Objective: The effect of long-term performance of one-bottle or two-bottle bonding agents on the shear bond strength to lithium disilicate ceramics (LDS) were to investigate, and the long-term performance of the bond strength of two-bottle bonding agent (Tokuyama Universal Bond II) was investigated under conditions without hydrofluoric acid solution (abbreviated as HF)-pretreatment of LDS. Methods: Nine resin cements (both self-adhesive and adhesive types) were used. It was investigated 1) the adhesion strength of various resin cements to LDS from the presence or absence of HF-treatment, 2) to determine the effect of the deterioration in three times [after one-day storage (abbreviated as Base), and after 5,000 & 20,000 thermocycles (abbreviated as TC 5k and TC 20k)] of one- and two-component bonding agents. And the difference in degradation between one- and two-component bonding gents consist of the silane coupling agent was performed by chemical analysis (High Performance Liquid Chromatography). Results: The trends of resin cements were statistically not very different for each cement 3 times with HF-conditions. Also ESTECEM II and Super-Bond Universal showed the significant greatest values in two conditions (TC 5k and TC 20k) without HF-condition. In TC 20k, ESTECEM II & Super-Bond Universal showed significantly better results than others when treated with the recommended bonding agents without HF-condition. In TC 20k, there was not much statistically significant difference if pretreated with Tokuyama Universal Bond II without HF-condition. Significance: When using LDS, it was found that long-term durability could be maintained by pretreating with Tokuyama Universal Bond II without pretreating with various hazardous HFs.

Composite materials are widely used in the dental field in clinics as biomaterials. For example, it has been used as a biomaterial to repair caries and restore masticatory function, and as a cement to adhere the restoration to the tooth substrate. In order to demonstrate its function, dental biomaterials are measured their mechanical strength. From such basic research, we explained the potential of dental biomaterials, especially flexural strength and modulus of elasticity. Mechanical properties of dental biomaterials similar to those of the tooth, thermal stimulation, and aesthetic elements in the oral cavity. In this part, we will introduce the commercialized products of composites suitable for the characteristics and tooth quality, and provide the reader with the characteristics from the flexural characteristics of the composite materials used in clinical dentistry. In clinical performance, it might be advisable to delay polishing when composite biomaterials are used for luting materials, filling materials and core build-up materials since improved the flexural strength and the flexural modulus of elasticity were displayed after 1-day storage. And it is thought that flexural strength or characteristics is a significant important mechanical property of oral biomaterials.