The purpose of this study is to evaluate clinical performance of 3D dental scanners (intra-oral scanners and a laboratory scanner) from the point of view of trueness and precision. Two types of reference models of the mandible were fabricated, in which ball abutments were connected to implants. A computer numerical control coordinate measuring machine (CNCCMM), intra-oral scanners (Lava COS, TRIOS) and a laboratory scanner (ARCTICA) were used in measuring the reference models. Two ball abutments were scanned, and the distance between the center of balls were calculated as the values of the trueness and precision. Regarding trueness, the value obtained from Lava COS was significantly different from the values obtained from TRIOS or ARCTICA (p<0.05). Regarding the precision, the data of Lava COS was significantly different than the data of ARCTICA (p<0.05). Deviation of trueness and precision in ARCTICA was the smallest, while Lava COS was the greatest. Moreover, results of the intra-oral scanning were operator dependent (p<0.05). Those results suggested that the laboratory scanner had a stable trueness and precision regardless of the distance because it was capable of a wide-range scanning. Conversely, intra-oral scanners produce the image by connecting and superimposing the small 3-D data, resulting in small errors. It was concluded that some could be intra-oral scanners might have comparable performance to conventional impression technique and useful in clinical practice.

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The osteoblast differentiation on the endosseous titanium (Ti) implants is required for successful osseointegration, which could be promoted by various cytokines. Recent studies suggested a pro-inflammatory cytokine, IL-17F, could be a candidate cytokine for inducing the cellular response in the early phase of osteogenesis. However, the role of IL-17F as well as another member of the IL-17 superfamily, IL-17A, in regulating the osteoblast differentiation on Ti surfaces remains unclear. In this study using a rat model, the first molars in both maxillary quadrants were extracted and a Ti bar (φ1.0×2.4mm) was topically applied to one extraction socket. One to 7 days after application, the animals were sacrificed, and the tissue samples from both extraction sockets were collected. IL-17F and IL-17A in the tissue specimens were detected by nested RT-PCR. Furthermore, the direct effect of IL-17s on the cultured preosteoblast MC3T3-E1 cells on Ti disks was examined. In vivo studies indicated the frequency of IL-17F-positive samples from the Ti-applied sockets increased significantly on day 3, whereas the frequency of IL-17A-positive samples gradually increased up to day 3 regardless of Ti application. In vitro studies suggested that IL-17F could stimulate the MC3T3-E1 cells on Ti disks to increase the expressions of alkaline phosphatase and bone sialoprotein. Thus, IL-17F could enhance the osteoblast differentiation on Ti surfaces via the upregulation of osteoblast differentiation markers.

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Streptococcus anginosus infection could be closely related with oral squamous cell carcinoma, although the mechanism underlying carcinogenesis is still unknown. Recent studies suggested that the aberrant expression of activation-induced cytidine deaminase (AID) in the epithelial cells could result in the generation of nucleotide alterations in tumor-related genes and possible malignant transformation of the AID-expressing cells. In this study using the 17 surgical tissue specimens, a possible involvement of S. anginosus infection and aberrant AID expression in oral squamous cell carcinoma was assessed by the species-specific PCR and RT-qPCR. Further, the aberrant AID expression and NF-κB activation were examined by a dual luciferase assay and RT-qPCR in three epithelial cell lines and the primary human gingival epithelial cells after stimulation with a bioactive antigen of S. anginosus, SAA. The results indicated that both S. anginosus infection and aberrant AID expressions were frequently observed in the tissue specimens (47% and 41%, respectively), and S. anginosus infection was significantly correlated with the aberrant AID expression. The stimulation of the cultured cells with SAA could induce the NF-κB activation and aberrant AID expression in all the epithelial cells tested, and the addition of an inhibitor of NF-κB activation abrogated the aberrant AID expression. Thus, S. anginosus infection could be closely related with oral squamous cell carcinoma through the induction of the aberrant AID expression by S. anginosus antigen.

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The aim of this study was to evaluate the safety of dental metals installed in patients in ultra-high-field MRI. Deflection angle, heating by radiofrequency, and artifacts of dental metals were measured at 7 Tesla MR system. Magnetic field-related translational deflection force was measured using a tailor-made instrument at 3 Tesla and 7 Tesla MR system. Samples were 9 types of dental metals. MRI-related heating and artifacts were also examined using a gelled-agarose-filled-head/neck phantom at 7 Tesla MRI. Twenty grams-ingot of pure titanium and Co-Cr alloy were also examined at 7 Tesla to observe the volume dependent effects. In the heating test, non-metal embedded-phantom was examined as a control. Deflection angle of 20 grams ingot of Co-Cr alloy and Ni-Cr alloy showed the value of 17.0° and 31° at 7 Tesla, respectively. Ni-Cr alloy should be removed prior to the inspection because deflection angle in 7 Tesla which close to 45° that was indicated as dangerous value by ASTM. In contrast, deflection angles of other metals were 10° or less, and inspection can be carried out safely at both 3 Tesla and 7 Tesla. In the heating test, it was indicated that impact of ultra-high field MRI on those materials is not considerable, because pure titanium and control showed a maximum temperature increase of 0.5℃ by 2D-SE T2WI scanning and the temperature increase of the other samples were 0.5℃ or less by all imaging. An ortifact of pure titanium ingot was 3-8 times in axial slice, 4-7 times in coronal slice as large as sample images. The maximum artifact of axial slice and coronal slice was observed by 3D-FSE T2WI imaging and 2D-SE T2WI imaging. Those results suggested that the image obtained by each scanning may vary depending on the type of metal.

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Taste disorder patients are increasing along with the increase of the elderly population. In dental clinics, patients often complain of taste disorder when the palate is covered with removable dentures, but the causal relationship is not yet clear. The purpose of this study is to clarify the cause of the taste disorder as it relates to the wearing of dentures. Taste disorder by the denture wearing was evaluated objectively from the point of view of higher brain function response using fMRI. We investigated the brain activity by taste stimulation. 15 healthy subjects received taste solution on the palate only. To examine the change of the brain activity of the taste by the palatal covering, 14 healthy subjects received taste stimulus. Subjects were divided to two conditions, in which the palate was not covered (control) or the palate was covered (palate covering). Taste solution was quinine hydrochloride solution that has been set in the recognition threshold of each subject as bitter stimulus. Artificial saliva containing the 25 mM KCl and 25 mM NaHCO3 was used as a rinse. The primary gustatory cortex was activated in response to bitter taste stimulation for the palate. By the palatal coverage, activation was accepted in both conditions by the primary and secondary gustatory cortex. The extents of activation in the primary and secondary gustatory cortex were significantly lower than control, and the activation intensity of the primary gustatory cortex was lower than control. Present results suggested that palate coverage from dentures might cause the attenuation of gustatory response. Furthermore, it is suggested that objective rating of influence exerted on the gustatory response by palate covering could be possible.

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