Reliability of sealer penetration measurement methods and assessment of dentine penetrability after endodontic retreatment: A correlation study between confocal microscopy and micro-computed tomography

Objectives: To evaluate the reliability of sealer penetration measurement methods used with confocal laser scanning microscopy (CLSM) in correlation with the percentage of residual root filling, and to examine the effect of residual root filling on dentine penetrability after endodontic retreatment. Materials & Methods: Root canals of extracted teeth were prepared and obturated using different calcium silicate-based sealers (CSBSs): BioRoot-RCS, MTA-Fillapex, Bio-C, or epoxy resin-based sealer (ERBS) (AH-Plus) and single cone gutta-percha. After 8-week storage, the root filling material was removed, and canals were chemo-mechanically prepared again before obturation using warm vertical compaction and fluorescein labelled ERBS. Control teeth obturated using warm vertical compaction and labelled ERBS were not retreated. Sealer penetration was measured from images obtained by CLSM using 4 methods: maximum and average depth, penetration area, and penetration percentage. Using Spearman’s test, penetration measurements were correlated with the residual filling material obtained from micro-computed tomography. Results: The highest correlation was with the penetration percentage method. Significant differences were found among sealers in the percentage of residual filling material and sealer penetration (pp=0.013) and middle (p=0.016) thirds, respectively. When compared with non-retreated teeth, the penetrability of dentine was not affected by the residual root filling material regardless to the sealer type (p=0.094). Conclusions: Measuring sealer penetration into radicular dentine using the penetration percentage method was found to be the most reliable. Dentine penetrability during retreatment did not seem to be affected by the type of residual root filling material. Clinical Significance: During non-surgical endodontic retreatment, dentine penetrability may not be affected by the residual root filling material after canal preparation regardless to the type of sealer used in the initial treatment.