The critical barrier to progress in dentine bonding with the etch-and-rinse technique

Abstract

Objectives The lack of durability in resin–dentine bonds led to the use of chlorhexidine as MMP-inhibitor to prevent the degradation of hybrid layers. Biomimetic remineralisation is a concept-proven approach in preventing the degradation of resin–dentine bonds. The purpose of this study is to examine the integrity of aged resin–dentine interfaces created with a nanofiller-containing etch-and-rinse adhesive after the application of these two approaches. Methods The more established MMP-inhibition approach was examined using a parallel in vivo and in vitro ageing design to facilitate comparison with the biomimetic remineralisation approach using an in vitro ageing design. Specimens bonded without chlorhexidine exhibited extensive degradation of the hybrid layer after 12 months of in vivo ageing. Results Dissolution of nanofillers could be seen within a water-rich zone within the adhesive layer. Although specimens bonded with chlorhexidine exhibited intact hybrid layers, water-rich regions remained in those hybrid layers and degradation of nanofillers occurred within the adhesive layer. Specimens subjected to in vitro biomimetic remineralisation followed by in vitro ageing demonstrated intrafibrillar collagen remineralisation within hybrid layers and deposition of mineral nanocrystals in nanovoids within the adhesive. Conclusions The impact was realized by understanding the lack of an inherent mechanism to remove water from resin–dentine interfaces as the critical barrier to progress in bonding with the etch-and-rinse technique. The experimental biomimetic remineralisation strategy offers a creative solution for incorporating a progressive hydration mechanism to achieve this goal, which warrants its translation into a clinically applicable technique.

Clinical application of adhesive systems - a critical review: biomimetic approach

“…The current literature points to two factors that contribute to this situation: the degradation promoted by the water on the bonding agent (silane) and the action of host enzymes present in the collagen fibers, which are released by the action of the acid used in the procedure 10,40 . Studies have concentrated on the correction of these factors by means of the total removal of water during the adhesive procedure and the use of chemical substances to promote the inactivation of the host enzymes 1 . Encouraging results have been obtained by using alcoholic substances (ethanol) to rinse the cavity prior to the impregnation of the substrate with the adhesive system, in an attempt to reduce the water in the interstice of the exposed fibrils [10][11] and chlorhexidine- based compounds.…”

“…The latter has permitted good results in the act of inactivating enzymes released by the collagen fibers in response to acid etching 10 , being a viable clinical procedure, already being used in practice, as a promoter of greater longevity for the adhesive interface with the dentin 4, [10][11] . An in vivo analysis over a period of 12 months has shown the effectiveness of using chlorhexidine after the acid-etch phase 1 . In longitudinal in vitro analyses 4,10 ,40, 42 and rare works on in vivo evaluations 45 the three-step adhesives have proved themselves to be superior to the others in terms of performance 10,45 .…”

“…Biomimetic philosophy aims to imitate nature in the conception of prosthetic rehabilitation solutions 1 . Aspects such as preservation, integration, function and aesthetics must be implicit in current restoration techniques.…”

“…Also in 2011, Brackett et al 1 , after presenting in the introduction to the paper a review of the line of research in adhesive procedures, discussed an experiment to evaluate the effectiveness of chlorhexidine in vivo as a metalloproteinase inhibitor and which, consequently, would retain adhesive potential over time. They also presented the concept of biomimetic remineralization as a fresh alternative.…”

Influência da marca do condicionador ácido na resistência de união da resina composta à dentina

“…Essas alterações possibilitam a penetração do adesivo nas porosidades do esmalte, formando a zona de interdifusão, responsável pela união 1,2,5 . Diversamente, na dentina, o condicionamento remove a smear layer (formada durante o preparo cavitário), alarga a entrada dos túbulos dentinários e desmineraliza as dentinas peri e intertubular, expondo a rede de fibrilas colágenas 6,7 . A penetração do adesivo por entre as fibrilas colágenas forma a camada híbrida responsável pela união do adesivo ao tecido dentinário 2,6,8,9 .…”