The critical apical diameter to obtain regeneration of the pulp tissue after tooth transplantation, replantation, or regenerative endodontic treatment.

INTRODUCTION: Regeneration of pulp-like tissue in the pulp chamber after tooth transplantation, replantation, or in regenerative endodontic treatment is only possible if the apical foramen is open. According to the literature, the success of regeneration decreases considerably if the foramen is smaller than 1 mm when measured on radiographs. The aim of this study was to study histologically the relation between the width of the apical foramen and regeneration of tissue in the pulp chamber after autotransplantation. METHODS: Fifteen single-rooted mature teeth of 3 adult beagle dogs were used. All experimental teeth were extracted and underwent apicoectomy. The teeth were photographed from the apical side, and the width of the foramen was calculated. The foramen width ranged from 0.24-1.09 mm. All teeth were replanted in infraocclusion. The observation period was 90 days after transplantation. RESULTS: The 10 teeth with the smallest apical diameter, ranging between 0.24 and 0.53 mm, showed vital tissue in at least one third of the pulp chamber. The 6 most successful teeth showing vital tissue in the entire pulp chamber had an apical diameter between 0.32 and 0.65 mm, and 80% of the experimental teeth with a diameter varying between 1.09 and 0.31 mm showed vital tissue in at least one third of the pulp chamber 90 days after transplantation. CONCLUSIONS: The size of the apical foramen seems not to be the all decisive factor for successful revascularization and ingrowth of new tissue after transplantation. The minimum width of the apical foramen has not been determined, but a size smaller than 1 mm does not prevent revascularization and ingrowth of vital tissue. In this animal study an apical foramen of 0.32 mm did not prevent ingrowth of new tissue in two-thirds of the pulp chamber 90 days after transplantation.

Does removal of the original pulp tissue before autotransplantation influence ingrowth of new tissue in the pulp chamber?

In an attempt to extend the indication area for autotransplantation of vital teeth, two possibilities can be proposed: (i) The enlargement of the apical foramen, with the aim to facilitate revascularization and ingrowth of new tissue. The ingrowth of tissue will eliminate the need for endodontic treatment when mature teeth are transplanted and (ii) the cryopreservation of teeth in case they cannot be transplanted immediately to the receptor site. Teeth with an ideal stage of root formation can be cryopreserved to perform transplantation later. Although pulpcell cultures survive crypreservation in vitro, the pulp tissue cannot survive the cryopreservation procedures when it is kept inside the pulpchamber. Therefore, the pulp tissue has to be removed before cryopreservation. It has been demonstrated that revascularization and ingrowth of new tissue can occur in an empty pulp chamber (1). The aim of this study was to find out if revascularization and ingrowth of new pulp tissue is influenced by removal of the original pulp tissue before autotransplantation. Twenty nine single-rooted teeth from three adult beagle dogs were transplanted after resection of the root tip. One group of teeth (n = 14) had the pulp tissue removed before transplantation. The other group (n = 15) had the original pulp left in situ. The transplanted teeth were histologically analysed 90 days post-transplantation. In the group with the tissue left in situ, 12 teeth (80%) showed a pulp chamber totally filled or at least 1/3 to 2/3 filled with viable tissue. In the group with the pulp tissue removed, 11 teeth (79%) had no or little vital tissue in the pulp chamber. The necrotic masses that develop in the original pulp tissue immediately after transplantation are a possible stimulating factor in the repair process of the pulp. As a conclusion, it can be stated that in case of autotransplantation of teeth, it is advisable to leave the pulp tissue in situ to stimulate the revascularization and ingrowth of new tissue after transplantation.

Influence of cryopreservation on the pulpal tissue of immature third molars in vitro.

The purpose of this study was to evaluate in vitro the viability of isolated and non-isolated pulpal tissue of immature third molars after cryopreservation. This study was divided in three different experiments. Experiment 1: Pulpal tissue isolated from 19 third molars was divided in horizontal segments. Each segment was cultured separately in order to evaluate whether differences in growth capacity within the tissue could be found. Experiment 2: Pulpal tissue isolated from 27 third molars was divided in a mesial and a distal part. One part was cryopreserved before culturing, the other part was cultured immediately. Growth capacity of cryopreserved and non-cryopreserved tissue was evaluated and compared. Experiment 3: 43 third molars were cryopreserved. After thawing, the dimension of the apical foramen was measured and the pulp was isolated and segmented horizontally. The different parts were cultured and growth capacity was evaluated and compared. Results of experiment 1 and 2 showed no significant difference in growth capacity between fibroblasts originating from different pulpal segments of the same tooth without cryopreservation and between fibroblasts originating from cryopreserved and non-cryopreserved isolated pulpal tissue. In experiment 3 it was demonstrated that the dimension of the apical foramen and pulpal viability after cryopreservation are positively correlated. A minimum dimension of 9.42 mm(2) enables the cryoprotective agent to penetrate sufficiently and to protect the pulpal tissue from apex to crown. This study proved that cryopreservation of human pulpal tissue is possible if the cryoprotective agent can reach the entire pulp.

Influence of cryopreservation on human periodontal ligament cells in vitro.

Cryopreservation of teeth before autotransplantation may create new possibilities in dentistry. The purpose of this study was to examine the effect of a standardised cryopreservation procedure on human periodontal ligament (PDL) cell cultures. Human PDL fibroblasts obtained from immature third molars of 11 patients were cultured and divided into two groups. The experimental group was cryopreserved and cultured after thawing. The control group was cultured without cryopreservation. A comparison was made between cryopreserved and control cells. To evaluate possible differences in the characteristics of the fibroblasts, the cells in both groups were tested for viability (membrane integrity), growth capacity and alkaline phosphatase (ALP) expression. The Wilcoxon test for paired comparison between cryopreserved and non-cryopreserved cells was performed for each characteristic. The results showed that membrane integrity of cells was not influenced by cryopreservation. There was no statistically significant difference in growth capacity between cryopreserved and control cells. Non-cryopreserved cells were slightly stronger positive for ALP, but the difference was not statistically significant. From these experiments it can be concluded that the observed parameters are not influenced by cryopreservation.

Tooth transplantation and cryopreservation: state of the art.

Autotransplantation of teeth is useful and has many indications in dentistry. Cryopreservation of teeth creates new possibilities--eg, when autotransplantation is needed, but the recipient site is too small and orthodontic treatment is needed to gain space for the transplant. This review article examines the reactions of various dental tissues after autotransplantation vs after autotransplantation with cryopreservation. Various subjects will be discussed, including periodontal healing, pulp reactions, and root development after autotransplantation with and without cryopreservation.

Histologic analysis of pulpal revascularization of autotransplanted immature teeth after removal of the original pulp tissue.

The survival rate of replanted and autotransplanted teeth is mainly affected by the reaction of the pulp. Pulpal necrosis can cause periapical inflammation and inflammatory root resorption. The purpose of this study is to learn more about the pulpal changes in autotransplanted immature teeth whose pulp tissue was removed before transplantation. The experimental material consisted of 16 single-rooted teeth with open apices, from a beagle dog (3 months of age). At day 0, 4 teeth were extracted, the pulpal tissues were removed, and the teeth were then transplanted to their contralateral side. The same procedure was carried out on days 9, 16, and 23, each time for 4 single-rooted teeth. Longitudinal paraffin sections were made for histologic investigation. The results showed that, after 7 days, 2 of the 4 teeth had an ingrowth of new tissue over one fourth of their length. After 14 days, all 4 teeth had ingrowth (> or =one fourth of the pulp chamber). At the 21-day observation, more than half of the pulp chambers of all teeth were filled, and, after 30 days, there was total ingrowth in 3 of the 4 teeth. This new tissue consisted of well-organized and well-vascularized connective tissue.

Unicoronal suture autotransplantation in the rabbit.

INTRODUCTION: Our hypothesis was that a neurocranial suture autograft will, when shielded from dura, grow and be incorporated into the calvarium. METHODS: Growth was monitored by marker separation in three isohistogenic groups of rabbits, between postnatal days 9 and 90. In order to simulate increased neurocapsular expansion force, the left-sided coronal suture of a group of 20 rabbits was immobilised with a resorbable suture on gestational day 25. The other group of 10 rabbits was sham-operated. On postnatal day 9, 10 of the experimental rabbits underwent transplantation of the suture contralateral to the defect resulting from extirpation of the immobilised suture. The transplant was shielded from dural influence by a platinum foil. RESULTS: The growth of the immobilised coronal sutures was severely impaired, and also that of the contralateral unicoronal sutures to a lesser extent. A significant catch-up of growth occurred in the transplanted unicoronal sutures. Overgrowth occurred at the donor sites. CONCLUSION: The results allow us to consider suture transplantation combined with endosteal dura stripping in craniosynostosis surgery.

A histomorphometric analysis of heavily loaded and non-loaded implants.

PURPOSE: To investigate the bone tissue response at the interface of loaded and non-loaded implants used in an orthopedic anchorage system after a continuous, non-axial force application of 5 N over 2 months. MATERIALS AND METHODS: Twenty-nine Brånemark System implants were placed in the zygomatic arches of 5 dogs. After a healing period of 8 weeks, 20 implants (4 in each dog) were loaded during 8 weeks with a large non-axial orthopedic force application of 5 N. This force was directed between the implants and a maxillary splint to move the maxilla forward. Nine implants were not loaded during this period. At the termination of the experiment, all 29 implants were retrieved for radiographic as well as for histologic analysis. Computer-based histomorphometric quantifications were performed via light microscopy and computer software. Bone-metal contact (BMC), bone surface area (BSA) inside the threads, and the bone mirror area (BMA) of the implants were measured. Statistical comparisons between the loaded and non-loaded implants were carried out. In the group of loaded implants a 2-factor analysis of variance was used. RESULTS: There were no statistically significant differences found in BMC, BSA, and BMA between the loaded and non-loaded implants, both for all the threads and for only the cervical region of the implants. Nor were there statistically significant differences between the non-pressure and pressure sides or for different lengths of the loaded implants. DISCUSSION: The loaded implants maintained the osseointegration achieved during the 8-week healing period. CONCLUSIONS: The results of this study indicate that titanium implants can be used as anchorage for orthopedic force application systems.