Low-temperature, low-pressure gas plasma application on Aspergillus brasiliensis, Escherichia coli and pistachios.

AIM: The aim of this study was to investigate the effect of plasma-enhanced chemical vapour deposition (PECVD) treatment on selected bacteria and spores and to contribute to the understanding of the synergistic effect of UV-directed plasma. METHODS AND RESULTS: The experiments were conducted on pure cultures of Aspergillus brasiliensis and Escherichia coli and on naturally contaminated pistachios that were exposed to pure oxygen-, pure argon- and to a mixture of oxygen-argon-generated plasma for different treatment times and at different micro-organism concentrations. Optical emission spectroscopy (OES) measurements were performed to observe the active species in the plasma. After exposure, the effectiveness of decontamination was assessed through microbiological techniques by calculating the growth reduction on a logarithmic scale. A treatment time of 30 min resulted in a 3·5 log reduction of A. brasiliensis using pure oxygen or argon, while treatment times of 5 min, 1 min and 15 s resulted in a 5·4 log reduction using a mixture of argon and oxygen (10 : 1 v/v). Treatment times of 1 min and 30 s resulted in a 4 log reduction of E. coli with oxygen and argon, respectively, which led to a complete elimination of the micro-organisms. Two-log reductions of fungi were achieved for pistachios after a treatment time of 1 min. CONCLUSIONS: These results suggest that this newly designed plasma reactor offers good potential applications for the reduction in micro-organisms on heat-sensitive materials, such as foods. The plasma that was generated with Ar/O2 was more effective than that which was generated with pure oxygen and pure argon. SIGNIFICANCE AND IMPACT OF THE STUDY: An improvement in the knowledge about PECVD mechanisms was acquired from the chemical and biological points of view, and the suitability of the method for treating dry food surfaces was demonstrated.

[Considerations on composite odontoma]. / Alcune considerazioni sull'odontoma composto.

Odontoma in most cases presents in the mixed dentition period and can remain for long unrecognised. Asymptomatic during its long latency period, odontoma gives signs of life only in an aspecific way: the absence in the arch of one or more teeth should direct the clinician towards investigations which make it possible to identify the cause, as this may be due to odontomas. Radiography may clearly point to the presence of this lesion and may direct the operator towards surgical/orthodontic treatment so as to restore to the dental arch a tooth that would otherwise have remained included. It is, furthermore, important to remove the lesion, even though it is quite benign, because it is easily subject to septic complications. It should be recalled that it is always necessary to back up clinical with histological diagnosis so as to differentiate the odontoma from other lesions with different prognosis and therapy.