An experimental model for studies on delayed tooth replantation and ankylosis in rabbits

Exosomes derived from stem cells from apical papilla promote angiogenesis via miR-126 under hypoxia

OBJECTIVES

To explore the effect of exosomal miR-126 derived from stem cells from the apical papilla (SCAPs) under hypoxia on human umbilical vein endothelial cell (HUVEC) angiogenesis.

METHODS

miR-126 mimics plasmids were used to upregulate miR-126 in SCAPs. Internalization of PKH26-labeled exosomes was examined by fluorescent microscopy. CCK-8 assay, Transwell assay, scratch assay, tube formation assay, and Matrigel plug assay were performed to detect the effects of exosomes on the angiogenic ability of HUVECs. The luciferase reporter assay and rescue assay were performed to examine the relationship between miR-126 and sprouty-related, EVH1 domain-containing protein 1 (SPRED1). The involvement of SPRED1 and the extracellular signal-regulated kinase (ERK) signaling pathway was evaluated by western blotting.

RESULTS

miR-126 expression was upregulated in SCAPs and in SCAP-derived exosomes under hypoxia. miR-126 expression was increased in HUVECs when cocultured with SCAP-derived exosomes. Induced overexpression of miR-126 in hypoxic SCAPs and secreted exosomes resulted in enhanced angiogenesis both in vitro and in vivo. Western blot analysis revealed that miR-126-mediated SPRED1 downregulation induced activation of ERK signaling.

CONCLUSIONS

Under hypoxic conditions, exosomes derived from SCAPs can promote HUVEC angiogenesis through expression of miR-126, which subsequently suppresses SPRED1 and activates the ERK signaling pathway.

Comparing the effect of demineralized versus hybrid dentin matrices on inducing bone regeneration in New Zealand white rabbits' Mandibular defect

OBJECTIVES

The aim of this study was to compare the effect of using demineralized dentin matrix (DDM) versus hybrid dentin matrices; Demineralized and undemineralized dentin particles (DDM +UDDM) on inducing bone regeneration in mandibular defects.

DESIGN

The study was conducted on fifty adult New Zealand rabbits, twenty for preparation of experimental materials and thirty for surgical procedures. They were randomly assigned into 3 equal groups as follow one control group: no treatment and two experimental groups including demineralized group: treated with DDM only; and hybrid group: treated with a hybrid of (50% DDM+50% UDD). A rounded critical size defect (10 mm in diameter- 5 mm in depth) was created in the body of mandible. After 3- and 6-weeks post-surgery, the bone regeneration was evaluated by light microscope, scanning electron microscope and histomorphometry.

RESULTS

Histological, histomorphometrical observation and SEM revealed that both dentin matrices had largely resorbed and induced new bone formation at both experimental groups compared to the control group, with statistically higher percentage of new bone formation in the hybrid group.

CONCLUSION

We concluded that although both dentin matrices induced new bone formation; however, hybrid dentin matrix yielded better results compared to DDM group.

Bone marrow mesenchymal stem cell sheets with high expression of hBD3 and CTGF promote periodontal regeneration

The multi-bacterial environment of the oral cavity makes it hard for periodontal regeneration. As a class of antimicrobial peptide, beta defensin has been found to show broad-spectrum antibacterial ability. In addition, connective tissue growth factor (CTGF) is demonstrated to play a great role in multi-physiological events such as angiogenesis, wound healing and, more importantly, fibrogenesis. In this study, human β defensin 3 (hBD3) and CTGF were co-transfected into bone marrow derived mesenchymal stem cells (BMSCs) for preparing cell sheets. The transfection efficiency was detected through fluorescence of eGFP and western blot assay. Our results showed that the hBD3 and CTGF proteins were highly and stably expressed in the BMSCs after transfection. The results of RT-PCR and induced differentiation indicated that hBD3 promoted osteogenic differentiation of BMSCs, while CTGF significantly increased fibrogenic differentiation even in the presence of hBD3. The BMSCs acquired stronger capacity in terms of promoting M2 polarization of RAW 264.7 macrophages fulfilled by the transfection and secretion of hBD3 and CTGF. To further evaluate the periodontal remodeling performance of cell sheets, a coralline hydroxyapatite (CHA)-chitosan based hydrogel-human tooth system was designed to simulate the natural periodontal environment. The results showed that dense extracellular matrix, oriented fiber arrangement, and abundant collagen deposition appeared in the area of BMSCs sheets after subcutaneous transplantation. Altogether, our data showed that the lentivirus transfected BMSCs sheets had a promising application prospect for periodontal repair.

Low-intensity pulsed ultrasound attenuates replacement root resorption of avulsed teeth stored in dry condition in dogs

This study aimed to investigate the effects of low-intensity pulsed ultrasound (LIPUS) on replacement root resorption after replantation of avulsed teeth stored in a dry condition in dogs. A total of 73 premolar roots from four male mongrel dogs were intentionally avulsed with forceps and divided into four groups—HN, HL, DN, and DL—according to storage conditions and whether or not they received LIPUS treatment. Thirty-eight roots were kept in Hanks’ Balanced Salt Solution for 30 min (HN and HL groups), whereas the remaining 35 roots were left to dry in the air for an hour (DN and DL groups) prior to replantation. Following replantation, the roots in the HL and DL groups (21 and 18 roots, respectively) received a 20-min daily LIPUS treatment for 2 weeks. The animals were euthanized 4 weeks after the operation. Micro-computed tomography images were acquired for each root and the amount of replacement root resorption was measured three-dimensionally. Histological assessments were also carried out. There was significantly less replacement root resorption for the roots in the DL group compared to the DN group (p < 0.01). Histological findings in the DN group demonstrated evident replacement root resorption, whereas the DL group revealed less severe resorption compared to the DN group. Within the limitations, these results suggest that LIPUS could attenuate the replacement resorption of avulsed teeth stored in a dry condition, thereby improving their prognosis.

Histological Evaluation of Periradicular Tissue Inflammatory Reactions and Calcified Tissue Formations After Implantation of Experimental Calcium Silicate and Hydroxyapatite Based Nanostructural Cements Into Root Canals of Rabbits Teeth

The aim of the study was to evaluate inflammatory tissue reactions and the formation of calcified tissue after implantation of experimental nanostructured calcium silicate cement (CS) and hydroxyapatite with calcium silicate cement (HA-CS) into root canals of rabbits’ teeth. The study was conducted on four rabbits of the genus Oryctolagus cuniculus. After instrumentation and irrigation, the root canals of the central incisors were dried and filled with CS, HA-CS and control material (MTA Angelus). The animals were sacrificed after 28 days. After histological preparation and hematoxylin-eosin staining, tissue samples were evaluated for the intensity and extension of inflammatory tissue reaction; continuity, morphology and thickness of the newly formed calcified tissue; and presence of giant cells, materials particles and microorganisms. Kruskal Wallis and Dunn’s post hoc test were used for data analysis (α=0.05). There were no significant differences in the intensity of inflammatory reactions between CS, HA-CS and MTA control. HA-CS showed significantly better results than MTA and CS with respect to continuity of the newly formed calcified tissue (P=0.003 and P=0.010, respectively). Significant differences in thickness of the calcified tissue existed between CS and MTA (P=0.004) and between HA-CS and MTA (P=0.012). Application of CS and HA-CS resulted in minimal inflammatory tissue response, similar to the MTA control. CS and HA-CS were more efficient than MTA in supporting hard tissue formation. The best organized newly formed calcified tissue was seen after HA-CS application.

Effect of root surface treatment with denusomab after delayed tooth replantation

OBJECTIVES

To evaluate denosumab, a human monoclonal antibody that mimics the effects of osteoprotegerin in bone metabolism, as a topical treatment of root surface to be used prior to delayed tooth replantation.

MATERIALS AND METHODS

Thirty-six rats' right incisors were used. Teeth were extracted and divided into: delayed replantation without root surface treatment (control); delayed replantation with root surface treatment with denosumab 60 mg/mL and 30 mg/mL, respectively, for 10 min both experimentals groups. After that, the root canals were filled with calcium hydroxide and replanted. After 15 and 60 days, the animals were euthanized, and the samples were collected and processed for microscopic analysis. Histological sections were performed, and stained with HE to describe the dental characteristics, measure ankylosis, replacement resorption, and dental resorption by conventional microscopy. Also, was performed Brown & Brenn staining and immunohistochemistry for RANKL, OPG, and periostin.

RESULTS

Denosumab 60 mg/mL reducted ankylosis (p < 0.0001), replacement resorption (p < 0.0001), and tooth resorption, 60 days after replantation, compared to untreated replanted teeth (p < 0.005). Lower bacterial contamination in root surface in the denosumab treatment groups was found, regardless of the concentration used (p < 0.001). Also, denosumab treatment inhibited the expression of RANKL without modulating OPG. Periostin was observed in periodontal ligament of replanted tooth, although this labelling was absent in the ankylosis areas, in both experimental periods.

CONCLUSION

Treatment of the root surface with denosumab at 60 mg/mL of rat teeth before delayed replantation reduced dental root resorption compared with the untreated teeth after 60 days.

CLINICAL RELEVANCE

Survival of a replanted tooth has been a challenge in clinical practice. The use of a medication, such as denosumab, to limit dental root resorption represents an important therapeutical approach.

The effect of cathepsin K inhibitor surface treatment on delayed tooth replantation in dogs

BACKGROUND/AIM

Continuous research efforts have been focusing on promoting healing of delayed replantation of avulsed teeth. The aim of this in vivo study was to assess the effect of cathepsin K inhibitor surface treatment on delayed tooth replantation.

MATERIALS AND METHODS

Thirty-four premolar roots of 4 beagle dogs were extracted, and conventional root canal treatment was performed. The canals were filled with gutta-percha and cement. All extracted teeth were air-dried for 1 hour. Teeth were divided into 2 groups according to the root surface treatment prior to replantation: control (n = 13) and cathepsin K inhibitor (n = 21). Treated teeth were replanted in their original sockets and stabilized with a resin-wire splint for 1 week. After 12 weeks, the dogs were euthanized and micro-computed tomography was performed. Tissues were then further processed as resin-embedded specimens stained with hematoxylin and eosin. In each evaluation, data were analyzed using the Mann-Whitney U test (P < .05).

RESULTS

In the micro-computed tomography evaluation, inflammation scores of both groups were not statistically different (P > .05). In the histological evaluation, the mean proportions of inflammatory resorption and replacement resorption in the control group were similar to those in the cathepsin K inhibitor group (P > .05).

CONCLUSIONS

Cathepsin K inhibitor did not demonstrate significant inhibitory effects on root resorption after delayed replantation in vivo.

Effect of periodontal ligament removal with gauze prior to delayed replantation in rabbit incisors on rate of replacement resorption

BACKGROUND/AIM

Delayed (dry storage > 60 minutes) replantation results in ankylosis and replacement resorption. It has been suggested to remove the non-viable periodontal ligament before replantation to possibly reduce the rate of replacement resorption. However there has been no study on the rate of replacement resorption after such measures. The aim of this study was to investigate if there was any difference in the rate of replacement resorption by either removing the periodontal ligament (PDL) with gauze or not removing PDL in teeth subjected to delayed replantation followed by healing for 2 or 6 weeks.

MATERIALS AND METHODS

Maxillary central incisors were extracted in 8 rabbits. In the right central incisors, the necrotic PDL was removed by dry gauze over the root surface. In the left eight extracted teeth PDL was left on the root surface. All extracted teeth were left to dry for 60 minutes. Extra-oral root canal treatment was performed before replantation. The rabbits were sacrificed after 2 weeks and 6 weeks respectively. Histologic processing and evaluation was done.

RESULTS

In the 2 weeks group, all teeth showed ankylosis. The cementum was intact, and fusion of the bone and root was generally seen without resorption of the root, whereas in the 6 weeks group regardless of whether PDL had been kept or not, ankylosis and osseous replacement of the dentin was seen. There was no evidence of inflammatory infiltrate in the sections examined.

CONCLUSION

Removal of PDL prior to delayed replantation may result in some initial protection of the cementum during the first few weeks. However, over longer times there seems to be neither protection of the dentin from ankylosis and osseous replacement, nor any influence on the rate of replacement resorption.

Bone regeneration using composite non-demineralized xenogenic dentin with beta-tricalcium phosphate in experimental alveolar cleft repair in a rabbit model

Background

Alveolar cleft repair is performed via bone grafting procedure to restore the dental arch continuity. A suitable bone substitute materials should possess osteoinductive and osteoconductive properties, to promote new bone formation, along with a slowly resorbable scaffold that is subsequently replaced with functionally viable bone. Calcium phosphate biomaterials have long proved their efficacy as bone replacement materials. Dentin in several forms has also demonstrated its possibility to be used as bone graft replacement material in several studies. The purpose of this study was to evaluate bone regeneration pattern and quantify bone formation after grafting pre-established experimental alveolar clefts defects model in rabbits using composite xenogenic dentin and β-TCP in comparison to β-TCP alone.

Methods

Unilateral alveolar cleft defects were created in 16 New Zealand rabbits according to previously described methodology. Alveolar clefts were allowed 8 weeks healing period. 8 defects were filled with β-TCP, whereas 8 defects filled with composite xenogenic dentin with β-TCP. Bone regeneration of the healed defects was compared at the 8 weeks after intervention. Quantification of bone formation was analyzed using micro-computed tomography (µCT) and histomorphometric analysis.

Results

µCT and histomorphometric analysis revealed that defects filled with composite dentin/β-TCP showed statistically higher bone volume fraction, bone mineral density and percentage residual graft volume when compared to β-TCP alone. An improved surgical handling of the composite dentin/β-TCP graft was also noted.

Conclusions

Composite xenogenic dentin/β-TCP putty expresses enhanced bone regeneration compared to β-TCP alone in the reconstruction of rabbit alveolar clefts defects.

A rabbit model for experimental alveolar cleft grafting

Objectives

The purpose of the present study was to develop an animal model for creating alveolar cleft defects with properly simulated clinical defect environment for tissue-engineered bone-substitute materials testing without compromising the health of the animal. Cleft creation surgery was aimed at creating a complete alveolar cleft with a wide bone defect with an epithelial lining (oral mucosa) overlying the cleft defect.

Methods

A postmortem skull of a New Zealand White (NZW) rabbit skull (Oryctolagus cuniculus) underwent an osteological and imaging survey. A pilot postmortem surgery was conducted to confirm the feasability of a surgical procedure and the defect was also radiologically confirmed and illustrated with micro-computed tomography. Then, a surgical in vivo model was tested and evaluated in 16 (n = 16) 8-week-old NZW rabbits to create in vivo alveolar cleft creation surgery.

Results

Clinical examination and imaging analysis 8 weeks after cleft creation surgery revealed the establishment of a wide skeletal defect extending to the nasal mucosa simulating alveolar clefts in all of the rabbits.

Conclusions

Our surgical technique was successful in creating a sizable and predictable model for bone grafting material testing. The model allows for simulating the cleft site environment and can be used to evaluate various bone grafting materials in regard to efficacy of osteogenesis and healing potential without compromising the health of the animal.