Serious accidental perforations during RCT were regrettably common in this large material of endodontic injuries. According to the PIC advisors, four of five perforations could have been avoided by following good clinical practice. The irreversible outcome of these perforations increases the gravity of the situation.
Many earlier reports emphasize the role of perforations as reasons for failure in RCT. However, comparisons with previous reports remain limited because of the wide variation in target groups and definitions of perforations and their outcome. We analysed cases with verified endodontic injuries and restricted perforations to those occurring during endodontic treatment. Further, we excluded resorptions, apical over-instrumentation, and perforations during preparation of the post space, a situation commonly associated with root canal perforations. A meta-analysis of repair of perforations in the root canal system summarized that 47% of perforations were ‘noted or created’ during endodontic treatment and 53% were due to prosthodontics .
The main strength of our study is the large nationwide data covering 8 years. Practically all serious injuries are claimed to PIC, in part due to the ease of doing so. Furthermore, dentists are willing to help the patient in making the claim since the goal of the process is not to determine guilt, but to pay compensation to the patient. Some minor cases may, however, be settled immediately in the dental office without further consequences.
Our document-based data comprise background information on both patients and operators. We could, thus, assess the occurrence of the serious accidental perforations among the verified endodontic injuries not only by type of tooth but also according to the patient’s and dentist’s backgrounds. We found dentists’ age, either young or old, to have an impact on the fatal outcome of perforations as extraction of the tooth. Young dentists have less endodontic experience/routine practices, whereas older dentists may have neglected their need for continuing education. Unfortunately, dentists’ level of endodontic knowledge and skills could not be assessed in this context.
Our data allowed us to relate the occurrence of serious accidental perforations to the number of endodontic patients in the entire population. Such data are available both in the private sector as open data  and in the public sector as sporadic publications , thus allowing us to relate injury cases to the numbers of endodontic patients in the entire country. Comparable aspects have, to our knowledge, not been reported earlier. Our results suggested that 0.023% of endodontic patients per year experienced accidental perforations in 2011–2013. However, this rate must be considered an underestimation of all accidental perforations as it describes serious incidents only. Further, we could not relate accidental perforations to the numbers of teeth that had undergone RCT per year, which can be taken as a limitation of the study. Further, due to the new techniques and materials available, many smaller perforations certainly are adequately repaired, thus avoiding any injury claim to the PIC. Unfortunately, no information of such incidents is available in patient-based documents or registers.
In our data, 70% of the teeth with accidental perforations ended up being extracted, 42% before and 28% after filling the root(s). This indicates the seriousness of the perforations. Teeth with perforation comprised 29% of all verified endodontic injuries (n = 970), and thus, tooth extractions were the outcome for some 20% of all endodontic injuries. A recent study of 1000 endodontically failed teeth, 28% of which were extracted, reported the reason for extraction to be prosthetic for 41% and perforation for only 3% . Their definition for failure included clinical, restorative, and radiographic problems; nevertheless, our estimated outcome rate of extractions following serious endodontic injuries is in line with their rate of extractions following endodontic failures.
In the long term, teeth with perforation often result in fatal problems and final failures. Our data of verified endodontic injuries proved a high rate of extractions following serious accidental perforations. A similar fate existed in the patient case we presented, as the perforated tooth ended up being extracted after two symptomless years. In line, a recent radiographic analysis of 1146 root canals in 618 endodontically treated teeth reported rather few perforations, but 91% of the perforation cases were with apical radiolucency  indicating unsuccessful outcome of the treatment.
Reports of accidental perforations highlight time, size, and location as important factors for prognosis of the incidence . Our data offer information about location only, half were in canals and half in the pulp chamber, but sizes of perforations remained unknown, which can be taken as a limitation of the study. We can, however, infer that the perforations were massive or otherwise serious since the majority of the cases resulted in tooth extraction. A further limitation is that these data cannot answer the question about the reasons leading to accidental perforations because the quality of the patient documents varied widely , and consequently, descriptions of the incidents or attempts to repair them varied from detailed to minor or none.
The vast majority of serious accidental perforations analysed here could have been avoided had the operator followed good clinical practice, as stated by the PIC advisors. Similar conclusions have been presented in many review articles and numerous case reports about accidental perforations during RCT. Dentists have at hand a lot of detailed instructions showing methods for adequate root canal preparation, step-by-step, and for avoidance of accidental perforation or file separation [22, 23].
When new preparation techniques have been introduced, their quality has soon been analysed also from the point of avoiding procedural errors. In 1999, an experiment compared automated root canal preparation with hand instrumentation in 45 extracted mandibular molars and concluded that the ‘manual instrumentation proved to be safe; no instrument fracture, perforation or loss of working length could be observed, whereas automated preparation resulted in one perforation and two cases of loss of working length’ . Opposite findings were recently reported from a university clinic comparing root canal treatments performed by students using manual preparation in 2002–2003, but rotary instrumentation in 2012–2013 . The authors concluded rotary root canal preparation being with fewer procedural errors than manual preparation.
The following questions arise: Has the development of new equipment been too rapid to allow necessary training? Are dentists ignoring the training needed before adopting new working methods? Or are dentists’ working schedules too tight to allow adequate time for performing RCTs? These aspects should be seriously discussed in every unit aiming to avoid serious perforation injuries during RCT.