The local anesthesia of the first lower molar has the highest occurrence of failure in dental anesthesia. In some patients, the tooth is not anesthetized even after successful mandibular and buccal anesthesia.
The solution lies in the anatomical variability of meticulous branches of the mylohyoid nerve. Therefore a successful anesthesia in these patients requires an additional application of approximatelly 0.5 ml of anesthetic solution under the lingual mucous membrane of the oral diaphragm, at the level of the first molar, is necessary.