Infiltration of local anesthetic in the maxilla (a) and the mandible (b). Unlike in the maxilla, in the mandible the LA infiltration may not penetrate the cortical plate, leading to insufficient anesthesia
Inflammation and LA Failure
Presence of inflammation may have several effects on local tissue physiology, and it was speculated that local anesthetics are generally much less effective when administered to patients with inflamed tissue probably due to the tissue acidosis . The inflammation induces tissue acidosis that may cause “ion trapping” of local anesthetics: the low tissue pH will result in a greater proportion of the local anesthetic being trapped in the charged acid form of the molecule and, therefore, unable to cross cell membranes . In addition, peripheral vasodilation induced by inflammatory mediators would reduce the concentration of local anesthetics by increasing the rate of systemic absorption .
Local inflammation may lead to activation and sensitization of peripheral nociceptors and sprouting of nerve terminals. In addition, local inflammation may also lead to neural central sensitization, accelerated even more when the patient suffers from psychological stress. Thus, the local inflammation may bare both local and central neural effects that may compromise the ability to achieve profound long-lasting LA .
Faura-Solé et al.  reported on a series of cases of broken anesthetic injection needles. The needles were located in the pterygomandibular space or near the maxillary tuberosity. These complications were the result of an unexpected movement by the patient or an incorrect anesthetic technique. For prevention of needle breakage, it is recommended to routinely inspect dental needles before administering injections and minimize the number of repeated injections using the same needle . The needles should not be bended before use. And short needles are inadequate when performing an inferior alveolar nerve block, since a needle must be of adequate length to ensure that it is never buried to the hub .
The management of needle breakage is a clinical dilemma. While there is still controversy as to whether or not to remove a broken dental needle , recognition, localization, and documentation are of paramount importance. The removal is warranted not only because of the fear of needle migration toward large blood vessels in the head and neck but also because of the medicolegal considerations [21, 33–38].
Ethunandan et al.  recommended in the event that needle breakage does occur, every effort should be made to retrieve the needle immediately, if the tip is visible, using fine hemostats. However, if the broken tip is not visible, an immediate referral is advised. The remaining portion of the broken needle should also be sent along for further determinations of the size of the broken fragment . In addition, when breakage occurs, the patient must be informed immediately and the event must be documented thoroughly. The patient will need reassurance and referral to an oral and maxillofacial surgeon for treatment. In addition, marking the needle entry point with a permanent marker will help the oral surgeon establish orientation [34, 37]. Today, new technologies and surgical techniques allow for complete removal of a broken needle preventing possible complications .
Postoperative Soft-Tissue Injury
It is extremely important to warn patients that the effects of anesthesia can persist for several hours which may cause a patient to bite the mucosa of the lower lip, cheek, or tongue or to scratch or rub the chin region resulting in a self-inflicted injury .
The most important steps in managing untoward reactions to LA are to adopt a clinical practice aimed to prevent LA possible complications, diagnose the problem promptly when it does occur, treat it if necessary, and reassure the patient.
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