Growth and differentiation factors for periodontal regeneration: a review on factors with clinical testing

FGF and TGF-β growth factor isoform modulation of human gingival and periodontal ligament fibroblast wound healing phenotype

Release of growth factors in the tissue microenvironment is a critical process in the repair and regeneration of periodontal tissues, regulating fibroblast behavior and phenotype. As a result of the complex architecture of the periodontium, distinct fibroblast populations in the periodontal ligament and gingival connective tissue exist in close proximity. Growth factor therapies for periodontal regeneration have gained traction, but quantification of their effects on multiple different fibroblast populations that are required for repair has been poorly investigated. In this study, we examined the effects of TGF-β1, TGF-β3, FGF-2, and FGF-9 on human gingival fibroblasts (hGF) and human periodontal ligament cells (hPDL), as well as the combined effects of TGF-β3 and FGF-2. We show that FGF-2 enhances cell migration while TGF-β1 and TGF-β3 promotes matrix production, and TGF-β1 promotes fibroblast to myofibroblast transition. Interestingly, the combination of TGF-β3 and FGF-2, acting through both p-SMAD3 and p-ERK pathways, mitigates the inhibitory effects of TGF-β3 on migration in hPDL cells, suggesting synergistic and complimentary effects of FGF-2 and TGF-β3. Additionally, fibronectin production in hGF increased when treated with the combined TGF-β3+FGF-2 compared to FGF-2 alone, indicating that the effects of TGF-β3 in promoting extracellular matrix production are still active in the combined treatment condition. Finally, our study highlights that FGF-9 did not influence migration, α-SMA expression, or extracellular matrix production in either cell type, emphasizing the unique roles of specific growth factors in cellular responses. The synergistic effects observed with combined TGF-β3 and FGF-2 treatments present promising avenues for further research and clinical advancements in regenerative medicine.

The clinical effect of bone perforations in periodontal regeneration and alveolar socket preservation: a systematic review with meta-analysis

OBJECTIVES

The present systematic review aimed to evaluate if cortical bone perforation is effective in enhancing periodontal surgery and guided bone regeneration (GBR) in humans.

MATERIALS AND METHODS

Electronic search was performed in PubMed, Scopus and Cochrane CENTRAL up to October 31st, 2023. Grey literature was also searched. Prospective controlled studies were included. Two PICO questions were created; one focusing on the effect of bone perforation in the treatment of peridodontal intrabony defects (primary outcome probing depth (PD)) and one focusing on the effect of bone perforation in guided bone regeneration (primary outcome: histologic and histomorphometric data). The risk of bias of the included studies was assessed using the Cochrane tool for randomized controlled studies (RCTs) and the Joanna Briggs Institute Critical Appraisal tool for cohort studies. Pairwise meta-analysis was undertaken when possible, to estimate the overall effect for the outcomes investigated.

RESULTS

The search on databases yielded a total of 653 articles. After screening, five RCTs and one non-randomized study were included. A meta-analysis was performed for the first PICO. PD was evaluated in 4 articles and no significant difference was found between the perforation vs. no perforation groups (0.11 mm (95% CI [-0.14 to 0.37 mm], P = 0.38). Additionally, radiographic defect depth (mean difference 0.77 mm, 95% CI [0.24 to 1.30 mm], P = 0.004) and distance between cemento-enamel junction and bone defect (standardized mean difference 0.98 mm, 95% CI [0.47 to 1.50 mm], P = 0.0002) resulted improved in the cortical bone perforation group.

CONCLUSION

The evidence supporting a positive effect of using cortical perforations is very poor. Further studies with larger sample sizes are needed to determine whether decortication brings meaningful advantages.

CLINICAL RELEVANCE

This study is focused on clinical studies and, using a rigorous study selection and a meta-analytic approach suggests that the apparent positive effect of bone decortication on the regeneration process still requires to be confirmed by more solid evidence.

Simultaneous or staged lateral ridge augmentation: A clinical guideline on the decision-making process

Lateral ridge augmentation is a standard surgical procedure that can be performed prior to (staged) or simultaneously with implant placement. The decision between a simultaneous or staged approach involves considering multiple variables. This paper proposed a decision-making process that serves as a guideline for choosing the best treatment choice based on the available evidence and the author's clinical experience.

The role of rhFGF-2 in periodontal defect bone fill: A systematic review of the literature

BACKGROUND

Growth factors have been used with success in periodontal regeneration, especially in intrabony defects. Among those, the recombined form of fibroblast growth factor-2 (rhFGF-2) has been also examined.

OBJECTIVE

To address the outcomes of periodontal regeneration using rhFGF-2 alone or in combination with bone substitutes primarily in terms of Radiographic Bone Fill (RBF%) and secondary Probing Pocket Depth (PPD), and Probing Attachment Levels (PAL).

MATERIAL AND METHODS

A search in MEDLINE and EMBASE using the Ovid interface was conducted from 2000 up to and including the 12th of November 2022. Starting from the initially identified 1289 articles, 34 studies were selected for further analysis. Following the full-text screening, 7 of the 34 studies met the inclusion criteria and thus were included in the systematic review after assessing their quality according to the Newcastle-Ottawa scale (NOS). Clinical and radiographic results (bone gain, pocket depth, and clinical attachment level) after the application of FGF-2 alone or in combination with different carriers were studied in patients with intrabony defects of at least one wall and pocket depth greater than 4 mm.

RESULTS

Primary outcomes: RBF% was higher in studies using a combination of rhFGF-2 and bone substitutes (74.6 ± 20.0%) compared to others using the specific growth factor alone or negative controls (22.7 ± 20.7%). In terms of secondary outcomes, the analysis failed to show an additional benefit from the use of the rhFGF-2 alone or in combination with bone substitutes.

CONCLUSION

rhFGF-2 can improve RBF% in the treatment of periodontal defects, especially when it is used in combination with a bone substitute.

Guided Bone Regeneration in a Periodontally Compromised Individual with Autogenous Tooth Bone Graft: A Radiomics Analysis

BACKGROUND

Autogenous tooth bone graft material (AutoBT) has been advocated as a bone substitute when conducting alveolar ridge preservation. This study is aimed at using a radiomics approach in order to evaluate and testify whether AutoBT can stimulate bone growth during socket preservation in severe periodontal cases.

MATERIALS AND METHODS

For this study, 25 cases with severe periodontal diseases were selected. The patients' AutoBTs were inserted into the extraction sockets and covered with Bio-Gide^® collagen membranes. 3D CBCT scans and 2D X-rays were taken of the patients before surgery and after 6 months post-surgery. For the retrospective radiomics analysis, the maxillary and mandibular images were compared in different groups. Maxillary bone height was analyzed at the buccal, middle, and palatal crest sites, while the mandibular bone height was compared at the buccal, center, and lingual crest sites.

RESULTS

In the maxilla, the alveolar height was increased by -2.15 ± 2.90 mm at the buccal crest; -2.45 ± 2.36 mm at the center of the socket, and -1.62 ± 3.19 mm at the palatal crest, while the height of the buccal crest was increased by 0.19 ± 3.52 mm, and the height at the center of the socket was increased by -0.70 ± 2.71 mm in the mandible. The three-dimensional radiomics analysis demonstrated significant bone growth in the local alveolar height and high density.

CONCLUSION

Based on clinical radiomics analysis, AutoBT could be used as an alternative bone material in socket preservation after tooth extraction in patients with severe periodontitis.

Periodontal regeneration: Lessons from the periodontal ligament-cementum junction in diverse animal models

The attachment of the roots of mammalian teeth of limited eruption to the jawbone is reliant in part on the mineralization of collagen fibrils of the periodontal ligament (PDL) at their entry into bone and cementum as Sharpey's fibers. In periodontitis, a high prevalence infection of periodontal tissues, the attachment apparatus of PDL to the tooth root is progressively destroyed. Despite the pervasiveness of periodontitis and its attendant healthcare costs, and regardless of decades of research into various possible treatments, reliable restoration of periodontal attachment after surgery is not achievable. Notably, treatment outcomes in animal studies have often demonstrated more positive regenerative outcomes than in human clinical studies. Conceivably, defining how species diversity affects cementogenesis and cementum/PDL regeneration could be instructive for informing novel and more efficacious treatment strategies. Here we briefly review differences in cementum and PDL attachment in commonly used animal models to consider how species differences may lead to enhanced regenerative outcomes.

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.

Periodontal Wound Healing and Regeneration: Insights for Engineering New Therapeutic Approaches

Periodontitis is a widespread inflammatory disease that leads to loss of the tooth supporting periodontal tissues. The few therapies available to regenerate periodontal tissues have high costs and inherent limitations, inspiring the development of new approaches. Studies have shown that periodontal tissues have an inherent capacity for regeneration, driven by multipotent cells residing in the periodontal ligament (PDL). The purpose of this review is to describe the current understanding of the mechanisms driving periodontal wound healing and regeneration that can inform the development of new treatment approaches. The biologic basis underlying established therapies such as guided tissue regeneration (GTR) and growth factor delivery are reviewed, along with examples of biomaterials that have been engineered to improve the effectiveness of these approaches. Emerging therapies such as those targeting Wnt signaling, periodontal cell delivery or recruitment, and tissue engineered scaffolds are described in the context of periodontal wound healing, using key in vivo studies to illustrate the impact these approaches can have on the formation of new cementum, alveolar bone, and PDL. Finally, design principles for engineering new therapies are suggested which build on current knowledge of periodontal wound healing and regeneration.

Biological Basis of Periodontal Regeneration

The ultimate goal of periodontal therapy is homeostatic regeneration of lost attachment of alveolar bone and gingival connective tissue to the exposed root surfaces with a fully functional and healthy periodontal ligament that is covered with a healthy epithelium. This goal needs a complete understanding of the biological mechanisms inherent to healing and inflammatory processes.

Immunohistochemical Evaluation of Periodontal Regeneration Using a Porous Collagen Scaffold

(1) Aim: To immunohistochemically evaluate the effect of a volume-stable collagen scaffold (VCMX) on periodontal regeneration. (2) Methods: In eight beagle dogs, acute two-wall intrabony defects were treated with open flap debridement either with VCMX (test) or without (control). After 12 weeks, eight defects out of four animals were processed for paraffin histology and immunohistochemistry. (3) Results: All defects (four test + four control) revealed periodontal regeneration with cementum and bone formation. VCMX remnants were integrated in bone, periodontal ligament (PDL), and cementum. No differences in immunohistochemical labeling patterns were observed between test and control sites. New bone and cementum were labeled for bone sialoprotein, while the regenerated PDL was labeled for periostin and collagen type 1. Cytokeratin-positive epithelial cell rests of Malassez were detected in 50% of the defects. The regenerated PDL demonstrated a larger blood vessel area at the test (14.48% ± 3.52%) than at control sites (8.04% ± 1.85%, p = 0.0007). The number of blood vessels was higher in the regenerated PDL (test + control) compared to the pristine one (p = 0.012). The cell proliferative index was not statistically significantly different in pristine and regenerated PDL. (4) Conclusions: The data suggest a positive effect of VCMX on angiogenesis and an equally high cell turnover in the regenerated and pristine PDL. This VCMX supported periodontal regeneration in intrabony defects.

Combination of enamel matrix derivative and hyaluronic acid inhibits lipopolysaccharide-induced inflammatory response on human epithelial and bone cells

Objectives

The aim of this study was to evaluate the in vitro effect of enamel matrix derivative (EMD) and hyaluronic acid (HA) and their synergistic combination on lipopolysaccharides (LPS)-induced inflammation in human keratinocytes and osteoblasts.

Material and methods

Cells were challenged with LPS (1 μg/ml) and cultured in the following treatment groups with EMD (30 mg/ml) and HA (30 mg/ml): LPS, EMD, HA, EMD + HA, EMD + LPS, HA + LPS, and EMD + HA + LPS. Cell viability, inflammatory cytokine expression, and cell migration were determined using colorimetric assay, quantitative real-time polymerase chain reaction (qPCR), and scratch wound healing assay, respectively.

Results

Cell viability was decreased when exposed to LPS compared to the controls. Overall, LPS treatment expressed upregulation on inflammatory cytokine tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6). EMD and HA reduced up to 3.0-fold the cytokine expression caused by LPS (p < 0.05). EMD and HA statistically induced higher migration in osteoblasts and keratinocytes, respectively. Migration was impaired by LPS, whereas it significantly increased after addition of EMD and HA.

Conclusions

EMD and HA are advantageous biomaterials that individually generate strong directional migratory keratinocyte and osteoblast response. Their combination also enhances cell viability, and anti-inflammatory and migratory abilities to promote healing specially under LPS inflammatory stimulus. Future in vivo and animal research is necessary to further characterize the effect of EMD and HA on periodontal regeneration.

Clinical relevance

The use of EMD in conjunction with HA resulted in a reduction of inflammation and improvement of tissue healing at wound sites. Both biomaterials combined may potentially improve the effectiveness of bone regeneration in periodontal bone defects, pointing to the potential clinical relevance of both materials in regenerative periodontal surgery.

Effect of interleukin-1β on bone morphogenetic protein-9-induced osteoblastic differentiation of human periodontal ligament fibroblasts

Bone morphogenetic protein-9 (BMP-9) has been shown to potently induce osteoblastic differentiation of periodontal ligament fibroblasts (PDLFs) and may be a candidate therapeutic agent for periodontal tissue healing/regeneration, but the effect of the inflammatory environment of periodontitis on such approaches is unclear. We investigated whether interleukin-1β (IL-1β) affected BMP-9-mediated osteoblastic differentiation of human (h) PDLFs. IL-1β suppressed BMP-9-induced osteogenic differentiation of hPDLFs, as evidenced by reduced alkaline phosphatase (ALP) activity and mineralization, and the downregulated expression of BMP-9-mediated bone-related genes, RUNX2, SP7, IBSP, and SPP1. In hPDLFs, with or without BMP-9, IL-1β increased the protein expression of activin A, a BMP-9 antagonist, and decreased follistatin protein, an antagonist of activin A. Similarly, IL-1β upregulated the expression of the activin A gene and downregulated that of the follistatin gene. Notably, follistatin re-established BMP-9-induced ALP activity suppressed by IL-1β. Activin A inhibited the expression of BMP-9-responsive genes and BMP-9-induced ALP activity, while follistatin re-established them. Finally, extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and nuclear factor-kappa B (NF-κB) inhibition significantly blocked IL-1β-induced activin A gene expression. Our data indicate that IL-1β inhibits BMP-9-induced osteoblastic differentiation of hPDLFs, possibly by promoting activin A production via the ERK1/2, p38, and NF-κB pathways.

Pre-clinical evaluation of the effect of a volume-stable collagen matrix on periodontal regeneration in two-wall intrabony defects

AIM

To histologically evaluate the effect of a new collagen matrix on periodontal regeneration.

MATERIALS AND METHODS

Two-wall intrabony defects were surgically created bilaterally distally to the maxillary first and third pre-molars in beagle dogs. The defects were randomly allocated to open flap debridement either with (test) or without (control) a volume-stable collagen matrix (VCMX). After 12 weeks, the dogs were euthanized, and the specimens histologically processed. Descriptive, histomorphometrical (vertical gain of periodontal tissues) and statistical analyses were then performed.

RESULTS

Healing was uneventful in most cases. Residual VCMX was still present and showed integration into new bone, new periodontal ligament, connective tissue and, in some specimens, into new cementum. Periodontal regeneration occurred to a varying extent in both groups. New continuous cementum and new bone formation were statistically significantly greater in the test group (4.12 mm and 3.28 mm, respectively) than in the control group (1.54 mm and 2.47 mm, respectively) (p = .009 and p = .037, respectively). The junctional epithelium was longer in the control group (2.21 mm) than in the test group (1.49 mm, p = .16).

CONCLUSION

The present results have for the first time provided histologic evidence for the potential of this novel VCMX to facilitate periodontal regeneration thus warranting further pre-clinical and clinical testing.

Medium- and long-term clinical benefits of periodontal regenerative/reconstructive procedures in intrabony defects: Systematic review and network meta-analysis of randomized controlled clinical studies

BACKGROUND

Systematic reviews have established the short-term improvements of periodontal regenerative/reconstructive procedures compared to conventional surgical treatment in intrabony defects. However, a hierarchy of periodontal regenerative/reconstructive procedures regarding the medium- to long-term results of treatment does not exist.

AIM

To systematically assess the literature to answer the focused question "In periodontitis patients with intrabony defects, what are the medium- and long-term benefits of periodontal regenerative/reconstructive procedures compared with open flap debridement (OFD), in terms of clinical and/or radiographic outcome parameters and tooth retention?".

MATERIAL & METHODS

Randomized controlled clinical trials (RCTs), reporting on clinical and/or radiographic outcome parameters of periodontal regenerative/reconstructive procedures ≥3 years post-operatively, were systematically assessed. Clinical [residual probing pocket depth (PD) and clinical attachment level (CAL) gain, tooth loss] and radiographic [residual defect depth (RDD), bone gain (RBL)] outcome parameters were assessed. Descriptive statistics were calculated, and Bayesian random-effects network meta-analyses (NMA) were performed where possible.

RESULTS

Thirty RCTs, presenting data 3 to 20 years after treatment with grafting, GTR, EMD, as monotherapies, combinations thereof, and/or adjunctive use of blood-derived growth factor constructs or with OFD only, were included. NMA based on 21 RCTs showed that OFD was clearly the least efficacious treatment; regenerative/reconstructive treatments resulted in significantly shallower residual PD in 4 out 8 comparisons [range of mean differences (MD): -2.37 to -0.60 mm] and larger CAL gain in 6 out 8 comparisons (range of MD: 1.26 to 2.66 mm), and combination approaches appeared as the most efficacious. Tooth loss after regenerative/reconstructive treatment was less frequent (0.4%) compared to OFD (2.8%), but the evidence was sparse. There were only sparse radiographic data not allowing any relevant comparisons.

CONCLUSION

Periodontal regenerative/reconstructive therapy in intrabony defects results, in general, in shallower residual PD and larger CAL gain compared with OFD, translating in high rates of tooth survival, on a medium (3-5 years) to long-term basis (5-20 years). Combination approaches appear, in general, more efficacious compared to monotherapy in terms of shallower residual PD and larger CAL gain. A clear hierarchy could, however, not be established due to limited evidence.

Risk factors in bone augmentation procedures

Bone augmentation is an extremely common procedure in implant dentistry today because of significant advancements with reactive biomaterials, a better understanding of the mechanism of action that is found with growth factors contained in platelets, and improvements in surgical techniques. The expectation is for the surgeon to place the dental implant in the position that best serves the requirements of the prosthetic restorations. With the increasing demands that patients have for ideal prosthetic results, surgeons are expected to predictably augment both hard and soft tissues to provide the anticipated esthetic and functional outcomes. Bone grafting can be performed before, during, and after the implant placement; however, these augmentation procedures come with increased cost, the risk of complications such as infection or failure, and lengthening of the total treatment time. In addition, a plethora of grafting materials are available commercially, where they are often inadequately studied, or there is minimal information regarding their predictability or long-term success, or ability to support dental implants. It is clear that although the surgical field has seen major progress since early implant surgical techniques in the 1980s, major challenges still exist with hard tissue augmentation procedures. This review will discuss these challenges that are increased and often specific to bone graft healing, and which are becoming more common as implant site development often requires bone augmentation to improve volume or contour deficiencies. The risk factors that patients may present with that will affect outcomes with bone augmentation procedures are identified, and recommendations for the prevention of complications or managing complications once they have occurred are provided.

One-Year Results Evaluating the Effects of Concentrated Growth Factors on the Healing of Intrabony Defects Treated with or without Bone Substitute in Chronic Periodontitis

Background

The restoration of damaged periodontium, especially one-wall intrabony defects, is a major challenge for clinicians. Concentrated growth factors (CGF) are a 100% autologous fibrin with multiple concentrated growth factors. The rigid fibrin structure of CGF makes it possible to preserve or reconstruct the initial bone volume. The aim of this study was to evaluate the clinical healing patterns after surgical application of CGF with and without a Bio-Oss graft in one-wall infrabony defects.

Material/Methods

We randomly divided 120 one-wall intrabony defects in 54 patients into 4 groups: flap surgery alone (Group 1), flap surgery with autologous CGF (Group 2), flap surgery with Bio-Oss (Group 3), and flap surgery with CGF+Bio-Oss (Group 4). Clinical parameters such as probing depth (PD) and clinical attachment level (CAL) change were recorded at baseline and at 6 and 12 months postoperatively.

Results

At 12 months postoperatively, Group 2 showed significant improvement in clinical parameters over Group 1 (P<0.05) and the results were significantly greater in Groups 3 and 4 compared to the other groups (P<0.05). Although no significant difference was noted between Groups 3 and 4 in clinical parameters (P>0.05) compared to Group 3, the mean change of CAL at 6–12 months in Group 4 was not significant (P>0.05).

Conclusions

CGF reduced periodontal intrabony defects depth and, when mixed with Bio-Oss, CGF showed better results in the early period and the effect was more stable.

Tissue engineering in periodontology: Biological mediators for periodontal regeneration

Teeth and the periodontal tissues represent a highly specialized functional system. When periodontal disease occurs, the periodontal complex, composed by alveolar bone, root cementum, periodontal ligament, and gingiva, can be lost. Periodontal regenerative medicine aims at recovering damaged periodontal tissues and their functions by different means, including the interaction of bioactive molecules, cells, and scaffolds. The application of growth factors, in particular, into periodontal defects has shown encouraging effects, driving the wound healing toward the full, multi-tissue periodontal regeneration, in a precise temporal and spatial order. The aim of the present comprehensive review is to update the state of the art concerning tissue engineering in periodontology, focusing on biological mediators and gene therapy.

Clinical and radiographic evaluation and comparison of bioactive bone alloplast morsels when used alone and in combination with platelet-rich fibrin in the treatment of periodontal intrabony defects-A randomized controlled trial

BACKGROUND

The present study aims to evaluate and compare the clinical and radiographic changes obtained through Bioactive Glass (BG) with and without autologous platelet-rich fibrin (PRF) in the treatment of intrabony defects in chronic periodontitis patients.

METHODS

The present study was a split-mouth randomized controlled clinical trial comprising 20 chronic periodontitis patients (mean age: 35.9 years) having at least one pair of bilateral intrabony defect. Group 1 included 20 sites treated with a combination of BG and autologous PRF whereas 20 sites in Group 2 were treated with BG alone. Probing pocket depth (PPD), clinical attachment level (CAL) and gingival recession (GR) were evaluated at 3 and 6 months and bone fill at 6 months by using cone beam computed tomography (CBCT) analysis. Primary study outcomes were changes in PPD, CAL, GR, and bone fill.

RESULTS

CAL gain was greater in Group 1 (5.05 ± 1.09 mm) when compared with Group 2 (4.2 ± 1.70 mm). Furthermore, a significantly greater bone fill was found in Group 1. At 6 months, statistically significant reduction in PPD in Group 1 and Group 2 was evident.

CONCLUSION

BG morsel when used in combination with PRF is found to be more effective in gain in CAL, reduction in PPD and achieving greater bone fill as compared with treatment with BG alone in periodontal intrabony defects and is indicative of enhanced periodontal regeneration.

Nanogel Tectonics for Tissue Engineering: Protein Delivery Systems with Nanogel Chaperones

Amphiphilic polysaccharide self-assembled (SA) nanogels are promising protein carriers owing to their chaperone-like activity that allows them to nanoencapsulate proteins within their polymer networks. The chaperoning function is an important concept that has led to breakthroughs in the development of effective protein drug delivery systems by stabilizing formulations and controlling the quality of unstable proteins. Recently, nanogel-tectonic materials that integrate SA nanogels as building blocks have been designed as new hydrogel biomaterials. This article describes recent progress and applications of SA nanogel tectonic materials as protein delivery systems for tissue engineering.

Statins in nonsurgical and surgical periodontal therapy. A systematic review and meta-analysis of preclinical in vivo trials

The cholesterol-lowering drugs, statins, possess anti-inflammatory, antimicrobial and pro-osteogenic properties, and thus have been tested as an adjunct to periodontal treatment. The present systematic review aimed to answer the following focused research question: What is the effect of local and/or systemic statin use on periodontal tissues in preclinical in vivo studies of experimentally induced periodontitis (EIP) and/or acute/chronified periodontal defect (ACP) models? A literature search (of Medline/PubMed, Embase/Ovid, CENTRAL/Ovid) using the following main eligibility criteria was performed: (i) English or German language; (ii) controlled preclinical in vivo trials; (iii) local and/or systemic statin use in EIP and/or ACP models; and (iv) quantitative evaluation of periodontal tissues (i.e., alveolar bone level/amount, attachment level, cementum formation, periodontal ligament formation). Sixteen studies in EIP models and 7 studies in ACP models evaluated simvastatin, atorvastatin or rosuvastatin. Thirteen of the EIP (81%) and 2 of the ACP (29%) studies presented significantly better results in terms of alveolar bone level/amount in favor of statins. Meta-analysis based on 14 EIP trials confirmed a significant benefit of local and systemic statin use (P < .001) in terms of alveolar bone level/amount; meta-regression revealed that statin type exhibited a significant effect (P = .014) in favor of atorvastatin. Three studies reported a significantly higher periodontal attachment level in favor of statin use (P < .001). Complete periodontal regeneration was never observed; furthermore, statins did not exert any apparent effect on cementum formation. Neither local nor systemic use of statins resulted in severe adverse effects. Statin use in periodontal indications has a positive effect on periodontal tissue parameters, supporting the positive results already observed in clinical trials. Nevertheless, not all statins available have been tested so far, and further research is needed to identify the maximum effective concentration/dose and optimal carrier.

Quantification of growth factors in different platelet concentrates

Concentrated growth factor (CGF), a new generation of platelet concentrate product, appears to have more abundant growth factors because of its special centrifugation process. However, there are few studies supporting this. This study was designed to evaluate the contents of major growth factors in CGF and compare them with those found in PRP (platelet-rich plasma) and PRF (platelet-rich fibrin). PRP, PRF, and CGF were obtained from the same samples of peripheral blood. Concentrations of five representative growth factors in platelets were measured with enzyme-linked immunosorbent assay (ELISA): platelet-derived growth factor-BB (PDGF-BB), transforming growth factor β-1 (TGF-β1), insulin-like growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF). The results showed that the bFGF levels in CGF and PRF were significantly higher than that in activated PRP. For other growth factors, such as PDGF-BB, TGF-β1, IGF-1, and VEGF, the levels did not differ significantly among activated PRP, PRF, and CGF. Our findings extended the currently available data on the release and measurement of growth factors in CGF and other platelet gels. In future studies, we need more data to find the proper therapeutic doses for platelet concentrates suitable for different clinical applications.

Effects of diode laser irradiation and fibroblast growth factor on periodontal healing of replanted teeth after extended extra-oral dry time

AIM

The search for effective protocols to reduce the incidence of root resorption and allow periodontal ligament repair is still challenging, given the unpredictable outcome of late tooth replantation. The aim of this study was to assess the effects of both high-power diode laser irradiation (DL) and basic fibroblast growth factor (FGF) on the periodontal healing of replanted teeth after extended extra-oral dry time.

METHODS

Maxillary incisors of 50 male rats were extracted and assigned to three experimental and two control groups (n = 10). DL: root surfaces treated with DL (810 nm, continuous mode, 1.0 W, 30 s), FGF: topical application of FGF gel to the root surface and in the alveolar wound, DL + FGF: DL and topical application of FGF gel, C+: no treatment after extraction and immediate replantation and C-: no treatment after extraction and replantation after 60 min. In the experimental groups, the specimens were kept dry for 60 min, the pulps were removed and the canals were filled with calcium hydroxide paste prior to tooth replantation. The animals were euthanized after 60 days. The specimens were processed for radiographic, histological and immunohistochemical analyses.

RESULTS

The radiographic analysis showed fewer resorptive areas in DL + FGF (P < 0.05). The histological and immunohistochemical analyses showed that the DL group had lower mean values of ankylosis, replacement and inflammatory resorption when compared to C-, not differing statistically from C+. DL + FGF produced significantly more collagen fibers (type I and type III) than C-, not differing from C+ in the case of type I fibers (P < 0.05).

CONCLUSIONS

DL, with or without FGF, reduced the occurrence of external root resorption and ankylosis. Periodontal healing was favored and some fiber reinsertion occurred only when FGF was used.

In vitro characterization of an osteoinductive biphasic calcium phosphate in combination with recombinant BMP2

BACKGROUND

The repair of alveolar bone defects with growth factors and bone grafting materials has played a pivotal role in modern dentistry. Recombinant human bone morphogenetic protein-2 (rhBMP2), an osteoinductive growth factor capable of cell recruitment and differentiation towards the osteoblast lineage, has been utilized in combination with various biomaterials to further enhance new bone formation. Recently, a group of novel biphasic calcium phosphate (BCP) bone grafting materials have been demonstrated to possess osteoinductive properties by demonstrating signs of ectopic bone formation. The aim of the present study was to study the effects of rhBMP2 in combination with osteoinductive BCP bone grafts on osteoblast cell behaviour.

METHODS

MC3T3-E1 pre-osteoblasts were seeded on 1) control tissue culture plastic, 2) 10 mg of BCP alone, 3) 100 ng rhBMP2, and 4) 100 ng rhBMP2+ 10 mg of BCP and analyzed for cell recruitment via a Transwell chamber, proliferation via an MTS assay and differentiation as assessed by alkaline phosphatase (ALP) activity, alizarin red staining and real-time PCR for osteoblast differentiation markers including Runx2, collagen1, ALP, and osteocalcin (OCN).

RESULTS

rhBMP2 was able to significantly upregulate cell recruitment whereas the addition of BCP as well as BCP alone had no additional ability to improve osteoblast recruitment. Both BCP and rhBMP2 were able to significantly increase cell proliferation at 3 and 5 days post seeding and cell number was further enhanced when rhBMP2 was combined with BCP. In addition, the combination of rhBMP2 with BCP significantly improved ALP activity at 7 and 14 days post seeding, alizarin red staining at 14 days, and mRNA levels of Runx2, ALP and osteocalcin when compared to cells seeded with rhBMP2 alone or BCP alone.

CONCLUSIONS

The results from the present study demonstrate that 1) the osteoinductive potential of BCP bone particles is equally as osteopromotive as rhBMP2 on in vitro osteoblast differentiation and 2) BCP particles in combination with rhBMP2 is able to further increase the osteopromotive differentiation of osteoblasts in vitro when compared to either rhBMP2 alone or BCP alone. Future animal testing is further required to investigate this combination approach on new bone formation.

Recombinant human bone morphogenetic protein-9 potently induces osteogenic differentiation of human periodontal ligament fibroblasts

To accomplish effective periodontal regeneration for periodontal defects, several regenerative methods using growth and differentiation factors, including bone morphogenetic proteins (BMPs), have been developed. Bone morphogenetic protein-9 exhibits the most potent osteogenic activity of this growth factor family. However, it is unclear whether exogenous BMP-9 can induce osteogenic differentiation in human periodontal ligament (PDL) fibroblasts. Here, we examined the effects of recombinant human (rh) BMP-9 on osteoblastic differentiation in human PDL fibroblasts in vitro, compared with rhBMP-2. Recombinant human BMP-9 potently induced alkaline phosphatase (ALP) activity, mineralization, and increased expression of runt-related transcription factor-2/core binding factor alpha 1 (RUNX2/CBFA1), osterix, inhibitor of DNA binding/differentiation-1 (ID1), osteopontin, and bone sialoprotein genes, compared with rhBMP-2. The levels of rhBMP-9-induced osterix and ALP mRNA were significantly reduced in activin receptor-like kinase-1 and -2 small interfering RNA (siRNA)-transfected human PDL fibroblasts. Recombinant human BMP-9-induced ALP activity was not inhibited by noggin, in contrast to rhBMP-2 induced ALP activity, which was. Phosphorylation of SMAD1/5/8 in human PDL fibroblasts was induced by addition of rhBMP-9. Recombinant human BMP-9-induced ALP activity was suppressed by SB203580, SP600125, and U0126, which are inhibitors of p38, c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase 1/2 (ERK1/2), respectively. Our data suggest that rhBMP-9 is a potent inducer of the differentiation of human PDL fibroblasts into osteoblast-like cells and that this may be mediated by the SMAD and mitogen-activated protein kinase (p38, ERK1/2, and JNK) pathways.

Growth factors and beta-tricalcium phosphate in the treatment of periodontal intraosseous defects: A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

To evaluate the effectiveness at different points in time, of recombinant human platelet-derived growth factor-BB (rhPDGF-BB) coated onto a beta-tricalcium phosphate (β-TCP) carrier compared to β-TCP alone, or to recombinant human growth/differentiation factor-5 (rhGDF-5) adsorbed onto a β-TCP scaffold in intraosseous periodontal defects.

DESIGN

A digital search for randomised controlled trials (RCTs) was conducted on MEDLINE/PubMed. The quality of reporting and the risk of bias of the included RCTs were assessed using the CONSORT guidelines and the Cochrane risk of bias tool. The difference between the means of the outcomes at baseline and at follow-up for each group was tested using the Student's t-test for paired samples. The difference between the means of the outcome changes at follow-up between groups was analysed using the Student's t-test for two independent samples. Prior to each analysis a test of homogeneity of variances (Ansari-Bradley) was performed.

RESULTS

From 11 articles assessed for eligibility, 5 RCTs were included in this review. The risk of bias was considered to be low in 2 articles, medium in 1 study and high in 2 studies.

CONCLUSIONS

In the treatment of periodontal intraosseous defects the application of rhPDGF-BB/β-TCP improved all outcomes when compared to β-TCP at 6 months follow-up. Either rhPDGF-BB/β-TCP or rhGDF-5/β-TCP seemed to provide similar results in terms of probing pocket depth (PPD) reduction and clinical attachment level (CAL) gain. The application of rhGDF-5/β-TCP resulted in a more pronounced reduction in gingival recession (GR) depth at 6 months follow-up compared to rhPDGF-BB/β-TCP.

FGF-2 induces the proliferation of human periodontal ligament cells and modulates their osteoblastic phenotype by affecting Runx2 expression in the presence and absence of osteogenic inducers

The exact phenotype of human periodontal ligament cells (hPDLCs) remains a controversial area. Basic fibroblast growth factor (FGF-2) exhibits various functions and its effect on hPDLCs is also controversial. Therefore, the present study examined the effect of FGF-2 on the growth and osteoblastic phenotype of hPDLCs with or without osteogenic inducers (dexamethasone and β-glycerophosphate). FGF-2 was added to defined growth culture medium and osteogenic inductive culture medium. Cell proliferation, osteogenic differentiation and mineralization were measured. The selected differentiation markers, Runx2, collagen type I, α1 (Col1a1), osteocalcin (OCN) and epidermal growth factor receptor (EGFR), were investigated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Runx2 and OCN protein expression was measured by western blotting. FGF-2 significantly increased the proliferation of hPDLCs, but did not affect alkaline phosphatase activity. RT-qPCR analysis revealed enhanced mRNA expression of Runx2, OCN and EGFR, but suppressed Col1a1 gene expression in the absence of osteogenic inducers, whereas all these gene levels had no clear trend in their presence. The Runx2 protein expression was clearly increased, but the OCN protein level showed no evident trend. The mineralization assay demonstrated that FGF-2 inhibited mineralized matrix deposition with osteogenic inducers. These results suggested that FGF-2 induces the growth of immature hPDLCs, which is a competitive inhibitor of epithelial downgrowth, and suppresses their differentiation into mineralized tissue by affecting Runx2 expression. Therefore, this may lead to the acceleration of periodontal regeneration.

Wound models for periodontal and bone regeneration: the role of biologic research

The ultimate goals of periodontal therapy remain the complete regeneration of those periodontal tissues lost to the destructive inflammatory-immune response, or to trauma, with tissues that possess the same structure and function, and the re-establishment of a sustainable health-promoting biofilm from one characterized by dysbiosis. This volume of Periodontology 2000 discusses the multiple facets of a transition from therapeutic empiricism during the late 1960s, toward regenerative therapies, which is founded on a clearer understanding of the biophysiology of normal structure and function. This introductory article provides an overview on the requirements of appropriate in vitro laboratory models (e.g. cell culture), of preclinical (i.e. animal) models and of human studies for periodontal wound and bone repair. Laboratory studies may provide valuable fundamental insights into basic mechanisms involved in wound repair and regeneration but also suffer from a unidimensional and simplistic approach that does not account for the complexities of the in vivo situation, in which multiple cell types and interactions all contribute to definitive outcomes. Therefore, such laboratory studies require validatory research, employing preclinical models specifically designed to demonstrate proof-of-concept efficacy, preliminary safety and adaptation to human disease scenarios. Small animal models provide the most economic and logistically feasible preliminary approaches but the outcomes do not necessarily translate to larger animal or human models. The advantages and limitations of all periodontal-regeneration models need to be carefully considered when planning investigations to ensure that the optimal design is adopted to answer the specific research question posed. Future challenges lie in the areas of stem cell research, scaffold designs, cell delivery and choice of growth factors, along with research to ensure appropriate gingival coverage in order to prevent gingival recession during the healing phase.

Counter-regulatory phosphatases TNAP and NPP1 temporally regulate tooth root cementogenesis

Cementum is critical for anchoring the insertion of periodontal ligament fibers to the tooth root. Several aspects of cementogenesis remain unclear, including differences between acellular cementum and cellular cementum, and between cementum and bone. Biomineralization is regulated by the ratio of inorganic phosphate (P_i) to mineral inhibitor pyrophosphate (PP_i), where local P_i and PP_i concentrations are controlled by phosphatases including tissue-nonspecific alkaline phosphatase (TNAP) and ectonucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). The focus of this study was to define the roles of these phosphatases in cementogenesis. TNAP was associated with earliest cementoblasts near forming acellular and cellular cementum. With loss of TNAP in the Alpl null mouse, acellular cementum was inhibited, while cellular cementum production increased, albeit as hypomineralized cementoid. In contrast, NPP1 was detected in cementoblasts after acellular cementum formation, and at low levels around cellular cementum. Loss of NPP1 in the Enpp1 null mouse increased acellular cementum, with little effect on cellular cementum. Developmental patterns were recapitulated in a mouse model for acellular cementum regeneration, with early TNAP expression and later NPP1 expression. In vitro, cementoblasts expressed Alpl gene/protein early, whereas Enpp1 gene/protein expression was significantly induced only under mineralization conditions. These patterns were confirmed in human teeth, including widespread TNAP, and NPP1 restricted to cementoblasts lining acellular cementum. These studies suggest that early TNAP expression creates a low PP_i environment promoting acellular cementum initiation, while later NPP1 expression increases PP_i, restricting acellular cementum apposition. Alterations in PP_i have little effect on cellular cementum formation, though matrix mineralization is affected.

Effect of bone graft density on in vitro cell behavior with enamel matrix derivative

OBJECTIVES

Bone replacement grafting materials play an important role in regenerative dentistry. Despite a large array of tested bone-grafting materials, little information is available comparing the effects of bone graft density on in vitro cell behavior. Therefore, the aim of the present study is to compare the effects of cells seeded on bone grafts at low and high density in vitro for osteoblast adhesion, proliferation, and differentiation.

MATERIALS AND METHODS

The response of osteoblasts to the presence of a growth factor (enamel matrix derivative, (EMD)) in combination with low (8 mg per well) or high (100 mg per well) bone grafts (BG; natural bone mineral, Bio-Oss®) density, was studied and compared for osteoblast cell adhesion, proliferation, and differentiation as assessed by real-time PCR. Standard tissue culture plastic was used as a control with and without EMD.

RESULTS

The present study demonstrates that in vitro testing of bone-grafting materials is largely influenced by bone graft seeding density. Osteoblast adhesion was up to 50 % lower when cells were seeded on high-density BG when compared to low-density BG and control tissue culture plastic. Furthermore, proliferation was affected in a similar manner whereby cell proliferation on high-density BG (100 mg/well) was significantly increased when compared to that on low-density BG (8 mg/well). In contrast, cell differentiation was significantly increased on high-density BG as assessed by real-time PCR for markers collagen 1 (Col 1), alkaline phosphatase (ALP), and osteocalcin (OC) as well as alizarin red staining. The effects of EMD on osteoblast adhesion, proliferation, and differentiation further demonstrated that the bone graft seeding density largely controls in vitro results. EMD significantly increased cell attachment only on high-density BG, whereas EMD was able to further stimulate cell proliferation and differentiation of osteoblasts on control culture plastic and low-density BG when compared to high-density BG.

CONCLUSION

The results from the present study demonstrate that the in vitro conditions largely influence cell behavior of osteoblasts seeded on bone grafts and in vitro testing.

CLINICAL RELEVANCE

These results also illustrate the necessity for careful selection of bone graft seeding density to optimize in vitro testing and provide the clinician with a more accurate description of the osteopromotive potential of bone grafts.

Akt activation is required for TGF-β1-induced osteoblast differentiation of MC3T3-E1 pre-osteoblasts

Background

We have previously reported that repeated treatment of human periodontal ligament cells and murine pre-osteoblast MC3T3-E1 cells with transforming growth factor-beta 1 (TGF-β1) inhibited their osteoblastic differentiation because of decreased insulin-like growth factor-1 (IGF-1) secretion. We also found that IGF-1/PI3K signaling plays an important role in osteoblast differentiation induced by TGF-β1 treatment; however, the downstream signaling controlling this remains unknown. The aim of this current study is to investigate whether Akt activation is required for osteoblast differentiation.

Methodology/Principal Findings

MC3T3-E1 cells were cultured in osteoblast differentiation medium (OBM) with or without 0.1 ng/mL TGF-β1. OBM containing TGF-β1 was changed every 12 h to provide repeated TGF-β1 administration. MC3T3-E1 cells were infected with retroviral vectors expressing constitutively active (CA) or dominant-negative (DN)-Akt. Alkaline phosphatase (ALP) activity and osteoblastic marker mRNA levels were substantially decreased by repeated TGF-β1 treatment compared with a single TGF-β1 treatment. However, expression of CA-Akt restored ALP activity following TGF-β1 treatment. Surprisingly, ALP activity increased following multiple TGF-β1 treatments as the number of administrations of TGF-β1 increased. Activation of Akt significantly enhanced expression of osteocalcin, but TGF-β1 treatment inhibited this. Mineralization of MC3T3-E1 cells was markedly enhanced by CA-Akt expression under all medium conditions. Exogenous IGF-1 restored the down-regulation of osteoblast-related gene expression by repeated TGF-β1 administration. However, in cells expressing DN-Akt, these levels remained inhibited regardless of IGF-1 treatment. These findings indicate that Akt activation is required for the early phase of osteoblast differentiation of MC3T3-E1 cells induced by TGF-β1. However, Akt activation is insufficient to reverse the inhibitory effects of TGF-β1 in the late stages of osteoblast differentiation.

Conclusions

TGF-β1 could be an inducer or an inhibitor of osteoblastic differentiation of MC3T3-E1 cells depending on the state of Akt phosphorylation. Our results indicate that Akt is the molecular switch for TGF-β1-induced osteoblastic differentiation of MC3T3-E1 cells.

Regenerative periodontal therapy: 30 years of lessons learned and unlearned

In this review, we reflect upon advances and hindrances encountered over the last three decades in the development of strategies for periodontal regeneration. In this soul-searching pursuit we focus on revisiting lessons learned that should guide us in the quest for the reconstruction of the lost periodontium. We also examine beliefs and traditions that should be unlearned so that we can continue to advance the field. This learned/unlearned body of knowledge is consolidated into core principles to help us to develop new therapeutic approaches to benefit our patients and ultimately our society.

Periodontology: past, present, perspectives

Periodontitis is an infectious disease that affects the tooth-supporting tissues and exhibits a wide range of clinical, microbiological and immunological manifestations. The disease is associated with and is probably caused by a multifaceted dynamic interaction of specific infectious agents, host immune responses, harmful environmental exposure and genetic susceptibility factors. This volume of Periodontology 2000 covers key subdisciplines of periodontology, ranging from etiopathogeny to therapy, with emphasis on diagnosis, classification, epidemiology, risk factors, microbiology, immunology, systemic complications, anti-infective therapy, reparative treatment, self-care and affordability issues. Learned and unlearned concepts of periodontitis over the past 50 years have shaped our current understanding of the etiology of the disease and of clinical practice.

Cyclic tensile force up-regulates BMP-2 expression through MAP kinase and COX-2/PGE2 signaling pathways in human periodontal ligament cells

Periodontal ligament cells play important roles in the homeostasis of periodontal tissue by mechanical stress derived from mastication, such as tension, compression, fluid shear, and hydrostatic force. In the present study, we showed that cyclic tensile force increased the gene expression level of bone morphogenetic protein (BMP)-2, a crucial regulator of mineralization, in human periodontal ligament cells using real-time PCR. Signaling inhibitors, PD98059/U0126 (extracellular signal-regulated kinase (ERK) inhibitors) and SB203580/SB202190 (p38 inhibitors), revealed that tensile force-mediated BMP-2 expression was dependent on activation of the ERK1/2 and p38 mitogen-activated protein (MAP) kinase pathways. Cyclic tensile force also induced cyclooxygenase-2 (COX-2) gene expression in a manner dependent on ERK1/2 and p38 MAP kinase pathways, and induced prostaglandin E2 (PGE2) biosynthesis. NS-398, a COX-2 inhibitor, significantly reduced tensile force-mediated BMP-2 expression, indicating that PGE2 synthesized by COX-2 may be involved in the BMP-2 induction. The inhibitory effect of NS-398 was completely restored by the addition of exogenous PGE2. However, stimulation with PGE2 alone in the absence of tensile force had no effect on the BMP-2 induction, indicating that some critical molecule(s) other than COX-2/PGE2 may be required for cyclic tensile force-mediated BMP-2 induction. Collectively, the results indicate that cyclic tensile force activates ERK1/2 and p38 MAP kinase signaling pathways, and induces COX-2 expression, which is responsible for the sequential PGE2 biosynthesis and release, and furthermore, mediates the increase in BMP-2 expression at the transcriptional level.

Platelet-rich plasma, low-level laser therapy, or their combination promotes periodontal regeneration in fenestration defects: a preliminary in vivo study

BACKGROUND

This study histomorphometrically analyzes the influence of platelet-rich plasma (PRP), low-level laser therapy (LLLT), or their combination on the healing of periodontal fenestration defects (PFDs) in rats.

METHODS

PFDs were surgically created in the mandibles of 80 rats. The animals were randomly divided into four groups: 1) C (control) and 2) PRP, defects were filled with blood clot or PRP, respectively; 3) LLLT and 4) PRP/LLLT, defects received laser irradiation, were filled with blood clot or PRP, respectively, and then irradiated again. Animals were euthanized at either 10 or 30 days post-surgery. Percentage of new bone (NB), density of newly formed bone (DNB), new cementum (NC), and extension of remaining defect (ERD) were histomorphometrically evaluated. Data were statistically analyzed (analysis of variance; Tukey test, P <0.05).

RESULTS

At 10 days, group PRP presented ERD significantly lower than group C. At 30 days, group PRP presented NB and DNB significantly greater than group C. Groups LLLT, PRP, and PRP/LLLT showed significant NC formation at 30 days, with collagen fibers inserted obliquely or perpendicularly to the root surface. NC formation was not observed in any group C specimen.

CONCLUSIONS

LLLT, PRP, or their combination all promoted NC formation with a functional periodontal ligament. The combination PRP/LLLT did not show additional positive effects compared to the use of either therapy alone.