Buffering local anaesthetics to reduce dental injection pain?

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Local anaesthesia is essential in order to perform the wide range of dental procedures carried out daily in dental practices. While they help to control pain patients often report burning and stinging sensations during injection of anaesthetics. A potential cause of this is the acidic nature of the local anaesthetic solution. It has been suggested that alkalisation of local anaesthesia with buffering agents hey reduce pain and speed anaesthesia onsets period

The aim of this review is to investigate the efficacy of buffering local anaesthetics in reducing infiltration pain and anaesthesia onset time in dentistry.


Searches were conducted in the Medline, Embase, Scopus and SCIELO databases. Clinical trials in patients aged 18 and over using buffered local anaesthetics injected orally were considered. The primary outcome was pain intensity during local anaesthetic solution deposition. Two reviewers selected studies and abstracted data with the risk of bias being assessed using the Cochrane tool. All pain scales were converted two a standard of scale for comparison and all time measures normalised two minutes. Data was combined using a random effects better analysis. A priori subgroup analysis for injection type and local tissue conditions were planned.


  • 14 RCTs were included.
  • 8 studies used a crossover or split mouth design, 6 a parallel design.
  • 12 studies used lidocaine, 1 buvipacaine, 1 articaine.
  • All studies used sodium bicarbonate has the buffer agent prepared immediately before injection.
  • 4 studies had a low risk of bias,7 an unclear risk and 3 a high risk.
  • 9 studies were pooled in the meta-analysis of self- reported pain for buffered versus unbuffered local anaesthetic injection.  Buffered lidocaine did not result in less pain during intraoral injections: mean difference (MD) -6.4 (95% CI -12.81 to 0.01) units in a 0-100 scale.
  • Four studies were pooled in the meta-analysis of onset time for buffered versus unbuffered local anaesthetics.  Decrease in onset time = -0.65mins (95% CI -1.38 to 0.09).
  • Subgroup analysis suggest that alkalinisation resulted in a more rapid onset for IAN blocks [-1.26 mins (95%CI -1.41 to -1.10)] and in inflamed tissues [-1.37 mins (95%CI -2.03 to -0.70)].


The authors concluded: –

On the basis of this review, routine alkalinisation of local anaesthetics is not recommended in dentistry. Adjusting the pH of lidocaine was not effective in reducing the pain of intraoral injections in normal or inflamed tissues. The onset of anaesthesia was not improved using buffered lidocaine in normal tissues. A slight reduction of the onset time was observed in inflamed tissues and when the IAN block technique was used; however, this change may not be clinically relevant considering the time required to prepare the buffered agent. Studies performed using other anaesthetic salts did not show robust and clinically significant results in favour of alkalinisation.


The authors have searched a good range of databases for RCTs to address this question. They found  14 studies in total although only the 12 studies that involved the use of lidocaine contributed to the meta-analysis. All of the included studies were published in English, but it is not clear if the searches were restricted to English only.

Overall the review did not find a significant effect for alkalinisation in reducing pain control or injections. However, while a slight reduction in anaesthesia onset time was observed in inflamed tissues and using the IAN block technique only two studies were included in these analyses. As only 4 of the included studies were at low risk of bias the overall quality of the evidence is low so it is possible that further high quality studies may have an important impact on the findings.


Primary Paper

Aulestia-Viera PV, Braga MM, Borsatti MA. The effect of adjusting the pH of local anaesthetics in dentistry: a systematic review and meta-analysis. Int Endod J. 2018 Jan 29. doi: 10.1111/iej.12899. [Epub ahead of print] Review. PubMed PMID: 29377171.

Other references

Original review protocol in PROSPERO



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