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

Andrés Dávila-Sánchez,Luisa Fernanda Alegria-Acevedo,Cesar Augusto Galvão Arrais,Salvatore Sauro,Luján Méndez-Bauer,Mario Felipe Gutierrez,Jorge Pailover Bermudez,Fagner Kiratzc,Paulo Vitor Farago,Camilo Pulido,Alessandro Dourado Loguercio

doi:10.3390/polym13071145

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.

Highlights

The bonding interface created by “simplified” adhesive systems is still considered the “Achilles heel” of resin-based restorations [1], since it is usually susceptible to severe degradation over time [2,3]
The reasons for such a situation can be attributed to a synergic hydrolytic degradation of the polymer matrix within the hybrid layer (HL) [4] and the enzymatic degradation of poorly infiltrated demineralized dentine collagen fibrils through activated host metalloproteinases (MMPs) [5] and cysteine-cathepsins (CTs) [6]
The specimens in the CON group showed the lowest μTBS values at both intervals (p < 0.001), with no significant difference compared to the NAR group

Summary

Introduction

The bonding interface created by “simplified” adhesive systems is still considered the “Achilles heel” of resin-based restorations [1], since it is usually susceptible to severe degradation over time [2,3] The reasons for such a situation can be attributed to a synergic hydrolytic degradation of the polymer matrix within the hybrid layer (HL) [4] and the enzymatic degradation of poorly infiltrated demineralized dentine collagen fibrils through activated host metalloproteinases (MMPs) [5] and cysteine-cathepsins (CTs) [6]. When oligomeric proanthocyanidins (PROs) were added to experimental HEMA-free adhesives, it was possible to modify the permeability of the dentine substrate (e.g., hydraulic conductance) and preserve the integrity of the HL over time [13]

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Conclusion