Aims: To analyse the level of evidence (LOE) of clinical studies in the field of periodontology, and to investigate whether LOE is a predictor of scientific impact and social impact. Materials and Methods: Clinical studies published in five leading periodontal journals during 2015-2019 were identified. The LOE of included studies were assessed with a modified LOE classification system based on Oxford 2009 LOE, Oxford 2011 LOE and GRADE guidelines. Citation counts were harvested from Web of Science and Scopus. Altmetric Attention Scores (AAS) were obtained from Altmetric Explorer. Multivariable generalized estimation equation (GEE) analyses were used to investigate association between LOE and citation count, as well as between LOE and AAS. Results: Among 768 studies included, the proportion of level-1, level-2, level-3 and level-4 was 10.4%, 44.8%, 13.7% and 31.1%, respectively. In the multivariable GEE analyses, high LOE was a significant predictor of higher average citation count (p = .010) and higher AAS (p < .001). Conclusion: The LOE of clinical studies in the periodontal field is relatively high in general, although it varies significantly in different journals. Studies with high LOE tend to have greater scientific impact and social impact than low LOE studies.