[Autotransplantation of tooth germs]

The authors explained, after an attentive review of literature, the clinic and therapeutic procedures about dental germs' transplant. They show the indications for this surgical operation, the procedure for selection of grafting germs and the current surgical technique to do it.

[Autotransplantation of human tooth germs]

The Author presents three cases of tooth germ transplantation which were periodically checked by x-rays to show the progressive root development. The clinical result obtained were quite satisfactory. The situations requiring the transplantations in the 3 cases were all rather unusual: in one case the tooth germ was inside a large follicular cyst; in the other two the tooth germs were mesiodistally rotated 90 degrees which made eruption impossible. The cases described differ from cases frequently found in literature in that the transplanted tooth germs were in the initial stage of development; the roots, in fact, had not yet begun to develop. All the tooth germs transplanted, once their growth was completed, presented two types of morphological alternations. A reduction in the volume of the pulpar chamber and a pad of radiopaque tissue around the neck of the tooth. We have attempted to give an explanation for both of these alterations. The cases as well as the surgical procedures are described in detail.

Nerve growth to tooth buds after homotopic or heterotopic autotransplantation

Feline permanent incisor tooth buds (bell stage) were autotransplanted to mandibular alveolar sockets (homotopic site) or to the submandibular subcutis or the leg (heterotopic sites). This was done in 34 kittens aged 1-2 months. After survival times of 3-8 months the animals were fixed by glutaraldehyde perfusion. A total of 56 mineralized teeth, which had developed at the recipient sites, were removed, demineralized and processed for light microscopic (LM) general evaluation. Fourty-four teeth, which were judged to be grossly normal in the LM, were selected for electron microscopic (EM) analysis with respect to the occurrence of pulpal nerve fibres. The highest proportion of normal teeth (16 of 16) was obtained from the alveolar site, followed by the submandibular (11 of 14) and hindlimb (17 of 26) sites. Most of the grossly normal grafts possessed pulpal axons (37 of 44). The alveolar grafts were all innervated and exhibited a largely normal appearance qualitatively and in terms of percentage of myelinated fibres. The proportion of innervated pulps was lower among the heterotopic mandibular (10 of 11) and hindlimb (11 of 17) grafts. In addition, signs of nerve fibre degeneration appeared more frequently at the heterotopic sites. On the basis of these findings, and in view of the results of other workers, we conclude that tooth germs are attractive targets for all divisions of the trigeminal nerve and for cutaneous nerves outside the trigeminal system. However, the morphological picture tends to become increasingly abnormal with increasing distance from the normal locus.

The development of mandibular molar tooth germs isografted in the mouse spleen

Tooth germs taken from 13-day-old embryonic mice and isografted in the spleen of adult mice were examined by light and electron microscopy. Well-organized tooth structures from the early cap stage to fully developed and mineralized mature teeth were obtained up to day 60 after transplantation. Germs on day 2 were similar to those prior to the onset of grafting but reached the late cap stage of development on day 4. On day 6, enamel and dentine formation were initiated and inner enamel epithelium and dental papilla cells were polarized. On days 10-15, enamel-matrix secretion was completed and almost all ameloblasts had become resorptive enamel epithelium. India ink injected from the recipient caudal vein accumulated to the capillaries within the pulp throughout the newly-formed vessels. On day 20, defined root formation had begun but occasionally irregular and cellular osteodentine was formed in root areas. On day 30, transplants were covered with reduced enamel epithelium and acellular cementum was formed at the root areas together with rudimentary periodontal ligament fibres. Cellular cementum became thicker up to day 40. There was little evidence of cellular infiltration from recipient tissue up to day 60. The spleen seems to be a suitable site for transplantation of tooth germs.

[Vital tooth autotransplantation]

Ten cases of dental transplants belonging to the authors' set of cases were selected and they proved to be successful according to the factors these authors' believe to be important. The operations were carried out on young patients by transplanting the not fully formed third molar to the place of the first molar, following the technique described in the text. The success of a vital dental autotransplant depends on some factors: the tooth to be transplanted should have completed the amelogenesis so that two thirds of its root and the floor of the pulp chamber are also formed; the receiving alveolus must be prepared before the giving area, thus reducing the time in which the third molar remains dislocated out of its alveolus and the lack of communication between the two surgical beds.

Autotransplantation of human premolars. A clinical and radiographic study of 100 teeth

The purpose of the present study was to identify factors which might influence the success of autotransplantation, such as root development, root resorption, pulp condition and tooth eruption. The material consisted of 100 human premolars transplanted in 87 patients. The observation period ranged from 3-18 years, with a mean value 6.3 years. Clinical and radiographic examinations were performed. The transplanted premolars were divided into 7 stages of root development. At the final control, 93 teeth remained and 7 teeth were extracted. Periodontal healing without root resorption was related to stage of root development. It decreased from 93% in teeth with 3/4 root development to 37% in teeth with fully developed roots. Inflammatory root resorption was seen in 7 cases and replacement root resorption in 12 cases. Pulp revascularization was observed in 100% in stages with initial root development to 1/2 root development and decreased to 0% for teeth with fully developed roots. Pulp obliteration was observed in all cases with revascularized pulp tissue. The gingival condition was similar to contralateral, not transplanted premolars or adjacent teeth. Root growth increased with the stage of root development at the time of transplantation. It is concluded that transplantation of premolars with 1/2-3/4 root development provides a good chance of pulp survival, limited risk of root resorption and ensures sufficient final root length, and is thus recommended.

Recombinant study of the mouse molar cervical loop and dental papilla by renal transplantation

Cervical loop tissues of the mandibular first molar germs were dissected from 18-day mouse embryos and recombined with the isochronal dental papilla mesenchyme. The recombinants were transplanted under the kidney capsule of syngeneic male mice. Five days later, proliferation of epithelial and mesenchymal cells was observed. At the junctional region between the internal dental epithelium and the dental papilla mesenchyme, extracellular organic matrix was deposited. By 10 days after, transplantation, the formation of dentine and enamel was initiated. Twenty days after transplantation, the recombinant developed into an almost intact molar tooth. The compensatory potential of the molar cervical loop, when recombined with the dental papilla mesenchyme, was indicated.

Histology, innervation and radiographic appearance of fetal rat tooth germs developing in oculo

Rat molar and incisor tooth germs from gestational days 18-21 were homologously grafted to the anterior eye chamber of adult recipients. The fetal tooth transplants survived and grew considerably in the eye, attached to and vascularized from the anterior surface of the host iris. Grafts were examined histologically and compared with in situ controls after up to 6 months in oculo. Radiographic examinations of the grafts showed a normal rate of mineralization and a distinct enamel/dentin border after intraocular development. The size of the tooth grafts was somewhat smaller than in situ but the grafted teeth attained a form much resembling in situ incisors and molars. Light microscopy revealed a regular dentin and predentin, a distinct dentin/enamel border and a well innervated and vascularized pulp. No degenerative changes in dentin or enamel layers could be found in long-term grafts (6 months). Thus, intraocular tooth grafts in rats develop many histologic and anatomic features typical of normal teeth, emphasizing the importance of intrinsic regulatory mechanisms in tooth development.

Autotransplantation and replantation of tooth germs in monkeys. Effect of damage to the dental follicle and position of transplant in the alveolus

The effect of damage to the follicle and of superficial positioning of tooth germs after replantation or autotransplantation was studied in green Vervet monkeys. Radiographs were taken immediately after surgery and 3, 6 and 9 months postoperatively, whereafter the animals were sacrificed. The tissue blocks were sectioned in step serial sections along a frontal plane and histologic and radiographic evaluation was made. Tooth germs whose follicle was either damaged or removed showed no sign of eruption, while tooth germs which were replanted with an intact follicle were fully erupted within 3 months. Non-operated control teeth were fully erupted within 6 months. Histologic examination revealed that roots of replanted teeth were only slightly shorter than the non-operated control teeth. Transplantation of tooth germs in different positions in relation to the alveolar crest showed that teeth placed in their original position attained an average tooth length of 12.5 mm, whereas teeth placed in a semi-erupted position achieved an average length of only 9.7 mm. A control group of non-operated incisors demonstrated an average tooth length of 13.7 mm. This study indicates that damage to the follicle at the time of replantation of tooth germs is of major importance for tooth eruption and that placing tooth germs in a semi-erupted position adversely influences later root development.

Influence of serum on cultured murine tooth organ allotransplants

Previous investigations indicated that in vitro culture of fetal tooth germs before allotransplantation prolonged graft survival. This study assessed the influence of different sources of serum in culture medium on post-transplant development of neonatal tooth organs. The results indicate that recipient-strain serum, but not donor-strain serum or calf serum, increased tooth survival compared with that of uncultured controls, which were rejected by the fourteenth post-transplant day. The survival curve for cultured tooth organs was shifted to the right by two days. No tooth transplant survived beyond three wk.

Murine tooth organ transplantation after in vitro culture

Molar tooth organs were transplanted from fetal and neonatal mouse donors as well as from cap-stage molar tooth organs following ten days of in vitro culture. Tooth organs from neonatal donors appeared to develop better than those from fetal donors in syngeneic recipients. Cultured allogeneic molar tooth organs appeared to survive longer than uncultured controls.

Aberrations involving the enamel epithelium in transplanted developing teeth

Structural changes that occurred when unerupted developing permanent teeth in dogs were transferred to other bony crypts or surgically prepared sockets were assessed histologically. The enamel epithelium and pieces of enamel matrix were often displaced from the developing teeth and contained within the dental sac. The epithelium underwent metaplasia, cysts frequently developed, and cementum was formed in moderate quantities when enamel matrix was directly in contact with connective tissues. Development of the crowns did not continue normally, and the teeth did not erupt.