The creep behavior of denture-supporting tissues and soft lining materials.

This study examined the desirable properties of a soft denture liner. The physical behavior of palatal mucosa of young adults was quantified by analyzing creep behavior using Voigt's four-element model. Instantaneous elastic recovery was significantly smaller than instantaneous elastic displacement, and delayed elastic recovery was significantly larger than delayed elastic displacement (P < .05). Viscous recovery was small but detectable. To ascertain whether the characteristics of the mucosa can be replaced with a soft material, a new soft lining material was developed and both behaviors, especially after load release, were compared with each other. It was indicated that by properly controlling the amounts of the crosslinking agent and inorganic filler of the soft material, its properties may be made to approximate those of the mucosa.

Adhesion of a new light-polymerized denture base resin to resin teeth and denture base materials.

Shear adhesive strength tests were conducted to examine the adhesion of a newly developed light-polymerized denture base resin (LPR) to resin teeth and denture base materials. When LPR was bonded to these materials with a new light-activated bonding agent, the adhesive strength improved greatly. Adhesive strengths of LPR to denture base metals were greater than, or similar to, the metal adhesive autopolymerized resin containing 4-META. Compared with the metal adhesive heat-polymerizing resin, the LPR adhesive values were less when bonded to pure titanium but greater for 18-8 stainless steel and the gold-silver-palladium alloy.

Properties of a new light-polymerized relining material.

This study evaluated a newly developed light-polymerized relining material. The material had lower values for bending strength than conventional resins, but laminating the denture base and the relining material increased the plasticity and thus the toughness. The fit of dentures relined with the new material was similar to that of the autopolymerizing resin. A strong adhesion was obtained between the relining material and the denture base when a new light-activated bonding agent was used.

[Development of a light curing denture base resin].

We developed the light cured direct relining material and used it clinically. In this study, a partial change in its components was made to improve both its strength and manipulability with the aim of using it as a denture base material. The physical properties of the new material, bonding to resin teeth, fit, as well as procedure were discussed. As for physical properties, the bending strength of the new material was increased by improving its organic filler, it becoming comparable to that of heat curing resin. The water absorption of the new material was the lowest of compared materials. The bonding strength of this material to resin teeth was increased by treatment with a light cured bonding agent and the fit of the new material to a test model was comparable to that of heat curing resin. Thus, the new material seems to be quite clinically effective as a denture base resin.

Quality assurance program for a drug information center.

The objective of this study was to develop a quality assurance program for the drug information service using outcome measurements. Criteria of timeliness, accuracy, objectivity, completeness, and use of the information in patient care were measured by a questionnaire sent to users of the service. A response rate of 86 percent showed that the criteria were met in 92, 97, 92, 75, and 69 percent of cases, respectively. The autoreputational approach was utilized in altering procedures to attempt to meet the previously set standards. It was concluded that measuring outcome is a useful method for assuring the quality of a drug information service.

A calorimetric study of the interaction of synthetic phospholipid liposomes with lipid-soluble small molecules used as dental materials and devices.

The interaction of 22 lipid-soluble small molecules, widely used in dental materials and devices, with synthetic phospholipid liposomes, was investigated by the application of differential scanning calorimetry (DSC), in order to clarify the mechanism of small molecules in biological systems. Dimyristoyl phosphatidyl choline (DMPC) and dipalmitoyl phosphatidyl choline (DPPC) were used as lipids. The interaction of various monomers with liposomes has been reported by us in this journal. In this experiment, various compounds such as redox-initiator, photo-initiator or photo-sensitizer, inhibitor, root-canal disinfectant, cement-base materials (eugenol and 2-ethoxybenzoic acid) etc., were investigated. From changes in the phase transition temperature (T), enthalpy (delta H kcal mol-1) and H/HHW values of both DMPC and DPPC liposomes induced by these molecules, it was concluded that aromatic tertiary amine, benzoyl peroxide and hydroquinone monomethyl ether had a relatively large effect on liposomes, and that in phenol derivatives, m-cresol and p-chlorophenol had a large effect on liposomes compared to phenol. Eugenol used as dental cement also had a large effect on liposomes due to its high hydrophobicity. Changes in the transition properties of liposomes induced by small molecules (characterized by shift of T to a lower temperature, an increase or decrease in cooperativity (H/HHW), and a decrease in delta H of a endothermic peak) seemed to be related to biological activities.

Effects of photoinitiators for the visible-light resin system on hemolysis of dog erythrocytes and lipid peroxidation of their components.

The visible-light (VL) polymerizing resin system with photoinitiators (photosensitizer and reducing agent) is widely used in modern dentistry. In this system, polymerization is initiated by photochemical reactions between the photosensitizers (aromatic or aliphatic ketones) and reducing agents (tertiary amines) during VL irradiation. In order to simulate the VL resin-induced toxicity in dental pulps, the present investigation was conducted to determine whether hemolysis of dog erythrocytes and lipid peroxidation of their components occur on exposure to a VL resin system containing aromatic (9-fluorenone, benzil) or aliphatic ketones (camphoroquinone) plus tertiary amine [2-(dimethylamino) ethyl methacrylate]. It was demonstrated that the hemolysis and lipid peroxidation with aromatic ketones were markedly higher than with those of aliphatic ketones, even when the latter were used at higher concentrations. It was clear that peroxidation-induced hemolysis occurred and, further, that surface-active complexes between photosensitizers and reducing agents, which are formed by irradiation, promote hemolytic activity due to their hydrophobic interactions. VL resin-induced responses to dental pulps are probably promoted due to the double effects of unpolymerized monomers and of both radicals and surface-active complexes formed during irradiation.

Current status of release of fluoride ions and other bioactive agents from dental materials: prospects for controlled release.

Many kinds of intraoral systems of bioactive agents have been developed. The cariostatic effect of fluoride ions on enamel caries has been demonstrated through numerous clinical studies. In order to maximize the exposure time of fluoride on enamel for improved prevention of dental caries, fluoride compounds were incorporated into various dental materials and other fluoride-releasing devices were made. The application of fluoride-releasing system is accepted as one of effective caries-preventing procedures. The release of other bioactive agents such as antimicrobial agents (antibiotics, chrorhexidines, eugenols, o-ethoxybenzoic acids and nystatins, etc.) and antiinflammatory agents (benzydamine HCl and steroids) from dental materials and devices have also been investigated. In this article, current status of these systems is reviewed and the therapeutic applicabilities are evaluated.