Bacteriological and mechanical impact of the Sterrad sterilization method on personalized 3D printed guides for mandibular reconstruction.

Surgical cutting guides are increasingly used for maxillofacial reconstruction. They are usually provided by laboratories. In recent years, surgical teams have published studies on the possibility of manufacturing their own cutting guides thanks to 3D printers. The object of this study is to analyze the impact of the sterilization on the surface of those personalized models and to assess the effectiveness of sterilization. Using the data from high-resolution CT scan of patient, 3D models were generated through computerized assisted design and fabricated with a 3D printer using Acrylonitrile Butadiene Styrene (ABS). For the sterilization, a Sterrad method was used. In order to evaluate the effectiveness of sterilization, 3D models were artificially contaminated with several bacterial reference strains, sterilized and finally cultured. The surfaces and mechanical modifications were analyzed before and after sterilization with infrared spectrometry, surface contact angle, extensometer, scanning electron microscopy and atomic force microscopy. Ten models of different shapes and 24 samples were fabricated, sterilized and analyzed. The 3D models were designed in 48 h, printed in an average of 122 min and underwent a 47 min cycle of sterilization. All experimentally contaminated 3D models were negative in culture, with at least, a six log reduction of the initial inoculum. The hydrophobicity and roughness of the surface suffered few changes. The reproducibility of this procedure was proved by identical results in the three sterilization rounds. Using Sterrad process for the sterilization of ABS printed material doesn't represent a bacterial risk for the patient. It is a feasible and safe innovative reconstructive method that can save time particularly for oncological cases.

Very low oral doses of vitamin B-12 increase serum concentrations in elderly subjects with food-bound vitamin B-12 malabsorption.

The BOSSANOVA study, a randomized double-blind trial, was designed to test the ability of very low oral doses of vitamin B-12 to increase the serum vitamin B-12 concentration in elderly subjects with food-bound vitamin B-12 malabsorption, and to determine whether there was a dose response. We also aimed to quantitatively assess the most efficient dose to be added to flour in addition to folic acid (flour cofortification with vitamin B-12 and folic acid). Sixty-seven patients were randomly assigned to 1 of 6 groups receiving various daily oral doses of vitamin B-12 (i.e., 2.5, 5, 10, 20, 40, or 80 microg/d) for 30 d. The dose-response was tested for different biological variables using a mixed model, taking into account the variable's initial value (between-subject effect), a linear log-dose effect, and a linear log (dosextime) interaction, where time was d 15 or d 30. We planned to determine the amount of oral vitamin B-12 that would increase the serum vitamin B-12 concentration by 37 pmol/L (50 ng/L). Significant between-subject effects were found for serum vitamin B-12, plasma homocysteine, and methylmalonic acid concentrations, but a log-dose effect was found only for vitamin B-12 (P<0.001). The slope of the line tended to be higher (P=0.07) at d 30 than at d 15. For a mean serum vitamin B-12 increase of 37 pmol/L, a dose of 5.9 (95% CI, 0.9-12.1) microg/d was needed. We concluded that very low oral doses of vitamin B-12 increased serum vitamin B-12 concentrations in elderly subjects with subclinical vitamin B-12 deficiency, following a log-dose pattern. Our results could be beneficial in the design of a public health program for safe flour cofortification with folic acid.