Vertical root fractures and their management.

Vertical root fractures associated with endodontically treated teeth and less commonly in vital teeth represent one of the most difficult clinical problems to diagnose and treat. In as much as there are no specific symptoms, diagnosis can be difficult. Clinical detection of this condition by endodontists is becoming more frequent, where as it is rather underestimated by the general practitioners. Since, vertical root fractures almost exclusively involve endodontically treated teeth; it often becomes difficult to differentiate a tooth with this condition from an endodontically failed one or one with concomitant periodontal involvement. Also, a tooth diagnosed for vertical root fracture is usually extracted, though attempts to reunite fractured root have been done in various studies with varying success rates. Early detection of a fractured root and extraction of the tooth maintain the integrity of alveolar bone for placement of an implant. Cone beam computed tomography has been shown to be very accurate in this regard. This article focuses on the diagnostic and treatment strategies, and discusses about predisposing factors which can be useful in the prevention of vertical root fractures.

INTRODUCTION

According to the American Association of Endodontists, “A vertical root fracture is a longitudinally oriented fracture of the root that originates from the apex and propagates to the coronal part.”[1] According to the literature, vertical root fracture is the third most common reason for extraction of an endodontically treated tooth.[2] Vertical root fracture is an important threat to the tooth's prognosis during and after root canal treatment. The diagnosis of vertical root fracture can be problematic, and it often requires prediction rather than definitive identification. The clinical scenario of vertical root fracture may resemble that of a periodontal disease or of a failed root canal treatment. So it is important to differentially diagnose vertical root fracture from other similar clinical conditions. Radiographic diagnosis of vertical fracture of root is also difficult, as not all the classical radiographic signs of vertical root fracture may be present in every case. The accuracy of radiographic diagnosis also depends on the proper radiographic angulation, contrast, density and sensitivity of the clinician in interpreting the radiographic findings. There is need for the development of a diagnostic strategy depending on the patient's dental history, clinical signs and radiographic observations. CBCT has been used in recent studies with a high accuracy and sensitivity in detecting vertical root fracture.[345678910111213141516] Preserving a vertically fractured tooth helps improving function, esthetics and maintaining the integrity of the arch by preserving the alveolar bone height. Various attempts were made in the literature for the treatment of vertically fractured roots. But the long term prognosis of reunion of the fractured roots is questionable and requires further follow up. On the other hand, there are studies evidencing the role of various endodontic procedures, materials and post endodontic restorations in the etiopathogenesis of vertical root fracture. This review adds to the preventive measures which can be incorporated during routine clinical procedures.

MATERIALS AND METHODS

The search strategy spanning from a period of 1970s to 2012 was conducted using MEDLINE via PUBMED and the Cochrane databases using following search terms: ‘vertical root fracture’, ‘diagnosis of vertical root fracture’, ‘management of vertical root fracture’. A hand search was also carried out of the last two issues of the following major endodontic journals: Journal of Endodontics; International Endodontic Journal; Dental Traumatology; Australian Endodontic Journal. The process of cross referencing continued to get relevant articles.

A total of seventy seven articles were selected for the study, which included forty three in-vivo, and thirty four in-vitro studies. The in-vivo studies included case reports[7891011171819202122232425262728293031323334353637] clinical surveys[38394041] and review articles[119424344] and a histological study.[45] The titles and abstracts of all identified articles were screened to determine the relevance of each study with regards to the diagnosis, contributing factors and management of vertical root fracture. Full texts of selected articles were collected and analyzed. These articles were selected based on their evidence based information in establishing definite criteria for the diagnosis, role of predisposing etiological factors, based on studies with large sample and adequate follow up. Relevant information from each study, such as evaluation techniques, tooth involved, recall time and findings were summarized in Tables 1 and 2.

Table 1

Diagnosis of vertical root fractures by different evaluation techniques — A report of available studies

Table 2

List of available studies for the treatment of vertical root fractures

RESULTS

From the search strategy, thirty five studies were identified [Table 1] to determine different evaluation techniques for the diagnosis of vertical root fractures. In these studies, the diagnosis of vertical root fracture was made by careful evaluation of the clinical signs, symptoms, radiographic findings and CBCT. In [Table 2] the treatment strategies for vertical root fracture since from 1984 to 2012 have been summarized.

Clinical evidence of vertical root fractures

Mild pain is the only symptom in majority of cases of vertical root fracture.[17] Spontaneous dull pain on mastication or slight tooth mobility may be present in some cases. Although single sinus tract [Figure 1a] is most frequently seen in many cases, intraoral swelling with multiple sinus tracts is not uncommon. Isolated pockets with probing characteristics of sinus tracts are pathognomonic. These pockets extend from gingival sulcus part way or all of the way to the apex. Pockets are narrower with normal depth of sulcus on either side. Periodontal type abscesses are also one of the clinical findings in cases of vertical root fracture, which result from chronic inflammation at the fracture line. Vertical root fracture may also be detected during obturation of root canal. Sharp cracking or popping sound during root canal filling, a sharp stab of pain, bleeding in the canal or enlarged canal allowing large number of accessory cones - any one of these signs/symptoms or a combination, during root canal filling,[18] should be suspected for vertical root fractures. It is rare for all these findings to be present in a single case of vertical root fracture. Therefore, each of these clinical findings should be carefully observed and correlated with the radiographic findings, to get conclusive evidence for vertical root fracture. It is also important to observe for a crack or incomplete fracture line in the crown which may be the only clue for the detection of vertical root fracture in some cases. Staining with dyes, trans-illumination using fibreoptic light and surgical exposure are some methods to delineate fracture lines.[17] A tooth with vertical root fracture presents a clinical scenario that often mimics a tooth with failed root canal treatment or periodontal disease. So, it is important rule out these conditions in such cases.

Figure 1a

Mandibular first molar with metal crown and sinus in the buccal vestibule

Radiographic features of vertical root fracture

Radiographic features of vertical root fractures vary widely. These may be observed on radiographs as diffuse widening of periodontal ligament,[17] dislodgement of retro-filling material,[19] vertical bone loss [Figure 1b],[20] separation of root fragments[21] or displacement of apical portions of root.[22] Presence of ‘radiographic halo’ has been shown as a major finding in cases of vertical root fractures. Periodontal type lesions are also not uncommon. In an endodontically treated molar, bifurcation radiolucency [Figures 2 and 3] in conjunction with other areas is the first radiographic evidence of vertical root fracture. This stresses the importance of speedy radiographic diagnosis of vertical root fracture. Bony dehiscence's and fenestrations are also the findings in cases of vertical root fractures.[2324] Radiolucent areas adjacent to obturating material or spreader void type lucent areas can be suspected for vertical root fractures.

Figure 1b

Radiograph of the tooth in 4a showing typical J-shaped radiolucency

Figure 2

Root canal treated mandibular molar with bifurcation radiolucency

Figure 3

Root canal treated maxillary first molar with bifurcation radiolucency indicative of vertical root fracture

Histopathogenesis of vertical root fractures

Vertical root fracture invites various irritating agents like bacteria and their metabolites, necrotic pulpal tissue, sealer components and food debris, which are forced into the fracture site during mastication.

The source of bacteria in the fracture site may be due to communication from the gingival sulcus or from the canal itself (which are not removed completely from the root canal). This result in the periodontal breakdown and deep probing defects usually associated with the vertical root fractures. Although the “hollow tube theory” is disputed, the fracture represents a considerable area of exposure to the canal space for substances to enter, deteriorate and then exit as irritants.[45]

Incidence and distribution according to the type of tooth in Vertical root fractures

Premolars are the most susceptible teeth for vertical root fracture followed by molars, incisors and cuspids in descending order.[38] The most susceptible roots to fracture are maxillary and mandibular premolars, mesial roots of mandibular molars and mandibular incisors.[46]

Root depressions in the mesial roots of mandibular molars and buccal roots of bifurcated maxillary premolars are the anatomical entities that can predispose the roots to fracture.[47484950] Gher et al. suggested a low incidence of 2.3% of vertical root fractures among teeth.[51]

Patterns of vertical root fracture in vital and endodontically treated teeth

Grippo suggested that mechanical loading factors affecting teeth are magnitude, frequency, locations and direction of force. In vital teeth, excessive masticatory force leads to the attrition of occlusal surface. Forces concentrated at weaker apical part, initiate crack, which progresses coronally. In roots weakened due to endodontic treatment or post, crack begins at the apex or mid root or some other positions.[52]

Predisposing factors for vertical root fractures

In non vital teeth

Root canal anatomy

Roots narrower in mesiodistal dimension and with developmental depression such as mesial root of mandibular molars and buccal roots of premolars are more susceptible to fracture.[5053] Reduced curvature radius of roots in buccal and lingual areas.[5354] Ratio of canal width to the width of total root also increases the risk of root fracture.[55]

Change in dentin characteristics in endodontically treated teeth

Dentin of pulpless teeth exhibits more plastic deformation than does that of normal teeth. Dehydration of human dentin increases its Young's modulus, in other words it increases stiffness, which is attributed to the change in collagen cross linking of root dentin in endodontically treated teeth.[56]

Residual dentin thickness after removal of intracanal procedures

Excessive removal of dentin during coronal enlargement of canal and post space preparation.[535457]

Round canal preparation in an oval canal. This decreases the remaining dentin thickness and increases the susceptibility to fracture.[5053]

Long term calcium hydroxide as a root canal dressing may increase the risk of root fracture. Calcium hydroxide causes change in the organic matrix, which is due to disruption of link between the hydroxyapatite crystals and collagenous network in dentin.[58]

Root fractures associated with corrosion

Corrossion products of pins and posts also contribute to root fractures. In a study out of 468 teeth with root fractures, evidence of a fracture could be demonstrated radiographically by the presence of corrosion products from the pin or post or by dissolution of the pin in 71.8% of the cases.[42]

Use of spreader and vertical root fracture

Wedging effect of spreader during lateral condensation can lead to vertical root fracture. It is recommended to have increased canal taper during preparation, to allow equal distribution of stresses during lateral condensation.[55]

Obturation techniques and vertical root fracture

Excessive forces during lateral condensation technique were shown to cause vertical root fracture.[171859] Lateral condensation technique produces more apical strain, where as Obtura and Thermafil produce more coronal strain. Obtura and Thermafil also caused thermal expansion of root dentin.[60]

Post placement and vertical root fracture

Tapered end posts produce wedging effect near the apex [Figure 4], severe for posts of smaller diameter with shallower embedment. Parallel sided posts produce uniform stress distribution, whereas larger diameter and greater depth produce best stress distribution.[61] Zirconia posts are rigid, and cause vertical root fracture.[43]

Figure 4

Root canal treated and post retained mandibular premolar showing vertical root fracture

Fracture susceptibility of endodontically treated teeth has been studied. In this study, teeth with endodontic treatment alone or with post, full coverage and partial coverage restoration were surveyed for five years. All 220 teeth survived for 5 years. This study emphasizes the need for further investigations to evaluate the role of posts and complete or partial coverage restorations in protecting endodontically treated teeth from fracture.[39]

In vital teeth

Small cracks, tooth infractions, acute trauma to anterior teeth due to heavy masticatory loads or biting on hard objects may act as precursors for vertical root fracture. Another clinical entity, which may act as major cause for vertical root fracture in vital teeth is the cracked tooth syndrome.[1]

Literature of Vertical root fracture in non-endodontically treated teeth is apparently common in Chinese population.[25] There was predilection for male population. All the sixty four teeth were molars, with minimal or no restorations. The crowns showed severe attrition due to the diet pattern of this particular population and this was attributed as the cause for the fractures.[26]

DISCUSSION

Vertical root fracture associated with root canal treated teeth is one of the most difficult problems to diagnose and treat. Early detection has two fold advantages - it prevents unnecessary frustration and inappropriate endodontic treatment, and prevents extensive damage to the supporting tissues.

Diagnosis is usually confirmed through the clinical signs and radiographic features. But not all the typical signs of a fractured root may be present in each case. So, the combination of clinical signs, symptoms and radiographic features may provide a clue for the diagnosis of vertical root fracture. Also, presently CBCT has been shown to be promising in the early detection of vertical root fractures.

A periapical radiograph can detect a fracture line only in 35.7% cases. The reasons for this may be,

Superimpositions of root canals on fracture line

X-ray beam not parallel to the plane of fracture

Fracture line present in the fused root superimposed by radiopaque anatomic structures

Location of fracture line precludes the use radiograph.[3]

Cone Beam Computed Tomography has been used successfully for the early detection of vertical root fracture in both endodontically and non-endodontically treated teeth in recent studies. It is more sensitive and accurate in the detection of vertical root fractures as compared to conventional[456] and digital radiography.[6] This has been confirmed by clinical studies.[78910] It has been shown that the presence root canal filling does not significantly influence the accuracy but reduces specificity[1112] in detection of vertical root fracture by CBCT. In an vitro study, CBCT has been used successfully for diagnosing simulated vertical root fractures of thicknesses 0.5 mm,1 mm,1.5 mm and 2 mm in extracted teeth. CBCT has been shown to be more accurate in vertical root fracture with thickness of 0 to 2 mm.[13] Coming to the technical aspects, it has been shown that the accuracy varies among different CBCT systems. Also, axial scans are shown to be more accurate than sagittal and coronal slices.[12] Multi-detector CT has been compared with CBCT and digital radiography in a recent study on extracted teeth. In non root filled teeth group, MDCT has been shown to be most accurate in diagnosing vertical root fracture, where as its specificity is similar to CBCT and digital radiography. In this study CBCT is found to be most sensitive among the three in detecting vertical root fracture.[14]

Early detection of vertical root fractures avoids unnecessary bone loss, which can result in difficulty in reconstructing a bone area, where implants are the treatment of choice in future. In such cases CBCT can be recommended when conventional radiography is negative.

Limitations of CBCT

CBCT reduces the radiation dose to the patient compared to Conventional CT,[15] whereby still it is 4 to 42 times greater than panoramic examination doses.[16] The specificity of CBCT in detecting vertical root fracture can be reduced due to the presence of gutta-percha and sealers. Also, CBCT is not found in every dental office and interpretation by an expert radiologist for every scan is required.

Coming to the treatment aspects, in single rooted teeth, extraction of the tooth is recommended. In multi-rooted teeth various attempts have been made in the literature,[323334353637626364656667] by uniting the fragments and replanting the tooth in its socket. Materials like GIC, 4 META, dual cure resin cements, fiber posts with composite resins have been used to unite the fractured fragments. The periodontal defects caused by vertical root fracture have been corrected using various graft materials. The cytotoxic effects, inflammatory reactions, solubility, sealing ability and biocompatibility of these materials should be considered. Also, long-term follow up of treated cases is necessary to determine a definitive treatment strategy in these cases.

CO2 and Nd:YAG lasers have been used for the treatment of vertical root fractures on extracted teeth in a study. The results of this study indicate that currently available lasers do not have capability to fuse the fractured roots. This is because it is not possible to predict the thermal changes in the target tissue. The energy densities used in this study for melting of mineral phase for fusion of the fractured fragments induce pulpal damage in vital teeth and therefore should be considered excessive.[68]

Medico legal aspects of vertical root fractures

Poor quality root canal fillings complicate the diagnosis of vertical root fracture, which in turn extend the time for accurate diagnosis and medico legal risk. Premolar and mandibular molar teeth are more prone to medico legal claims related to vertical root fracture following root canal treatment. Post should be placed only when essential for additional core support to avoid medico-legal risk.[69]

CONCLUSION

This review comes out with the following recommendations in cases of vertically fractured teeth

CBCT can be valuable in the diagnosis and treatment of vertical root fracture, after the routine clinical and radiographic examination.

It is essential to determine the necessity of a post in endodontically treated teeth

For maxillary incisors with only access cavities no posts are required.

For posterior teeth with sufficient tooth structure remaining after tooth preparation, posts are not required.

A post and core may help prevent coronal fractures, when the remaining coronal tooth structure is very thin after tooth preparation.

Among the posts, threaded posts cause highest strain and incidence of root fracture. Parallel sided, serrated posts cause highest success rate.-[44] Posts when indicated should be passive, and use of fiber reinforced composite posts should be considered whenever possible.

Complete coverage restorations are necessary in case of endodontically treated posterior teeth except when the destruction is limited only to access cavity.

More flexible and less tapered finger spreaders are safer than stiff, conventional hand spreader.[70]

Root strength can be improved by removing the smear layer in case of fiber posts.[71]

Resin based sealers like AH-26 can be used to strengthen root canal.[71] Over flared root canals which are more susceptible to vertical root fracture can be reinforced by MTA rather than gutta-percha, resilon or composite.[7277]