Barrier membrane is an essential component in guided bone regeneration for successful bone augmentation in implant dentistry. The microstructure of barrier membrane can remarkably impact its mechanical properties and biological performances. This study was aimed to investigate the pore structures of a bi-layered porous polyethylene (PPE) barrier membrane by 2D and 3D characterization techniques. Two opposite sides of PPE barrier membrane were imaged with scanning electron microscope and micro-computed tomography (micro-CT). The 2D and 3D pore characteristics were then analysed with associated software, respectively. Both techniques similarly showed that PPE barrier membrane comprised two different structures including one with low porosity (smooth) and one with high porosity (coarse) as designed. In 2D analysis, both surfaces possessed similar positively skewed distributions in pore area and circle diameter. The smooth side had significantly smaller pore amount, pore density, surface porosity, pore area, circle diameter, Feret diameter and aspect ratio, but larger roundness, circularity and solidity than the coarse side (p < 0.05). In 3D analysis, the smooth side possessed significantly smaller pore diameter and volume porosity than the coarse one (p < 0.05). No significant differences in strut thickness, specific surface area, connectivity density (Conn.D), and degree of anisotropy (DA) were found between two layers (p > 0.05). The combination of 2D and 3D techniques could be effectively employed to characterize the pore microstructure and morphology of PPE barrier membrane. The limitations of each technique were also discussed.
Background To compare the mean mineral density (MMD) and examine the remineralization of carious dentin after cavity disinfection with chlorhexidine gluconate (CHX) and restoration with high viscosity glass ionomer cement (H-GIC) in vitro. Methods Selective caries removal to leathery dentin was performed in 40 extracted primary molars. The samples were scanned using micro-computed tomography (micro-CT) to determine the MMD baseline and randomly divided into 4 groups (n = 10): Equia™ group, applied dentin conditioner and restored with H-GIC (Equia Forte™), CHX-Equia™ group, disinfected the cavity with 2% CHX before applying dentin conditioner and restored with H-GIC (Equia Forte™), Ketac™ group, restored with H-GIC (Ketac Universal™) and CHX-Ketac™ group, disinfected the cavity with 2% CHX before restored with H-GIC (Ketac Universal™). The samples underwent micro-CT scanning post-restoration and post-pH-cycling to determine their respective MMDs. One sample from each group was randomly selected to analyze by scanning electron microscopy (SEM). Results The MMD gain in the 4 groups post-restoration was significantly different between the Equia™ and CHX-Ketac™ groups (oneway ANOVA with Post hoc (Tukey) test, P = 0.045). There was a significant difference in MMD gain post-restoration between the Equia™ and CHX-Equia™ groups (Independent t-test, P = 0.046). However, the Ketac™ and CHX-Ketac™ group’s MMD were similar. The SEM images revealed that the CHX-Ketac™ group had the smallest dentinal tubule orifices and the thickest intertubular dentin among the groups. However, the CHX-Equia™ group had thicker intertubular dentin than the Equia™ group. Conclusion Applying 2% CHX on demineralized dentin enhances the remineralization of the dentin beneath the restoration.
Fluoride supplementation in drinking tap water is one of the well-known effective methods for dental caries prevention. However, overexposure to fluoride following excessive fluoride intake from drinking water leads to dental fluorosis. Therefore, the assessment of daily fluoride consumption is required to calculate the optimal fluoride intake. The present study investigated the fluoride concentration in tap water collected from different areas in Thailand. A total of 27 locations were selected. Three samples of tap water (500 mL each) were independently collected from one location. Each sample in the same location was collected from the same faucet of tap water and stored in different containers. The samples were collected by dental students or dentists who worked in the selected areas from March 2020 to June 2020. Briefly, the faucet was cleaned with the tap water and the water was run from the faucet for 1-2 mins. Then, water was collected in 500 mL bottles and immediately capped. Samples were then stored at room temperature in tightly sealed bottles until analysis. Findings showed that most samples contained fluoride at a concentration lower than 0.7 mg/mL. Further, the water pH was in the range of 6.81-8.37. These levels were lower than the cut-offs established by the World Health Organization (WHO) for maximum levels of fluoride and pH in drinking water. In conclusion, the present study demonstrated that fluoride levels in tap water from different regions in Thailand are lower than those recommended by WHO for fluoride levels in drinking water.
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