Comparison of linear transverse measures between plaster and resin printed digital models.

The aim of this study was to test for dimensional variations between plaster models recorded with alginate impression and printed 3D physical replicas from an .stl file digitized with an intra-oral scanner. Eighty arches (maxillary and mandibular) from 40 different patients were analyzed. Classic alginate impressions and digital recordings with an intraoral scanner were taken on the same day, for both arches of each patient. Digital recordings were then printed into resin models. The linear intercanine (IC) and intermolar (IM) distances were measured with a manual electronic caliper and then compared. The measurements were repeated twice for each distance to verify repeatability with the intraclass correlation coefficient (ICC). The Student’s t test for paired data was used to compare the two sets of impressions. The repeatability of the measures was assessed as ICC values were higher than 0.98. The values of the IC and IM lengths showed a statistically significant difference, but not clinically significant as it was less than 0.1 mm, between the two techniques.

Palatal morphology changes in post-stroke patients measured by geometric morphometrics.

This study aimed to describe longitudinal palatal shape changes in post-stroke patients when compared to a sample of healthy subjects through linear measurements and geometric morphometrics. The 3D palatal scanned models of seven stroke patients having a 1-year post-stroke follow-up were matched with seven control subjects of the same age group (range 50-87 years). Intercanine, intermolar distances and palatal height were measured. 3D images were also analysed through geometric morphometrics to assess changes in the shape of the palate from T0 to T1 (1 year after the stroke). Principal component analysis was used to describe shape morphology changes, and visual colour maps were used to qualitatively assess differences between T0 and T1. No changes were detected nor in linear measures neither in palatal shape in healthy subjects from T0 to T1. The palates of stroke patients showed no linear differences either. However, when visualising shape changes through colour maps, the lateral aspects of the palatal vault were slightly narrower in T1, with respect to T0 in stroke patients. This may be attributed to altered tongue function following the stroke.

Comparative physical tests on segmented polyurethanes for cardiovascular applications.

In order to select a candidate segmented polyurethane (SPU) elastomer for cardiovascular prostheses, a series of physical tests was carried out on five commercially available biomedical polyurethanes. The tests were performed on uniformly thick sheets (0.2-0.3 mm), obtained by solvent casting from THF (Cardiothane 51, Pellethane 2363 80A, Estane 5714 F1, and Estane 58810) or DMAC (Biomer). Tensile mechanical tests at 23 and 37 degrees C showed for all the copolymers typical stress/strain behaviour of elastomeric materials, with small individual differences. Hydrolytic stability was investigated at 85, 60, and 37 degrees C, at increasing times of exposure (96-168 h), in water or alkaline buffer (pH = 10). As indicated by gel permeation chromatography, in almost all cases a degradation of the molecular weight (particularly the M w) was noticed after the hydrolytic tests, but tensile, thermal (by DSC) and dynamic mechanical properties were substantially not affected. SEM was also performed on the materials, before and after the hydrolytic tests. Changes in the morphology of the materials (related to degradation effects) was observed only in the case of Biomer, as shown also by the thermomechanical analyses. After this first series of physical tests, a clear choice of a particular SPU among the five investigated was not found.