Effects of Dentine Pretreatment Solutions Containing Flavonoids on the Resin Polymer-Dentine Interface Created Using a Modern Universal Adhesive

Abstract

The aim of the present study was to evaluate the influence of several experimental pretreatment crosslinker solutions on the resin polymer–dentine interface created using a representative universal adhesive system, by means of microtensile bond strength testing (μTBS), nanomechanical properties and ultramorphology confocal laser scanning microscopy (CLSM). Five experimental solutions containing different flavonoids were applied as dentine pretreatment after acid etching. A control pretreatment group containing no flavonoid was also employed. A representative modern universal adhesive was then applied, followed by a 3 mm thick composite built up. Specimens were sectioned into sticks and submitted to a μTBS test or nanoindentation analysis along the interface (24 h or 25,000 thermocycles). The ultramorphology of the polymer–resin interface was also evaluated using CLSM. The results were analyzed using two-way ANOVA and Bonferroni’s post hoc test (α = 0.05). All flavonoids improved short- and long-term μTBS values (p < 0.01), while only some specific such solutions improved the nanomechanical properties (p < 0.05) and preserved the structural morphology of the interface after aging. Pretreatment of acid-etched dentine using specific flavonoid-containing solutions may be a promising approach to improve both the nanomechanical properties and the durability of modern universal adhesive systems.

Antibacterial and Bonding Properties of Universal Adhesive Dental Polymers Doped with Pyrogallol

“…Therefore, the second null hypothesis must be rejected. The same observations were reported by previous studies when quercetin was used in resin adhesive systems [ 40 , 48 ]. Moreover, such an outcome may be a consequence of the reaction of some antioxidants that promoted a prolonged late polymerization and thus increasing the resistance of the bonding interface to degradation.…”

“…This antibacterial activity could be related to the acidity of the 10-MDP functional monomer or to the elution of some unpolymerized components present in the adhesive system, which are usually toxic to bacteria [ 37 ]. In the literature, it is possible to see that other polyphenols, such as epigallocatechin-3-gallate (EGCG) and catechin, were added to dental adhesives to promotes better antibacterial activity [ 38 , 39 ] and bonding durability [ 40 ].…”

Traditional Microscopic Techniques Employed in Dental Adhesion Research—Applications and Protocols of Specimen Preparation

“…The aim of precursory CLSM studies conducted over 30 years ago, was to evaluate the extent of the dentin smear layer at the microscopic level, as well as the structural organization of dentin tubules. Several further studies used CLSM to visualize the hybrid layer and restoration-dentin interface [ 4 , 11 , 12 , 14 , 15 ] or to assess the properties of new generation composite materials [ 13 ]. Their main objectives were to establish the optimal protocols of bonding techniques and to improve the quality of adhesive connection.…”

“…These properties enable the observation of the interface area between the adhesive material and dental tissue and reveal how deeply the primer incorporates intertubular dentin and penetrates the dentin tubules [ 4 , 11 , 12 ]. Further dyes, such as fluorescein isothiocyanate (FITC) or acriflavin [ 12 , 14 ], were also implemented in research. FITC has a green color and its excitation and emission peak is set at wavelengths 495 nm and 519 nm.…”

“…However these solutions do not perfectly identify the components of the hybrid layer due to their premature leaching [ 12 ]. Dávila-Sánchez et al [ 14 ] presented the CLSM images of an acid-etched dentin surface which was additionally exposed to the experimental flavonoid solutions ( Figure 2 ). The aim was to assess the influence of applied pretreatment protocol on the interaction between dentin and bonding system.…”