Ensuring a dry and clean field is essential in the adhesive bonding of dental restorations. Dentists often face challenges when contaminants such as blood, remnants of temporary cement materials, or saliva are present during the application of adhesive materials. To address some of these challenges, the use of hemostatic agents to control bleeding during adhesive bonding is a common practice. However, it is important to note that if these hemostatic agents are not properly cleaned from the dentin surface, they well jeopardize the bond strength to dentin [10, 22, 23]. Therefore, it is crucial to thoroughly clean the hemostatic materials before bonding to dentin to maintain a proper and durable bond between the restoration and dentin. This study aimed to assess the impact of various cleaning methods on the SBS of dental composite to dentin after contamination of dentin with two different hemostatic agents, in comparison to a control group with non-contaminated dentin.

Shear bond strength test is considered reliable and provides a relative screening of bonding effectiveness at various areas and depths within the dentin. By measuring shear bond strength, it becomes possible to assess the quality of the bond and compare it across different regions or depths of the dentin. However, non-uniform stress distribution at the interface may occur during shear testing, resulting in bond strength values lower than the actual ones which may present a limitation of this test [24].

The present study explored the influence of various cleaning methods on SBS when used in conjunction with different hemostatic agents. The findings highlighted that different cleaning methods have varying effects on SBS, particularly when employed with different hemostatic agents. These findings indicate a rejection of the null hypothesis, as both the contamination agents and the cleaning methods led to a significant difference in SBS among the groups (p-value < 0.05).

Cleaning methods used in the present work are either water, 35% phosphoric acid, katana cleaner (mainly, MDP, triethanolamine, polyethylene glycol) or air-abrasion using 27µ aluminum oxide particles. The findings of the study suggest that the cleaning methods employed with Aluminum Chloride were more effective in restoring the initial SBS compared to Ferric Sulfate.

Regardless of the cleaning methods used, it was observed that Viscostat hemostatic agent had a more detrimental effect on SBS compared to Viscostat Clear. This difference in performance can be attributed to the distinct chemical compositions of the two hemostatic agents and their respective mechanisms of action. Viscostat, containing 20% Ferric Sulfate, controls bleeding by forming superficial and deep clots [10]. On the other hand, Viscostat Clear, which contains 25% Aluminum Chloride, reduces capillary fragility and triggers the precipitation of mucosal proteins during blood channel contraction [10, 25]. The differing mechanisms of action in addition to the different nature of materials considering the higher viscosity of ferric sulfate which is often supplied in gel form, may explain the varying influence of these materials on dentin shear bond strength after cleaning.

The influence of both aluminum chloride and ferric sulfate as hemostatic agents on SBS was investigated previously, and the results showed a significant decline in SBS with the use of both agents [10]. In addition, it was observed that ferric sulfate caused a greater deterioration in bond strength, which aligns with the findings of the present study.

On the other hand, regardless of the hemostatic agents, the use of 35% phosphoric acid significantly restored the SBS when compared to other cleaning methods with a non-significant difference between the other cleaning methods. The higher bond strength obtained with phosphoric acid could be attributed to the dual effect of etching dentin surface which results in removal of smear layer and the cleaning of the hemostatic agent from tooth surface. Only with Aluminum Chloride, phosphoric acid restored the SBS to be comparable to or slightly higher than the control group, while this was not achieved when phosphoric acid was used with Ferric Sulfate solution. Etching dentin surface with phosphoric acid removes the smear layer and dissolve the appatite crystals exposing the collagen fibrils and creating a room for the adhesive to flow around the collagen fibrils [26]. The dental adhesive employed in this study was Single Bond Universal, containing MDP phosphate monomer and hydroxyethyl methacrylate (HEMA), and it was applied in a self-etch mode. The topic of acid etching before the application of self-etch adhesives remains a subject of debate in the literature. Some studies indicate that bond strength can be improved when etch and rinse mode is used with self-etch adhesives [27], while others have shown a decline in bond integrity and durability when etch and rinse technique is applied to self-etch adhesives [28]. In addition, some researchers found no difference between the two methods regarding bond integrity [29]. It has been well documented that the acidity encountered during the bonding process increases the host-derived endogenous enzymatic activity in dentin matrices influencing bond durability and lead to degradation of hybrid layers created by these adhesives [30, 31]. Therefore, future long-term studies are needed to investigate the durability of the adhesive bond after dentin contamination with hemostatic agent and cleaning with phosphoric acid.

Single Bond Universal is characterized by the presence of 10-Methacryloyloxydecyl dihydrogen phosphate (MDP), which is a monomer that bonds chemically to the hydroxyapatite of the tooth structure and thus was reported to resist hydrolysis and enhance resin-dentin bond strength [2, 27,28,29]. It can be clear that MDP was added mainly to enhance bond strength when the adhesive is applied using self-etch mode. If acid etching is performed, it completely demineralizes the dentinal surface, leaving no minerals to interact with MDP.

Various outcomes were observed when examining the cleaning effectiveness of Aluminum Chloride and Ferric Sulfate. In the case of Aluminum Chloride, it was found that phosphoric acid exhibited the highest efficacy in restoring SBS, followed by water and Katana cleaner with air abrasion being the least effective in cleaning the dentin surface. However, when it came to Ferric Sulfate, none of the cleaning methods were able to restore the SBS, and the results were significantly lower than the control group. These findings highlight the differing effectiveness of cleaning agents on bond strength restoration, depending on the specific hemostatic agent used. Ferric sulfate is usually provided in a gel form to control the flow of the material on the tooth surface which may explain the difficulty in removing the solution effectively from dentin surface.

The MDP-containing Katana Cleaner was investigated in the present study due to its performance in previous studies as it improved bond strength when used to clean contaminated Zirconia [32, 33]. Karana Cleaner has a high cleaning effect due to the surface active characteristic of MDP Salt. The hydrophobic group of MDP adheres to contamination, while MDP salt reduces the surface tension of contamination and facilitates its removal (Kuraray Noritake Dental Inc., Technical Product Brochure, Okayama, Japan 2020). However, limited studies evaluated the influence of using Katana cleaner with contaminated dentin. The use of Katana cleaner in the present work did not restore the bond strength in both cases of hemostatic agents and the results of using katana cleaner were almost similar to water cleaning. This may be attributed to the pH of katana cleaner “4.5” which is much higher than that of the acid etchant (pH = 0.1) resulting in inability to completely remove all remnants of hemostatic agents. However, it showed much better results with aluminum chloride than ferric sulfate hemostatic agent which may be attributed to the lower viscosity of aluminum chloride which facilitated its partial removal. Further future studies are required to evaluate the efficacy of katana cleaner in improving bond strength to hemostatic-contaminated dentin.

These findings are consistent with previous studies that have demonstrated improved performance in cleaning dentin surface contamination when using phosphoric acid and chlorhexidine, compared to the use of Katana Cleaner [25]. The agreement between our results and prior research further supports the effectiveness of phosphoric acid as reliable cleaning agents for achieving optimal bond performance.

Air abrasion with Viscostat clear (Aluminum chloride) provided the lowest SBS values, and with Viscostat (Ferric sulfate) was similar to other cleaning methods that resulted in low SBS compared to the control. Therefore, air abrasion was not able to properly clean the dentinal surfaces from the hemostatic agents which may be attributed to the parameters of the procedure as the size of aluminum oxide particles, the pressure used or the time of application. However, these results are in contrast to previous studies that demonstrated that air abrasion had enhanced resin-dentin bond strengths [23, 34].

The failure pattern usually reflects the strength of the bond at the interface, the stronger the bond the higher will be the probability of cohesive failure while adhesive failure usually occur with weaker bonds. In the current study, there was no pure cohesive failure, however, adhesive and mixed failures occurred. Within each group, the adhesive failure predominated, while there was no significant difference between groups regarding the mode of failure. However, it can be noticed that the highest number of mixed failures occurred in the viscostat clear group cleaned with acid-etch and the control group where both groups exhibited highest bond strength values.

There are several limitations of this in-vitro study including inability to fully simulate the oral environment such as presence of saliva, dentinal fluid under positive pulpal pressure, temperature and pH changes, dynamic forces as well as variable cavity designs which were not provided by the specimens used in the study. Furthermore, absence of dentin elemental analysis following different cleansing protocols and resin-dentin interface examination are considered limitations of this study.