LAUSR

The aim of the study was to assess the effect of different experimental conditions on registration of microcracks by means of micro-computed tomography. Twenty roots of permanent lower incisors were instrumented with SAF system, filled with a single-cone technique and retreated with the Pro Taper Universal Retreatment system. Each sample was measured in dry, water, and moist conditions. The dry scanning was done after drying of the roots for a period of 4 h in ambient conditions followed by a second observation in wet environment after 48 h of rehydrating in distilled water. A time scan was performed to measure the dentin shrinkage while drying the samples in the tomograph's device compartment. All roots underwent complex inhomogeneous shrinkage and deformation due to the internal stress upon dehydration. This deformation opened the existing cracks to an extent above the current resolution of today's laboratory computed tomography scanners. Contrary, rehydration of the dentin reversed the deformation thus closing some of the cracks below the computed tomography resolution making them undetectable. The first dehydration of dentin may be a source of cracks initiation itself.