Introduction: According to the actual EFP guidelines, first step of periodontal therapy should include oral hygiene instructions (OHI), comprising the use of interdental brushes (IDBs). Yet, non-conclusive evidence exists for their effect. The present multicentric clinical controlled explorative study compared the clinical outcomes of two NSPT (non-surgical periodontal therapy) concepts under university settings, one with (in Germany (NSPT-G)) and one without IDBs (in Egypt (NSPT-E)). Methods: 23 stage III/IV periodontitis patients (NSPT-G/NSPT-E:11/12) were examined before (T0) and after NSPT (T1). Patients' demographic data, tooth loss, clinical attachment loss (CAL), probing depths (PD) and bleeding on prob-ing (BOP) were assessed. ANOVA and Mann-Whitney-U tests were used for statistical analysis. Results: Baseline differences were observed in terms of age, severity and tooth number per patients. NSPT duration was 1.6 times longer in NSPT-G vs. NSPT-E. Improvements of BOP, PD and CAL were observed in both groups, with greater mean percentage reduction of PD for NSPT-G vs. NSPT-E (–26.86 (9.29) %/–12.61 (9.38) %; p=0.004). Similar effects were observed for changes in CAL, with higher improvement in NSPT-G vs. NSPT-E (–34.84 (11.18) %/–10.98 (10.6) %; p0.001). Conclusion: Both NSPT concepts achieved significantly beneficial clinical effects for patients within their socio-economic circumstance. However, according to the limitations of the explorative study, a clear benefit for a treatment concept comprised of NSPT in combination with comprehensive OHI and IDC during periodontal treatment remains unconfirmed. Keywords: bleeding on probing, instruction, motivation, non-surgical periodontal therapy, oral hygiene, periodontitis