Establishment of new ascites hepatomas

The hepatomas of the Donryu rats induced by feeding 4.dimethyl. aminoazobenzene for more than 191 days were transplanted into the brain of newborn rats of the same strain and the formed tumors were transplanted into the peritoneal cavity of adult rat of the same strain for the purpose to obtain transplantable strain of ascites hepatoma. As the result 4 lines of transplantable ascites hepatomas have been establised. The cells of these 4 hepatomas resembled their original liver tumor cells, respectively, showing the similar morphologic appearance to their mother cell. They showed less differentiated or more malignant characteristics in those taken from the tumor at the more advanced stages of DAB feeding. The liver tissues from the rat fed on DAB for 191 days had no tumor inducing activity when they were inoculated into the brains of the newborn rats (C 74). The liver tumors of the rats fed for more than 236 days produced the tumors in brain, which was serially transplantable (C 82), and kept the original morphologic pattern through serial transplantation and even in those growing in ascites. The tumor cells of the C 82 line showed the least malignancy among the 4 lines of ascites hepatoma established. Those of the C 83 line, which originated from the rat fed on DAB for 264 days, demonstrated the type of well.differentiated liver cell carcinoma with the trabecular arrangement of the tumor cells, but in ascites form they grew more rapidly than those of C 82. Those having most malignant characteristics were the cells of C 84.A which were derived from the rat fed on DAB for 312 days, and they were of the type of undifferentiated liver cell carcinoma. The island forming capacity of the C 84·A cells was the weakest among those of the 4 lines. C 84·B cells were also those derived from the same rat as that from which C 84.A originated and also showed the type of poorly differentiated liver cell carcinoma, but less malignant than those of C 84.A.</p

Comparison of cerebral cortex activation induced by tactile stimulation between natural teeth and implants

The purpose of this study was to assess the cortical-level sensory differences between natural teeth with a periodontal membrane and dental implants. We used functional near-infrared spectroscopy (fNIRS) to measure brain activity in the cerebral cortex of 12 patients who had both natural teeth and dental implants in the lower molar region. Painless vibratory tactile stimulation was performed on both the natural teeth and the dental implants. Activation was seen in the somatosensory cortex during stimulation of both natural teeth and dental implants. A comparison of cortical activation showed no significant differences between natural teeth and dental implants. These results indicate the possible existence of sensory input to the cerebral cortex via dental implants as well as natural teeth, and thus suggest that may not only the periodontal membrane be involved in the signaling pathway. The data from this experiment may help us for understanding the neural mechanisms underlying natural teeth and dental implants

Study protocol for a multi-center, randomized controlled trial to develop Japanese denture adhesive guidelines for patients with complete dentures : the Denture Adhesive Guideline trial : study protocol for a randomized controlled trial

Background: Denture adhesives, characterized as medical products in 1935 by the American Dental Association, have been considered useful adjuncts for improving denture retention and stability. However, many dentists in Japan are hesitant to acknowledge denture adhesives in daily practice because of the stereotype that dentures should be inherently stable, without the aid of adhesives. The aim of this study is to verify the efficacy of denture adhesives to establish guidelines for Japanese users. The null hypothesis is that the application of denture adhesives, including the cream and powder types, or a control (isotonic sodium chloride solution) would not produce different outcomes nor would they differentially improve the set outcomes between baseline and day 4 post-application. Methods: This ten-center, randomized controlled trial with parallel groups is ongoing. Three hundred edentulous patients with complete dentures will be allocated to three groups (cream-type adhesive, powder-type adhesive, and control groups). The participants will wear their dentures with the denture adhesive for 4 days, including during eight meals (three breakfasts, two lunches, and three dinners). The baseline measurements and final measurements for the denture adhesives will be performed on the first day and after breakfast on the fourth day. The primary outcome is a general satisfaction rating for the denture. The secondary outcomes are denture satisfaction ratings for various denture functions, occlusal bite force, resistance to dislodgement, masticatory performance, perceived chewing ability, and oral health-related quality of life. Between-subjects comparisons among the three groups and within-subjects comparisons of the pre- and post-intervention measurements will be performed. Furthermore, a multiple regression analysis will be performed. The main analyses will be based on the intention-to-treat principle. A sample size of 100 subjects per group, including an assumed dropout rate of 10 %, will be required to achieve 80 % power with a 5 % alpha level. Discussion: This randomized clinical trial will provide information about denture adhesives to complete denture wearers, prosthodontic educators, and dentists in Japan. We believe this new evidence on denture adhesive use from Japan will aid dentists in their daily practice even in other countries

Accuracy of Dental Models Fabricated Using Recycled Poly-Lactic Acid

Based on the hypothesis that the fabrication of dental models using fused deposition modeling and poly-lactic acid (PLA), followed by recycling and reusing, would reduce industrial waste, we aimed to compare the accuracies of virgin and recycled PLA models. The PLA models were recycled using a crusher and a filament-manufacturing machine. Virgin PLA was labeled R, and the first, second, and third recycles were labeled R1, R2, and R3, respectively. To determine the accuracies of the virgin and reused PLA models, identical provisional crowns were fitted, and marginal fits were obtained using micro-computed tomography. A marginal fit of 120 µm was deemed acceptable based on previous literature. The mesial, distal, buccal, and palatal centers were set at M, D, B, and P, respectively. The mean value of each measurement point was considered as the result. When comparing the accuracies of R and R1, R2, and R3, significant differences were noted between R and R3 at B, R and R2, R3 at P, and R and R3 at D (p < 0.05). No significant difference was observed at M. This study demonstrates that PLA can be recycled only once owing to accuracy limitations

Positive Effects of Saliva on Oral Candidiasis: Basic Research on the Analysis of Salivary Properties

The major causes of oral candidiasis include decreased salivary flow rate and the use of ill-fitting dentures. However, the relationships among prosthetic treatment, saliva, and Candida albicans have not been elucidated. This study aimed to examine the effects of prosthetic treatment and changes in saliva (mainly the salivary flow rate) on oral candidiasis symptoms. Participants requiring prosthetic treatment underwent testing for C. albicans, salivary flow rate, intraoral symptoms, and bite force at the initial visit and four months after treatment to evaluate pretreatment and post-treatment changes. The relationships among C. albicans, salivary flow rate, dentures, and intraoral symptoms were analyzed using multiple regression analysis. Denture treatment improved activity against C. albicans as well as the salivary flow rate, intraoral symptoms, and masticatory function. Multiple regression analysis revealed that changes in the stimulated salivary flow rate due to prosthetic treatment significantly improved C. albicans detection (p = 0.011), intraoral symptoms (p = 0.037), and bite force (p = 0.031). This study showed that prosthetic treatment improved salivary flow and intraoral symptoms and confirmed the influence of stimulated salivary flow rate changes

Chewing-induced regional brain activity in edentulous patients who received mandibular implant-supported overdentures: a preliminary report.

We used functional magnetic resonance imaging (fMRI) to investigate the change in brain regional activity during gum chewing when edentulous subjects switched from mandibular complete dentures to implant-supported removable overdentures