Comparative SEM study regarding the performance of 4th generation of dental adhesives and universal adhesives

Abstract

The aim of this study is to compare, in terms of adhesion strength, marginal adaptation, and thickness of the adhesive layer, the 8th generation of adhesive systems with those of the 4th generation which are considered the "golden standard". Materials and method. The study was performed on a batch of 40 teeth extracted for periodontal/orthodontic reason. They were divided into 4 groups of 10 teeth each. Class I preparation which interested both enamel and dentin were performed on each tooth. The preparations were restored using adhesive systems and restoration materials as follows: group 1: Clearfil Universal Bond Quick, Kuraray Noritake Dental Inc. adhesive system + composite resin Gradia direct posterior, GC; group 2: Clearfil Universal Bond Quick, Kuraray Noritake Dental Inc adhesive system+ ormocer Admira Fusion, VOCO; group 3: All Bond 3, Bisco adhesive + composite resin Gradia direct posterior, GC; group 4: All Bond 3, Bisco + ormocer Admira Fusion, VOCO. After performing the restorations according to the working protocol and in compliance with the manufacturer's instructions, the teeth were sectioned in the facio-lingual direction using a diamond disc and water cooling. The resulting sections include the restoration area, as well as the enamel and the dentin in the vicinity. The sections were analyzed using Quanta Inspect scanning electron microscope. Following the SEM analysis of the sections, the thickness of the adhesive layer, the adhesion to the dental tissues (enamel and dentin), as well as the adhesion to the restoration materials were highlighted. Results and discussions. In 1 and 2 working groups, in which the Clearfil Universal Bond Quick, Kuraray Noritake Dental Inc. was used, the adhesive layer is approximately 10 nm, with a thickness Also irregularities at the interface with the dental tissue and the presence of air voids can be observed. With Clearfil Universal Bond Quick adhesive layer, hybridization is weak compared to that obtained with the 4th generation adhesive layer. In 3 and 4 working groups, All Bond 3, Bisco adhesive system was used (4th generation adhesive system, Etchand-Rinse 3-step (ER 3-step), with separate acid etching step). The thickness of the adhesive layer is about 40 nm, without air voids, the area is compact, relatively constant even in difficult areas of the cavity. With the 4th generation adhesive system, the hybridization is clearly superior, and the interface between the dental tissue and the adhesive is slightly creased, which increases the contact surface. The increased contact surface and the lack of air voids ensure the ER 3-step adhesive system a much better marginal adaptation compared to the universal adhesive. Conclusions. Clearfil Universal Bond Quick, universal adhesive system shows a weaker adhesion compared to All Bond 3 adhesive system due to the difference of adhesion at the adhesive- dental tissue interface, where the acid etching and bonding of All Bond 3 system ensure stronger bonds that varies between 5 and 15 nm.

Keywords

• universal adhesive system
• 4th generation adhesive
• bonding
• adhesion strength