Figure 1-26 Poorly fitting intracoronal restorations can place stresses within the tooth that can cause a vertical root fracture. A, This radiograph of a mandibular second premolar (with a gold inlay) reveals extensive periapical and periradicular bone loss, especially on the distal. B, The tooth pulp tested nonvital, and there was an associated 12-mm-deep, narrow, isolated periodontal pocket on the buccal aspect of the tooth. After the tooth was extracted, the distal aspect was examined. C, Upon magnification (16x) the distal aspect of the root revealed an oblique vertical root fracture. Similarly, the placement of an ill-fitting post may exert intraradicular stresses on a root that can cause a fracture to occur vertically. D, This radiograph depicts a symmetrical space between the obturation and the canal wall, suggesting a vertical root fracture. E, After the tooth is extracted, the root fracture can be easily observed.
Certainly, of the previous three categories, fractured teeth are the most variable in presentation, in that the extent of the fracture is often difficult to determine. One of the more common reasons for recurrent endodontic pathosis is the vertical root fracture, a severe crack in the tooth that extends longitudinally down the long axis of the root. Often it extends through the pulp and to the periodontium. It tends to be more centrally located within the tooth, as opposed to being more oblique, and typically traverses through the marginal ridges. These fractures may be present prior to endodontic treatment, secondary to endodontic treatment, or they may develop after endodontic treatment has been completed. Because diagnosing these vertical root fractures may be difficult, they often go unrecognized. Typically, these cracks lead to a split root, leaving the tooth with a poor prognosis. Therefore, diagnosing the existence and extent of a vertical root fracture is imperative prior to any restorative or endodontic treatment since these cracks can dramatically affect the overall success of treatment. Because the presence of vertical root fractures play such an important role in the prognosis assessment of teeth, a detailed analysis of vertical root fractures is presented here.
Etiology of a Vertical Root Fracture
Vertical root fractures may arise from a physical traumatic injury, occlusal prematurities,13 repetitive parafunctional habits of heavy stressful chewing,93 or resorption-induced pathologic root fractures.7 However, the most common cause of vertical root fractures may be iatrogenic dental treatment.7,13,65 Dental procedures such as the placement of posts and pins28,54 or the tapping into place of a tightly fitting post or intracoronal restoration may induce a vertical root fracture (Fig. 1-26). The most common dental procedure contributing to vertical root fractures is endodontic treatment.7 Preoperatively, teeth that are about to undergo endodontic treatment may be predisposed to vertical root fractures since quite often the tooth is already compromised from extensive coronal restorations, caries, resorption, or trauma. Teeth were once thought to be more susceptible to fracturing after endodontic treatment because of a decrease in hydration.36 However, later studies found no difference in the dentin properties after endodontic procedures.38,77 Although the physical characteristics of the dentin may not be compromised by endodontic treatment, the over-enlarging of an endodontic access and excessive canal shaping will result in an increased amount of dentin removal. Consequently, the root may become weaker and may be more predisposed to vertical root fractures. Intracanal forces from excessive compaction pressure during obturation may also contribute to an increased incidence of vertical root fractures.7,54
Date Added: 15 May 2006
Karl Keiser, DDS, MS, University of Texas Health Science Center at San Antonio
Degree of canal taper and the resistance to root fracture
Both the American National Standard Institute (ANSI) and the International Organization for Standardization (ISO) have established standards for the manufacture of endodontic hand instruments.1,2 The creation of tolerances for tip diameters and percent taper has given clinicians a certain confidence when selecting appropriate instruments during the cleaning and shaping process. For many years, tip sizes increased by 0.05 mm (from 0.10 mm through 0.60 mm) and 0.10 mm (from 0.60 mm through 1.40 mm), while increase in diameters within any given instrument was 2% (that is, for every mm from the tip, the diameter increased by 0.02 mm). For an excellent description and figures, see Chapter 8 by Drs. Himel, McSpadden, and Goodis.
More recently, both hand and rotary root canal instruments with non-standardized tip diameters and tapers have been manufactured. Chapter 9, by Drs. Peters and Peters, describes the majority of available files systems in detail, with suggested techniques for their clinical usage.
One concern of increased taper of the root canal preparation lies in the strength of the remaining root dentin. Several papers have addressed the effect of dentin removal on the root strength, and as common sense dictates, increased dentin removal leads to a decrease in root strength.3,4,5 Recently, a study by Zandbiglari, Davids, and Schäfer compared the effect of instrument taper on the fracture resistance of endodontically prepared extracted human roots.6 All canals were instrumented to a size 40 at the apex with either 2% tapered hand files with no coronal flaring or with nickel titanium rotary files. FlexMaster 2% rotary files were used in a crown-down manner (proceeding apically with decreasing tip size and constant 2% taper), and GT rotary files were also used with a crown down technique (proceeding apically with decreasing taper and constant tip size). In this manner, the taper of the canals created by these techniques increased from hand instruments to FlexMaster to GT Rotary Files. An uninstrumented group served as a negative control. Half of the instrumented teeth were obturated with gutta percha and AH Plus sealer. In all groups, a Universal Testing Machine created vertical forces at a 15-degree angle to the long axis of the roots. The force required to fracture the roots was noted, and mean forces were statistically compared. As expected, the uninstrumented roots required significantly more force to fracture than the instrumented roots. There was no difference in the force required to fracture the hand-instrumented roots and the roots prepared with 2% taper FlexMaster instruments. There was, however, significantly less force required to fracture the more highly tapered GT Rotary File-prepared roots. Obturation had no significant effect on root strength.
Of course these results cannot be directly extrapolated to the clinical condition, but it does give one pause to consider the balance between the taper necessary to adequately fill a prepared root canal and the effect of increased preparation taper on the incidence of vertical root fracture of endodontically treated teeth. The effects of today's larger-tapered preparations may not be seen clinically for several years.
1. American National Standard Institute: ADA Specification No. 28 for Root Canal Files, New York, 1981, The Institute.
2. International Organization for Standardization: Dental Root-Canal Instruments. Part 1. Files, Reamers, Barbed Broaches, Rasps, Paste Carriers, Explorers and Cotton Broaches, Geneva, 1992, The Organization.
3. Trabert KC, Caput AA, Abou-Rass M: Tooth fracture--a comparison of endodontic and restorative treatments. J Endod 4:341-345, 1978. MedlineSimilar articles
4. Sornkul E, Stannard JG: Strength of roots before and after endodontic treatment and restoration. J Endod 18:440-443, 1992. MedlineSimilar articles
5. Gutmann JL: The dentin-root complex: anatomic and biologic considerations in restoring endodontically treated teeth. J Prosthet Dent 67:458-467, 1992. MedlineSimilar articles
6. Zandbiglari T, Davids H, Schafer E: Influence of instrument taper on the resistance to fracture of endodontically treated roots. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 101:126-131, 2006. MedlineSimilar articles
Determination of a Vertical Root Fracture
The assessment of a potential vertical root fracture may be based more on subjective than on objective findings, making the diagnosis more like an art than a science, but early detection is crucial. Many subtle findings can lead the clinician to suspect a vertical root fracture.17 Medical and dental histories are very important. Clinical, periodontal, and radiographic examinations may be at best only suggestive of a vertical root fracture. The tooth is typically painful, with symptoms ranging from mild to severe in intensity. When the tooth is painful, patients will typically complain of symptoms when they occlude or release on the tooth in a specific direction. Also noteworthy is the anatomic location of the tooth in question. Mandibular second molars have a higher incidence of vertical root fractures, followed by maxillary first molars and maxillary premolars.13 Prominent cusps, balancing interferences, and occlusal prematurities may all be factors in this predisposition to fracturing.
The patient's medical history may seem like an unlikely place to discover any suggestion of a vertical root fracture. But a history of facial trauma may add information to help in the creation of a differential diagnosis. For example, patients with seizure disorders may be prone to dental trauma, either from severe seizure-induced clenching, or from physical injuries sustained secondary to a grand mal seizure (Fig. 1-27). Additionally, a patient who has had a stroke, heart attack, or any other ailment that might have resulted in lack of consciousness could have traumatized a tooth. This could result in a vertical root fracture if the trauma is directed accordingly.
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Figure 1-27 Physical trauma from sports-related injuries or seizure-induced trauma, if directed accordingly, may cause a vertical root fracture in a tooth. This fracture occurred in a 7-year-old child secondary to trauma from a grand mal seizure.
Various comments made by a patient when a dental history is taken may direct the clinician to suspect a vertical root fracture. A patient might report ice chewing or other parafunctional habits. A patient might also describe a symptom by stating "the tooth only hurts when I bite a certain way." Comments like "it only started hurting after I accidentally bit down on a cherry pit" might also be suggestive of a vertical root fracture. Other comments concerning recent dental treatment may also be significant. Localized pain on tooth after the placement of a cast post or cast intracoronal restoration could also implicate a vertical root fracture. The repeated falling out of a coronal restoration could be due to a fracture between the axial walls of the preparations; as the fractured segments flex or move apart, the restoration between these segments may lose its resistance form, become loose, and dislodge. Similarly, a retrograde restoration that has become dislodged could be secondary to a vertical root fracture apically.24,65 As the apical fracture opens up, the retrograde restoration may come out (Fig. 1-28). An endodontic procedure that was performed well but does not result in healing may also be suggestive of a vertical root fracture, especially if the tooth does not heal after retreatment or apical surgery.
Clinical Evaluation of a Vertical Root Fracture
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Figure 1-28 Pulp infections that are refractory to endodontic treatment may often result from vertical root fractures. A, This radiograph shows the placement of retrograde restorations in the apex of the mesial roots of this lower left first molar. B, The photograph shows that the restorations are directly in the root's apex. C, After a little more than a year, the retrograde restorations are observed to have been dislodged, suggesting the possibility of a vertical root fracture.
Occasionally a vertical root fracture can be observed upon clinical examination. The use of a dental operating microscope may be invaluable in detecting cracks and fractures in the clinical crown and root surfaces. Probing the crack may elicit pain or even reveal moving segments on either side of the crack line, indicating a split tooth. To determine the extent of the fracture, it is important to apply some pressure to the cusps that are adjacent to any visible crack (Fig. 1-29). Occasionally, pressure to the cusp or actual probing of the crack will reveal a split tooth that would not have otherwise been found.
Vertical root fractures may manifest as a selective sensitivity when the tooth is percussed in a particular direction. The back end of a dental mirror handle is a very useful instrument. There are also specially designed bite sticks that when applied to a certain part of the tooth may elicit pain that would not be present when biting on another location of the tooth's occlusal surface (see Fig. 1-20).
Highly suspect of a vertical root fracture is a tooth with minimal or no restoration or caries that is nonvital. Except for luxation injuries, systemic disease (for example, intraoral herpes zoster)33 or surgical procedures that may accidentally devitalize a tooth (i.e., sinus surgery, orthognathic surgery, accidental extraction of a tooth with subsequent replantation); for example, a vertical root fracture is one of the few reasons for such a tooth to become nonvital (Fig. 1-30). A tooth with recurrent endodontic pathosis and a post that is an abutment to a cantilever bridge should also be suspected of having a vertical root fracture (Fig. 1-31). The torque created during mastication on the cantilevered pontic and the subsequent flexing of the bridge can cause stresses in the root that lead to vertical root fracture. Persistent symptoms on a tooth with a conservative cast intracoronal restoration should also make the clinician suspicious of a vertical root fracture. Generally speaking, there has to be a reason for a tooth becoming nonvital and/or causing pain. The clinician should evaluate the restorative treatment, or lack thereof, and try to make an assessment as to whether or not there is sufficient cause for necrosis or symptoms; differential diagnosis should always include vertical root fracture under these circumstances.
Multiple Sinus Tracts
Also indicative of a vertical root fracture is the presence of multiple sinus tracts adjacent to the tooth in question. Since the fracture may be present on at least two surfaces of the tooth, the infected area may drain to multiple sites, creating multiple sinus tracts.24
Dental Operating Microscope
Used in medicine for years, the dental operating microscope (DOM) has become an invaluable tool when doing endodontic treatment. With magnification capabilities of over 25×, and with superb illumination, the clinician is now capable of observing intracoronal and extracoronal details with great precision. Sometimes a fracture may be observed extracoronally prior to endodontic treatment; its depth can be visualized intracoronally with the DOM after an endodontic access has been created (Fig. 1-32).
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Figure 1-29 Often it is difficult to diagnose a root fracture unless the coronal restoration is removed. A, This radiograph shows no evidence of a fracture. B, However, once the crown and post are removed, the fracture is easily visualized. C, Sometimes it is helpful to physically push on the axial walls of the clinical crown in order to observe the existence of a fracture.
Often the only definitive way of determining if there is a vertical root fracture or split tooth is by direct surgical exposure. For optimal visualization of a potential fracture, a full thickness mucoperiosteal flap incision should be created at the level of the sulcus and reflected apically. Typically, only a small flap is necessary, since once the flap is reflected, if there is a vertical root fracture, it can usually be seen after the overlying granulation tissue is removed. Many times there is an associated boney dehiscence directly over the fracture. The use of a DOM is especially helpful in maximizing the illumination and visualization of these defects (Fig. 1-33).
Transillumination and Dyes
Often it may be necessary to remove the restoration in the tooth to better visualize the fracture. Methylene blue dye when painted on the tooth surface with a cotton tip applicator will penetrate into cracked areas. The excess dye may be removed with a moist application of 70% isopropyl alcohol. The dye will indicate the possible location of a crack. Transillumination may be more helpful (Fig. 1-34). Directing a high-intensity light directly on the exterior surface of the tooth at the cementum-enamel junction (CEJ) may indicate the extent of the fracture. Teeth with fractures block transilluminated light. The part of the tooth that is proximal to the light source will absorb this light and glow, whereas the area beyond this fracture will not have light transmitted to it and will be grey by comparison.65 Although the presence of a fracture may be evident using dyes and transillumination, the depth of the fracture cannot always be determined.
Radiographic Evaluation of a Vertical Root Fracture
Occasionally, a vertical root fracture or a split tooth may be an obvious diagnosis based on radiographic findings (Fig. 1-35). However, most of the time the fracture is in a plane that is not perceptible from a periapical radiograph. In one study72 using extracted teeth, investigators determined that a fracture becomes visible when the x-ray beam is directed within 4 degrees of the fracture plane. Outside of this horizontal angulation, a fracture may not be discernible. They also found that when a vertical root fracture is present, it is observed in a radiograph only 35.7% of the time (Fig. 1-36).
Another interesting way of detecting vertical root fractures or split teeth is from a CAT scan. This technique has been shown to be superior to dental radiography in the detection of vertical root fractures.94 However, this type of imaging is typically not yet available in a dental office.
To assist the clinician, other radiographic signs may be helpful in the detection of vertical root fractures.
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Figure 1-30 A tooth with minimal or no restoration or caries is unlikely to become nonvital. A, This radiograph of the mandibular second molar shows a restoration that is distant from the pulp chamber, yet the tooth is nonvital and symptomatic. B, Upon occlusal examination, a slight crack is observed on the distal marginal ridge. C, After extraction, the mesial aspect of the crown and root shows no indication of a fracture. D, However, the distal aspect of the crown and coronal root shows the fracture. E and F, When the crown is sectioned, the crack can be observed to extend well into the pulp chamber.
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Figure 1-31 A, Cantilever bridges can create oblique forces on an abutment tooth, especially if that tooth has endodontic treatment with a post. B, A distal-extension removable partial denture can compound the stresses on the abutment tooth, setting up a situation that can predispose that tooth to a vertical root fracture.
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Figure 1-32 Often the radiograph does not give a good indication of a vertical root fracture. A, This mandibular second premolar is nonvital, with a restoration that is not significantly close to the pulp chamber. B, The interior walls of the pulp chamber are examined under high magnification (12X) to reveal a vertical root fracture.
When the vertical root fracture or split root extends from the mesial to the distal of the tooth, often this crack can be "interpreted" after endodontic treatment has been performed. Sometimes a "cement trail" can be seen up or across the root. This is the cement extruded through and out of the fracture site, after which it becomes visible radiographically. It can be confused with the obturation passing through accessory canals, but the appearance is more diffuse in cases of vertical root fractures, with no observation of a symmetrical lateral canal passing from a main canal (Fig. 1-37).
Halo-like Bone Loss
Typically, when a nonvital tooth causes radiographic changes, the bone loss occurs apically. However, often when there is a vertical root fracture or split root, the bone loss has a tendency to give a "halo-like" appearance, traversing circumferentially around the root. The radiolucent area may also travel almost completely up one side of the root, with this pattern of bone loss often termed a "J-type" lesion88 (Fig. 1-38).
Isolated Bone Loss
The clinician should be aware of unusual radiographic changes revealing extensive bone loss that is isolated to just one tooth in the absence of advanced periodontal disease (Fig. 1-39). This could be suggestive of a vertical root fracture or split tooth.
A widened canal space which is inconsistent with the canal spaces of the adjacent roots (Fig. 1-40).
A radiolucent space presenting between the long axis of the obturation material (or post) and the canal wall (Fig. 1-41).
An associated bone loss mesial and distal to the root. When a vertical root fracture or split root extends from the mesial to the distal of the tooth, there is often an atypical widening of the entire periodontal ligament space.
When these features are visualized on the radiograph, a vertical root fracture or split tooth should be strongly suspected.
Periodontal Evaluation of a Vertical Root Fracture
Typically, a vertical root fracture or split tooth has associated bone loss contiguous with the fracture line. Left undetected, this creates a dehiscence in the bone and a V-type pattern of bone loss extending apically. The periodontal pocket associated with this bone loss is generally isolated, narrow, and deep (Fig. 1-42); a similar defect may occur 180 degrees opposite to the defect (i.e., the other side of the fracture on the other side of the root). When the periodontal probe is inserted into this type of periodontal pocket, it is tight within the pocket, and the periodontal probe's movement from side to side is restricted. This is a classic periodontal presentation and is practically pathognomonic for a vertical root fracture or split tooth.
Prognosis of a Vertical Root Fracture
A patient who consents to endodontic treatment must be informed if the tooth has a questionable prognosis. The clinician must be able to interpret the subjective and objective findings that suggest a vertical root fracture or split tooth, be able to make a prediction as to the eventual potential of healing, and must convey these suspicions to the patient. The prognosis assessment should be described as follows:
If a coronal crack is observed with nonmovable segments and the patient does not have symptoms, notwithstanding any other adverse parameters the tooth has a good prognosis.
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Figure 1-33 When a vertical root fracture is suspected, sometimes the reflection of a surgical flap over the root may allow better visualization. A, The radiograph here shows no indication of a root fracture. B, However, after surgical exposure, the fracture can be seen. C, Unfortunately, this tooth was never extracted and is observed with a prominent split root a year later. D, Similarly, the radiograph of this mandibular anterior tooth shows no indication of a root fracture. E, However, when the root is surgically exposed, the fracture is easily seen.
If the tooth is sensitive upon probing the occlusal crack, with the opposing segments nonmovable, then the prognosis is more guarded. The patient should understand that the pending endodontic treatment may not resolve the symptoms and that the prognosis is only fair. If endodontic treatment is performed, the interior walls of the access should be carefully examined, preferably with the use of a DOM along with transillumination, to determine if the crack has traversed into the canal space (see Fig. 1-32). If this is observed, the patient should again be advised of the potential for a more compromised prognosis. The tooth should be restored with a bonded intracoronal core in the access, the use of a post should be avoided, and a full-coverage restoration with cuspal reinforcement should be placed.76,90
If there are movable segments on either side of the occlusal crack, then the prognosis is poor. Often the movement of the segments is difficult to visualize, so magnification is essential. If this tooth is nonvital, with a minimal caries and restorative history, and has a deep, narrow, isolated periodontal pocket with normal periodontium otherwise, then a vertical root fracture or a split root should be highly suspected, and extraction should be considered.
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Figure 1-34 Sometimes there is no clear indication of why a tooth is symptomatic. This radiograph shows a mandibular second molar with a moderately deep restoration (A); the pulp tests nonvital. Without any transillumination a fracture cannot be detected (B). However, by placing a high-intensity light source on the tooth surface, a root fracture can be observed on the buccal (C) and the distal-lingual (D).
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Figure 1-35 A and B, Vertical root fractures that develop into split roots are sometimes easy to diagnose from a radiograph.
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Figure 1-36 Although split roots are not always radiographically visible, the precise angulation of the radiation source is necessary in order to observe them. A, A root fracture is not visible in the radiograph of this mandibular first premolar. B, However, if exposed with only a small change in the horizontal angulation, the fracture becomes visible.