Crown infraction refers to the incomplete fracture of a tooth. In English, the term “cracked-tooth syndrome” is used.
It is a crack or fracture in the tooth that is either limited to the crown only or involves the root.
Teeth that exhibit an infraction are, for the most part, teeth that have already been restored with fillings. The mandibular posterior teeth (molars) are often affected because they are subjected to high pressure during chewing.
Symptoms – complaints
Crown infraction does not always cause discomfort. Often, patients do not know that a tooth already has an infraction. Sometimes a brief, stabbing pain is noticeable when food is ingested. A common symptom is tooth sensitivity to hot and cold. Sensitivity to biting of the affected tooth may also occur.
Continuous pain is not present, but may occur if the crack spreads to the pulp (tooth nerve) and inflammation of the nerve (pulpitis) occurs.
Pathogenesis (disease development) – etiology (causes)
There are several causes that can lead to infraction. The most common reason given is trauma (injury), such as can occur when accidentally biting down on a hard fruit pit. The sudden clenching of teeth in an accident or fright can also cause such high stress that a tooth infracts.
Teeth that are already weakened are particularly at risk. These include teeth with large carious defects, large fillings or root canal-treated teeth.
Infraction can also occur on a weakened tooth in the course of dental treatment, for example if too much pressure is applied when a root canal filling is inserted.
Factors that additionally increase the risk of infraction are parafunctions – grinding and pressing – as well as occlusal trauma* and incorrect loading. * Occlusal trauma was defined as early as 1917: “a condition in which closing of the jaws results in damage to the retaining apparatus of the teeth with submicroscopic or microscopic changes in the root membrane, causing reversible pathologic mobility” (Stillman 1917).
Consequential diseases
If an infraction spreads to the pulp (tooth nerve), it can cause pulpitis (inflammation of the tooth nerve). Sometimes the affected tooth must then undergo root canal treatment.
Diagnostics
Diagnosing an infraction is often difficult; often the cracks are so fine that they are barely visible to the naked eye. A classic symptom is the appearance of pain after biting down on a hard object. This can be easily tested by the dentist. Likewise, an attempt can be made to make the crack visible with dye.
Therapy
To treat the infraction, it is first necessary to prevent the crack from progressing by splinting the tooth. This must be followed by a final restoration of the tooth using a partial crown or crown to adequately protect it from complete fracture. Ceramic inlays can also provide adequate stability. After definitive restoration, the discomfort associated with the infraction, such as sensitivity to temperature and bite, usually subsides as well:
