PMC9355846_01
Intraoral examination showing bilateral peg-shaped lateral incisors
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F1
Intraoral examination revealed bilateral peg-shaped lateral incisors (Fig. 1). 
Periapical lesion associated with tooth #10 extending apically to the ipsilateral impacted canine. The configuration of the root canal corresponded to Oehlers type II DI.
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F2
On the diagnostic periapical radiograph, a periapical lesion was noticed, which was associated with tooth #10 extending apically to the ipsilateral impacted canine (Fig. 2).
CBCT revealed no perforation in the buccal or palatal cortical plates. There was no direct contact between the invagination and the periodontium
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F3
The associated periapical lesion extended to the crown of the impacted canine and had not perforated the buccal or palatal cortical plates (Fig. 3).
MTA apical plug placement (retroMTA)
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F4
Due to external resorption of the apical part of the root, RetroMTA (BioMTA, Deajon, Seoul, Korea) was placed as an apical plug to provide an adequate seal in the apical portion of the root canal up to the point of invagination defect and temporarily sealed (Fig. 4). 
(A) At 3-month follow up, substantial bone formation in the periapical lesion was observed and clinical examination of the patient revealed no signs or symptoms. (B) Backfilling by warm vertical condensation technique
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F5
In order to maintain the coronal seal during the orthodontic treatment, the MTA apical plug was backfilled using gutta-percha (Meta (Dentsply, Tulsa, OK, USA) with warm vertical compaction technique (Fig. 5).
(A) Six-month follow-up: complete bone formation in the periradicular area. (B) One-year follow-up: evident bone healing and no evidence of recurrence of the periapical lesion
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F6
Upon periapical radio-graphic evaluation after 6 months, complete bone formation was observed in the periradicular area (Fig. 6a). At the one-year follow-up, the patient was asymptomatic, and the periapical radiograph showed bone healing and no evidence of recurrence of the periapical lesion (Fig. 6b).