Background/Objectives: Psoriasis and periodontitis share inflammatory pathways. Current evidence suggests a bidirectional non-causal relation. However, the evidence on the effects of periodontal treatment on psoriasis outcomes (severity, inflammatory markers, quality of life) is limited. This study aims to synthetize the available clinical and preclinical evidence of periodontal treatment effects on psoriasis outcomes, in patients with comorbid psoriasis and periodontitis (CRD420261298145). Methods: Several databases (PubMed, WebOfScience, ScienceDirect, ProQuest and GoogleScholar) were searched for relevant articles, without language or time restrictions. We included randomised and non-randomised clinical studies on humans, and controlled animal experiments. Interventions included periodontal treatment (surgical and non-surgical). Outcomes were the Psoriasis Area and Severity Index and dermatology-specific quality of life scores; secondary outcomes included inflammatory biomarkers and periodontal parameters. Studies were screened in duplicate, data extracted independently and risk of bias was assessed using Cochrane RoB 2, ROBINS I, NOS and SYRCLE. Results: A total of five studies were included in this systematic review (four clinical studies and one preclinical studies). Three studies directly assessed post-treatment psoriasis outcomes, with two studies investigating inflammation mediators as secondary outcomes. Two studies directly assessed PASI (Psoriasis Area and Severity Index) modifications, both studies confirming PASI scores decreasing post-periodontal treatment; one study also reported DLQI (Dermatology Life Quality Index). Typical follow-up durations ranged from 8 to 10 weeks for interventional studies, to 5 years for one cohort study. Conclusions: Although momentarily limited by the small number of available studies, the results of this review suggest that periodontal treatment may be associated with improvements in psoriasis outcomes. Further studies on larger samples, with longer follow-up periods would be necessary to confirm and possibly strengthen the existing results.
