Single Tooth Anesthesia
Root canal procedures have the reputation of being painful; without effective pain control, an endodontic treatment cannot be performed in a calm, precise fashion. Achieving clinically acceptable anesthesia in the maxilla is rarely a problem, while anesthesia of mandibular teeth is more difficult to achieve on a consistently reliable basis.
Patients who are experiencing pulpal pain, particularly in mandibular molars, have additional anesthetic problems. The inferior alveolar nerve block does not always provide profound pulpal anesthesia in mandibular molar with pulpitis, and supplemental local anaesthesia is often required. A “bull’s eye approach” is useful in difficult cases: inferior alveolar nerve – buccal / lingual – intraligamental – intraosseous – intrapulpal. Other problems arise with apprehensive patients, who report a history of previous difficulty with anesthesia; because of technical problems or individual factors, sometimes a larger dose of anesthetic is required. A “rule of the thumb” for remembering maximal dosages with currently formulated local anesthetic cartridges (Mepivacaine3%, Mepivacaine2% with ephinephrine 1:100.000, Articaine 4% with ephinephrine 1:100.000) is to use one cartridge of local anesthetic for every 12 kg of patient weight.
Anyway, the inferior alveolar nerve block unfortunately has an high percentage of failures, even when properly administered. Mandibular teeth may receive innervation from more than one nerve trunk, such as long buccal nerve, lingual nerve and mylohyoid nerve; buccal and lingual infiltration adjacent to the tooth of interest may be effective.
The most popular supplementary injection is the intraligamentary injection or periodontal ligament (PDL) injection. It uses the periodontal ligament to administer the local anesthetic solution. The success of supplemental intraligamentary injections in achieving pulpal anesthesia for endodontic procedures has been reported to be 50% to 96%. A short needle is placed in the sulcus and advanced along the root, until resistance is met. Anesthetic is injected with considerable pressure. Sometimes it is painful on delivery, and can cause post-operative discomfort. Using a conventional syringe, the possibility of breakage of the anesthetic cartridge does exist.
Recently, a computer-controlled local dental anaesthetic system has been developed. This technology utilises an electro-mechanical motor regulated by a central processor unit functioning in concert with a force/pressure transducer. The machine continuously monitors the exit pressure of the anaesthetic solution, and automates the injection at a controlled rate, thus reducing pain and post-op discomfort.