Tooth eruption through autogenous and xenogenous bone transplants: a histological and radiographic evaluation in beagle dogs

A biomimetic self-assembling peptide promotes bone regeneration in vivo: A rat cranial defect study

Rationally designed, pH sensitive self-assembling β-peptides (SAPs) which are capable of reversibly switching between fluid and gel phases in response to environmental triggers are potentially useful injectable scaffolds for skeletal tissue engineering applications. SAP P₁₁-4 (CH₃COQQRFEWEFEQQNH₂) has been shown to nucleate hydroxyapatite mineral de novo and has been used in dental enamel regeneration. We hypothesised that addition of mesenchymal stromal cells (MSCs) would enhance the in vivo effects of P₁₁-4 in promoting skeletal tissue repair. Cranial defects were created in athymic rats and filled with either Bio-Oss® (anorganic bone chips) or P₁₁-4 ± human dental pulp stromal cells (HDPSCs). Unfilled defects served as controls. After 4 weeks, only those defects filled with P₁₁-4 alone showed significantly increased bone regeneration (almost complete healing), compared to unfilled control defects, as judged using quantitative micro-CT, histology and immunohistochemistry. In silico modelling indicated that fibril formation may be essential for any mineral nucleation activity. Taken together, these data suggest that self-assembling peptides are a suitable scaffold for regeneration of bone tissue in a one step, cell-free therapeutic approach.

Bone regeneration with bovine bone impairs orthodontic tooth movement despite proper osseous wound healing in a novel mouse model

BACKGROUND

The aim of this study was to investigate the biological mechanisms underlying alveolar bone regeneration (ABR) and orthodontic tooth movement into bovine bone (BB) regenerated sites.

METHODS

Two mouse models were established in C57BL/6 mice. The ABR model was based on osseous defects filled with BB. The orthodontic tooth movement-ABR model was used to move a molar into the regenerated site. Osseous morphometric analysis and tooth movement distance were evaluated with micro-CT. Histologic characteristics and osteoclast (OCS) accumulation were evaluated by hematoxylin and eosin and tartrate-resistant acid phosphatase staining (TRAP). Expression and location of the receptor activator of nuclear factor-kappa B (RANKL) and of osteoprotegerin (OPG) were evaluated by immunofluorescent staining.

RESULTS

Bone healing peaked at 4 weeks. The distance of the orthodontic tooth movement into the bovine bone was significantly reduced versus that of the nonbovine bone controls. BB particles accumulated along the root's pressure side during orthodontic treatment. Despite the osteoclasts' presence adjacent to the BB particles, no BB resorption was observed. Increased RANKL expression was seen at the orthodontic tooth movement pressure zone, without any change in OPG expression.

CONCLUSION

The two novel mouse models show that the lack of resorption of BB xenografts renders them inadequate for proper orthodontic tooth movement at a later stage.

Mid versus late secondary alveolar cleft grafting using iliac crest corticocancellous bone graft

BACKGROUND

Mid-secondary alveolar cleft repair performed at ages 9-12, in the mixed dentition stage, prior to eruption of the permanent canine, is generally accepted as the ideal time for residual alveolar cleft closure in cleft lip and palate cases with a cleft alveolus.

METHODS

In our study, four cases of mid-secondary and five cases of late-secondary alveolar cleft grafting were carried out using iliac crest corticocancellous bone graft. Clinical defect closure and radiographic bone fill were compared.

RESULTS

All the nine cases performed in the two different age groups showed excellent results, clinically, with complete closure of the cleft defect and achievement of continuity of the dental arches. One case was planned for a two-stage procedure owing to the large bilateral maxillary defects. Good bone fill was visualized radiographically in all nine cases.

CONCLUSION

Precise timing for undertaking alveolar cleft repair may not be all that crucial for a successful alveolar cleft grafting procedure.

A comparison of autogenous bone graft combined with deproteinized bovine bone and autogenous bone graft alone for treatment of alveolar cleft

This study assessed the use of composite autogenous bone and deproteinized bovine bone (DBB) for repairing alveolar cleft compared with autogenous bone alone in terms of clinical outcomes and patient morbidity. 30 patients with a mean age of 10.2±1.7 years were randomly divided into two groups. Group I used autogenous cancellous bone graft harvested from the anterior iliac crests by the conventional trapdoor approach. Group II used a composite of DBB and autogenous cancellous bone harvested by a trephine bone collector; the proportion of 1:1 by volume was used. The bone graft quantities of both groups decreased with time. Their average changes were not statistically different over 24 months after grafting. The canines of both groups could spontaneously or orthodontically erupt through the grafting areas. Patients in group II recovered from uncomfortable walking significantly faster than those in group I (p<0.05) and their duration of hospital stay was significantly shorter than those in group I (p<0.05). The average operation time, intra-operative blood loss and postoperative pain were less in group II than in group I (p>0.05).

Orthodontie Treatment Results following Grafting Autologous Mandibular Bone to the Alveolar Cleft in Patients with a Complete Unilateral Cleft

Objective

To analyze orthodontic treatment results following mandibular symphysis bone grafting and postoperative orthodontic treatment.

Design

Randomized selection of 75 patients out of 308 with unilateral cleft of lip, alveolus, and palate, operated upon according to protocol between 1990 and 2008 in the Wilhelmina Children's Hospital, Utrecht, The Netherlands.

Main Outcome Measure

Goslon Yardstick rating changes of dental arch relationship. Significant agreement ( p < .001) was observed between the two assessments carried out with an interval of 3 months (Cohen's kappa = .963, p < .001).

Results

Following mandibular bone grafting and orthodontic treatment in 65.3% of the patients, the aim of treatment (Goslon Yardstick groups 1 and 2) had been achieved. The applied before/after Goslon allocations showed high improvement significance ( p < .001).

Conclusions

Postoperative orthodontic treatment in patients following grafting with mandibular symphysis bone showed excellent results.

Orthodontic movement in bone defects filled with xenogenic graft: An experimental study in minipigs

INTRODUCTION

In this study, we investigated whether it is possible to orthodontically move a tooth into an adjacent bone defect previously filled with xenogenic grafting material, with emphasis on the reactions of the tooth roots and adjacent tissues.

METHODS

Six minipigs were used. In each animal, 4 defects were created at the mesial aspects of the maxillary and mandibular first permanent molars; the defects on the right were filled with the xenograft (test side), and the opposite defects (control side) were filled with blood clots and allowed to heal spontaneously. Three months later, orthodontic appliances were placed in each quadrant to allow mesial bodily movement of the first permanent molars. When the teeth were moved about halfway into the defect spaces, the animals were killed, and the areas of interest were harvested. The mesial roots of the first molars and adjacent tissues were histologically and morphometrically evaluated. The volume density of bone tissue, the percentage of root resorption, and the bone height were evaluated with image analysis software.

RESULTS

Data analysis showed that (1) the percentage of root resorption was smaller (P = .0359) for the test group (4.16%) compared with the control (6.52%); (2) there was no statistically significant differences between groups concerning the volume density of neoformed bone (P >.05); (3) the bovine bone matrix was almost totally replaced by structured bone tissue; (4) the test group had a statistically significant smaller bone height loss (2.18 mm, P = .0018) than the control group (3.26 mm).

CONCLUSIONS

Based on these results, it was concluded that teeth can be moved into areas of bone defects previously filled with xenograft.

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.

Tooth eruption into the newly generated bone induced by recombinant human bone morphogenetic protein-2

OBJECTIVE

The purpose of this study was to observe tooth eruption pattern into the newly generated bone induced by recombinant human bone morphogenetic protein-2 (rhBMP-2).

METHOD

Three 12-week-old beagle dogs were used. Following wound healing of the extracted maxillary third deciduous incisor at the age of 13 weeks, a resection of maxillary alveolar bone (8 mm by 8 mm by 8 mm) was carried out, accompanied by extraction of the maxillary second incisor tooth germ. The rhBMP-2 (5 microgram/100 microL or 10 microgram/100 microL) was implanted in the resected area. A group that was not implanted after resection and a nonresected group were used as controls. Serial changes of the eruption pattern of the maxillary third incisor in the implanted area were observed radiographically. Oxytetracycline and calcein were employed as bone markers. Nine weeks after the implantation, the animals were sacrificed. The samples were observed histologically and analyzed using peripheral quantitative computerized tomography to acquire the bone mineral density (BMD).

RESULTS

In the rhBMP-2 (5 microgram/100 microL)-treated group, histological findings and the BMD of the newly generated bone were almost same as in the nonresected group. The maxillary third incisor erupted through the implanted area. However, in the rhBMP-2 (10 microgram/100 microL)-treated group, more osteoinductive activity and significantly higher BMD were observed in the newly generated bone. The maxillary third incisor erupted mesially so as to avoid this implanted area.

CONCLUSION

Results showed that bone remodeling and tooth eruption through the newly generated bone appear to be dose dependent. Accordingly, proper dosage of rhBMP-2 should be determined for successful clinical application.

Qualitative assessment of natural apatite in vitro and in vivo

Among the natural and synthetic materials investigated as bone graft substitutes, much interest has been focused on natural apatite obtained from low temperature heat-deproteinated compact bone. Previous research demonstrates that, when treated at a temperature below 500 degrees C, this material maintains its characteristic ultrastructural features, with a high surface/volume ratio, while as an implant material, it offers the host tissue a large surface of interaction. In vitro and in vivo tests showed that natural apatite is well tolerated and is a good osteoconducing material. The present in vivo study in rabbits was carried out to first investigate the behavior and capacity of natural apatite implants to stimulate bone ingrowth, and then to analyze the cells located at the bone/material interface. Synthetic hydroxyapatite was used as a control material. In a parallel in vitro study, we investigated the activity of differentiated osteoblasts and periosteal cells obtained from rats and new-born rabbits, incubated with natural apatite and synthetic hydroxyapatite. The in vivo study showed that natural apatite allows osteoblasts to form new bone tissue, adhering to the implant with ingrowth into the implant structure. In the presence of synthetic hydroxyapatite, a less pronounced osteoblastic activity was observed. In agreement with these observations, the in vitro study showed that natural apatite is more effective in attracting cells, favoring their proliferation and stimulating alkaline phosphatase activity. These findings suggest that natural apatite is more suitable for bone filling or bone regeneration than synthetic hydroxyapatite.

Incorporation of particulated bone implants in the facial skeleton

The purpose of this study was to compare the regenerative response of autogenous cortical and cancellous bone chips and a natural particulate resorbable bone mineral (RBM) (Bio-Oss, Geistlich-Pharma, Wolhusen, Switzerland) in standardized bony defects relating paranasal sinuses to one another and to bone blocks. On 13 skeletally mature female goats four standardized critical-sized full thickness bone defects were made in the frontal bone overlying the frontal sinus. These defects were filled at random with cortical bone chips, cancellous bone chips, spongiosa granules of a RBM or left empty. Fluorochrome bone markers were injected subcutaneously 1 and 5 weeks after transplantation, and one week before the animals were killed. The animals were killed at 3, 6, 12 and 24 weeks after surgery. Autogenous cancellous bone chips is the material of choice for bridging a bony defect in the maxillofacial area where there is no need for mechanical strength. They heal in the same way as cancellous bone blocks do. Cortical bone chips are not reliable enough to be used as a solitary bone-grafting material under these conditions. A cortical block as a solitary implant gives better results. RBM granules as solitary implant in a critical-sized defect do not stimulate osteoconduction but give rise to an extensive osteoclastic activity stimulated by the mutual loose relation. A solid block of RBM is in a similar case more reliable.