In recent prosthodontic procedures in crowns and bridges on endodontically treated teeth, root fractures have become a more critical issue to be discussed since practitioner have often met as many clinical problems associated with the phenomenon as those of dislodgement of post and core. One of the main reasons for this phenomenon may be a mechanical stress concentration on cast post and core which may be caused by a difference of elastic modulus between tooth structure and post core. Hence, as a preventive measure, the use of flexible fiber posts is thought to be effective clinically. Therefore, direct post and core employing stock posts and adhesive resins are now highly recommended to clinicians. However, in Japan, cast metal post and core have been primarily used as laboratory process, and general practitioner may not be used to the direct procedure.
There are technical difficulties to the progress of indirect procedure of resin post and core using a fiber post and working cast such as inefficient light curing and the necessity of separating agent application on a cast. Hence, in this particular clinical report, a unique and effective laboratory process technique is introduced and discussed.

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A newly designed two-bottle/one-step resin bonding system (SI-IB551) containing 6-MHPA as an adhesion promoting monomer was developed by Shofu. The aim of this study was to observe the interfacial ultrastructure of the experimental bonding system by means of the Ar ion beam etching under the FE-SEM. The experimental flowable resin composite (SI-BF-2001-HF) was bonded to the flat enamel/dentin surfaces or dentin cavities after caries removal of the human extracted molars using this system. In a routine technique, the specimens were cut half, embedded in an epoxy resin, polished and then the resin-tooth interface was observed after Ar ion beam etching for 35sec under the FE-SEM. This new experimental bonding system showed the tight interfacial junction to enamel/dentin/cariesaffected dentin, but the decalcified dentin layer produced by the self-etching adhesive was very thin and the hybrid structure was not clearly observed in the superficial dentin layer. We thought that this resin bonding system might be promising for clinical use.

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In 1978, Kuraray introduced “Clearfil Bond System F”, the world's first total etching adhesive system, and then made improvements to the total-etching procedure and launched “Clearfil New Bond” and “Clearfil Photo Bond”. Following the development of “Clearfil Liner Bond System”, a mild etching/primer system, we introduced “Clearfil Liner Bond II”, the first total self-etching bonding system in the world. Moreover, we have developed “Clearfil Liner Bond IIΣ” which has designed for multiple uses, and “Clearfil Mega Bond”, which has designed to improve manipulation. Also, we have made an experimental product called “ABF”, a fail-safe system that contains an antibacterial monomer and fluoride releasing compound.
Furthermore, we have applied its adhesion technology to the development of adhesive resin cements and have developed “Panavia EX”, “Panavia Fluorocement”, and “Panavia F 2.0”, improving cementing function with the introduction of each new product. Also, as a response to the diversification of restoration materials, we have introduced such product as, “Porcelain Bond”, a ceramic surface treating agent, and “Alloy Primer”, a metal surface treating agent.
In this manner, we have been able to develop products with better functions because of advances in key technologies. This article deals with the molecular design involved in our key technologies.

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In 1982, Sun Medical (“SUN”) commercialized a dental adhesion resin “Super-Bond” based on a 4-META/MMA-TBB resin invented by Tokyo Medical and Dental University. Since then SUN has cultivated its adhesion technology by combining the study on the curing kinetics of Super-Bond; the results of a series of researches on dentin adhesion conducted by Prof. Nakabayashi & his team and Dr. Takeyama; and the polymer technologies developed by Mitsui Petrochemicals (currently Mitsui Chemicals), one of the parent companies.
Table 1 shows major dentin adhesion systems that have been developed by SUN.
The 4-META/MMA-TBB resin has been used in broad clinical applications all over the world owing to its strong dentin adhesion and superior marginal sealability, and even today, after more than 2 decades from its introduction, many new academic and clinical studies are being conducted on the use of this system.
Super-Bond D-Liner was developed by modifying the 4-META/MMA-TBB resin to a bonding agent for composite resins and amalgam. Super-Bond D-Liner, the first Japanese bonding agent employing a HEMA-based primer to be used after etching, has been simultaneously introduced to the US market as Amalgambond Plus. In Japan, Super-Bond D-Liner has evolved into Super-Bond D-Liner II and Super-Bond D-Liner Dual. They have been well accepted by clinicians as bonding systems, with which a smear layer can be thoroughly eliminated.
In 2000, the research on the 4-META/MMA-TBB resin brought forth two new products:
AQ Bond, a thin-film light-curing bonding agent, and
ChemiAce II, a dual-curing filled resin cement.
These two products maximize the adhesion properties of Super-Bond without use of the TBB, the curing initiator used in Super-Bond. With respect to AQ Bond a minor modification was made and evolved to AQ Bond Plus in 2003, to respond to the recent remarkable advances in light curing units.
This article deals with the relationship between the 4-META/MMA-TBB system, the SUN's core technology, and the new light-curing bonding agents with thin film thickness, as well as the history of their development.

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GC has a successful history in developing numerous glass ionomer cements with selfadhesive properties, based on original technologies. In recent years, in the field of adhesive resins, GC has examined 4-MET from the viewpoint of adhesion theory as it relates to glass ionomer cements. Research found that 4-MET dissolves in water, which in turn, led to the development of the world's first self-etching primer utilizing 4-MET in an aqueous solution. Based on this technique, GC has developed “UniFil Bond”, “LINKMAX”, and “UniFil Core” in rapid succession, and now has succeeded in developing “G-BOND”, a one-bottle, one-step typed bonding agent. The development of G-BOND was based on the concepts of easy handling through a perfect one-bottle, one-step system, producing the same bond strength as two step systems and excellent storage stability. The result is that the application time of G-BOND is the shortest among commercially available bonding agents, while the micro-tensile bond strength is almost same as that of UniFil Bond. In this article we review GC adhesive technology focusing on adhesive resins.

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Ever since Shofu Dental Mfg. Co., Ltd. Was founded in 1922 (the corporate name was changed to Shofu Inc. in 1983), the company has produced a number of products that have contributed to dental care as one of the oldest Japanese dental material manufacturers. In research and development, based on accumulated a vast amount of technical information and data over the past 81 years by our colleagues, Shofu has actively promoted technical exchanges among different product fields as one of the advantages of comprehensive dental material manufacturer and introduction of new materials and techniques ought to meet needs of times, and engaged in technical innovations aiming technology-centered product development. We will discuss the history of world-renown restorative materials and their technical innovations at Shofu.

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Recent advances in restorative bonding systems have been made, and at present, seventhgeneration products are being developed overseas. The conditions necessary for dentin adhesion include: demineralization by an acid treatment; penetration and diffusion of a monomer into the area created by demineralization; and curing of the monomer while forming a complex with organic materials. In order to achieve dentin adhesion, different manufacturers have developed various products, and in 2001, Dentsply-Sankin introduced Xeno CF II Bond, a two-bottle, one-step all-in-one restoration system. This article deals with this product and a new bonding system.

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Tokuyama Dental has developed various dental bonding agents: Palfique, Tokuyama Dental's first bonding agent was introduced in 1983; Tokuso Mac-Bond II, a self-etching bonding agent was introduced in 1997; and One-Up Bond F, a single-step bonding agent that does not require any pretreatment was introduced in 1999. Also, Tokuyama Dental has developed adhesive resin cements, such as, Bistite II (1998) and Multibond (2001), and ceramics and metal restoration primers such as, Tokuso Ceramic Primer (1993) and Metaltite (1998).
This article deals with Tokuyama Dental's original key technologies and materials that have played central roles in the company's research and development of these adhesives over the last 20 years.

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