Highlighted review: Injectable local anaesthetic agents for preventing pain in participants requiring dental treatment

Geoffrey St George, Alyn Morgan, John Meechan, David R Moles, Ian Needleman, Yuan-Ling Ng, Aviva Petrie
Editorial Group: Cochrane Anaesthesia, Critical and Emergency Care

Plain language summary: Injectable local anaesthetic agents for preventing pain in participants requiring dental treatment

Review question
This review assessed the evidence for providing successful local anaesthesia that prevents pain during a dental procedure. Included studies compared injections of local anaesthetic to help people requiring dental treatment and to prevent painful sensations tested in an experimental way (such as using cold, a sharp probe, or an electric stimulus).

Background
An injection of local anaesthetic prevents a person from feeling pain. It is given in one specific area rather than in the whole body. Although pain during dental treatment can be successfully managed, it is a common fear of patients.

Several different local anaesthetics are available to dentists, as well as a variety of ways to deliver them, to prevent pain. Factors that appear to influence success include increased difficulty in anaesthetizing teeth in the presence of inflammation, variable susceptibility of different teeth to local anaesthesia, different operative procedures performed on the tooth (for example, it appears easier to achieve successful anaesthesia for dental extractions than for root canal treatment), and various techniques and solutions used to give the local anaesthetic.

We investigated whether injection of one local anaesthetic solution was more effective than another for preventing pain during dental treatment or during an experimental study, and whether this effect occurred quickly or lasted a sufficient length of time, if any unwanted effects occurred, and people’s experience of the dental procedures. Local adverse events might include pain during or after injection, or long-lasting anaesthesia. Systemic effects due to the local anaesthetic solution can include allergic reactions and changes in heart rate and blood pressure.

Study characteristics
Two reviewers searched the literature to identify studies that compared different local anaesthetic solutions injected into people undergoing dental treatment or volunteers who had the same outcomes measured in experimental ways. Within every trial, each person was randomly assigned to receive one of the local anaesthetics under study. The search was up-to-date as of 31 January 2018.

We found 123 trials with 19,223 male and female participants. These trials investigated pain experienced during dental treatment including surgery, extraction, periodontal (gum) treatment, tooth preparation, root canal treatment, anaesthesia of nerves within teeth (pulps) tested using an electric pulp tester or cold stimulant, and anaesthesia of soft tissues measured following pricking of gums or self-reported by the participant.

We pooled data from 68 studies (6615 participants). This resulted in eight outcomes when seven different local anaesthetic solutions were tested during dental treatment, two outcomes assessing pain during and after injection of local anaesthetic, and 47 outcomes tested with a pulp tester or by pricking of gums or self-reported by participants.

Key results
The review suggests that of the 14 types of local anaesthetic tested, evidence to support the use of one over another is limited to the outcome of success (absence of pain), from three comparisons of local anaesthetic. Findings show that 4% articaine, 1:100,000 epinephrine was superior to 2% lidocaine, 1:100,000 epinephrine in posterior teeth with inflamed pulps requiring root canal treatment. No difference between these solutions was seen when pain on injection was assessed, and although lidocaine resulted in less post-injection pain, the difference was minimal.

Researchers found that 2% lidocaine, 1:100,000 epinephrine was superior to 3% prilocaine, 0.03 IU felypressin and 4% prilocaine plain for surgical procedures and surgical procedures/periodontal treatment, respectively. Speeds of onset were within clinically acceptable times, and durations were variable, making them suitable for different applications. Both of these latter outcomes were tested in experimental ways that may not reflect clinical findings. Unwanted effects were rare. Patients' experience of the procedures was not assessed owing to lack of data.

Quality of the evidence
From comparisons of local anaesthetics in this review, all appeared effective and safe with little difference between them. Available evidence ranged from moderate to very low in quality. Some studies fell short, in terms of quality, owing to small numbers of participants, unclear reporting of study methods, and reporting of data in a format that was not easy to combine with other data. Further research is required to clarify the effectiveness and safety of one local anaesthetic over another.

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Citation: St George G, Morgan A, Meechan J, Moles DR, Needleman I, Ng YL, Petrie A. Injectable local anaesthetic agents for dental anaesthesia. Cochrane Database of Systematic Reviews 2018, Issue 7. Art. No.: CD006487. DOI: 10.1002/14651858.CD006487.pub2.