Comparative effects of local anesthetic preparations on gingival fibroblasts of the rat.

Cultures of rat gingival fibroblasts were exposed to various dilutions of lidocaine hydrochloride (Xylocaine), mepivacaine hydrochloride (Carbocaine), and prilocaine hydrochloride (Citanest). All three anesthetics produced cell-rounding and detachment from the substrate, which varied depending on the anesthetic, its concentration in the medium, and the duration of exposure (p less than 0.001). Effects were not pH-dependent in the range of 7.0-7.4 and were not modified by epinephrine in the concentration normally present in commercially prepared anesthetic solutions. Prilocaine produced morphological changes at a greater rate and at a lower concentration than did lidocaine or mepivacaine (p less than 0.001). The effects elicited by prilocaine were irreversible, since prolonged exposures to it resulted in various toxic effects: (1) detachment of the cells from the substrate, and (2) development of pyknotic nuclei and circumferential halos in cells that remained attached. The study strongly suggested that prilocaine has the potential to be more toxic to fibroblasts than either mepivacaine or lidocaine, a situation of potential clinical importance.