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Etiology and vascularization of dental lamina cysts
Etiology and vascularization of dental lamina cysts William P. Maher, B.X., D.D.S.,x and P. P. Swindle, B.S., A.B., A.M., Ph.D.,** Milwaukee, Wis. MARQUETTE
UNIVERSITY
SCHOOL
OF DENTISTRY
I
t is believed that dental lamina cysts may arise from unresorbed and enclaved epithelial remnants of the dental lamina. Dental lamina cysts in the maxillary and mandibular dental ridges of the newborn infant may be histologically differentiated fsom enclaved epithelial fragments that may give rise to cysts at points of fusion of the palatomaxillary processes. Cysts derived from unresorbed epithelial fragments of the dental lamina are odontogenic epidermal fissural cysts. It is known that cysts of this class are lined with stratified squamous epithelium, sometimes with dental epithelium, or occasionally with various combinations of these cell types. It might be expected that if the retained epithelial fragments of the dental lamina were nearer to the oral epithelium the future cyst would be lined with stratified squamous epithe1iu.m. If the enclaved fragments were nearer to a developing tooth, however, it might be expected that the future cyst would be lined with a mixture of stratified squamous epithelium and dental epithelium. It could be assumed that, because of the proximity of some enclaved cells of the dental lamina to a developing tooth, at least a few cells might possess some eha,racteristics of hard dental structures. Consequently, upon maturation of the enclaved mass of cells, some histologic features of the enclavement may resemble dentine or enamel, or combinations of the various cell types may give rise to pearllike structures. Cysts situated along the palatal midline are nonodontogenic epidermal fissural cysts that arise from enclaved epithelium at points of fusion where the This study was supported by Research Grant of Dental Research, United States Public Health Grant from Marquette University. *Research Associate, Department of Anatomy. **Emeritus Professor of Physiology.
590
ZROl-DE-01093 Service, and
from the National by an Institutional
Institute Intramural
Volume 29 Number 4
Dental
law&u
cysts
591
palatomaxillary processes of the embryonic face fuse. It is known that cysts along the midpalatal suture are lined with stratified squamous epithelium, some!times with pseudostratified ciliated columnar epithelium, and sometimes with combinations of these cell types.l We hare reported the early development and further growth of fissural cysts at the palatal midline and their blood s~pply.~ The present report pertains to the early development and further growth of dental lamina cysts and thcil* blood supply. In a special attempt to clarify alleged confusion and possible misnomers concerning cysts that arise from enclaved epithelinm and also aberrant develop-ing mucous glands or their ducts in the palate and in the dental ridges, Fromm:~ reported observations from his histologic studies of inclusion cysts in these areas. AcrordinF to his judgment, three types have been clarified, as :follows : 1. Epstein’s pearls-Cysts that arise from trapped epithelium at the median raphe of the palate. 2. Bohn’s nodules--Cysts that arise from remnants of mucous glands located on the crests of the dental ridges and in the palate away from the midline. 3. Dental lamina cysts-Cysts that arise from remnants of the dental lamina in the crests of the dental ridges. Fromm presents photomicrographs (Figs. 4 and 5 in his report) clepieting Bohn’s nodules in histologic section at high and low magnification. He states in the legends that mucous glands and ducts are present,. However, UY arc not convinced that mucous type acini or ducts arc shown in the photomicrographs. According to Fromm, Bohn’s nodules on the crests of the dental ridges a.rc’ characterized by the presence of mucous glands, mucous ducts, acini, or remnants of these structures in the vicinity of one or more encluved massesot’ epithelium. We are fully aware of the presence of mucous glands in the palate, and XV(I do not overlook the possibility that mucous glands may develop ec+opicaIl.y itI and about, the vicinity of the crests of the dent.al ridges. Enclaved fragments of epithelium at the palatal midline may dcvclop into cysts, but their development a.nd growth are quite independent of mucous glands. However, mucous glands or their ducts in the palatal area may bccornc- intclrposed between two, or more than two, cysts ; consequently, the mucous glands or their ducts may be condensed or deranged as a result of pressure caused by unusual growth of the epithelial inclusions. In our opinion, unresorbed strands of dental lamina may resemble tubes or ducts in hist,ologic section, and these structures may be interposed among clusters of microcysts that develop from unresorbecl fragments of dental lamina. In a labiolingual section through the lower incisor region at the cap and bell stages of odontogenesis, the dental lamina appears to consist of a double strand of basal epithelium. At the cap stage, the connection of the dental lamina wit,11 that of the gingival epithelium is labial to the developing tooth and somewhat in the vicinity of the lip furrow band. In a sagittal section through the head during the bell stage of odontogenesis, it can be demonstrated that the gingival
592
Maher
and
Swkdle
Oral -4pri1,
Surg. 1970
Fig. P. Sketches illustrating cap and bell stages of odontogenesis as seen in IabiolinguaI section in the vicinity of the lower incisor region. Many details were omitted from the sketches for purposes of convenience. Some details that illustrate the apparent shift of the dental lamina, due mainly to differences in the labial portions of the dental ridge, are represented. (Drawn from photomicrographs depicting histologic features of odontogenesis as illustrated in Orban’s Textbook of Oral Histology and Embryology.4)
connection of the dental lamina is lingual to the developing dental structure in the mandible and palatal to the dental structures in the maxilla. The dental lamina, as seen in labiolingual section, divides the dental ridge into labial and lingual portions in the mandible and labial and palatal portions in the maxilla. The apparent shift of the dental lamina relative to dental structures is due mainly to differences in rates of growth between the two portions of the dental ridge. The spatial relationship of the dental lamina to a developing lower incisor at the cap and bell stages of odontogenesis is illustrated in four sketches (Fig. 1). Incidentally, these sketches were drawn from photomicrographs depicting cap and bell stages of odontogenesis as illustrated in Orban’s Textbook of Oral Histology and Embryotogy.4 Some effects resulting from the shift of the dental lamina due to differences in rates of growth of the two portions of the dental ridge are as follows: 1. The labial portion of the dental ridge grows against the lingual portion and over the dental structures to form the incisal and occlusal gingival pads in the maxillary and mandibular dental arches (Figs. 2 and 3). 2. Some cells destined to become mucous glands in the lip may become ectopically situated in the area of the future gingiva during a very early period in the development of the vestibular lamina. Then, as the
Volume 29 Number
4
E
Pig. i. Oral view of palatogingival mucoperiosteum in human fetus, approximately I m. Bone removed. Blood vessels injected with India ink. The slight swellings in t.anc the crest of the ridge are the individual gingival pads. The black line palatal t.o borthr of lgrval pads is due to superimposition of many ink-filled vessels at the labial atogingival groove. Fig. 3. Same palatomucoperiosteal tissue as illustrated in Fig. 2. The enlargement, is f ) left anterior portion of the dental ridge and vicinity. The labial portion of the dc: go forms the gingival pads. The gingival pads of the central and lateral incisors and lpid are clearly indicated. The blood vessels that nourish the dental ridge arise ma Nrn branches of vessels from the lips and cheeks.
labial portion of the dental ridge grow over tlic dental structures, ihe cells ordinarily destined to become mucous glands in the lip may instead give rise to cysts on the dental ridges. This hypothetical considerat,ion describing the origin of mucous gland cysts embedded in the crests of the dental ridges requires further histologic evaluation. 3. The anlage of the permanent tooth consistently develops lingually
594
Maher
and
Swindle
Oral April,
Fig. 4. Human fetus, approximately mid-term, showing a portion of the maxillary dental ridge. At least eight odontogenic epidermal fissural cysts in linear arrangement about the crest of the ridge are depicted. Blood vessels not injected, bone not removed, cleared. Photographed from the oral surface.
Surg. 1970
left at or tissues
or palatally in relation to its deciduous predecessor in the mandibular and maxillary dental arches. 4. Fragments of the dental lamina may become aborted or delaminated and subsequently may be resorbed completely or may become enclaved in the connective tissues of the labial portion of the dental ridge. Clinical examination of the dental ridges of the newborn infant reveals that dental lamina cysts, when present, are sometimes labial to the crest of the ridge and sometimes lingual to it. The various locations of these cysts suggest that fragments of the dental lamina were aborted at different times during growth of the labial portion of the dental ridge. 5. Blood vessels of the labial portion of the crest of the dental ridge arise mainly from branches of vessels that extend into the area from the lips and cheeks (Fig. 3). To improve opportunities for analysis of the arrangement of arteries, veins, and blood capillaries in the vicinity of the dental lamina, we injected the blood vessels of the hea.d and neck region with Higgins black India ink variously diluted with tap water. The blood vessels became filled via a cannula inserted into the ascending thoracic aorta. A 30 C.C. syringe was attached to the eannula and, by manual operation of the syringe, the injection medium was urged into the blood vascular system. The upper and lower jaws were removed from each
Volume 29 Yurder
5
of many fetuses thus injected, and then each necropsy was cleased by a Xpalteholz method. Subsequent to the clearing process, all bone was removed from the palatogingival mucoperiosteum by microdissection while the tissnos were completely immersed in synthetic oil of wintergreen. The complexity oi the arrangement of the blood vessels in the palatogingival mucoperiosteurn is illustrated in Figs. 2 and 3. Topographic examination of the palatogingival mucoperiosteum of IIUI~C~~~I.IS fetuses of various ages reveals the presence of a groove extending from a point. in the anterior palate at or near the anterior palatine papilla. The groove c’stends somewhat parallel to the denta. arch and somewhat palatally to the crest of the dental ridge. We have interpreted this groove as being the oral portion of the dental lamina. The deeper portions of this groove, as commonly pictnrccl in cross section, are generally designated as dental lamina. In the mid-term fetus we found that, by careful probing, the groove may bc widened so that its opposite walls may be examined with the aid of a stcrcomicroscope. We found that the topography of its walls consist of epithelial ridges and papillae. Furthermore, we have observed that there is epithclial fusion between opposite walls, spotwise, throughout the depth of the groovtl. The foregoing examinations were made upon noncleared palates. Stereomicroscopic examination of cleared pslatcs in which the blood vessels were not injected revealed, in some instances, the prescncc of cysts in lineal arrangement at the crest of the maxillary dental ridge, as illustrated in lOig. 4. Also, we found that the epithelial inclusions vary in size and that they III~J. be at various depths in the connective tissues. Prior to the time the dental lamina becomes resorbed, it functions as a barrier to the development of blood vessels. Spotwise resorption throughout its length creates opportunities for blood vessels to pass from the palatal area into the labial portion of the dental ridge, and vice versa. Blood vessels in t.hc vicinity of unresorbed fragments of the dental lamina may become nutrient to the fragments of epithelium, just as other vessels are nutrient to basal cells of the gingival epithelium. Proliferation of the enclaved cells increases the size of tile mass, and further growth results in a condensation of the conncctivc lissue peripheral to it. Blood \*essels are contained in the condensed portion of the connective tissue. The condensed portion of the connective tissue peripheral to the growing cyst is known as the connective tissue capsule. At least three cysts with their nourishing blood vessels which originate from the palatal nct~vork are illustrated in Fig. 5. Arteries, veins, and blood capillaries in the connective tissue capsule of at least three cysts palatal to the dental ridge are illust.ratcd in Fig. 6. There is a remarkable similarity in the cvcnts of development and growth of fissural cysts at the palatal midline and cysts that develop from unresorbcd fragments of the dental lamina. Should it bc possible to define the dental lamina as an epithelial fissure, then we might classify dental lamina cysts as cysts of a. fissural type. Moreover, the dental la.mina participates in the odontogenic processes. These cysts, therefore, should be classified as odontogenic epidcl~mal fissural cysts.
596
Maher
and
Swindle
Oral April,
Surg. 1970
Fig.
Fig. 5. Human fetus, near term. Blood vessels injected with India ink. At least three cysts on the palatal side of the dental ridge in the vicinity of the incisor teeth and their nourishing blood vessels from the palatal network are illustrated. Fig. 6. Human fetus, near term. Capillaries and other small blood vessels in the connective tissue capsules of at least three cysts palatal to the maxillary dental ridge in the vicinity of the anterior teeth are shown.
Fromm3 states that inclusion cysts on the maxillary and mandibular dental arches are not true epithelial cysts but are remnants of the dental lamina. In our judgment, the term “nonodontogenic fissural cyst” is a more descriptive term to apply to cysts that arise from enclaved epithelial fragments at points of fusion of the palatomaxillary processesthan is the term “Epstein’s pearls.” Similarly, the term “odontogenic epidermal fissural cyst” more accurately describes cysts that arise from enclaved remnants of the dental lamina than does the term “Bohn’s nodules.” Fig. 7 shows at least ten microcysts which presumably resulted from epi-
Volume Number
29 4
Pig. 7. Human fetus, approximntcl~ mid-tr>vru. Postrrior portion of palatal midline. ,X1. Icast ten microcysts (nonodontogmic e~tictermal fissural qsts) presum~tl~Iy resulting from cnclsved epithdium at points of fusion of the palatornnsiliar,v proct’ss(‘s. Blood ~~sntds roof: injected, hone not, rt~movcd, tissues cleared. Phottrgrnpl~ctl from t I\(, oral surfac-e.
thelial enclavemenbs at points of fusion of the palat,omasillary processes. Fig. 1 shows at least eight microcysts in linear arrangement at the crest of a segment of the maxillary dental ridge. The blood ~essrls are not injected in either of the two cleared tissue preparations. The photographs in each case were made from the oral surface while the tissues were completely immersed in synthetic oil of wintergrccn. Appropriate combinations of transmitted and reflected light were used. REFERENCES
1. Cohen, M. M.: Fissural Cysts of the Median Palatine Sdure, Amer. J. Orthodont. 6c Oral Surg. 29: 442, 1943. 2. Swindle, P. F., and Maher, W. P.: Blood Vessels of Median Palatal Fissural Cysls, ORAL SURG. 27: 36!, 1969. 3. Fromm, A.: Epstem’s Pearls, Bohn’s Nodules and Inclusion Cysts of the Oral Cavity, J. Dent. Child. 24: 275, 1967. Embryology, ed. 6, St. Louis, 1966, 4. Sicher, H. (editor): Orban’s Oral Histology and The C. V. Mosby Company (Figs. 15, 16, 18, and 21).
UNIVERSITY
SCHOOL
OF DENTISTRY
I
t is believed that dental lamina cysts may arise from unresorbed and enclaved epithelial remnants of the dental lamina. Dental lamina cysts in the maxillary and mandibular dental ridges of the newborn infant may be histologically differentiated fsom enclaved epithelial fragments that may give rise to cysts at points of fusion of the palatomaxillary processes. Cysts derived from unresorbed epithelial fragments of the dental lamina are odontogenic epidermal fissural cysts. It is known that cysts of this class are lined with stratified squamous epithelium, sometimes with dental epithelium, or occasionally with various combinations of these cell types. It might be expected that if the retained epithelial fragments of the dental lamina were nearer to the oral epithelium the future cyst would be lined with stratified squamous epithe1iu.m. If the enclaved fragments were nearer to a developing tooth, however, it might be expected that the future cyst would be lined with a mixture of stratified squamous epithelium and dental epithelium. It could be assumed that, because of the proximity of some enclaved cells of the dental lamina to a developing tooth, at least a few cells might possess some eha,racteristics of hard dental structures. Consequently, upon maturation of the enclaved mass of cells, some histologic features of the enclavement may resemble dentine or enamel, or combinations of the various cell types may give rise to pearllike structures. Cysts situated along the palatal midline are nonodontogenic epidermal fissural cysts that arise from enclaved epithelium at points of fusion where the This study was supported by Research Grant of Dental Research, United States Public Health Grant from Marquette University. *Research Associate, Department of Anatomy. **Emeritus Professor of Physiology.
590
ZROl-DE-01093 Service, and
from the National by an Institutional
Institute Intramural
Volume 29 Number 4
Dental
law&u
cysts
591
palatomaxillary processes of the embryonic face fuse. It is known that cysts along the midpalatal suture are lined with stratified squamous epithelium, some!times with pseudostratified ciliated columnar epithelium, and sometimes with combinations of these cell types.l We hare reported the early development and further growth of fissural cysts at the palatal midline and their blood s~pply.~ The present report pertains to the early development and further growth of dental lamina cysts and thcil* blood supply. In a special attempt to clarify alleged confusion and possible misnomers concerning cysts that arise from enclaved epithelinm and also aberrant develop-ing mucous glands or their ducts in the palate and in the dental ridges, Fromm:~ reported observations from his histologic studies of inclusion cysts in these areas. AcrordinF to his judgment, three types have been clarified, as :follows : 1. Epstein’s pearls-Cysts that arise from trapped epithelium at the median raphe of the palate. 2. Bohn’s nodules--Cysts that arise from remnants of mucous glands located on the crests of the dental ridges and in the palate away from the midline. 3. Dental lamina cysts-Cysts that arise from remnants of the dental lamina in the crests of the dental ridges. Fromm presents photomicrographs (Figs. 4 and 5 in his report) clepieting Bohn’s nodules in histologic section at high and low magnification. He states in the legends that mucous glands and ducts are present,. However, UY arc not convinced that mucous type acini or ducts arc shown in the photomicrographs. According to Fromm, Bohn’s nodules on the crests of the dental ridges a.rc’ characterized by the presence of mucous glands, mucous ducts, acini, or remnants of these structures in the vicinity of one or more encluved massesot’ epithelium. We are fully aware of the presence of mucous glands in the palate, and XV(I do not overlook the possibility that mucous glands may develop ec+opicaIl.y itI and about, the vicinity of the crests of the dent.al ridges. Enclaved fragments of epithelium at the palatal midline may dcvclop into cysts, but their development a.nd growth are quite independent of mucous glands. However, mucous glands or their ducts in the palatal area may bccornc- intclrposed between two, or more than two, cysts ; consequently, the mucous glands or their ducts may be condensed or deranged as a result of pressure caused by unusual growth of the epithelial inclusions. In our opinion, unresorbed strands of dental lamina may resemble tubes or ducts in hist,ologic section, and these structures may be interposed among clusters of microcysts that develop from unresorbecl fragments of dental lamina. In a labiolingual section through the lower incisor region at the cap and bell stages of odontogenesis, the dental lamina appears to consist of a double strand of basal epithelium. At the cap stage, the connection of the dental lamina wit,11 that of the gingival epithelium is labial to the developing tooth and somewhat in the vicinity of the lip furrow band. In a sagittal section through the head during the bell stage of odontogenesis, it can be demonstrated that the gingival
592
Maher
and
Swkdle
Oral -4pri1,
Surg. 1970
Fig. P. Sketches illustrating cap and bell stages of odontogenesis as seen in IabiolinguaI section in the vicinity of the lower incisor region. Many details were omitted from the sketches for purposes of convenience. Some details that illustrate the apparent shift of the dental lamina, due mainly to differences in the labial portions of the dental ridge, are represented. (Drawn from photomicrographs depicting histologic features of odontogenesis as illustrated in Orban’s Textbook of Oral Histology and Embryology.4)
connection of the dental lamina is lingual to the developing dental structure in the mandible and palatal to the dental structures in the maxilla. The dental lamina, as seen in labiolingual section, divides the dental ridge into labial and lingual portions in the mandible and labial and palatal portions in the maxilla. The apparent shift of the dental lamina relative to dental structures is due mainly to differences in rates of growth between the two portions of the dental ridge. The spatial relationship of the dental lamina to a developing lower incisor at the cap and bell stages of odontogenesis is illustrated in four sketches (Fig. 1). Incidentally, these sketches were drawn from photomicrographs depicting cap and bell stages of odontogenesis as illustrated in Orban’s Textbook of Oral Histology and Embryotogy.4 Some effects resulting from the shift of the dental lamina due to differences in rates of growth of the two portions of the dental ridge are as follows: 1. The labial portion of the dental ridge grows against the lingual portion and over the dental structures to form the incisal and occlusal gingival pads in the maxillary and mandibular dental arches (Figs. 2 and 3). 2. Some cells destined to become mucous glands in the lip may become ectopically situated in the area of the future gingiva during a very early period in the development of the vestibular lamina. Then, as the
Volume 29 Number
4
E
Pig. i. Oral view of palatogingival mucoperiosteum in human fetus, approximately I m. Bone removed. Blood vessels injected with India ink. The slight swellings in t.anc the crest of the ridge are the individual gingival pads. The black line palatal t.o borthr of lgrval pads is due to superimposition of many ink-filled vessels at the labial atogingival groove. Fig. 3. Same palatomucoperiosteal tissue as illustrated in Fig. 2. The enlargement, is f ) left anterior portion of the dental ridge and vicinity. The labial portion of the dc: go forms the gingival pads. The gingival pads of the central and lateral incisors and lpid are clearly indicated. The blood vessels that nourish the dental ridge arise ma Nrn branches of vessels from the lips and cheeks.
labial portion of the dental ridge grow over tlic dental structures, ihe cells ordinarily destined to become mucous glands in the lip may instead give rise to cysts on the dental ridges. This hypothetical considerat,ion describing the origin of mucous gland cysts embedded in the crests of the dental ridges requires further histologic evaluation. 3. The anlage of the permanent tooth consistently develops lingually
594
Maher
and
Swindle
Oral April,
Fig. 4. Human fetus, approximately mid-term, showing a portion of the maxillary dental ridge. At least eight odontogenic epidermal fissural cysts in linear arrangement about the crest of the ridge are depicted. Blood vessels not injected, bone not removed, cleared. Photographed from the oral surface.
Surg. 1970
left at or tissues
or palatally in relation to its deciduous predecessor in the mandibular and maxillary dental arches. 4. Fragments of the dental lamina may become aborted or delaminated and subsequently may be resorbed completely or may become enclaved in the connective tissues of the labial portion of the dental ridge. Clinical examination of the dental ridges of the newborn infant reveals that dental lamina cysts, when present, are sometimes labial to the crest of the ridge and sometimes lingual to it. The various locations of these cysts suggest that fragments of the dental lamina were aborted at different times during growth of the labial portion of the dental ridge. 5. Blood vessels of the labial portion of the crest of the dental ridge arise mainly from branches of vessels that extend into the area from the lips and cheeks (Fig. 3). To improve opportunities for analysis of the arrangement of arteries, veins, and blood capillaries in the vicinity of the dental lamina, we injected the blood vessels of the hea.d and neck region with Higgins black India ink variously diluted with tap water. The blood vessels became filled via a cannula inserted into the ascending thoracic aorta. A 30 C.C. syringe was attached to the eannula and, by manual operation of the syringe, the injection medium was urged into the blood vascular system. The upper and lower jaws were removed from each
Volume 29 Yurder
5
of many fetuses thus injected, and then each necropsy was cleased by a Xpalteholz method. Subsequent to the clearing process, all bone was removed from the palatogingival mucoperiosteum by microdissection while the tissnos were completely immersed in synthetic oil of wintergreen. The complexity oi the arrangement of the blood vessels in the palatogingival mucoperiosteurn is illustrated in Figs. 2 and 3. Topographic examination of the palatogingival mucoperiosteum of IIUI~C~~~I.IS fetuses of various ages reveals the presence of a groove extending from a point. in the anterior palate at or near the anterior palatine papilla. The groove c’stends somewhat parallel to the denta. arch and somewhat palatally to the crest of the dental ridge. We have interpreted this groove as being the oral portion of the dental lamina. The deeper portions of this groove, as commonly pictnrccl in cross section, are generally designated as dental lamina. In the mid-term fetus we found that, by careful probing, the groove may bc widened so that its opposite walls may be examined with the aid of a stcrcomicroscope. We found that the topography of its walls consist of epithelial ridges and papillae. Furthermore, we have observed that there is epithclial fusion between opposite walls, spotwise, throughout the depth of the groovtl. The foregoing examinations were made upon noncleared palates. Stereomicroscopic examination of cleared pslatcs in which the blood vessels were not injected revealed, in some instances, the prescncc of cysts in lineal arrangement at the crest of the maxillary dental ridge, as illustrated in lOig. 4. Also, we found that the epithelial inclusions vary in size and that they III~J. be at various depths in the connective tissues. Prior to the time the dental lamina becomes resorbed, it functions as a barrier to the development of blood vessels. Spotwise resorption throughout its length creates opportunities for blood vessels to pass from the palatal area into the labial portion of the dental ridge, and vice versa. Blood vessels in t.hc vicinity of unresorbed fragments of the dental lamina may become nutrient to the fragments of epithelium, just as other vessels are nutrient to basal cells of the gingival epithelium. Proliferation of the enclaved cells increases the size of tile mass, and further growth results in a condensation of the conncctivc lissue peripheral to it. Blood \*essels are contained in the condensed portion of the connective tissue. The condensed portion of the connective tissue peripheral to the growing cyst is known as the connective tissue capsule. At least three cysts with their nourishing blood vessels which originate from the palatal nct~vork are illustrated in Fig. 5. Arteries, veins, and blood capillaries in the connective tissue capsule of at least three cysts palatal to the dental ridge are illust.ratcd in Fig. 6. There is a remarkable similarity in the cvcnts of development and growth of fissural cysts at the palatal midline and cysts that develop from unresorbcd fragments of the dental lamina. Should it bc possible to define the dental lamina as an epithelial fissure, then we might classify dental lamina cysts as cysts of a. fissural type. Moreover, the dental la.mina participates in the odontogenic processes. These cysts, therefore, should be classified as odontogenic epidcl~mal fissural cysts.
596
Maher
and
Swindle
Oral April,
Surg. 1970
Fig.
Fig. 5. Human fetus, near term. Blood vessels injected with India ink. At least three cysts on the palatal side of the dental ridge in the vicinity of the incisor teeth and their nourishing blood vessels from the palatal network are illustrated. Fig. 6. Human fetus, near term. Capillaries and other small blood vessels in the connective tissue capsules of at least three cysts palatal to the maxillary dental ridge in the vicinity of the anterior teeth are shown.
Fromm3 states that inclusion cysts on the maxillary and mandibular dental arches are not true epithelial cysts but are remnants of the dental lamina. In our judgment, the term “nonodontogenic fissural cyst” is a more descriptive term to apply to cysts that arise from enclaved epithelial fragments at points of fusion of the palatomaxillary processesthan is the term “Epstein’s pearls.” Similarly, the term “odontogenic epidermal fissural cyst” more accurately describes cysts that arise from enclaved remnants of the dental lamina than does the term “Bohn’s nodules.” Fig. 7 shows at least ten microcysts which presumably resulted from epi-
Volume Number
29 4
Pig. 7. Human fetus, approximntcl~ mid-tr>vru. Postrrior portion of palatal midline. ,X1. Icast ten microcysts (nonodontogmic e~tictermal fissural qsts) presum~tl~Iy resulting from cnclsved epithdium at points of fusion of the palatornnsiliar,v proct’ss(‘s. Blood ~~sntds roof: injected, hone not, rt~movcd, tissues cleared. Phottrgrnpl~ctl from t I\(, oral surfac-e.
thelial enclavemenbs at points of fusion of the palat,omasillary processes. Fig. 1 shows at least eight microcysts in linear arrangement at the crest of a segment of the maxillary dental ridge. The blood ~essrls are not injected in either of the two cleared tissue preparations. The photographs in each case were made from the oral surface while the tissues were completely immersed in synthetic oil of wintergrccn. Appropriate combinations of transmitted and reflected light were used. REFERENCES
1. Cohen, M. M.: Fissural Cysts of the Median Palatine Sdure, Amer. J. Orthodont. 6c Oral Surg. 29: 442, 1943. 2. Swindle, P. F., and Maher, W. P.: Blood Vessels of Median Palatal Fissural Cysls, ORAL SURG. 27: 36!, 1969. 3. Fromm, A.: Epstem’s Pearls, Bohn’s Nodules and Inclusion Cysts of the Oral Cavity, J. Dent. Child. 24: 275, 1967. Embryology, ed. 6, St. Louis, 1966, 4. Sicher, H. (editor): Orban’s Oral Histology and The C. V. Mosby Company (Figs. 15, 16, 18, and 21).