The following table is a classification of root perforations which is based on the key prognostic factors that affects long-term outcome, namely, size and location of perforation and timeline from diagnosis to repair (Table 12.1).

Early recognition of a root perforation is crucial to the long-term prognosis. Sudden bleeding or pain during instrumentation of the root canals or post space preparation in the teeth is an important sign that should alert the clinician to the possibility of an iatrogenic error resulting in a perforation. The presence of blood on paper points, particularly on the coronal or middle 1/3, may also be indicative of such a mishap. One must be aware that over-instrumentation beyond the apical foramina or remaining pulp tissue remnants within the canal system can also result in evidence of blood on a paper points.

A more reliable method is to use an electronic apex locator (EAL). The working length should always be verified with an EAL, and a premature reading significantly shorter than the estimated length in combination with profuse bleeding is often a good indicator of the presence of a perforation.

The diagnostic value of a radiograph can be useful when a file is placed to this level often demonstrating that the file is misplaced beyond the confines of the canal into the periodontal tissues. If the perforation is either buccal or lingual, then the diagnostic yield of the radiograph is limited.

The use of a dental operating microscope is another effective tool in the detection of perforations and management thereafter. High magnification combined with illumination will often allow direct unimpeded visualization of the perforation within the straight portion of the root canal.

If a perforation has been present for some time and there has been communication with the perforation site and attachment level at crestal bone level, then a narrow probing profile may be detected in this area. The ingress of bacteria within this communication will result in further apical migration of epithelial attachment resulting in a narrow pocket depth.

A well-designed and executed access cavity is an essential objective whereby straight-line access is gained to the root canal system without overzealous tooth removal thereby preserving the overall integrity of the tooth (Fig. 12.2).

Due consideration should be given to the orientation of the tooth in question and in particular any deviation of the crown and root along the long axis of the tooth. This can typically occur in cases where a crown has been placed or where the tooth is dilacerated, rotated or imbricated (Fig. 12.3).

Furcation perforations occurring typically in the floor of the posterior molar teeth usually occur during access preparation when due care has not been given to the level of the furcation relative to the crown. A preoperative bitewing radiograph will give the clinician an excellent idea as to the approximate depth to the pulp chamber. Digital radiographic systems allow for manipulation of the image taken and measurements to be made. Provided the bitewing is a parallel image with minimal distortion, then the measurement should be fairly accurate.

Canal identification can be problematic in those cases where obvious calcification has occurred in the coronal pulp chamber resulting in iatrogenic perforations.

Chronic insults whereby reparative dentine is laid down will result in sclerosed canals and diminished pulp chambers. Anatomical features pertinent to the tooth in question as well as preoperative radiographs will alert the clinician to the expected number of root canals and their likely position. Once an initial access preparation has been made, the individual canals can be located usually following the ‘road map’ of root canal anatomy which is darker compared to the whiter axial walls. Pulp chamber calcifications can often be observed using a dental operating microscope and illumination highlighting the colour difference between surrounding anatomies. Ultrasonic tips are often useful when removing small amount of dentine in search of canal orifices. No burs should be used to gouge the floor of the pulp chamber and risk perforation.

The advent of nickel titanium rotary instrumentation techniques means the ideal canal shape should be a continuously tapered preparation, maintaining canal anatomy and keeping the apical foramen as small as possible. The clinician should bear in mind the danger zones in relation to root canal anatomy and care during preparation procedures to ensure no strip perforation occurs due to overzealous instrumentation (Fig. 12.4).

Incautious preparations without taking into account the original anatomy and overzealous use of either rotary instruments or large tapered Gates Glidden burs can result in apical or crestal strip perforations. Large inflexible instruments used in curvatures can also result in zipping of the canal anatomy leading to perforations. A glide path should always be used prior to negotiating any canal curvature whether straight or curved (Fig. 12.5).

Post space preparation should be carried out ideally at time of obturation. Clinically 4–5 mm of gutta-percha should remain apical to the post space to maintain an apical seal. A safe preparation should be taken under the guidance of the dental operating microscope to avoid risk of perforation due to deviation of post bur from the long axis of the root. The canal anatomy should be assessed for any changes in curvature along the root length, which would risk perforation.

A prerequisite for non-surgical management is that the perforation site can be visualized using the dental operating microscope. In those instances where a strip perforation has been created, then the canal space beyond the perforation must be obturated prior to repair of the perforation. The first step in order to visualize the perforation site is to stem any bleeding which may be present. Local anaesthetic, sodium hypochlorite or triamcinolone acid soaked on a cotton wool pledget and pressed against the site of perforation should be sufficient to control haemorrhage (Fig. 12.6).

To avoid extrusion of filling material into the periodontal tissues and risk of further inflammation, delayed healing or need for a surgical procedure for debridement, an internal modified matrix technique can be used. Sterile inorganic bovine bone (ABB; Bio-Oss, Geistlich AG, Wolhusen, Switzerland) is packed into the perforation defect. Once the matrix is in place, the artificial floor barrier can be placed using either glass ionomer cement, MTA or Biodentine without the risk of pushing the material into the surrounding bone and supporting tissues.

If MTA has been used, then the access cavity is sealed with a temporary moist cotton wool pledget to ensure that the site has sealed and the MTA has set (Fig. 12.7).