Background: A fiber-optic periodontal endoscope was developed to aid in the visualization of subgingival structures and to improve the diagnosis and management of periodontal diseases. The purpose of this study was to determine whether use of the periodontal endoscope with scaling and root planing (SRP) resulted in a decrease in residual calculus compared to SRP alone. Methods: Fifteen subjects with 50 tooth pairs participated in this study. Each tooth per pair was randomized to receive SRP with or without the endoscope. Teeth were extracted, and a stereomicroscope and digital image analysis was used to determine percent residual calculus present in a masked fashion. Results: There was 2.14% (P< 0.001) more residual calculus at control versus test sites. At buccal/lingual and interproximal surfaces, mean differences in residual calculus were 1.30% (P<0.015) and 2.93% (P< 0.001), respectively. Test treatment time decreased significantly as operator experience increased. There were no statistically significant differences between residual calculus for test and control teeth at shallower probing depths; however, at deeper probing depths, the use of the endoscope resulted in significantly less residual calculus. Conclusions: The use of the periodontal endoscope resulted in a statistically significant overall improvement in calculus removal during SRP, which was most evident in deeper probing depths. The clinical significance of this level of improvement is unknown.