Introduction: Calcification of mandibular second premolar teeth begin in ages of 3-3.5. However, it was revealed in the literature that the greatest

variations in the odontogenesis process are observed in the mandibular second premolars, excluding the third molars.

Case Report(s): Seven-year-old male patient applied at our clinic with toothache on mandibular left region. During the clinical examination, deep

carious lesion on the tooth number 75 and localized swelling. Radiographical examination revealed radiolucency in the periradicular and interra-

dicular areas and lead to suspected late mineralization in the second premolar tooth.

Upon this unusual situation, regenerative treatment protocol was applied on tooth number 75 with flexible treatment option and mineralization

process of the second premolar tooth was observed.

The calcification process was clearly observed at the sixth month follow and crypt formation was observed at the ninth and twelfth months at the

mandibular second premolar tooth. The clinical and radiological success was achieved in tooth number 75 at the 12-month follow up.

Conclusions: This case report targeted to ensure of the arch integrity with long-term survival of the primary tooth and to preserve the physiological

resorption process. It is considered that such targets can be achieved with regenerative endodontic treatment. However, with the awareness of the

possible negative effects of the regenerative treatment protocol on permanent tooth germ, which is the most major discussion topic, it is aimed to

monitor the case until the permanent tooth eruption period and to share information that would contribute to the literature in the following years

Keywords: agenesis, primary teeth, regenerative endodontic treatment