Zanchetta Peron F. et al. - Photobiomodulation and Pain Associated with Local Anesthesia in Children: A Systematic Review and Meta-Analysis

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Photobiomodulation administered before the injection of a local anesthetic appears to moderately reduce the pain experienced by children at the time of needle insertion. This systematic review with meta-analysis includes 10 studies, but the authors themselves describe the level of evidence as limited.

What this study measured

Does photobiomodulation reduce pain associated with local anesthetic injections in pediatric dentistry? The target population consists of children receiving local anesthesia at the dental office, a procedure often associated with dental anxiety. The authors searched six databases, including PubMed, Embase, and Cochrane CENTRAL, through January 2025, with no language restrictions. Two independent reviewers conducted the selection and data extraction, and assessed the risk of bias using the ROB-2 tool. Of the 9,852 references identified, 10 studies met the eligibility criteria and were included in the qualitative review. The protocol was registered in PROSPERO under number CRD42024539486.

Key Findings

All of the included studies measured pain at the precise moment of needle insertion using the WBFPRS and FLACC scales. Two separate meta-analyses were conducted based on the chosen comparator.

Compared with a placebo: 3 studies providing 14 comparisons, with a standardized mean difference of -0.44 (95% CI: -0.59 to -0.29), representing a moderate reduction in pain in favor of photobiomodulation.
No heterogeneity was observed in this analysis (I² = 0%), with consistent results across all scales.
When compared with a topical anesthetic gel: 2 split-mouth studies, with a mean difference of -3.30 (95% CI: -3.98 to -2.62), and again, no heterogeneity (I² = 0%).
A sensitivity analysis confirmed the stability of these results.

How photobiomodulation works for this indication

The mechanisms discussed remain hypothetical and have not been tested in this review. Red and near-infrared light is thought to be absorbed by cytochrome c oxidase, a photon acceptor in the mitochondrial respiratory chain. This absorption could alter ATP production and signaling related to reactive oxygen species, which would locally influence the inflammatory response. A modulation of the excitability of peripheral nerve fibers and a reduction in tissue oxidative stress are sometimes proposed to explain reduced pain perception. These hypotheses remain speculative: no biological measurements confirm them here.

Limits You Should Know

The first limitation relates to the volume of data: only 3 studies support the comparison with a placebo, and 2 support the comparison with an anesthetic gel. The authors point out that the parameters vary from one study to another—particularly wavelengths and energy densities—which makes it impossible to establish a standard protocol. Their conclusion is clear: current data remain limited, and well-conducted trials with standardized protocols are needed. Finally, pain was assessed only at the time of needle insertion, not throughout the entire session.

What This Means in Practice

This study suggests that photobiomodulation may be considered as a potential adjunct prior to an anesthetic injection in children, without replacing standard techniques for managing pain and anxiety. The comparison with topical anesthetic gel shows a more pronounced difference, but it is based on only two studies. No specific protocol can be derived from this review, and the decision is up to a healthcare professional.

Frequently Asked Questions

Is photobiomodulation less painful than anesthetic gel for children?

Two split-mouth studies directly compare the two approaches and report an average difference of -3.30 (95% CI: -3.98 to -2.62) in favor of photobiomodulation. This result pertains to pain at the time of needle insertion. It is based on very few studies and cannot be generalized.

How many studies are there on photobiomodulation prior to dental anesthesia in children?

The search identified 9,852 references, of which 10 studies met the inclusion criteria. Three of these were included in the meta-analysis comparing the treatment to a placebo, and two in the meta-analysis comparing it to an anesthetic gel. This small sample size explains the authors’ caution.

What photobiomodulation settings were used in these studies?

The protocols differed in wavelength and energy density, although the specific values were not specified. It is therefore not possible to derive a reference setting from them. This is one of the reasons why the authors call for standardized protocols.

Reference

Zanchetta Peron F, Ribeiro MC, da Costa VPP, Leão Goettems M. Effect of photobiomodulation on pain perception during local anesthesia in children: a systematic review and meta-analysis. Journal of Dental Anesthesia and Pain Medicine, 2026. PMID 41640722. View the study on PubMed

This summary is provided for informational purposes only and does not constitute medical advice. Photobiomodulation is not a substitute for prescribed treatment. Consult a healthcare professional.