Diagnosis of cracked tooth syndrome.

The incidences of cracks in teeth seem to have increased during the past decade. Dental practitioners need to be aware of cracked tooth syndrome (CTS) in order to be successful at diagnosing CTS. Early diagnosis has been linked with successful restorative management and predictably good prognosis. The purpose of this article is to highlight factors that contribute to detecting cracked teeth.

Cracked tooth is defined as an incomplete fracture of the dentine in a vital posterior tooth that involves the dentine and occasionally extends into the pulp. The term “cracked tooth syndrome” (CTS) was first introduced by Cameron in 1964.[1]

The diagnosis of CTS is often problematic and has been known to challenge even the most experienced dental operators, accountable largely by the fact that the associated symptoms tend to be very variable and at times bizarre.[2] The aim of this article is to provide an overview of the diagnosis of CTS.

Diagnosis

Diagnosing CTS has been a challenge to dental practitioners and is a source of frustration for both the dentist and the patient. Identification can be difficult because the discomfort or pain can mimic that arising from other pathologies, such as sinusitis, temperomandibular joint disorders, headaches, ear pain, or atypical orofacial pain. Thus, diagnosis can be time consuming and represents a clinical challenge.[3] Early diagnosis is paramount as restorative intervention can limit propagation of the fracture, subsequent microleakage, and involvement of the pulpal or periodontal tissues, or catastrophic failure of the cusp.[4]

The ease of diagnosis varies according to the position and extent of the fracture. Mandibular second molars, followed by mandibular first molars and maxillary premolars are the most commonly affected teeth. The tooth often has an extensive intracoronal restoration. The pain may sometimes occur following dental treatments, such as cementation of an inlay, which may be erroneously diagnosed as interferences or high spots on the new restoration. Recurrent debonding of cemented intracoronal restorations such as inlays may indicate the presence of underlying cracks.

Dental History

When eliciting the history from the patient, certain distinct clues can be obtained.[5] There may be a history of a course of extensive dental treatment involving repeated occlusal adjustments or replacement of restorations, which fail to eliminate symptoms. The patient will give a history of pain on biting on a particular tooth, often occurring with foods that have small, discrete, harder particles in them, for example, bread with hard seeds or muesli.[6] Besides pain on biting, the patient will also experience sensitivity to thermal changes, particularly cold. Patients with a previous incidence of CTS can frequently self-diagnose their condition. Occasionally, there is sensitivity to sweets. It is also important to note that there can be instances when the patient may also remain asymptomatic for a long period. Many dentists would have evaluated them without a conclusive diagnosis. Patients who have an existing cracked tooth are likely to have other cracked teeth. Habits that might contribute to cracked teeth are clenching or grinding, chewing ice, pen, hard candy, or other similar objects.

Clinical Examination

The inability to visualize the extent of the crack through clinical exam alone is one aspect that leads to the complexity of accurately determining an endodontic diagnosis. Other clues evident on examination include the presence of facets on the occlusal surfaces of teeth (identifies teeth involved in eccentric contact and at risk from damaging lateral forces), the presence of localized periodontal defects (found where cracks extend subgingivally), or the evocation of symptoms by sweet or thermal stimuli. Many authors suggest removing existing restorations and stains once the tooth has been localized to further aid in the visualization of the crack. The use of rubber dam enhances the probability of visualizing these cracks by isolating the tooth, highlighting the crack with a contrasting background, keeping the area free of saliva, and reducing peripheral distractions.

Visual Inspection

Visual inspection of the tooth is useful, but cracks are not often visible without the aid of magnifying loupes. It can be occasionally detected. However, it is not always readily apparent.

Tactile Examination

Scratch the surface of the tooth with the tip of a sharp explorer. The tip may catch in a crack.

Exploratory Excavation

Sometimes exploratory excavation becomes necessary to obtain a visual diagnosis. The decision to excavate should always be made with the consent of the patient since it is not guaranteed that a fracture will be found underneath any removed restoration. Removal of existing restorations may reveal fracture lines.

Percussion Test

They are seldom tender to percussion (when percussed apically).

Periodontal probing

Periodontal probing helps distinguish between a cracked tooth and a split tooth when the fracture line extends below the gingiva, thereby causing a localized periodontal defect. For suspected cracks, careful probing must be performed to disclose the presence of an isolated periodontal pocket. However, isolated deep probing often indicates the presence of split tooth, which predicts a poor prognosis.

Dye Test

Gentian Violet or methylene blue stains can be used to highlight fracture lines.[7] The disadvantage of this technique is that it takes at least 2–5 days to be effective and may require placement of a provisional restoration. Placing a provisional restoration undermines the structural integrity of the tooth and further propagates the crack. An additional disadvantage is that a definitive esthetic restoration cannot be obtained.

Transillumination

Transillumination is an important aid in locating the crack whether it is incomplete, as in CTS, or a complete vertical root fracture.[8] When performing transillumination, the tooth should be cleaned and the light source placed directly on the tooth. A crack that penetrates into the dentin of the tooth will cause a disruption in the light transmission under these circumstances. Transillumination is probably the most common modality for traditional crack diagnosis. There are two drawbacks to using transillumination without magnification. First, transillumination dramatizes all cracks to the point that craze lines appear as structural cracks. Second, subtle color changes are rendered invisible. Transillumination with a fiber-optic light and use of magnification will aid in visualization of a crack.[9]

Bite Tests

Symptom mimickers can be used to reproduce the symptoms associated with incomplete fractures of posterior teeth. Bite tests can be performed using orange wood sticks, cotton wool rolls, rubber abrasive wheels such as Berlew wheels, or the head of number 10 round bur in a handle of cellophane tape. When using orange wood sticks to determine cracks, the patient is asked to bite on individual cusps separately. This helps to isolate the fractured cusp.

Cotton rolls can be used to detect cracks. The patient is asked to bite down on cotton rolls and then suddenly release the pressure. Pain perceived on sudden release of pressure confirms the diagnosis. The use of rubber plungers of anesthetic carpules suspended from a length of floss can be used in a similar manner as that of cotton rolls.

Other commercially available tools are Fractfinder (Denbur, Oak Brook, IL, USA) and Tooth Slooth II (Professional Results Inc., Laguna Niguel, CA, USA). Ehrman et al. have advocated the use of this method as one with a higher level of sensitivity than that associated with the use of wood sticks. This helps in accurate identification of the involved cusp. The Fractfinder or Tooth slooth can be used on each individual cusp and the patient is asked to bite, thus allowing the placement of selective pressure on one cusp. If there is pain on biting or release of biting pressure, it is indicative that the cusp is cracked.

Vitality tests are usually positive. However, sometimes the affected teeth may display hypersensitivity to cold stimuli due to the presence of pulpal inflammation, a feature that may help to confirm a diagnosis of CTS.

Radiograph

Radiographs can aid in evaluating the pulpal and periodontal health of a tooth, but it is rare to see a crack on a radiograph.[10-13] Radiographs tend to be of limited use as fractures tend to propagate in a mesiodistal direction, parallel to that of the plane of the film. However, they can be useful in detecting more rarely occurring fractures which may run in a buccolingual direction and for excluding other dental pathology.

Microscopic Detection

Experienced clinicians using a clinical microscope have reached a general consensus that ×16 provides an ideal magnification level for the evaluation of enamel cracks, with a range from ×14 to ×18.[14] Use of the clinical microscope makes possible the treatment of asymptomatic but structurally unsound posterior teeth.

Ultrasound is also capable of imaging cracks in simulated tooth structure and could pose an important diagnostic aid in the future. Where direct diagnostic methods prove unsuccessful, indirect diagnostic methods like banding can be used to detect CTS. The use of copper rings, stainless steel orthodontic bands, and acrylic provisional crowns may be placed on the tooth to prevent separation of the crack during function. Upon review, following a period of 2–4 weeks after the application of immediate splint, the absence of pain has been described to indicate not only a correct diagnosis but also successful immobilization.

Another indirect diagnostic method is an unauthenticated technique which Banerji et al. mentioned in their review on cracked teeth. They recommend placing composite resin over the tooth without etching and bonding. The material is added and wrapped across the external line angles that act as a splint. The patient when asked to bite finds a great reduction in discomfort as the material acts as a splint.

Differentiating a Cracked Tooth from a Fractured Cusp or Split Tooth

If a crack can be detected, use wedging to test for movement of the segments to differentiate a cracked tooth from a fractured cusp or split tooth. No movement with wedging forces implies a cracked tooth. A fractured cusp may break off under slight pressure with no further mobility. A split tooth will show mobility with wedging forces and the mobile segment extends well below the cemento-enamel junction.

Conditions that may be misdiagnosed as a cracked tooth involve the following: Acute periodontal disease, reversible pulpitis, dentinal hypersensitivity, galvanic pain, postoperative sensitivity associated with microleakage from recently placed composite resin restorations, fractured restorations, and areas of hyperocclusion from dental restorations, pain from bruxism, orofacial pain, or atypical facial pain.

Conclusion

The possibility of CTS must always be considered when a patient complains of pain or discomfort on chewing or biting. In spite of CTS being a diagnostic challenge, having knowledge and awareness of CTS should enable the dental practitioner to detect the same, thereby preventing further crack propagation and complications associated with crack propagation.