Failure of inferior alveolar nerve block in endodontics.

Analgesia is essential for successful completion of modern dental procedures. Standard inferior alveolar nerve block (IANB) is the primary method used to achieve mandibular analgesia. Difficulty experienced in obtaining satisfactory analgesia after IANB, especially of an acutely inflamed mandibular molar, remains a common clinical problem. Even when a proper technique is employed, clinical studies show that IANB fails in approximately 30% to 45% of cases. The reasons for failure are not fully understood. Anatomical considerations and abnormal physiological responses in the presence of inflammation as explanations for IANB failure are discussed in this paper.