The correlation between endodontic-periodontal lesion has been documented well by researches. Endodontic lesion originates from pulp, while periodontal lesion originates from periodontal tissues. Anatomically they are connected by apical foramen, lateral canal and accesories, as well as dentin tubules. The correlation appeared as the endodontic defect can be from periodontal lesion, or a periodontal defect is from a pulp tissue. Together they can emerge and form a combination lesion. Endodontic infections have been highly correlated with deeper periodontal pockets and furcation involvement in mandibular, the causal relationship between the two pathoses has not yet been established. This consensus supports the influence of degenerated or inflamed pulp that can happen on the periodintium; but not all researchers agree about the effect of periodontal disease on the pulp. Conclusion: The mechanism of endo-perio lesion need to taken care in order to have appropriate diagnostic so that the right therapy would be able to keep the teeth in the oral cavity.