Periodontitis in patients with primary Sjögren's syndrome: A nation-wide register study.

The aim of this study was to compare the occurrence of periodontitis in patients with primary Sjögren's syndrome (pSS) and a non-Sjögren's patient group during a 7-year period from 2011 through 2017. In this population-based study, the patients were identified based on the International Classification of Diseases-10 (ICD-10) codes registered in the Norwegian Patient Registry (NPR), which contains information on diagnosis and time of admission for all hospitalized patients in Norway. The pSS group comprised patients with ≥4 registrations with ICD-10 code M35.