Objectives New generation intraoral scanners are promoted to be suitable for digital scans of long-span edentulous spaces and completely edentulous arches; however, the evidence is lacking. The current study evaluated the accuracy of intraoral scanning (IOS) in partially and completely edentulous arch models and analyzed the influence of operator experience on accuracy. Materials and methods Four different resin models (completely and partially edentulous maxilla and mandible) were scanned, using a new generation IOS device (n = 20 each). Ten scans of each model were performed by an IOS-experienced and an inexperienced operator. An industrial high-precision scanner was employed to obtain reference scans. IOS files of each modeloperator combination, their respective reference scan files (n = 10 each; total = 80), as well as the IOS files from each model generated by the same operator, were superimposed (n = 45; total = 360) to calculate trueness and precision. An ANOVA for mixed models and post hoc t tests for mixed models were used to assess group-wise differences (α = 0.05). Results The median overall trueness and precision were 24.2 μm (IQR 20.7-27.4 μm) and 18.3 μm (IQR 14.4-22.1 μm), respectively. The scans of the inexperienced operator had significantly higher trueness in the edentulous mandibular model (p = 0.0001) and higher precision in the edentulous maxillary model (p = 0.0004). Conclusion The accuracy of IOS for partially and completely edentulous arches in in vitro settings was high. Experience with IOS had small influence on the accuracy of the scans. Clinical relevance IOS with the tested new generation intraoral scanner may be suitable for the fabrication of removable dentures regardless of clinician's experience in IOS.

The drag-reducing ability of the seal fur surface was tested in a rectangular channel flow using water and a glycerol-water mixture to measure the pressure drop along the channel in order to evaluate friction factors in a wide range of Reynolds number conditions, and the drag reduction effect was confirmed quantitatively. The maximum reduction ratio was evaluated to be 12% for the glycerol-water mixture. The effective range of the Reynolds number, where the drag reduction was remarkable, was wider for the seal fur surface compared to that of a riblet surface measured in this channel and in previous studies. It was also found that for the seal fur surface, unlike riblets, any drag increase due to the effect of surface roughness was not found up to the highest Reynolds number tested. Measurements of the seal fur surface using a 3D laser microscope revealed that there were riblet-like grooves, composed of arranged fibers, of which spacings were comparable to that of effective riblets and were distributed in various wavelengths. Using LDV measurements, it was found that the difference in the mean velocity scaled by the outer variable among the smooth, riblet, and seal fur surfaces did not appear at any spanwise locations. Streamwise turbulence intensity for the seal fur surface was found to be about 5% smaller than those for smooth and riblet surfaces.

The effectiveness of a previously developed unsintered hydroxyapatite (uHA) and poly(L-lactic acid) (PLLA) hydrophilic membrane as a resorbable barrier for guided bone regeneration (GBR) was evaluated. Critical-size 8-mm diameter bone defects were surgically generated in the parietal bones of 24 12-week-old male Wistar rats, which were then divided into three groups in which either a uHA/ PLLA or a collagen membrane or no membrane (control) was placed onto the bone defect. Following sacrifice of the animals 2 or 4 weeks after surgery, bone defects were examined using microcomputed tomography and histological analysis. Bone mineral density, bone mineral content, and relative bone growth area values 2 or 4 weeks after surgery were highest in the uHA/PLLA group. Four weeks after surgery, the relative bone growth area in the uHA/PLLA group was larger than that in the collagen group. The resorbable uHA/PLLA membrane is thus potentially effective for GBR.

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