A morpho-structural evaluation of root canal dentin

Objectives: The aim of this preliminary study was to perform a morpho-structural evaluation of dentin in the coronal, middle and apical thirds of the root canal. Variability of tubule density and size in different tooth areas may influence adhesion achievement and efficacy in the endodontic space.

Methods: Evaluation was carried out on 10 healthy extracted teeth. Once the canal preparation was completed, using both hand and rotary techniques associated with 5% NaClO and 10% EDTA irrigations, teeth were longitudinally divided. Root canal walls were etched with 37% phosphoric acid for 15”, then washed, and finally underwent SEM observation (2500 X and 23000 X). Morphologic analysis was carried out in the coronal, middle and apical third of the root canal. A tubule quantification in each portion of the root canal was performed calculating the average of tubules observed in three predefined measurement areas (400 µm2). The average density of dentin tubules per mm2 was then obtained. A further measurement was performed to evaluate the average dentin tubule orifice size. The surface area of tubular and intertubular dentin (both in mm2 and in percentage) was measured and statistic analyses were obtained (p<0.05).

Results: The results of this experimental study showed that higher tubule density and size were revealed in the coronal portion of the root canal (4082/mm2 and 3.90µm respectively) than in the middle portion (2830/mm2 and 2.77µm). The apical third showed a low tubule density (3887/mm2) and a reduced tubular size (1.3µm). The percentages of dentin surface occupied by tubules in the coronal, middle and apical portions were 48.77%, 12.33% and 5.22% respectively.

Conclusion: According to these findings the coronal and middle thirds seem to favour a higher rate of resin tag formation, necessary for micro-mechanical retention of root canal adhesive systems.