Original article
Morphodifferentiation and histodifferentiation of the dental hard tissues in connpound odontoma; a study of undemineralized material
Adriano Piattelli and Paolo Trisi Dental School, Uhiversify of Chieti, Italy
Piattelli A. Trisi P: Morphodiffcrcnliation and histodiffcrcntiation of the dental hard tissues in compound odontoma: a study of undemineralized material. J Oral Pathol Med 1992; 21: 340-2. Dental hard tissues and mineralization at the enamel .surface or in the ameloblastic epithelium were studied in 10 odontomas using undemineralized material. All the specimens showed a high degree of histo- and morphodifferentiation. Dcntin formed the bulk of the tumors. Much of the enamel was prismatic and apparently normal and in almost every specimen were present enamel tufts and spindles. At greater magnification it could be seen that the prisms had a very irregular orientation. Cementum was mostly acelluhir. Calcified material formed focally in the intercellular portion of the enamel epithelium: this material showed a concentric layers arrangement.
The compound odontoma is an agglomeration of small though morphologically recognizable teeth and is characterized by a high degree of histo- and morphodifferentiation. Specific studies of enamel in odontomas are very few (I). Much of the enamel is fully mineralized and thus in demineralized sections its participation in the lesion is indicated by the empty spaces that remain after its removal by dcmineralization. The demincralizing agents remove the mineralized tissues and thus not only do not allow an accurate assessment of the degree of mineralization but also determine the loss of the immediate neighboring cellular components and. incidentally, a change in the tintorial affinity of the tumor (2). The aim of the present investigation was to study dental hard tissues and mineralizations and calcifications associated with the odontogenic epithelium in odontomas. using thin ground sections.
the attached soft tissues were fixed, immediately upon removal, by immersion in \i)"A buffered formalin, dehydrated in an ascending series ol alcohols and
Key words: enamel; ghost cells; odontogenic tumor; odontoma. compound: teeth, hard
tissues A. Piattelli. Via F. Sciucchi 63. 1-66100 Chieti. Italy Accepted for publication March 6. 1992,
infiltrated and polymerized in Technovit 7200 VLC resin. The final preparation of the histologie slides was performed by the cutting-grinding technique (}).
Material and methods
Ten compound odontomas were used for the present study. The tumors with
Fig. I. Di.sorganized enamel prisms and aprismatic enamel. Basic luclisin X 400.
MeUiylene blue.
Differentiation of tissues in odonfoma 341 The thin (10 ^m) ground sections were stained with toluidine blue, basic fuchsin and mcthylcnc blue and were investigated with normal tran.smitted and polarized light. Results
All the specimens showed a high degree of histo- and morphodilTcientiation and in all ot" them it was possible to see a number of morphologically recognizable teeth. In most of the slides dentin formed the bulk of the tumor, and was covered by prismatic and apparently normal enamel. Around the tumors there were areas of llbroblastic connective tissue with groups of cubical or tlat epithelial cells: in some portions of the lesions the epithelial cells formed some structures resembling the enamel organ with an outer layer of cubical cells enelosing a central zone of stellate cells. The thickness of the enatncl was very variable. In some areas it was possible to observe the striae of Retzius; at an higher magniTication these striae were
observed to pass the prisms in a stepwise fashion along the cross striations. emphasizing the phasic organization of the enamel. The Huntcr-Schrcger lines were absent, probably due to the disordered arrangement of the prisms. In almost every specimen were present enamel tufts and spindles: sometimes it was possible to observe an enamel lamella, located in the outer part of the enamel. The disorderly arrangement of the enamel prisms caused the appearance of dark and light bands, irregularly spaced and organized: sometimes these bands traversed the enamel roughly in a fashion parallel to the outer enamel surface. At greater magnification it could be seen that the prisms had a very irregular orientation and that they were cut casually in a longitudinal or transversal way (Fig. 1). At the enamel surface the prisms had an even less regular orientation: in some areas the enamel was aprismatic. with various degrees of tnineralization. The areas with a low degree of mineralization had a basic staining and were more numerous in the tumors
that had not fully matured and in which the morphodifterentiation of the dental tissues was not yet complete (Fig. 2). Polarized light examination showed a non-homogenous light diffraction due to the disordered arrangement, irregular diameters and distortion in the enamel prisms outlines (Fig. 3). In the less organized odontomas. areas with a low mineralization of the enamel were very numerous and sometimes the staining property and the amount of the organic material present in these non-mineralized prisms was such that the prisms had a bone-like appearance. Perikymata have never been observed in our specimens. Cementum was mostly acellular. Enamel was covered by a flat epithelium one or two layers deep and by cells with long cytoplasmatic processes, similar to cells of the stellate reticulum. In the less differentiated odontomas areas of epithelial columnar or cuboid ameloblastlike cells were present with the nuclei in central position. Calcified material was seen to form focally in the intercellular portion of the enamel epitheliurn (Fig.
Fig. 2. IjuiiDcl prisms ;uc not a l u n y s coiiiplcR'h miiicrali/ed and it Is possible to soc an area stiongl\ staining with basic I'uchsin. x 200. Fig 3. Disorderly orlcruation of prisms cicalos non-liomogeneoiis liylu dinVaction. l o l u i d i n c blue, p o l a i i / e d light. \ 100. Fig. • / . . C o l u m n a r ameloblasts vvilli dysplasllc calcification siiirouiKled by epilhelial cells. Basic riiclisiii melh>lene blue, x 1000. Fig. >. Liesegang ring formation. Basic I'uclisin metlivlene bhie. x 1000.
342
PiATri:LLi & TRISI
4). These islands did not exhibit a typical enamel, dentin or cementum structure; they showed a concentric layers arrangement (Fig. 5). different staining properties, sometimes adhered to the enamel or dentin surface, while others were distinctly demareated from adjacent enamel and were located in the stromal connective tissue of the tumor, or in the central portion of the intermediate layer. Between crossed polars they showed a polarization cross, indicating a concentric structure. Some of these islands were in close contact with the epithelial cells of the intermediate layer: they looked less dense than neighboring hard dental tissues. Areas of so-called ghost cells could be found interspersed in the tissues of less differentiated odontomas. These cells showed different degrees of nuclear pyknosis and granular or clear cytoplasm. Many of the ghost cells underwent calcification or were embedded in an amyloid-like matrix. This matrix, however, blended into calcified globular structures like dysplastic enamel. Single intracytoplasmatic calcifications could be observed in some of these cells.
Discussion Studies on the morphology of the hard tissues forming a compound odontoma are very few. probably for the difficulties encountered in their microscopic examination. Previous research on the structure of the mineralized tissues in odontomas has been carried out with microradiography, x-ray microbeam diffraction and electron probe microanalysis (5). microradiography and SEM (I. 6). The recent introduction of a new technique (3) has made possible to obtain very thin (5-15 nm) slides of hard dental tissues where it has been possible to maintain a good structural relationship between the organic and inorganic components, to avoid the staining arti-
facts due to the use of acids, and to types of dysplastic calcifying cells proobtain a very good microscopic resolu- ducing two different tissues, other than normal dental mineralized tissue. tion of all the structures. In our opinion both these cells and Our results show a high degree of differentiation of the dental hard tissues cellular products derive from the enamel organ, in particular from the intermediin compound odontomas due probably to a correct interrelationship of the or- ate layer or from the stellate reticulum. ganizing influences between epithelium They could represent two different stagand mesenchymc. during the formation es of dysplastic epithelial ameloblastic of the denticles. cells. The cells of the intermediate layer or of the stellate reticulum of the enamel The altered enamel appearances that we have observed could be due to quali- organ, that arc normally quiescent, tative, quantitative and temporary mod- could give origin to these cells. ifications of the functions of the enamel Acknowledgements This work was in part organ with a difference in the mineralization and maturation of the amelo- supported by MURST (60%). blasts (6). The alterations of the enamel structure could be associated with variations in Mg content (5). In Ki-.Rt'Bi-t/s References study (1) the SEM enamel surface view, 1. KI:RI:III:I. LM. KI;RI:III;I. B. Dysplastic showing numerous prints of Tomes' enamel in odontoma: a light microscopprocesses, demonstrated the immaturity ic, microradiographic and SliM stvidy. J of the enamel found in odontomas. Oral Pathol 1984; 13: L17 46. 2. DoNAiii K. Zur Histologie dCs amelDysplastic calcified tissues in less difoblaslischcn l-pithels in gemischten und ferentiated odontomas present different zusamniengesel/cn Odontomen am Sadegrees of mineralization and organizagc-Dunnschliff. Dtsch y. Mnnd Kicfer tion. In our specimens we could observe Gcsichts Chir 19X4; 8: 206 10. two different kind of dysplastie calcified 3. DoNATM K. BRI:UNI:R G . A method Tor tissue. The first is similar to the rounded Ihe study of undecalcified bones and eoncentric calcification formed by Lieteeth with attached soil tissues. J Oral scgang's rings which have been found Pathol 1982; II: 318 25. by many investigators in odontoma. 4. MJ(')R 1A. PiNDiioRc; JJ. Histology of the CEOT, calcifying odontogenic cyst human tooth. Copenhagen: Munks(7-9). We observed these concentric forgaard. 1973: 7 12. 5. AoiiA T YosHioKA C. YACII T. Correlated mations in contact with the epithelial microradiography. X-ray microbeam difcells of the intermediate layer and of the fraction and electron probe microanalystellate reticulum of the enamel organ. sis of calcifications in an odontoma. J The concentric layers of these calcificaOral Pathol 1980; 9: 280 7. tions could represent a successive strati6. AHATI S, GARAITINI G . CARRASSI A: Osfication of calcifying material. servazioni niorlo-slriitturali al SEM in On the other hand we observed a different type of dysplastic calcified material without the appearance of concentrical layers; that seemed to derive from an amyloid-like material produced by the ghost cells. We also observed intracytoplasmatic calcification of these cells indicating that they could calcify completely and be substituted by dysplastic calcified materials. We can conclude that in odontoma there are two different
un caso di odontoma composto. Dent Cadmos 1988; 7: 50 8. 7. BAKNUS L. Surgical Pathology of the head atul neck. New York: Marcel Dekker. 1985: 1263 7/1346 9. 8. PREIN J. Ri:MAGt:N W. SPIHSSI, B . UtH-
i.iNUKR E. Atlas of tumors of the facial skeleton. Berlin: Springer Verlag. 1986: 54 9. 9. GARDNKR DG. DoRT LC. Dysplastie enamel in odontoma. Oral Surg Oral Med Oral Pathol 1979; 47: 238 46.
Morphodifferentiation and histodifferentiation of the dental hard tissues in connpound odontoma; a study of undemineralized material
Adriano Piattelli and Paolo Trisi Dental School, Uhiversify of Chieti, Italy
Piattelli A. Trisi P: Morphodiffcrcnliation and histodiffcrcntiation of the dental hard tissues in compound odontoma: a study of undemineralized material. J Oral Pathol Med 1992; 21: 340-2. Dental hard tissues and mineralization at the enamel .surface or in the ameloblastic epithelium were studied in 10 odontomas using undemineralized material. All the specimens showed a high degree of histo- and morphodifferentiation. Dcntin formed the bulk of the tumors. Much of the enamel was prismatic and apparently normal and in almost every specimen were present enamel tufts and spindles. At greater magnification it could be seen that the prisms had a very irregular orientation. Cementum was mostly acelluhir. Calcified material formed focally in the intercellular portion of the enamel epithelium: this material showed a concentric layers arrangement.
The compound odontoma is an agglomeration of small though morphologically recognizable teeth and is characterized by a high degree of histo- and morphodifferentiation. Specific studies of enamel in odontomas are very few (I). Much of the enamel is fully mineralized and thus in demineralized sections its participation in the lesion is indicated by the empty spaces that remain after its removal by dcmineralization. The demincralizing agents remove the mineralized tissues and thus not only do not allow an accurate assessment of the degree of mineralization but also determine the loss of the immediate neighboring cellular components and. incidentally, a change in the tintorial affinity of the tumor (2). The aim of the present investigation was to study dental hard tissues and mineralizations and calcifications associated with the odontogenic epithelium in odontomas. using thin ground sections.
the attached soft tissues were fixed, immediately upon removal, by immersion in \i)"A buffered formalin, dehydrated in an ascending series ol alcohols and
Key words: enamel; ghost cells; odontogenic tumor; odontoma. compound: teeth, hard
tissues A. Piattelli. Via F. Sciucchi 63. 1-66100 Chieti. Italy Accepted for publication March 6. 1992,
infiltrated and polymerized in Technovit 7200 VLC resin. The final preparation of the histologie slides was performed by the cutting-grinding technique (}).
Material and methods
Ten compound odontomas were used for the present study. The tumors with
Fig. I. Di.sorganized enamel prisms and aprismatic enamel. Basic luclisin X 400.
MeUiylene blue.
Differentiation of tissues in odonfoma 341 The thin (10 ^m) ground sections were stained with toluidine blue, basic fuchsin and mcthylcnc blue and were investigated with normal tran.smitted and polarized light. Results
All the specimens showed a high degree of histo- and morphodilTcientiation and in all ot" them it was possible to see a number of morphologically recognizable teeth. In most of the slides dentin formed the bulk of the tumor, and was covered by prismatic and apparently normal enamel. Around the tumors there were areas of llbroblastic connective tissue with groups of cubical or tlat epithelial cells: in some portions of the lesions the epithelial cells formed some structures resembling the enamel organ with an outer layer of cubical cells enelosing a central zone of stellate cells. The thickness of the enatncl was very variable. In some areas it was possible to observe the striae of Retzius; at an higher magniTication these striae were
observed to pass the prisms in a stepwise fashion along the cross striations. emphasizing the phasic organization of the enamel. The Huntcr-Schrcger lines were absent, probably due to the disordered arrangement of the prisms. In almost every specimen were present enamel tufts and spindles: sometimes it was possible to observe an enamel lamella, located in the outer part of the enamel. The disorderly arrangement of the enamel prisms caused the appearance of dark and light bands, irregularly spaced and organized: sometimes these bands traversed the enamel roughly in a fashion parallel to the outer enamel surface. At greater magnification it could be seen that the prisms had a very irregular orientation and that they were cut casually in a longitudinal or transversal way (Fig. 1). At the enamel surface the prisms had an even less regular orientation: in some areas the enamel was aprismatic. with various degrees of tnineralization. The areas with a low degree of mineralization had a basic staining and were more numerous in the tumors
that had not fully matured and in which the morphodifterentiation of the dental tissues was not yet complete (Fig. 2). Polarized light examination showed a non-homogenous light diffraction due to the disordered arrangement, irregular diameters and distortion in the enamel prisms outlines (Fig. 3). In the less organized odontomas. areas with a low mineralization of the enamel were very numerous and sometimes the staining property and the amount of the organic material present in these non-mineralized prisms was such that the prisms had a bone-like appearance. Perikymata have never been observed in our specimens. Cementum was mostly acellular. Enamel was covered by a flat epithelium one or two layers deep and by cells with long cytoplasmatic processes, similar to cells of the stellate reticulum. In the less differentiated odontomas areas of epithelial columnar or cuboid ameloblastlike cells were present with the nuclei in central position. Calcified material was seen to form focally in the intercellular portion of the enamel epitheliurn (Fig.
Fig. 2. IjuiiDcl prisms ;uc not a l u n y s coiiiplcR'h miiicrali/ed and it Is possible to soc an area stiongl\ staining with basic I'uchsin. x 200. Fig 3. Disorderly orlcruation of prisms cicalos non-liomogeneoiis liylu dinVaction. l o l u i d i n c blue, p o l a i i / e d light. \ 100. Fig. • / . . C o l u m n a r ameloblasts vvilli dysplasllc calcification siiirouiKled by epilhelial cells. Basic riiclisiii melh>lene blue, x 1000. Fig. >. Liesegang ring formation. Basic I'uclisin metlivlene bhie. x 1000.
342
PiATri:LLi & TRISI
4). These islands did not exhibit a typical enamel, dentin or cementum structure; they showed a concentric layers arrangement (Fig. 5). different staining properties, sometimes adhered to the enamel or dentin surface, while others were distinctly demareated from adjacent enamel and were located in the stromal connective tissue of the tumor, or in the central portion of the intermediate layer. Between crossed polars they showed a polarization cross, indicating a concentric structure. Some of these islands were in close contact with the epithelial cells of the intermediate layer: they looked less dense than neighboring hard dental tissues. Areas of so-called ghost cells could be found interspersed in the tissues of less differentiated odontomas. These cells showed different degrees of nuclear pyknosis and granular or clear cytoplasm. Many of the ghost cells underwent calcification or were embedded in an amyloid-like matrix. This matrix, however, blended into calcified globular structures like dysplastic enamel. Single intracytoplasmatic calcifications could be observed in some of these cells.
Discussion Studies on the morphology of the hard tissues forming a compound odontoma are very few. probably for the difficulties encountered in their microscopic examination. Previous research on the structure of the mineralized tissues in odontomas has been carried out with microradiography, x-ray microbeam diffraction and electron probe microanalysis (5). microradiography and SEM (I. 6). The recent introduction of a new technique (3) has made possible to obtain very thin (5-15 nm) slides of hard dental tissues where it has been possible to maintain a good structural relationship between the organic and inorganic components, to avoid the staining arti-
facts due to the use of acids, and to types of dysplastic calcifying cells proobtain a very good microscopic resolu- ducing two different tissues, other than normal dental mineralized tissue. tion of all the structures. In our opinion both these cells and Our results show a high degree of differentiation of the dental hard tissues cellular products derive from the enamel organ, in particular from the intermediin compound odontomas due probably to a correct interrelationship of the or- ate layer or from the stellate reticulum. ganizing influences between epithelium They could represent two different stagand mesenchymc. during the formation es of dysplastic epithelial ameloblastic of the denticles. cells. The cells of the intermediate layer or of the stellate reticulum of the enamel The altered enamel appearances that we have observed could be due to quali- organ, that arc normally quiescent, tative, quantitative and temporary mod- could give origin to these cells. ifications of the functions of the enamel Acknowledgements This work was in part organ with a difference in the mineralization and maturation of the amelo- supported by MURST (60%). blasts (6). The alterations of the enamel structure could be associated with variations in Mg content (5). In Ki-.Rt'Bi-t/s References study (1) the SEM enamel surface view, 1. KI:RI:III:I. LM. KI;RI:III;I. B. Dysplastic showing numerous prints of Tomes' enamel in odontoma: a light microscopprocesses, demonstrated the immaturity ic, microradiographic and SliM stvidy. J of the enamel found in odontomas. Oral Pathol 1984; 13: L17 46. 2. DoNAiii K. Zur Histologie dCs amelDysplastic calcified tissues in less difoblaslischcn l-pithels in gemischten und ferentiated odontomas present different zusamniengesel/cn Odontomen am Sadegrees of mineralization and organizagc-Dunnschliff. Dtsch y. Mnnd Kicfer tion. In our specimens we could observe Gcsichts Chir 19X4; 8: 206 10. two different kind of dysplastie calcified 3. DoNATM K. BRI:UNI:R G . A method Tor tissue. The first is similar to the rounded Ihe study of undecalcified bones and eoncentric calcification formed by Lieteeth with attached soil tissues. J Oral scgang's rings which have been found Pathol 1982; II: 318 25. by many investigators in odontoma. 4. MJ(')R 1A. PiNDiioRc; JJ. Histology of the CEOT, calcifying odontogenic cyst human tooth. Copenhagen: Munks(7-9). We observed these concentric forgaard. 1973: 7 12. 5. AoiiA T YosHioKA C. YACII T. Correlated mations in contact with the epithelial microradiography. X-ray microbeam difcells of the intermediate layer and of the fraction and electron probe microanalystellate reticulum of the enamel organ. sis of calcifications in an odontoma. J The concentric layers of these calcificaOral Pathol 1980; 9: 280 7. tions could represent a successive strati6. AHATI S, GARAITINI G . CARRASSI A: Osfication of calcifying material. servazioni niorlo-slriitturali al SEM in On the other hand we observed a different type of dysplastic calcified material without the appearance of concentrical layers; that seemed to derive from an amyloid-like material produced by the ghost cells. We also observed intracytoplasmatic calcification of these cells indicating that they could calcify completely and be substituted by dysplastic calcified materials. We can conclude that in odontoma there are two different
un caso di odontoma composto. Dent Cadmos 1988; 7: 50 8. 7. BAKNUS L. Surgical Pathology of the head atul neck. New York: Marcel Dekker. 1985: 1263 7/1346 9. 8. PREIN J. Ri:MAGt:N W. SPIHSSI, B . UtH-
i.iNUKR E. Atlas of tumors of the facial skeleton. Berlin: Springer Verlag. 1986: 54 9. 9. GARDNKR DG. DoRT LC. Dysplastie enamel in odontoma. Oral Surg Oral Med Oral Pathol 1979; 47: 238 46.
