For the majority of dentists, inferior alveolar nerve blocks (IANB) are the only way to achieve anesthesia for mandibular teeth. Periapical infiltrations are blocked by the dense buccal cortical bone, so injection into the pterygomandibular space is the only way to go. Yet, this method isn’t without its headaches. Inferior alveolar nerve blocks are only successful 60-92% of the time. They can also cause parasthesia, transient facial nerve paralysis (if injected into the parotid gland) or trismus, if there is any trauma to muscles or blood vessels during the injection.
On the coronal aspect of the mandible, there is much more perforated bone, compared to the outer compact bone. This is the target for intrapapillary injections (also known as crestal anesthesia) – as the perforations in the bone allow for drug diffusion in the marrow space, and leads to pulpal anesthesia.
Some studies suggest about 100% successful anesthesia with this method. However, intrapapillary injections are most commonly used only as a supplementary technique, when IANB fails. How useful is this technique, in regards to achieve successful anesthesia, patient comfort, and post-op recovery pain?
Effectiveness of intrapapillary injection compared to inferior alveolar nerve block
The effectiveness of the two injection technique is similar. In one study following 30 patients extracting mandibular premolars; there was no significant difference between intrapapillary injections and IANBs in achieving anesthesia. In fact, the rate of successful anesthesia with intrapapillary injection is even higher in molars than premolars. As the broader alveolar crest in the molar regions is accompanied by larger bone perforations, it leads to a higher diffusion of the anesthesia in the marrow space.
Time of onset of anesthesia
The onset of anesthesia with an intrapapillary injection is significantly faster than that of IANBs. It has been shown that the intrapapillary injection can produce anesthesia in about 1 minute, and IANBs produce anesthesia in about 7 minutes.
Pain perceived by the patient during injection and during the procedure
The pain perceived by patients during intrapapillary injection is slightly lower than that of IANBs. In fact, IANBs are the most painful injection method, followed by periapical local infiltration and mental nerve blocks. Furthermore, once anesthesia is achieved, the pain of a procedure is similar between injection methods.
Duration of anesthesia
The duration of anesthesia is much shorter with intrapapillary injections (up to 60 minutes) compared to IANB (up to 130 minutes). When performing relatively simple procedures, intrapapillary injections are much more preferred by patients, simply because the anesthesia wears off faster. However, when performing a more complex procedure, IANBs are needed, as they award more time to the clinician.
Postoperative pain
With intrapapillary injection, postoperative complications can include ulcerated epithelium at the injection site, or sloughing of tissues. In fact, Prostaglandin E2 (PGE2) levels are significantly higher at the site of injection, with intrapapillary injections than other techniques. PGE2 is the most prominent pro-inflammatory and pain mediator involved in the pulp and periodontium. It is due to the increased PGE2 levels that patient post-op perceived pain at the injection site is higher with intrapapillary injections, as compared to IANBs. However, keep in mind that the rate of patient self-induced trauma, transient facial nerve paralysis and trismus are much higher with an IANB.
Intrapapillary injections are a great tool in a dentist’s tool bag. It is a method than can be used alone or in combination with an IANB. In simple, short procedures, this method can be used to achieve localized and predictable anesthesia. However, due to its shorter duration, IANB is preferred during more complex, longer procedures.