# Resin-Based Cement Applied to Enamel and Dentin Pre-Treated with Phytic Acid: An In Vitro Study
## 4 Discussion  
The effect of manufacturer-provided etchants (PA or CAF) and IP6 etchant on the immediate bond strength of the resin-based cement to enamel and dentin were addressed in the current study. The results showed that the manufacturer-provided etchant (PA) had no significant difference compared to 1% and 5% IP6, but superior performance than 10% IP6 when bonded to enamel. Thus, the first null hypothesis that the different concentrations of IP6 would not affect the bond strength of the resin-based cement to enamel compared to manufacturer-provided etchants (PA) must be partially rejected. On the other hand, the manufacturer-provided dentin etchant (CAF) showed lower bonding performance than 1% IP6 to dentin; the second null hypothesis must be rejected. The peculiar structure and the high-density negative charges of IP6 confer a great chelation and unique antioxidant abilities, making it suitable for several applications in dentistry. Despite the compelling data on the merits of IP6 use in dentistry, only very few studies have tested its effect on the bonding of dental adhesive systems to enamel and dentin [24]. We chose to use IP6 in a concentration of 1% on dentin and not higher, based on our pilot study results, where the higher concentrations resulted in an aggressive etching pattern on dentin which negatively affected adhesion (data are not shown). In this study, IP6 has been proven to be an effective agent for removing the smear layer  
Figure 4: SEM images of enamel smear layer removal: (**a**) control group (PA); (**b**) 1% IP6 group; (**c**) 5% IP6 group; (**d**) 10% IP6 group; and SEM images of dentin smear layer removal; (**e**) control group (CAF); (**f**) 1% IP6 group. from enamel and dentin; this effect is mainly attributed to its acidity and ability to chelate with calcium. The higher bond strength to dentin obtained with the use of IP6 might be explained by several mechanisms. Firstly, we hypothesize that the IP6 is able to form insoluble complexes with calcium at pH higher than 4 [25]. Despite the low acidity of IP6, these complexes are expected to occur upon conditioning with IP6 due to the high buffering capacity of dentin [26]. The insoluble IP6-calcium complexes might provide structural stability to the exposed dental collagen network thus enhancing monomer infiltration and bonding to dentin. The stability of collagen is also enhanced by a binary or ternary interaction of IP6 with collagen as described hereafter. IP6 is reported to have a crosslinking effect on collagen, through an electrostatic interaction that results in a binary association between the negatively charged IP6 and the dental collagen network that might attain a positive net charge upon exposure to acids [27; 28]. A ternary interaction might also occur between IP6 and collagen where a cation such as calcium bridges IP6 to collagen. This type of interaction occurs at a pH above the isoelectric point of collagen. A less understood mechanism of IP6-induced stabilization of collagen is called the kosmotropic effect where IP6 acts as a Hofmeister anion through its six anionic groups by interacting with water in the surrounding medium [27]. It has been recently demonstrated that the treatment of dentin with IP6 resulted in less total dental collagen degradation compared to phosphoric acid [29]. In the present study, the decreased percentage of adhesive failures to dentin in the IP6-treated group might be a reflection of the enhanced stability of the exposed collagen network by the action of IP6. Despite the developments in the strategies of bonding to enamel, acid-etching of enamel is still the gold standard procedure for effective enamel bonding through the demineralization of the surface forming a microporous layer with a high surface energy in which the resin infiltrates, forming resin tags [30]. However, the length of these tags has minimal impact on the bond strength values [31].