[Objective assessment of mental nerve local anesthesia].

AIM To study the reaction of the mental nerve to selective stimulation of thin nerve fibers by thermal stimuli during conduction anesthesia. MATERIAL AND METHOD The pilot study involved 24 healthy volunteers: 13 subjects were injected with a 4% solution of articaine-containing anesthetic with a vasoconstrictor in a ratio of 1:200 000 (pH 4.8-5.4) and 11 subjects - a 3% solution of mepivacaine-containing local anesthetic without a vasoconstrictor (pH value 5.8-6.4). The registration of evoked potentials was performed twice: before local anesthesia and 5 minutes after anesthesia. With the help of disposable carpal dental injectors, local anesthesia was performed near the mental foramen in order to anesthetize the innervation region of the mental nerve through a conductive type. The evoked potentials (VP) were recorded on a Nicolet instrument (USA) with Bravo evoked potentials software. The study of thermal EPs was performed using a Contact heat evoked potential stimulator (CHEPS) device ('Medoc Ltd, Ramat Yishai', Israel). The base and peak temperature were set at 33 and 54 °C, correspondingly. RESULTS The evoked potentials for thermal stimulation demonstrated a significant decrease in the amplitude of all components and the elongation of the LP of the main negative-positive N2-P2 complex after anesthesia compared with the initial thermal EP. The complete disappearance of thermal responses was observed in 14 (58%) of 24 study participants, minor changes were seen in 3 (12.5%) cases only. The total response disappearance was observed in 10 (77%) of 13 participants after articaine and in 3 (27%) of 11 - after mepivacaine (p<0.05), weak changes were registered in 2 (15%) cases in the articaine group and in 1 (9%) case in the mepivacaine group. CONCLUSION A 4% solution of articaine is somewhat more effective for pain relief of teeth and bone since it often causes deeper anesthesia, and a 3% solution of mepivacaine without a vasoconstrictor is physiologically more suitable for working with soft tissues.