| Bonding techniques today are widely used in every branches of dentistry, from tooth restoration to veneer adhesion. It has not only facilitated the clinical procedures, but also produced more conservative restorative techniques and met in some extent the growing cosmetic needs of patients. All these should owe to the constant introduction of new adhesion strategies and evolution of adhesive systems. In 1979, Fusayama proposed the "total-etch" concept. Bonding systems developed from this concept greatly increased dentin bond strength. However, their unpredictable postoperative tooth sensitivity puzzled the clinicians. Although desensitizing might relieve patients of the discomfort, it undoubtedly further complicated the clinical procedures. In such circumstances, Chigira et al proposed the "self-etching" concept in 1989. In the beginning, the theory was applied to dentin only. Soon, it was used to both dentin and enamel simultaneously. The concept now is based on the use of nonrinsing acidic polymerizable monomers, which is capable of conditioning and priming enamel and dentin simultaneously to form a continuum in the substrate. Without the need of rinsing, the smear plug is then incorporated in the resin tag. Several years later, different brands of self-etching products were gradually released in the dental market. In view of the convenient application, time saving, reduction ofpostoperative sensitivity and some other advantages, self-etching bonding systems have become a new type of adhesives, more promising than the conventional total-etch systems, and gained growing attentions from researchers and clinicians all over the world. But up to now, they are not so widely used in clinics due to the limited knowledge of their bonding characteristics.With more intensive studies on self-etching systems, researchers are facing with some new problems. For example, as self-etching primers are weaker than etchants, whether they have the capability of etching enamel effectively and get an ideal bond strength as those of total-etch adhesives; if prolongation of conditioning time when uses self-etching primers, especially on enamel, will affect the bond strength, etc. These problems may get different answers when using different self-etching bonding systems. What's more, as there is not a standard test procedure for the measurement of bond strength which can reflect the actual bonding effects subjectively and accurately, it led to ambiguities in the interpretations of the experimental data. Therefore, researchers haven't reached agreement on these problems. In China, there is few researches on self-etching adhesives, even few in clinical applications.In this study, we aimed at examining the bonding characteristics of two self-etching bonding systems in comparison with one acid-etching system using self-improved tensile test and scanning electron microscopy. We compared the differences among the three bonding systems firstly the micromorphologies of tooth enamel and dentin after conditioning; secondly, the tensile bond strengths to enamel and dentin; and finally investigate the effects of prolonged conditioning time and different bonding areas on bond strength.The main findings of this study were as follows:1. 34% Tooth Conditioner Gel (phosphoric acid etchant) produced the strongest demineralization on enamel and dentin, and Clearfil SE Bond primer (self-etching primer) the mildest. It suggested that clinicians may chooseappropriate bonding system for a particular patient according to the variation in solubility of the smear layer and aggressiveness among the three conditioners.2. The mean tensile bond strengths obtained for the 2 mm diameter group were generally higher than those in the 3 mm diameter group, but only specimens bonded with Clearfil SE Bond showed statistical differences. It recommended to use a smaller bonding area to acquire tensile bond strengths closer to their true values.3. There was no significant differences among the tensile bond strengths of bovine enamel and... |
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