Characterisation of the antibacterial effect of polyethyleneimine nanoparticles in relation to particle distribution in resin composite.

OBJECTIVES: To characterise the antibacterial effect of resin composite incorporating cross-linked quaternised polyethyleneimine (QPEI) nanoparticles in relation to their distribution in the bulk material. METHODS: The antibacterial effect of resin composite incorporating QPEI nanoparticle was tested against various oral pathogens, including Enterococcus faecalis, Streptococcus mutans, Actinomyces viscousus, Lactobacilus casei and whole saliva. Nanoparticle distribution in the modified resin composite was assessed using X-ray photoelectron spectroscopy (XPS). Additionally, the degree of conversion was recorded. RESULTS: Total bacterial inhibition was detected against all the tested pathogens following direct contact with the outer surface of the modified resin composite. Similarly, the inner surface of the modified resin composite caused total inhibition. Electron microscope images showed bacterial death. XPS revealed surface I(-) ions on both the outer and the inner surfaces of the modified composite. No I(-) ions were detected in the unmodified composite. Nanoparticle distribution was higher on the inner surface of the modified composite. The composite's degree of conversion was unaffected by nanoparticle addition. CONCLUSIONS: QPEI nanoparticles represent a new generation of antibacterial nanoparticles which are highly promising in preventing bacterial recontamination when restoring teeth.

Platelet derived growth factor secretion and bone healing after Er:YAG laser bone irradiation.

Er:YAG laser irradiation has been reported to enhance wound healing. However, no studies have evaluated the synthesis of growth factors after laser irradiation. The present study investigated the effects of laser irradiation on the amount of secretion of platelet derived growth factor (PDGF) in the wound, clarifying the effects of the Er:YAG laser on the bone healing. Osteotomies were prepared in the tibiae of 28 rats using an Er:YAG laser (test group). Maximum power of 8 watts, energy per pulse of 700 mJ, and frequency up to 50 Hz were used. The laser was used with external water irrigation, a spot size of 2 mm, energy per pulse of 500 to 1000 mJ/pulse, and energy density of 32 J/cm(2). Twenty eight additional rats served as a control group and their osteotomies were prepared with a drill 1.3 mm in diameter at 1000 rpm, with simultaneous saline irrigation. Two rats from the tested group and 2 from the control group were sacrificed on each day following surgery (1-14 days), and the tissue specimens were prepared for histologic evaluation. Immunohistochemical staining with anti-PDGF was performed after histologic examination. The difference between the PDGF staining intensities of the 2 treatment groups was analyzed using a multivariate logistic regression test. A significant rise in PDGF staining occurred in both groups 2-3 days following surgery. However, while high PDGF counts remained for the 2-week experimental period in the laser group, PDGF levels in the control group returned to baseline levels 8 days post surgery. The 2 groups (laser and control) were found to be different throughout the experiment, and the rat type was found to be a significant predictor (P  =  .000011). The present study demonstrated that Er:YAG laser irradiation seems to stimulate the secretion of PDGF in osteotomy sites in a rat model. It is possible that the high levels of PDGF are part of the mechanism that Er:YAG irradiation enhances and improves the healing of osteotomy sites.

Antibacterial effect of polyethyleneimine nanoparticles incorporated in provisional cements against Streptococcus mutans.

BACKGROUND: Frequently provisional restorations require long-term permanence in the oral cavity, thus an antibacterial effect is desirable. We hypothesized that this effect may be achieved by incorporating polyethyleneimine (PEI) nanoparticles into provisional cements. METHODS: The nanoparticles antibacterial effect incorporated at 0.5%, 1%, and 2% w/w into provisional cement, was studied in vitro. The antibacterial effect against Streptococcus mutans and Enterococcus faecalis was tested using direct contact test. The data was analyzed using the ANOVA test, with the Dunnett test for multiple pairwise comparisons. RESULTS: A strong antibacterial effect was evident in all test groups after an aging period of 14 days against S. mutans and E. faecalis (p < 0.05). A significant effect was found between study groups 0.5% w/w and 1% w/w group, as well as between study groups 0.5% w/w and 2% w/w for E. faecalis (p < 0.05). No significant difference was found between study groups 1% w/w and 2% w/w. The growth rate graphs depict an effective bacteria inhibition starting from 1% w/w. CONCLUSION: PEI nanoparticles incorporated at low concentrations in a provisional cement exhibit antibacterial effect against S. mutans and E. faecalis for a period of 14 days. The minimum effective concentration suggested is 1% w/w. CLINICAL IMPLICATIONS: Incorporation of nanoparticles may prevent caries and inflammation, and thereby improve the results of the prosthetic treatment. Further investigation is necessary on the effect on mechanical properties and clinical relevance.