Regeneration of Class III furcation defects with basic fibroblast growth factor (b-FGF) associated with GTR. A descriptive and histometric study in dogs

Cross-linked hyaluronic acid gel with or without a collagen matrix in the treatment of class III furcation defects: A histologic and histomorphometric study in dogs

AIM

To histologically evaluate the effects of cross-linked hyaluronic acid (xHyA) with or without a collagen matrix (CM) on periodontal wound healing/regeneration in class III furcation defects in dogs.

MATERIALS AND METHODS

Class III furcation defects were surgically created in the mandibular premolars in six beagle dogs. The defects were randomly treated as follows: open flap debridement (OFD) + CM (CM), OFD + xHyA (xHyA), OFD + xHyA + CM (xHyA/CM) and OFD alone (OFD). At 10 weeks, the animals were euthanized for histological evaluation.

RESULTS

The newly formed bone areas in the xHyA (4.04 ± 1.51 mm² ) and xHyA/CM (4.32 ± 1.14 mm² ) groups were larger than those in the OFD (3.25 ± 0.81 mm² ) and CM (3.31 ± 2.26 mm² ) groups. The xHyA (6.25 ± 1.45 mm) and xHyA/CM (6.40 ± 1.35 mm) groups yielded statistically significantly (p < .05) greater formation of new connective tissue attachment (i.e., new cementum, with inserting connective tissue fibres) compared with the OFD (1.47 ± 0.85 mm) group. No significant differences were observed in any of the histomorphometric parameters between the xHyA and xHyA/CM groups. Complete furcation closure was not observed in any of the four treatment modalities.

CONCLUSIONS

Within their limits, the present results suggest that the use of xHyA with or without CM positively influences periodontal wound healing in surgically created, acute-type class III furcation defects.

Development and regeneration of periodontal supporting tissues

Periodontal tissues, including gingiva, cementum, periodontal ligament, and alveolar bone, play important roles in oral health. Under physiological conditions, periodontal tissues surround and support the teeth, maintaining the stability of the teeth and distributing the chewing forces. However, under pathological conditions, with the actions of various pathogenic factors, the periodontal tissues gradually undergo some irreversible changes, that is, gingival recession, periodontal ligament rupture, periodontal pocket formation, alveolar bone resorption, eventually leading to the loosening and even loss of the teeth. Currently, the regenerations of the periodontal tissues are still challenging. Therefore, it is necessary to study the development of the periodontal tissues, the principles and processes of which can be used to develop new strategies for the regeneration of periodontal tissues. This review summarizes the development of periodontal tissues and current strategies for periodontal healing and regeneration.

One-step treatment of periodontitis based on a core-shell micelle-in-nanofiber membrane with time-programmed drug release

As a chronic inflammatory disease, periodontitis is responsible for irreversible soft tissue damage and severe alveolar bone resorption. However, curative effects of current therapies are largely confined by the difficulty to simultaneously achieve anti-inflammation and bone regeneration. Also, the dynamic environment in oral cavity easily causes the drugs swallowed or rinsed away by saliva. We report here a one-step treatment based on a core-shell nanofiber membrane fabricated by coaxial electrospinning. Polymeric micelles containing SP600125 were distributed in the shell, while BMP-2 was incorporated in the core. After crosslinking, the nanofiber membrane displayed a prolonged degradation and release period up to 4 weeks. The release of SP600125 was detected at beginning, whereas BMP-2 was not released until day 12. Such a time-programmed release behavior was proved desirable for suppressing the expression of pro-inflammatory factors and enhancing the osteogenic induction in vitro. Further in vivo investigation confirmed that, by simply covering the periodontitis site with our nanofiber membrane, alveolar destruction was largely avoided and bone defects recovered within 2 month. Taken together, we believe that the use of our membrane with sequential release of SP600125 and BMP-2 may become a convenient and highly comprehensive therapy for periodontitis.

Experimental and clinical studies on regenerative periodontal therapy

The recognition of a periodontal therapy as a regenerative procedure requires the demonstration of new cementum, periodontal ligament, and bone coronal to the base of the defect. A diversity of regenerative strategies has been evaluated, including root surface conditioning, bone grafts and bone substitute materials, guided tissue regeneration, enamel matrix proteins, growth/differentiation factors, combined therapies and, more recently, tissue-engineering approaches. The aim of this chapter of Periodontology 2000 is to review the research carried out in Latin America in the field of periodontal regeneration, focusing mainly on studies using preclinical models (animal models) and randomized controlled clinical trials. This review may help clinicians and researchers to evaluate the current status of the therapies available and to discuss the challenges that must be faced in order to achieve predictable periodontal regeneration in clinical practice.

Topical application of bFGF on acid-conditioned and non-conditioned dentin: effect on cell proliferation and gene expression in cells relevant for periodontal regeneration

Periodontal regeneration is still a challenge in terms of predictability and magnitude of effect. In this study we assess the biological effects of combining chemical root conditioning and biological mediators on three relevant cell types for periodontal regeneration.

Action Mechanism of Fibroblast Growth Factor-2 (FGF-2) in the Promotion of Periodontal Regeneration in Beagle Dogs

Fibroblast growth factor-2 (FGF-2) enhances the formation of new alveolar bone, cementum, and periodontal ligament (PDL) in periodontal defect models. However, the mechanism through which FGF-2 acts in periodontal regeneration in vivo has not been fully clarified yet. To reveal the action mechanism, the formation of regenerated tissue and gene expression at the early phase were analyzed in a beagle dog 3-wall periodontal defect model. FGF-2 (0.3%) or the vehicle (hydroxypropyl cellulose) only were topically applied to the defect in FGF-2 and control groups, respectively. Then, the amount of regenerated tissues and the number of proliferating cells at 3, 7, 14, and 28 days and the number of blood vessels at 7 days were quantitated histologically. Additionally, the expression of osteogenic genes in the regenerated tissue was evaluated by real-time PCR at 7 and 14 days. Compared with the control, cell proliferation around the existing bone and PDL, connective tissue formation on the root surface, and new bone formation in the defect at 7 days were significantly promoted by FGF-2. Additionally, the number of blood vessels at 7 days was increased by FGF-2 treatment. At 28 days, new cementum and PDL were extended by FGF-2. Moreover, FGF-2 increased the expression of bone morphogenetic protein 2 (BMP-2) and osteoblast differentiation markers (osterix, alkaline phosphatase, and osteocalcin) in the regenerated tissue. We revealed the facilitatory mechanisms of FGF-2 in periodontal regeneration in vivo. First, the proliferation of fibroblastic cells derived from bone marrow and PDL was accelerated and enhanced by FGF-2. Second, angiogenesis was enhanced by FGF-2 treatment. Finally, osteoblastic differentiation and bone formation, at least in part due to BMP-2 production, were rapidly induced by FGF-2. Therefore, these multifaceted effects of FGF-2 promote new tissue formation at the early regeneration phase, leading to enhanced formation of new bone, cementum, and PDL.

Tissue engineering for bone regeneration and osseointegration in the oral cavity

OBJECTIVE

The focus of this review is to summarize recent advances on regenerative technologies (scaffolding matrices, cell/gene therapy and biologic drug delivery) to promote reconstruction of tooth and dental implant-associated bone defects.

METHODS

An overview of scaffolds developed for application in bone regeneration is presented with an emphasis on identifying the primary criteria required for optimized scaffold design for the purpose of regenerating physiologically functional osseous tissues. Growth factors and other biologics with clinical potential for osteogenesis are examined, with a comprehensive assessment of pre-clinical and clinical studies. Potential novel improvements to current matrix-based delivery platforms for increased control of growth factor spatiotemporal release kinetics are highlighting including recent advancements in stem cell and gene therapy.

RESULTS

An analysis of existing scaffold materials, their strategic design for tissue regeneration, and use of growth factors for improved bone formation in oral regenerative therapies results in the identification of current limitations and required improvements to continue moving the field of bone tissue engineering forward into the clinical arena.

SIGNIFICANCE

Development of optimized scaffolding matrices for the predictable regeneration of structurally and physiologically functional osseous tissues is still an elusive goal. The introduction of growth factor biologics and cells has the potential to improve the biomimetic properties and regenerative potential of scaffold-based delivery platforms for next-generation patient-specific treatments with greater clinical outcome predictability.

Bone repair cells for craniofacial regeneration

Reconstruction of complex craniofacial deformities is a clinical challenge in situations of injury, congenital defects or disease. The use of cell-based therapies represents one of the most advanced methods for enhancing the regenerative response for craniofacial wound healing. Both somatic and stem cells have been adopted in the treatment of complex osseous defects and advances have been made in finding the most adequate scaffold for the delivery of cell therapies in human regenerative medicine. As an example of such approaches for clinical application for craniofacial regeneration, Ixmyelocel-T or bone repair cells are a source of bone marrow derived stem and progenitor cells. They are produced through the use of single pass perfusion bioreactors for CD90+ mesenchymal stem cells and CD14+ monocyte/macrophage progenitor cells. The application of ixmyelocel-T has shown potential in the regeneration of muscular, vascular, nervous and osseous tissue. The purpose of this manuscript is to highlight cell therapies used to repair bony and soft tissue defects in the oral and craniofacial complex. The field at this point remains at an early stage, however this review will provide insights into the progress being made using cell therapies for eventual development into clinical practice.

Cell- and gene-based therapeutic strategies for periodontal regenerative medicine

Inflammatory periodontal diseases are a leading cause of tooth loss and are linked to multiple systemic conditions, such as cardiovascular disease and stroke. Reconstruction of the support and function of affected tooth-supporting tissues represents an important therapeutic endpoint for periodontal regenerative medicine. An improved understanding of periodontal biology coupled with current advances in scaffolding matrices has introduced novel treatments that use cell and gene therapy to enhance periodontal tissue reconstruction and its biomechanical integration. Cell and gene delivery technologies have the potential to overcome limitations associated with existing periodontal therapies, and may provide a new direction in sustainable inflammation control and more predictable tissue regeneration of supporting alveolar bone, periodontal ligament, and cementum. This review provides clinicians with the current status of these early-stage and emerging cell- and gene-based therapeutics in periodontal regenerative medicine, and introduces their future application in clinical periodontal treatment. The paper concludes with prospects on the application of cell and gene tissue engineering technologies for reconstructive periodontology.

Periodontal tissue engineering and regeneration: current approaches and expanding opportunities

The management of periodontal tissue defects that result from periodontitis represents a medical and socioeconomic challenge. Concerted efforts have been and still are being made to accelerate and augment periodontal tissue and bone regeneration, including a range of regenerative surgical procedures, the development of a variety of grafting materials, and the use of recombinant growth factors. More recently, tissue-engineering strategies, including new cell- and/or matrix-based dimensions, are also being developed, analyzed, and employed for periodontal regenerative therapies. Tissue engineering in periodontology applies the principles of engineering and life sciences toward the development of biological techniques that can restore lost alveolar bone, periodontal ligament, and root cementum. It is based on an understanding of the role of periodontal formation and aims to grow new functional tissues rather than to build new replacements of periodontium. Although tissue engineering has merged to create more opportunities for predictable and optimal periodontal tissue regeneration, the technique and design for preclinical and clinical studies remain in their early stages. To date, the reconstruction of small- to moderate-sized periodontal bone defects using engineered cell-scaffold constructs is technically feasible, and some of the currently developed concepts may represent alternatives for certain ideal clinical scenarios. However, the predictable reconstruction of the normal structure and functionality of a tooth-supporting apparatus remains challenging. This review summarizes current regenerative procedures for periodontal healing and regeneration and explores their progress and difficulties in clinical practice, with particular emphasis placed upon current challenges and future possibilities associated with tissue-engineering strategies in periodontal regenerative medicine.

Periodontal regeneration: focus on growth and differentiation factors

Several growth and differentiation factors have shown potential as therapeutic agents to support periodontal wound healing/regeneration, although optimal dosage, release kinetics, and suitable delivery systems are still unknown. Experimental variables, including delivery systems, dose, and the common use of poorly characterized preclinical models, make it difficult to discern the genuine efficacy of each of these factors. Only a few growth and differentiation factors have reached clinical evaluation. It appears that well-defined discriminating preclinical models followed by well-designed clinical trials are needed to further investigate the true potential of these and other candidate factors. Thus, current research is focused on finding relevant growth and differentiation factors, optimal dosages, and the best approaches for delivery to develop clinically meaningful therapies in patient-centered settings.

Localized delivery of growth factors for periodontal tissue regeneration: role, strategies, and perspectives

Difficulties associated with achieving predictable periodontal regeneration, means that novel techniques need to be developed in order to regenerate the extensive soft and hard tissue destruction that results from periodontitis. Localized delivery of growth factors to the periodontium is an emerging and versatile therapeutic approach, with the potential to become a powerful tool in future regenerative periodontal therapy. Optimized delivery regimes and well-defined release kinetics appear to be logical prerequisites for safe and efficacious clinical application of growth factors and to avoid unwanted side effects and toxicity. While adequate concentrations of growth factor(s) need to be appropriately localized, delivery vehicles are also expected to possess properties such as protein protection, precision in controlled release, biocompatibility and biodegradability, self-regulated therapeutic activity, potential for multiple delivery, and good cell/tissue penetration. Here, current knowledge, recent advances, and future possibilities of growth factor delivery strategies are outlined for periodontal regeneration. First, the role of those growth factors that have been implicated in the periodontal healing/regeneration process, general requirements for their delivery, and the different material types available are described. A detailed discussion follows of current strategies for the selection of devices for localized growth factor delivery, with particular emphasis placed upon their advantages and disadvantages and future prospects for ongoing studies in reconstructing the tooth supporting apparatus.

Regulation of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases by basic fibroblast growth factor and dexamethasone in periodontal ligament cells

BACKGROUND AND OBJECTIVES

In this study, we investigated the effect of basic fibroblast growth factor (bFGF) and dexamethasone (Dex) on mRNA expressions of collagen (COL) type I, III and X, matrix metalloproteinases (MMP)-1, -2, -3 and -9 and tissue inhibitors of metalloproteinases (TIMP)-1 and -2, and also on mineralization and morphology of periodontal ligament (PDL) cells.

MATERIAL AND METHODS

Periodontal ligament cells were obtained from premolar teeth extracted for orthodontic reasons. Periodontal ligament cells were cultured with Dulbecco's modified Eagle's medium containing: (1) 5% fetal bovine serum (FBS); (2) 5% FBS + ascorbic acid (AA, 50 microg/mL); (3) 5% FBS + Dex (10(-7) m) + AA; (4) 5% FBS + bFGF (10 ng/mL) + AA; or (5) 5% FBS + Dex (10(-7) m) + bFGF + AA. Cells within each group were evaluated for gene expression profile using semi-quantitative reverse transcriptase-polymerase chain reaction for COL I, III and X, MMP-1, -2, -3 and -9 and TIMP-1 and -2 on days 14 and 21 and for biomineralization by von Kossa stain in vitro on day 21. Images of PDL cells were examined using a phase contrast microscope.

RESULTS

Basic fibroblast growth factor stimulated MMP-1, MMP-3 and MMP-9 mRNA expressions and inhibited TIMP-2 mRNA expression. Treatment of cells with Dex + bFGF led to downregulation of MMP-1, MMP-3 and MMP-9 transcripts. Whilst AA alone and Dex alone induced biomineralization of PDL cells, bFGF blocked the mineralization activity of the cells. In the Dex + bFGF group, more mineral nodules were noted when compared to AA alone and Dex alone groups.

CONCLUSION

The addition of Dex to culture reversed bFGF-mediated inhibition of mineralization. Use of combined bFGF and Dex to regulate PDL cell function may be a good therapeutic option to obtain periodontal regeneration.

Effects of basic fibroblast growth factor on density and morphology of fibroblasts grown on root surfaces with or without conditioning with tetracycline or EDTA

A study was conducted to evaluate in vitro the effect of root surface conditioning with basic fibroblast growth factor (b-FGF) on morphology and proliferation of fibroblasts. Three experimental groups were used: non-treated, and treated with 50 microg or 125 microg b-FGF/ml. The dentin samples in each group were divided into subgroups according to the chemical treatment received before application of b-FGF: none, or conditioned with tetracycline-HCl or EDTA. After contact with b-FGF for 5 min, the samples were incubated for 24 h with 1 ml of culture medium containing 1 x 10(5) cells/ml plus 1 ml of culture medium alone. The samples were then subjected to routine preparation for SEM, and random fields were photographed. Three calibrated and blind examiners performed the assessment of morphology and density according to two index systems. Classification and regression trees indicated that the root surfaces treated with 125 microg b-FGF and previously conditioned with tetracycline-HCl or EDTA presented a morphology more suggestive of cellular adhesion and viability (P = 0.004). The density of fibroblasts on samples previously conditioned with EDTA, regardless of treatment with b-FGF, was significantly higher than in the other groups (P < 0.001). The present findings suggest that topical application of b-FGF has a positive influence on both the density and morphology of fibroblasts.

Opposite effects of bFGF and TGF-β on collagen metabolism by human periodontal ligament fibroblasts

This study evaluated the effects of bFGF and TGF-beta, individually and combined, on cell proliferation and collagen metabolism. Primary human periodontal ligament cells were stimulated with two concentrations (1 and 10 ng/ml) of each growth factor, both individually and combined. Proliferation was determined by a commercial biochemical assay. Real time RT-PCR determined gene expression of MMP-1 and -2, collagen types I and III, TIMP-1, -2 and -3. Autocrine effects on synthesis of bFGF and TGF-beta were evaluated by ELISA. Only TGF-beta, either isolated or associated with bFGF, significantly increased cell proliferation. TGF-beta had anabolic effects, increasing expression of type I and III collagen as well as of TIMPs, whereas bFGF had opposite effects. When bFGF and TGF-beta were associated, the anabolic effects prevailed. Synthesis of TGF-beta was induced only by the association of lower concentrations of the growth factors, whereas there was a dose-dependent production of bFGF. It is concluded that bFGF had a predominantly catabolic effect, and TGF-beta exerted an anabolic effect on hPDL cells.

Levels of gingival tissue platelet activating factor after conventional and regenerative periodontal surgery

The hypothesis, a relationship between gingival tissue platelet activating factor (PAF) levels and healing after periodontal surgery, was tested by measuring PAF levels in gingival tissues collected from sites that had undergone flap surgery and guided tissue regeneration (GTR) or flap surgery alone. Using a split-mouth design, 20 intrabony defects were randomly assigned to treatment with flap surgery and GTR (group 1) or with flap surgery alone (group 2). Gingival tissue samples were obtained at surgery (baseline) and at 6-month follow-up evaluation visit. One half of each sample was used for analysis of PAF levels by high-performance liquid chromatography, and the other half of the sample was used for histomorphometric analysis that included measurements of number and diameter of blood vessels. PAF levels and diameter of blood vessels were significantly decreased (p < 0.01), and the number of blood vessels was significantly increased (p < 0.05) in both groups after 6 months compared to the baseline values. Postoperative number of blood vessels were significantly higher in group 1 (p < 0.05), whereas there was no significant difference in postoperative PAF levels between the two groups (p > 0.05). Based on the reported results, it is suggested that a decrease in gingival PAF levels might be found after conventional and regenerative periodontal surgery.

Craniofacial tissue engineering by stem cells

Craniofacial tissue engineering promises the regeneration or de novo formation of dental, oral, and craniofacial structures lost to congenital anomalies, trauma, and diseases. Virtually all craniofacial structures are derivatives of mesenchymal cells. Mesenchymal stem cells are the offspring of mesenchymal cells following asymmetrical division, and reside in various craniofacial structures in the adult. Cells with characteristics of adult stem cells have been isolated from the dental pulp, the deciduous tooth, and the periodontium. Several craniofacial structures--such as the mandibular condyle, calvarial bone, cranial suture, and subcutaneous adipose tissue--have been engineered from mesenchymal stem cells, growth factor, and/or gene therapy approaches. As a departure from the reliance of current clinical practice on durable materials such as amalgam, composites, and metallic alloys, biological therapies utilize mesenchymal stem cells, delivered or internally recruited, to generate craniofacial structures in temporary scaffolding biomaterials. Craniofacial tissue engineering is likely to be realized in the foreseeable future, and represents an opportunity that dentistry cannot afford to miss.

Role of growth factors on periodontal repair

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis and differentiation of cells from epithelium, bone and connective tissue. They express their action by binding to specific cell-surface receptors present on various target cells including osteoblasts, cementoblasts and periodontal ligament fibroblasts. The observation that growth factors participate in all cell functions led to exogenous application during periodontal tissue repair aiming to their use as an alternative therapeutic approach to periodontal therapy. Cell types and cultures conditions, dose, carrier materials, application requirements are of critical importance in the outcome of periodontal repair. The purpose of this article is to review the literature with respect to the biological actions of PDGF, TGF, FGF, IGF and EGF on periodontal cells and tissues, which are involved in periodontal regeneration.

Growth factor delivery for oral and periodontal tissue engineering

The treatment of oral and periodontal diseases and associated anomalies accounts for a significant proportion of the healthcare burden, with the manifestations of these conditions being functionally and psychologically debilitating. Growth factors are critical to the development, maturation, maintenance and repair of craniofacial tissues, as they establish an extracellular environment that is conducive to cell and tissue growth. Tissue-engineering principles aim to exploit these properties in the development of biomimetic materials that can provide an appropriate microenvironment for tissue development. These materials have been constructed into devices that can be used as vehicles for delivery of cells, growth factors and DNA. In this review, different mechanisms of drug delivery are addressed in the context of novel approaches to reconstruct and engineer oral- and tooth-supporting structures, namely the periodontium and alveolar bone.

Treatment of Class III Furcation Defects With Expanded Polytetrafluoroethylene Membrane Associated or Not With Anorganic Bone Matrix/Synthetic Cell-Binding Peptide: A Histologic and Histomorphometric Study in Dogs

BACKGROUND

Up until now, no predictable periodontal regeneration of Class III furcation defects has been demonstrated after treatment with different available techniques. Recently, a bone graft enriched with a peptide was developed and has shown satisfactory results when applied in intrabony defects. The aim of this study was to compare the use of expanded polytetrafluoroethylene (ePTFE) membrane associated (test group) or not (control group) with anorganic bovine-derived bone matrix (ABM)/synthetic peptide, in the treatment of Class III furcation defects in dogs.

METHODS

Six mongrel dogs were used in this study, and the second and fourth mandibular lower premolars were extracted. Class III furcation defects were surgically created in the third premolars and filled with impression material. Afterwards, the defects were surgically assessed for debridement and root planing. Teeth were randomly assigned into test and control groups. The membranes were removed after 4 weeks, and the animals were sacrificed 12 weeks later.

RESULTS

Comparisons between groups by the Wilcoxon signed rank test showed no statistically significant differences in the parameters evaluated. In the control group, a new bone area (NBA) of 41.71%+/-24.07%, connective tissue area (CTA) of 36.34%+/-15.50%, and epithelium tissue area (ETA) of 9.39%+/-5.85% were observed. The new cementum extension (NCE) was 24.16%+/-13.18%. The test group presented an NBA of 31.84%+/-12.58%, CTA of 47.72%+/-11.33%, ETA of 9.17%+/-6.81%, and an NCE of 30.13%+/-16.43%.

CONCLUSION

There was no statistically significant difference between the two therapies: ePTFE membrane associated with ABM/synthetic peptide flow or ePTFE membrane only.

Enamel matrix proteins associated with GTR and bioactive glass in the treatment of class III furcation in dogs

This study investigated, both histologically and histometrically, the efficacy of enamel matrix derived proteins (EMD) associated with bioactive glass (BG) and an absorbable membrane in the treatment of class III furcation defects in mongrel dogs. After surgical defect creation and chronification, the lesions were randomly divided into three groups according to the treatment employed: Test Group 1 - EMD + BG + membrane, Test Group 2 - EMD + membrane and Control Group - BG + membrane. After a 90-day healing period, the dogs were sacrificed. The descriptive analysis and the histometric data showed similar results for the experimental groups in all studied parameters (MANOVA, p > 0.05). The association of Emdogain® with bioglass and GTR, or with GTR only, showed similar results when compared with the ones obtained with bioglass associated with membrane in the treatment of class III furcation defects in dogs. The three modalities of treatment showed partial filling of the furcations, with bone and cementum regeneration limited to the apical portion of the defects.

Growth and Amelogenin-Like Factors in Periodontal Wound Healing. A Systematic Review

BACKGROUND

Regeneration of tooth-supporting structures destroyed by periodontitis is a major goal of periodontal therapy. Periodontal tissue engineering utilizing growth and amelogenin-like factors (GAFs) applies advances in materials science and biology to regenerate alveolar bone, periodontal ligament, and cementum. Amelogenin-like factors (e.g., enamel matrix derivative [EMD]) and growth factors (e.g., platelet-derived growth factor [PDGF] and bone morphogenetic proteins [BMPs, also considered morphogens]) have demonstrated pleotrophic effects on the stimulation of several key events required for tissue regeneration including DNA synthesis, chemotaxis, differentiation, and matrix synthesis.

RATIONALE

GAFs have been used for the treatment of periodontal disease as shown in preclinical and clinical studies. This systematic review evaluates the evidence to support the utilization of EMD and growth factors (GFs) for periodontal repair and regeneration associated with natural teeth.

FOCUSED QUESTION

In patients with periodontal osseous defects, what is the effect of GAFs compared with controls on clinical, radiographic, histologic, adverse, and patient-centered outcomes?

SEARCH PROTOCOL

Two investigators searched MEDLINE, pre-MEDLINE, and the Cochrane Oral Health Group trials register for clinical and preclinical studies published in English. Hand searches were performed on the International Journal of Periodontics and Restorative Dentistry, Journal of Clinical Periodontology, Journal of Dental Research, Journal of Periodontology, and Journal of Periodontal Research. Searches were performed for articles published through April 2002. In addition, investigators contacted manufacturers of GAF products for related unpublished data and studies in progress.

SELECTION CRITERIA

INCLUSION CRITERIA

Randomized controlled clinical trials (RCTs), cohort studies, case-control studies, case reports, and preclinical (animal) randomized controlled investigations that included a cohort population diagnosed with periodontal disease and presenting data on intrabony/interproximal defects and/or furcation defects were screened.

EXCLUSION CRITERIA

In vitro studies or those that did not include quantifiable data with respect to clinical or bone measures were not included.

DATA COLLECTION AND ANALYSIS

Meta-analyses were performed for studies that fulfilled the eligibility criteria for the following continuous variables: clinical attachment level (CAL), probing depth (PD), or bone level (radiographic, re-entry, or histologic). Heterogeneity was assessed to determine whether the differences among therapies were due to systematic confounding factors (as noted in study quality assessments).

MAIN RESULTS

1. Eight studies, representing 7 RCTs and 1 quasi-experimental study, representing a total population of 511 subjects were analyzed with respect to EMD. 2. The majority of the remaining papers had a low evidence rating. 3. Most reports were case studies or case series without controls. 4. There were insufficient data to conduct a meta-analysis on the effect of growth factors used in periodontal repair around teeth.

REVIEWERS' CONCLUSIONS

1. There is evidence supporting the use of EMD for periodontal osseous defects to improve CAL and reduce PD, although long-term benefits have not been established. 2. EMD has demonstrated notable consistency among the studies investigated in terms of superiority to controls (in general compared to open flap debridement [OFD]). 3. EMD appears to be safe for single and multiple administrations in terms of lack of elicitation of antibody responses or other local/systemic inflammatory events. 4. Preclinical and initial clinical data for growth factors appear promising but are insufficient to draw definitive conclusions at this time.

Novel approach to regeneration of periodontal tissues based on in situ tissue engineering: effects of controlled release of basic fibroblast growth factor from a sandwich membrane

To regenerate periodontal tissues, a sandwich membrane composed of a collagen sponge scaffold and gelatin microspheres containing basic fibroblast growth factor (bFGF) in a controlled-release system was developed according to the new concept of "in situ tissue engineering." A three-walled alveolar bone defect (3 x 4 x 4 mm) was made bilaterally in edentulous regions created mesially to the canines in both the maxilla and mandible of nine beagle dogs. A sandwich membrane with or without bFGF (100 microg) was implanted in each defect (each group, n = 18). During weeks 1, 2, and 4, histologic evaluation and histometric analyses were performed on three dogs. Throughout the 4 weeks, vascularization and osteogenesis were active only in the bFGF-treated group (p < 0.01). New cementum was formed (2.4 +/- 0.9 mm) on the exposed root surface at 4 weeks, and functional recovery of the periodontal ligament was indicated in part by the perpendicular orientation of regenerated collagen fibers. In the control group, epithelial downgrowth and root resorption occurred and the defects were filled with connective tissue. Thus, our sandwich membrane induced successful regeneration of the periodontal tissues in a short period of time.

Regenerative repair of the mandible using a collagen sponge containing TGF-beta1

INTRODUCTION

Alveolar bone resorption and atrophy of the mandible are a major challenge for regeneration medicine. In the present investigation, a collagen sponge that contained TGF-beta1 was placed at a mandibular defect and the osteogenic effects of collagen-TGF-beta1, complex were evaluated.

MATERIAL AND METHODS

The Pm2, Pm3, and Pm4 teeth on both sides of the mandibles of 12 adult beagle dogs (9.0-12.0 kg) were extracted. After the extraction-site wounds healed, a bone defect (10.0 x 15.0 mm-wide, 10.0 mm-deep or 10.0 x 10.0 mm-wide, 10.0 mm-deep) was created on the mandible. A collagen sponge (10.0 x 10.0 x 10.0 mm) that contained TGF-beta1 (1.0 microg, 5.0 microg, or 10.0 microg, in physiological saline) was placed at the bottom of the defect and the overlying mucous membrane was sutured with 4-0 prolene. As a control, a collagen sponge that contained physiological saline only was placed in a defect on the opposite side. Two weeks after the surgery the wounds above the bone defects on both the control and TGF-beta1-treated sides had healed completely.

RESULTS

At four, six, or eight weeks post-operatively animals were killed. Soft X-ray and bone-salt measurement analyses confirmed clearly that there was greater calcified bone formation in the defects into which TGF-beta1 had been incorporated than with the control defects. The implanted collagen sponges were fully resorbed and the bone tissue had regenerated from the bottom of the defects on the TGF-beta1, side by four weeks. On the control side, no such regeneration was observed.

CONCLUSIONS

These results indicate that TGF-beta1, released slowly from a collagen sponge was effective in promoting bone remodeling when applied to mandibular defects in adult dogs.

Cytokine regulation of gingival fibroblast lysyl oxidase, collagen, and elastin

BACKGROUND

Systemic therapy with cyclosporin A, phenytoin, and nifedipine modulates cytokine levels in human gingival tissues. Functional relationships between altered cytokine levels and gingival extracellular matrix production are partially characterized. The present study investigates in cultured human gingival fibroblasts the regulation of lysyl oxidase, alpha-1 type I collagen, and elastin by selected cytokines that are elevated in drug-induced gingival overgrowth tissues.

METHODS

Normal human gingival fibroblasts were cultured and then treated with selected cytokines: interleukin (IL)-1beta, IL-6, platelet-derived growth factor (PDGF)-BB, and basic fibroblast growth factor (bFGF or FGF-2). Cells were harvested at intervals, and changes in lysyl oxidase enzyme activity, and in mRNA levels of lysyl oxidase, alpha-1 type I collagen, and elastin were determined.

RESULTS

bFGF reproducibly and significantly decreased human gingival fibroblast lysyl oxidase and alpha-1 type I collagen mRNA levels in a dose- and time-dependent manner; 1 nM bFGF reduced lysyl oxidase and collagen mRNA levels to 53% and to less than 10% of control after 48 hours of treatment. Interestingly, bFGF downregulated lysyl oxidase enzyme activity by 10% to 20%. IL-1, IL-6, and PDGF-BB did not significantly regulate lysyl oxidase enzyme activity, or alpha-1 type I collagen, elastin, and lysyl oxidase mRNA levels under the conditions tested.

CONCLUSIONS

Previous studies have shown that modulated levels of bFGF occur in gingiva as a result of certain pharmacologic therapies. The present study suggests that modulated levels of bFGF likely influence gingival connective tissue metabolism.