Background: Diabetes increases periodontal disease risk and its complications, which are worsened with age or faulty restorations. Aim: Evaluate periodontal health among patients with diabetes treated with different dental restorations. Materials and Methods: This comparative cross-sectional study was conducted at the faculty of dentistry, Najran University, KSA, from March 2018 to February 2020. It included 260 diabetics, treated with different dental restorations, divided into four groups, each comprising 65 patients aged 45 -60 years: Group 1 (G1), no restorations (control group); Group 2 (G2), Class II amalgam restorations; Group 3 (G3), Class II composite resin restorations; and Group 4 (G4), three-unit posterior metal ceramic prostheses. The Ages of all restorations ranged from 8 to 10 years. All groups were assessed for the Plaque Index (PI) and Gingival Index (GI), Overhangs Rate (OR), Alveolar Bone Loss (ABL) (the latter two using panoramic X-ray). HbA1c and duration of participants were also assessed and compared. Results: The mean HbA1c results of the groups ranged from 8.1% to 9.5%, and their mean diabetes durations ranged from 7.2 to 12 years. All the groups showed worse periodontal scores, ranging from 2.45 -2.95 for PI and 2.25 -2.8 for GI. G2 had higher scores than G1 and G3 (p < 0.001). G4 had the highest two recorded scores (p < 0.001). G2 had a higher rate of overhangs than G3 (p < 0.037). The mean ABL was 44% (SD 6.4) for G1, 56.0% (SD 6.7) for G2, 46.5% (SD 5.8) for G3, and 74.5% (SD 6.4) for G4. The lowest values were recorded in G1 and G3 (p = 0.987). The highest value was observed in G4, which was significantly high-