Strength and bioactivity of PEEK composites containing multiwalled carbon nanotubes and bioactive glass.

Polyetheretherketone (PEEK) polymer is a widely accepted implantable biomaterial in the biomedical field. However, PEEK has a low elastic modulus (E-modulus) as well as a bio-inert nature which is not conductive to rapid bone cell attachment, hence, producing delayed or weak bone-implant integration. Multiwalled carbon nanotubes (MWCNTs) represent one of the strongest known materials that could be added to a polymer to improve its mechanical properties. Bioactive glasses (BGs) can form hydroxyapatite deposits on their surfaces and form a tight bond with the bone, thus, their incorporation into the PEEK matrix may improve its bioactivity. METHODS: Eight groups were formulated according to the type and percentage of modification of PEEK by MWCNTs and BGs. Group 1: Pure PEEK (P), Group 2: P + 3% MWCNTs (PC3), Group 3: P + 5% MWCNTs (PC5), Group 4: P + 5% BGs (PG5), Group 5: P + 10% BGs (PG10), Group 6: P + 3% MWCNTs + 5% BGs (PC3G5), Group 7: P + 3% MWCNTs + 10% BGs (PC3G10), and Group 8: P + 5% MWCNTs + 5% BGs (PC5G5). Characterization of the vacuum-pressed PEEK and PEEK composite specimens was done using FE-SEM, EDS, FT-IR and TF-XRD. Three-point load test was done to obtain the flexural strength (F.S) and the E-modulus of the specimens. Wettability was determined by measuring the contact angle with distilled water. In-vitro bioactivity was determined after immersion of specimens in simulated body fluid (SBF). Moreover, the effect of the specimens on osteoblastic cell viability was evaluated. RESULTS: Three-point load test results have shown an improvement in both F.S. and E-modulus for groups PC5, PC3G5 and PC5G5. The lowest contact angle was obtained for group PC5G5 followed by the PC3G10 group. All specimens containing BGs showed the formation of hydroxyapatite-like deposits after their immersion in SBF, as well as an improvement in osteoblastic cell viability compared to PEEK. CONCLUSION: PC3G10, PC3G5 and PG10, groups are promising for the fabrication of patient-specific implants that can be used in low-stress-bearing areas.

Effect of aging on mechanical and antibacterial properties of fluorinated graphene reinforced glass ionomer: In vitro study.

OBJECTIVES: This study: 1) aims to test the mechanical and antibacterial properties of fluorinated graphene strengthened glass ionomer materials (FG/GICs); 2) aims to investigate the effects of thermo-cycling on (FG/GICs). MATERIALS AND METHODS: Fluorinated graphene (FG) with bright white color was prepared from fluorinated graphite (SIGMA Aldrich), using modified Hummer's method, to be added to conventional glass ionomer cements (GICs). In addition to a control group (group 1), experimentally modified GICs were prepared by adding FG to the conventional glass ionomer powder with three different weight ratios; (group 2, 1 wt %; group 3, 2.5 wt %; and group 4, 5 wt %) using mechanical blending method. Experimental groups of the specimens (n = 240) were divided, for each concentration (n = 120) half of the specimens were subjected to thermo-cycling. Hardness, compressive strength, and antibacterial activity of (FG/GICs) were measured with and without thermo-cycling. Compressive strength was measured by a universal testing machine, hardness was measured using a Vickers micro-hardness tester, and antibacterial effects against staphylococcus aureus and streptococcus mutans were tested by the pellicle sticking method. For statistical analysis, numerical data were explored for normality and variance homogeneity using Shapiro-Wilk and Leven's tests respectively. RESULTS: The prepared (FG/GICs) showed an increase in hardness in group 4 (p < 0.001). Groups 3 and 4 gave the highest compressive strength values with no significant difference between them (p < 0.001). Groups 2, 3, and 4 showed improved antibacterial activity with no statistical difference between them (p > 0.001). Results after thermo-cycling showed significantly decreased hardness, and compressive strength values (p < 0.001), however, the results of antibacterial activity against streptococcus mutans showed no statistical difference after thermo-cycling (group 2, p = 0.05; group 3, p = 0.18; group 4, p = 0.26). The same results were observed for antibacterial activity against staphylococcus aureus (p = 0.92, p = 0.14, and p = 0.48 respectively). CONCLUSION: FG can be considered a promising additive to GICs to promote its anti-cariogenic effects, however, these antibacterial effects are only useful in the short term, as aging adversely affected their mechanical properties. The 2.5 wt % FG/GICs is suggested to be the most encouraging, as after aging, it represented the highest compressive strength among all groups, while its hardness values were at least comparable to that of conventional glass ionomer. CLINICAL SIGNIFICANCE: FG/GICs can be considered an anti-cariogenic restoration in temporary restorative interventions, as in certain cases in deciduous teeth where considerable esthetics may be required, especially those with difficult moisture control, where neither resin composite restorations nor amalgam restorations will be indicated. It can also be used for patients with high caries index or in atraumatic restorative treatment (ART) in low-income countries.

Effect of resin infiltration and bleaching on surface roughness and microhardness of human enamel with induced white spot lesions / Efeito do infiltrante resinoso e do clareamento na rugosidade e microdureza de superfície do esmalte humano com lesões de mancha branca induzidas

Objective: To comparatively evaluate the effect of resin infiltration, bleaching and bleaching followed by resin infiltration on the surface roughness and microhardness of human enamel with induced white spot lesions (WSLs) and their resistance to acidic challenge. Material and Methods: Sixty human specimens were randomly divided into three groups (n=20) according to the treatment modality applied; group I Icon® resin infiltration, group II bleaching and group III bleaching followed by Icon® resin infiltration. For each treatment modality, 10 specimens were tested for surface roughness and another 10 for microhardness. WSLs were artificially induced in all specimens and after treatment, all specimens were subjected to acidic challenge. Surface roughness was measured by the tapping mode of the atomic force microscope (AFM) and microhardness was measured by digital Vickers hardness tester at baseline, after induction of WSLs, after treatment and after acidic challenge. Results: Groups I and III showed significant reduction in surface roughness after treatment, while group II showed significant increase. Groups I and III showed significant increase in the microhardness after treatment, while group II showed insignificant increase. The three tested groups showed significant increase in surface roughness values and significant reduction in microhardness after acidic challenge. Conclusion: Resin infiltration and bleaching followed by resin infiltration reduced the surface roughness and enhanced the microhardness of the WSLs. The three treatment modalities failed to resist acidic challenge resulting in increasing surface roughness and reducing microhardness. (AU)

Objetivo: Avaliar comparativamente o efeito do infiltrante resinoso, clareamento e clareamento seguido de infiltração resinosa sobre a rugosidade e microdureza superficial do esmalte humano com lesões de manchas brancas induzidas (WSLs) e sua resistência ao desafio erosivo. Material e Métodos: Sessenta espécimes humanos foram divididos aleatoriamente em três grupos (n = 20) de acordo com a modalidade de tratamento aplicada; grupo I infiltrante resinoso Icon®, grupo II clareamento e grupo III clareamento seguido de infiltração resinosa Icon®. Para cada modalidade de tratamento, 10 corpos-de-prova foram testados para rugosidade superficial e outros 10 para microdureza. WSLs foram artificialmente induzidos em todas as amostras e, após o tratamento, todas as amostras foram submetidas ao desafio erosivo. A rugosidade de superfície foi medida por microscopia de força atômica em modo de contato intermitente (AFM) e a microdureza Vickers foi medida inicialmente, após a indução de WSLs, após o tratamento e após o desafio ácido. Resultados: Os grupos I e III apresentaram redução significativa da rugosidade superficial após o tratamento, enquanto o grupo II apresentou aumento significativo. Os grupos I e III apresentaram aumento significativo na microdureza após o tratamento, enquanto o grupo II apresentou aumento insignificante. Os três grupos testados mostraram aumento significativo nos valores de rugosidade superficial e redução significativa na microdureza após o desafio erosivo. Conclusão: O infiltrante resinoso e o clareamento seguido de infiltração resinosa reduziram a rugosidade de superfície e aumentaram a microdureza dos WSLs. As três modalidades de tratamento falharam em resistir ao desafio erosivo, resultando em aumento da rugosidade de superfície e redução da microdureza.(AU)