Clinical Considerations of Intrapulpal Anesthesia in Pediatric Dentistry.

During endodontic treatment, effective anesthesia of any vital pulp tissue present in the pulp chamber or root canals is important for patient's cooperation and to maintain the comfort level. This is particularly true in cases of pediatric patients, where ineffective analgesia might result in a traumatic experience for the kids leading to increased apprehensiveness, reduced pain threshold, inadequate cooperation, and also creates an embarrassing situation for the dentists. The most commonly used local anesthetic solution in pediatric endodontics is 2% lidocaine hydrochloride with adrenaline (1:100,000) because of its improved efficacy at low concentrations and decreased allergenic characteristics.[1] The intrapulpal injection technique (IPI) is one of the commonly employed supplemental anesthetic technique adjuvant to conventional maxillary infiltration anesthesia or mandibular inferior alveolar block in situations, where patients encounter severe pain or discomfort during pulp extirpation, especially in acutely inflamed molars.[2] Although various supplemental techniques such as intraligamentary or intraosseous techniques are available, it is wise to anticipate that in spite of apparently profound anesthesia, an IPI may be required to obtain total analgesia.[3] In general, the deposition of local anesthetic solution directly into the pulp chamber provides an effective anesthesia for extirpation, instrumentation, and debridement of pulpal tissues. The most significant factor contributing to the success of IPI is that its administration must be done under pressure. Birchfield and Rosenberg suggested that the anesthetic effect of the intrapulpal technique is mainly due to the back-pressure of the solution, independent of the type of solution injected.[4] However, when the exposure site is too large for a snug needle fit, the exposed pulp is flooded with a small amount of local anesthetic solution for a minute, premature to advancing the needle as far apically as possible into the pulp chamber and injecting under pressure.[5] Various suggested methods that aid in pressure build up in such cases include, obliteration of a large pulpal opening with either gutta-percha or a cotton pellet.[5] Nevertheless, the precise mechanism by which pressure can induce anesthesia is incompletely understood. Monheim has suggested that prolonged pressure may lead to degeneration of nerve fibers in many instances leading to profound anesthesia for long endodontic treatment procedures, as in cases of pediatric patients.[6] Following access cavity preparation and deroofing of pulp chamber, IPI is administered followed by effective hemostasis which is usually achieved with a cotton wool pledge soaked with anesthetic solution or hemostatic agents such as Racellet pellets, aluminum chloride, or with sodium hypochlorite (NaOCl). In addition to its use as a hemostatic agent, NaOCl (in concentrations ranging from 0.5% to 5.25%) have been widely employed as the gold standard irrigant for pulp tissue dissolution in endodontics.[7] The pediatric dentists are aware of significant interactions between various endodontic irrigants, i.e., NaOCl and chlorhexidine (CHX), NaOCl and ethylenediaminetetracetic acid (EDTA), CHX and EDTA, but the interaction between the local anesthetic solution and subsequently used irrigants are often overlooked in clinical situations in many instances.[8910] However, a careful review of literature revealed a study conducted by Vidhya et al. who evaluated the chemical interaction between lidocaine hydrochloride (with and without adrenaline) and NaOCl using nuclear magnetic resonance spectroscopy and reported the formation of a toxic precipitate, 2,6-xylidine, which is a known carcinogen.[11] Although all clinicians neglect this significant interaction attributing to the reason that, only a small amount of local anesthetic solution (0.2–0.5 ml) is employed for IPI, acutely inflamed pulp remnants might necessitate frequent such IPI administrations until the hot tooth is completely devoid of vital tissues to ensure the patient's maximum comfort. This is a true unacceptable fact because every dentist strives hard to perform pulp therapy in pediatric patients, for effectively putting the concerned tooth to sleep, thereby avoiding any further interventional and expensive management techniques such as conscious sedation, general anesthesia, and other behavioral management methods. Hence, the subsequent use of NaOCl (as a hemostatic agent or an irrigant) following IPI with lidocaine hydrochloride (with or without adrenaline) should be avoided in clinical cases to prevent such potential interactions. In addition, 0.9% normal saline can be preferably used to lidocaine hydrochloride for intrapulpal anesthesia (as stated by Birchfield and Rosenberg) to avoid unfavorable circumstances.[4] The IPI technique serves as a useful means of overcoming failure in teeth where conventional anesthetic techniques have failed, with an added advantage of causing negligible systemic effects. However, the main drawback with IPI technique as stated by Malamed is that the IPI by itself can be highly painful.[12] This can be attributed to the vascular distension of the tissues, i.e., engorgement of the blood vessels as stated by Harris.[13] Recently, Sooraparaju et al. in a clinical study reported that topical application of 20% benzocaine gel mixed with hyaluronidase, to the exposed pulp before the administration of IPI can reduce the intensity of pain during IPI.[14] Hyaluronidase is an enzyme that acts by hydrolysis of hyaluronic acid, a normal component of connective tissue, thereby enhancing the diffusivity of drugs injected along with it.[15] In addition, shorter needles have also been recommended in an attempt to reduce pain during injection, especially for the young uncooperative patients.[16] Therefore, a short (20 mm) or an extra shot (10 mm) 30-gauge needle can be employed in such cases to render a painless IPI. These clinically significant observations should be considered during the administration of intrapulpal anesthesia with lidocaine HCl, particularly, in cases of endodontic management of young permanent molars for rendering safe, painless, and successful pulpectomy procedures.