Diode and erbium lasers in periodontology: what the studies actually show

How to read these studies

Three concepts help interpret the results. The mean difference between two groups, in millimetres of pocket depth or attachment, shows whether an add-on contributes anything beyond the standard treatment. Clinical relevance asks a different question: does a gain of a few tenths of a millimetre, even if statistically significant, change the outlook for a tooth? Finally, the certainty of evidence (rated with the GRADE method) indicates how far the result can be trusted: it falls when trials are small, at risk of bias or inconsistent.

In periodontology, the main outcomes are pocket depth (measured in millimetres with a fine graduated gauge), clinical attachment level (the height of supporting tissue remaining around the root) and bleeding provoked by that measurement, which reflects inflammation. Tooth loss, the outcome that matters most to patients, is rarely measured in laser trials, which are too short for that.

It also matters what kind of study is being discussed. An in vitro study, in the laboratory, measures for instance the number of bacteria destroyed on a surface or in a tube: it informs about a mechanism, not about a patient's recovery. A randomised trial compares, in patients allocated by chance, treatment with and without a laser: this is what answers the clinical question. A systematic review gathers all available trials on a question, assesses their quality and, where possible, combines their results in a meta-analysis; the European guidelines rest on such reviews. In this article, the nature of each source is stated.

The benchmark: mechanical cleaning

A systematic review prepared for the European guideline, based on clinical trials, estimates that after subgingival instrumentation pocket depth falls by an average of 1.7 mm (95% CI 1.3–2.1) at 6–8 months and that about 74% of pockets close ^[7]. A laser added to this treatment must therefore provide a measurable extra gain on top of this already substantial effect. These average results and what they mean for the patient are summarised on the page How periodontitis is treated, which refers here for the detail.

Diode and other lasers as an adjunct to root planing

The systematic review by Salvi et al. (2020), carried out for the EFP guideline, identified 17 randomised trials: 10 on lasers (370 patients) and 8 on photodynamic therapy (331 patients) ^[2]. For lasers, the variety of devices, settings and protocols was such that no meta-analysis could be performed. The risk of bias was rated unclear in all studies. The authors conclude that the available evidence on adjunctive lasers and photodynamic therapy (aPDT) is limited by the small number of controlled studies and the heterogeneity of their protocols, and that patient-reported benefits remain to be demonstrated.

Er:YAG: promising on paper

Er:YAG has attractive physical properties: it removes calculus and a thin layer of tissue with little heating, as shown mainly by laboratory studies and review work ^[8]. Clinically, a review of systematic reviews published in 2024 analysed four reviews of its use in non-surgical treatment, themselves based on randomised trials ^[4]. Two of them reported a significant reduction in pocket depth at 3 months; at 6–12 months, no significant improvement in attachment level, pocket depth or recession was found. The methodological quality of the included reviews ranged from high to critically low. The authors conclude that evidence of effectiveness is weak and clinical benefit has not been shown.

In other words, Er:YAG appears able to partly replace conventional instrumentation without doing better. Any practical advantage (comfort, access to certain areas) remains to be shown in patient-centred trials.

Antimicrobial photodynamic therapy (aPDT)

aPDT combines a dye placed in the pocket with a light, often from a diode laser, which activates the dye to release reactive oxygen species that are toxic to bacteria. It is the most studied laser-based add-on.

The Cochrane review by Jervøe-Storm et al. (2024), a systematic review with meta-analysis, included 50 randomised trials and 1,407 participants ^[3]. In active treatment of periodontitis, adding aPDT reduced pocket depth by 0.52 mm more than instrumentation alone at 6 months (95% CI 0.31–0.74), improved attachment by 0.44 mm (CI 0.24–0.64) and reduced bleeding by about 6 percentage points. In maintenance (6 trials), the difference in pocket depth was nil (−0.04 mm).

The certainty of these results is very low (risk of bias, small samples, heterogeneity). The authors consider that any improvements may be too small to be clinically important. On a reassuring note, 24 trials (639 participants) observed no adverse effects related to aPDT. The 2020 European guideline does not suggest aPDT as an adjunct ^[1].

Around implants

The 2023 European guideline on peri-implant diseases examined the same questions ^[5]. For peri-implant mucositis (reversible inflammation of the mucosa around an implant), it suggests not adding a diode laser to professional cleaning, and does not suggest aPDT. For peri-implantitis (with bone loss), it does not suggest using lasers, as an adjunct or alone, nor Er:YAG to decontaminate the implant surface during surgery. Peri-implant prevention and treatment are covered in the article Gum care around implants.

Where lasers remain useful: soft tissue

For frenectomy, a 2021 systematic review (10 trials, 375 patients) reports less bleeding, no need for stitches and generally less post-operative pain with a laser than with a scalpel ^[6]. In one study, healing was more advanced with the scalpel at one week and one month, with no difference at three months. The studies were few and used different lasers, which prevented a meta-analysis. These results point to a practical benefit without amounting to strong proof.

What remains to be shown

• Large randomised trials at low risk of bias, with standardised settings reported in detail.
• Patient-centred outcomes: pain, comfort, number of visits, need for later surgery, long-term tooth loss.
• Subgroups in which a benefit might exist (deep pockets, diabetes, smoking), which are currently under-studied.
• Head-to-head comparisons between the diode laser and the Er:YAG laser, whose wavelengths and effects are not interchangeable.
• Cost evaluation: an expensive add-on should deliver a proportionate benefit.

Some teams are also studying biological effects of lasers (photobiomodulation, modulation of inflammation). This work relies mainly on laboratory studies and small case series: these are hypotheses, not effects demonstrated in patients. Likewise, the percentages of bacteria destroyed that one sometimes reads come from in vitro studies or immediate samples; they do not measure the lasting clinical result.

What this means for the patient

For someone being treated for periodontitis, these data have three practical consequences. First, the treatment that counts is mechanical root cleaning, root surface debridement, followed by maintenance: this is what closes pockets and stabilises the disease, laser or no laser. Second, a laser added in the pockets can only be presented as an adjunct whose additional benefit is, at most, modest and uncertain; it does not justify expecting an assured better result, forgoing debridement or spacing out periodontal maintenance. Finally, for procedures on the gum (frenum, gingivectomy), the laser brings real, documented comfort, even if studies remain few.

At the practice in Levallois-Perret, Dr Hazout applies this reading: debridement remains the basis; the diode or Er:YAG laser is proposed after it, in some pockets and for gum procedures, with the patient informed of the modest benefit to be expected and of the fact that the European guideline does not suggest it as an adjunct. The situations retained and the cost are set out on the Lasers page, the full treatment on the page How periodontitis is treated.

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