The distribution- and anchor-based methods will be used to estimate the Minimal Important Difference (MID) of the OHIP-P-HIN. Two established distribution-based approaches, the standardized effect size (ES) and standardized response mean (SRM) will be calculated. The ES is calculated by dividing the mean change scores in the OHIP-P-HIN from baseline by the standard deviation of the baseline scores. And the SRM are computed as ratios of the mean change score divided by its standard deviation. The anchor-based approach will be applied by using the global transition scale as the anchor.

Inclusion Criteria:

• ≥18 years of age
• patients able to understand and complete questionnaires independently
• confirmed diagnosis of periodontitis

Exclusion Criteria:

• Patients with systemic diseases such as acquired immunodeficiency syndrome or diabetes mellitus
• pregnancy
• required prophylactic antibiotic coverage prior to dental treatment,
• patients with bleeding disorders
• patients who had received non-surgical periodontal therapy within the preceding eight weeks.