Craze lines are present in the enamel structure of a tooth. The majority of adult teeth will have craze lines. These are the result of “normal” wear and tear from occlusal action. In molar teeth, they are frequently present in the marginal ridges and extending along buccal and lingual surfaces. These craze lines are asymptomatic and require no treatment. Craze lines are best differentiated from cracks by trans-illuminating the tooth. In a tooth with a true craze line the whole tooth will be illuminated, whereas in a cracked tooth the light will not progress through the crack line into the adjacent segments.
Fig. 2.11 Flowchart for pulp test when radiographic assessment is abnormal. N normal, AbN abnormal, AbN L abnormal and lingering
A fractured cusp typically involves a vertical and horizontal component of the tooth. The degree of extension can be variable. It can be a complete or an incomplete fracture that is initiated from the crown and extends obliquely in a gingival direction. Occlusally, a fractured cusp can appear to be off-center; this can help differentiate it from a cracked tooth. Classically, if the fracture progresses it will shear off a cusp completely. The pulp may or may not be exposed as a result of this and the fracture may also progress below the gingival attachment.
Frequently, a molar tooth with a cuspal fracture and a Class II restoration can lead to a destabilized marginal ridge. Typically, the crack results in sporadic sharp pain during mastication that can be simulated when a patient applies pressure to the individual offending cusp. A biting test of the cusp will elicit brief, sharp pain, especially upon release of biting pressure. Typically, the pulpal response to thermal testing will either indicate a normal pulp or possibly reversibly inflamed pulp. Percussion assessment is also frequently normal unless the percussion is in a direction such that it causes movement of the cusp. Similarly, radiographic assessment will also be normal or inconclusive.