multiple comparisons with Tukey’s honest significant difference (HSD) test (α=0.05). The level of statistical significance was determined at p<0.05.ResultsIt was observed that the mean flexural strength was maximum in PMMA incorporated with 0.05% of aloe vera AgNPs and least in PMMA incorporated with 0.1% noni AgNPs. It was seen that a steady loss in flexural strength is observed from 0.05% to 0.1%. The mean hardness was maximum in PMMA incorporated with 0.1% of noni AgNPs and least in PMMA incorporated with 0.05% aloe vera AgNPs. It was also found that the hardness was directly proportional to the number of nanoparticles. With an increase in the weight percentage of nanoparticles, a steady increase in hardness was seen in all the test groups.In our study, the results showed that finger root 0.1% showed the least CFU with a significant reduction of C. albicans adherence; therefore, it indicates higher anti-fungal activity. Aloe vera 0.05% showed the lowest inhibition of C. albicans, suggesting the least anti-fungal activity.ConclusionWithin the limitations of this study, It can thus be concluded that the addition of AgNPs incorporated with plant extracts of Aloe barbadensis miller (aloe vera), Morinda citrifolia (noni), and Boesenbergia rotunda (finger root) can alter the flexural strength, hardness, and microbial adhesion of PMMA. In our study, it can be concluded that flexural strength increases with the addition of AgNPs of 0.5% concentration after which a steady loss is seen. However, the hardness and antimicrobial activity increased with an increase in the concentration of AgNPs in all three plant extracts.

Influence of the content of polymethyl methacrylate on the properties of porous Si3N4 ceramics fabricated by digital light processing

The purpose of this study was to examine the wear of resin materials using two-body wear tests and to verify a selection method for optimal interim restoration materials from findings of a diagnostic occlusal device. Specimens were prepared from nine different resins used for diagnostic occlusal devices (soft resin) and interim restorations. Wear tests were conducted using an abrasion testing machine. The resulting wear on resin specimens and antagonist stainless-steel styluses was measured using a laser confocal scanning microscope, and the surface conditions were observed through a scanning electron microscope. The data were analyzed with one-way ANOVA and Tukey's multiple comparison test. The findings of the previous study on diagnostic occlusal devices were referred to in order to verify the selection method of optimal interim restoration materials. The maximum wear depth of the soft resin specimens was significantly greater than that of the other specimens (p<0.05) and was equivalent to the wear depth of a diagnostic occlusal device used for 14 nights. The wear of bis-acryl resin material was shallower than that of the other materials (Polymethyl methacrylate and polyethyl methacrylate), and its antagonist stylus was significantly worn (p<0.05). The findings of the previous and present studies showed a relationship among the parameters of Electromyography, wear depth of the diagnostic occlusal device, and wear of materials used for interim restorations. Findings related to bruxism can guide in the selection of interim restoration material and the determination of a suitable duration of wear.

Poly methyl methacrylate (PMMA) is mostly used for fabrication of denture base by heat-curing technique. Therefore, the purpose of this study is to investigate the effect of Al2O3 filler as toughening particles together with nitrile butadiene rubber (NBR) particles as impact modifier were used to reinforce PMMA denture base materials on the impact strength (IS) and fracture toughness (KIC). PMMA powder was mixed with liquid methyl methacrylate (MMA) and ethylene glycol dimethacrylate (EGDMA) as crosslinking agent. The powder components are PMMA, benzoyl peroxide, NBR (5, 7.5 and 10 wt%), and Al2O3 filler (5 wt%) treated by silane. The liquid components are 90% of methyl methacrylate and 10 % ethylene glycol dimethacryate. FTIR analyses confirmed that the Al2O3 filler was successfully treated with silane as coupling agent. The morphology of fracture surfaces was characterized using field emission scanning electron microscopy (FESEM). The results shown that IS and KIC improved significantly when using treated the Al2O3 filler. IS has increased to 56% (8.26 KJ/m2) and 73% (2.77 MPa.m1/2) for KIC when treated Al2O3 filler compared to unreinforced PMMA matrix. Statistical analyses of data results were significantly improved (P<0.05) when using 7.5 wt% NBR with treated Al2O3 filler compared to other the compositions.