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.

Polarizing activity, Sonic hedgehog, and tooth development in embryonic and postnatal mouse

Tooth development involves reciprocal epithelial-mesenchymal interactions, polarized growth, mesenchyme condensation, and complex morphogenetic events. Because these processes bear similarities to those occurring in the developing limb, we asked whether morphogenetic signals found in the limb also occur in the developing tooth. We grafted mouse embryo tooth germs to the anterior margin of host chick embryo wing buds and determined whether the dental tissues had polarizing activity. Indeed, the grafts induced supernumerary digits. Activity of both molar and incisor tooth germs increased from bud to cap stages and was maximal at late bell stage in newborn. With further development the polarizing activity began to decrease, became undetectable in adult molar mesenchyme but persisted in incisor mesenchyme, correlating with the fact that incisors grow throughout postnatal life while molars do not. When different portions of neonatal incisors were assayed, a clear proximo-distal gradient of activity was apparent, with maximal activity restricted to the most proximal portion where undifferentiated mesenchyme and enamel organ reside. In situ hybridizations demonstrated that prior to induction of supernumerary digits, the tooth germ grafts induced expression in host tissue of Hoxd-12 and Hoxd-13. In addition, whole-mount in situ hybridizations and immunohistochemistry showed that developing tooth germs express Sonic hedgehog (Shh). Shh expression was first detected in bud stage tooth germs; at later stages Shh transcripts were prominent in enamel knot and differentiating ameloblasts at the cuspal region. We concluded that tooth germs possess polarizing activity and produce polarizing factors such as Shh. As in the limb, these factor(s) and activity probably play key roles in establishing polarity and regulating morphogenesis during early tooth development. Given its subsequent association with differentiating ameloblasts, Shh probably participates also in cytogenetic events during odontogenesis.

Development and cell fate in interspecific (Mus musculus/Mus caroli) intraocular transplants of mouse molar tooth-germ tissues detected by in situ hybridization

Mandibular first molar tooth germs were dissected from Mus musculus (CDI) and Mus caroli (age range: 14-day embryo to 1-day postnatal). Most of the tooth germs were separated enzymically into epithelial and mesenchymal components. Interspecific tissue recombinations and intact M. caroli tooth germs were grown in the anterior chamber of the eye of adult CDI mice for 24 weeks. Recombinations of M. caroli enamel-organ epithelium with M. musculus, dental papilla and follicle mesenchyme developed into normal teeth with advanced root, periodontal ligament and bone formation, thereby confirming extensive epithelial-mesenchymal interactions across the species barrier. Labelling sections by in situ hybridization with a M. musculus-specific DNA probe (pMSat5) showed that almost all cells in the pulp, periodontal ligament and bone were M. musculus, including cementoblasts. Reduced enamel epithelium and epithelial cell rests derived from donor M. caroli enamel organ were unlabelled. This indicates that any cementogenic role of Hertwig's epithelial root sheath must be short-lived. The immunological privilege of the intraocular transplantation site in M. musculus CDI mice did not extend to grafts including xenogeneic M. caroli dental mesenchyme. Thus, intact M. caroli tooth germs and recombinations of M. musculus enamel organ with M. caroli dental papilla and follicle showed limited development, with no root formation, and were populated almost exclusively with labelled host M. musculus lymphocytes.

[Outcome of wisdom tooth germ transplantation]

In 68 patients, 79 tooth germs of the third molar were transplanted. Out of this group, 43 patients with 50 transplantations under-went a follow-up examination. All surgery was performed by one surgeon. Retrospectively, we tried to establish whether the success of postoperative healing depends on the donor and receiver regions. Crossing the jaw border clearly worsens the prognosis for transplantation. Altogether 9 transplantations turned out to be failures, 7 of which had been transplanted from the upper to the lower jaw. The results of this investigation showed incomplete root development in 34%, the necessity of endodontic treatment in 6% and enlarged periodontal pockets in 8%. Ankylosed teeth were found in 10%; we did not see any root resorptions.

Autotransplantation of teeth in cases with agenesis or traumatic loss of maxillary incisors

The purpose of this study was to investigate the prognosis of 50 consecutively autotransplanted teeth to the maxillary incisor region. Thirty-five were transplanted in cases of traumatic injuries, eleven in cases of agenesis and four in cases with impaction of maxillary canines. The average follow-up time was 7 years and 6 months (range 4-17 years). The transplants were examined clinically in respect of tooth vitality and radiographically in respect of root canal obliteration, periradicular changes, root formation, and root length. The results show a success rate of 82 per cent. It is concluded that the procedure of tooth transplantation has the advantage of maintaining or restoring alveolar bone volume and gives the opportunity to replace a missing tooth without involvement of neighbouring teeth as prosthetic abutments.

[The possibility of orthodontic therapy in transplanted teeth]

The paper reports four cases of tooth transplant: two teeth were transplanted once they were fully mature (completely formed roots) and two were transplanted as germs. Having documented the clinical and radiological recovery for all four teeth, orthodontic braces were applied for a variety of reasons. In the two cases of teeth transplanted once the roots had completely formed it was impossible to move the teeth, whereas in the case of the germ transplants the teeth were quickly moved to a correct occlusal position. On the basis of these different reactions, the author assesses the possibility of histological recovery of the tooth transplant. Repeated radiographic controls showed anomalies in radicular formation and of the camera pulposa. Lastly, the paper discusses the optimal time to transplant a tooth germ.

[Tooth germ transplantation or gap closure--a comparative study in the loss of the first molar]

In our study 37 transplanted and 33 mesialized molars by orthodontics were clinically and radiologically compared. The teeth moved by orthodontics showed a better long-term prognosis. As vital teeth with functioning periodontal structures and only slightly shortened roots they were equivalent to healthy teeth. However, the disadvantage of orthodontic space closure is the requirement of a good compliance due to long treatment time. The prognosis of maintaining a transplanted tooth germ is uncertain. One third of the teeth showed an altered periodontium with resorption areas. The danger of a continuing resorption, as well as a late external resorption is still a risk after a long period of time and can eventually lead to tooth loss. As a treatment alternative, germ transplantation may serve as a replacement of a single missing 6-year-molar in adolescence. Orthodontic space closure is indicated at any age with an existing dysgnathia, the loss of several first molars, the loss of space and mesial tipping of the second molars.

Repair potential in localized juvenile periodontitis. A case in point

An aggressive form of localized juvenile periodontitis (LJP) in a 12-year old West African female is reported. The case was treated with scaling, root planing, debridement, and tetracycline therapy, which resulted in complete resolution of the disease, including elimination of periodontal inflammation, regeneration of lost periodontal structures, and spontaneous repositioning of teeth that had pathologically migrated. A hopelessly involved mandibular right first molar was successfully replaced by an incompletely developed maxillary third molar tooth bud whose roots and pulp structure continued to develop after autotransplantation. It is suggested, that LJP can be successfully treated without periodontal surgery and that the potential for repair in LJP cases is apparently greater than what one can anticipate in adult forms of periodontitis.

Calcification capacity of dental papilla mesenchymal cells transplanted in the isogenic mouse spleen

The capacity of the dental pulp to form calcified tissue was examined in papilla cells dissociated from first molar tooth germs of the neonatal mouse and isografted in the spleen for up to 7 days. To obtain papilla cell populations without odontoblasts, pulpal mesenchyme was isolated mechanically from the enamel organ after 0.1% trypsin treatment and rolled on a membrane filter. On day 3 after transplantation, the grafted papilla cells had changed into large, spindle-shaped cells, and initial calcification with needle-like crystals began in association with the collagenous matrix surrounding those cells. On day 7 after transplantation, the spindle cells transformed into odontoblast-like cells containing well-developed secretory organelles, and irregular, but nontubular, calcified tissues were commonly observed surrounding the extracellular collagenous matrix. The calcified tissue matrix with cellular inclusions displayed a structure similar to that of osteodentin. During this period, an intense positive reaction for alkaline phosphatase (ALPase) activity was demonstrated along the cell membranes of the odontoblast-like cells aligned at the periphery of forming calcified tissue. Enzymatic activity could not be detected on the cells incorporated completely into osteodentin-like matrix. The present results show that the papilla cell population transplanted into the spleen formed osteodentin-like material, thus demonstrating the capacity of papilla cells to produce calcified tissue.

Creation of a chimaeric periodontium in the rat by isotopic tooth germ transplantation

The purpose of this work was to develop and test a chimaeric periodontium in which it would be possible to distinguish between connective tissue cells of odontogenic and oral mucosal origin. The recombinant periodontium was created by transplanting first maxillary molar tooth germs with their follicles from 1-3-day-old hooded Lister rats into the corresponding evacuated crypts of 6-9-day-old histocompatible recipients of the same strain. Of 71 transplants, 22 had formed erupted teeth 3 weeks later, with dentogingival junctions and periodontal ligaments histologically similar to those of control teeth. The recombinant nature of the graft periodontium was confirmed by incubating tooth germs in vitro with tritiated thymidine before grafting them, and then demonstrating radiolabelled nuclei in the dentogingival junctions formed by the transplants. Labelled cells were randomly distributed within the periodontal ligament and predominantly near to the basement membrane of junctional epithelium.

[Autotransplantation of tooth germs]

During the routine orthodontic examination of a 8-year-4-month old female, it was found that the upper right canine and premolars were missing. The anamnesis revealed that their buds had been surgically removed after a trauma when she was 6 years old. The lower incisors were slightly crowded. Since the age of the patient would not permit a fixed prosthetic restoration in the next few years, it was decided to attempt an autogeneic transplant of the lower first premolars to replace the upper right canine and premolars too.

[Periodontal development after tooth germ transplantation within the framework of orthodontic treatment]

The normal development of the periodontal structures was confirmed histologically on young beagle dogs following tooth germ transplants. In humans, clinical and radiographic examinations revealed no pathology of the periodontium following transplantation of tooth germs. The grafted teeth could be moved orthodontically in the same way as any other teeth. No precautions need to be taken. This paper describes the most common indications for transplanting the tooth germs of canines, bicuspids and molars.

Retrovirus-induced insertional mutation in Mov13 mice affects collagen I expression in a tissue-specific manner

In the Mov13 mouse mutant, transcription of the alpha 1 (1) collagen gene is blocked by a retroviral insert in the first intron. We now report that teeth derived from homozygous embryos produce a dentin layer containing normal amounts of collagen 1. In situ hybridization and RNAase protection experiments indicate that the mutant allele is efficiently transcribed in odontoblasts, in contrast to other cell types. Correct splicing of the primary transcript containing the viral sequence results in a functional alpha 1 (1) collagen mRNA. The absence of a mutagenic effect in odontoblasts, as opposed to fibroblasts, suggests that the retroviral insert interferes with tissue-specific transcriptional control of the alpha 1 (1) collagen gene, most likely by inactivating cell-type-specific cis-acting regulatory elements.

[Combined surgical orthodontic therapy in a patient with multiple agenesis]

After a wide analysis of the problems concerning biology and integration of autogenic transplantation of tooth germs, the Authors present a clinical case of monolateral agenesis of two premolars, with the transfer of the second premolar germ from one side to an other, suggesting some technical details in flap scalloping.

[Autotransplantation: technic and long-term results]

Dental transplantation can be a useful and efficious technic. It was first described by Ambroise Pare and the authors have had over 12 years success and failures enough to present clinical cases and illustrations of the surgery and the orthodontic treatment. Success depends essentially on the right indication, the time and the exact methodical technic, reproducible in a treatment plan.

Morphological evidence of the formation of intracellular collagen fibrils in the embryonic mouse molar odontoblasts induced by colchicine administration

The effects of colchicine on collagen formation were examined ultrastructurally using secretory odontoblasts in mouse molar tooth germs isografted to the spleen for 1 week. Colchicine in concentrations of 0.025 or 0.05 mg/0.1 ml was injected intravenously 12-24 h prior to harvesting. Colchicine induced the disruption of the Golgi apparatus and caused the accumulation of various types of Golgi-associated vacuoles containing collagenous fibrillar structures. Many vacuoles containing fine particles, nonstriated parallel filaments, banding patterns with a periodicity of approximately 63-nm intervals, and occasionally segment-long-spacing-like assemblies were aggregated in the cytoplasm during the experimental period. These morphological changes in vacuole contents may reflect the initial steps for polymerization of the intracellular collagen fibrils. The majority of the aggregated vacuoles were degraded by fusion with lysosomes but banded filamentous material in some vacuoles appeared to polymerize into the collagen fibrils with native structures. These results suggested that in unsecreted vacuoles accumulated in the odontoblasts as a result of colchicine administration the polymerization of collagen fibrils with native structures can occur.

Ultrastructure of a new generation of odontoblasts in grafted coronal tissues of mouse molar tooth germs

Third molar tooth germs were removed from 14-day-old mice and freed from the enamel organ and follicle. After section of the apical tissues, including Hertwig's sheath, they were transplanted in 1-day-old newborn mice of the same lineage. Electron microscopy of grafts removed 7, 14 and 21 days later showed that, following the disappearance of the initial layer of odontoblasts and a period of adaptation, 14 days after transplantation newly differentiated odontoblasts deposited tubular dentine. The dentine matrix production was increased over that of controls, demonstrating that synthesis was accelerated, possibly because of lack of nerves in the grafts. Numerous characteristic structures that might be involved in the transit of proteoglycans from the Golgi apparatus were seen, as far as the extremity of the odontoblast processes. The particular experimental conditions allowed the observation in the neck region of the odontoblast of a concentration of coated vesicles which might be involved in cellular lengthening. Thus, in the presence of a fine and regular vascular network, a new generation of odontoblasts may differentiate, even in the absence of epithelial and nervous elements, and so predentine may contain inductive factors that allow the odontoblastic differentiation of pulp cells in contact with it.

Autogenic tooth transplantation: a report of ten cases

Modifications in the surgical procedure for transplantation of the unerupted mandibular third molar to the first molar socket are presented, and the clinical and radiographic data on ten cases with a 3-year follow-up are described. The proposed method of treatment makes it possible to stabilize the transplant without a splint by using a suture crossed over the occlusal surface of the tooth.