Key Engineering Materials Vol. 751

Abstract: The aim of this study was to evaluate the effects of bleaching on color change of stained resin composites. Ninety disk-shaped specimens were prepared with 3 different composite materials (Estelite ∑ Quick, Premise, and Filtek Z350 XT). After stored in artificial saliva at 37°C for 24 hours in an incubator, the 30 specimens of each material were divided into 3 subgroups and immersed in either coffee, red wine, or artificial saliva (control) at 37°C. After 24 days, spectrophotometric measurement was performed. After the staining process, the bleaching agent (Opalescence, 10% carbamide peroxide) was applied to the surface of the specimens, 8 hours per day for 14 days. After the bleaching process, spectrophotometric measurement was performed. The color differences between specimens before and after bleaching were statistically significant (ΔE*ab>3.3) for all composites in the red wine staining. The highest-level color change after bleaching was observed for Filtek Z350 XT in red wine staining, while the least value was found in Estelite ∑ Quick in coffee staining. In summary, color changes of all red wine-stained composites after bleaching were noticeable and have higher level of color change than coffee-stained composites.

Abstract: The elastic modulus and nanohardness of denture bases may be different based on the type of material. The purpose of this study was to compare the elastic modulus and nanohardness of polyamide and polymethyl methacrylate (PMMA) denture base materials. Three polyamide denture base materials (Valplast, Lucitone FRS, and Thermoplastic Comfort System (TCS)) and one Polymethyl methacrylate (PMMA,Triplex Hot) denture base material (n=10) were evaluated to compare their elastic modulus and nanohardness values using an ultramicroindentation system (UMIS 2000; CSIRO, Lindfield, Australia). The data were statistically analyzed using one-way ANOVA, followed by Tukey HSD and Tamhane’s post hoc tests (α=.05). The elastic modulus and nanohardness of PMMA were significantly higher compared to the polyamide groups (P<.05). All the materials showed significant differences in each of their elastic modulus and nanohardness (P<.05). The values of nanohardness and elastic modulus of each group were as follows: Triplex Hot > Lucitone FRS > Valplast > TCS. The elastic modulus and nanohardness values varied among the polyamide denture base materials. PMMA showed higher elastic modulus and nanohardness than the polyamide. A strong positive correlation existed between elastic modulus and nanohardness of the denture bases tested (R² = 0.979, P<.05).

Abstract: Objective: To investigate the flexural strength and cytotoxicity of ZCC, a resin modified zinc oxide-calcium carbonate liner prototype, compared with commercial dental liners. Materials and Methods: ZCC, Dycal, Ultra-Blend® plus (UB), and TheraCal LC® (TC) were evaluated for flexural strength. Six samples of each material were incubated in growth medium (10% fetal bovine serum supplemented DMEM) for 24 h. Primary human dental pulp cells were cultured in the conditioned medium from each sample, with growth media used as a control. Cytotoxicity was determined using an MTT assay. Data were analyzed by one-way ANOVA. The value of p<0.05 was considered significant. Results: UB had the highest flexural strength with Dycal presenting the lowest values (p<0.05). ZCC demonstrated significantly higher flexural strength values compared with those of TC and Dycal (p<0.05). The MTT assay indicated that Dycal conditioned media significantly reduced cell viability at 24 and 48 hours (p<0.05). There was no significant difference in viability between the control, ZCC, UB, and TC groups at 24 and 48 hours (p>0.05). Conclusion: ZCC met the requirements for flexural strength per ISO 9917-2:2010(E). There was no significant difference in viability between the control and ZCC group at 24 and 48 hours.

Abstract: 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.

Abstract: In this study, an alveolar ridge preservation using novel hydroxyapatite granules which was fabricated by three dimensional printing technique in post-extraction socket was carried out and evaluated. Clinical, radiographic and histology were assessed prior to dental implant placement. Five volunteered patients who needed an extraction of anterior tooth and scheduled for implant replacement were enrolled in this pilot study. No sign of infection or local of systemic immune reaction to the three dimensional printed hydroxyapatite granules in all patients was noted. At 8 weeks post-surgery, the grafted area was observed to be completely filled with woven bone and the formation of new vessels was seen. In addition, the bone quality and quantity of the grafted site when placing the implant showed efficient implant stability (ISQ values ∼ 65) without the need of additional bone graft surgery. Overall results indicated that three dimensional printed hydroxyapatite granules could be potentially employed as bone grafting material for alveolar ridge preservation.

Abstract: This research aimed to study the preparation of activated carbon from sugarcane bagasse waste. The sugarcane bagasse adsorbent was prepared by calcination at 600°C for 2 hours with the use of sulfuric acid (H₂SO₄) as a chemical activation. The adsorption surface possessed high specific surface area (838 m²/g) with mesoporous diameter. Factors explaining adsorption including adsorption isotherm, adsorption kinetic and adsorption mechanism were constructed from methylene blue adsorption experiments. It was found that the equilibrium data was best represented by Freundlich isotherm, showing multilayer coverage of dye molecules at the outer surface of adsorbent with a cooperative adsorption (physisorption and chemisorption). The kinetic of methylene blue adsorption was found to follow pseudo-second-order rate kinetic model, with a good correlation coefficient. This indicated that the overall rate of the dye adsorption process was controlled by the chemisorption process.

Abstract: ACT is a widely used prescriptive drug for analgesic treatment. Due to incomplete conversion of ACT in the body, a significant portion of it is released with human excreta. Most wastewater treatment plants lack the efficiency to treat influent containing ACT residues. As a result, risk of surface and groundwater contamination has been increased. Constructed wetlands (CWs) are one of the widely used natural wastewater treatment technologies, employing soil-plant interactions in treating pollutants through a number of reactions such as plant uptake, ion adsorption and advanced Fenton reaction. In addition, the wetland plants are well-known to generate H₂O₂ in the surrounding rhizosphere for advanced oxidation process. In this study, the potential of laterite soil in initiating Fenton reactions by its abundant composition of iron (Fe) and its modified structure with activated carbon, cement and crushed shellfish (modified soil) were evaluated for ACT treatment. The induced H₂O₂ soil environment in the constructed wetland units could remove almost 80% of the ACT present initially. The results showed good occurrence of Fenton process on both natural laterite soil and modified media bed (cement: laterite soil fine: 50% laterite soil coarse: 50% activated carbon).

Abstract: Currently, Doi Chaang village is the biggest area producing coffee in Thailand. Throughout seed to cup the pulp must be removed from coffee cherry after harvesting and left as waste. Tannin is one of various composition in coffee pulp which is affected by soil nutrition and pH. In this study, we have characterized the amount of tanin in coffee pulp using UV-Visible spectroscopy and electronic structure calculation. The results showed that coffee pulp consist of 5.68% tannin . It was determined to condense tannin form. Moreover, the pH of soil after treated with modified coffee pulp with water, Ca(OH)₂, Na₂S₂O₅, 2% Ca(OH)₂, and 2% Na₂S₂O₅ is higher than that with non-modified case. Likewise, DFT calculations predicted the structure of tannin with smaller HOMO-LUMO gap in the condense tannin.

Abstract: Ag₃PO₄-alginate beads (AAB) were synthesized by simple precipitation method and their structure was characterized by XRD, FT-IR and SEM/EDS, respectively. The AAB was evaluated as the photocatalyst for degradation of methylene blue (MB) under sunlight irradiation. The results showed that AAB exhibited the high performance for degradation of MB (97.6%) in 60 min. The kinetic studied demonstrated that the photocatalytic reactions followed the pseudo first-order model. Moreover, AAB can maintain full photodegradation activity for at least five cycles. Consequently, the AAB are promising materials for the photocatalytic of dyes or similar organic contaminant in environmental pollution cleanup.

Abstract: The preparation of carbon materials from low-cost agricultural residues is presented in this work. Carbon products were prepared from carbonized cassava tuber (cassava tuber char, CTC) using a chemical activation assisted sonochemical process incorporating KOH as an activating agent. The physical properties such as proximate analysis, ultimate analysis and FTIR spectra of raw material were studied using cassava tuber collected from farmland in the Kanchanaburi Province. The structure of the precursor material played a significant role in influencing the quality and properties of the as-prepared carbon. It was found that the specific surface area of carbon products was improved through chemical activation assisted sonochemical process at 80 °C for 4 hours. The influence of KOH impregnation ratios on the specific surface area of the prepared carbon was also investigated in the activation step. Moreover, the properties of cassava tuber-carbon material were characterized by SEM, FTIR, XRD, and multipoint BET analysis. Finally, the application of cassava tuber carbon material as a carbon support for ZnO photocatalyst was investigated by a simple technique.