Er:YAG Laser Versus Systemic Metronidazole as an Adjunct to Nonsurgical Periodontal Therapy: A Clinical and Microbiological Study Selc ¸ uk Yilmaz, D.D.S., Ph.D., 1 Burak Kut, D.D.S., Ph.D., 1 Hare Gursoy, D.D.S., Ph.D., 1 Bahar Eren Kuru, D.D.S., Ph.D., 2 Ulku Noyan, D.D.S., Ph.D., 2 and Tanju Kadir, D.D.S., Ph.D. 3 Abstract Objective: The objective of this randomized clinical trial was to describe the clinical and microbiological results obtained by treatment with Er:YAG laser and systemic metronidazole used as adjuncts to mechanical sub- gingival debridement in chronic periodontitis. Methods: Twenty-seven chronic periodontitis (CP) patients were randomly divided into three parallel groups each comprising nine individuals with at least four teeth having at least one approximal site with a probing depth (PD) of ‡ 5 mm and gingival index (GI) of ‡ 2 in each quadrant. Groups of patients received: (1) Scaling and root planing (SRP) + Er:YAG laser (10 hz, 30 mJ/pulse, 1 min per pocket, apico-coronal direction in parallel paths with 30 degree angle tips, under water irrigation), (2) SRP + systemic metronidazole, or (3) SRP alone. In all treatment groups, SRP was performed at 1 week intervals in two sessions. The microbiological and clinical effects of the treatments were evaluated after 90 days. Results: At the end of the experimental period, statistically significant improvements in plaque index, GI, PD and attachment level, as well as reductions in the number of total bacteria and proportions of obligately anaerobic microor- ganisms were observed within each group. Although intergroup comparisons revealed no significant microbi- ological differences, clinical parameters as attachment gain and PD reduction were found significantly higher in Group 1 compared with the other groups. Conclusions: Within its limits, this study demonstrated the possibility of better resolution of infection with combined SRP + Er:YAG laser treatment. However, microbiological results failed to demonstrate significant advantages of this combination in comparison with SRP alone or SRP + systemic metronidazole. Introduction The primary objective of mechanical periodontal treat- ment is to disrupt subgingival biofilm and remove bacterial deposits from root surfaces, in an effort to stop tissue de- struction, and eliminate or control etiologic agents, together with creating a microbial shift toward what is typically present in health. 1–3 However, mechanical periodontal therapy alone may fail to eliminate the pathogenic bacteria in deep peri- odontal pockets and within the gingival and dental tissues or in other areas inaccesible to periodontal instruments. 4–6 Therefore, suggestions have been made regarding the devel- opment of treatment strategies that focus on supression or elimination of specific periodontopathogens and control their overgrowth on tooth surface 7 . The adjunctive antimicrobial therapeutic rationales depend upon systemic and local administration of antibiotics as well as new developing tech- nical modalities using sophisticated tools such as lasers, ozone gas, or photodynamic therapy. The choice of the antibiotics in periodontal diseases must be based on the specific bacterial etiology. 8 Several antibiotics have been tested for their clinical and microbiological efficacy in periodontal diseases. Among the antibiotics that are being considered for periodontal treat- ment, metronidazole is particularly preferable because of its selective efficacy against obligate anaerobes. 9 It has a narrow spectrum and works specifically on the anaerobic flora asso- ciated with periodontitis, leaving the flora associated with health intact. Treatment with metronidazole has been shown to improve clinical parameters and reduce the number of disease-related bacteria. 10–17 Laser systems such as Nd:YAG, diode, and Er:YAG have antibacterial effects and exert their bactericidal effects via 1 Yeditepe University, Facuty of Dentistry, Department of Periodontology, Bagdat Cad, No: 238, Go ¨ ztepe, Istanbul, Turkey. 2 Marmara University, Facuty of Dentistry, Department of Periodontology, Bu ¨ yu ¨ kciftlik sok. Nisantasi, Istanbul, Turkey. 3 Marmara University, Faculty of Dentistry, Department of Microbiology, Bu ¨ yu ¨ kciftlik sok. Nisantasi, Instanbul, Turkey. Photomedicine and Laser Surgery Volume 30, Number 6, 2012 ª Mary Ann Liebert, Inc. Pp. 325–330 DOI: 10.1089/pho.2010.2762 325