ABSTRAKPendahuluan: Resin akrilik polimerisasi panas memiliki kekurangan pada sifat mekanis sehingga diperlukan bahan penguat yaitu kitosan. Kitosan dapat meningkatkan sifat-sifat RAPP yang berkaitan dengan kekasaran permukaan dan jumlah Candida albicans. Tujuan penelitian menganalisis pengaruh penambahan kitosan 5, 6, 7, 8, dan 9% pada bahan basis gigi tiruan RAPP terhadap kekasaran permukaan dan jumlah Candida albicans. Metode: Jenis penelitian eksperimental laboratoris. Sampel berjumlah 42 berukuran 12 x 12 x 3 mm untuk kekasaran permukaan dan 30 sampel berukuran 10 x 10 x 1 mm untuk Candida albicans yang dibagi menjadi 6 kelompok (kontrol, 5, 6, 7, 8, dan 9%) kemudian dicampurkan dengan RAPP dan di curing untuk menghasilkan basis akrilik. Sampel dikontaminasi dengan Candida albicans kemudian dihitung koloni yang melekat pada permukaan basis dengan colony counter. Hasil perhitungan kekasaran permukaan dianalisis dengan uji One-way ANOVA and LSD sedangkan jumlah Candida albicans diuji dengan Kruskal-Wallis dan Mann-Whitney. Hasil: Nilai rerata kekasaran permukaan kelompok kontrol sebesar 0,105±0,006; kitosan 5, 6, 7, 8, dan 9% sebesar 0,123±0,006; 0,137±0,005; 0,147±0,004; 0,158±0,005; 0,176±0,007 berturut-turut. Nilai rerata jumlah Candida albicans kelompok kontrol sebesar 250,60 ± 6,88; kitosan 5, 6, 7, 8, dan 9% sebesar 112,60 ± 4,78; 95,00 ± 2,00; 84,40 ± 3,29; 5,20 ± 1,64; 0,60 ± 0,90 berturut-turut dengan nilai p = 0,0001 (p<0,05). Simpulan: Penambahan kitosan 5% dapat dijadikan sebagai bahan penguat pada bahan basis gigi tiruan RAPP dengan nilai kekasaran permukaan tidak melebihi 0,2 μm sehingga dapat diterima secara klinis dan penggunaan kitosan 9% efektif mengurangi jumlah Candida albicans.Kata kunci: resin akrilik polimerisasi panas, bahan penguat, kitosan, kekasaran permukaan, candida albicans The effect of chitosan addition on polymethyl methacrylate denture base on surface roughness and against Candida albicans growth: a laboratory experiment studyABSTRAKIntroduction: Polymethyl methacrylate (PMMA) has deficiencies in mechanical properties, so a reinforcing agent, chitosan, is required. Chitosan can improve properties of PMMA. This experimental laboratory study was aimed to determine effects of 5, 6, 7, 8, and 9% chitosan addition on PMMA denture base on surface roughness and against Candida albicans growth. Methods: A total of 42 samples (12 x 12 x 3 mm) for surface roughness and 30 samples (10 x 10 x 1 mm) for Candida albicans were divided into 6 groups (control, 5, 6, 7, 8, and 9%). The chitosan was mixed with PMMA and cured to create acrylic plates. Samples were contaminated with Candida albicans and the remaining colonies were measured by colony counters. Surface roughness value were analyzed by One-way ANOVA and LSD meanwhile Candida albicans growth were analyzed by Kruskal-Wallis and Mann-Whitney. Results: The mean value of surface roughness on control group was 0.105 ± 0.006; 5, 6, 7, 8, and 9% was 0.123 ± 0.006; 0.137 ± 0.005; 0.147 ± 0.004; 0.158 ± 0.005; 0.176 ± 0.007. The mean value of the number of Candida albicans on control group was 250.60 ± 6.88; 5%, 6%,7%,8%,9% at 112.60 ± 4.78; 95.00 ± 2.00; 84.40 ± 3.29; 5.20 ± 1.64; 0.60 ± 0.90 with p value = 0.0001 (p<0.05). Conclusion: Addition of 5% chitosan can be used as reinforcement material of PMMA with surface roughness value not exceeding 0.2 μm so that it was clinically accepted. Addition of 9% chitosan was effective in reducing adherence of Candida albicans.Key wordheat polymerized acrylic resin, reinforcement, chitosan, surface roughness, candida albicans