## 5 Aapical Plug in Teeth with Periapical Lesions  
### Aypical Plug in Teeth with Apical Resorption and \"Open Apex\"  
The major challenge in endodontic treatment is to achieve complete debridement, canal disinfection, and the sealing of the root canal space in teeth with open apices and teeth with apical resorption resembling an open apex (Figure 2A-E) [64]. An open apex is a clinical situation that is a result of the iatrogenic enlargement of apical constriction with both hand and rotary files. Years ago, we treated these teeth with immature apical formation by generating mineralized formations at the apical zone as a barrier via the repeated placement of calcium hydroxide paste over many months. Incomplete root development often arises secondary to pulpal necrosis as a result of caries or trauma.  
Nowadays, such clinical situations are treated with an apical plug with MTA and an apical barrier made from collagen [68]. Chronic lesions alter the adjacent bone structure, periodontal ligaments, and cementum and dentine in the periapical region. In the majority of instances, the apical physiological constriction is either absent or enlarged. In the absence of a restriction, it is difficult to attain satisfactory treatment outcomes. MTA was used for an apical 5 mm plug to prevent sealer overfilling when the root canal was definitively obturated. MTA has been demonstrated to be a suitable material for apical obturation in cases of an \"open apex\" in teeth with embryonic root formation, apical root resorption, and iatrogenic enlargement, as it avoids apical surgical procedures with a similar prognosis. Apical periodontitis is a destructive process in the bone around the root apex that also affects the cement and dentin. The radiographic image replicates the apical image of immature teeth, which are characterized by large, exposed apices and thin, fracture-prone dentinal  
Figure 2: (**A**) Preoperative X-ray on tooth #21, which is planned for primary endodontic treatment— PAIS; (**B**) CBCT image to control the condition of the corticalis. When the periapical bone lesion is closed, orthograde treatment is recommended; (**C**) Postoperative X-ray—the canal is filled with an apical barrier of nanometer-sized biocearamics (\(\beta\)-TCP), which stops the bleeding and realizes drying at the apical third. Then, the whole canal is filled with a biocearamic sealer and injectable thermoplasticized gutta-percha. The apical width is ISO #80; (**D**) Control X-ray after 6 months; (**E**) after 1 year—after repair at the periapical bone lesion, the old crown is replaced with an all-ceramic one; (**F**,**G**) magnifications at the apical zone—from PAI5 to PAI1 (with the permission of [PERSON]).  
walls. The apical width is measured using an instrument between #80 and #140. The presence of a periapical lesion may also result in foraminal and peri-foraminal resorption of the root apex.  
The clinical case presents the placement of an MTA apical plug into the distal root canal, with the apical foramen's width being ISO #60. The patient's informed consent was obtained before the endodontic therapy. From the preoperative radiograph, a periapical index of PAII was determined with suspicion of apical resorption, and the tooth was planned for retreatment. The control radiograph after separating instrument (_lentulo_) removal displays the complete elimination of the fragment. The observation of root canal filling from the postoperative X-ray shows that the mesial canals were filled with a bioceramic sealer (_TotalFill_, _FKG_, _Switzerland_) and gutta-percha, and the apical 5 mm of the distal canal was obturated with MTA due to the width of the foramen (ISO #60). The apical barrier formed from collagen is applied before the MTA plug. The control X-ray and follow-ups after 1 month, 6 months, 1 year and 4 years demonstrate the successful endodontic outcome (Figure 3A-G).