The cracked-toothsyndrome and fractured posterior cusp D&d THE
E. Snyder,* San Antonio, UNIVERSITY
Cracked-tooth syndrome and fractured posterior cusp are fairly Their occurrence, diagnosis, and prevention are studied.
he cracked-tooth syndrome and the fractured posterior cusp are obviously related entities, since the initial lesion finally results in a fractured cusp if the crack does not run vertically into the tooth root. The cracked-tooth syndrome is characterized by sensitivity to certain biting pressures, The tooth is usually x-ra.y negative and normal to pulp vitality tests. If the dentist is unaware of this entity, or the symptoms are obscure, the cracked-tooth syndrome will remain undiagnosed. Many patients have been dismissed with the comment, “It’s all in your head.” If the case is undiagnosed and/or untreated, the pain usually continues, often increasing in severity. The condition may lead to pulpal death or the previously mentioned fractured cusp. Detailed studies of many cases by some authors dwell mostly on the mesiodistal crack which endangers the pulp. W. H. Hiattl studied 100 teeth in sixtyfour patients, and more than one third of the teeth in his study had no restorations. His study excluded teeth with both marginal ridges restored, however, since one of the diagnostic guidelines was the detection of hairline cracks over the marginal ridges. Cameron2 also dwelt on the mesiodistal crack. Ingle,3 in his text on endodontia, obviously associated cracks with endodontic problems. Even table clinics have discussed cracks as an endodontic problem.* Unlike the specialist, the average general practitioner may not have the interest in, nor have seen as many endodontic, periodontic, or exodontic cases resulting from, the cracked tooth or fractured cusp. My clinical impressions of the last few years since becoming aware of the cracked-tooth syndrome seem slightly different from those reflected in someof the articles mentioned : 1. Many of the cases of cracked-tooth syndromes were extremely difficult *Assistant Professor, Department of General Practice.
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Cra.cked-tooth syndrome and fract,ured
to diagnose if the patient had a high pain threshold, a minor crack, or a fluctuating sensitivity, such as discomfort felt only during attacks of sinusitis. Many cases would eventually become self-diagnosed because a portion of the tooth would fracture off, relieving all symptoms, except for possible sensitivity to temperature. 2. Most of the cracks and fractures did not result in exposure of the pulp. 3. Most of the cracks and fractures ended above the epithelial attachment and did not involve the root at all. (Many of the cracks and fractures which did extend into the root did so at such an angle that the pulp was not exposed, only part of the periodontium was damaged, and only a slight modification of technique was necessary to restore the tooth. Many of the cracks and fractures were through such a small cross-sectional area of dentin that it was easy to conclude why the tooth had failed. The previous decay or restorative procedure so weakened and undermined the tooth that it was inevitable that the tooth would break). This fact underlines the importance of being conservative of tooth structure. DIAGNOSIS
For the cases that are difficult to diagnose a few points should be stressed. Cracked-tooth syndrome may be confused with pulp pathosis, temporomandibular pain dysfunction syndrome, and other facial pains in some patients. Since many patients have centric prematurities, sinusitis, teeth that are sensitive to cold, and posterior teeth that give inconclusive pulp tests, we should also make every attempt to rule out the cracked-tooth syndrome as a source of pain. Any tooth with a large amalgam filling or a gold filling which does not onlay or protect the cusps should be suspect. The older the patient or the greater the intercuspation and wear, the greater the possibility of cracks. A diagnosis can sometimesbe made in difficult casesby means of special materials and methods to place painproducing pressure. Having the patient bite on a stick, cotton, a Burlew disc, or a small strip of leather will often help to locate the tooth. Sometimes, percussion with an instrument handle will help; this usually requires tapping on all cusps of a tooth. Another diagnostic aid is an amalgam condenser. With strong pressure in different directions it is possible to detect which cusp is cracked, not just which tooth. Removing the old amalgam from a suspected tooth will sometimes allow the operator to see the crack. The use of magnification, eugenol or Acrephen to stain or disclose the dentin, and transillumination or cross lighting all can help to show the cracks. Occasionally, the removal of the old restoration plus the vibration of the bur or diamond will cause the crack-weakened portion to fracture. Small fracture or crack areas permit a choice of treatment. (A few of the patients rejected treatment and the smooth fracture surface remained fairly insensitive and free from caries.) TREATMENT
Very few of the patients with the cracked-tooth syndrome could be helped by grinding the offending cusp out of occlusion rather generously. This obviously
Oral Surg. June, 1976
700 Snyder Table I. Age spread of fractured cusps and cracked-tooth syndrome Agegrouphr.)
20 to 29 30 to 39 40 to 49 so to 59 60 to 69 70 and over Total
1: ii 19 5 6 E
did not solve the problem, since the bolus of food could still exert the pain-producing pressure and did not determine the direction or severity of the crack. Some of the patients rejected cast restorations, and the defect where the tooth substance was missing or cracked was “patched” with amalgam. Most of these repairs were accomplished by slight undercuts in adjacent amalgam fillings or in available dentin surfaces wibh inverted cone, small round, or wheel burs. Only occasionally were pins used. The amalgam was condensed directly without the use of a matrix and carved out of occlusion. Most of these “patches” functioned satisfactorily. Similar old, tarnished repairs seen in patients who had been treated by other dentists showed that this treatment can last for years. Those patients who did accept castings frequently did not require full crowns. The common lingual cusp fracture of a lower molar could frequently be restored with a threequarter crown, with a projection into the buccal groove for added retention. CLINICAL REVIEW OF CASE
To investigate the incidence of cracked-tooth syndrome and fractured posterior cusps, the appointment-book records and patient records were checked with the calendar year 1974 in a general practice. The following facts were recorded about each case: age of the patient, tooth number, missing tooth structure if this was an actual fractured cusp, presence of cracked-tooth syndrome, and treatment accomplished. Brittle, cndodontically treated teeth and anterior teeth were excluded. Obviously, some cases were missed and some facts were incorrectly recorded, but the practice had no turn-over of personnel during the year recorded. (The practice was a rather small, conservative, lower-middle income, restorative practice.) When castings were used, they were usually for teeth that were badly damaged by decay, or for teeth in which amalgam restorations had failed. Many teeth were restored in amalgam which would better have been done in castings, but financial and other considerations were the deciding factors for simpler restorations. RESULTS OF CASE REVIEW
During the year, sixty-two cases were recorded as having either fractured cusps or the cracked-tooth syndrome. 0~1~ eleve?Lwere recorded as casesof the cracked-tooth syndrome alone. Of the total number, only two teeth were extracted. These two teeth were eliminated because the crack appeared to extend through the pulp and root, and the teeth were judged to be nonrestorable. All the teeth
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syndrome and fractured
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Fig. 1. Left: Wide occlusal outline one third to one half of intercuspal row occlusal outline one fourth or less of intercuspal width.
had previous restorations. Only one of them had a restoration which appeared small on the roentgenogram, and this was one of the extractions. These cases were collected from 3,537 patient visits during the calendar year of 1974. Recording the number of actual patients seen in January and multiplying by 12, the calculated number of patients was 2,628, counting the recall and dental hygiene patients. A breakdown of patients by age is shown in Table I. The greatest number of cases occurred in the age range of 30 to 59 years. No patient in whom a crackedtooth syndrome was recorded was older than 53 years. DISCUSSION Probably many cases of cracked-tooth syndrome were missed in this series because of failure to properly diagnose, as in many examinations of patients; but the average of about one per month is certainly a significant number when one is considering problems of oral and facial pain. Although it is very possible to have cracked teeth without previous restoration, this series pointed out that the large previous restoration weakens the tooth. If it is possible to keep amalgam restorations small, the number of cracked teeth should, conceivably, be kept to a minimum. The preservation of the oblique ridge in upper molars and the transverse ridge in the lower first premolars is a traditional way to retain tooth substance. Preserving the cross-sectional area of dentin should be a major objective, since the previously mentioned clinical impression was that many of the fractures occurred where dentin was small in cross section. Occlusal preparations can be kept as small as the instruments in many cases, and not following some of the older views of one third of the intercuspal width (Fig. 1). Vale5 showed that occlusal preparation widths of one fourth of the intercupsal width or less had only slight weakening effect on the teeth, whereas those that were wider materially weakened the tooth. The occlusal portion of a Class II restoration can sometimes be eliminated if the tooth anatomy and decay are favorable (Fig. 2). Bronners and Almquist? both stressed that the proximal portion of the cavity should be retentive in itself and not dependent on the occlusal dovetail for retention. Proximal outlines of amalgam preparations usually diverge as they approach the gingiva. If this divergence is great and the extension into the buccal and lingual embrasures is considerable, the cusps are
Fig. 8. Left: Class II without occlusal dovetail.
Fig. 3. Left:
Fig. 4. Left: Pulpal floor slopes. Right: ular to the long axis of the pulp.
pulp if placed perpendic-
weakened and undercut. The use of less divergence and extension can conserve tooth substance (Fig. 3). The placing of gingival margins under the gingival tissue at all times may not be necessary. Perhaps in many patients the breaking of contact gingivally to the same extent that buccal and lingual contact is broken is all that is necessary. This may help in keeping the preparation shorter occlusogingivally and therefore decrease splitting of the tooth. The lower first premolar
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syndrome and fractured
Fig. 5. Upper molar with “pot hole” at central pit.
Fig. 6. Left: Flat axial wall. Right: Curved axial wall.
is frequently mentioned as a tooth in which the pulpal floor should not be perpendicular to the long axis of the tooth because of its special anatomy (Fig. 4). Perhaps other teeth should be analyzed for this same type of dental anatomy. The upper first and sometimes second molars have very deep central pits. The other pits and grooves may not be so deep. These preparations could have a “pot hole” where the deep pit is located and the rest of the pulpal floor could remain a bit shallower (Fig. 5). In certain teeth with a need for rather wide proximals buccolingually, the axial wall can be curved just as the axial wall of a large Class V restoration is convexly curved to wrap around the pulp and conserve dentin (Fig. 6). There is a great tendency for the previous decay or restoration to guide the instrument; if this is deep, most of the rest of the preparation may end at this same depth. Carefully controlled use of the high-speed bur may be the answer to this depth problem, rather than the early use of a slow-speed bur or spoon excavator. For the tooth that is already seriously damaged, an amalgam is not the treatment of choice. The MOD onlay and the three-quarter crown are preparations which perhaps are not so popular as they should be. The high-speed handpiece and the ease of impression taking have increased the use of the full crown. The MOD onlay and the three-quarter crown protect or “shoe” the cusps. These restorations act to prevent the cracked-tooth syndrome or the fractured posterior cusp and also are more conservative of tooth substance.
Oral Surg. June, 1976
1. Even from such a small sample as that reported in this study, it, is evident that the fractured cusp and cracked-tooth syndrome are common problems. ‘I’hc large number of fractured cusps compared to the cracked-tooth syndrome suggests that some of the cases of fractured cusp could hare been diagnosed earlier. 2. It is most important that dentists be aware of the cracked-toot,h syndrome in order to relieve the patient’s discomfort, prevent the possible eventual loss of the pulp or tooth, and avoid unnecessary and possibly damaging treatment for misdiagnosed facial pain. 3. Conservation of tooth structure in restorative procedures is most necessary in order to prevent the cracked-tooth syndrome or fractured posterior cusp, REFERENCES
1. 2. 3. 4.
Hiatt, W. H.: Iucomplete Crown-root Fracture, J. Periodontol. 44: 369-379, 1973. Cameron, C. E.: Cracked-Tooth, Syndrome, J. Am. Dent. Assoc. 68: 403-411, 1964. Ingle, J. I.: Endodontics, Philadelphia, 1965, Lea & Febiger. Jurist, B. L.: Table Clinics, The Cracked Tooth Syndrome, J. Am. Dent. Assoc. 89: 326, 1974. 5. Vale, W. A.: Cavity Preparation, Irish Dent. Rev. 2: 33, 1956. 6. Bronner, F. J.: Mechanical, Physiological and Pathological Aspects of Operative Procedures, Dent. Cosmos 73: 577-584, 1931. 7. Almquist, T. C., et al.: Conservative Amalgam Restorations, J. Prosthet. Dent. 29: 524-528, 1973.
Reprint requests to: Dr. David E. Snyder Department of General Practice The University of Texas Health Science Center at San Antonio 7703 Floyd Curl Dr. San Antonio, Texas 78284