Periodontal tissue-vitality after different etching modalities.

The purpose of the present study was to investigate possible immediate necrotizing effects on periodontal tissues of etching agents operating either at low or neutral pH. Phosphoric and citric acids, both of which operate at low pH, exerted immediate (within 20 s) necrotizing effects on both mucosal flaps and periodontal tissues. The penetration depth increased with time up to 1/4 of the circumference of the root after 3 min. This was in sharp contrast to EDTA which operates at neutral pH. EDTA failed to induce any detectable necrosis during the experimental periods. Whether or not the immediate necrotizing effects of low pH etching agents also impair periodontal healing in the long-term perspective, needs to be evaluated with controlled experimental studies in vivo as well as clinically in order to determine whether etching at neutral pH is preferable.