Inferior alveolar nerve block (IANB) using 2% lignocaine hydrochloride (HCl) with adrenaline in 1:100,000 (LA) concentration is considered to be one of the standard anaesthetic techniques for achieving pulpal anaesthesia for management of symptomatic irreversible pulpitis (SIP) in mandibular molars. However,  pulpal inflammation notably decreases the anaesthetic efficacy by eight-fold in SIP cases. It has been reported in literature that the anaesthetic failure rate in SIP patients vary between 15-57% in mandibular molars .  The reasons for such failures could be multi-factorial such as, decreased tissue pH, altered resting potentials, associated reduced thresholds in inflamed tissues, presence of tetrodotoxin-resistant (TTXr) sodium channels, lowered activation threshold of voltage gated sodium channels, activation of nociceptors, increase in pro-inflammatory cytokines in caries exposed pulps, in addition to the patient and operator related factors .

To overcome the difficulties and to improve the success of pulpal anaesthesia in SIP patients, various adjuvant methods are recommended which include, premedication with nonsteroidal anti-inflammatory drugs (NSAIDs), replacing lignocaine with articaine/bupivacaine/mepivacaine anesthetics and supplemental anaesthetic techniques such as, intraligamentary, intra-osseous and/ intra-pulpal anaesthesia. However, each supplementary technique/methods possess their own drawbacks. For instance, NSAIDs can increase the range of gastrointestinal problems and renal complications whereas replacement of lignocaine with other anesthetics like bupivacaine, mepivacaine or articaine results in anxiety, cardiotoxicity, blurred vision and gingival complications respectively. Intraligamentary method results in periodontal tissue damage and bacteremia whereas intra-osseous administration causes post injection discomfort and is a quite technique sensitive procedure. Further, intra-pulpal injections usually cause high patient discomfort.   

Cryotherapy is a long-standing therapeutic technique that has frequently been applied in medicine for pain management and postoperative care. More recently, it has been reported that intraoral cryotherapy application on the vestibular surface of the treated mandibular molar for 5 mins after IANB application enhanced the anaesthetic success rate in SIP patients. The basic physiological tissue effects of cryotherapy include vascular and neurologic changes. If tissue is exposed to reduced temperatures, an initial reflex vasoconstriction occurs and is followed by cold-induced vasodilatation. This process occurs as a neural reflex triggered by the adrenergic elements of the blood vessels and decreases vascular permeability, thereby reducing tissue inflammation.  Regarding the neurologic effect, cryotherapy induces analgesia by impeding the transmission of both A and C fibers. In addition, cold application might decrease the activation threshold of tissue nociceptors resulting in a local anaesthetic effect that is defined as cold induced neuropraxia.

Further, it was also reported that administration of precooled LA at 4-6 Â°C resulted in faster onset and improved anesthetic efficacy in both maxillary and mandibular molars in patients diagnosed with SIP. Cooling of LA increases the pKa value of lignocaine and this would further increase the cation to base ratio enhancing the anaesthetic potency, as cation form is the principal active local anaesthetic molecule.