Contemporary Restoration of Endodontically Treated Teeth. Nadim Z. Baba
convenience in discussing cracks and fractures, three categories will be used: enamel craze lines, infractions, and vertical root fractures (VRFs).
Enamel craze lines. Craze lines are small cracks that are confined to the enamel of teeth (Fig 2-5). They are not typically visible unless light rays highlight them incidentally. They develop over time, so they probably can be found in most teeth eventually. Occasionally they will show stains from exposure to liquids such as coffee and red wine. Because these cracks are confined to enamel, they have no pulpal impact, and no treatment is necessary, except optional bleaching if they are stained. There is no evidence that craze lines progress to involve more than enamel.
Fig 2-5 Enamel craze lines (arrow) are common and present no particular problem other than their potential for staining.
Infractions (cracked teeth). The term cracked tooth is commonly used to describe a tooth that has developed an infraction, which is defined as “a fracture of hard tissue in which the parts have not separated”17 (Fig 2-6). Cameron18 incorrectly defined this condition as cracked tooth syndrome; the use of syndrome is not appropriate for pain associated with fractures in teeth. It is, however, a situation with a variety of symptoms, and diagnosis can be very difficult.
Fig 2-6 (a) Infractions (arrow) can be identified visually with the help of dyes, in this case a red dye. Infractions usually run in a mesiodistal direction; they may be asymptomatic or associated with pain on chewing and cold stimuli. (b) A tooth extracted because of symptoms associated with an infraction shows the presence of the infraction (arrow). They typically originate in the crown of the tooth and progress in an apical direction. (c) On rare occasions, infractions run in a faciolingual direction (arrow).
Mandibular molars and maxillary molars and premolars are the teeth most frequently associated with infractions. The teeth usually have vital pulps and the infractions typically run in a mesiodistal direction. They begin in the crowns of teeth and progress in an apical direction. Not all teeth with infractions are symptomatic, but when symptoms develop they can range from pain on chewing, to an exaggerated response to cold stimuli, to severe pain episodes that can mimic trigeminal neuralgia; chronic orofacial pain can also develop. The wide range of pain experiences is probably why Cameron18 used the term syndrome to describe this dental situation. The etiology of infractions is probably in most cases related to occlusal forces, whether from regular daily chewing or isolated trauma such as blows to the underside of the mandible.19–25
It is likely that teeth with infractions become symptomatic when the infractions become invaded by bacteria26 (Fig 2-7). Bacteria stimulate inflammation in the pulp, whether or not the infraction communicates directly with the pulp tissue. The inflamed tissue is responsible for the exaggerated cold response. It is also likely that the tooth will become sensitive to biting when the infraction progresses from the tooth crown to the root, and the bacteria that will soon occupy the infraction then stimulate an inflammatory response in the adjacent periodontal ligament (PDL).
Fig 2-7 Infractions become populated with bacteria very quickly and produce an inflammatory response in the pulp (located to the right in this section), whether they communicate directly with the pulp (as in this case) or not. This explains why such teeth respond abnormally to cold stimuli.
Diagnosis of infractions is complicated by many factors. Because infractions are usually located in a mesiodistal direction in the crown, they are not visible on radiographs.
Before the infractions progress down the roots to significantly involve the PDL, patients are unable to point to the problem teeth. Based on the patient’s complaints, the first goal of examination is to identify the problem teeth and the second is to determine the pulpal condition of these teeth.
The presence of an infraction can be determined by the use of various biting tests (Fig 2-8a), with the aid of colored dyes (see Fig 2-6a), and through transillumination with an intense light source27 (Fig 2-8b). In contrast to the way enamel craze lines are highlighted by intense light, infractions actually block the transmission of light, clearly identifying their presence.
Fig 2-8 (a) The bite test is a useful way to identify a tooth with an infraction. After biting down on a wet cotton roll (or on one of many types of biting devices), the patient will often experience a strong response when he or she releases biting pressure—the so-called release pressure pain. (b) The use of an intense light, such as that from a fiber-optic light source, will illuminate the part of the crown near the light, but the light stops at the infraction, which involves both enamel and dentin. In contrast, enamel craze lines only involve enamel, through which light rays travel unimpeded.
The status of the pulp—reversible or irreversible pulpitis— can be determined as in other situations of pulpal inflammation, that is, by the presence or absence of lingering pain to application of cold stimuli. If the pulp is reversibly involved, placement of a complete-coverage crown may be enough initially, but Krell and Rivera28 showed that about 20% of these teeth subsequently developed irreversible pulpitis. If the patient wishes to retain the tooth for as long as possible, it may be advisable to perform RCT in anticipation of a later need before a complete-coverage crown is placed. There is some promising information29 about the use of bonded resin to cover the occlusal surfaces to resist further progression of infractions.
To determine if an infraction has progressed to the root of the tooth, the use of a periodontal probe can provide some information. However, because the pocket that develops in the PDL adjacent to the infraction in the root is very narrow, it is usually necessary to anesthetize the area first; otherwise the procedure will be very painful for the patient.
The prognosis for teeth with infractions is not good. Fuss et al30 have reported that many of these teeth are extracted within 5 years following diagnosis of infraction. However, insufficient data are available to make a statement about the expected survival time of these teeth. Clinicians can only explain to patients that once this condition develops it cannot be reversed, and that it is only possible to make an effort to prolong the inevitable. With a full understanding of the poor long-term prognosis, many patients still wish to maintain such teeth for as long as possible, and that is where RCT and complete-crown coverage may be considered. It is prudent, however, to explain to such patients that periodic radiographic evaluation is recommended so that when bone loss is evident plans can be made for extraction before a large amount of bone is lost.
As the infraction progresses, the eventual result is either that the tooth splits vertically or, when the infraction involves a cusp, that the cusp fractures off, with or without exposure of the pulp.
Vertical root fractures. VRFs differ from infractions in several aspects.31 With few exceptions, VRFs occur in endodontically treated teeth (Fig 2-9). The direction of fractures is more often in a faciolingual orientation, and symptoms for the most part are mild. In some patients, symptoms are absent or so mild that the patients are unaware of any problems. VRFs typically originate from the apical end