EDTA: effect on root dentin ph after exchange of calcium hydroxide paste / Efeitos do EDTA no pH da dentina radicular após trocas de pastas de hidróxido de cálcio

ABSTRACT

The aim of this research was to analyze in vitro the influence of EDTA on root dentin pH during exchange of calcium hydroxide paste. Thirty maxillary central human incisors were selected, and after opening the pulp chamber, root canals were prepared using a stepback preparation technique associated with Gates-Glidden burs. Sodium hypochlorite 1 per cent was used as the irrigating solution, and the root canals were then dried and filled with ETDA for 3 min. Root canals were then again irrigated with sodium hypochlorite, dried and completely filled with calcium hydroxide paste, using saline as the vehicle. Each tooth had its crown adapted in carnauba wax mounted in the middle of the base of a plantform that was filled with saline solution up to 1 mm from the root tip, and purges were performed with nitrogen in the remaining space. Analysis of the diffusion of hydroxyl ions was carried out by a colorimetric method, using a universal indicating solution. This analysis was done at 7, 15, 30, 45, 60 and 90 days; after each analysis the calcium hydroxide paste was exchanged in the root canals and EDTA was applied for 3 min. The results showed a pH change of 6-7 to 7-8 after 30 days, remaining at this level at 90 days in the apical and middle thirds; and at the cervical thirds there was a pH change of 6-7 to 7-8 after 30 days, and a change of pH to 8-9 at 60 days remaining at this level at 90 days. The Kruskal Wallis test showed no significant difference between the third and the time (a=0.05)