BDNF/TrkB/Akt Signaling Pathway Epithelial Odontogenic Tumors and Keratocyst: An Immunohistochemical Study Comparative With Dental Germs

Odontogenic lesions (OL) are an important group of oral and maxillofacial diseases represented by odontogenic cysts, benign, and malignant tumors. The brain-derived neurotrophic factor (BDNF)/ tropomyosin receptor kinase B (TrkB) signaling pathway has multiple biological actions and has been identified as an important pathway in the proliferation, invasion, and survival of different epithelial tumors. Its role in the development of OL, however, has so far been unexplored. Our aim was to evaluate the BDNF/TrkB/Akt/p-RPS6 signaling pathway in OL of epithelial origin. This cross-sectional study comprised 3 cases of tooth germs, 25 cases of odontogenic keratocyst (OK), 29 cases of ameloblastoma (Am), and 6 cases of ameloblastic carcinoma. Immunohistochemical staining for BDNF, TrkB, p-Akt, and p-RPS6 was performed. OLs were evaluated according to the pattern of immunohistochemical expression in epithelial cells and by semiquantitative scores that considered the intensity of staining and percentage of positive cells. BDNF stromal expression was also assessed. No significant differences were observed with respect to the percentage of positive cases for all markers. Regarding the immunoreactive scores, BDNF and p-RPS6 expressions were similar in the odontogenic epithelium of all OL. However, TrkB and p-Akt were overexpressed in OK compared with ameloblastic carcinoma. In Am, epithelial BDNF was significantly higher compared with stromal expression. In conclusion, BDNF seems to participate in the development of cystic, benign, and malignant odontogenic epithelium to similar degrees. The acquisition of the invasive or malignant phenotype in odontogenic neoplasms is not associated with alterations in the BDNF/TrkB/Akt/RPS6 axis, which could be implicated in the differentiation process.

C-Jun N-terminal kinase (JNK) pathway activation is essential for dental papilla cells polarization

During tooth development, dental papilla cells differentiate into odontoblasts with polarized morphology and cell function. Our previous study indicated that the C-Jun N-terminal kinase (JNK) pathway regulates human dental papilla cell adhesion, migration, and formation of focal adhesion complexes. The aim of this study was to further examine the role of the JNK pathway in dental papilla cell polarity formation. Histological staining, qPCR, and Western Blot suggested the activation of JNK signaling in polarized mouse dental papilla tissue. After performing an in vitro tooth germ organ culture and cell culture, we found that JNK inhibitor SP600125 postponed tooth germ development and reduced the polarization, migration and differentiation of mouse dental papilla cells (mDPCs). Next, we screened up-regulated polarity-related genes during dental papilla development and mDPCs or A11 differentiation. We found that Prickle3, Golga2, Golga5, and RhoA were all up-regulated, which is consistent with JNK signaling activation. Further, constitutively active RhoA mutant (RhoA Q63L) partly rescued the inhibition of SP600125 on cell differentiation and polarity formation of mDPCs. To sum up, this study suggests that JNK signaling has a positive role in the formation of dental papilla cell polarization.

The Dentin Matrix Protein 1 (Dmp1) is Specifically Expressed in Mineralized, but not Soft, Tissues during Development

Dentin Matrix Protein 1 ( Dmp1) was originally identified from dentin. However, its expression and function in vivo are not clear. To clarify these two issues, we have generated mice carrying a truncated Dmp1 gene by using gene targeting to replace exon 6 with a lacZ gene. Northern blot analysis shows the expected 5.8-kb Dmp1-lacZ fusion transcript and loss of the wild-type 2.8-kb Dmp1 transcript, confirmed by a lack of immunostaining for the protein. Using heterozygous animals, we demonstrate that Dmp1 is specific for mineralized tissues. Not previously shown, Dmp1 is also expressed in pulp cells. Dmp1-deficient embryos and newborns display no apparent gross abnormal phenotype, although there are a modest expansion of the hypertrophic chondrocyte zone and a modest increase in the long bone diameter. This suggests that DMP1 is not essential for early mouse skeletal or dental development.

Circadian Rhythm Regulates Development of Enamel in Mouse Mandibular First Molar

Rhythmic incremental growth lines and the presence of melatonin receptors were discovered in tooth enamel, suggesting possible role of circadian rhythm. We therefore hypothesized that circadian rhythm may regulate enamel formation through melatonin receptors. To test this hypothesis, we examined expression of melatonin receptors (MTs) and amelogenin (AMELX), a maker of enamel formation, during tooth germ development in mouse. Using qRT-PCR and immunocytochemistry, we found that mRNA and protein levels of both MTs and AMELX in normal mandibular first molar tooth germs increased gradually after birth, peaked at 3 or 4 day postnatal, and then decreased. Expression of MTs and AMELX by immunocytochemistry was significantly delayed in neonatal mice raised in all-dark or all-light environment as well as the enamel development. Furthermore, development of tooth enamel was also delayed showing significant immature histology in those animals, especially for newborn mice raised in all daylight condition. Interestingly, disruption in circadian rhythm in pregnant mice also resulted in delayed enamel development in their babies. Treatment with melatonin receptor antagonist 4P-PDOT in pregnant mice caused underexpression of MTs and AMELX associated with long-lasting deficiency in baby enamel tissue. Electromicroscopic evidence demonstrated increased necrosis and poor enamel mineralization in ameloblasts. The above results suggest that circadian rhythm is important for normal enamel development at both pre- and postnatal stages. Melatonin receptors were partly responsible for the regulation.

Immunohistochemical Expression of GLUT-1 and HIF-1α in Tooth Germ, Ameloblastoma, and Ameloblastic Carcinoma

Hypoxia-inducible factor-1α (HIF-1α) promotes proteins that enable cell survival during hypoxia, such as glucose transporter 1 (GLUT-1). Their coexpression has been associated with aggressiveness in malignancies and has not been studied in odontogenic tumors. Immunohistochemical expression of HIF-1α and GLUT-1 was analyzed in 13 tooth germs (TGs), 55 ameloblastomas (AMs), and 3 ameloblastic carcinomas (ACs). HIF-1α was negative in all TGs, and just 1 case of AM and 1 of AC had nuclear positivity. GLUT-1 expressed in ameloblastic cells of all TGs, AMs, and ACs, with an increasing intensity, respectively, and was significantly higher in solid AM than in unicystic AM (P = .041). Absence of nuclear HIF-1α in TGs and most AMs suggest that GLUT-1 may be induced by alternative pathways to hypoxia. However, in ACs, HIF-1α may be activated; however, to confirm this, additional cases are needed. GLUT-1 overexpression could be related to aggressiveness in AMs and ACs and must represent a normal metabolite in TGs.

An unusual association of extraoral sinus tract with unerupted permanent tooth

Cases have been reported in the literature in which extraoral sinus tracts of dental origin have been diagnosed and successfully treated. Similarly, the presence of an intracoronal radiolucency in unerupted permanent teeth has been found in the dental literature. The association of one with the other, however, is a rare occurrence. The purpose of this case report was to describe the treatment of a 7-year-old child who presented with an extraoral draining sinus originating from a carious, developing tooth bud of the unerupted permanent mandibular left second molar. After a thorough clinical and radiographic examination, a conclusive diagnosis was determined and surgical treatment was performed. The patient responded well, and the cutaneous lesion healed uneventfully.

An amelogenin mutation leads to disruption of the odontogenic apparatus and aberrant expression of Notch1

BACKGROUND

Amelogenins are highly conserved proteins secreted by ameloblasts in the dental organ of developing teeth. These proteins regulate dental enamel thickness and structure in humans and mice. Mice that express an amelogenin transgene with a P70T mutation (TgP70T) develop abnormal epithelial proliferation in an amelogenin null (KO) background. Some of these cellular masses have the appearance of proliferating stratum intermedium, which is the layer adjacent to the ameloblasts in unerupted teeth. As Notch proteins are thought to constitute the developmental switch that separates ameloblasts from stratum intermedium, these signaling proteins were evaluated in normal and proliferating tissues.

METHODS

Mandibles were dissected for histology and immunohistochemistry using Notch1 antibodies. Molar teeth were dissected for western blotting and RT-PCR for evaluation of Notch levels through imaging and statistical analyses.

RESULTS

Notch1 was immunolocalized to ameloblasts of TgP70TKO mice, KO ameloblasts stained, but less strongly, and wild-type teeth had minimal staining. Cells within the proliferating epithelial cell masses were positive for Notch1 and had an appearance reminiscent of calcifying epithelial odontogenic tumor with amyloid-like deposits. Notch1 protein and mRNA were elevated in molar teeth from TgP70TKO mice.

CONCLUSION

Expression of TgP70T leads to abnormal structures in mandibles and maxillae of mice with the KO genetic background and these mice have elevated levels of Notch 1 in developing molars. As cells within the masses also express transgenic amelogenins, development of the abnormal proliferations suggests communication between amelogenin producing cells and the proliferating cells, dependent on the presence of the mutated amelogenin protein.

The effect of retinoic acid on mouse mandibular molar development in vitro, using alkaline phosphatase as a molecular indicator of differentiation

INTRODUCTION

An excellent model system that links evolutionary biology and developmental biology in seeking to understand evolutionary diversity is the study of tooth development in mammals. These studies reflect the diversity of mammalian radiations which bear on the interpretation of South African fossil hominids. Tooth development occurs via epithelio-mesenchymal interactions and involves the production of many substances, including alkaline phosphatase, which is necessary for dentine and enamel formation. Retinoic acid is a known morphogen and is important in tooth development. In excess, retinoic acid has been found to alter the formation of teeth.

OBJECTIVES

In order to determine whether retinoic acid has any effect on tooth morphology, exogenous retinoic acid was administered to developing mouse molar teeth in vitro, and alkaline phosphatase was utilized as an indicator of differentiation.

METHODS

Molars were microdissected from 15.5 day mouse embryo mandibles and cultured at the air: medium interface with or without retinoic acid for seven days. Following fixation and embedding, the explants were sectioned for morphological analysis. Alkaline phosphatase activity was detected using a modified Gomori's histochemical method.

RESULTS AND CONCLUSION

Retinoic acid appeared to retard the growth and differentiation of the molar explants. This was coincident with reduced alkaline phosphatase.

Immunohistochemical detection of uPA, uPAR, PAI-1, and maspin in ameloblastic tumors

BACKGROUND

To evaluate the roles of extracellular matrix (ECM)-degrading serine proteinase in progression of odontogenic tumors, expression of urokinase-type plasminogen activator (uPA), uPA receptor (uPAR), plasminogen activator inhibitor-1 (PAI-1), and maspin was analyzed in ameloblastic tumors as well as in tooth germs.

METHODS

Tissue specimens of 10 tooth germs, 45 ameloblastomas, and 5 malignant ameloblastic tumors were examined immunohistochemically with the use of antibodies against uPA, uPAR, PAI-1, and maspin.

RESULTS

Immunohistochemical reactivity for uPA, uPAR, PAI-1, and maspin was detected in normal and neoplastic odontogenic tissues: uPA was recognized predominantly in mesenchymal cells, uPAR was evident in epithelial cells, PAI-1 was found in both epithelial and mesenchymal cells, and maspin was expressed only in epithelial cells. The levels of uPA and uPAR immunoreactivity in ameloblastic tumors were slightly higher than the levels in tooth germs, while PAI-1 reactivity in ameloblastomas tended to be lower than that in tooth germs. The level of maspin immunoreactivity in ameloblastomas was significantly higher than that in tooth germs, and ameloblastic carcinoma showed decreased maspin reactivity.

CONCLUSION

Expression of uPA, uPAR, PAI-1, and maspin in tooth germs and ameloblastic tumors suggests that interactions among these molecules contribute to ECM degradation and cell migration during tooth development and tumor progression. Altered expression of the serine proteinase and its associated molecules in ameloblastic tumors may be involved in oncogenesis of odontogenic epithelium.

Syndecan-1 and Wingless-type protein-1 in human ameloblastomas

BACKGROUND

Aberrant Wingless type 1 glycoprotein (Wnt) pathway in ameloblastomas and a role of syndecan-1 (SDC1) in activating Wnt signalling were perspected. SDC1 shifting from epithelium to stroma was reported in invasive non-odontogenic neoplasms. The aim of this study was to reveal the role of SDC1 and Wnt1 in intraosseous ameloblastomas (IA(s)).

METHODS

SDC1 and Wnt1 expressions were investigated in 29 ameloblastoma subtypes and seven tooth buds.

RESULTS

SDC1 immunostaining strongly depicted stromal cells, extracellular matrix (ECM) and basement membranes of ameloblastomas. It also showed epithelial tumour cells in the acanthomatous and plexiform subtypes, and it often occurred in stellate reticulum cells and basal ameloblasts of tooth buds. Parallel Wnt1 expression occurred in ameloblastomatous epithelial cells, but it was common in basal cells of tooth buds too. Statistically, a significant correlation was found between the percentage of IA(s)-bearing SDC1-positive stromal cells and ECM and the percentage of IA(s)-bearing Wnt1-positive epithelial cells.

CONCLUSIONS

A role of SDC1 in stromal cells and ECM can be hypothesized as a critical factor for carcinogenesis and local invasiveness of IA(s).

Claudins 1, 4, 5, 7 and occludin in ameloblastomas and developing human teeth

BACKGROUND

To analyze the distribution pattern of claudins 1, 4, 5, 7 and occludin in benign and malignant ameloblastomas and developing human teeth.

METHODS

Paraffin-embedded tissue specimens of 25 benign and four malignant ameloblastomas and two developing human teeth were examined immunohistochemically using antibodies against claudins 1, 4, 5, 7 and occludin.

RESULTS

In ameloblastomas strongest expression was seen for claudins 1 and 7 while claudin 4 was expressed less frequently. Claudin 5 and occludin were seen only in a minority of cases. There were no evident differences in the expression of claudins or occludin neither between different histologic subtypes of ameloblastomas nor between benign or malignant cases. The strongest expression for claudins was present in the central stellatum reticulum-like cells surrounding the microcysts and in the areas with squamous differentiation of the ameloblastomas. In developing teeth both claudin 1 and 7 stained strongly in the enamel epithelium, ameloblasts, and enamel matrix, but staining for claudin 4 was relatively weak. Claudin 5 was preferentially expressed only in vessels, and occludin staining ranged from negative to weak in ameloblastomas and teeth germs.

CONCLUSION

There were no clear differences in the expression levels between benign and malignant ameloblastic tumors. The overexpression of claudins in the areas with microcyst formation may indicate their attempt to maintain the interepithelial cohesion of the cells. The strong immunoreactivity of ameloblasts and newly synthesized enamel matrix for claudins 1 and 7 indicates that they may be involved in cell signaling influencing enamel formation.

Adenomatoid dentinoma or adenomatoid odontogenic hamartoma: what is the better term to denominate this uncommon odontogenic lesion?

We report two cases of an uncommon odontogenic lesion, previously described as adenomatoid dentinoma. They were well-circumscribed unilocular radiolucent lesions exhibiting discrete radiopacities, located in the left mandibular third molar region. Microscopically they were composed of odontogenic hard and soft tissues, similar to a dental germ. Dental papilla and dentin were easily identified. Odontogenic epithelium formed adenomatoid-like structures, and by scanning electron microscopy a layer of enamel was seen in contact with the dentin. Based on these clinical, radiographic, histological and electron microscopical features we proposed the diagnosis of adenomatoid odontogenic hamartoma. Treatment consisted of surgical removal, and no recurrence was observed. In our opinion all similar cases previously reported pertain to the same spectrum of this lesion and thus should be named as suggested above. Moreover, ultrastructural observations using 5 microm sections can be useful to better characterize the presence of hard tissues.

Loss of permanent mandibular lateral incisor and canine tooth buds through extraoral sinus: report of a case

Extraoral sinus tract may occur as a result of an inflammatory process associated with the necrotic pulp. Several non odontogenic disorders may also produce an extraoral sinus tract, the differential diagnosis of these clinical findings is of prime importance in providing appropriate clinical care. Presented here is a case report of 4 year old female child with extraoral sinus tract through which the tooth buds of mandibular permanent left lateral incisor and mandibular permanent left canine were lost. The extraoral sinus was due to mandibular left primary canine with class IX fracture (Ellis and Davey's classification).

Expression of bone morphogenetic proteins and their associated molecules in ameloblastomas and adenomatoid odontogenic tumors

OBJECTIVE

To further clarify the roles of regulators of embryonic development, bone morphogenetic protein (BMPs) and their associated molecules, in oncogenesis and cytodifferentiation of odontogenic tumors, the expression of these regulator molecules were analyzed in epithelial odontogenic tumors as well as in tooth germs.

MATERIALS AND METHODS

Tooth germs, ameloblastomas, adenomatoid odontogenic tumors, and malignant ameloblastomas were examined by RT-PCR and immunohistochemistry for detection of BMP-2, -4, -7, BMP receptors I and II (BMPR-I, BMPR-II), core-binding factor alpha1 (CBFA1), and osterix.

RESULTS

mRNA expression of BMPs, BMPRs, CBFA1, and osterix was detected in all odontogenic tissues. Immunohistochemical reactivity for BMPs, BMPRs, and CBFA1 was detected in both epithelial and mesenchymal cells of tooth germs and epithelial odontogenic tumors. BMPs and BMPRs were evidently expressed in odontogenic epithelial cells in tooth germs and epithelial odontogenic tumors. Acanthomatous ameloblastomas showed increased BMP-7 reactivity in keratinizing cells. Nuclear CBFA1 expression was detected scatteredly in odontogenic epithelial cells in normal and neoplastic odontogenic tissues, as well as in some mesenchymal cells in tooth germs and in some stromal cells in epithelial odontogenic tumors. Ameloblastic carcinomas showed low reactivity for BMPs, BMPRs, and CBFA1.

CONCLUSION

BMPs and their associated molecules might play a role in cytodifferentiation of normal and neoplastic odontogenic epithelium via epithelial-mesenchymal interactions.

EGF-R and erbB-2 in murine tooth development after ethanol exposure

BACKGROUND

Alcohol consumption during pregnancy can frequently lead to a congenital disorder known as fetal alcohol syndrome (FAS); however, not all children born to alcoholic women develop FAS. Alcohol consumption may affect diverse organs and systems during embryonic development, including craniofacial structures. Small teeth, enamel alterations, and delayed eruption have been observed after ethanol exposure. Epidermal growth factor receptors (EGF-Rs) participate in dental proliferation and differentiation, and changes in these receptors were considered here to be a likely mechanism associated to the dental anomalies observed in this syndrome. Epidermal growth factor receptor type 1 (EGF-R) and epidermal growth factor receptor type 2 (erbB-2) immunoexpression during the lower first molar morphogenesis was investigated in mouse fetuses exposed to ethanol during gestation.

METHODS

Pregnant female mice were divided into groups, consuming either 5, 10, 15, 20, or 25% ethanol solutions, or water (control group). Heads were obtained from 16.5- and 18.5-day fetuses. Immunohistochemistry was applied to EGF-R and erbB-2.

RESULTS

At days 16.5 and 18.5, fetuses from 15%, 20%, and 25% ethanol groups showed delayed differentiation, degenerative changes in dental epithelial tissues and reduced dental size; additionally, they displayed an enhanced immunoreactivity to EGF-R and erbB-2.

CONCLUSIONS

Our results suggest that ethanol consumption during pregnancy affects the expression of EGF receptors and induces a delay in murine fetal dental morphogenesis. Dental development is a process that involves a number of growth factors; hence we consider that further research is required to show whether the changes in glycosylation and growth-factor signaling pathways observed in other cells are also involved in the alterations observed in this study.

STR-genotyping from human medieval tooth and bone samples

We extracted the DNA contained in samples of bones and teeth from 10 skeletons excavated from the Gravette site (400-1000 AD, south of France). Ancient DNA was analysed by autosomal short tandem repeats (STRs). The DNA present in these ancient remains appeared very degraded, but nevertheless, better conserved in tooth than in bone samples. Moreover, we showed that the DNA extracted from ancient dental pulp was not exempt from polymerase chain reaction (PCR) inhibitors, which could result from extreme DNA fragmentation. An adapted protocol with a supplementary step of purification removed this inhibition.

Effects of maternal ethanol intake on immunoexpression of epidermal growth factor in developing rat mandibular molar

OBJECTIVE

A polyclonal antibody was used to investigate the effects of ethanol ingestion before and during pregnancy, in the expression of EGF on dentinogenesis and amelogenesis of rat mandibular first molar.

DESIGN

Ethanol was administered to drinking water (treated group) starting at concentrations of 1% and increasing weekly to 5, 10, 15, 20 and 25% (v/v). During week 7, these rats were mated and continued to receive the 25% alcoholic solution, up to delivery. The control group received tap water. On postnatal days 0, 4 and 9, two offspring of each litter were killed, their hemimandibles removed and prepared for paraffin processing and immunohistochemistry.

RESULTS

At postnatal day 0 the EGF immunoreactivity of the inner enamel epithelium and presecretory ameloblasts was weak when compared to controls. At postnatal day 4 EGF immunoreactivity of the secretory ameloblasts and odontoblasts was only moderate compared to controls. At postnatal day 9 EGF staining of the ameloblasts was weak when compared to controls.

CONCLUSIONS

These results suggest that, maternal alcoholism interferes with EGF expression during initial dentinogenesis and amelogenesis and in the secretion and maturation of the dentin and enamel, therefore, which may cause a reduction of dentin and enamel formation.

[Tooth bud fixation by the material LitAr]

The results of the biotransformation investigation of the material LitAr after replacing through it the cystectomy area for the fixation of the permanent tooth rudiment are given here. The conversion process of the material LitAr into the bone tissue was checked roentgenologically and with the use of magnetic resonance image (MRI). In accordance with the MRI data all the bone tissue formation marks have been stated in 2 months after implanting the material LitAr into the rudiment fixation area. All the further observations (up to 10 months) have shown the bone tissue formation which was accompanied by cutting the tooth in the correct position and on time.

Accelerated bone formation and increased osteoblast number contribute to the abnormal tooth germ development in parathyroid hormone-related protein knockout mice

Our previous study showed that tooth germs at late embryonic stage [later than embryonic day 17.5 (E17.5)] and neonatal homozygous parathyroid hormone-related protein (PTHrP)-knockout mice are compressed or penetrated by the surrounding alveolar bone tissue. In vivo and in vitro studies have shown that the development of the tooth germ proper is not disturbed, but insufficient alveolar bone resorption, due to the decreased number and hypofunction of osteoclasts, is the main cause of this abnormality. In addition to the insufficient alveolar bone resorption, progressive bone formation toward tooth germs was observed in homozygous mice, suggesting that accelerated bone formation also contributes to this abnormality. To further investigate this, homozygous mice at E14.0 and E15.5, when alveolar bone is forming, were used for histochemical and bone histomorphometric analyses. In contrast to the late embryonic stage, the alveolar bone did not yet compress developing tooth germs in homozygous mice on E14.0, but a larger amount of bone tissue was seen compared to wild-type littermates. Histomorphometric analysis of bone at E14.0 revealed that the osteoblast numbers and surfaces in the mandibles and in the bone collar of femora of homozygous mice were significantly higher than those of wild-type mice. However, unlike our previous study showing the osteoclast surface on E18.5 in homozygous mice to be significantly lower than that of wild-type mice, this study at E14.0 showed no significant difference between the two genotypes. To evaluate the amount of calcification around tooth germs, 3D images of mandibles were reconstructed from the calcein-labeled sections of the wild-type and mutant mice. Labeling was performed at E14.0, and the mice were sacrificed 1 h after the calcein injection to minimize the effect of bone resorption. Comparison of the 3D images revealed that the labeled surface was larger around developing tooth germs in homozygous mouse than in wild-type mouse. On day E15.5, osteoblasts approached the enamel organ of homozygous mice but this was not observed in wild-type mice. In this study, we report a systemic increase in osteoblast number and accelerated bone formation in homozygous PTHrP-knockout mice, both of which contribute to the abnormal tooth development.

Expression of integrin subunits alpha2, alpha3, alpha5, alphav, beta1, beta3 and beta4 in different histological types of ameloblastoma compared with dental germ, dental lamina and adult lining epithelium

OBJECTIVE

To analyze integrin expression and distribution in different histological types of ameloblastoma, compared with dental germ, dental lamina and adult lining epithelium.

MATERIALS AND METHODS

Three-micrometer sections from paraffin-embedded specimens were evaluated employing a streptavidin-biotin immunohistochemical method and anti-integrin alpha2, alpha3, alpha5, alphav, beta1, beta3 and beta4 antibodies.

RESULTS

All integrins were present in all specimens, exhibiting different patterns. In follicular ameloblastoma, the integrin staining was stronger in the periphery while integrin alpha2 was not present in the central cells. Acanthomatous ameloblastoma showed a similar pattern, with positive staining for integrins alpha3, alpha5, alphav, beta1 and beta4 in the metaplastic cells. In the unicystic, integrin staining was uniform except for integrins alpha5 and beta3 which showed weaker staining in the upper layers. In the plexiform ameloblastoma, dental germ and lamina integrin staining was uniform. In the adult lining epithelium, staining for integrins alpha2, alpha5 and beta4 was confined to the basal layer, while integrins alphav and beta3 were present in the basal and parabasal, with integrins alpha3 and beta1 in the upper layers.

CONCLUSION

Acanthomatous, follicular and unicystic ameloblastomas showed integrin staining patterns similar to the adult lining epithelium while the plexiform ameloblastoma was similar to the dental germ and lamina.

Continuous tooth replacement: the possible involvement of epithelial stem cells

Epithelial stem cells have been identified in integumental structures such as hairs and continuously growing teeth of various rodents, and in the gut. Here we propose the involvement of epithelial stem cells in the continuous tooth replacement that characterizes non-mammalian vertebrates, as exemplified by the zebrafish. Arguments are based on morphological observations of tooth renewal in the zebrafish and on the similarities between molecular control of hair and tooth formation. Dissection of the molecular cascades underlying the regulation of the epithelial stem cell niche might open perspectives for new regenerative treatment strategies in clinical dentistry.

Recruitment of osteoclasts in the mandible of osteopetrotic (op/op) mice

Osteoclasts in osteopetrotic (op/op) mice are substantially reduced by the absence of functional activities of macrophage colony-stimulating factor (M-CSF). However, it is known that osteoclasts appear in op/op skeletal bones with aging, although the molecular mechanism for this is unknown. In order to investigate osteoclastic recruitment in the jaw bones of op/op mice, osteoclastic distribution was analysed for 2 yr after birth by histochemistry for tartrate-resistant acid phosphatase activity and immunohistochemistry for cathepsin K. Osteoclasts in op/op mandibular bones decreased rapidly in number after birth and disappeared by 3 d, although there was no difference in the osteoclastic distribution between op/op and normal littermates at birth. At 2 wk, osteoclasts began to reappear around op/op tooth germs, where no apparent connective tissue layer intervened between tooth germs and bone trabeculae. They increased in number and were scattered over the mandible, reaching a maximum at 8 wk, when periodontal ligament-like structures were recognizable around incisor germs. Osteoclasts then again decreased gradually, and after 62 wk few osteoclasts were seen in op/op mandibular bones, whose marrow space disappeared. These findings suggest that osteoclasts are recruited in an M-CSF-independent manner in op/op mandibles, especially in areas around tooth germs.

Influence of aging on tooth eruption: experimental canine mandibular allograft

PURPOSE

Aging is clinically related to tooth eruption; however, there are no known studies that have elucidated the relationship. We examined whether tooth eruption would occur normally in a mature subject.

MATERIALS AND METHODS

Using vascularized composite tissue mandibular transplantation, we extracted portions of immature mandibles including the tooth germs from young beagle dogs and placed them into unrelated immature and mature beagle dogs. We then examined eruption of the lower first molar in the grafted mandibular bone and compared the results clinically, radiographically, and histologically.

RESULTS

Normal tooth eruption was observed in the transplanted mandibles in the young dogs. In the mature dogs, eruption from the gingiva was delayed, whereas that from alveolar bone occurred normally in the transplanted mandibles. Further, the whole crown was covered with a cap of gingival tissue in the mature dogs, although this cap was not gingival overgrowth.

CONCLUSIONS

Tooth eruption is influenced by some unknown factors related to aging. Apparently, apoptosis did not occur in the connective tissues between the reduced enamel epithelia and oral epithelia that overlay the teeth in the mature subjects.

Expression of parathyroid hormone-related protein (PTHrP), osteoclast differentiation factor (ODF)/receptor activator of nuclear factor-kappaB ligand (RANKL) and osteoclastogenesis inhibitory factor (OCIF)/osteoprotegerin (OPG) in ameloblastomas

BACKGROUND

To clarify the roles of osteoclast regulatory factors in progression of odontogenic tumors, expression of parathyroid hormone-related protein (PTHrP), osteoclast differentiation factor (ODF)/receptor activator of nuclear factor-kappaB ligand (RANKL), and osteoclastogenesis inhibitory factor (OCIF)/osteoprotegerin (OPG) were analyzed in ameloblastomas as well as tooth germs.

METHODS

Tissue specimens of nine tooth germs and 36 benign and one malignant ameloblastomas were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry for the expression of PTHrP, ODF/RANKL, and OCIF/OPG.

RESULTS

Expression of PTHrP, ODF/RANKL, and OCIF/OPG mRNA was detected in all tooth germ and ameloblastoma samples. Immunohistochemical reactivity for PTHrP was recognized in both normal and neoplastic odontogenic epithelial cells. In ameloblastomas, PTHrP reactivity in peripheral columnar or cuboidal cells was stronger than that in central polyhedral cells, and keratinizing cells showed increased PTHrP reactivity. ODF/RANKL and OCIF/OPG were expressed predominantly in mesenchymal cells rather than in odontogenic epithelial cells in both tooth germs and ameloblastomas. Epithelial ODF/RANKL and OCIF/OPG expression was slightly lower in ameloblastomas than in tooth germs. Tumor cells in plexiform ameloblastomas showed slightly higher reactivity for PTHrP and ODF/RANKL than tumor cells in follicular ameloblastomas.

CONCLUSION

Expression of PTHrP, ODF/RANKL and OCIF/OPG in tooth germs and ameloblastomas suggests that these factors might locally regulate bone metabolism and dynamics in tooth development as well as in progression of ameloblastomas. These factors might also be involved in tumor cell differentiation and/or tumor tissue structuring in ameloblastomas.

Abnormal epidermal differentiation and impaired epithelial-mesenchymal tissue interactions in mice lacking the retinoblastoma relatives p107 and p130

The functions of p107 and p130, members of the retinoblastoma family, include the control of cell cycle progression and differentiation in several tissues. Our previous studies suggested a role for p107 and p130 in keratinocyte differentiation in vitro. We now extend these data using knockout animal models. We found impaired terminal differentiation in the interfollicular keratinocytes of p107/p130-double-null mice epidermis. In addition, we observed a decreased number of hair follicles and a clear developmental delay in hair, whiskers and tooth germs. Skin grafts of p107/p130-deficient epidermis onto NOD/scid mice showed altered differentiation and hyperproliferation of the interfollicular keratinocytes, thus demonstrating that the absence of p107 and p130 results in the deficient control of differentiation in keratinocytes in a cell-autonomous manner. Besides normal hair formation, follicular cysts, misoriented and dysplastic follicles, together with aberrant hair cycling, were also observed in the p107/p130 skin transplants. Finally, the hair abnormalities in p107/p130-null skin were associated with altered Bmp4-dependent signaling including decreased DeltaNp63 expression. These results indicate an essential role for p107 and p130 in the epithelial-mesenchimal interactions.

Occlusal guidance for eruption disturbance of mandibular second premolar: a report of three cases

This study presents the treatment courses in three impacted cases of mandibular second premolars caused by distal inclination of the tooth germs. In all cases, the second premolars were surgically exposed, but the traction periods until oral emergence differed. The reasons for the differences may be the variation in the severity of the distal inclinations of the tooth germs and the calcified development of the affected germs at fenestration.

Distribution of basement membrane type IV collagen alpha chains in ameloblastoma: an immunofluorescence study

BACKGROUND

Type IV collagen, a heterotrimeric molecule that exists in six genetically distinct forms, alpha1(IV)-alpha6(IV) is a major structural component of basement membrane (BM) and acts as a scaffold for other BM constituents.

METHODS

Indirect immunofluorescence using alpha chain-specific monoclonal antibodies was employed to clarify basement membrane (BM) collagen IV distribution in two ameloblastoma, and for comparison, on oral mucosa and tooth germ.

RESULTS

Ameloblastoma BM expressed five of six genetically distinct forms of collagen IV: alpha1(IV), alpha2(IV), alpha5(IV) and alpha6(IV) chains occurred as intense linear stainings without disruption around neoplastic epithelium, and this expression pattern was fundamentally similar to oral mucosa BM; alpha4(IV) expression was rare and occurred around nests of primitive tumor cells or potentially invasive sites. The tooth germ demonstrated a stage- and position-specific collagen IV distribution: the inner enamel epithelium BM expressed alpha1(IV), alpha2(IV), and alpha4(IV) except in the cuspal predentine region; and the outer enamel epithelium BM expressed alpha1(IV), alpha2(IV), alpha5(IV), and alpha6(IV) chains.

CONCLUSIONS

Results suggest that collagen IV alpha chain distribution in ameloblastoma BM plays an important role in tumor cytodifferentiation and progression.

The secretion of amelogenins is associated with the induction of enamel and dentinoid in an ameloblastic fibro-odontoma

Ameloblastic fibro-odontoma is the unique entity of epithelial-ectomesenchymal odontogenic tumors, which is characterized by enamel formation in addition to dentine. We examined immunohistochemically a case of this tumor in which enamel having prism structures was developed in the absence of odontoblast differentiation but was in contact with mesenchymal matrices. Histological examination showed diverse morphological features of epithelial tumor cells, e.g., cuboidal cells comprising tooth bud-like projections, ameloblast- and stellate reticulum-like cells, and residual cells in forms of extended cords or islands of odontogenic epithelium. Immunostaining with anti-amelogenin sera proved that the intracellular production of amelogenins was initiated at the tooth bud-like stage. The secreted amelogenins were detected almost exclusively in the induced enamel and dentinoid areas, as well as in the core region of cementicle-like spheres deposited in the encapsulating stroma. The results obtained indicate that the odontogenic tumor epithelia and its products, i.e., amelogenins, participate in multifaceted aspects of dental hard tissue formation that takes place during oncogenesis.

Intraoral distraction osteogenesis of the mandible in hemifacial microsomia

PURPOSE

Lengthening of the mandible by distraction osteogenesis is the preferred method for treatment of hemifacial microsomia in children. Use of an intraoral distraction technique and horizontal oblique ramus osteotomy in such patients is presented.

PATIENTS AND METHODS

Mandibular ramus lengthening was performed in 11 patients aged 6 to 12 years with hemifacial microsomia. During the age of mixed dentition in hemifacial microsomia patients with a hypoplastic mandible, the unerupted molars buds are located high in the retromolar region and are in danger of being damaged by the osteotomy. Therefore, an intraoral approach exposing the mandibular ramus and angle was performed, and a horizontal oblique ramus osteotomy was made, preserving the inferior alveolar nerve. An intraoral device was placed along the ramus, and distraction was started on the third postoperative day at the rate of 1 mm/d and continued for 2 to 3 weeks or as long as necessary. The device was maintained for retention an additional 6 weeks and was then removed.

RESULTS

Clinically, the face became more symmetric. The postdistraction posteroanterior cephalometric radiographs demonstrated elongation of the affected ramus and improvement in facial symmetry.

CONCLUSIONS

The advantages of this method are that it allows device placement along the ramus, permitting the ramus elongation necessary in treatment of hemifacial microsomia, that it prevents damage to the tooth buds which, during the age of mixed dentition, are in a higher position in the retromolar area, and that it prevents injury of the inferior alveolar nerve.

Craniofacial tissues including tooth buds in fetal hypohidrotic ectodermal dysplasia

OBJECTIVE

Hypohidrotic ectodermal dysplasia (HED) comprises defects in hair, teeth, and sweat glands. Disturbances in other ectodermal tissues have been associated with the condition. Our objective was to examine ectodermal craniofacial structures histologically in a fetus with HED and to compare the findings to similar structures in normal control fetuses.

MATERIALS AND METHODS

A male fetus diagnosed with HED was therapeutically aborted in the 15th week of gestation. One male and two female healthy fetuses were used as normal controls. All fetuses were examined with parental consent, and had comparable sizes. Their bone maturation stage in the hand was identical. Tissue blocks from the craniofacial region were excised from all fetuses and prepared for histological analysis (formalin fixed, stained with toluidine blue or Alcian blue). The tissues examined were: tooth buds, skin and skin appendages, oral mucosa including minor salivary glands, major salivary glands, lacrimal glands, and adenohypophysis.

RESULTS

Fewer tooth buds, minor salivary glands, and hair follicles were observed in the HED fetus as compared to controls. The structures of the epidermal components in the developing HED organs were loose and disorganised. The adhesion between the ectodermal and mesenchymal organ components in the HED fetus seemed to be disturbed.

The fate of developing teeth in mandibular lengthening by distraction: an experimental study

PURPOSE

The purpose of this study was to observe developing teeth in a lengthened mandible after distraction.

MATERIAL

Ten mongrel dogs with deciduous dentitions were used.

METHODS

A corticotomy was carefully made around a tooth bud and the external distractor (Orthofix M-100) was connected. After a 5-day latent period, distraction was started at a rate of 0.75 mm per day for 10 consecutive days. Then, the lower jaw was stabilized by an external fixation to allow ossification. While the operation was performed on the left side (Distraction group), the contralateral side was studied for comparison (Control). In addition, a corticotomy, artificial fracture and external fixation were carried out to confirm the influence of the operation (Fracture group). Then macroscopic, radiographic and histological evaluations were carried out.

RESULTS

In the Distraction group, the space between the wall of the dental follicle and the crown expanded as distraction began. The end of the calcified root became wider and irregular during the distraction period, and finally, the apex closed. In the Fracture group, the teeth erupted although slight alterations of the root shape were observed in association with the operation period.

CONCLUSION

The root became irregular, but the teeth erupted within the distraction area.

Eruption disturbances of mandibular permanent canines in Japanese children

OBJECTIVES

The purpose of this study was to clarify the cause and prognosis of eruption disturbance of mandibular permanent canines.

SAMPLE AND METHODS

Fifteen Japanese children who visited Niigata University Dental Hospital between 1979 and 1997 with unerupted and/or impacted mandibular permanent canines were examined.

RESULTS

All cases showed unilateral disturbances. The eruption disturbance of 6 mandibular canines was associated with a calcified obstacle such as an odontoma (5 cases) or a supernumerary tooth (1 case). After removal of the obstacle, 5 canines were aligned within the dentition. Out of 10 cases, where the permanent canine germ showed malpositioning or aberrant eruption path, 5 primary predecessors had undergone endodontic treatment. In these 10 cases, 6 canines erupted after treatment, two were extracted and the remaining two were left in their impacted position.

CONCLUSIONS

The present results suggest that it is relatively easy for the position of unerupted mandibular canines associated with calcified obstacles to be improved by removal of the obstacle, but that it is more difficult for teeth showing anomaly in the position of the canine germ to be aligned within the dentition.

Immediate repositioning of an accidentally extruded immature premolar after extracting root remnants of the primary molar

This article describes a case where during an extraction of a primary molar's root remnant, the successor permanent tooth was accidentally extruded. The extruded tooth was immediately repositioned to its right position in the socket and it erupted normally after a short time. After 2 years, a routine clinical examination revealed normal appearance of the premolar in the dental arch. A radiograph demonstrated an obliterated coronal part of the pulp, normal root length, a slightly open apex and no periapical inflammation.

[Complications of injuries to the deciduous teeth. Clinical and radiographic evaluation. Perspectives on management and prevention. Apropos of 4 cases]

The traumatisms of primary teeth have often sequels thereabouts grave on the germs of their successional permanent teeth. They have many causes but they are above all frequent during the child's walking trial. We have carried out a clinical and radiographic study of some cases. The study has ascertained the fact that the diversity of the sequels and their gravity depend on the age of the occurring of the traumatism, the intensity and the direction of the shock. The therapeutic and preventive management of these traumatisms and their possible sequels use a pluridisciplinary protocol based on the strict application of indicated treatments, the clinical and radiographic regular follow up and the adoption of a rigorous preventive attitude by the parents during the target period of walking trial.

A histological study of the effect of growth hormone on odontogenesis in the Lewis dwarf rat

The effect of growth hormone (GH) on the dentition has been described in children with pituitary dwarfism where teeth fail to form; those that do form tend to be reduced in size and the eruption potential is diminished. The aim here was to examine the effect of GH on odontogenesis via molar development in Lewis (control), dwarf (Dw) and Dw GH-treated (Dw+GH) rats aged 3, 6, 9, 12 and 15 days. Dw+GH animals received a twice-daily dose (65 microg/kg) of GH which commenced at 2 days of age. Animals were killed, mandibles removed, processed to embedding in paraffin, sectioned and stained for histological examination of molar morphology during development. Variations in enamel mineralization and root development were observed. In 6-day-old animals, enamel mineralization was delayed in Dw and Dw+GH animals. Root initiation was evident at 6 days of age in controls but was not observed until 9 days of age in Dw and Dw+GH animals. At 12 days of age, maturation of enamel in Dw and Dw+GH animals remained delayed. By 15 days of age no variation in tooth development was evident. These data indicate that enamel mineralization is affected by the level of circulating GH in the rat. A specific deficiency of GH did not appear to delay bone resorption prior to tooth emergence.

Epidermal growth factor receptor as a mediator of developmental toxicity of dioxin in mouse embryonic teeth

We have previously shown that dioxins at prevailing levels in mothers' milk may cause mineralization defects in the developing teeth of their children. Developmental dental defects have also been reported in rhesus macaques and rats experimentally exposed to dioxin. The most toxic dioxin congener, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), is a potent modulator of epithelial cell growth and differentiation. To clarify whether epidermal growth factor receptor (EGFR), implicated in the mediation of the developmental toxicity of TCDD, is involved in dental toxicity, we cultured embryonic molar teeth from EGFR-deficient mice with TCDD, epidermal growth factor (EGF), and both agents in combination. In teeth of the normal embryos, TCDD caused depolarization of odontoblasts and ameloblasts. Consequently, the dentin matrix failed to undergo mineralization, the enamel matrix was not deposited, and cuspal morphology was disrupted. In teeth of the null mutant embryos, only the cuspal contour was mildly modified. EGF alone retarded the molar tooth development of normal embryos, but not that of EGFR-deficient embryos. When coadministered with TCDD, EGF for the most part prevented the adverse effects of TCDD on teeth of the normal embryos. These results show that the interference of TCDD with mouse molar tooth development in vitro involves EGFR signaling. Thus, EGFR may also play a role in the developmental defects that dioxins cause in human teeth. Because EGFR is widely expressed in developing organs, EGFR signaling may even be of general relevance in the mediation of the developmental toxicity of TCDD.

Experimental odontogenic cysts induced by in vitro 4-nitroquinoline 1-oxide (4NQO) treatment of F344 rat incisor tooth germs

This study was designed to establish an experimental animal model for elucidating the early stages of odontogenic cysts and tumors. It involves the in vitro treatment of tooth germs with 4-nitroquinoline 1-oxide (4NQO) at the early bell stage and their subsequent transplantation into the kidney subcapsular space. While all tooth germ transplants of the control group not exposed to the carcinogen showed continued tooth development with no pathological lesions, 21 of 23 4NQO-treated tooth germs developed into similar appearing keratinized cysts with or without associated tooth structures. The remaining two transplants failed to develop cysts and formed only a tooth. The present experimental procedure was effective in inducing keratinized cystic lesions that exhibit some similarities to human odontogenic keratocysts or primordial cysts.

Loss of deciduous teeth and germs of permanent incisors in a 4-year-old child. An atypic prepubertal periodontitis? A clinical, microbiological, immunological and ultrastructural study

A 4-year-old child was referred, in April 1988, to Rennes Dental School (France) for deciduous tooth mobility with premature loss of 4 deciduous teeth and germs of 2 permanent incisors. Microbiological examinations by culture revealed the presence of the periodontal pathogen Actinobacillus actinomycetemcomitans. Immunofluorescence of plaque samples revealed the presence of Porphyromonas gingivalis that had not been isolated by culture. Neutrophil functions were within normal ranges. Transmission electron microscopy of gingiva showed a disorganised epithelium. The connective tissue was infiltrated by inflammatory cells. The basement membranes were normal, but the connective tissue-epithelium interface was mainly composed of short rete pegs. Scanning electron microscopy of extracted deciduous teeth revealed lack of cementum, lacunae in the cementum and lack of fibrillar insertion on the middle part of the root. Skin lesions, mainly situated on face, were observed. Treatment was by extraction of mobile deciduous teeth combined with 3-week courses of metronidazole. Clinical and microbiological follow-up was continued over a 7-year period. No periodontal lesions have been detected since eruption of the permanent teeth. The present subgingival and lingual microflora (December 1995) is composed of bacteria associated with periodontal health. However, the future appearance of a hitherto undetected systemic disease is still possible.

Detection of apoptosis-related factors and apoptotic cells in ameloblastomas: analysis by immunohistochemistry and an in situ DNA nick end-labelling method

To clarify the possible role of apoptosis in odontogenic epithelium, apoptosis-related factors and apoptotic cells were examined by immunohistochemistry and an in situ DNA nick end-labelling method. Expression of bcl-2 protein was detected in both normal and neoplastic odontogenic epithelium, whereas expression of p53 protein was detected only in neoplastic but not in normal odontogenic epithelium. The prevalence of cases positive for Lewis(y) antigen in ameloblastomas was significantly lower than in enamel organs. Correlation between these factors and apoptotic cells presented by an in situ DNA nick end-labelling method was not clear. The number of apoptotic cells in ameloblastomas was significantly greater than in normal odontogenic epithelium, and apoptotic reactions in the granular cell type ameloblastoma tended to be more frequently detected than in other types of ameloblastomas. These results suggested that apoptotic cell death might play an important role in oncogenesis and/or tissue differentiation in odontogenic epithelium.

Eosinophilic granuloma: report of case

This paper related a case of eosinophilic granuloma in an eleven-year-old male child, treated successfully with curettage. The lesion appeared as a single irregular nodule in the left mandibular alveolar crest. A radiolucency was observed in the radiograph apparently causing an expansion of the vestibular and lingual cortical plates and displacement of the germs of the canine and first premolar. The treatment was by curettage, retaining the germs of the teeth involved. Other parts of the body were examined by osteal scintillography. Clinical and radiographic observations were done in the first three months; one year; two years; and five years postoperative with excellent prognosis.

Long-term histopathologic findings in tooth germs autotransplantation. Analysis of a series

Tooth germ autotransplantation, a surgical technique based upon extraction of a germ followed by reimplantation in the same individual, is indicated in tooth agenesis or loss as an alternative to traditional methods of treatment. The success of autotransplantation relies on several factors, and clinical studies indicate that results are excellent if correct surgery is carried out. This work offers a morphological contribution to the understanding of post-transplantation changes of the pulp, periodontal ligament and root cementum.

The role of endotoxin and cytokines in the pathogenesis of odontogenic cysts

Odontogenic cysts arise from tooth-forming epithelial residues. The stimulus for the formation of radicular cysts is thought to be endotoxin released from the infected necrotic tooth pulp. However, in keratocysts and follicular cysts, such a stimulus is not present. In order to investigate what drives the cyst epithelium to proliferate, explant media and fluids from 16 radicular cysts, eight keratocysts and seven follicular cysts and explant media from four specimens of non-inflamed gingival tissue were examined for the presence of endotoxin and cytokines. Cyst fluids were also cultured for 72 h in anaerobic and aerobic conditions to detect micro-organisms. Endotoxin from three different bacteria, cytokines [interleukin-(IL) 1 alpha, IL-1 beta and IL-6] as well as prostaglandin E2 (PGE2) were tested in an epithelial cell-proliferation assay. As the cyst epithelium is supported by a connective tissue capsule, the effect of fibroblast culture media on epithelial cell proliferation was also investigated. The results showed significantly higher concentrations of endotoxin in radicular cyst fluid than in the keratocyst or the follicular cyst. None of the cyst fluids contained micro-organisms. Immunoassays demonstrated the presence of IL-1 alpha and -6 in all fluids and explants tested; IL-1 beta was only found in the inflammatory radicular cysts. However, reverse transcriptase-polymerase chain reaction showed that mRNAs for IL-1 alpha, -1 beta and -6 were present in all cyst types. Proliferation studies indicated that endotoxin and the cytokines had a mitogenic effect on epithelia at low concentrations; PGE2 had very little effect at low concentrations, and had an inhibitory effect at high concentrations. Cyst fibroblast culture media had a mitogenic effect on the epithelia that was enhanced by the presence of endotoxin.

[Ultrasound diagnosis of fetal tooth anlagen and their histologic correlates]

AIM

The present study was to examine the radiographic and histologic correlation of the respective ultrasonographic findings.

METHODS

Histologic examinations were performed in 12 fetuses who had died in utero between 16 and 34 weeks of gestation. The fetuses had been examined by intrauterine sonography for tooth germs and had been subjected to additional radiographic examinations post abortum or partum. During autopsy, the tooth germs were again examined sonographically and radiographically, and non-decalcified histological sections were obtained by means of the sawing and grinding technique.

RESULTS

The results obtained by histologically examining the 12 fetal jaws in the ultrasonic plane corresponded in all cases to those examined by sonography and radiology.

CONCLUSION

Sonographic proof of tooth germs might gain increasing importance in future because agenesia of tooth germs is one of the principal signs of a variety of hereditary syndromes, particularly those of ectodermal origin.

Effects of vincristine on the developing hamster tooth germ in vitro

Vincristine is one of the cytostatic drugs present in cocktails commonly used for the treatment of cancer in children. The aim of this study was to evaluate biochemically and histologically the toxic effects of this drug on the developing tooth in vitro using the organ culture model in order to be able to predict what damage the drug can induce in the developing teeth from children undergoing anti-neoplastic chemotherapy. The most profound effect of the drug (10(-8)M-10(-4)M vincristine) on the developing tooth germ was the induction of mitotic arrests at the cervical loop and in the inter-cuspal regions. The 10(-4)M-10(-6)M vincristine doses were cytotoxic to most cells in the developing tooth germ. The 10(-7)M vincristine dose apart from induction of mitotic arrests, did not appear to be cytotoxic to the mature differentiated secretory cells. However, this dose induced incomplete nuclear polarization of the differentiating ameloblasts and odontoblasts. At 10(-8)M vincristine, the only effect observed were mitotic arrests; the secretory cells did not appear to have been affected at all. On the other hand, mineralization (TCA-soluble 45Ca and 32P uptake) was dose-dependently decreased from 10(-7)M vincristine upwards. 10(-9)M vincristine, the lowest dose tested, did not induce any changes in the developing tooth germ. The organ culture data indicate that 10(-9)M vincristine is the highest (safe) dose which does not induce any toxic effects in the developing hamster tooth germ.(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue reactions towards titanium implants inserted in growing jaws. A histological study in the pig

In this investigation, the tissue reactions towards titanium implants inserted in growing jaws of pigs were studied by means of histology. At the age of 12 weeks, 5 test pigs each received 4 Brånemark System titanium implants (fixtures). The fixtures were inserted immediately after extraction of the mesial root of the second deciduous premolar (P2) and the deciduous canine (C) on one side of the mandible and the mesial root of the first deciduous premolar (P1) on the other side. The fourth implant was placed after extraction of the deciduous lateral incisor (L) on one side in the upper jaw. Furthermore, 1 pig in which no extractions or fixture installations were performed served as a control. All pigs were followed for 165 days with clinical, radiographic and biometric examinations, the results of which have been previously presented. In this study, 10-microns-thick ground sections were produced for histology after the jaws had been fixed by immersion in formalin and further processed and embedded in plastic resin. Six of the fixtures originally inserted were lost during the experimental period, and the remaining implants were found to be involved with mineralized bone to varying degrees. Regarding the fixture-to-teeth relationship, it was found that, in the premolar region of the lower jaw, the teeth were positioned superior to and buccally angulated in relation to the fixtures. In the upper jaw, the implants were positioned below the adjacent teeth but centrally in the alveolar process. Tooth germs adjacent to the fixture had a displaced eruption path, buccally or lingually to the fixture. If the bud developed in close contact with the fixture, a changed morphology of the germ could be observed.

The effect of prenatal caffeine exposure on the enamel surface of the first molars of newborn rats

Timed-pregnant rats were randomly divided into three groups at day 7 of gestation. A caffeine tablet was implanted subcutaneously in the experimental group and a placebo tablet in the control group. The third group was used as surrogate dams. At birth, eight randomly selected pups born either to the experimental or control dams were placed with surrogate dams that had produced pups on the same day; these were then used in either the experimental or the control group, and so the surrogate dams raised pups that came from either the experimental or control group. At day 22 after birth, the pups were killed, and their first and second maxillary and mandibular molars were removed. They were then placed in a specially designed chamber and exposed to an acid solution. The outflowing acid solution was collected every 20 min and up to 80 min. Then the calcium, phosphorus, and magnesium contents of each fraction were measured. The enamel surfaces of untreated and acid-treated first molars of the caffeine and control groups were examined by scanning electron microscopy. Untreated teeth were powdered and separated into enamel and dentine. Pure enamel samples were examined with a Gandolfi X-ray powder camera to measure the crystallite size. At 20-, 40- and 60-min intervals, calcium and phosphorus contents of the first molars of the caffeine group were significantly higher than those of the control. The enamel surface of the untreated and acid-treated first molars of the caffeine group had significantly different scanning microscopic appearances from those of the non-caffeine untreated and acid-treated control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Retardation of mouse odontoblast differentiation by heparin in vitro

The effect of heparin was studied histologically and immunohistochemically. Tooth germs from 15-day-old mouse embryos were cultured with or without heparin. After 6 days of culture in control medium, mesenchymal cells underlying the inner enamel epithelium had differentiated into odontoblasts and secreted predentine. In medium with heparin, mesenchymal cells were undifferentiated. In medium with other glycosaminoglycans such as chondroitin sulphate, dermatan sulphate or hyaluronate, tooth germs were similar to those in control medium, as were those in medium with heparin-Sepharose absorbed serum. After 12 days of culture in the heparin medium, mesenchymal cells in some cusps had differentiated into odontoblasts and secreted predentine but in other cusps remained undifferentiated. Immunohistochemically, exogenous heparin did not prevent the deposition of type IV collagen, laminin and fibronectin in the basement membrane and extracellular matrix. These results suggest that exogenous heparin retards differentiation of odontoblasts but not by disruption of the basement membrane nor inactivation of heparin-binding growth factors present in serum.

Immunohistochemical demonstration of enamel proteins in odontogenic tumors

Immunohistochemical localization of two enamel proteins, amelogenin and enamelin, in comparison with that of keratin, was determined in odontogenic tumors and the allied lesions in order to verify functional differentiation of the tumor cells as ameloblasts. Amelogenin and enamelin were demonstrated in small mineralized foci and in the tumor cells surrounding them in adenomatoid odontogenic tumor (AOT), calcifying epithelial odontogenic tumor (CEOT), and calcifying odontogenic cyst (COC). Hyaline droplets in AOT showed positive staining for both enamel proteins. These mineralized and hyaline materials were not positive for keratin, although tumor cells were positive. On the other hand, no immunoreaction for enamel proteins was obtained in ameloblastoima and odontogenic epithelial cell nests within myxoma and epulis. The results suggest that tumor cells of AOT and CEOT and lining epithelial cells of COC show ameloblastic differentiation in part, but that ameloblastoma cells do not attain functional matauration as secretory phase ameloblasts.

Effects of gamma radiation on incisor development of the prenatal albino mouse

Fetuses of pregnant albino mouse exposed to 400 rad of gamma-irradiation, on the 12th gestational day, were compared with unirradiated fetuses to asses the radiation effect on developing incisors. Pregnant animals were sacrificed on day 18 post coitum, and their fetuses were decapitated. Heads were routinely prepared, frontally sectioned, and stained with hematoxylin and eosin. Histologic examination demonstrated that the development of the maxillary and mandibular incisors was retarded in all the experimental fetuses and were in early bell stage, whereas those of the control animals were elaborated their matrices. It was concluded that gamma-irradiation interferes with cytodifferentiation of the enamel organ and dental papilla and subsequently inhibits normal odontogenesis.