Morena Petrini

Fabrication and characterization of biomimetic ceramic/polymer composite materials for dental restoration

OBJECTIVE Conventional dental composites with randomly dispersed inorganic particles within a polymer matrix fail to recapitulate the aligned and anisotropic structure of the dentin and enamel. The aim of the study was to produce a biomimetic composite consisting of a ceramic preform with graded and continuously aligned open pores, infiltrated with epoxy resin. METHODS The freeze casting technique was used to obtain the hierarchically structured architecture of the ceramic preforms. Optical and scanning electron microscopy (SEM) and differential thermal analysis and thermogravimetry (TG-DTA) were used to characterize the samples. Three point bending test and compression test were also performed. RESULTS All analysis confirmed that the biomimetic composite was characterized by a multi-level hierarchical structure along the freezing direction. In the bottom layers close to the cooling plate (up to 2mm thick), a randomly packed ceramic with closed pores were formed, which resulted in incomplete infiltration with resin and resultant poor mechanical propertiesof the composite. Above 2mm, all ceramic samples showed an aligned structure with an increasing lamellae spacing (wavelength) and a decreasing wall thickness. Mechanical tests showed that the properties of the composites made from ceramic preforms above 2mm from cooling plate are similar to those of the dentin. SIGNIFICANCE The fabrication processing reported in this work offers a viable route for the fabrication of biomimetic composites, which could be potentially used in a range of dental restorations to compete with the current dental composites and ceramics.

In vitro inactivation of Enterococcus faecalis with a led device.

Non-coherent light-emitting diodes (LEDs) are effective in a large variety of clinical indications; however, the bactericidal activity of LEDs is unclear, although the effectiveness of such lights is well known. Currently, no studies have examined the effects of NIR-LED on bacteria. The aims of this study were to verify the antibacterial activity of 880-nm LED irradiation on a bacterial suspension of Enterococcus faecalis and to compare it with the actions of sodium hypochlorite (NaOCl) and the concurrent use of both treatments. Before we proceeded with the main experiment, we first performed preliminary tests to evaluate the influence of such parameters as the distance of irradiation, the energy density, the irradiation time and the presence of photosensitizers on the antimicrobial effects of LEDs. After treatment, the colony forming units per milliliter (CFU/mL) was recorded and the data were submitted to ANOVA and Bonferroni post hoc tests at a level of significance of 5%. The results showed that LED irradiation, at the parameters used, is able to significantly decrease E. faecalis viability in vitro. The total inhibition of E. faecalis was obtained throughout concurrent treatment of LED and NaOCl (1%) for 5min. The same antimicrobial activity was confirmed in all of the experiments (p<0.05), but no statistically significant differences were found by varying such parameters as the distance of irradiation (from 0.5mm to 10mm), energy density (from 2.37 to 8.15mJ/s), irradiation time (from 5min to 20min) or by adding toluidine blue O (TBO).

Gold nanoparticles as scaffolds for poor water soluble and difficult to vehiculate antiparkinson codrugs

We report the facile and non-covalent preparation of gold nanoparticles (AuNPs) stabilized by an antiparkinson codrug based on lipoic acid (LA). The obtained AuNPs appear stable in both dimethyl sulfoxide and fetal bovine serum and able to load an amount of codrug double the weight of gold. These NPs were demonstrated to be safe and biocompatible towards primary human blood cells and human neuroblastoma cells, one of the most widely used cellular models to study dopaminergic neural cells, therefore are ideal drug carriers for difficult to solubilize molecules. Very interestingly, the codrug-stabilized AuNPs were shown to reduce the accumulation of reactive oxygen species in SH-SY5Y cells treated with LD and did not change total oxidant status levels in cultured human blood cells, thus confirming the antioxidant role of LA although bound to AuNPs. The characterization of AuNPs in terms of loading and stability paves the way for their use in biomedical and pharmacological applications.

Cyclic nucleotide phosphodiesterase activity in stem cells of human periodontal ligament (PDL-MSCs) before and after osteogenic induction.

OBJECTIVE The aim of this work was to evaluate both the level of endogenous cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cAMP) and phosphodiesterase activity in mesenchymal stem cells (MSCs) before and during the osteogenic induction. STUDY DESIGN Samples were organized into control (nondifferentiated) and test groups which were analyzed at 3 different time points: 1, 2, and 4 weeks. Periodontal ligament MSCs were isolated and then expanded in an MSCM medium while cyclic nucleotide levels and phosphodiesterase activity were assessed. RESULTS cAMP and cGMP levels were markedly higher in the first week than in the following stages. Similarly, PDE activity increased during the first week and reached the peak in the second week. CONCLUSIONS This work validates that cAMP, cGMP, and PDE activities are important factors in the first phase of the osteogenic induction of a human stem cell.

Effect of pre-operatory low-level laser therapy on pain, swelling, and trismus associated with third-molar surgery

Background The extraction of impacted third molars is commonly associated to pain, edema, trismus, limited jaw opening and movements. The aim of this retrospective study is to verify if pre-surgical low-level laser therapy (LLLT) associated with the extraction of impacted lower third molars could add benefits to the postoperative symptoms respect LLLT performed only after surgery. Material and Methods Data from 45 patients subjected to a surgical extraction of lower third molars were pooled and divided into three groups. Patients that received only routine management were inserted in the control group. Group 1, were patients that received LLLT immediately after surgery and at 24 hours. In group 2 were included patients treated with LLLT immediately before the extraction and immediately after the end of the procedure. Data were analyzed using linear regression and descriptive statistics. Results Both laser-treated groups were characterized by minor events of post-surgery complications of pain, edema, trismus. The use of NSAIDs in the first 24 hours was significantly inferior in Group 2. Conclusions Pre-surgical LLLT treatment seems to increase the analgesic effect of LLLT. However, trismus and edema were reduced in both laser treated groups, independently from the period of irradiation. Key words:Laser, LLLT, pain, surgery, extraction, third molars, wisdom teeth.

In vitro antimicrobial activity of LED irradiation on Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen responsible of many deaths due to nosocomial pneumonia each year. It is particularly resistant to many different classes of antibiotics and disinfectants. For all these reasons, there is the necessity to find novel approaches of treatment. The aim of this study was to evaluate the effect of 880nm light emitting diodes (LED) irradiation on P. aeruginosa, in vitro. Different LED irradiation parameters (time, energy output and the addition of methylene blue and chlorhexidine) have been tested in order to evaluate the effects on this bacterium. After treatment, the colony forming units per milliliter (CFU mL-1) were recorded and the data were submitted to ANOVA and Bonferroni post hoc tests at a level of significance of 5%. A statistical significant reduction of bacterial count has been registered after 5min of LED irradiation. The antibacterial effect was directly proportional to irradiation time and the output energy. The pre-treatment with methylene blue, seems to be not effective against P. aeruginosa, independently from irradiation parameters. On the contrary, the contemporary action of LED and chlorhexidine has shown a great reduction of bacterial count that was statistical significant respect chlorhexidine and LED alone. The effect of LED irradiation was visible also after 24h, when a lower bacterial count characterized all irradiated samples respect controls.