Photobiomodulation Therapy as Adjunct to Scaling and Root Planing for Patients with Type 2 Diabetes Mellitus Complicated by Chronic Periodontitis: A Systematic Review and Meta-Analysis

Abstract

Background:

Type 2 diabetes mellitus (T2DM) and chronic periodontitis (CP) have a bidirectional association; scaling and root planing (SRP) alone has limited efficacy in their comorbidity, with controversial photobiomodulation therapy (PBMT) adjunctive efficacy.

Objective:

To quantify PBMT + SRP’s effects on periodontal [probing depth (PD), clinical attachment level (CAL)], glycemic [fasting plasma glucose (FPG), glycated hemoglobin (HbA1c)], and inflammatory [high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α)] indices in patients with T2DM + CP and explore heterogeneity (PBMT parameters, study region) for clinical optimization.

Methods:

Following PRISMA 2020, we searched six databases (PubMed, Cochrane Library, etc.) from inception to August 24, 2025, for PBMT-adjuvanted SRP randomized controlled trials (RCTs). Bias was assessed via RoB 2.0, meta-analysis via RevMan 5.4, with preset subgroup analyses.

Results:

Six RCTs (n = 319) were included. At 3 months of follow-up, PBMT + SRP significantly improved key periodontal indices (PD: MD = −0.87 mm, 95% CI: [−1.00, −0.74]; CAL: MD = −0.47 mm, 95% CI: [−0.65, −0.29]; both p < 0.00001), glycemic control (FPG: MD = −0.79 mmol/L, 95% CI: [−1.41, −0.17], p = 0.01), and systemic inflammation (hs-CRP: MD = −0.99 mg/L, 95% CI: [−1.12, −0.86]; TNF-α: MD = −2.78 pg/mL, 95% CI: [−3.17, −2.39]; both p < 0.00001) versus SRP alone. HbA1c showed borderline significant reduction (MD = −0.81%, 95% CI: = [−1.62, −0.01], p = 0.05). Subgroup analyses suggested 808/810 nm + 0.8–1.5 W as potentially optimal PBMT parameters, though high-power efficacy relied on one small-sample study (n = 40). Notable limitations included high inter-study heterogeneity (most I² > 90%) and maximum 6-month follow-up.

Conclusions:

PBMT adjunctive to SRP significantly improves periodontal indices (PD, CAL), FPG, and hs-CRP in patients with T2DM and CP, with borderline HbA1c reduction and good safety. Subgroup analyses identify 808/810 nm + 0.8–1.5 W as potentially optimal PBMT parameters, though high-power efficacy relies on one small-sample study. Given high inter-study heterogeneity (most I² > 90%) and short follow-up (maximum 6 months), conclusions require validation by standardized, large-sample, long-term, high-quality RCTs.