CO₂ Laser Photobiomodulation and Scar Formation: A Summary of a 2023 Review
A 2023 review by Daigo and colleagues examined how CO₂ lasers may support the healing of small defects in oral soft tissue through two proposed mechanisms: artificial scab formation and photobiomodulation therapy, or PBMT.
In Part 1, we looked at the artificial scab—a coagulated and carbonized blood layer formed over the wound surface—and its proposed roles in retaining blood and wound fluid, maintaining space, and protecting developing tissue.
Part 2 focuses on the second concept discussed in the review: how PBMT may influence the biological processes involved in wound repair and scar formation.
This article expands on our short video introduction to CO₂ laser photobiomodulation and scar formation. The video provides a concise visual overview, while the sections below take a closer look at the mechanisms, research findings, and limitations discussed in the review.
What Is Photobiomodulation?
Photobiomodulation refers to the use of light energy to influence biological responses within tissue.
This differs from using a CO₂ laser to cut, vaporize, or coagulate tissue. Those applications rely primarily on direct thermal effects. PBMT is discussed in the review as a way of influencing cellular activity associated with tissue repair and scar formation.
In several of the treatment approaches described by the authors, an artificial scab is first formed through surface coagulation. PBMT is then performed during the subsequent healing process.
The two effects are presented as having different but potentially complementary roles. The artificial scab may help maintain the physical healing environment, while PBMT may influence the biological activity occurring beneath and around the wound.
TGF-β1, Myofibroblasts, and Scar Formation
Two important factors discussed in the review are transforming growth factor beta 1, or TGF-β1, and myofibroblasts.
Fibroblasts participate in the formation of connective tissue and collagen during wound repair. Under the influence of signaling factors including TGF-β1, some fibroblasts differentiate into myofibroblasts.
Myofibroblasts have contractile properties that help draw the edges of a wound together. This makes them important for normal wound closure. However, persistent or excessive myofibroblast activity may also contribute to excessive collagen deposition, fibrosis, scar contracture, and changes in tissue contour.
The review describes findings suggesting that PBMT may downregulate TGF-β1 expression and reduce markers associated with myofibroblast activity.
Importantly, TGF-β1 is not simply a harmful factor that should always be suppressed. It plays an important role during early wound repair. The timing of its regulation may therefore matter, with reduced activity during later phases potentially helping to limit excessive fibrosis.
What Has the Research Reported?
The review discusses basic and animal studies examining the effects of laser irradiation on biological processes associated with scar tissue.
Reported findings included:
Reduced TGF-β1 expression
Lower expression of α-smooth muscle actin, or α-SMA
Reduced excessive collagen production
Changes in collagen fiber density and organization
Reduced activity of fibroblasts associated with scar tissue
α-SMA is commonly used as a marker of myofibroblast activity. A reduction in α-SMA expression may therefore indicate lower myofibroblast differentiation or activity.
The review also cites clinical studies involving scars resulting from trauma, burns, surgical wounds, acne, and cleft lip repair. Some of these studies reported improvements in scar thickness, hardness, flexibility, elasticity, and appearance following CO₂ laser treatment.
Taken together, these findings suggest possible biological pathways through which laser treatment may influence fibrosis and scar formation.
However, most of the clinical evidence cited in this section comes from studies involving skin scars, including fractional CO₂ laser treatments. These studies provide relevant background, but they are not equivalent to evidence for PBMT during oral soft-tissue healing.
Why This Research Matters in Dentistry
Scar formation is a normal part of tissue repair, but excessive contraction or fibrosis may lead to undesirable esthetic or functional changes.
In the oral cavity, even relatively small soft-tissue defects may sometimes result in:
Mucosal concavity
Gingival recession
Altered tissue contours
Scar contracture
Changes in the movement of the lips, tongue, or cheeks
The review discusses PBMT in connection with clinical situations such as open lip wounds, extraction sockets, and free gingival graft procedures.
In these examples, artificial scab formation is proposed to help retain blood and wound fluid, maintain space, and protect the wound surface. Subsequent PBMT is proposed to influence cellular activity associated with healing and scar formation.
Because artificial scab formation and PBMT are often used together in the clinical examples, it may be difficult to determine how much of an observed outcome results from the artificial scab, PBMT, or the combination of both.
Interpreting the Evidence
Evidence remains limited, particularly for oral mucosa. The review does not establish a standardized treatment protocol or demonstrate that CO₂ laser PBMT consistently prevents scarring after oral soft-tissue surgery. Because outcomes may vary with tissue type and irradiation conditions, appropriate technique and careful case selection remain essential. Further clinical research is needed to determine when PBMT may provide predictable benefits.
Conclusion
The review presents PBMT as a potential biological component of CO₂ laser-assisted wound management.
Experimental findings suggest that PBMT may influence TGF-β1 expression, myofibroblast activity, and collagen-related processes associated with fibrosis. Clinical studies involving skin scars have also reported changes in scar thickness, hardness, flexibility, elasticity, and appearance.
However, evidence involving oral soft tissue remains limited. The findings should therefore be viewed as an evolving area of research rather than proof of a universally established clinical outcome.
Together with artificial scab formation, PBMT provides an important framework for understanding how researchers are examining CO₂ lasers beyond cutting and hemostasis—including their possible influence on tissue repair and scar formation.
Read Part 1
For the first concept discussed in the review, read:
Source
Daigo Y, Daigo E, Fukuoka H, et al. CO₂ Laser for Esthetic Healing of Injuries and Surgical Wounds with Small Parenchymal Defects in Oral Soft Tissues. Diseases. 2023;11(4):172.
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