Evaluation of the micromorphology of the hybrid layer in caries-affected dentin: a systematic review

Introduction
Conventional restorative procedures demand the inclusion of caries-affected dentin (CAD) in tooth preparation. Developments in adhesive dentistry preclude the removal of the affected layer by achieving bonding to it. This systematic review was undertaken to evaluate the micromorphology that was seen in a hybrid layer formed within CAD.

Objectives
The aim of this review was to evaluate the micromorphology of the hybrid layer in caries-affected dentin

Material and methods
PubMed and Google Scholar databases were searched according to the inclusion and exclusion criteria from September 2010 to August 2020. References from articles were manually searched. Full-text articles available in the English language were chosen. Data extraction and quality assessment of selected articles were independently performed by two authors and a third author was consulted when needed. The risk of bias was assessed using the MINORS checklist. Data were entered in appropriate tables for assessment of obtained results.

Results
Out of the 328 search results, 325 were excluded and 3 studies were selected for inclusion in the present review. This systematic review favored sound dentin (SoD) over CAD. Morphological and chemical characteristics strongly influence the response of CAD in bonding which, regardless of the type of adhesives, demonstrates lower strength and durability than sound dentin.

Conclusions
Based on the studies included in the review, it can be concluded that despite the improvement in adhesion technology over recent decades, CAD bonding needs to be further understood and improved.