Figure 2. Periapical radiographs and clinical photograph of the mandibular right second premolar with an open apex. (a) Preoperative periapical radiograph showing apical radiolucency with underdeveloped root; (b) Periapical radiograph after MTA filling showing limited blood clot space despite using collagen matrix; (c) Periapical radiograph at the 12 month follow-up showing resolution of the apical radiolucency without further root formation; (d) Clinical photograph at the 12 month follow-up showing slight grayish discoloration of the crown due to MTA filling.