Reduced functional loads alter the physical characteristics of the bone-periodontal ligament-cementum complex

Niver EL, Leong N, Greene J, Curtis D, Ryder MI, Ho SP. Reduced functional loads alter the physical characteristics of the bone–periodontal ligament–cementum complex. J Periodont Res 2011; 46: 730–741. © 2011 John Wiley & Sons A/S Background and Objective: Adaptive properties of the bone–periodontal ligament–tooth complex have been identified by changing the magnitude of functional loads using small‐scale animal models, such as rodents. Reported adaptive responses as a result of lower loads due to softer diet include decreased muscle development, change in structure–function relationship of the cranium, narrowed periodontal ligament space, and changes in the mineral level of the cortical bone and alveolar jaw bone and in the glycosaminoglycans of the alveolar bone. However, the adaptive role of the dynamic bone–periodontal ligament–cementum complex to prolonged reduced loads has not been fully explained to date, especially with regard to concurrent adaptations of bone, periodontal ligament and cementum. Therefore, in the present study, using a rat model, the temporal effect of reduced functional loads on physical characteristics, such as morphology and mechanical properties and the mineral profiles of the bone–periodontal ligament–cementum complex was investigated. Material and Methods: Two groups of 6‐wk‐old male Sprague–Dawley rats were fed nutritionally identical food with a stiffness range of 127–158 N/mm for hard pellet or 0.3–0.5 N/mm for soft powder forms. Spatio‐temporal adaptation of the bone–periodontal ligament–cementum complex was identified by mapping changes in the following: (i) periodontal ligament collagen orientation and birefringence using polarized light microscopy, bone and cementum adaptation using histochemistry, and bone and cementum morphology using micro‐X‐ray computed tomography; (ii) mineral profiles of the periodontal ligament–cementum and periodontal ligament–bone interfaces by X‐ray attenuation; and (iii) microhardness of bone and cementum by microindentation of specimens at ages 6, 8, 12 and 15 wk. Results: Reduced functional loads over prolonged time resulted in the following adaptations: (i) altered periodontal ligament orientation and decreased periodontal ligament collagen birefringence, indicating decreased periodontal ligament turnover rate and decreased apical cementum resorption; (ii) a gradual increase in X‐ray attenuation, owing to mineral differences, at the periodontal ligament–bone and periodontal ligament–cementum interfaces, without significant differences in the gradients for either group; (iii) significantly (p < 0.05) lower microhardness of alveolar bone (0.93 ± 0.16 GPa) and secondary cementum (0.803 ± 0.13 GPa) compared with the higher load group insert bone = (1.10 ± 0.17 and cementum = 0.940 ± 0.15 GPa, respectively) at 15 wk, indicating a temporal effect of loads on the local mineralization of bone and cementum. Conclusion: Based on the results from this study, the effect of reduced functional loads for a prolonged time could differentially affect morphology, mechanical properties and mineral variations of the local load‐bearing sites in the bone–periodontal ligament–cementum complex. These observed local changes in turn could help to explain the overall biomechanical function and adaptations of the tooth–bone joint. From a clinical translation perspective, our study provides an insight into modulation of load on the complex for improved tooth function during periodontal disease and/or orthodontic and prosthodontic treatments.     

Mechanical stimulation induces CTGF expression in rat osteocytes

Connective tissue growth factor (CTGF), which is encoded by an immediate early gene and a member of the CCN family, has been shown to be expressed in osteoblasts, fibroblasts, and chondrocytes. Although CTGF is expressed in bone and cartilage tissues, we tested the hypothesis that CTGF is regulated in mechanotransduction. In the alveolar bone during experimental tooth movement, CTGF mRNA was expressed in osteoblasts and in osteocytes localized around the periodontal ligament under control conditions. Interestingly, 12 hrs after the start of experimental tooth movement, the expression of CTGF mRNA in osteocytes and osteoblasts became more intense around the periodontal ligament, and the intense expression of CTGF extended to osteocytes situated deep in alveolar bone matrix apart from periodontal ligament in both tension and compression sides. Our present findings indicate that CTGF could play a role in regulation of osteocyte function during the mechanical stimulation of bone.     

Histological,immunohistochemical and radiographic evaluation of Amitriptyline administration on the periodontium of albino rats (An experimental study)

BackgroundAmitriptyline is a tricyclic antidepressant drug accustomed to treat depressive disorders. It recorded many side effects on different tissues.ObjectiveTo investigate reaction of Albino rats’ periodontium after oral administration of Amitriptyline histologically and radiographically.MethodsFourteen adult male albino rats (150–200 g) were divided into two groups, control and experimental. Rats of experimental group received 10 mg?kg?day of Amitriptyline hydrochloride by oral gavage for four weeks. Mandibles were prepared for hematoxylin and eosin (H&E) and anti-osteopontin (Anti-OPN) immunohistochemistry staining. Bone mineral density was measured in mandibular alveolar bone. Statistical analysis for Anti-OPN and relative Hounsfield unit value (HU value) was performed using independent-samples t-test.ResultsGingiva of experimental group showed epithelial degeneration with pyknotic nuclei and disintegration in lamina propria. Areas of separation in alveolar bone and degeneration of some regions in cementum were seen with apparent increase in periodontal ligament (PDL) thickness and its detachment from bone and cementum at some regions. Immunohistochemical examination of experimental group showed apparently increased immunopositivity in gingiva, cementocytes, osteocytes, cementum, bone matrices, fibroblasts and PDL fibers when compared to control group. Statistical analysis revealed insignificant difference of Anti-OPN area% in gingiva between both studied groups. While there was statistical significant increase of Anti-OPN area% in the other periodontium tissues and high statistical significant decrease of relative HU value in experimental group when compared to control.ConclusionsAmitriptyline has destructive effect on periodontal tissues and statistically increases the expression of Anti-OPN in all periodontal tissues except gingiva and decreases bone mineral density.     

Morphological characteristics of the depository surface of alveolar bone of diabetic mice

Sharpey's fibers support teeth by attachment of periodontal ligament fibers to alveolar bone. The effects of diabetes mellitus on this support mechanism have not been described and were the subject of this study. Male Swiss mice were rendered diabetic by streptozotocin. Mandibles were removed 9 weeks after injections, the mineralizing front of the depository surface of the interdental septum was exposed by fracture through the periodontal ligament, rendered anorganic, and examined by scanning electron microscopy. No significant reduction in alveolar crest height was evident in diabetic as compared to control animals; however, significant changes in the a) mineralization patterns of bone depository surfaces and Sharpey's fibers, and b) number of Sharpey's fibers inserting into alveolar bone were evident in diabetics. Unmineralized fissures, characteristic of Sharpey's fibers of control, were nearly obliterated by mineralized tissue in diabetic animals. The mineralizing front of the middle and apical thirds of the diabetic alveolar wall was covered by numerous large calcified globules resembling enlarged calcospherites, which were not evident over the cervical third or control tissues. The mean Sharpey fiber density was greater in controls than in diabetics (p less than 0.001); however, there was no significant difference between their mean diameters. These observations suggest that, in early diabetes, Sharpey's fibers and depository surfaces of the middle and apical thirds of the interdental septum have morphologic evidence of aging, which precedes significant reduction in alveolar crest height. These changes may weaken the attachment of periodontal ligament fibers to bone and reduce resistance of the periodontium to intrusive forces.     

Effects of adenoviral‐mediated coexpression of bone morphogenetic protein‐7 and insulin‐like growth factor‐1 on human periodontal ligament cells

Yang L, Zhang Y, Dong R, Peng L, Liu X, Wang Y, Cheng X. Effects of adenoviral‐mediated coexpression of bone morphogenetic protein‐7 and insulin‐like growth factor‐1 on human periodontal ligament cells. J Periodont Res 2010; 45: 532–540. © 2010 John Wiley & Sons A/S Background and Objective: Bone morphogenetic protein‐7 (BMP‐7) and insulin‐like growth factor‐1 (IGF‐1) are important in periodontal reconstruction. However, their synergistic effect in periodontal regeneration by gene delivery has not been reported. In this study, gene delivery of these two growth factors to human periodontal ligament cells (hPDLCs) was examined for its effects on cell proliferation and differentiation. Material and Methods: Recombinant adenoviruses containing both human BMP‐7 and IGF‐1 cDNA created by introducing the internal ribosome entry site (IRES) sequence were used to transfer the genes into hPDLCs. 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and cell cycle analysis were used to observe their effects on cell proliferation, while alkaline phosphatase activity measurement, RT‐PCR and in vivo tests were conducted to investigate their effects on cell differentiation. Results: The proliferation of hPDLCs transduced by adenoviruses coexpressing BMP‐7 and IGF‐1 was suppressed while their differentiation ability was enhanced. There was a synergism of BMP‐7 and IGF‐1 in up‐regulating alkaline phosphatase activity and mRNA levels of collagen type I and Runx2. Implantation in vivo with scaffolds illustrated that the transduced cells exhibited osteogenic differentiation and formed bone‐like structures. Conclusion: The combined delivery of BMP‐7 and IGF‐1 genes using an IRES‐based strategy synergistically enhanced differentiation of hPDLCs. It is suggested that this could be a new potential method in gene therapy for periodontal reconstruction.     

Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro

An S, Ling J, Gao Y, Xiao Y. Effects of varied ionic calcium and phosphate on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells in vitro. J Periodont Res 2012; 47: 374–382. ©2011 John Wiley & Sons A/S Background and Objective: A number of bone‐filling materials containing calcium (Ca²⁺) and phosphate (P) ions have been used in the repair of periodontal bone defects; however, the effects that local release of Ca²⁺ and P ions has on biological reactions are not fully understood. In this study, we investigated the effects of various levels of Ca²⁺ and P ions on the proliferation, osteogenic differentiation and mineralization of human periodontal ligament cells (hPDLCs). Material and Methods: The hPDLCs were obtained using an explant culture method. Defined concentrations and ratios of ionic Ca²⁺ to inorganic P were added to standard culture and osteogenic induction media. The ability of hPDLCs to proliferate in these growth media was assayed using the Cell Counting Kit‐8. Cell apoptosis was evaluated by the fluorescein isothiocyanate–annexin V/propidium iodide double‐staining method. Osteogenic differentiation and mineralization were investigated by morphological observations, alkaline phosphatase activity and Alizarin Red S/von Kossa staining. The mRNA expression of osteogenic related markers was analysed using RT‐PCR. Results: Within the ranges of Ca²⁺ and P ion concentrations tested, we observed that increased concentrations of Ca²⁺ and P ions enhanced cell proliferation and formation of mineralized matrix nodules, whereas alkaline phosphatase activity was reduced. The RT‐PCR results showed that elevated concentrations of Ca²⁺ and P ions led to a general increase of Runx2 mRNA expression and decreased alkaline phosphatase mRNA expression, but gave no clear trend on osteocalcin mRNA levels. Conclusion: The concentrations and ratios of Ca²⁺ and P ions could significantly influence proliferation, differentiation and mineralization of hPDLCs. Within the range of concentrations tested, we found that the combination of 9.0 mm Ca²⁺ ions and 4.5 mm P ions were the optimal concentrations for proliferation, differentiation and mineralization in hPDLCs.     

Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein-2 on periodontal regeneration

Song D‐S, Park J‐C, Jung I‐H, Choi S‐H, Cho K‐S, Kim C‐K, Kim C‐S. Enhanced adipogenic differentiation and reduced collagen synthesis induced by human periodontal ligament stem cells might underlie the negative effect of recombinant human bone morphogenetic protein‐2 on periodontal regeneration. J Periodont Res 2011; 46: 193–203. © 2010 John Wiley & Sons A/S Background and Objective: Recombinant human bone morphogenetic protein‐2 (rhBMP‐2) is a potent inducer for the regeneration of mineralized tissue, but has a limited effect on the regeneration of cementum and periodontal ligament (PDL). The aim of the present study was to determine the effects of rhBMP‐2 on the in vitro and in vivo biologic activity of well‐characterized human PDL stem cells (hPDLSCs) and to elucidate the underlying mechanism of minimal periodontal regeneration by rhBMP‐2. Material and Methods: hPDLSCs were isolated and cultured, and then transplanted into an ectopic subcutaneous mouse model using a carrier treated either with or without rhBMP‐2. Comprehensive histologic, histometric and immunohistochemical analyses were performed after an 8‐wk healing period. The effects of rhBMP‐2 on the adipogenic and osteogenic/cementogenic differentiation of hPDLSCs were also evaluated. The effect of rhBMP‐2 on both soluble and insoluble collagen synthesis was analyzed, and the expression of mRNA and protein for collagen types I, II, III and V was assessed. Results: In the present study, rhBMP‐2 promoted both adipogenic and osteogenic/cementogenic differentiation of hPDLSCs in vitro, and the in vivo potential of hPDLSCs to form mineralized cementum and organized PDL tissue was down‐regulated following treatment with rhBMP‐2. Collagen synthesis, which plays a crucial role in the regeneration of cementum and the periodontal attachment, was significantly reduced, with associated modification of the relevant mRNA and protein expression profiles. Conclusion: In summary, the findings of the present study suggest that enhanced adipogenic differentiation and inhibition of collagen synthesis by hPDLSCs appear to be partly responsible for the minimal effect of rhBMP‐2 on cementum and PDL tissue regeneration by hPDLSCs.     

Fibulins and matrilins are novel structural components of the periodontium in the mouse

Periodontitis refers to inflammatory disease of the periodontal structures (the gingiva, dental cementum, periodontal ligament (PDL) and alveolar bone) that ultimately leads to their destruction. Whereas collagens are well-examined main components of the periodontium, little is known about the other structural proteins that make up this tissue. The aim of this study was to identify new extracellular matrix (ECM) components, including fibulins and matrilins, in the periodontium of mice.After sacrificing 14 mice (Sv/129 strain), jaws were prepared. Each tissue sample contained a molar and its surrounding alveolar bone. Immunohistochemistry was carried out on paraffin-embedded sections.Our results show that mice exhibit fibulin-3, -4 and -5 and matrilin-1, -2, -3 and -4 in PDL and in blood vessels of alveolar bone and PDL as well as in the pericellular matrix of osteocytes and cementocytes. In dental cementum, only fibulin-4 is expressed.For the first time, we show that fibulin-3, -4 and -5 and matrilin-1, -2, -3 and -4 are essential components of the periodontal tissues. Our findings indicate an association of these proteins with collagens and oxytalan fibers that might be of future interest in regenerative periodontitis therapy.     

Aging affects the phenotypic characteristics of human periodontal ligament cells and the cellular response to hormonal stimulation in vitro

Lossdörfer S, Kraus D, Jäger A. Aging affects the phenotypic characteristics of human periodontal ligament cells and the cellular response to hormonal stimulation in vitro. J Periodont Res 2010; 45: 764–771. © 2010 John Wiley & Sons A/S Background and Objective: Aging modulates the proliferative activity and organic matrix production of cells in vivo and in vitro. Here, we explore how aging affects the phenotypic characteristics of human periodontal ligament cells and their response to hormonal stimulation. Material and Methods: Fifth passage periodontal ligament cells from subjects aged 12–14 (group 1), 41–55 (group 2) and 61–70 years (group 3) were characterized for the expression of mesenchymal marker genes and proteins by real‐time PCR and flow cytometry. Confluent cultures were exposed to 10^?12 m parathyroid hormone(1–34) [PTH(1–34)] intermittently for three cycles. At harvest, cell number, alkaline phosphatase activity and osteocalcin production were determined by cell count, biochemical assay and ELISA. Results: The characterization of the cells revealed a decreased expression of osteoblast‐specific marker genes along with a lower percentage of cells presenting the respective proteins with age. An intermittent exposure of the cultures to 10^?12 m PTH(1–34) induced an increase of the cell number as opposed to a significant decrease of alkaline phosphatase activity and osteocalcin production. The cellular response to PTH(1–34) was strongest in group 1. Basal osteoprotegerin levels were highest in the cultures from the oldest donors and inhibited by intermittent PTH(1–34) in all groups. Conclusion: Our data indicate that periodontal ligament cells from older subjects display a less differentiated phenotype and a reduced response to intermittent PTH, suggesting a compromised ability to maintain tissue homeostasis and a limited possibility to support periodontal repair processes with age. The high basal osteoprotegerin expression in older subjects might serve as a compensatory mechanism.     

Osteocytic Sclerostin Expression in Alveolar Bone in Rats With Diabetes Mellitus and Ligature‐Induced Periodontitis

Background: Osteocytic sclerostin inhibits bone formation, and its expression is stimulated by tumor necrosis factor (TNF)‐α. This study investigates sclerostin and TNF‐α expression in rats with diabetes mellitus (DM) and periodontitis. Methods: Rats were divided into control (C), periodontitis (P), and DM + periodontitis (DP) groups. After induction of DM by streptozotocin, periodontitis was induced by ligature. At day 0 (control) and at days 3 and 20 after induction of periodontitis, alveolar bone, osteoclasts, osteoid area, and TNF‐α and sclerostin expression were evaluated. Results: The distance between the cemento‐enamel junction and the alveolar bone crest of the DP group was longer than that of the P group at day 20 after induction of periodontitis, but the number of osteoclasts was not different. Osteoid area decreased in both the P and DP groups by day 3, but whereas sustained osteoid suppression was observed in the DP group at day 20, osteoid formation was increased in the P group. The number of sclerostin‐positive osteocytes increased in both groups at day 3, but the increased number of sclerostin‐positive osteocytes was maintained only in the DP group through day 20. The number of TNF‐α–positive cells increased more in the DP group than in the P group. Conclusions: Enhanced alveolar bone loss, suppressed bone formation, and prevalent TNF‐α expression were characteristic of the DP group compared with the P group. Suppressed bone formation in the DP group was observed simultaneously with increased sclerostin and TNF‐α expression. These results suggest that upregulated osteocytic sclerostin expression in periodontitis accompanied by DM may play a role in suppressed bone formation.     

Asporin in compressed periodontal ligament cells inhibits bone formation

ObjectiveDuring orthodontic tooth movement, bone resorption and inhibition of bone formation occur on the compressed side, thereby preventing ankylosis. Periodontal ligament (PDL) cells control bone metabolism and inhibition of bone formation on the compressed side by secreting bone-formation inhibitory factors such as asporin (ASPN) or sclerostin (encoded by SOST). The aim of this study was to identify the inhibitory factors of bone formation in PDL cells.DesignIn vitro, the changes in expression of ASPN and SOST and subsequent protein release in human PDL (hPDL) cells were assessed by semi-quantitative polymerase chain reaction (PCR), real-time PCR, and immunofluorescence in hPDL cells subjected to centrifugal force using a centrifuge (45, 90, 135, and 160 × g). In vivo, we applied a compressive force using the Waldo method in rats, and examined the distribution of ASPN or sclerostin by immunohistochemistry.ResultsIn vitro, hPDL cells subjected to 90 × g for 24 h demonstrated upregulated ASPN and downregulated SOST expressions, which were confirmed by immunofluorescent staining. In addition, the formation of mineralized tissue by human osteoblasts was significantly inhibited by the addition of medium from hPDL cells cultured during compressive force as well as the addition of equivalent amounts of ASPN peptide. In vivo, asporin-positive immunoreactive PDL cells and osteoclasts were found on the compressed side, whereas few sclerostin-positive PDL cells were observed.ConclusionsPDL cells subjected to an optimal compressive force induce the expression and release of ASPN, which inhibits bone formation during orthodontic tooth movement on the compressed side.     

Apical tooth germ cell-conditioned medium enhances the differentiation of periodontal ligament stem cells into cementum/periodontal ligament-like tissues

Background and Objective: Limitations of current periodontal regeneration modalities in both predictability and extent of healing response, especially on new cementum and attachment formation, underscore the importance of restoring or providing a microenvironment that is capable of promoting the differentiatiation of periodontal ligament stem cells (PDLSCs) towards cementoblast‐like cells and the formation of cementum/periodontal ligament‐like tissues. The aim of this study was to investigate the biological effect of conditioned medium from developing apical tooth germ cells (APTG‐CM) on the differentiation and cementogenesis of PDLSCs both in vitro and in vivo. Material and Methods: Using the limiting dilution technique, single‐colony‐derived human PDLSCs were isolated and expanded to obtain homogeneous populations of PDLSCs. Morphological appearance, cell cycle analysis, bromodeoxyuridine incorporation, alkaline phosphatase (ALP) activity, mineralization behavior, gene expression of cementoblast phenotype and in vivo differentiation capacities of PDLSCs co‐cultured with APTG‐CM were evaluated. Results: The induced PDLSCs exhibited several characteristics of cementoblast lineages, as indicated by the morphological changes, increased proliferation, high ALP activity, and the expression of cementum‐related genes and calcified nodule formation in vitro. When transplanted into immunocompromised mice, the induced PDLSCs showed tissue‐regenerative capacity to produce cementum/periodontal ligament‐like structures, characterized by a layer of cementum‐like mineralized tissues and associated periodontal ligament‐like collagen fibers connecting with the newly formed cementum‐like deposits, whereas control, untreated PDLSCs transplants mainly formed connective tissues. Conclusion: Our findings suggest that APTG‐CM is able to provide a cementogenic microenvironment and induce differentiation of PDLSCs along the cementoblastic lineage. This has important implications for periodontal engineering.     

The human periodontal ligament cell: a fibroblast-like cell acting as an immune cell

Jönsson D, Nebel D, Bratthall G, Nilsson B‐O. The human periodontal ligament cell: a fibroblast‐like cell acting as an immune cell. J Periodont Res 2011; 46: 153–157. © 2010 John Wiley & Sons A/S Background: Periodontal ligament cells are fibroblast‐like cells characterized by collagen production but also possessing some osteoblastic features. In the light of numerous studies presented during recent times, which show that human periodontal ligament cells also produce cytokines and chemokines in response to inflammation promoters, it is reasonable to suggest that periodontal ligament cells play a role as promoters of periodontal inflammation through these mechanisms. Material and Methods: The periodontal ligament, which harbours the periodontal ligament cells, is a part of the attachment apparatus comprised of periodontal ligament cells, extracellular matrix and fibres, attaching the root cement to the alveolar bone. Periodontal ligament cells are in close proximity to bacteria within the plaque and the pocket, and thus these cells are readily accessible to bacterial endotoxins and other promoters of inflammation. Results: Cytokines and chemokines, released by periodontal ligament cells upon stimulation with inflammation promoters, reach the blood vessels easily thanks to rich vascularization of the periodontium stimulating recruitment of white blood cells to the site of inflammation. In addition to classical inflammatory cells, such as leucocytes, macrophages and mast cells, the periodontal ligament cells also contribute to periodontal inflammation via their production and release of cytokines and chemokines. Conclusion: Therefore, pharmacological treatment of periodontitis should aim to reduce the release of proinflammatory agents not only from classical inflammatory cells but also from periodontal ligament cells.     

Immunolocalization of a human cementoblastoma-conditioned medium-derived protein

Little is known about the molecular mechanisms that regulate the cementogenesis process, because specific cementum markers are not yet available. To investigate whether a cementoblastoma-conditioned medium-derived protein (CP) could be useful as a cementum biological marker, we studied its expression and distribution in human periodontal tissues, human periodontal ligament, alveolar bone, and cementoblastoma-derived cells. In human periodontal tissues, immunoreactivity to anti-CP was observed throughout the cementoid phase of acellular and cellular cementum, cementoblasts, cementocytes, cells located in the endosteal spaces of human alveolar bone, and in cells in the periodontal ligament located near the blood vessels. Immunopurified CP promoted cell attachment on human periodontal ligament, alveolar bone-derived cells, and gingival fibroblasts. A monoclonal antibody against bovine cementum attachment protein (CAP) cross-reacted with CP. These findings indicate that CP identifies potential cementoblast progenitor cells, is immunologically related to CAP species, and serves as a biological marker for cementum.     

Non‐surgical model for alveolar bone regeneration by bone morphogenetic protein‐2/7 gene therapy

1 Background

Alveolar bone is a critical tissue for tooth retention; however, once alveolar bone is lost, it may not spontaneously regenerate. Currently, bone grafts or artificial bone is commonly used for alveolar bone regeneration therapy. However, these therapies require surgical procedures, which present risks, particularly in elderly patients. Therefore, development of alveolar bone regeneration techniques that do not require surgical procedures is critical. It is well known that stem cells present in the periosteal and periodontal ligament may be induced to differentiate into osteogenic cells. This study hypothesizes that transfer of the bone morphogenetic protein‐2/7 (BMP‐2/7) gene into periodontal tissues via in vivo electroporation induces exogenous BMP production and causes stem cells in periodontal tissues to differentiate into osteogenic cells, enabling generation of new alveolar bone.

2 Method

The BMP‐2/7 gene expression vector was introduced via electroporation into the target site in periodontal tissues of the first molar of rat maxillae.

3 Results

Exogenous BMP‐2 and ‐7 were detected in the target areas, and growth of new alveolar bone tissue was observed 5 days after gene transfer. On day 7, new alveolar bone tissues were found to connect to the original bone tissues. Moreover, mineral apposition rates of the alveolar bone after BMP‐2/7 gene transfer were significantly higher than those in the control group after LacZ gene transfer.

4 Conclusion

The present findings indicate that a combination of the BMP‐2/7 non‐viral vector and in vivo electroporation represents a promising non‐surgical option for alveolar bone regeneration therapy.     

Regenerative potential and healing dynamics of the periodontium: a critical‐size supra‐alveolar periodontal defect study

Objectives: The nature and characteristics of the newly formed periodontium obtained following regenerative procedures remain a matter of controversy. The objective of this study was to evaluate the regenerative potential of the periodontal attachment and healing dynamics as observed from the spatial distribution of newly formed cementum, periodontal ligament (PDL) and alveolar bone following optimal circumstances for wound healing/regeneration in a discriminating animal model. Material and Methods: Critical‐size, 6‐mm, supra‐alveolar, periodontal defects were surgically created in six young adult Beagle dogs. Space‐providing ePTFE devices with 300‐μm laser‐drilled pores were implanted to support wound stability and space provision in one jaw quadrant/animal. Treatments were alternated between left and right jaw quadrants in subsequent animals. The gingival flaps were advanced to submerge the defect sites for primary intention healing. Histometric analysis followed an 8‐week healing interval. Results: Healing was uneventful in all animals. The histometric analysis showed that cementum regeneration (2.99 ± 0.22 mm) was significantly greater than PDL (2.54 ± 0.18 mm, p=0.03) and bone regeneration (2.46 ± 0.26 mm, p=0.03). The wound area showed significant positive non‐linear effect on cementum (log β=1.25, p<0.001), PDL (log β=1.24, p<0.001) and new bone formation (log β=1.36, p<0.001). A high degree of concordance and significant linear relationship was observed between cementum, PDL and bone regeneration indicating that their formation virtually occurred in parallel. Conclusions: Cementum, PDL and alveolar bone virtually regenerate in parallel under optimal circumstances for periodontal wound healing/regeneration. Moreover, space provision positively influences the extent of periodontal regeneration.     

Periodontal regeneration via chemoattractive constructs

Aim

Chemoattractants, such as stromal cell‐derived factor‐1α (SDF‐1α), can offer an advantage for periodontal regeneration by recruiting the patient’s own stem cells to stimulate self‐repair. We here developed a chemoattractive construct for periodontal regeneration using SDF‐1α and evaluated its efficacy in vivo.

Materials and Methods

SDF‐1α was loaded on gelatin sponge and tested in vitro for SDF‐1α release. Subsequently, SDF‐1α constructs were implanted into rat periodontal defects for 1 and 6 weeks, with unloaded materials and empty defects as controls. The regenerative efficacy was evaluated by micro‐CT, histological and histomorphometrical analyses.

Results

In vitro results showed limited SDF‐1α release up to 35 days. In contrast, SDF‐1α constructs significantly improved periodontal defect regeneration in terms of alveolar bone height, new bone area and functional ligament length. Additionally, SDF‐1α constructs decreased the inflammatory response at Week 6.

Conclusion

Chemoattractive constructs significantly improved periodontal regeneration in terms of alveolar bone height, new bone area and functional ligament length.