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The protective effect of a newly designed light-cured varnish on the vulnerability to water of two kinds of glass polyalkenoate cement restorations was examined by determining the penetration depth of Ag ion into the set cement on the SEM pictures in comparison with those of the conventional varnish and a light-cured resin bonding agent. The protective effect of the experimental light-cured varnish was perfect, while those of the conventional varnish and the light-cured resin bonding agent were inferior to that.

To simulate a clinical cavity wall with the inner layer of carious dentin preserved, an artificially demineralized layer was made on the axial wall class V cavities of monkeys by a quick decalcifying solution. The cavities were then restored with a chemically adhesive composite resin after etching with a 40% phosphoric acid jelly etchant. Comparison of the Knoop hardness, the calcium concentration, and the scanning electron microscope observation of the dentin at the axial wall revealed that the dentin, demineralized by etching, was completely remineralized after 4 months.

Recently, problems have occurred frequently such as cervical and exposed dentin surface lesions or root caries and subsequent hypersensitivity because of further increase of the elderly population. This study was projected to device a proper and simple treatment and materials for the adhesive composite restoration for such lesions. The 10-20Ca (10% citric acid containing 20% calcium chloride) solution was found to be a comparatively mild tooth surface conditioning agent and to be effective with a single application to both dentin and enamel. In addition, the use of the SA primer (3% N-methacryloyl 5-aminosalicylic acid in 80% ethanol) and the LVR (visible light-cured, 33% microfilled low viscous Bis-GMA resin) dramatically improved the adhesion and adaptability of the composite restoration in the saucer cavity at the cervical area.

Pulpal response to marginal enamel etching or both enamel and dentine etching with 37% phosphoric acid for adhesive composite restorations was studied in the teeth of the Japanese monkey (Macaca fuscata). Dentine etching irritated the pulp and caused moderate to severe initial changes along the odontoblastic layer at 3 days. When no bacteria were present along the cavity walls, the subsequent pulpal reactions at 30 and 90 days decreased with time and large amounts of irritation dentine were formed. These inflammatory reactions were less than those caused by enamel etching only, or zinc oxide/eugenol cement. Significant correlation (P less than 0.01) was found between the intensity of the inflammatory reactions and the degree of bacterial infection. The pulpal irritation caused by acid etching of dentine for composite restorations is transitory only when the fillings have a good marginal seal and wall adaptation.

A newly developed light-cured anterior restorative composite resin "Graft LC" by GC Co. is characterized by having Vita VMK 68 shades and containing glass filler particles treated with graft binders. Several properties of the resin were examined by using the SEM, surface recorder, and color analyzer. The Graft LC resin was classified as semi-hybrid resin. The filler particles of Graft LC resin comprised two kinds of glass filler in which Si, Ba and Al, and Si were detected. Graft LC resin showed a relatively small surface roughness after polishing in spite of the semi-hybrid resin. According to the degradation test in the alkaline solution, the polished surfaces of Graft LC resin became rough and the depth of subsurface damage layer increased with time. However, the filler particles were retained in the subsurface damage layers. An Ar ion etching employed for SEM preparation is useful to observe the subsurface damage layer distinctly under the SEM. No color change was found even after long-term immersion in a distilled water, though the color of Graft LC resin changed greatly due to irradiation.

The basic concept behind the Black system in the restoration of teeth is a mechanical one. It aims at the retention of restorations by perfect contact with, and the grip of, resilient sound dentinal cavity walls. This necessitates the cutting of sound dentin which is sometimes accompanied by pain and pulpal irritation. For the complete removal of infected carious dentin the conventional technique has depended upon the operator's perception of discoloured dentin and its changed hardness. It has been shown that carious dentin consists of two layers. Namely, a superficial layer which is infected, not remineralizable and necrotic, whereas the deeper layer is uninfected, remineralizable and vital. The first step in the tooth substance saving restorative technique is to use a dye to differentiate between the two layers. Pain on caries removal is virtually eliminated by the selective removal of the stained and necrotic superficial layer while assuring complete removal of all infected dentin. The second step is to use chemically adhesive composite resins which have been developed for both anterior and posterior use. They adhere to enamel and sound dentin and also to the deeper layer of carious dentin. Cutting painful tissue so as to provide the retention form of the classical technique is not required, nor is amalgam as a restorative material in operative dentistry.

The addition of a chemically adhesive composite resin to a restoration of the same material may be evaluated by the bond strength. This was determined after no contamination and after momentary (30 seconds), short-term (7 days), and long-term (3 months) contamination under various conditions. The momentary contamination was not removed by spray-washing the glossy surface that set under a matrix. Removing the glossy surface reduced the bond. The momentary contamination was removed by the etchant whereas the longer contamination was removed only by surface reduction. The application of etchant and bonding agents significantly strengthened the bond to the reduced surface. According to the directives drawn from this investigation, the clinical techniques were illustrated for a large restoration, a subgingival proximal restoration, repair of an open proximal contact, and repair of a worn restoration.