Nascimento M.F.D.S. et al. - Preemptive Photobiomodulation and Pain from Dental Anesthetic Injections: A Systematic Review and Meta-Analysis

In 1,519 patients across 27 randomized trials, a photobiomodulation session administered immediately before a dental anesthetic injection was associated with a 1.72-point reduction in pain on the visual analog scale. The effect was not observed on the SEM scale, and the authors rated the certainty of the evidence as very low.

What this study measured

Fear of needles remains one of the main reasons people avoid dental care. This systematic review and meta-analysis, registered under the number PROSPERO CRD42025641468, examines a so-called preemptive approach: applying photobiomodulation to the oral mucosa before the anesthetic injection, rather than after, in order to reduce the pain of the procedure itself.

The authors identified 27 randomized clinical trials involving a total of 1,519 participants, 25 of which were included in the meta-analysis. The interventions included dental and craniomaxillofacial procedures. Pain was measured using several instruments: the visual analog scale, the Pain Rating Scale, the FLACC behavioral scale, and the SEM scale. The certainty of the results was assessed using the GRADE method.

Key Findings

Preemptive photobiomodulation is associated with a significant reduction in pain on three of the four measures analyzed.

• Visual Analog Scale: mean difference of -1.72 points (95% CI: -2.87 to -0.57)
• Pain Rating Scale: mean difference of -0.89 points (95% CI: -1.59 to -0.20)
• FLACC Scale: mean difference of -1.14 points (95% CI: -1.90 to -0.37)
• SEM scale: mean difference of -0.56 points (95% CI -1.72 to 0.60), with no significant effect
• Heterogeneity across studies: I² ranging from 96.7% to 98.9%, tau ranging from 0.93 to 1.97

The results on the SEM scale are worth noting: the confidence interval crosses the zero value, which means that no difference could be established between this group and the control group on this measure.

How photobiomodulation works for this indication

The hypothesis put forward in the literature is based on a local effect on nerve conduction and on inflammatory mediators at the irradiated site. Low-intensity red and near-infrared light is absorbed by mitochondrial chromophores, which is thought to temporarily alter the depolarization threshold of superficial nociceptive fibers. When applied before the procedure, it is therefore intended to reduce pain perception at the moment of needle penetration, rather than to accelerate recovery.

This review does not test this mechanism. It measures a clinical effect and does not allow us to distinguish between a specific neurophysiological effect and a component related to patient expectations.

Limits You Should Know

Heterogeneity is the major weakness of this study. With an I² ranging from 96.7% to 98.9%, the results of the individual trials vary widely, to the point that the authors report wide prediction intervals. In other words, the extent of the expected benefit for a given patient remains highly uncertain.

The authors also report methodological limitations in the included trials and conclude that the GRADE certainty is very low for all outcome measures. Very low certainty means that future studies are likely to substantially change the estimate. Finally, the null result on the SEM scale shows that the conclusion depends in part on the measurement instrument used.

What This Means in Practice

The evidence suggests that photobiomodulation may be beneficial as an adjunctive measure prior to local dental anesthesia, particularly in anxious patients or children, in whom the FLACC behavioral scale also shows improvement. The procedure is noninvasive, and no significant adverse effects are reported in this review.

The decision remains the practitioner’s responsibility. Given the very low level of certainty, photobiomodulation is not a substitute for any anesthesia protocol and should be considered a complementary treatment.

Frequently Asked Questions

Does photobiomodulation relieve the pain of a dental injection?

No. In this meta-analysis, it is associated with an average decrease of 1.72 points on a visual analog scale, which represents a partial reduction rather than a complete elimination. One in four instruments shows no difference.

How many studies support this finding?

Twenty-seven randomized clinical trials involving a total of 1,519 participants were included, twenty-five of which were incorporated into the meta-analysis. However, the authors rate the certainty of the evidence as very low.

Is this approach suitable for children?

The FLACC scale, used for patients who are unable to verbalize their pain, shows a reduction of 1.14 points. This finding still needs to be confirmed by dedicated studies and discussed with the dentist.

Reference

Nascimento MFDS, Almeida JES, Gomes MCM, Costa LSD, Silva PGB, Damasceno JX, Verde MEQL. Preemptive photobiomodulation therapy for reducing pain during local anesthetic needle puncture in dental and craniomaxillofacial procedures: a systematic review and meta-analysis of randomized clinical trials. Journal of Dentistry, 2026. PMID 42259468. PubMed link

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.