Background: Type 2 diabetes mellitus (T2DM) and chronic periodontitis share a well-documented bidirectional relationship in which hyperglycaemia predisposes to periodontal breakdown and periodontal inflammation, in turn, worsens glycaemic control. Whether the addition of homecare sub-gingival water irrigation to non-surgical periodontal therapy (NSPT) provides an incremental clinical, glycaemic, and inflammatory benefit over conventional oral hygiene alone in this population remains inadequately defined.

Objective: To comparatively evaluate the effect of homecare sub-gingival irrigation versus standard tooth-brushing and flossing, both delivered after NSPT, on periodontal, glycaemic, and inflammatory parameters in adults with T2DM and chronic periodontitis.

Methods: A single-blind, randomized controlled trial was conducted over eighteen months at the Department of Periodontology and Oral Implantology, Yamuna Institute of Dental Sciences and Research, Yamuna Nagar, Haryana, India. A total of 140 patients with T2DM (HbA1c below 7%) and generalized chronic periodontitis were randomized, using research randomizer software, into two equal groups of 70. Group 1 used a powered sub-gingival water irrigator twice daily in addition to brushing; Group 2 performed conventional brushing and flossing twice daily. Gingival Index (GI), Plaque Index (PI), Oral Hygiene Index-Simplified (OHI-S), Gingival Bleeding Index (GBI), probing depth (PD), and clinical attachment loss (CAL) were recorded at baseline, one, three, and six months. HbA1c and C-reactive protein (CRP) were recorded at baseline and six months. Repeated-measures ANOVA with post-hoc Bonferroni correction and independent-sample t-tests were used, with significance set at p<0.05. Results: Both groups improved significantly across all clinical indices over six months. Inter-group comparison favoured

Group 1: mean GI at six months was 0.48±0.36 versus 0.78±0.32 (p=0.009), PD was 2.24±0.48 mm versus 3.60±0.51 mm (p<0.001), and CAL was 0.63±0.60 mm versus 1.01±0.57 mm (p=0.049). CRP fell from 17.06±2.42 mg/L to 6.96±1.21 mg/L in Group 1 compared with 18.27±2.38 mg/L to 10.17±1.90 mg/L in Group 2 (p<0.001 at six months). HbA1c declined in both groups (Group 1: 6.69% to 6.44%; Group 2: 6.76% to 6.52%) without a statistically significant inter-group difference (p=0.182). Conclusion: Adjunctive homecare sub-gingival irrigation produced significantly greater improvement in periodontal clinical parameters and systemic inflammatory status than conventional oral hygiene alone in diabetic patients with chronic periodontitis, although the two protocols did not differ significantly in their effect on glycaemic control at six months.