軟質裏装材の変色と劣化について

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  • Color Change and Degradation of Soft Lining Materials

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Description

The success of complete and partial dentures depends on comfort, esthetics, and function. One of the fundamental principles of these prosthesis is the prevention of undue movement of the denture during function; in an effort to reduce movement it is generally recognized that a rigid denture base is desirable. There are, however, cases when the denture-bearing area is of such a nature as to make coverage by a rigid denture intolerable to the patient. Many patients experience pain and difficulty using dentures constructed with hard denture bases. The soft denture-bearing mucosa is confined between the hard denture base and the bone, and during normal function damage can be done to the tissues, resulting in chronic soreness. This problem is even more pronounced for those patients who have diabetes or other debilitating diseases or for geriatric patients. Dental soft lining materials are widely used as aids for the treatment and prevention of localized areas of painful tissue irritation under dentures. These materials provide a cushion for the denture-bearing mucosa, and this provides comfort for patients. Soft denture liners also valuable when treating patients with (1) ridge atrophy or resorption, (2) bony undercut, (3) bruxing tendencies, (4) congenital or acquired oral defects requiring obturation, (5) xerostomia, and (6) dentures opposing natural dentition. A number of different types of materials have been tried for these application, but none has proved fully satisfactory. Commonly observed deficiencies include poor adhesion to the denture base, poor tear resistance, difficult finishing and polishing, excessive hardness, gradual hardening with time, and excessive fluid absorption with resultant distortion and fouling. The desirable properties, and certain clinical requirements, of a resilient denture base materials have been suggested: (1) non-irritant and non-toxic to the oral tissue, odorless and tasteless, (2) dimensionally stable during processing and in use, (3) low water sorption, (4) high abrasion resistance, (5) permanent resilience, (6) color stability, (7) adequate bond strength to the rigid denture base resin, (8) no adverse effects on the denture base such as distortion, loss of strength, crazing, or blanching, (9) ease of processing, finishing and polishing and (10) ease of repair. However, such an excellent material can not be found in clinics. Most soft lining materials can be classified broadly into two types, namely silicone elastomers and plasticized soft acrylics. The properties and selects together with chemical structure of these materials have been well documented. While acrylic materials have excellent adhesion to poly (methyl methacrylate), they have poor elastic properties and harden gradually due to leaching out of plasticizers. Although silicone soft liners have excellent elastic properties, they have great susceptible to deterioration in the oral enviroment. In particular, depending on their detailed chemical composition may support the growth of Candida albicans. The success or failure of a soft denture liner is not only determined by the physical properties but also other properties sucu as bond strength, creep compliance, dynamic modulus and resilience, water sorption, and stain resistance should be considered. It is also apparent from the results of many studies that the dental profession needs to develop specific performance properties for these materials. Additionaly, future studies should be undertaken to evaluate how the physical/mechanical properties of soft denture liners relate to patient comfort and tissue health.

Journal

  • 松本歯学

    松本歯学 23 (2), 85-96, 1997-08-31

    松本歯科大学学会

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