Summary

Pulp chamber and root perforations may occur due to pathological processes or treatment consequences. Such perforations are severe complications and are associated with dramatically compromised endodontic treatment outcomes, especially when bacterial infection is allowed to establish. Various dental materials have been proposed over the years for perforation repair with varying degrees of success. The use of bioactive materials, such as mineral trioxide aggregate (MTA) and other calcium-silicate cements, promotes a favourable environment for regeneration and has been used successfully for perforation repair. This is in contrast to materials used previously that often led to unpredictable outcomes. With the increasing range of new bioactive endodontic materials available, the number of potential materials being used for repair of root perforations is growing. Though promising to date, there is little evidence to support the use of most of these new materials. Based on the currently available literature, the guidelines for perforation repair and treatment options need to be re-evaluated and the parameters for the use of MTA and other bioactive materials need to be optimised.

19.1 Introduction

Root perforations may arise pathologically, i.e. by resorptive processes or by caries, or may occur iatrogenically as a complication during or after root canal treatment [1] (Figures 19.1–19.8). The American Association of Endodontists (AAE) Glossary of Endodontic Terms defines perforations as mechanical or pathological communications between the root canal system and the external tooth surface [2]. The subsequent injury to the periodontium results in the development of inflammation, destruction of periodontal fibres, bone resorption, formation of granulomatous tissue, proliferation of epithelium, and the development of a periodontal pocket [3–6]. Root perforations are significant complications during root canal treatment; if not detected and properly treated, the breakdown of the periodontium may ultimately lead to loss of the tooth. An outcome study on root canal retreatment demonstrated that one of the factors significantly affecting the success rate of root canal retreatment was the presence of a preoperative perforation [7]. The incidence of perforations is quoted in the literature as being between 0.7 and 10% [8–11]. The percentage of teeth extracted due to endodontic failure with perforations is described as 2.9% to 4.2% [11, 12]. When analyzing the success rates of root canal retreatment procedures, perforations were present in 7 to 12% of primary root canal treatments [7, 13, 14].

19.2 Occurrence and Diagnosis of Perforations During Root Canal Treatment

This section provides an overview of the occurrence and diagnosis of root perforations. Root perforations may occur in any part of the root and can be divided according to the time a perforation occurs in relation to root canal treatment:

• Preoperative, typically pathologically, e.g. resorption or caries,
• Intra-operative procedural accidents, e.g. during access cavity preparation or canal instrumentation, or
• Postoperative procedural errors, e.g. during preparation of a post space.

According to Kvinnsland et al. [15], 53% of iatrogenic perforations occur during insertion of posts (prosthodontic treatment); the remaining 47% occur during routine root canal treatment. In 74.5% of cases, the complications occurred in the maxilla and the remaining 25.5% occurred in the mandibular arch. In order to prevent complications during root canal treatment, a complete understanding of the location and dimensions of the pulp chamber as well as the anatomical variations of the specific tooth and its canal system is essential. Kvinnsland et al. [15] reported that in maxillary anterior teeth, perforations were always located on the labial aspect of roots because the operator usually underestimates the palatal root inclination in the maxilla. In multirooted teeth, furcal perforations can occur when removing dentine from the chamber floor while searching for canal orifices [5]. The crowns of many teeth are frequently perforated when anatomical variations are not anticipated during access preparation as a result of misalignment of the bur with the long axis of the tooth [16]. Careful examination of radiographic views is important to evaluate the shape and depth of the pulp chamber and width of the furcation floor [6]. Significant crown-root angulations, calcifications of the pulp chamber and orifices, anatomical variations, misidentification of canals, and excessive removal of coronal dentine are often the reason for perforations in the coronal part of the tooth. Attempts to locate calcified orifices or excessive flaring of the cervical portion of curved roots in molars can cause lateral root perforations in the root canal [17]. Perforations caused by overzealous instrumentation occur mostly in the coronal or middle aspect of the root, are usually ovoid in shape, and are termed strip perforations. Excessive use of Gates Glidden burs or overzealous enlargement along the inner wall of curved canals can result in these procedural accidents. Perforations in the apical area of roots result mainly from a failure to properly clean and shape the canal and are often initiated by blockages and ledges that cause endodontic instruments to deviate from the canal and gouge the dentine eventually creating a false pathway [18].

Post-space preparation may result in a perforation due to over-enlargement or misdirected angulations. It has been often reported that the best way to manage perforations is to prevent them [16]; however, it is imperative to diagnose and treat a perforation if one has occurred.

19.3 Diagnosis of Perforations

The diagnosis of the presence and localisation of a perforation, as well as the determination of a treatment plan, can be challenging. Because the time lapsed between the creation of the perforation and its repair is critical to the prognosis for the tooth, early and accurate determination of the presence of a perforation is of paramount importance [6, 19, 20]. The diagnosis should be confirmed by clinical observations including aetiological aspects and radiographic findings. The first clinical appearance of a perforation is frequently associated with profuse bleeding from the defect within the chamber or canal [21, 22]. If anaesthesia is less than adequate, the patient may experience sudden pain when the perforation occurs. Indirect assessment of bleeding using paper points has been demonstrated to be helpful to identify smaller perforations or strip perforations within the canal. The canals should be cleaned as well as possible and dried. A freshly inserted paper point that has blood on the lateral aspect indicates a strip perforation. Repeated insertion of paper points demonstrating blood on their tips can indicate apical perforations. The use of magnification (i.e. operating microscope) has gained increased popularity in dental practice as it provides better vision, facilitating most endodontic procedures. Better visualisation and enhanced magnification and illumination enable easier and clearer diagnosis. Minute perforations can be easily missed, compromising the treatment outcome. Using an operating microscope during treatment is considered an important factor when repairing a perforation site, and high success rates with the use of MTA can be attributed to that combination [23, 24].

Another way to diagnose a perforation is to use an electronic apex locator. Normally used to determine working length, an electronic apex locator connected to a file and inserted into the perforation is a reliable tool to detect and confirm the perforation [25, 26]. It can help to locate the perforation, which might not be visible on two-dimensional radiographs periapical radiographs [27]. However, it must be appreciated that the contents of the canal may have an impact on the accuracy of apex locators, e.g. the type of irrigant. Altunbas et al. [27] obtained most accurate measurements in dry conditions. Among irrigation solutions, EDTA was associated with the most accurate results; sodium hypochlorite (NaOCl) was least accurate. On the contrary, another study reported excellent results using several apex locators with 2.5% NaOCl [28]. It has to be kept in mind that the studies referred to are laboratory-based and may not reflect the exact clinical conditions.

Angulated radiographic views are also essential for accurate diagnosis. However, the radiographical detection of root perforations, especially on the labial/buccal or lingual/palatal root surfaces, is often impractical because the image of the perforation is superimposed on intact root structure. Three-dimensional information acquired from cone-beam computed tomography (CBCT) scans can provide additional and more conclusive information [29] (Figures 19.9–19.17). CBCT imaging allows more accurate identification of perforations compared with radiographs [30–32]. In general, images with small field of view (FOV) are recommended for detection and treatment planning of perforations [30, 31, 33]. A small FOV scan reduces the volume of exposed tissue and, therefore, the effective radiation dose. It also has the benefit of reducing scatter, which improves image quality [34]. Although CBCT imaging can provide 3D visualisation of the perforation, scatter and beam hardening caused by high-density neighbouring structures or materials can affect the quality and diagnostic accuracy of CBCT images. Crowns, bridges, implants, restorations, root filling materials, and intracanal posts with higher density can create streak artifacts and distort the area of interest. This can mimic endodontic complications, hide existing ones, or induce false interpretation by simulating loss of tooth structures [30, 35–37] which can limit the effectiveness of CBCT imaging. Bueno et al. recommended a map-reading strategy, focusing on the involved tooth and obtaining scans in different planes (sagittal, coronal, and axial) in an attempt to minimise the possible beam hardening effect produced by higher density materials/stuctures [37]. Changing the contrast mode in the digital software can additionally help to reduce this problem.

The furcation area is often difficult to examine radiographically as restorative materials and crowns can either cover and hide the perforations or make a diagnosis difficult by producing artefacts, making proper evaluation impossible [33]. Furcation perforations especially when magnification is used, can often be diagnosed clinically not necessitating radiographic determination. Strip perforations can often be challenging to detect radiograhically, especially using periapical radiographs; indeed, even CBCT scans are sometimes unable to detect these perforations reliably [31] due to artefacts from root filling materials overlapping the area of interest. Information about the potential presence of a perforation can be given by the resulting bony defect of an infected perforation site, which is sometimes visible on two-dimensional radiographs; however, for detecting bony defects, using a CBCT scan is more sensitive, and they can usually be clearly identified.

In all perforations, it is essential to assess the periodontal status of the tooth in question as cervical and occasionally mid-root perforations are associated with epithelial downgrowth and subsequent periodontal defects, which will compromise the prognosis [3, 38, 39].

19.4 Classification of Perforations and Factors Affecting Prognosis

The aim of perforation management is to maintain healthy periodontal tissues adjacent to the perforation without persistent inflammation or loss of periodontal attachment. In the case of established periodontal tissue breakdown, the aim is to re-establish tissue attachment [40, 41]. Thus, successful perforation repair depends on the ability to seal the perforation and to re-establish a healthy periodontal ligament [3]. In the past, attempts to repair perforations exclusively with an orthograde technique were unpredictable [15]. Materials used to repair root perforations were associated with the formation of a fibrous connective tissue capsule in contact with the adjacent bone. The formation of a periodontal defect has been a common finding associated with the majority of materials used previously [38].

Kvinnsland et al. [15] reported 56% success in the primary treatment of perforations. Their conclusion was that the major problem with a nonsurgical approach was the inability to predictably seal the canal and the perforation defect without extruding considerable amounts of repair material through the perforation and into adjacent periodontal structures. They also found a relatively poor prognosis for perforations in the cervical portion of roots and attributed this to the loss of the epithelial attachment resulting in the formation of a permanent periodontal defect. This has been confirmed in experimental studies of the treatment of furcal perforations, which have invariably produced disappointing results [3, 22, 42–44].

In general, investigators have agreed that the prognosis for root perforations in the apical and middle third of the root is better than for those in the cervical third of the root or of the pulp chamber floor [41]. The prognosis of teeth with root perforations depends on the severity of the initial damage to the periodontal tissues, the size of the perforation, the location of the perforation in relation to the gingival sulcus, the time lapse between injury and repair, the adequacy of the perforation seal, the presence of microorganisms at the perforation site, and the biocompatibility of the material used to repair the perforation [42–49]. In the past, many materials were advocated for perforation repair; however, none provided a favourable environment for re-establishing the normal tissue architecture and predictable healing after treatment. The inadequacy of these materials can be attributed to their inability to seal the communication between the oral cavity and the underlying tissues, or their lack of biocompatibility. A characteristic that differentiates MTA and similar cements from other materials is their ability to promote regeneration of cementum, thus facilitating the regeneration of the periodontal apparatus [5, 41] (Figure 19.18). Until the advent of MTA, repair materials were unable to stimulate this regenerative process [38]. Histological examination of the periradicular tissues after root-end filling with MTA in dogs has shown that not only is there a re-establishment of normal periodontium, but there is also build-up of cementum over the material [41, 50]. Lack of adverse effects after extrusion of MTA into the furcation in both cases indicates biocompatibility [5, 41]. Several studies have concluded that MTA establishes an effective seal of root perforations [51–54] and can be considered as a potential repair material that enhances the prognosis of perforated teeth that would otherwise be compromised [38, 41]. According to some data, the prognosis of perforation repair is enhanced when MTA is used.

To determine an ideal treatment strategy, Fuss and Trope introduced a classification system based on the factors affecting the prognosis of perforations and their treatment [9], as mentioned below.

19.4.1 Time of Repair

As prevention or treatment of bacterial infection of the perforation site dictates the success of the repair, the time elapsed between perforation and appropriate treatment is extremely important. Immediate repair under aseptic conditions before bacterial contamination and breakdown of the surrounding tissues achieves better results than delayed repair, which is associated with a less favourable prognosis. Several histological studies with experimentally induced perforations demonstrated more favourable healing when perforations were sealed immediately [3, 4, 46]. Pitt Ford et al. demonstrated that even with the use of MTA in the group with delayed repair, more specimens were associated with inflammation, which appeared to be linked to the presence of infection [41]. Time of treatment seems to be more critical as the perforation size increases [55]. When examining infected, previously untreated perforations, epithelial proliferation can often be observed. Successful treatment of infected perforations can be attributed to removal of contaminants as well as cleansing of the pulp chamber, perforation, and wound site before repairing under aseptic conditions [15, 41, 45].

19.4.2 Size of Perforation

The potential for successful reattachment of the periodontal ligament is dependent on the surface area that must be repaired. In small perforations, mechanical damage to tissue is minimal and sealing is improved in comparison to large perforations. Although often mentioned, it has been reported that there is no substantive evidence that perforation size affected prognosis [41]. Some case reports have demonstrated healing and promising results in large perforations treated with MTA [5], so the effects of perforation size should to be re-evaluated. Moreover, most articles refer to problems with the coronal seal in situations with larger defects and used materials other than MTA, so the potential to achieve regeneration would be increased by using MTA in these cases.

19.4.3 Location of Perforation

The location of a perforation is probably the most important factor affecting treatment prognosis [9]. In general, investigators have agreed that the prognosis for root perforations in the apical and middle third of the root is better than those in the cervical third of the root or in the floor of the pulp chamber [45]. Fuss and Trope [9] emphasised the importance of the ‘critical zone’ at the crestal bone level and the epithelial attachment. Perforations above that zone have a good prognosis because they can be sealed properly using adhesive techniques or be covered by final restorations, without periodontal involvement. In some cases, orthodontic eruption of the tooth or surgical crown lengthening can move the perforation out of the critical zone. Crestal root perforations are sensitive to epithelial migration and rapid periodontal breakdown, which can reduce the chance of regeneration and lower success rates, making treatment more complex and less predictable. Perforations apical to the critical zone have a good prognosis, assuming that root canal treatment can be performed adequately and the perforation sealed.

Although there are claims for a good prognosis in perforations apical to the critical zone, the difficulties concerning accessibility increase with perforations deep within the canal. In these cases, predictable repair may be challenging or provide a compromised result, necessitating a surgical approach. Perforations can occur circumferentially on the buccal, lingual, mesial, or distal aspects of roots. The location of the defect is not as important when nonsurgical treatment is selected but is critical in a surgical approach [18].

More recent studies indicate that these historical prognostic factors for teeth after perforation repair are no longer as important as they were before the introduction of MTA [56]. To date, there is no clear agreement on the significant prognostic factors. This might be due to the fact that perforation repair does not occur frequently, which makes it a difficult topic to study clinically, and often results in small sample sizes, limiting statistical power and compromising the conclusions. It should be noted that the variety of different clinical situations makes comparisons and standardisation of studies difficult. In a systematic review and meta-analysis on treatment outcome of repaired root perforation involving studies before the introduction of MTA as well as following its introduction, two factors significantly affected the success rate of nonsurgical repairs [23]:

1. Maxillary teeth had a significantly greater chance to heal when compared with their mandibular counterparts. This might be explained in part by the rich vascular network supplying the maxilla that may help to promote healing [23]. In addition, some radiolucent lesions might have escaped detection because of the presence of overlapping radiodense structures in the maxilla.
2. Clinical cases with no preoperative radiolucent area adjacent to the perforation site also had a significantly higher success rate than those with a radiolucency.

As mentioned previously, most authors agree that the size of the perforation does not influence the treatment success [39, 56, 57].

Torabinejad et al. summarised in an updated overview on MTA and other bioactive cements confounding factors that may affect the outcome of perforation repair [24]:

• Experience of the practitioner who performed the perforation repair treatment [56];
• Negative influence on placing a post following root canal treatment [56];
• Presence of preoperative lesions and communication between the perforation site and oral cavity [39, 58];
• The location of the perforation and the quality of the final restoration had a significant influence on the outcome of perforation repair [57], and most failed cases had a close proximity to the osseus crest;
• The site of perforation (mid‐root and apical) and perforation size larger than 3 mm were reported as significant predictors for the recurrence of progressive inflammation following initial healing [58]; and
• Gender of the patients (female) [57, 58].

These factors should be taken into careful consideration at the time of treatment planning, although the usual prognostic factors associated with traditional materials might not apply when MTA is used [24].

The decision to treat a perforation also depends on the periodontal condition of the defect. The presence of periodontal involvement frequently requires additional procedures for management and reduces the prognosis for a successful outcome. If a defect is not associated with increased probing depths and loss of attachment, then the treatment method of choice is usually nonsurgical perforation repair, which should be done as soon as possible because timing is essential for a successful long-term prognosis. However, if a defect is associated with increased probing depth, the loss of attachment and the risk of epithelial downgrowth decrease the chances of regeneration drastically. When pockets have already formed, any conservative treatment is compromised [41]. These defects usually require nonsurgical periodontal management or may even need surgical intervention. Surgical treatment of perforations can often lead to the loss of periodontal attachment, chronic inflammation, and furcal pocket formation [48]. Based on the probability for regeneration, the treatment options (namely surgical, nonsurgical, or a combination of both) require careful consideration. The experience of the operator seems also to have an impact on treatment outcome and most clinical studies mention that the treament was performed by endodontists or dentists with special training being educated for treating such severe complications as perforations. In addition, clinical procedures were aided by operating microscopes [23, 56]. The increased willingness of patients to keep their teeth in combination with improvements in technology necessitates a re-evaluation of the indications to treat and retain perforated teeth. When teeth are of strategic value and treatment prognosis is adequate, perforation repair is clearly indicated.

19.4.4 MTA as a Perforation Repair Material

Various materials have been used to repair root perforations. The requirements for an ideal repair material have been described by several authors [19, 59] (Table 19.1).

Traditionally, the most commonly used repair materials have been amalgam, zinc oxide eugenol cement, calcium hydroxide, gutta-percha, glass ionomer cement, IRM (Dentsply Sirona, York, PA, USA), composite resin, and SuperEBA (Keystone Industries, Gibbstown, NJ, USA). More recently, mineral trioxide aggregate (MTA and similar materials have been advocated.

MTA was initially introduced as a root-end filling material for surgical endodontic procedures [50, 60]. Since then, its clinical applications have broadened to include perforation repair, pulp capping, pulpotomy, and apexification. During these procedures, the materials usually come into contact with the underlying tissues. The original gray and white formulations of MTA were reported to work equally well [20, 61].

The bond strength of most dental materials is significantly reduced by moisture contam- ination from the tissue, whereas MTA requires the presence of moisture for setting. Therefore, set MTA can acquire its optimal strength and produce excellent sealability in the presence of tissue fluids [51]. Due to its excellent biocompatibility and osteoconduction property, MTA is able to allow the growth of cementoblasts with deposition of cementum over its surface [62, 63]. On the other hand, the formation of fibrous tissues encapsulating or walling-off other materials such as resin composite, intermediate restorative material, or zinc ethoxybenzoic acid cement was a commonplace finding [64]; often there may be varying degrees of chronic inflammation in the periodontal tissue adjacent to these materials [64].

Siew et al. concluded that nonsurgical repair using MTA resulted in a higher success rate when compared with other materials. With an overall success rate for perforation repair of about 81% when using MTA, saving the tooth nonsurgically with such a method is worthwhile [23]. Two surveys amongst active Diplomates of the American Board of Endodontics in the USA and Australian Society of Endodontology reported that MTA was the most popular material for perforation repair [24, 65, 66].

With increasing and promising research on the use of bioceramic cements [62], a general group of materials to which MTA also belongs, the choice of material for repairing root perforation is growing. (For more detailed information on MTA and bioactive cements, see chapter 14 on calcium silicate-based endodontic cements.)

19.4.5 Alternative Materials for Perforation Repair in Specific Indications

An attempt has been made to take advantage of the favourable biological properties of MTA in periodontal regenerative therapy. However, freshly mixed MTA is usually washed out whenever there is a communication between the oral cavity and MTA, which has limited its applications in periodontal procedures. In order to circumvent this problem, MTA has been used in combination with a bone graft material to repair external resorption and osseous defects [67]. This approach was successful in reducing the pocket depth without causing clinical symptoms. An alternative could be the use of other bioactive materials with reduced setting time.

Another material, resin-modified glass ionomers such as Geristore (DenMat, Santa Maria, CA, USA), may be used for perforation repair, specifically when there is communication between the perforation site and the oral cavity. Geristore is a resin ionomer that was introduced to treat perforations and resorptive defects. Several case studies using Geristore in perforation sites have reported promising results. Breault et al. [68] reported sustained tissue health and minimal probing depths at the surgical site when a root perforation was repaired with Geristore. There have only been a few studies examining the biocompatibility of Geristore. Al-Sabek et al. [69] reported that human gingival fibroblasts attached and spread well on Geristore, which demonstrates that Geristore might be less toxic than IRM (Sybron Kerr) and Ketac-Fil (Espe, Seefeld, Germany). Similar results were published by Gupta et al. confirming that Geristore has enhanced biologic behavior in contact with human periodontal ligament cells and superior biocompatibility in comparison with MTA and glass ionomer cement (GIC) [70]. On the other hand, compared with MTA and IRM in endodontic root-end fillings in beagle dogs, Geristore was no different radiographically when compared with the other materials, and had the least favourable healing in the histologic evaluation [71]. Geristore might be an interesting alternative in the aesthetic zone and especially subgingival in the crestal region, when MTA or its derivates do not promote ideal outcomes (Figure 19.19–19.25) or aesthetic demands.