Styrene-isoprene block copolymer/methyl methacrylate graft copolymer (SIS-MMA), styrene-butadiene block copolymers (SBS), polyethylene, 1,2-polybutadiene, polysulfone, polycaprolactone polyurethane (PU) and ethylene-vinyl acetate copolymer (EVA) were implanted subcutaneously in dogs for 1 year. The same materials were stored in physiological saline solution at 37°C (in vitro) and in air at room temperature (in air) for 1 year for comparative purpose. Biodeterioration or biodegradation of these materials was studied by mechanical property testing, viscometry, x-ray diffractometry, infrared spectroscopy and microscopy. A little deterioration of the mechanical properties of all the implanted samples was noticed as compared with the samples stored in vitro and in air. The infrared spectrum and x-ray diffraction pattern of the implanted sample except SIS-MMA were practically identical with the control. The implanted samples of SIS-MMA and SBS showed a cracked surface under a differential interference microscope. Viscosity measurements suggested a possible main chain scission for SIS-MMA and cross-linking for SBS and showed that the molecular weight of the other materials was almost unchanged. The intactness was rather surprising in regard to the infrared spectrum and viscosity of PU and EVA, because they were supposed to be more biodegradable. Deterioration of the mechanical properties was not always due to the results of biodegradation, as is often believed, but it must be considered that it might also be due to the absorption of some constituents such as lipids, steroids and amino acid from the body fluids and/or leaching of low molecular weight substances from the implanted materials.

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Acrylic resin is widely used as a denture base material, but the upper complete denture fails often during use. Therefore, the denture base made from acrylic resin should be reinforced in some way. Therefore, as a new method of reinforcement on the denture base, the authors devised a method to improve the strength and rigidity by laminating the palatal surface of the denture base with an organic fiber reinforced plastic, the so-called canape construction. In this paper, as the basic experiment, the flexural strength, fatigue strength and the modulus of elasticity in bending of reinforced acrylic resin by the canape construction were investigated. As the results, the flexural and fatigue strength are improved respectively 160% and 130% compared to the denture base acrylic resin. And the modulus of elasticity in bending is improved 80%. Therefore, it is considered that this new combination of materials using the canape construction might be sufficiently applied to the denture base.

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A replica of natural gingival color can be fabricated in a prosthesis. A precise record of gingival color helps to follow-up oral and systemic diseases. A healthy gingival color according to the “Periodontal Workshop Committee I” is ‘pink’ but no indication is given for color variations by age or position. For more precise definition, therefore, gingival color was examined in the maxillary and mandibular anterior regions by visual color matching using standard color chips after Munsell’s system. Gingival color was measured in 60 subjects, in 18 locations around the anterior teeth. 1.The gingival color varies in Hue from 10 RP to 2.5 YR, being mainly between 2.5 R and 5 R; in Value from 4 to 8, maximum between 6 and 7.5; and in Chroma from 1.5 to 7, mainly from 4 to 5. 2.No difference in gingival color is recognized between the male and female, or between left and right sides of the jaw. 3.Gingival color varies with the position of papillary, marginal, and attached gingivae, and the parts corresponding to different teeth have different colors. 4.The gingival color of young persons, differs markedly from that of older people. In all the parts, red Hue is more tinged with purple in the old than in the young; Value is higher in the young; and Chroma is higher in the old.

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