Inferior alveolar nerve block in mandibular molars with symptomatic irreversible pulpitis: causes of anesthetic failure and how to increase the anesthetic success rate—a narrative review

Background and Objective: Effective pulpal anesthesia of mandibular molars with symptomatic pulpitis is one of the main clinical challenges related to anesthesiology faced by dentists. The literature shows high rates of failure, even when the inferior alveolar nerve block technique is correctly performed. The aim of this narrative review is to enumerate the possible causes of anesthetic failure and suggest alternatives for obtaining pulpal anesthesia with predictability.

Methods: A bibliographic search was carried out in the PubMed, Scopus, Web of Science, and Google Scholar databases up to May 1, 2026, and was limited to studies published in English and Portuguese. Studies addressing different anesthetic techniques used for anesthesia of mandibular teeth, as well as different anesthetic salts and the use of different preoperative medications, were included. Article selection involved three stages: screening of titles and abstracts, full-text analysis of relevant studies, and extraction of the main conclusions. A qualitative synthesis of the conclusions was performed.

Key Content and Findings: The success rate of the inferior alveolar nerve block may be lower than 30%. The causes are multifactorial and may involve the intensity of the pulpal inflammatory process, accessory innervation, the type and volume of anesthetic used, and tissue pH. An inferior alveolar nerve block alone will rarely result in the complete absence of pain during clinical procedures. The main strategies discussed to increase anesthetic success include the use of preoperative anti-inflammatory medication, adequate technical execution of the inferior alveolar nerve block, increased anesthetic volume, the use of articaine, supplemental intraligamentary and buccal anesthesia, and pulp testing before endodontic access.

Conclusions: Knowledge of the possible causes of anesthetic failure may serve as a basis for developing strategies to increase anesthetic success rates. A multifactorial approach is required to improve pulpal anesthesia in mandibular molars with symptomatic pulpitis. Combining adequate technical execution, pharmacological modulation of inflammation, appropriate anesthetic selection and volume, supplemental anesthesia, and objective confirmation of pulpal anesthesia may increase the predictability of anesthetic success.