Shinsuke Sadamori

The dimensional accuracy of rectangular acrylic resin specimens cured by three denture base processing method

The dimensional accuracy of rectangular acrylic resin specimens was examined when they were processed by three methods: a conventional method, the SR-Ivocap system, and a microwave curing method. The dimensional accuracy was evaluated by the change of the distance vector V, which is calculated by means of measurements of the distances between fixed points on specimens. The specimen cured by the SR-Ivocap system exhibited less dimensional change (p less than 0.05) than those cured by the conventional and the microwave curing methods. The SR-Ivocap system might produce a more accurate denture base than the conventional and the microwave curing methods.

The usage period of dentures and their residual monomer contents

The quantity of residual monomer content in 24 maxillary dentures was detected by gas liquid chromatography. The residual monomer contents tended to be lower in dentures used for long periods than in those used for short periods. Decreases in the quantities of residual monomer in acrylic resin dentures as a result of aging can be expressed in a hyperbola. The fitted curve also suggests that most of the loss could be accomplished in 5 years; however, complete loss of the residual monomer content takes many years.

Effect of serum concentration on Candida biofilm formation on acrylic surfaces

The biofilm formation of the oral fungal pathogen Candida on denture acrylic strips coated with saliva, serum and, saliva–serum pellicle were examined in vitro using Candida albicans (four isolates), Candida glabrata (three isolates) and Candida tropicalis (three isolates). The degree of biofilm activity varied depending upon both the isolate and the pellicle. Significantly increased biofilm activity on the pellicle (particularly serum)‐coated strips was observed with three isolates of C. albicans and another of C. glabrata on protein‐coated acrylics, with increasing concentration of serum in the pellicle. Similar trends were observed with one isolate of C. albicans and C. glabrata, although the effects of pellicles were not significant. In contrast, with all three isolates of C. tropicalis and a single isolate of C. glabrata, although the biofilm activity on the protein‐free control strips was significantly higher than that of saliva‐coated strips, the increase in activity of pellicle‐admixed biofilm depended upon the serum concentration. Candidal biofilm formation on acrylic surfaces is essentially promoted with increasing concentration of serum in the pellicle. This suggests that inflammation in the oral environment would facilitate fungal colonization on denture acrylic.

Influence of thickness and location on the residual monomer content of denture base cured by three processing methods

The influence of thickness and location on the residual monomer content of acrylic resin plates was examined when they were processed by three methods: a conventional method, fluid resin technique, and a microwave curing method. The residual monomer contents were measured by gas liquid chromatography. The levels of residual monomer were influenced by the processing methods and thicknesses of acrylic resin specimens, but not by location within the specimens. These results suggest that dimensional accuracy and stability of acrylic resin dentures could be influenced by the processing method, the thickness of the bases, and the shape and size of the dentures.

Effects of crude drugs and berberine hydrochloride on the activities of fungi

The effects of crude drugs on fungi have been used for a thousand years in China and Japan. These drugs include: Saussureae radix, Magnoliae cortex, Cinnamomi cortex, Hydrangeae dulcis folium, and Artemisiae capillarius flos. The activity of Coptidis rhizoma and Phellodendri cortex was stronger than other crude drugs against the three fungi. Berberine hydrochloride, which is a component of the two crude drugs, was investigated. Minimal inhibitory concentration values of berberine hydrochloride were 1, 0.125, and 0.5 mg/ml against Candida albicans, C. tropicalis, and C. glabrata, respectively. In C. glabrata, compared with C. albicans and C. tropicalis, berberine hydrochloride greatly inhibited the growth of fungi.

Non-specific adherence of Candida species to surface-modified glass

The nature of the physicochemical forces involved in the adherence of Candida species to a solid surface was investigated using modified glass slides. It was found that hydrophobic yeasts adhered to hydrophobic surfaces mainly by hydrophobic interactions, whereas in less hydrophobic yeasts electrostatic interactions seemed to play a more important role in adherence to the solid phase.

Factors involved in the adherence of Candida albicans and Candida tropicalis to protein-adsorbed surfaces

The adherence of Candida albicans and C. tropicalis to protein-adsorbed surfaces was investigated with surface-modified glass slides to which serum or salivary proteins were covalently bound. A specific adherence like a ligand-receptor interaction was observed between C. albicans and mucin- or salivary protein-immobilized glass slides. This interaction was eliminated by deglycosylation of the slides, suggesting that the receptor may be an oligosaccharide(s) contained mucin or saliva. A similar specific interaction was also observed between C. tropicalis and fibrinogen-immobilized glass surfaces. When the numbers of adherent cells to deglycosylated protein-immobilized glass glides were plotted against zeta potentials and contact angles of these protein-immobilized glass slides, a significant correaltion was observed between the numbers of adherent cells and zeta potentials in the case of C. albicans (r = −0.87), whereas a significant correlation was observed between cell numbers and contact angles (r = 0.82) in the case of C. tropicalis. These results suggest that the forces governing the adherence of fungi to pellicle in dentures may vary depending upon the surface properties of fungi and substrate.

The relationships between oral status, physical and mental health, nutritional status and diet type in elderly Japanese women with dementia

OBJECTIVES To suggest methods for maintaining an adequate nutritional status for elderly patients with dementia by evaluating the relationships between oral status, physical and mental health, and feeding conditions. BACKGROUND Feeding difficulties in dementia patients are related to food intake, and failure to eat may be associated with weight loss in long-term care facilities. The relationship between compromised oral function and diet is still unclear. MATERIALS AND METHODS A cross-sectional study of 94 elderly women with dementia (mean age 89.6 +/- 5.6 years) from a nursing home was undertaken to investigate their oral, physical and mental and nutritional status. RESULTS There were significant differences in serum albumin (p = 0.0284), N-ADL (p = 0.0005), NM scale (p = 0.0004) and HDS-R (p = 0.0004) between denture wearers and non-denture wearers. However, there were no significant differences in body mass index between denture wearers and non-denture wearers. CONCLUSION A suitable type of diet and assistance with feeding could maintain the nutritional status of elderly patients with dementia if they are still feeding themselves. The nutritional support team will benefit from the participation of a dentist.

Quantification of thigmotropism (contact sensing) of Candida albicans and Candida tropicalis

To quantify the thigmotropism, we adapted the our previous method using a chemotaxifilter system in combination with a bioluminescent adenosine triphosphate (ATP) assay based on firefly luciferase-luciferin system and analyzed the relationship between the ability of germ tube formation and thigmotropism of C. albicans and C. tropicalis.Both the ability to form germ tube and the amount of hyphae exhibiting thigmotropism varied depending upon both the species and strains of Candida. C. albicans formed more germ tubes than C. tropicalis. A good correlation was observed between the ability to form a germ tube and the capacity for thigmotropism, and the results gave a level of significance (p<0.05).Further, SEM observation revealed that relatively long hyphae of C. tropicalis with penetrated through the pores of filter membrane. This phenomenon may be of importance in the development of pathogenesis of C. tropicalis as well as C. albicans.

Durability of peel bond of resilient denture liners to acrylic denture base resin

PURPOSE The purpose of this study was to determine the durability of the peel bond of commercial resilient denture liners to a denture base resin using a thermal cycling test. METHODS Eight commercial resilient denture liners (five silicone and three acrylic) were used in the study. The samples were exposed to thermal cycles between 5°C and 55°C for 1 min for 0, 1,250, 2,500, 5,000 and 10,000 cycles. The test samples were placed under tension until failure in a materials testing machine using a crosshead speed of 20 mm/min. The modes of debonding were characterized as tear, peel or snap. Statistical analysis was performed using one-way and two-way analysis of variance and Student-Newman-Keuls multiple comparison tests (α=.05). RESULTS A significant difference was found between different resilient denture liners for peel bond strength at 0 cycles. No extreme influence on the peel bond strength was observed under any of the thermal cycles. The snap mode of debonding was observed in most samples of all materials for all cycles. CONCLUSION All resilient denture liners tested had a sufficiently strong bond to the denture base resin. Within the limitations of this study, the results show that all of the materials were acceptable for clinical use, having met the accepted adequate bond strength for resilient denture liners of 0.45 MPa.