Salma M. Fathy

Background/Objectives: Fabrication of ceramic restorations with higher performance, biocompatibility, and mechanical durability, as well as excellent optical properties, is challenging. Therefore, this study was designed to investigate the mechanical properties and surface roughness of different glass ceramics manufactured with CAD/CAM and pressed techniques before and after exposure to simulated gastric acidic challenge. Methods: Lithium disilicate-based (LDS) ceramic, advanced lithium disilicate (ALDS), and zirconia-reinforced lithium silicate (ZLSC), were manufactured with two techniques. Disc-shaped (N = 336) specimens were used to test the biaxial flexural strength (BFS), while surface microhardness and surface roughness were evaluated before and after exposure to hydrochloric acid (34–37% concentration and 1.2 pH for 24 h). The results were statistically evaluated using two- and one-way ANOVA, Tukey’s post-hoc and Student’s t-test. Results: Both CAD and pressed types of LDS ceramic IPS e.max, showed significantly highest BFS and microhardness before and after acidic challenge (p = 0.01 and <0.01, respectively). ALDS and ZLSC showed significantly lower roughness before acidic aging, while all groups showed no significant difference after aging. Conclusion: Pressed groups showed better mechanical performance than CAD groups. LSD (IPS e.max types) continuously showed a better mechanical performance than modified LDS. ALDS and ZLSC showed the best performance in terms of surface smoothness, but after acidic exposure, no significant difference was observed compared to the other groups.

Background: Flexible denture base polymers have gained popularity in modern dentistry however, their biofilm formation tendency, adversely affecting the oral tissue heath, remains a concern. Consequently, this study aimed to evaluate surface roughness and biofilm formation tendency of two types of denture base resins manufactured with two techniques before and after surface coating with chlorohexidine (CHX) NPs. Materials and methods: Acetal (AC) and Polymethyl-methacrylate (PMMA) resins manufactured by conventional and CAD/CAM methods were shaped into disk (10 X 10 X 1 mm). They were dipped for 8 h and 24 h in colloidal suspension prepared by mixing aqueous solution of CHX digluconate and hexa-metaphosphate (0.01 M). Surface roughness, optical density (OD) of microbial growth media and biofilm formation tendency were evaluated directly after coating. Elutes concentrations of released CHX were evaluated for 19 days using spectrophotometer. Three-way ANOVA and Tukey’s post-hoc statistical analysis were used to assess the outcomes. Results: AC CAD/CAM groups showed statistically significant higher roughness before and after coating (54.703 ± 4.32 and 77.58 ± 6.07 nm, respectively). All groups showed significant reduction in OD and biofilm formation tendency after surface coating even after 19 days of CHX NPs release. Conclusions: Biofilm formation tendency was highly relevant to surface roughness of tested resins before coating. After CHX NPs coating all tested groups showed significant impact on microbial growth and reduction in biofilm formation tendency with no relation to surface roughness. Significant antimicrobial effect remained even after 19 days of NPs release and specimens storage.

Background This study aimed to evaluate surface roughness and biofilm formation tendency of two types of denture base resins manufactured with two techniques before and after surface coating with chlorohexidine (CHX) NPs and release of these NPs from coated resins. Materials and methods Acetal (AC) and Polymethyl-methacrylate (PMMA) resins manufactured by conventional and CAD/CAM methods were shaped into disk (10 X 10 X 1 mm). They were dipped for 8h and 24h in colloidal suspension prepared by mixing aqueous solutions of CHX digluconate and hexa-metaphosphate (0.01 M). Surface roughness, optical density (OD) of microbial growth media and biofilm formation tendency were evaluated directly after coating. Elutes concentrations of released CHX were evaluated for 19 days using spectrophotometer and then OD after release was evaluated again. Three way ANOVA and Tukey’s post-hoc statistical analysis were used. Results AC CAD/CAM groups showed statistically significant highest roughness before and after coating (54.703 ± 4.32 and 77.58 ± 6.07 nm, respectively). All groups showed significant reduction in OD and biofilm formation tendency after surface coating even after 19 days of CHX NPs release. Conclusions Biofilm formation tendency was highly relevant to surface roughness of tested resins before coating. After CHX NPs coating all tested groups showed significant impact on microbial growth and reduction in biofilm formation tendency with no relation to surface roughness. Significant antimicrobial effect remained even after 19 days of NPs release and specimens storage.

Thermoplastic resin fiber composites have an easy fabrication process, good mechanical properties, and compatible stiffness to tooth dentin. However, they have not yet attracted much interest in the field of dentistry. The current study was carried out to test a new proposed approach to manufacture a fiber reinforced composite endodontic post and evaluate its flexural strength through a two-point inclined loading test. The proposed fiber post manufacture approach depends upon a braiding technique of the glass fibers’ (GF) reinforcing component with thermoplastic polypropylene (PP) resin fibers that will later represent the resin matrix after thermal melting. Posts were made of different core (70%) and sheath (30%) construction (PP/GF ratios) using three different GF types and seizing pre-treatment to both fiber types. Two-point inclined loading test at 45 °C applied force angle was used to test the posts’ flexural strength. Fiber posts (1.6 mm in diameter) with pure GF (de-sized starch E-GF and pre-silanized S-GF) core, and sheath construction with higher PP/GF ratios, showed the significantly highest two-point bending strength (56.67 ± 4.89 and 53.96 ± 1.81 MPa, respectively), among experimental posts groups (except for the commercial control posts). However, posts with PP core type showed the lowest values (21.59 ± 1.86 and 16.54 ± 1.94 MPa for de-sized and E-glass sheath fibers, respectively). Based on these findings, the proposed approach was reliable in producing fiber-reinforced composite post with the desired dimensions and fiber distribution. Post construction with a pure GF core and higher PP/GF ratio showed considerably higher flexural strength and GF volume fraction comparable to commercial available post types.

Nanoparticles are gaining more interest in dentistry for their antimicrobial, physical as well as other properties. This study aimed to evaluate the effect of adding two types of nanoparticles (NPs) on calcium silicate hydraulic cement’s (CSHC) unique bioactivity and antibacterial properties. Biotitania/AgCl NPs were synthetized and characterized for its morphology, types of formed functional groups and crystalline AgCl using field emission scanning electron microscope (FE-SEM) equipped with energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), Fourier transformation infrared spectroscopy (FT-IR) and thermo-gravimetric analysis (TGA). The former NPs and commercial titania (TiO2) NPs were added (0.5, 1.5 and 3-weight %) to commercial CSHS powder. A total of 140 disk-shaped specimens (10 mm×1 mm) were prepared (seven material groups per each test in addition to the eighth cell control group) to evaluate cell viability and alkaline phosphatase activity (ALP) after 3 and 12 days, respectively. All were incubated with mesenchymal stem cells. Antibacterial efficacy against Streptococcus mutans (S. mutans) was evaluated through the bacterial growth curve slopes while being in direct contact with the tested material groups for 18 h. One-way analysis of variance (ANOVA) and post hoc Tukey’s tests were used to analyze the obtained data. Addition of all NPs percentages had no significant effect (P 0.05) on cell viability in comparison to positive control CSHC. Commercial TiO2 NPs (0.5 weight %) had statistically significant lower values (P≤0.05) for bacterial growth curve slope. However, addition of all NPs percentages had significantly improved (P≤0.05) the ALP activity of CSHC with the most prominent effect to 3-weight% biotitania/AgCl NPs. Based on this in vitro study, addition of biotitania/AgCl NPs up to 3-weight% significantly improved the bioactivity of CSHC without having a significant negative impact on its antibacterial efficacy. Interestingly, the addition of commercial TiO2 even in small amounts can significantly improve CSHC antibacterial efficacy.

This study evaluated the impact of using biomimetic analogs (poly-acrylic acid and sodium tri-meta-phosphate) on dentin remineralization using two cement materials, the first is calcium silicate based and the second is calcium hydroxide based materials. Two standardized occlusal cavities (mesial and distal) were prepared within dentin after removal of occlusal enamel. Artificial demineralized dentin was induced through pH cycling (8 h in demineralizing and 16 h in remineralizing solutions). Demineralized cavities were divided into four groups; two groups received cement materials. The other groups were first treated with biomimetic analogs then restored with pulp cement materials. Teeth were sectioned buccolingually into two halves. Treated cavities with analogs were stored in simulated body fluid containing poly-acrylic acid. Untreated cavities were stored in simulated body fluid only. Ground unstained sections of demineralized dentin were examined using light microscope. Specimens were examined after 1, 6 and 12 weeks of storage using energy dispersive X-ray Spectroscopy (EDX) and Vickers microhardness was evaluated. Two-way ANOVA was used to analyze data statistically. Calcium silicate-based cement group with biomimetic analogs showed the highest statistically significant calcium and phosphorous wt% in addition to highest surface hardness values after 12 weeks of storage. Demineralized dentin ground sections showed increase in light zones after total period of storage. Calcium silicate-based cement showed the best ability to enrich the artificial carious dentin with ions for remineralization. Using biomimetic analogs had a significant impact on demineralized dentin surface hardness improvement.

This study investigated cytotoxic probability, osteogenic potential, and antibacterial efficacy of two pulp-capping hydraulic calcium-silicate cements. For osteogenic potential and cytotoxicity evaluation, mesenchymal stem cells (MSCs) and materials disc-shaped specimens were used. Increase or decrease in a number of proliferating MSCs was calculated after three intervals. Alkaline phosphatase (ALP) levels in osteogenic media were normalized to the total protein content of cells and measured spectrophotometrically. Antibacterial efficiency through growth curves of Streptococcus mutans in direct contact with tested materials. Biodentine showed the highest number of proliferating MSCs (278000.41 ± 4000.06, after 72 h) and the highest concentration of ALP after 12 days (209.26 ± 7.17 μU/μg protein). It showed the lowest slope (0.003 ± 0.0005) of S. mutans strains growth curves after 18 h. Biodentine proved a highly significant osteogenic ability and gave a significant reduction of S. mutans growth.