Comparative Analysis of the Shear Bond Strength of Flowable Self-Adhering Resin-Composites Adhesive to Dentine with a Conventional Adhesive

Research Article

J Dent & Oral Disord. 2021; 7(2): 1158.

Comparative Analysis of the Shear Bond Strength of Flowable Self-Adhering Resin-Composites Adhesive to Dentine with a Conventional Adhesive

Asiri AA1, Khan R2*, Alzahrani SS3, Haider S4*, Ud-Din Khan S5, Asiri EAM6, Alamri MF7 and Ahmad A8

1Ministry of Health, Jeddah Specialty Dental Center, Saudi Arabia

2Engineer Abdullah Bugshan Research Chair for Dental and Oral Rehabilitation, King Saud University, Saudi Arabia

3Jordan University of Science and Technology, College of Dentistry, Saudi Arabia

4Department of Chemical Engineering, College of Engineering, King Saud University, Saudi Arabia

5Sustainable Energy Technologies (SET) Center, College of Engineering, King Saud University, Saudi Arabia

6King Khalid University, College of Dentistry, Saudi Arabia

7Al-Farabi College of Dentistry and Nursing, Saudi Arabia

8Department of Chemistry, College of Science, King Saud University Riyadh, Saudi Arabia

*Corresponding author: Rawaiz Khan, Engineer Abdullah Bugshan Research Chair for Dental and Oral Rehabilitation, College of Dentistry, King Saud University, Riyadh 11545, Saudi Arabia

Received: March 06, 2021; Accepted: April 06, 2021; Published: April 13, 2021


This study aimed to measure and compare the Shear Bond Strength (SBS) of a self-adhering flowable resin composite to dentin with a conventional flowable composite, and evaluate the various modes of failure. Thirty (n=30) human premolar teeth were randomly allocated to two groups (Group I: Vertise Flow; Group II: Filtek Ultimate) of 15 specimens each, and SBS was measured for specimens from each group by applying shear load using a Universal Testing Machine (UTM). Modes of failure were observed with an optical microscope. An independent samples T test was performed to test the Levene’s assumption of homogeneity of variance across both groups, with the critical value set at 0.05. The results revealed, that the self-adhering flowable composite (Group I: VertiseTM Flow) resulted in lower shear bond strength as compared with the conventional flowable resin composite (Group II: Filtek Ultimate). Moreover, group I predominantly exhibited non-cohesive failure which reflects a poor bonding to dentin. On the other hand, Group II showed mixed failure for most of the samples, which demonstrate strong adhesive bonding. Therefore, it could be concluded that the self-adhering flowable resin composite (Group I) results in lower SBS to dentin as compare with conventional flowable composite.

Keywords: Shear bond strength; Dental adhesives; Flowable resin composites; Self-adhering composites


The development of the restorative materials that show adhesion with tooth structure is an interesting area of research. The lack of adherence of restorative material to the tooth structure may lead to several problems such as secondary caries, marginal leakage (infiltration of fluids, bacteria and ions into the gaps between restoration and cavity walls) [1] and post-operative sensitivity. Adhesion to dentin is more difficult as compared with enamel. This lack of adhesion to dentin is attributed to its organic composition and fluid that is present in the dentinal tubules. Currently, flowable restorative composites (nano-fillers added to low viscosity monomers) are ideal for many reasons such as pitand-fissure sealant, small Class III and V restorations, enamel flaws and incisal edge repairs [2]. Flowable composites generally result in higher shrinkage and lower elastic modulus (due to lesser filler content) than conventional nonflowable composites [3]. The interfacial shrinkage stresses between dental tissue and composites indicate the potential to increase the possibility of marginal leakage. Three-step conventional adhesive systems (etch + primer + bond) may result in high resin to dentin adhesion, however, factors such as excessive etching may influence the performance due to the possibility that the resin monomers may not be able to penetrate into the open dentinal tubules. In addition, there is a possibility of collagen collapse on air drying after etching [4]. A huge number of new adhesive systems has emerged (universal or multi-mode) and different operative techniques for each group of materials have been introduced [5-7]. As a result, it becomes a challenge for the dentists to choose an adhesive system for routine use at the clinic. Therefore, it is essential for the practitioners to be aware of the physical and chemical characteristics of these materials and its association with structures to select and use them correctly.

The bonding between the restorative material and tooth substrate greatly influences the mechanical, biological, and aesthetic properties. It has been always a great challenge to bond resin-based composites to dentin in comparison to enamel bonding [8,9]. The bond strength of resin composites to dentin could be assessed via numerous techniques. However, SBS is considered as a facile, and commonly adopted method for measuring the bond strength of restorative materials [9,10]. So far, very little literature is available on the SBS of self-adhering flowable composites. Therefore, in the current study we have adopted the SBS method to compare the adhesion properties of conventional flowable resin composite with that of self-adhering resin composite.

Generally, the self-etch adhesive bonding methods are being used as an alternative to conventional flowable resin composites, mainly due to the efortful handling of the latter ones [9,11-13]. However, besides the clinical advantages associated with these systems, their etching potential and bonding performance still need to be tested under various clinical circumstances [10,14,15]. Therefore, there has been increased interest in self-adhering flowable composite technology. Recently, Rengo et al. [16], showed that self-adhering flowable resin composite resulted in higher micro-leakage in dentin interfaces as compared with enamel interfaces. Moreover, they observed that etching of dentin using phosphoric acid reduced the sealing performance when a self-adhering flowable resin composite was applied in Class V cavities. Etching is carried out to open dentinal tubules so that the adhesive could penetrate to the dentinal tubules. So by etching the dentinal tubules are opened to enhance penetration of the adhesive. This will not only block the micro-leakage channels but also increase the interlocking and subsequently improve the shear bond strength.

In order to simplify the procedure, the manufacturers have launched adhesive systems, which combines the primer and the adhesive in a one-step. This new class of flowable composites are called “Self-Adhering Resin Composites” (SRCs). They do not require a separate acid conditioning step and moist post-rinse control. They are considered simplified adhesive materials and offer some advantages over conventional etch-and-rinse systems such as reduction of postoperative sensitivity and prevention of procedural errors related to clinical application of conventional bonding agents (such as over-drying and over-wetting) and reduction of chair time [14,17,18]. Another advantage is that infiltration of adhesive resin tends to occur simultaneously with the self-etch process [19]. As the rinsing and drying steps are excluded by the use of SRCs, therefore, the chances of cavity contamination, over-drying and overwetting issues are reduced [14].

These new SRCs have been proposed as an adhesive-free restorative material indicated for the restoration of small class I cavities, class V cavities, and noncarious cervical lesions as well as for lining in class I and II restorations [20]. Despite the ease of clinical use and other advantages of these SRCs, the durability and clinical service are still the matter of great concern for many dental practitioners [21]. Limited studies are available about their physical and mechanical properties [17,22,23].

The aim of this study was to evaluate the SBS of a self-adhering flowable composite and a conventional flowable composite to biodentine and mode of failure of these two components in order to evaluate their adhesion properties and their clinical performance.

Materials and Methods


The materials used in this study are summarized here along with the supplier’s details. The information regarding flowable composites used in this study is given in Table 1.