<p><strong><em>Background: </em></strong><em>Periodontitis is the most severe complication in oral cavity to diabetes mellitus</em><em>. Stichopus hermanii contain GAG, a polysaccharide which very useful in wound healing. Hyperbaric oxygen therapy is effective repairing ischemia, hypoxia, and is used as adjuvant therapy. <strong>Purpose:</strong> To determine effect of administration of Stichopus hermanii (SH) 3% gel and hyperbaric oxygen therapy 3x30 minutes with 5 minute intervals in 7 consecutive days to the number of fibroblasts in ligament periodontal diabetes mellitus rats with periodontitis. <strong>Materials and Methods: </strong></em><em>The experiment design is factorial design. Rats are inducted with STZ single dose 65 mg/kgBB to make them suffer DM and are inducted with P.gingivalis 1x10⁹sel/ml for 5 days straight to make them suffer periodontitis. 20 male wistar rats are divided into 5 groups.</em><em> K^- (control), K1 (STZ+P.Gingivalis), K2(STZ+P.Gingivalis+SH), K3(STZ+P.Gingivalis+HBO), K4(STZ+P.Gingivalis+SH+HBO). After </em><em>52 days treatment, rats is terminated to make a HPA Sample from the mandible and fibroblast is counted with 400x magnification</em><em>. <strong>Result: </strong>One-way Annova here were significant differences (p&lt;0,05) in K^- (32.300 ± 11.381), K1 (31.725 ± 5.590), K2 (54.225 ± 7.165), K3 (49.725 ± 10.088), K4 (72.075 ± 9.342). <strong>Conclusion:</strong> administration of Stichopus hermanii 3% gel combination and 2.4 ATA hyperbaric oxygen 3x30 minutes a day with 5 minutes intervals in 7 consecutive days can increase the number of fibroblasts in diabetes mellitus rats with periodontitis.</em></p><p><strong><em> </em></strong></p><p><strong><em>Keywords:</em></strong><em> Stichopus hermanii, hyperbaric oxygen, diabetes, periodontitis, fibroblasts</em></p><p><strong><em> </em></strong></p><p><strong><em>Correspondence:</em></strong><em> Dian Mulawarmanti, Department of Oral Biology,Faculty of Dentistry, , Hang Tuah University, Arif Rahman Hakim 150, Surabaya, Phone 031-5945864, Email: </em><a href="mailto:dian.mulawarmanti@hangtuah.ac.id"><em>dian.mulawarmanti@hangtuah.ac.id</em></a><em></em></p>