A comparison of two techniques for the removal of calcium hydroxide from root canals

To compare the ability of two irrigant regimens to remove calcium hydroxide (CH) mixed with different vehicles from root canal walls.

The root canals of 92 freshly extracted bovine incisor teeth were prepared with a step-back technique and randomly assigned into two experimental groups (n = 40), whilst the remaining teeth (n = 12) served as positive and negative controls. In each experimental group, ten teeth were assigned to each CH preparation: G1 - CH powder; G2 - CH + saline solution; G3 - CH + polyethylene glycol (PEG); G4 - CH + PEG + camphorated paramonochlorophenol (CPMC). The negative control did not receive CH placement, and the positive control received the intracanal dressing, but no subsequent removal. After 7 days, the CH was retrieved using manual or passive ultrasonic irrigation (PUI). The roots were grooved longitudinally and split into halves. Images of each half of the canal were acquired by a digital camera, and the percentage of CH coated surface area in relation to the surface area of each third of the canal was calculated. The results were statistically analysed with anova with post hoc Tukey test with the null hypothesis set as 5%.

Remnants of medicament were found in all experimental groups. The positive control group had complete coverage of the canal walls with CH in contrast to the negative control (P < 0.001). Considering the cervical and middle thirds, the percentage of CH retention in G1 was significantly lower using PUI (26.6% and 32.2%, respectively) than the manual (38.7% and 46.1%, respectively) technique (P < 0.05). No significant differences were observed between G2, G3 and G4 in all thirds and the experimental groups at the apical third (P > 0.05).

Neither syringe injection nor PUI methods were efficient in removing the inter-appointment root canal medicaments. Remnants of medicament were found in all experimental groups regardless of the vehicle used.