A microscopic study on the intercanalar isthmuses of the maxillary premolars and associated iatrogenic cracks

Abstract

The purpose of this microscopic investigation, using stereomicroscopy and light transmited microscopy was to evaluate the configuration of the endodontic treated maxillary premolars, making correlations between the presence of the intercanalar isthmuses and also, to identify possible associated fracture lines. We also evaluated the thickness of the tertiary dentinal layer (irritation dentin layer). The study was based on microscopic investigation on thin sections on fragments or separate preparations resulting from 12 premolars that were clinically compromised. The tertiary dentin is deposited in response to irritations and moderate intensity injuries. As the tendency of crack propagation is directed to the areas corresponding to the root canal towards one of the root surfaces (which is the closest) the crackline – almost without exception, is more or less arched, without detecting an eventual crack in a straight line.