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A roentgenographic study of dentigerous cysts
A roentgenographic study of dentigerous cysts II. Role of roentgenograms in detecting dentigerous cyst in the early
Parodc illmushed, B.Ch.D., M&J.,* DEPARTMENT GRADUATE
T
OF SCHOOL
ORAL OF
ROENTGESOLOGY,
stages
Cairo, United Arab liepublic UNIVERSITY
OF
PENNSYLVANIA
MEDICINE
INTRODUCTION
he dentigerous cyst has been classified as an odontogenic cyst which originates through alterations of the reduced enamel epithelium after the crown of the tooth has been completely formed. Fluid accumulates either between the layers of the enamel epithelium or between this epithelium and the tooth crown.’ As for the origin of the dentigerous cyst,, there are two schools of thought.’ The first group is a proponent of an intrafollicular origin and regards the dentigerous cyst as a direct enlargement of the follicle surrounding the finished crown of an unerupted tooth.3-5 The intrafollicular changes are thought to be due to either inflammatory or mechanical disturbances occurring during tooth eruption. The second group favors an extrafollicular origin and suggests that at first, the cyst develops from cxtrafollicular epithelial remnants and then later unites with the follicle of an erupting tooth. 6-8However, the majority of opinions are in agreement with the theory of intrafollicular origin. In the first report in this series, an attempt was made to determine the incidence of dentigerous cyst in a population sample.” The purpose of the present study is to demonstrate t,he important role of rocntgenograms in detecting dentigerous cyst in the early stages. From a portion of a thesis prepared far the Mastrr of Science degree in Graduate School of Medicine, University of Pennsylvania. *Instructor, Oral Radiology Department, College of Dentistry, Cairo University; memhcr of the American Academy of Oral Roentgenology.
54
dentistry, active
Volume Number
18 1
Dentiyerous
cysts. II
55
METHODS AND MATERIALS Sixteen roentgenograms were used as the basis for this study of the devclopmental changes related t.o the formation of the dentigerous cyst. These roentgenograms were selected from the material available in the Oral Roentgenology Department of the University of Pennsylvania Dental School. RESULTSAND DISCUSSION The teeth develop within a crypt which exists prior to the beginning of enamel formation and calcification and remains around the crowns of the developing teeth until they have completely erupted. Therefore, it is only natural to find the crypts around the crowns of all unerupted teeth. The dentigerous cyst develops as a result of epithelial cell division causing pressure within the crypt, which results in liquefaction necrosis of the cells in the center of the mass.It is this cellular disturbance of the crypt (the cause of which is unknown) which leads to the formation of t,he dentigerous cyst. In time, the accumulation of fluid within the cyst might lead to the appearance of the typical clinical signs associated with t,he later stages of dentigerous cyst development. The most prevalent areas in which the teeth are more commonly found to be uneruptrd are, in order of frequency, the areas surrounding the mandibular third molars, t,he maxillary third molars, the maxillary canines, and the mandibular second premolars.g One of the important factors in the failure of these teeth to erupt in the four aforementioned areas is lack of sufficient space. However, the reason for this lack of space varies with the location of the area,s in the dental arch. In the mandibular and maxillary third molar areas and in the maxillary canine areas such lack of space is usually due to insufficient growt,h and expansion of the dental arch. In t,he mandibular second premolar areas, it is often caused by early loss of one or both of the deciduous molars. Fig. 1, ~1 showsa mandibular third molar tooth which failed to erupt because of lack of sufficient, space in the mandible. Fig. 1, B shows a mandibular second premolar which failed to erupt because of its tilted position and lack of space resulting from early loss of the deciduous molar. The tooth is fully developed; the crypt is enlarged, and possibly this is the beginning of dentigerous cyst formation. Fig. 1, C shows bilateral uneruptcd maxillary canines. Again, this is a case of insufficient space caused by lack of growth and expansion of t,he dental arch. The arrows point to the crypts which are still around the crowns of both teeth. The second important factor related t,o the failure of these teeth to erupt, is malpositioning of the teeth during development, causing them to assumea position in which subsequent eruption is impossible. Fig. 2, A shows an unerupted mandibular third mola,r; the tooth lies horizontally in the arch and cannot erupt in its position. Fig. 2, B shows a perpendicularly inverted mandibular third molar. Fig. 2, C shows t,wo mandibular mola.rs in a horizontal position, the crowns of both teeth facing each other. Fig. 2, D shows an unerupted mandibular second premo1a.r (2) and a posterior drifting of the first premolar. This condition is due to the early loss of the deciduous molars and malpositioning of the tooth bud of the second premolar, The first premolar (2) has erupted rapidly
ox, O.M. & 0.1). .l uly,
Fig.
Pig.
1. Fnilurc
2. Failure
of eruption
of
eruption
of teeth
due to lack
of teeth
of sufficient.
due to malpositioning
spam~.
of the
tooth
Imtl.
1964
Volume Number
Den,tigerous
18 1
cysts.
II
57
and has drifted posteriorly. Only the coronal portion of the second premolar is formed and is lying in a distoangular position with a normal crypt, shown by arrows. Should a dentigerous cyst develop in any one of these areas, the only way it can be detected early is by means of the roentgenogram, as this condition is asymptomatic, especially in its early stages. In the advanced stages of the dentigerous cyst’s development, however, there are certain clinical symptoms which are associated with these changes, such as a gradual increase of swelling of the jaw leading to facial asymmetry, pain, numbness due to pressure against a nerve related to the area, or changing position of the teeth adjacent to the dentigerous cyst. Therefore, the conditions associated with development of the dentigerous cyst can be classified on the basis of the roentgenographic findings, where the pericoronal roentgenolucency is or exceeds 2.5 mm. in width. CLASSIFICATION
OF DENTIGEROUS
CYSTS
A classification of dentigerous cysts was established on the basis of roentgenographic findings and is as follows: CLASS
I. DENTIGEROUS
CYST ASSOCIATED
WITH
COMPLETELY
UNERUPTED
TEETH
A. Dentigerous cyst associated with uneruyted teeth wh#osefailure to erupt is due to la,ck of space in the dental arch Fig. 3 shows a dentigerous cyst associated with an unerupted mandibular third molar whose failuse to erupt is due to lack of space in the mandible. This condition occurred when the crypt remaining on the posterior surface of the tooth developed into a cyst, and the pressure of the developmental process of the cyst has forced the tooth downward and forvvard. Extensive loss of bone in the ascending ramus is shown by arrows. Fig. ,4 shows a dentigerous cyst related to an unerupted maxillary
Fig.
Fig. Fig.
9. Dentigerous 4. Dentigerous
3.
F
4.
cyst associated with unerupted mandibular third cyst associated with unerupted maxillary canine.
molar.
03..
0.M. h 0.1’. .I 1ll.V. 1964
canine whose failure to erupt is due to lack of sufficient space. The canine shadow is overlapping the lateral incisor root, and the cyst is pressing on t,he central incisor causing resorption of’ its root. Fig. 5 shows a dentigerous cyst related to an unerupted mandibular second premolar. The second deciduous molar is retained in place (uneruptcd) and is preventing eruption of the premolar. The permanent molars have migrated mesially and closed the space into which this tooth would have erupted. B. Dentiyerous cyst associated with uneruptd teeth whose to erupt is due to a malpositioninq oj’ the tooth germ
failure
Fig. 6 shows a dentigerous cyst surrounding the coronal portion of a completely unerupted mandibular third molar which is lying in a horizontal position. brrow 1 shows the cyst lying on the distal surface of the
Fig. 6.
A
dentigerous cyst associated
with
au
unerupted
mandihular
third
molar.
Volume Number
18 3
Fig. 7. A. dentigerous of maxilla.
cyst
surrounding
crown
of inverted
8. ,5 dentigerous
cyst
tooth
in midline
B.
A. Pig.
supcrnumcrary
related
to a supernumerary
mandibular
premolar.
crown. Arrow .2 shows the extension of the cyst, which is causing pressure on the second molar. Arrows 3 and 1 show the cyst extending downward to the base of the mandible, causing some pressure on the mandibular canal. Arrow 5 shows the effect of the cystic pressure changing t,he plane of occlusion of the lower second molar with its opponent in the maxillaqarch. C. Dentiyerous
cyst associated
with
unerupted
supernumerary
teeth
Fig. 7 shows a dentigerous c,yst surrounding the crown of an inverted supernumerary tooth in the midline of the maxilla. The permanent central incisor has been forced laterally and is superimposed over the permanent lateral incisor. Fig. 8, A shows an unerupted, undeveloped supernumerary mandibular premolar and the crypt surrounding the crown of the tooth. Fig. 8, B illustrates the same case, one year later, showing furt,her development of the crown and a rather extensive development of the crypt which has become a cystic area in a superior and mesial direction. During this period extensive restorations were placed, but the supernumerary tooth and the cyst, were ignored. CLASS
II. DENTIGEROUS
CYST
ASSOOCIATED
WITH
PARTIALLY
ERUPTED
TEETH
These teeth are partially erupted or have gone through a phase of eruption but, because of lack of space or malpositioning, are unable to complete the process of erupting. Dentigerous cysts are associated with these teeth in the same manner as with those in Class I but show variations in their location with respect to the crowns of these teeth.
OS.,
O.M. & O.P. July, 1964
Fig. 9, A. shows a dentipcrous cyst -formed beneath t,he crown of a partially erupted mandibular third molar which is lying in a horizont,al position. The cystic pressure has forrcd the apical port,ion of thcb scvont-I molar forward (I) which, in turn, has caused the crown to 10s~ its occlusal position (2) as seen in relation to the occlusal surfacr of t,hc first molar (3). Fig. 9, R shows an cstclnsive dentigerous cyst boncath the crown of a partially erupted mandibular third molar lying in a horizont,al posit,ion. The cystic prcswre has forced the third molar post clriorly (arrow 2) and caused an absorption of the distal root of the scvortd molar (arrow 2) .
Pig.
9. L)entigerous
cysts
associated
with
-partially
erupted
mxnrlilda~
tllirtl
~nolxr~.
This study emphasizes t,hc fact that the tecit,h that. arc more romn~only unerupted or impacted arc the ones that are more commonly associated with dentigerous cysts. Through the use of the roentgcnogram, the failure of these teeth to erupt-whether because of lack of sufficient space or because of malpositioning of the tooth bud-can be recognized early. The development of a dentigcrous cyst, with all its complications, can be kept under control. For this reason, the classification of dentigerous cysts on the basis of roentgenographic findings may help in early recognition of dentigerous cysts.
Volume Number
18 1
Dentigerozu
cysts.
II
61
SUMMARY In this study the importance of roentgenograms as a valuable means of early recognition of the dentigerous cyst has been pointed out. An attempt also has been made to classify dentigerous cysts on the basis of roentgenographic findings. CONCLUSIONS It has been emphasized that the areas in which the teeth arc more commonly unerupted are the areas in which we find the dentigerous cyst; this is due to the fact that the developmental crypk remain around the crowns of such teeth. The importance of the roentgenograms in establishing an early diagnosis of dentigerous cystic formation has been stressed so that the advanced stages of such a cystic condition with all its complications can be avoided through routine roentgenographic examination in those cases n-here clinical esamination shows delayed eruption of permanent teeth. It is then possible to remove the cyst while it is small. REFERENCES
1. Shafer, W. G., Hine, M. K., and Levy, B. M.: 1960, W. B. Saunders Company, pp. 176177. 2. Gillette, R., and Weinmann, J. P.: Extrafollicular
A Textbook Stages
of Oral
Pathology,
in Dentigerous
Cyst
Philadelphia, Development,
OEAL SURG., ORAL MED. & ORAL PATH. 11: 638, 1958. 3. Broca, P.: Traite des turners, Paris, 1869, P. Anselin, vol. 2, pp. 35-38. Pathological Anatomy, Prognosis and Therapy 4. Lartschneider, J. : Pathogenesis, lary Follicular Cysts, Dental Cosmos 71: 788-804, 1929. 5. Ries Centeno, G. A.: Dentigerous Cysts, J. Oral Surg. 2: 44-57, 1944. 6. Malassez, M. b.: Sur le role des debris epthelaux paradentaires, Arch. Physiol. 6: 379, 1885. 7. Sprawson, E.: Further Investigation of the Pathology of Dentigerous Cyst Treatment Based Thereon, Proc. Roy. Sot. Med. (Odontol. Sec.) 20: 67-78, 8. Bloch, J. K.: Follicular Cysts, Dental Cosmos 70: 708-711, 1928. 9. Mourshed, F.: A Roentgenographic Study of Dentigerous Cysts. I. Incidence tion Sample, ORAL Sum., ORAL MED. &ORAL PATE. 18: 47-53,1964.
of Maxil(3rd With 1927.
series) a Nelv
in a Popula-
Parodc illmushed, B.Ch.D., M&J.,* DEPARTMENT GRADUATE
T
OF SCHOOL
ORAL OF
ROENTGESOLOGY,
stages
Cairo, United Arab liepublic UNIVERSITY
OF
PENNSYLVANIA
MEDICINE
INTRODUCTION
he dentigerous cyst has been classified as an odontogenic cyst which originates through alterations of the reduced enamel epithelium after the crown of the tooth has been completely formed. Fluid accumulates either between the layers of the enamel epithelium or between this epithelium and the tooth crown.’ As for the origin of the dentigerous cyst,, there are two schools of thought.’ The first group is a proponent of an intrafollicular origin and regards the dentigerous cyst as a direct enlargement of the follicle surrounding the finished crown of an unerupted tooth.3-5 The intrafollicular changes are thought to be due to either inflammatory or mechanical disturbances occurring during tooth eruption. The second group favors an extrafollicular origin and suggests that at first, the cyst develops from cxtrafollicular epithelial remnants and then later unites with the follicle of an erupting tooth. 6-8However, the majority of opinions are in agreement with the theory of intrafollicular origin. In the first report in this series, an attempt was made to determine the incidence of dentigerous cyst in a population sample.” The purpose of the present study is to demonstrate t,he important role of rocntgenograms in detecting dentigerous cyst in the early stages. From a portion of a thesis prepared far the Mastrr of Science degree in Graduate School of Medicine, University of Pennsylvania. *Instructor, Oral Radiology Department, College of Dentistry, Cairo University; memhcr of the American Academy of Oral Roentgenology.
54
dentistry, active
Volume Number
18 1
Dentiyerous
cysts. II
55
METHODS AND MATERIALS Sixteen roentgenograms were used as the basis for this study of the devclopmental changes related t.o the formation of the dentigerous cyst. These roentgenograms were selected from the material available in the Oral Roentgenology Department of the University of Pennsylvania Dental School. RESULTSAND DISCUSSION The teeth develop within a crypt which exists prior to the beginning of enamel formation and calcification and remains around the crowns of the developing teeth until they have completely erupted. Therefore, it is only natural to find the crypts around the crowns of all unerupted teeth. The dentigerous cyst develops as a result of epithelial cell division causing pressure within the crypt, which results in liquefaction necrosis of the cells in the center of the mass.It is this cellular disturbance of the crypt (the cause of which is unknown) which leads to the formation of t,he dentigerous cyst. In time, the accumulation of fluid within the cyst might lead to the appearance of the typical clinical signs associated with t,he later stages of dentigerous cyst development. The most prevalent areas in which the teeth are more commonly found to be uneruptrd are, in order of frequency, the areas surrounding the mandibular third molars, t,he maxillary third molars, the maxillary canines, and the mandibular second premolars.g One of the important factors in the failure of these teeth to erupt in the four aforementioned areas is lack of sufficient space. However, the reason for this lack of space varies with the location of the area,s in the dental arch. In the mandibular and maxillary third molar areas and in the maxillary canine areas such lack of space is usually due to insufficient growt,h and expansion of the dental arch. In t,he mandibular second premolar areas, it is often caused by early loss of one or both of the deciduous molars. Fig. 1, ~1 showsa mandibular third molar tooth which failed to erupt because of lack of sufficient, space in the mandible. Fig. 1, B shows a mandibular second premolar which failed to erupt because of its tilted position and lack of space resulting from early loss of the deciduous molar. The tooth is fully developed; the crypt is enlarged, and possibly this is the beginning of dentigerous cyst formation. Fig. 1, C shows bilateral uneruptcd maxillary canines. Again, this is a case of insufficient space caused by lack of growth and expansion of t,he dental arch. The arrows point to the crypts which are still around the crowns of both teeth. The second important factor related t,o the failure of these teeth to erupt, is malpositioning of the teeth during development, causing them to assumea position in which subsequent eruption is impossible. Fig. 2, A shows an unerupted mandibular third mola,r; the tooth lies horizontally in the arch and cannot erupt in its position. Fig. 2, B shows a perpendicularly inverted mandibular third molar. Fig. 2, C shows t,wo mandibular mola.rs in a horizontal position, the crowns of both teeth facing each other. Fig. 2, D shows an unerupted mandibular second premo1a.r (2) and a posterior drifting of the first premolar. This condition is due to the early loss of the deciduous molars and malpositioning of the tooth bud of the second premolar, The first premolar (2) has erupted rapidly
ox, O.M. & 0.1). .l uly,
Fig.
Pig.
1. Fnilurc
2. Failure
of eruption
of
eruption
of teeth
due to lack
of teeth
of sufficient.
due to malpositioning
spam~.
of the
tooth
Imtl.
1964
Volume Number
Den,tigerous
18 1
cysts.
II
57
and has drifted posteriorly. Only the coronal portion of the second premolar is formed and is lying in a distoangular position with a normal crypt, shown by arrows. Should a dentigerous cyst develop in any one of these areas, the only way it can be detected early is by means of the roentgenogram, as this condition is asymptomatic, especially in its early stages. In the advanced stages of the dentigerous cyst’s development, however, there are certain clinical symptoms which are associated with these changes, such as a gradual increase of swelling of the jaw leading to facial asymmetry, pain, numbness due to pressure against a nerve related to the area, or changing position of the teeth adjacent to the dentigerous cyst. Therefore, the conditions associated with development of the dentigerous cyst can be classified on the basis of the roentgenographic findings, where the pericoronal roentgenolucency is or exceeds 2.5 mm. in width. CLASSIFICATION
OF DENTIGEROUS
CYSTS
A classification of dentigerous cysts was established on the basis of roentgenographic findings and is as follows: CLASS
I. DENTIGEROUS
CYST ASSOCIATED
WITH
COMPLETELY
UNERUPTED
TEETH
A. Dentigerous cyst associated with uneruyted teeth wh#osefailure to erupt is due to la,ck of space in the dental arch Fig. 3 shows a dentigerous cyst associated with an unerupted mandibular third molar whose failuse to erupt is due to lack of space in the mandible. This condition occurred when the crypt remaining on the posterior surface of the tooth developed into a cyst, and the pressure of the developmental process of the cyst has forced the tooth downward and forvvard. Extensive loss of bone in the ascending ramus is shown by arrows. Fig. ,4 shows a dentigerous cyst related to an unerupted maxillary
Fig.
Fig. Fig.
9. Dentigerous 4. Dentigerous
3.
F
4.
cyst associated with unerupted mandibular third cyst associated with unerupted maxillary canine.
molar.
03..
0.M. h 0.1’. .I 1ll.V. 1964
canine whose failure to erupt is due to lack of sufficient space. The canine shadow is overlapping the lateral incisor root, and the cyst is pressing on t,he central incisor causing resorption of’ its root. Fig. 5 shows a dentigerous cyst related to an unerupted mandibular second premolar. The second deciduous molar is retained in place (uneruptcd) and is preventing eruption of the premolar. The permanent molars have migrated mesially and closed the space into which this tooth would have erupted. B. Dentiyerous cyst associated with uneruptd teeth whose to erupt is due to a malpositioninq oj’ the tooth germ
failure
Fig. 6 shows a dentigerous cyst surrounding the coronal portion of a completely unerupted mandibular third molar which is lying in a horizontal position. brrow 1 shows the cyst lying on the distal surface of the
Fig. 6.
A
dentigerous cyst associated
with
au
unerupted
mandihular
third
molar.
Volume Number
18 3
Fig. 7. A. dentigerous of maxilla.
cyst
surrounding
crown
of inverted
8. ,5 dentigerous
cyst
tooth
in midline
B.
A. Pig.
supcrnumcrary
related
to a supernumerary
mandibular
premolar.
crown. Arrow .2 shows the extension of the cyst, which is causing pressure on the second molar. Arrows 3 and 1 show the cyst extending downward to the base of the mandible, causing some pressure on the mandibular canal. Arrow 5 shows the effect of the cystic pressure changing t,he plane of occlusion of the lower second molar with its opponent in the maxillaqarch. C. Dentiyerous
cyst associated
with
unerupted
supernumerary
teeth
Fig. 7 shows a dentigerous c,yst surrounding the crown of an inverted supernumerary tooth in the midline of the maxilla. The permanent central incisor has been forced laterally and is superimposed over the permanent lateral incisor. Fig. 8, A shows an unerupted, undeveloped supernumerary mandibular premolar and the crypt surrounding the crown of the tooth. Fig. 8, B illustrates the same case, one year later, showing furt,her development of the crown and a rather extensive development of the crypt which has become a cystic area in a superior and mesial direction. During this period extensive restorations were placed, but the supernumerary tooth and the cyst, were ignored. CLASS
II. DENTIGEROUS
CYST
ASSOOCIATED
WITH
PARTIALLY
ERUPTED
TEETH
These teeth are partially erupted or have gone through a phase of eruption but, because of lack of space or malpositioning, are unable to complete the process of erupting. Dentigerous cysts are associated with these teeth in the same manner as with those in Class I but show variations in their location with respect to the crowns of these teeth.
OS.,
O.M. & O.P. July, 1964
Fig. 9, A. shows a dentipcrous cyst -formed beneath t,he crown of a partially erupted mandibular third molar which is lying in a horizont,al position. The cystic pressure has forrcd the apical port,ion of thcb scvont-I molar forward (I) which, in turn, has caused the crown to 10s~ its occlusal position (2) as seen in relation to the occlusal surfacr of t,hc first molar (3). Fig. 9, R shows an cstclnsive dentigerous cyst boncath the crown of a partially erupted mandibular third molar lying in a horizont,al posit,ion. The cystic prcswre has forced the third molar post clriorly (arrow 2) and caused an absorption of the distal root of the scvortd molar (arrow 2) .
Pig.
9. L)entigerous
cysts
associated
with
-partially
erupted
mxnrlilda~
tllirtl
~nolxr~.
This study emphasizes t,hc fact that the tecit,h that. arc more romn~only unerupted or impacted arc the ones that are more commonly associated with dentigerous cysts. Through the use of the roentgcnogram, the failure of these teeth to erupt-whether because of lack of sufficient space or because of malpositioning of the tooth bud-can be recognized early. The development of a dentigcrous cyst, with all its complications, can be kept under control. For this reason, the classification of dentigerous cysts on the basis of roentgenographic findings may help in early recognition of dentigerous cysts.
Volume Number
18 1
Dentigerozu
cysts.
II
61
SUMMARY In this study the importance of roentgenograms as a valuable means of early recognition of the dentigerous cyst has been pointed out. An attempt also has been made to classify dentigerous cysts on the basis of roentgenographic findings. CONCLUSIONS It has been emphasized that the areas in which the teeth arc more commonly unerupted are the areas in which we find the dentigerous cyst; this is due to the fact that the developmental crypk remain around the crowns of such teeth. The importance of the roentgenograms in establishing an early diagnosis of dentigerous cystic formation has been stressed so that the advanced stages of such a cystic condition with all its complications can be avoided through routine roentgenographic examination in those cases n-here clinical esamination shows delayed eruption of permanent teeth. It is then possible to remove the cyst while it is small. REFERENCES
1. Shafer, W. G., Hine, M. K., and Levy, B. M.: 1960, W. B. Saunders Company, pp. 176177. 2. Gillette, R., and Weinmann, J. P.: Extrafollicular
A Textbook Stages
of Oral
Pathology,
in Dentigerous
Cyst
Philadelphia, Development,
OEAL SURG., ORAL MED. & ORAL PATH. 11: 638, 1958. 3. Broca, P.: Traite des turners, Paris, 1869, P. Anselin, vol. 2, pp. 35-38. Pathological Anatomy, Prognosis and Therapy 4. Lartschneider, J. : Pathogenesis, lary Follicular Cysts, Dental Cosmos 71: 788-804, 1929. 5. Ries Centeno, G. A.: Dentigerous Cysts, J. Oral Surg. 2: 44-57, 1944. 6. Malassez, M. b.: Sur le role des debris epthelaux paradentaires, Arch. Physiol. 6: 379, 1885. 7. Sprawson, E.: Further Investigation of the Pathology of Dentigerous Cyst Treatment Based Thereon, Proc. Roy. Sot. Med. (Odontol. Sec.) 20: 67-78, 8. Bloch, J. K.: Follicular Cysts, Dental Cosmos 70: 708-711, 1928. 9. Mourshed, F.: A Roentgenographic Study of Dentigerous Cysts. I. Incidence tion Sample, ORAL Sum., ORAL MED. &ORAL PATE. 18: 47-53,1964.
of Maxil(3rd With 1927.
series) a Nelv
in a Popula-