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Fractured vital teeth
Periodontia FRACTURED EVERETT
VITAL
TEETH
C. CLAUS, D.D.S.,# II)ENvER, COLO., AND BALINT M.D., D.D.S.,‘” COLORADO SPRINGS, COLO.
ORBAN,
T
HE retention of vitality in completely fractured teeth is rare, and only a few cases have been reported in the literature. Such a case is herein described, with the microscopic studies of the repair process. A 51-year-old white man gave the hist,ory of having injured his front teeth at the age of ll-forty years previously. Roentgenologic examination revealed two fractured central incisors. The teeth tested vital. The patient stated that t’he teeth were sore and tender for a short time after injury, but this sensitivity disappeared and since that time the teeth had given him no discomfort,. The four incisors had to be removed for prosthetic reasons, and, becauseof the necessary alveolectomp, the four incisors were removed in one block. This tissue block was fixed in 10 per cent neutral formalin, embedded in celloidin, and sectioned for microscopic examination. The literature reports only a few microscopic studies of fractured vital teeth. Gottliebl described a fracture of the apical half of the root of an upper cuspid of a man who died at the age of 22 years. Nothing was known about, the The date of the accident or the type of trauma t,hat had caused the fracture. crown of the tooth was intact; the pulp appeared vital, although the root was broken into several large and small pieces. Bone and cement,um had been deposited over all of the area of fracture, covering the exposed dentin and partl) uniting the fragments. Howe2 reported the histologic findings in a cuspid that had sustained a cross-fracture of the root six months before extraction. A solid union of the fragments had t,aken place. The newly formed hard substance between the fragments originated from the periodontal membrane and pulp and it consisted of cementum and irregular dentine. BoulgeF reported a case of cross-fracture of the roots of the two lower central incisors. The fragments of one tooth were close together, but not united; however, in the other the fragments were widely separated and the apical fragment was surrounded by connective tissue and a large number of small bone trabeculae. Presented Research, March *Veterans **Colorado
at
the Thirtieth General Meeting of 23, 1952, Colorado Springs, Colo. Administration Hospital. Dental Foundation. 605
the
International
Association
for
Dental
Kront’eld’
tlcscribcs
a c~~Y~ss-~‘I~;I~~~ III’C of iIt1 upper central incisor in the ilJ)i~%l third Of the root. ‘I’hc two fragments did not unite, but the pulp remained vital and both dentint> surfaces wrc cwveretl 1)~ ~ementimr. The periodontal to the other. membrane extended t’rorll one ~mglncwt ~1 large amount of irregufoix~ed in the pulp c*haniber and along the wall of the root lar clentine had kw cm1al.
The roentgenograllr i Fig. 1 ) of’ tire surgical specimen of our case demonstrates a fracture in the apical thirtl 01’ the right, central incisor and in the middle third of the left cclltral incisor. The pulp canals seem somewhat narrowed, but. are present; the coronal part 01’ the pulp in both central incisors seems to be reducecl in vizc. The lamiua dura ant1 supporting bone show no remarkable cahanges: the periodontal membrane is visible all around the roots. The alveolar crests are without pathologic signs.
The tissur Mock was separated into two parts bet,ween the central incisors and sectioned in two bloc*ks. both in mcsiodistal, i.e., frontal direction. The right cent,ral and lateral incisors arc seen in Fig. 2, in a low-power photomicrograph. The fracture space is clcarl>- visible in the apical third of the central The lamina incisor, running slightly oblique from mesioapical to distocoronal. dura of the alveolar hone follows (~(tt~ollal as well as apical fracture ends, showing a slight indentation at the I’ract IIW space, but there is only a slight dislocation of the fracture cn~ls. .I c~ncntu111 tear is seen on the mesial side of the central incisor, close 1o t hc ~aiielitot~iiaiiiel junction: the torn-out cementum has been reattached to the surfarc. A similar cernentuni tear is present on the mesial surface of the lateral incisor at about the middle of the root. Other tears of the cementum of this tooth seem to be artifacts caused at t,he time of surgical removal. The fracture ends facing each other show signs of resorption (Fig. 3), which is partly repaired by deposition oi’ a bonclike, hard substance upon dentine as well as cementurn of the fractured or resorbed root ends. Between these fragment ends a fibrons connective tissue, with numerous small capillaries, can
FRACTURED
VITAL
607
TEETH
be seen. In the center of the space, t,here is a bone spicule with vital osteocytes. Facing the apical fragment, some giant cells, osteoclasts, are seen on the surface of the bone, indicating active resorption at the time of surgical removal. In the pulp chamber, a hard substance can be seen completely filling the The newly space (Fig. 2) and extending along the walls of the pulp canal. formed hard substance lies either on the surface of the darker stained, intact dentine, or is laid down in resorption lacunae (Fig. 4). The hard substance is slightly lamellated in texture and shows a varying number of entrapped cells, some with long processes. Such cells are seen along t,he resorption line of the dentine. Dark lines are seen in the newI>7 formed hard substance. These are
central of the mesial
Fig.
2.-Photomicrograph incisor is in the apical central incisor on the side.
of the third. mesial
right central and lateral incisors. The fracture A healed cementurn tear is seen in the incisal side and in the mitlillr~ of the lateral incisor
of on
the third the
remnants of the original hypercalcified zones of dentine and predentine. The pulp tissue is somewhat fibrous, showing numerous vessels. No regular odontoblasts are seen in this area-only flattened cells line the surface. In someareas, the cells lining the pulp canals are more like odontoblasts. In some regions, the newly formed hard substance resemblesbone more than anything else (Fig. 5). This illustration is from the coronal fragment at the border line of pulp and fracture space distally from the pulp canal. Osteocytes are present in this hard substance and some connective tissue fibers are embedded as Sharpey’s fibers
wit bin th surface 0 of the de
resorption surfaces. without
Fig. Fig.
B.--Frwture
to\vard 4.-Newly Hard PI wxxliny
t-n,is
covt’re,t
apical fragment. formal hard substance is laid rrsorption.
by
substance ,lown
bone.
in
(bone artws
I:one
spiculc
01’ dentine-like) of preceding
bctuwm lines resorption,
fract pulp
ure canal ir I other
ends
xvitll on both rep ;ions
The fracture site of the left centjral incisor appears somew hat differ rent from tha ,t of the right,. The fracture is complete, but in one area the fracl ture ends are in close proximity (Fig. 6), where it, seemsthat, the two 1‘racture c:nds
FRACTURED
VITAL Fig.
Fig.
in cc
Fig. 5.Fig. G.ose tct a
609
TEETH
5.
6.
:wly formed hard substance. bonelike with acture site of left central incisor. In one lindermining without vital tissue between.
Sharpey’s flber spot, the two resorption
‘S.
fra on
.cture
bo bth
ends sides
610
IWERETT
(‘.
(%.\I,-S
.\NI)
Fig.
odontol: dentine
B:\ LTNT
ORB.0
7.
Fi
:r\
b ‘undies,
and
1 dentine
and
St:-
Fi
8.“OLK
Lpical end substance.
of
coronal Tlone
fracture formation
Odontoblasts part. on opposite fracture
trapped end.
b&w
FRACTURED
VITAL
611
TEETH
were rubbing on each other. There is no vital tissue between the fragments in t,his restricted space. On both sides of this contact surface, active resorption of dentine and eementum has taken place, undermining the contact area. From this region, toward the pulp canal, a newly formed hard substance is laid down upon t,he resorbed dentine. In the pulp canal of this tooth, hard substance formation is in progress, but it consists mostly of regular dentine (Fig. 7), with well-formed odontoblasts. Toward the fracture site, the odontoblasts lose their regular appearance and the hard substance loses its dentine character. The hard subst,ance here is fibrous, without dentinal tubules. It consists of dentine ground substance wit,hout the processes of odontoblasts (Fig. 8). Numerous odonto-
Fig. Fig.
9.-Apical hard
9.
Fig.
fracture part. structure laid down
dentinelike flat. Fig. IO.-Cementurn fiable hard substance.
tear
(from
Dentine after lateral
surface shows resorption the fracture occurred. incisor)
healed
to dentine
10.
lacunae Pulp, fibrous surface
with a bone : odontoblasts, by
an
or
unidenti-
blasts appear trapped between the former predentine and the newly formed dentine ground substance. Opposing this dentine-like substance on the other surface of the fracture end, osteocyte-like cells are seen in the fibrous ground substance, simulating the character of bone. In the apical fracture end, the root canal is lined by newly formed hard substance of a rather unidentifiable nature; it might be dentine or bone, or both
(Fig. 9). This hard substance is laid down on previously rmresorbetl or resorbed surfaces. As the hard substanc~c~ approaches the pulpal surface, it takes on t,he appearance of dentine, but no regular odontoblasts or odontohlast processes are present. Several caementnm tears can bc seen on the surface of the two i’ract,ured teeth and also on the mesial surface ot’ the lateral incisor which showed no fra,cture. One of these cementum tears is shown in E’ig. 10. It is a high magnification of the cementum tear on the mesial surface in the center of the right lateral incisor (Fig. 2). The space between the dentinc and cernentnm is now filled with an unidentifiable hard substance and can be considered repaired. The surface of the cement,nnr appears to be vital. It is formed by an uncalcified rementoid which is linetl by cementoblasts. The alveolar bone follows the surI’ace of the cementum. The findings in this case correspond largely to those reported by other investigators. The pulp remained vital for a long period following traumatic fracture, as in the cases reported by Gottlieb, Bonlger, and Kronfeld. It is evident by the resorption process in the pulp canal (F’ig. 4) that considerable tissue activity must have taken place after the trauma. The odontoblasts must have disappeared; ost.eoclasts or dentinoclasts must have developed, probably from undifferentiat,ed rnesenchpmal cells, leading to resorption of the dentine. After a period of time, the resorption stopped and a new hard substance had been laid down. This hard substance is often difficult to classify. It can resemble dentine (Fig. 4) or bone (Fig. 5). Sometimes the ground substance is characteristic (Fig. 8)) but the cellular structure of the tissue is missing. From analyzing the tissue changes which took place in this case, one can draw the conclusion that an “internal” resorption has t,aken place after the trauma, and one can wonder if trauma of minor consequences might not be a canse of “internal resorption. ” The formation of a bone spicule between the fracture ends (Fig. 3) might. be interpreted as the result of functional stimulus from the coronal fragment. The dentine and the cementum of the fracture ends facing each other are coverccl by bonelike tissue (Fig. 3). The connective tissue bebween these fragments is somewhat fibrous and some fiber bundles are seen embedded as Sharpey’s fibers into the bonelike hard substance (Fig. 5). The pulp in some arclas appears quite normal (Fig. 7) : in others it is rat,lret* fibrous (Fig. 4). In the apical fragment (Fig. 9). as well as coronal (Figs. 7 and 8), nerve bundles and blood vessels are evident. In fact, one can see these tissue elements pass from the apical into the coronal end. One could assume that these teeth remained vital after the injury because it occurred at an earl?age (11 years). The apex of the central incisor at this age is almost, completeI> formed, but there is still a wide foramen, as cornpared to that of an adult. A fracture at this age would be favorable t.o recovery after injury because of favorable circulation. One can assume that considerable hemorrhage would take place at the time of injury. but good circulation can lead to better organization and repair if the main blood vessels have not been severed.
FRACTURED
VITAL
TEETH
613
Torn cementum has been reported in literature in numerous cases.” Union between the torn fragments and tooth surface frequently occurs, as in the present case (Fig. 10). The union is established in some instances by bone, sometimes by cementum-like subst.ancc, and sometimes! as in this case, by an unidentifiable hard substance.
Summary A case of fractured vital teeth has been reported. The teeth rernained vital for forty years. The first tissue reaction to the injury was resorption of dentine in both fracture ends in certain areas. This was probably preceded by extensive hemorrhage. In other areas, only a longer resting period in dentine formation might have occurred and then dentine formation began again in a normal manner. If resorption occurred, it was repaired by the formation of a hard substance which is neither true dentine, bone, nor cementum. The ground substa,nce is the same, but the cellular element,s are not typical. In some areas, the pulp tissue is normal; in ot,hers it is more fibrous. Odontohlasts appear in some regions; in others, the cells are not typical. In circumscribed areas, odontoblasts are trapped into a seemingly rapidly formed hard substance. The fracture ends of the fragments facing each other show signs of previous resorption. The exposed dentine is covered in most areas by a bonelikc, hard substance.
References 1. C*ott,1iC+, R. : Histologicai Examination of a T-nited Tooth Fracture, Dental Items Interest 48: 577, 1926. Further Considerations of the Possil)le Results of the Fracture of 2. Howe, Percy R.: the Root of a Tooth Which Contains a Living Pulp, Dental Items Interest 49: 79, 1927. 3. Roulgrr, Earl P.: Histological Studies of a Specimen of Fractured Roots, J. Am. Dent. A. 15: 1778, 1928. 4. Kronfeld, Rudolf: The Procsess of Repair Following Tooth Fracture, J. D. Res. 11: 24i, 1931. 5. Kronfeld, Rudolf: A Case: Tooth Fracture With Special Emphasis on Tissue Repair and Adaptation Following Traumatic Tnjury. .T. 1). Res. 15: 429, 1936.
VITAL
TEETH
C. CLAUS, D.D.S.,# II)ENvER, COLO., AND BALINT M.D., D.D.S.,‘” COLORADO SPRINGS, COLO.
ORBAN,
T
HE retention of vitality in completely fractured teeth is rare, and only a few cases have been reported in the literature. Such a case is herein described, with the microscopic studies of the repair process. A 51-year-old white man gave the hist,ory of having injured his front teeth at the age of ll-forty years previously. Roentgenologic examination revealed two fractured central incisors. The teeth tested vital. The patient stated that t’he teeth were sore and tender for a short time after injury, but this sensitivity disappeared and since that time the teeth had given him no discomfort,. The four incisors had to be removed for prosthetic reasons, and, becauseof the necessary alveolectomp, the four incisors were removed in one block. This tissue block was fixed in 10 per cent neutral formalin, embedded in celloidin, and sectioned for microscopic examination. The literature reports only a few microscopic studies of fractured vital teeth. Gottliebl described a fracture of the apical half of the root of an upper cuspid of a man who died at the age of 22 years. Nothing was known about, the The date of the accident or the type of trauma t,hat had caused the fracture. crown of the tooth was intact; the pulp appeared vital, although the root was broken into several large and small pieces. Bone and cement,um had been deposited over all of the area of fracture, covering the exposed dentin and partl) uniting the fragments. Howe2 reported the histologic findings in a cuspid that had sustained a cross-fracture of the root six months before extraction. A solid union of the fragments had t,aken place. The newly formed hard substance between the fragments originated from the periodontal membrane and pulp and it consisted of cementum and irregular dentine. BoulgeF reported a case of cross-fracture of the roots of the two lower central incisors. The fragments of one tooth were close together, but not united; however, in the other the fragments were widely separated and the apical fragment was surrounded by connective tissue and a large number of small bone trabeculae. Presented Research, March *Veterans **Colorado
at
the Thirtieth General Meeting of 23, 1952, Colorado Springs, Colo. Administration Hospital. Dental Foundation. 605
the
International
Association
for
Dental
Kront’eld’
tlcscribcs
a c~~Y~ss-~‘I~;I~~~ III’C of iIt1 upper central incisor in the ilJ)i~%l third Of the root. ‘I’hc two fragments did not unite, but the pulp remained vital and both dentint> surfaces wrc cwveretl 1)~ ~ementimr. The periodontal to the other. membrane extended t’rorll one ~mglncwt ~1 large amount of irregufoix~ed in the pulp c*haniber and along the wall of the root lar clentine had kw cm1al.
The roentgenograllr i Fig. 1 ) of’ tire surgical specimen of our case demonstrates a fracture in the apical thirtl 01’ the right, central incisor and in the middle third of the left cclltral incisor. The pulp canals seem somewhat narrowed, but. are present; the coronal part 01’ the pulp in both central incisors seems to be reducecl in vizc. The lamiua dura ant1 supporting bone show no remarkable cahanges: the periodontal membrane is visible all around the roots. The alveolar crests are without pathologic signs.
The tissur Mock was separated into two parts bet,ween the central incisors and sectioned in two bloc*ks. both in mcsiodistal, i.e., frontal direction. The right cent,ral and lateral incisors arc seen in Fig. 2, in a low-power photomicrograph. The fracture space is clcarl>- visible in the apical third of the central The lamina incisor, running slightly oblique from mesioapical to distocoronal. dura of the alveolar hone follows (~(tt~ollal as well as apical fracture ends, showing a slight indentation at the I’ract IIW space, but there is only a slight dislocation of the fracture cn~ls. .I c~ncntu111 tear is seen on the mesial side of the central incisor, close 1o t hc ~aiielitot~iiaiiiel junction: the torn-out cementum has been reattached to the surfarc. A similar cernentuni tear is present on the mesial surface of the lateral incisor at about the middle of the root. Other tears of the cementum of this tooth seem to be artifacts caused at t,he time of surgical removal. The fracture ends facing each other show signs of resorption (Fig. 3), which is partly repaired by deposition oi’ a bonclike, hard substance upon dentine as well as cementurn of the fractured or resorbed root ends. Between these fragment ends a fibrons connective tissue, with numerous small capillaries, can
FRACTURED
VITAL
607
TEETH
be seen. In the center of the space, t,here is a bone spicule with vital osteocytes. Facing the apical fragment, some giant cells, osteoclasts, are seen on the surface of the bone, indicating active resorption at the time of surgical removal. In the pulp chamber, a hard substance can be seen completely filling the The newly space (Fig. 2) and extending along the walls of the pulp canal. formed hard substance lies either on the surface of the darker stained, intact dentine, or is laid down in resorption lacunae (Fig. 4). The hard substance is slightly lamellated in texture and shows a varying number of entrapped cells, some with long processes. Such cells are seen along t,he resorption line of the dentine. Dark lines are seen in the newI>7 formed hard substance. These are
central of the mesial
Fig.
2.-Photomicrograph incisor is in the apical central incisor on the side.
of the third. mesial
right central and lateral incisors. The fracture A healed cementurn tear is seen in the incisal side and in the mitlillr~ of the lateral incisor
of on
the third the
remnants of the original hypercalcified zones of dentine and predentine. The pulp tissue is somewhat fibrous, showing numerous vessels. No regular odontoblasts are seen in this area-only flattened cells line the surface. In someareas, the cells lining the pulp canals are more like odontoblasts. In some regions, the newly formed hard substance resemblesbone more than anything else (Fig. 5). This illustration is from the coronal fragment at the border line of pulp and fracture space distally from the pulp canal. Osteocytes are present in this hard substance and some connective tissue fibers are embedded as Sharpey’s fibers
wit bin th surface 0 of the de
resorption surfaces. without
Fig. Fig.
B.--Frwture
to\vard 4.-Newly Hard PI wxxliny
t-n,is
covt’re,t
apical fragment. formal hard substance is laid rrsorption.
by
substance ,lown
bone.
in
(bone artws
I:one
spiculc
01’ dentine-like) of preceding
bctuwm lines resorption,
fract pulp
ure canal ir I other
ends
xvitll on both rep ;ions
The fracture site of the left centjral incisor appears somew hat differ rent from tha ,t of the right,. The fracture is complete, but in one area the fracl ture ends are in close proximity (Fig. 6), where it, seemsthat, the two 1‘racture c:nds
FRACTURED
VITAL Fig.
Fig.
in cc
Fig. 5.Fig. G.ose tct a
609
TEETH
5.
6.
:wly formed hard substance. bonelike with acture site of left central incisor. In one lindermining without vital tissue between.
Sharpey’s flber spot, the two resorption
‘S.
fra on
.cture
bo bth
ends sides
610
IWERETT
(‘.
(%.\I,-S
.\NI)
Fig.
odontol: dentine
B:\ LTNT
ORB.0
7.
Fi
:r\
b ‘undies,
and
1 dentine
and
St:-
Fi
8.“OLK
Lpical end substance.
of
coronal Tlone
fracture formation
Odontoblasts part. on opposite fracture
trapped end.
b&w
FRACTURED
VITAL
611
TEETH
were rubbing on each other. There is no vital tissue between the fragments in t,his restricted space. On both sides of this contact surface, active resorption of dentine and eementum has taken place, undermining the contact area. From this region, toward the pulp canal, a newly formed hard substance is laid down upon t,he resorbed dentine. In the pulp canal of this tooth, hard substance formation is in progress, but it consists mostly of regular dentine (Fig. 7), with well-formed odontoblasts. Toward the fracture site, the odontoblasts lose their regular appearance and the hard substance loses its dentine character. The hard subst,ance here is fibrous, without dentinal tubules. It consists of dentine ground substance wit,hout the processes of odontoblasts (Fig. 8). Numerous odonto-
Fig. Fig.
9.-Apical hard
9.
Fig.
fracture part. structure laid down
dentinelike flat. Fig. IO.-Cementurn fiable hard substance.
tear
(from
Dentine after lateral
surface shows resorption the fracture occurred. incisor)
healed
to dentine
10.
lacunae Pulp, fibrous surface
with a bone : odontoblasts, by
an
or
unidenti-
blasts appear trapped between the former predentine and the newly formed dentine ground substance. Opposing this dentine-like substance on the other surface of the fracture end, osteocyte-like cells are seen in the fibrous ground substance, simulating the character of bone. In the apical fracture end, the root canal is lined by newly formed hard substance of a rather unidentifiable nature; it might be dentine or bone, or both
(Fig. 9). This hard substance is laid down on previously rmresorbetl or resorbed surfaces. As the hard substanc~c~ approaches the pulpal surface, it takes on t,he appearance of dentine, but no regular odontoblasts or odontohlast processes are present. Several caementnm tears can bc seen on the surface of the two i’ract,ured teeth and also on the mesial surface ot’ the lateral incisor which showed no fra,cture. One of these cementum tears is shown in E’ig. 10. It is a high magnification of the cementum tear on the mesial surface in the center of the right lateral incisor (Fig. 2). The space between the dentinc and cernentnm is now filled with an unidentifiable hard substance and can be considered repaired. The surface of the cement,nnr appears to be vital. It is formed by an uncalcified rementoid which is linetl by cementoblasts. The alveolar bone follows the surI’ace of the cementum. The findings in this case correspond largely to those reported by other investigators. The pulp remained vital for a long period following traumatic fracture, as in the cases reported by Gottlieb, Bonlger, and Kronfeld. It is evident by the resorption process in the pulp canal (F’ig. 4) that considerable tissue activity must have taken place after the trauma. The odontoblasts must have disappeared; ost.eoclasts or dentinoclasts must have developed, probably from undifferentiat,ed rnesenchpmal cells, leading to resorption of the dentine. After a period of time, the resorption stopped and a new hard substance had been laid down. This hard substance is often difficult to classify. It can resemble dentine (Fig. 4) or bone (Fig. 5). Sometimes the ground substance is characteristic (Fig. 8)) but the cellular structure of the tissue is missing. From analyzing the tissue changes which took place in this case, one can draw the conclusion that an “internal” resorption has t,aken place after the trauma, and one can wonder if trauma of minor consequences might not be a canse of “internal resorption. ” The formation of a bone spicule between the fracture ends (Fig. 3) might. be interpreted as the result of functional stimulus from the coronal fragment. The dentine and the cementum of the fracture ends facing each other are coverccl by bonelike tissue (Fig. 3). The connective tissue bebween these fragments is somewhat fibrous and some fiber bundles are seen embedded as Sharpey’s fibers into the bonelike hard substance (Fig. 5). The pulp in some arclas appears quite normal (Fig. 7) : in others it is rat,lret* fibrous (Fig. 4). In the apical fragment (Fig. 9). as well as coronal (Figs. 7 and 8), nerve bundles and blood vessels are evident. In fact, one can see these tissue elements pass from the apical into the coronal end. One could assume that these teeth remained vital after the injury because it occurred at an earl?age (11 years). The apex of the central incisor at this age is almost, completeI> formed, but there is still a wide foramen, as cornpared to that of an adult. A fracture at this age would be favorable t.o recovery after injury because of favorable circulation. One can assume that considerable hemorrhage would take place at the time of injury. but good circulation can lead to better organization and repair if the main blood vessels have not been severed.
FRACTURED
VITAL
TEETH
613
Torn cementum has been reported in literature in numerous cases.” Union between the torn fragments and tooth surface frequently occurs, as in the present case (Fig. 10). The union is established in some instances by bone, sometimes by cementum-like subst.ancc, and sometimes! as in this case, by an unidentifiable hard substance.
Summary A case of fractured vital teeth has been reported. The teeth rernained vital for forty years. The first tissue reaction to the injury was resorption of dentine in both fracture ends in certain areas. This was probably preceded by extensive hemorrhage. In other areas, only a longer resting period in dentine formation might have occurred and then dentine formation began again in a normal manner. If resorption occurred, it was repaired by the formation of a hard substance which is neither true dentine, bone, nor cementum. The ground substa,nce is the same, but the cellular element,s are not typical. In some areas, the pulp tissue is normal; in ot,hers it is more fibrous. Odontohlasts appear in some regions; in others, the cells are not typical. In circumscribed areas, odontoblasts are trapped into a seemingly rapidly formed hard substance. The fracture ends of the fragments facing each other show signs of previous resorption. The exposed dentine is covered in most areas by a bonelikc, hard substance.
References 1. C*ott,1iC+, R. : Histologicai Examination of a T-nited Tooth Fracture, Dental Items Interest 48: 577, 1926. Further Considerations of the Possil)le Results of the Fracture of 2. Howe, Percy R.: the Root of a Tooth Which Contains a Living Pulp, Dental Items Interest 49: 79, 1927. 3. Roulgrr, Earl P.: Histological Studies of a Specimen of Fractured Roots, J. Am. Dent. A. 15: 1778, 1928. 4. Kronfeld, Rudolf: The Procsess of Repair Following Tooth Fracture, J. D. Res. 11: 24i, 1931. 5. Kronfeld, Rudolf: A Case: Tooth Fracture With Special Emphasis on Tissue Repair and Adaptation Following Traumatic Tnjury. .T. 1). Res. 15: 429, 1936.