Irreversible pulpitis is based on subjective and objective findings that the inflamed vital pulp is unable to heal, as a result of bacterial infiltration [1]. The common symptoms include intense and paroxysmal spontaneous pain exacerbated by certain stimuli such as sweet, hot or cold foods and beverages [2]. However, relying on symptoms alone is not always clinically indicative of an irreversible pulpitis because the tooth may occasionally appear asymptomatic and responds well to thermal testing. In such cases, dental history and thermal testing are the primary tools for assessing pulpal status. Furthermore, irreversible pulpitis is one of the most common reason for emergency consultations in dentistry [2].
The treatment of choice is a pulpectomy, i.e. a complete removal of pulp tissue. In an emergency appointment, however, due to time constraints, this treatment could be difficult to perform. In multirooted teeth, it is commonly accepted that a pulpotomy, within part of the pulp tissue is removed at the level of the dental crown, is performed. The purpose of emergency pulpotomy is to stop the pain of pulpitis, and results in a lower incidence of post-operative pain [3–6]. The standard anaesthetic technique is an inferior alveolar nerve block (IANB) by introducing the needle near the mandibular foramen at the spine of Spix.
Obtaining anaesthesia in patients with endodontic pain of pulpal origin is often difficult to achieve despite supplemental buccal infiltrations in addition to nerve blocks [7]. The failure rate is between 44% and 81% as was described in various clinical studies [8–10]. In addition, mandibular molars are the most difficult to anaesthetize [11]. In mandibular molars, there is an IANB failure rate of 15% up to 58% for non-inflammatory pulpitis [12, 13] and 44 to 81% in irreversible pulpitis [14–17]. IANB is performed blindly and guided only by anatomic landmarks that vary from individual to individual. Furthermore, there is a variation in the physicochemical characteristics such as lowered pH in the inflamed tissue that neutralizes the base form of the anaesthetic in the nerve sheath and membrane. Furthermore, there are altered resting potentials and lowered thresholds of excitability of the nerves in the inflamed tissue that leads to a varied state of innervation [18]. In addition, psychological factors (fear, anxiety) from one individual to another leads to a state of hyperalgesia or no analgesia that adds to the difficulties in achieving successful pulpal anaesthesia.
Anaesthetics called intra-osseous (IO) could be a more effective alternative. IO consists of depositing the anaesthetic solution into the alveolar bone supporting the teeth. In this method, anaesthesia begins immediately after the injection without causing soft tissue numbness. The injection scarcely causes any pain, and it requires relatively fewer amounts of the anaesthetic solution compared to conventional nerve block techniques [19, 20]. Several types of intraosseous anaesthetic system have been commercialised and studied clinically, such as the Wand® (Milestone Scientific, USA), the X-Tip (Dentsply, York, PA) and Stabident™ (Fairfax Dental Inc., Miami, FL) systems.
Several forms exist: intra-septal (IS), intra-diploid (ID) and more recently, intra-osseous computerised anaesthesia (ICA). However, IS administers the anaesthetic solution into the bone septum just after the cortex, a dense and reduced area, that may lead to partial or complete necrosis [21].
Intra-osseous computerised anaesthesia (ICA), such as the Quicksleeper™ system (Dental Hi-Tec, Cholet, France), administers the solution with a computerised control into the diploë (a richly vascularized bone) at a local rate and pressure. Thus, Quicksleeper™ system is a form of ID in which the anaesthetic is delivered in close proximity to the root apices and associated periradicular tissues, leading to a greater reduction in periradicular sensation. The anaesthesia takes effect more rapidly since the solution is deposited close to the apex of the tooth at an axis of 15° to 30°. Thus, this form of delivery increases its effectiveness and reduces the risk of tissue necrosis, with better pain control (42–93% according to studies) [22, 23]. No soft tissue numbness occurs, and relatively fewer amounts of anaesthetic solution are needed. However, due to the fast diffusion of the anaesthetic solution in the diploe, the heart rate accelerates via the added effect of vasoconstrictors. This elevation is transient, and its effect is negligible and does not pose serious cardiovascular risk [12, 22].
There are currently many clinical studies that have evaluated cardiac parameters during IO administration. The heart rate increases in a reversible manner depending on the speed of injection [12]. The Stabident™ system showed a significant increase in heart rate of 8–28 beats/minute (BPM) on average with 2% lidocaine 1:100,000 epinephrine according to 3 authors [24–26]. By comparison, the X-Tip injection elevated the heart rate by 9–10 beats per min [27]. In regards to other parameters such as oxygen saturation and blood pressure, Pereira et al found no differences in either of them when using the X-Tip™ system but noted a significant increase in heart rate with 4% articaine (1:100,000 or 1:200,000 epinephrine) for anaesthetizing irreversible pulpitis lower molars [23]. Therefore, accelerated heart rate could be a potential adverse effect of this injection [27].
Articaine is a common anaesthetic agent and a member of the amide family. The presence of its thiophene group increases its liposolubility, facilitating its diffusion into both nerve sheaths (such as the inferior alveolar nerve) and neural membranes of individual axons comprising a nerve trunk. The lower pKa of articaine would translate into a greater percentage of the drug in the active base form and its plasma protein binding is 95% higher than most other local anaesthetics [25–27].
The use of epinephrine allows an increase in the success of anaesthesia and a decrease in systemic toxicity, with better pain control. Rogers et al. published the first randomized, double-blind, clinical trial of the efficacy of 4% articaine versus 2% lidocaine in an IANB. They found that 4% articaine to be significantly more effective than 2% lidocaine, with success rates of 62% and 37%, respectively [31].
There are even fewer studies on the Quicksleeper™ system and the variations in cardiovascular parameters (heart rate, systolic and diastolic blood pressure) that occur before and after anaesthesia administration. One study concluded that the increase in heart rate parameters caused by IO injection compared with IANB conventional block in impacted mandibular third molars weren’t significantly different [32]. However, there was no controlled concentration of epinephrine and no proper monitoring of the effects of anesthesia.
Objectives
The primary objective of this trial will evaluate the time taken for the cardiovascular parameters to return to their initial values before administration of IO compared to a standard nerve block anaesthesia in a mandibular molar with irreversible pulpitis. Secondary objectives will be the efficacy of Quicksleeper system compared to IANB when to (i) comparing patient pain, (ii) comparing post-operative outcomes, and (iii) investigating factors associated with the time to recovery of cardiovascular parameters between the 2 anaesthetic techniques. The use of blood pressure and cardiovascular measurements can be considered an asset and additional safety in the management of local anaesthesia through the early detection of signs of potential AEs. The main risk associated with local anaesthetics is a hypersensitivity or toxicity reaction, which is considered to be low leading to a very favourable benefit/risk balance.