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Cracked-tooth syndrome
Cracked-tooth syndrome
Caryl E. Cameron,* D.D.S., M.S., Chicago
The most important factor in diagnosis of a cracked tooth is awareness that these cracks occur. The predominant symptom is discomfort to pressure and thermal changes. Deeper cracking can be pre vented. Bicuspids and molars frequently are frac tured and split mesiodistally into buccal and lingual fragments. Diagnosis is obvi ous, and treatment is by extraction. T o prevent these fractures in teeth severely weakened by deep caries or root canal therapy, the cusps should be routinely protected with overlays or complete ve neer crowns. In fact, failure to do this is inadequate dental service. The problem is the early diagnosis of a crack in a vital tooth and its treatment to prevent further splitting. Teeth do crack; there are symptoms, and early rec ognition will help protect these teeth also. The following observations led to the con clusion that there is a cracked-tooth syndrome. The first observation came through a patient’ s complaint of pain on application of cold or pressure to the tooth. This hap pened in a molar in which a simple mesio-
occlusal inlay had been placed recently. The complaints were dismissed as normal sensitivity to a new inlay. Later complaints of sensitivity to pressure brought occlusal adjustment; the inlay was thought to have been “ high.” A year later, a distal cusp broke off, and the patient said she was finally comfortable. It probably had been cracked all that time. This recalled similar incidents in which teeth painful on chewing were relieved when a cusp broke away, even though sensitive dentin then was exposed. In these fractures, there was no pulp involvement, and the patient could chew comfortably on that side again. The second observation came from curiosity as to why some posterior teeth had abscessed. There was no periodontal disease, only small shallow restorations, and the teeth with large restorations had no pulp exposures. Yet the pulp had died; there was roentgenographic evidence of rarefaction at the apex, and the tooth was extracted (Fig. 1). When examined with a hand lens, many o f these teeth were found to have cracks extending into the cementum from the marginal ridge or gingival margin of the proximal restoration. The cracks were
92/406 • THE JO U R N A L O F THE A M ER IC A N DENTAL ASSOCIATION
before it was extracted. These latter teeth were covered with complete veneer crowns and still are giving good service ten years later. Fractures had been pre vented. H IS T O R Y
Fig . I • Sm all shallow restoration with no obvious reason fo r rad iolucent region a t apex. C ra c k is not seen roentg eno g rap hically
either mesial, distal or both. On section ing, the crack extended into the pulp, but the tooth had not fractured (Fig. 2 ). When the patients were questioned, some gave histories o f pain; others remembered nothing. Several mentioned having had occlusal adjustment o f that tooth. A third observation concerned three patients I treated ten years ago. They had fractured teeth which had to be ex tracted. Shortly thereafter, each com plained of pain in another tooth. All diagnosed the crack themselves since the pain was similar to that in the other tooth
Fig. 2 • Three ty p ica l R ig h t:U p p e r bicuspid
cracked
teeth
a fte r
In the literature, much has been written about completely fractured teeth, but there are only a few references to cracks or incomplete fractures. In 1954, Gibbs1 described the incom plete fracture as “ cuspal fracture odon talgia,” and he discussed cause, diagnosis, and treatment. No case histories were pre sented. Mellion2 in 1956 described the history, symptoms and treatment o f a fractured cusp. Thom a3 described “ fis sured fractures” and stated that, if deep, fractures may allow bacteria to invade the pulp. He also stated4 that these “ frac tures in posterior teeth caused by occlusal force are not always easily detected.” Ritchie and others5 in 1957 reported 22 instances of pulpitis resulting from incom plete tooth fracture. All but one had restorations of soft cast gold. The authors observed the symptoms and the progres sion through pulpitis and endodontic therapy to complete veneer crowns. Some vital teeth were kept vital by early recog nition and protection.
sectioning.
L e ft:U p p e r
molar.
M id d le :L o w e r
molar.
Fig. 3 • C ra c k extending from g ing ival m argin of restoration ap ically. T o p :G o ld inlay. M id d le : A m alg am . B o tto m :H ig h e r m agnification o f am al gam shown above
Sutton6 in 1962 described “ greenstick fracture of the tooth crown.” Eight cases o f cracked cusps were treated by remov ing the fractured tooth substance and re storing the tooth. In each, the fracture line went from the pulpal wall of an old cavity preparation out toward the cementoenamel junction. He and Ritchie agreed that an awareness of the problem is the most important factor in diagnosis. Sutton considered the greenstick fracture an in termediate stage o f fracture between the development of a crack and the fracture o f the tooth. H e stated that they are caused by trauma from lateral forces in teeth weakened by cavities. D IA G N O S IS
Although many dentists are aware of cracked teeth, it seldom is covered in textbooks and has not been brought to the attention o f students. The most important factor in its diagnosis is an awareness of the problem. A well-known maxillofacial surgeon and diagnostician7 reported that patients with cracked teeth frequently were sent to him as diagnostic problems. The patients were in pain; pulps were vital; there were no cavities, and the res torations were good. He and others have helped collect 50 examples o f cracked posterior teeth. Symptoms are not always clear-cut, nor is the tooth always easily identifiable. There may be vague pains when the teeth are heated or cooled and discomfort in chewing, and the patient may favor the affected side. The most common com plaint is pain to pressure. If the patient cannot localize the pain, tapping the teeth often will help him do so. The vari ous cusps should be tapped in all direc tions. Sometimes by biting on a wooden toothpick the patient can demonstrate the location.
Fig. 4 • Top:Transverse section showing crack into pulp. M id d !e :H ig h e r m agnification of transverse section shown ab o ve. Bottom :Transverse and hori zontal section showing crack into pulp from o cclu sal and proximal surfaces
Sensitivity to thermal changes in a tooth that previously has been comfort able is the other common complaint. This is differentiated easily from sensitive cementum by examination in the mouth. In many teeth with occlusoproximal, two-surface restorations, the crack can be seen over the remaining intact marginal ridge. Frequently, there will be occlusal caries in the crack, or the crack may be discovered when a cavity is prepared. When there is no approximating tooth, the crack may be seen along the entire proximal surface or from the gingival margin of a restoration apically (Fig. 3 ). Some cracks can be seen by transillumina tion; others can be stained with iodine, Mercurochrome or other dyes. The difficult diagnosis occurs when no crack can be seen. These teeth have mesioocclusodistal restorations which ap pear serviceable. By wedging with an in strument along a margin, pain often can be elicited. In others the restoration must be removed before the crack is visible. Some cracks are difficult to see in the pos terior of the mouth even though one feels sure they must be present. Checks in the enamel alone do not appear as wide or deep as cracks extending deeper. A tooth weakened by deep cavity preparation is more suspect. Electric pulp tests seldom are needed. If there is an obvious crack but no symp toms, the pulp may be dead, and a pulp test may help decide. A vital pulp re sponds to temperature changes and to wedging the sides of a crack apart. Full coverage of the apparently healthy cracked vital tooth may be indicated to prevent deeper cracking. T o try to deter mine the depth of the crack or to elimi nate it in a healthy vital tooth could be dangerous. The pulp might be exposed needlessly if the crack terminated near it.
CA M ERO N . . . VO LUM E 68, MARCH 1744 • 95/409
As the crack deepens, the typical pain of pulpitis arises. The crack then can be followed to determine its extent and whether extraction or endodontic therapy and full coverage is the better method o f treatment. RESU LTS
Fifty cracked teeth have been examined. T h e histories have not all been complete, but the cracks were seen in every instance. If not seen in the mouth, they were found after extraction and were examined with the dissecting microscope (Fig. 4 ). The teeth were then sectioned horizontally or transversely, or they were split and stained with safranine for depth o f plaque pene tration (Fig. 5 ). Fractured teeth or those with root canal fillings were not included. Fifty-four per cent of the teeth were from women, although one ordinarily thinks o f men being more muscular and biting harder. Patients were at least 35 years old. Some ages were known; others, estimated. Forty per cent were 60 or over; 32 per cent were 50 or over, only 28 per cent were under 50. It is well known that teeth grow more brittle with age and crack more easily, and these results sup port this. The locations of the teeth are shown in Table 1. T h e mandibular second molar was the one most frequently cracked; generally, the crack extended from the distal surface over the occlusal surface, sometimes to or including the mesial surface. In the max illary molars, the crack, if completed, usually would have gone into the bifur cation, separating the two buccal roots from the lingual one. Likewise an upper bicuspid would tend to split between the roots. T w o thirds of these cracked teeth were vital or acutely inflamed with a roentgenographically normal apex. The other third showed bone loss at the apex and were obviously dead. O f the total, 27 were ex tracted; 21 were restored, and 2 are yet to be treated. Th e tabulation o f symptoms is shown
in Table 2. Some patients had no symp toms; many had pain to more than one stimulus. A history o f discomfort before diagnosis ranging from one month to ten years was present in 29 of the 50 teeth. In 7 teeth, temporary relief had been achieved by adjusting the occlusion by grinding. Tabulation of the types of old restora tions was difficult. Some teeth had both hard and soft gold inlays; some had gold inlays and silver amalgam fillings, and histories were incomplete for some teeth in which fillings were missing after ex traction. O f the total number of restora tions, 35 per cent were soft gold, 13 per cent hard gold and 39 per cent amalgam ; restorations were missing in 13 per cent.
Fig. 5 • A :Safran in e-stain ed plaque in crack ex tend in g into pulp. B :C le a n fracture w here tooth was split with chisel; there is no p laque to stain
96/410 • THE JO U R N A L OF THE A M ERICAN DENTAL ASSOCIATION
D IS C U S S IO N
T ab le 2 • Symptoms of cracked teeth
I always had used soft 22 K gold for in lays but, after reading the work o f Ritchey and others,6 I began using a harder gold. M y results, however, show that teeth filled with silver amalgam cracked even more frequently than those filled with gold. Preliminary studies of photomicro graphs o f soft gold inlays show no distor tion below the surface in these cracked teeth. I f the inlays had been distorted, the force could have been transmitted toward the walls o f the cavity, wedging them apart. T h e inlays usually had been in place a number o f years, so that it is unlikely the cracks originated from malleting the inlays into place. It seems doubtful that expansion o f amalgam causes the cracking. The amal gam fillings had also been in place many years, and expansion was probably over long before. I f the expansion was continu ing or excessive, it apparently would cause the amalgam to flow out o f the cavity.8 T he cracking is most directly re lated to the depth of the cavity. The cracking o f intact teeth without caries or fillings can only be explained as a result of force. The force exerted to cause the crack
Table 1 • Locations of the cracked teeth Tooth
N o.
Per cent
Mandibular Second molars
17
34
First molars
9
18
Third molars
1
2
Bicuspids
1
2
12
24
Maxillary First molars Second molars
2
4
First bicuspids
&
12
Second bicuspids
2
4
50
100
Total
Pain
N o . of patients
Pressure
27
Cold
16
Heat
14
Ache
9
Cellulitis
5
Sw eet
1
N one reported
6
seems to be a prolonged hammering. Al most 60 per cent gave histories o f discom fort for from one month to ten years. A few could remember a sudden force, but these usually had suffered complete frac tures. Most occlusal surfaces had wear facets, which are evidence o f interfer ences, interceptive contacts or bruxism. Others had steep cusps and deep fossae where wedging could explain the cracking. Patients vary in the amount o f muscle pressure used in biting. Many o f these with cracked teeth delighted in exerting maximum pressure on foods whether heeding it or not. They took pleasure in biting hard. With over 200 lb. o f pressure possible in multiple blows over a long time, “ something has to give.” The centrally located cracks seem to follow the lines of the dentinal tubules and lead toward the pulp, causing its ex posure. The more peripheral cracks seem to lead to cuspal fracture, with or with out pulpal exposure, depending on the amount of secondary dentin. An interesting observation was that in lays became uncemented in teeth that later proved to be cracked. Another was patient diagnosis. Seven patients had lost another tooth by fracture. These patients said the pain of the cracked tooth was the same as that of the previous tooth before extraction. One patient was pleased to have two cracked teeth discovered in a routine examination. H e already had had three teeth extracted because of
CAM ERO N
cracking and was wearing a partial den ture replacing them. One cracked molar either had been weakened by internal re sorption or had been stimulated to resorp tion by irritation from the crack. Relief of symptoms by adjusting the occlusion was only temporary; eventually the symp toms returned. In six patients, there had been no pain that they could remember. Five o f these had cracks found on examination or dur ing cavity preparation. It is assumed they had not progressed far enough to be pain ful, yet all had penetrated the dentin. The remaining crack was found in an asymp tomatic tooth extracted because of radiolucency at the apex. C O N C L U S IO N S
There is a cracked-tooth syndrome. An awareness that these cracks occur is the prime factor in diagnosis. The predomi
105th Annual Session o f the American Dental Association and 52nd Annual Session o f the Fédération Dentaire Internationale November 9-12, San Francisco
. VO LUM E 68, MARCH 1964 • 97/411
nant symptom is discomfort to chewing pressure. Unexplained sensitivity to ther mal changes is almost as important. Other factors, such as staining, wedging and tapping, assist in early diagnosis when full coverage can prevent further cracking and pulp exposure. 670 North Michigan Avenue
*Assîstant professor of diagnosis, Northwestern Uni versity Dental School, Chicago. 1. Gibbs, J . W . Cuspal fracture odontalgia. D. Digest 60:158 April 1954. 2. Mellion, G. L. Case report: a fractured molar cusp. D. Survey 32:614 May 1956. 3. Thoma, Kurt H. Oral surgery, ed. 3. St. Louis, C. V. Mosby Co., 1958. 4. Thoma, Kurt H. Oral pathology, ed. 5. St. Louis, C. V. Mosby Co., I960. 5. Ritchey, Beryl; Mendenhall, Robert, and Orban, Balint. Pulpitis resulting from incomplete tooth fracture. Oral Surg., Oral Med. & Oral Path. 10:665 June 1957. 6. Sutton, P. R. N. Greenstick fracture of the tooth crown. Brit. D. J . 112:362 May I, 1962. 7. Stuteville, O. H. Personal communication. 8. Skinner, E. W ., and Phillips, R. W . The science of dental materials, ed. 5. Philadelphia, W . B. Saunders Co., I960.
Caryl E. Cameron,* D.D.S., M.S., Chicago
The most important factor in diagnosis of a cracked tooth is awareness that these cracks occur. The predominant symptom is discomfort to pressure and thermal changes. Deeper cracking can be pre vented. Bicuspids and molars frequently are frac tured and split mesiodistally into buccal and lingual fragments. Diagnosis is obvi ous, and treatment is by extraction. T o prevent these fractures in teeth severely weakened by deep caries or root canal therapy, the cusps should be routinely protected with overlays or complete ve neer crowns. In fact, failure to do this is inadequate dental service. The problem is the early diagnosis of a crack in a vital tooth and its treatment to prevent further splitting. Teeth do crack; there are symptoms, and early rec ognition will help protect these teeth also. The following observations led to the con clusion that there is a cracked-tooth syndrome. The first observation came through a patient’ s complaint of pain on application of cold or pressure to the tooth. This hap pened in a molar in which a simple mesio-
occlusal inlay had been placed recently. The complaints were dismissed as normal sensitivity to a new inlay. Later complaints of sensitivity to pressure brought occlusal adjustment; the inlay was thought to have been “ high.” A year later, a distal cusp broke off, and the patient said she was finally comfortable. It probably had been cracked all that time. This recalled similar incidents in which teeth painful on chewing were relieved when a cusp broke away, even though sensitive dentin then was exposed. In these fractures, there was no pulp involvement, and the patient could chew comfortably on that side again. The second observation came from curiosity as to why some posterior teeth had abscessed. There was no periodontal disease, only small shallow restorations, and the teeth with large restorations had no pulp exposures. Yet the pulp had died; there was roentgenographic evidence of rarefaction at the apex, and the tooth was extracted (Fig. 1). When examined with a hand lens, many o f these teeth were found to have cracks extending into the cementum from the marginal ridge or gingival margin of the proximal restoration. The cracks were
92/406 • THE JO U R N A L O F THE A M ER IC A N DENTAL ASSOCIATION
before it was extracted. These latter teeth were covered with complete veneer crowns and still are giving good service ten years later. Fractures had been pre vented. H IS T O R Y
Fig . I • Sm all shallow restoration with no obvious reason fo r rad iolucent region a t apex. C ra c k is not seen roentg eno g rap hically
either mesial, distal or both. On section ing, the crack extended into the pulp, but the tooth had not fractured (Fig. 2 ). When the patients were questioned, some gave histories o f pain; others remembered nothing. Several mentioned having had occlusal adjustment o f that tooth. A third observation concerned three patients I treated ten years ago. They had fractured teeth which had to be ex tracted. Shortly thereafter, each com plained of pain in another tooth. All diagnosed the crack themselves since the pain was similar to that in the other tooth
Fig. 2 • Three ty p ica l R ig h t:U p p e r bicuspid
cracked
teeth
a fte r
In the literature, much has been written about completely fractured teeth, but there are only a few references to cracks or incomplete fractures. In 1954, Gibbs1 described the incom plete fracture as “ cuspal fracture odon talgia,” and he discussed cause, diagnosis, and treatment. No case histories were pre sented. Mellion2 in 1956 described the history, symptoms and treatment o f a fractured cusp. Thom a3 described “ fis sured fractures” and stated that, if deep, fractures may allow bacteria to invade the pulp. He also stated4 that these “ frac tures in posterior teeth caused by occlusal force are not always easily detected.” Ritchie and others5 in 1957 reported 22 instances of pulpitis resulting from incom plete tooth fracture. All but one had restorations of soft cast gold. The authors observed the symptoms and the progres sion through pulpitis and endodontic therapy to complete veneer crowns. Some vital teeth were kept vital by early recog nition and protection.
sectioning.
L e ft:U p p e r
molar.
M id d le :L o w e r
molar.
Fig. 3 • C ra c k extending from g ing ival m argin of restoration ap ically. T o p :G o ld inlay. M id d le : A m alg am . B o tto m :H ig h e r m agnification o f am al gam shown above
Sutton6 in 1962 described “ greenstick fracture of the tooth crown.” Eight cases o f cracked cusps were treated by remov ing the fractured tooth substance and re storing the tooth. In each, the fracture line went from the pulpal wall of an old cavity preparation out toward the cementoenamel junction. He and Ritchie agreed that an awareness of the problem is the most important factor in diagnosis. Sutton considered the greenstick fracture an in termediate stage o f fracture between the development of a crack and the fracture o f the tooth. H e stated that they are caused by trauma from lateral forces in teeth weakened by cavities. D IA G N O S IS
Although many dentists are aware of cracked teeth, it seldom is covered in textbooks and has not been brought to the attention o f students. The most important factor in its diagnosis is an awareness of the problem. A well-known maxillofacial surgeon and diagnostician7 reported that patients with cracked teeth frequently were sent to him as diagnostic problems. The patients were in pain; pulps were vital; there were no cavities, and the res torations were good. He and others have helped collect 50 examples o f cracked posterior teeth. Symptoms are not always clear-cut, nor is the tooth always easily identifiable. There may be vague pains when the teeth are heated or cooled and discomfort in chewing, and the patient may favor the affected side. The most common com plaint is pain to pressure. If the patient cannot localize the pain, tapping the teeth often will help him do so. The vari ous cusps should be tapped in all direc tions. Sometimes by biting on a wooden toothpick the patient can demonstrate the location.
Fig. 4 • Top:Transverse section showing crack into pulp. M id d !e :H ig h e r m agnification of transverse section shown ab o ve. Bottom :Transverse and hori zontal section showing crack into pulp from o cclu sal and proximal surfaces
Sensitivity to thermal changes in a tooth that previously has been comfort able is the other common complaint. This is differentiated easily from sensitive cementum by examination in the mouth. In many teeth with occlusoproximal, two-surface restorations, the crack can be seen over the remaining intact marginal ridge. Frequently, there will be occlusal caries in the crack, or the crack may be discovered when a cavity is prepared. When there is no approximating tooth, the crack may be seen along the entire proximal surface or from the gingival margin of a restoration apically (Fig. 3 ). Some cracks can be seen by transillumina tion; others can be stained with iodine, Mercurochrome or other dyes. The difficult diagnosis occurs when no crack can be seen. These teeth have mesioocclusodistal restorations which ap pear serviceable. By wedging with an in strument along a margin, pain often can be elicited. In others the restoration must be removed before the crack is visible. Some cracks are difficult to see in the pos terior of the mouth even though one feels sure they must be present. Checks in the enamel alone do not appear as wide or deep as cracks extending deeper. A tooth weakened by deep cavity preparation is more suspect. Electric pulp tests seldom are needed. If there is an obvious crack but no symp toms, the pulp may be dead, and a pulp test may help decide. A vital pulp re sponds to temperature changes and to wedging the sides of a crack apart. Full coverage of the apparently healthy cracked vital tooth may be indicated to prevent deeper cracking. T o try to deter mine the depth of the crack or to elimi nate it in a healthy vital tooth could be dangerous. The pulp might be exposed needlessly if the crack terminated near it.
CA M ERO N . . . VO LUM E 68, MARCH 1744 • 95/409
As the crack deepens, the typical pain of pulpitis arises. The crack then can be followed to determine its extent and whether extraction or endodontic therapy and full coverage is the better method o f treatment. RESU LTS
Fifty cracked teeth have been examined. T h e histories have not all been complete, but the cracks were seen in every instance. If not seen in the mouth, they were found after extraction and were examined with the dissecting microscope (Fig. 4 ). The teeth were then sectioned horizontally or transversely, or they were split and stained with safranine for depth o f plaque pene tration (Fig. 5 ). Fractured teeth or those with root canal fillings were not included. Fifty-four per cent of the teeth were from women, although one ordinarily thinks o f men being more muscular and biting harder. Patients were at least 35 years old. Some ages were known; others, estimated. Forty per cent were 60 or over; 32 per cent were 50 or over, only 28 per cent were under 50. It is well known that teeth grow more brittle with age and crack more easily, and these results sup port this. The locations of the teeth are shown in Table 1. T h e mandibular second molar was the one most frequently cracked; generally, the crack extended from the distal surface over the occlusal surface, sometimes to or including the mesial surface. In the max illary molars, the crack, if completed, usually would have gone into the bifur cation, separating the two buccal roots from the lingual one. Likewise an upper bicuspid would tend to split between the roots. T w o thirds of these cracked teeth were vital or acutely inflamed with a roentgenographically normal apex. The other third showed bone loss at the apex and were obviously dead. O f the total, 27 were ex tracted; 21 were restored, and 2 are yet to be treated. Th e tabulation o f symptoms is shown
in Table 2. Some patients had no symp toms; many had pain to more than one stimulus. A history o f discomfort before diagnosis ranging from one month to ten years was present in 29 of the 50 teeth. In 7 teeth, temporary relief had been achieved by adjusting the occlusion by grinding. Tabulation of the types of old restora tions was difficult. Some teeth had both hard and soft gold inlays; some had gold inlays and silver amalgam fillings, and histories were incomplete for some teeth in which fillings were missing after ex traction. O f the total number of restora tions, 35 per cent were soft gold, 13 per cent hard gold and 39 per cent amalgam ; restorations were missing in 13 per cent.
Fig. 5 • A :Safran in e-stain ed plaque in crack ex tend in g into pulp. B :C le a n fracture w here tooth was split with chisel; there is no p laque to stain
96/410 • THE JO U R N A L OF THE A M ERICAN DENTAL ASSOCIATION
D IS C U S S IO N
T ab le 2 • Symptoms of cracked teeth
I always had used soft 22 K gold for in lays but, after reading the work o f Ritchey and others,6 I began using a harder gold. M y results, however, show that teeth filled with silver amalgam cracked even more frequently than those filled with gold. Preliminary studies of photomicro graphs o f soft gold inlays show no distor tion below the surface in these cracked teeth. I f the inlays had been distorted, the force could have been transmitted toward the walls o f the cavity, wedging them apart. T h e inlays usually had been in place a number o f years, so that it is unlikely the cracks originated from malleting the inlays into place. It seems doubtful that expansion o f amalgam causes the cracking. The amal gam fillings had also been in place many years, and expansion was probably over long before. I f the expansion was continu ing or excessive, it apparently would cause the amalgam to flow out o f the cavity.8 T he cracking is most directly re lated to the depth of the cavity. The cracking o f intact teeth without caries or fillings can only be explained as a result of force. The force exerted to cause the crack
Table 1 • Locations of the cracked teeth Tooth
N o.
Per cent
Mandibular Second molars
17
34
First molars
9
18
Third molars
1
2
Bicuspids
1
2
12
24
Maxillary First molars Second molars
2
4
First bicuspids
&
12
Second bicuspids
2
4
50
100
Total
Pain
N o . of patients
Pressure
27
Cold
16
Heat
14
Ache
9
Cellulitis
5
Sw eet
1
N one reported
6
seems to be a prolonged hammering. Al most 60 per cent gave histories o f discom fort for from one month to ten years. A few could remember a sudden force, but these usually had suffered complete frac tures. Most occlusal surfaces had wear facets, which are evidence o f interfer ences, interceptive contacts or bruxism. Others had steep cusps and deep fossae where wedging could explain the cracking. Patients vary in the amount o f muscle pressure used in biting. Many o f these with cracked teeth delighted in exerting maximum pressure on foods whether heeding it or not. They took pleasure in biting hard. With over 200 lb. o f pressure possible in multiple blows over a long time, “ something has to give.” The centrally located cracks seem to follow the lines of the dentinal tubules and lead toward the pulp, causing its ex posure. The more peripheral cracks seem to lead to cuspal fracture, with or with out pulpal exposure, depending on the amount of secondary dentin. An interesting observation was that in lays became uncemented in teeth that later proved to be cracked. Another was patient diagnosis. Seven patients had lost another tooth by fracture. These patients said the pain of the cracked tooth was the same as that of the previous tooth before extraction. One patient was pleased to have two cracked teeth discovered in a routine examination. H e already had had three teeth extracted because of
CAM ERO N
cracking and was wearing a partial den ture replacing them. One cracked molar either had been weakened by internal re sorption or had been stimulated to resorp tion by irritation from the crack. Relief of symptoms by adjusting the occlusion was only temporary; eventually the symp toms returned. In six patients, there had been no pain that they could remember. Five o f these had cracks found on examination or dur ing cavity preparation. It is assumed they had not progressed far enough to be pain ful, yet all had penetrated the dentin. The remaining crack was found in an asymp tomatic tooth extracted because of radiolucency at the apex. C O N C L U S IO N S
There is a cracked-tooth syndrome. An awareness that these cracks occur is the prime factor in diagnosis. The predomi
105th Annual Session o f the American Dental Association and 52nd Annual Session o f the Fédération Dentaire Internationale November 9-12, San Francisco
. VO LUM E 68, MARCH 1964 • 97/411
nant symptom is discomfort to chewing pressure. Unexplained sensitivity to ther mal changes is almost as important. Other factors, such as staining, wedging and tapping, assist in early diagnosis when full coverage can prevent further cracking and pulp exposure. 670 North Michigan Avenue
*Assîstant professor of diagnosis, Northwestern Uni versity Dental School, Chicago. 1. Gibbs, J . W . Cuspal fracture odontalgia. D. Digest 60:158 April 1954. 2. Mellion, G. L. Case report: a fractured molar cusp. D. Survey 32:614 May 1956. 3. Thoma, Kurt H. Oral surgery, ed. 3. St. Louis, C. V. Mosby Co., 1958. 4. Thoma, Kurt H. Oral pathology, ed. 5. St. Louis, C. V. Mosby Co., I960. 5. Ritchey, Beryl; Mendenhall, Robert, and Orban, Balint. Pulpitis resulting from incomplete tooth fracture. Oral Surg., Oral Med. & Oral Path. 10:665 June 1957. 6. Sutton, P. R. N. Greenstick fracture of the tooth crown. Brit. D. J . 112:362 May I, 1962. 7. Stuteville, O. H. Personal communication. 8. Skinner, E. W ., and Phillips, R. W . The science of dental materials, ed. 5. Philadelphia, W . B. Saunders Co., I960.