In addition to its effectiveness in resolving apical periodontitis, regenerative endodontic treatment (RET) has advantages of inducing root maturation and restoring innate immunity or sensory function through revascularization. However, its adoption in mature teeth in adults has been scarce due to limited stem cell sources and constricted apical size. In recent years, there have been instances of studies performing RET in mature permanent teeth. The present case report describes the treatment of apical periodontitis in a previously treated mature permanent tooth using RET with a 3-year follow up. In the present case, a 34-year-old female patient presented with previously treated maxillary lateral incisor with a large radiolucency. After removal of previous gutta percha within the root canal, bleeding was induced by passing hand file beyond root apex and calcium hydroxide was applied over the blood clot. During the 9-month follow-up, a reduction in periapical radiolucency was observed. Subsequently, after removing calcium hydroxide, apical bleeding was induced again and mineral trioxide silicate was placed up to 3mm beneath cemento-enamel junction, above the blood clot. The tooth was later restored with glass-ionomer cement and composite resin. After 3 years, the tooth was asymptomatic and radiographic evaluations showed complete resolution of periapical radiolucency with presence of normal lamina dura and periodontal ligament space. In conclusion, modified RET with long-term calcium hydroxide application is a potentially viable treatment option for previously treated mature permanent teeth with apical periodontitis. However, further clinical studies with larger number of cases are recommended to verify its effect.

Ⅰ. INTRODUCTION
Ⅱ. Case Report
Ⅲ. Discussion
REFERENCES

• 이명진(서울대학교 치과병원 치과보존과) | ng-Jin Lee (Department of Conservative Dentistry, School of Dentistry, Seoul National University, Seoul 54896, Republic of Korea) Corresponding author