Although the relation between periodontitis (PD) and systemic disorders (e.g. cardiovascular diseases, diabetes and rheumatoid arthritis) is widely accepted, the association with ankylosing spondylitis (AS) is inconsistently mentioned. We prospectively examined the relationship between periodontal disease and AS, focusing on the rate and course of PD, factors associated with severity and the impact of anti-TNF-α treatment on inflammatory status. Standard assessments performed twice (week 0, week 24) included an extensive dental evaluation (plaque index, gingival index, bleeding on probing, periodontal pocket depth, clinical attachment loss), inflammatory parameters and AS activity scores (BASDAI, ASDAS-CRP). More than half of AS presented with impaired periodontal health at baseline (mild to moderate PD) meaning increased sites with dental plaque, abnormal bleeding, increased periodontal pocket depth and clinical attachment loss. Significant positive correlation between presence and severity of PD, AS activity and systemic inflammation (CRP) was reported at baseline (p<0.05). A final analysis performed at 24 weeks revealed significant improvement in periodontal status, inflammatory parameters and AS activity, suggesting efficacy of TNF inhibitors directed not only against systemic, but also on local (articular, periodontal) inflammation (p<0.05). Patients with AS are at risk to develop periodontal disease, particularly those with high levels of systemic inflammation. Benefits of anti-TNFα therapy in the particular settings of AS patient and concomitant periodontal disease should be validated through further studies in larger cohorts.