The influence of preparation technique and sodium hypochlorite on removal of pulp and predentine from root canals of posterior teeth

Aim To test the null hypothesis that removal of pulp tissue and predentine from root canals of multirooted teeth is not significantly different when p erformed by one of two mechanical preparation techniques in conjunction wit h either water or 3% sodium hypochlorite (NaOCl) irrigation. Methodology Forty-six freshly extracted premolar or molar teeth, with pulps vital at the time of extraction, were assigned to four groups balanced by anatomy (group 1, step-back filing/NaOCl; group 2, step-back filing/water; group 3, automated rotary/NaOCl: group 4, automated rotary/water). Preparat ion was undertaken by a single operator and the volumes of irrigant recorde d for each tooth. One root from each tooth was prepared for transverse hist ological assessment at eight levels, including one at and two apical to the working length. A validated index was used to measure the presence and loc ation of residual pulp tissue and predentine. Results No statistically significant differences were found in the frequenc y with which residual pulp tissue or predentine were observed amongst the g roups, Coronal parts were more frequently devoid of pulp tissue and predent ine than the apical. Canals were frequently occluded with residual pulp tis sue apical to the working length. There was a trend for better pulp and pre dentine removal in accessible parts of the canal as a function of rotary pr eparation and NaOCl irrigation. The isthmus had residual pulp tissue less f requently in the NaOCl groups. Accessory anatomy was unaffected regardless of technique or irrigant. Conclusions Pulp tissue and predentine removal were not significantly diffe rent between a step-back filing and an automated rotary preparation techniq ue in conjunction with water or NaOCl.