Carious affected dentine: its behaviour in adhesive bonding

Background: Carious-affected dentin (CAD) represents a very common substrate in adhesive dentistry. Despite its ability to interact with adhesive systems, the intrinsic character of CAD leads to lower bonding compared with sound dentin, regardless of the adhesive systems used. This low bonding may be more susceptible to leakage and hydrolysis of the interface by matrix metalloproteinases (MMPs).
Purpose: to conduct a systematic review concerning CAD, selecting articles in term of CAD bonding, as well as the effect of MMP inhibitors against instability of hybrid layer.
Methods: MEDLINE/Pubmed, Scopus and The Cochrane Library databases were electronically searched for articles published from 01/01/1960 to 31/08/2014. Two reviewers independently screened and included papers according to the predefined selection criteria.
Results: The electronic searches identified 320 studies. After title, abstract and full-text examinations, 139 articles met the inclusion criteria. Data highlighted that a poor resin saturation of the already demineralized collagen matrix in CAD is strictly related to nanoleakage in interdiffusion and is the basis of the progressive decrease in strength with hydrolysis by MMPs. The use of mild self-etching systems seem to be the more accredited method to establish bonding in CAD. Inhibitors of MMPs may ensure better performance of CAD bonding, allowing undisturbed remineralisation of the affected matrix.
Conclusions: CAD bonding needs further understanding and improvement particularly to enhance the strength and durability of the hybrid layer.