Objectives: Removal of subgingival hard deposits is a prerequisite for successful periodontitis therapy. This can be challenging and the advantages of a dental endoscope (PE) seem obvious, but they have not yet been investigated in detail. Moreover, the influence of the operators' experience and training with such a device on treatment results is unclear. Therefore, we investigated in an in-vitro study the use of PE for scaling and root planing (SRP), influenced by the operators' experience and training. Material and Methods: A sonic device and mini-Gracey curettes were used by eleven operators (six dentists, five dental hygienists) in periodontitis manikin heads (28 maxillary/mandibular teeth with artificial subgingival hard deposits and a mean attachment loss of 5.86mm ±2.12mm SD). The time required for treatment and the proportion of simulated hard deposits removed by SRP were measured. Significant differences were tested with the Kolmogorov-Smirnov, Shapiro-Wilk, or Chi Square test, and possible associations with Pearson correlation and Spearman's rank correlation (all tests double sided; p≤0.05). Results: Using PE led to a significant difference in the removal of simulated hard deposits [%] (mean±SD) irrespective of the operators' experience (PE: 90.78±12.10% [range: 58.80-100%]; nPE: 79.98±22.15% [range:38.10-100%]; p0.001)). Sub-analyses for different tooth types only demonstrated a significant difference in favour of PE for the front teeth (p0.001) and in the upper jaw independent of the tooth type (p0.001). The comparison of the treatment times with and without PE showed a significantly longer treatment time with PE (54.73±13.12min [range: 40-80min]) vs. nPE (33.00±11.33min [range: 20-53min] p0.001). Conclusions: Within the present pilot study, the use of PE led to more removal of simulated hard deposits but concomitantly more time effort. PE may provide additional benefits for removal of hard deposits compared to traditional SRP; however, a higher effort (time/costs) and the requirement of intensive training are necessary. Keywords: Scaling and root planing, non-surgical periodontal therapy, experimental design, subgingival hard deposits, periodontal endoscopy