Sir,We read with great interest the article by Shah and Logani[1] regarding the formation of a biological seal after revascularization procedures. Unfortunately, the formation of so-called “biological seal” has not been demonstrated in the entire manuscript. There is no evidence of formation of seal in any of the presented case reports. The results shown in the case reports are not surprising. Any acute case with apical abscess or large periapical radiolucency will respond to cleaning/disinfection of the root canal system. Yet, the procedure described in the manuscript does not imply that a complete disinfection was even aimed at. The discussion clearly states that “apical canal widening to 300–500 μm is required to thoroughly cleanse the apical portion of the canal.” But the next line states that “apical foramen widening was done with gradually increasing number of files till no #25 or #30.” An apical widening up to size 25 or 30 (250–300 μm) may not be sufficient for thorough cleansing of the canal (as compared with 300–500 μm).Figure 1 Shows the clinical and radiographic image of a 53-year-old man treated with revascularization procedures. On closer inspection of the radiographs, one can easily figure out that the position of third molar is dubious. The 6-month follow-up radiograph shows a coronal movement of third molar as compared with the initial radiograph (surprising in a 53-year-old patient), but the 3-year follow-up shows a remarkable down movement of the third molar!In the entire article, we were unable to find any kind of “seal.” It is very well documented that there is formation of connective tissue or periodontal tissue into the pulp space when a blood clot scaffold is available.[23] This new tissue growth only lays down cellular and acellular cementum. The apical part of the root may become a little stronger because of cementum buildup, but the coronal half will be as weak as before. The ethics of not obturating the canal and whole point of a “sealbio” crashes in the last line of the discussion when the authors state that “further well-planned experimental animal studies can provide information on the type of cells involved and the tissue deposited.” The authors are still not sure of what type of tissue has been deposited in the “sealbio” and recommend an animal study to verify the results of the study that has already been done in human beings. Should not the treatment modality be first checked in animals and, if found successful, only then done in humanpatients? Although in an experimental study on dogs it has been found that after the revascularization protocol, the final product in the root canal space has little similarity with the pulp tissue and looks like a mixture of cementum and periodontal ligament.