Irreversible pulpitis: Do larger volumes of local anaesthetic improve success of inferior alveolar nerve blocks?


Performing root canal treatment requires effective local anaesthesia. However, for mandibular teeth with irreversible pulpitis the failure rate for of inferior alveolar nerve blocks (IANBs) has been reported to be between 43-83%. The use of oral premedication, supplementary injections (buccal, lingual infiltrations, intra-osseus or intra-pulpal) or increasing the volume of anaesthetic initially deposited are potential strategies.

The aim of this review was to compare the efficacy of 1.8 and 3.6 mL of the same anaesthetic solution for IANBs when treating mandibular teeth with irreversible pulpitis.


Searches were conducted in the PubMed, Scopus EBSCOhost (Dentistry & Oral Sciences Source) and databases. Randomised controlled trials (RCTs) published in English comparing 1.8 mL of anaesthetic solution with 3.6 mL of the same anaesthetic solution for inferior alveolar nerve blocks (IANBs) in adult patients were considered. Two reviewers independently screened and selected studies extracted data and assessed study quality using the Cochrane risk of bias tool. Disagreements were resolved by a third reviewer. The success rate of IANBs anaesthesia defined as ‘no’ or ‘weak/mild’ pain according to patient-reported pain scores during access cavity preparation and root canal instrumentation was the main outcome. meta-analysis was performed using the random-effects model and certainty of the evidence evaluated using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.


  • 4 RCTs involving a total of 280 teeth randomised.
  • 3 trials used the Heft-Parker visual analogue pain scale, One a verbal analogue scale.
  • 2 trials were conducted in Iran, one each in India and Brazil.
  • 3 trials were considered to be at low risk of bias one at unclear risk.
  • Meta-analysis of:-
    • 4 RCTs showed use of 6 mL of solution significantly increased the anaesthetic success of IANBs compared to 1.8 mL, RR = 1.94 (95%CI; 1.07 to 3.52) I2 = 77%.
    • 3 RCTs using Heft-Parker scale) demonstrated significantly increased anaesthetic success for 3.6 mL of anaesthetic compared with 1.8 mL, RR = 2.55 (95%CI; 1.72 to 3.78) I2 = 0%.
  • The authors graded the quality of evidence as ‘high’.


The authors concluded: –

Based on high-quality evidence, larger volumes of local anaesthetic solutions significantly increase the success rate of IANBs when treating mandibular molars with irreversible pulpitis. However, 100% anaesthetic success was still not achieved. Hence, supplemental techniques are recommended to achieve pulp anaesthesia when failure of IANBs occurs in teeth with irreversible pulpitis.


The authors have searched a number of major databases although restricting the inclusion criteria to English language papers could mean that relevant studies are excluded. A good methodological approach has been taken and 4 relevant RCTs identified. Three of the 4 RCTs were at low risk of bias and overall, the evidence was considered to be of high certainty.  As only a limited number of RCTs are available consideration of different types on anaesthetic  or different anaesthetic techniques was not possible in addition the included studies only relate to mandibular molars. There was no information on adverse effects.


Primary Paper

Nagendrababu V, Abbott PV, Pulikkotil SJ, Veettil SK, Dummer PMH. Comparing the anaesthetic efficacy of 1.8 mL and 3.6 mL of anaesthetic solution for inferior alveolar nerve blocks for teeth with irreversible pulpitis: a systematic review and meta-analysis with trial sequential analysis. Int Endod J. 2021 Mar;54(3):331-342. doi: 10.1111/iej.13428. Epub 2020 Nov 10. PMID: 33040335.

Review protocol on PROSPERO

Other references

Dental Elf – 1st Mar 2019

Irreversible pulpitis: What is the most effective local anaesthetic for inferior alveolar nerve block?







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