Wound healing of degree III furcation involvements following guided tissue regeneration and/or Emdogain®

Exploring the Use of Animal Models in Craniofacial Regenerative Medicine: A Narrative Review

The craniofacial region contains skin, bones, cartilage, the temporomandibular joint (TMJ), teeth, periodontal tissues, mucosa, salivary glands, muscles, nerves, and blood vessels. Applying tissue engineering therapeutically helps replace lost tissues after trauma or cancer. Despite recent advances, it remains essential to standardize and validate the most appropriate animal models to effectively translate preclinical data to clinical situations. Therefore, this review focused on applying various animal models in craniofacial tissue engineering and regeneration. This research was based on PubMed, Scopus, and Google Scholar data available until January 2023. This study included only English-language publications describing animal models' application in craniofacial tissue engineering (in vivo and review studies). Study selection was based on evaluating titles, abstracts, and full texts. The total number of initial studies was 6454. Following the screening process, 295 articles remained on the final list. Numerous in vivo studies have shown that small and large animal models can benefit clinical conditions by assessing the efficacy and safety of new therapeutic interventions, devices, and biomaterials in animals with similar diseases/defects to humans. Different species' anatomical, physiologic, and biological features must be considered in developing innovative, reproducible, and discriminative experimental models to select an appropriate animal model for a specific tissue defect. As a result, understanding the parallels between human and veterinary medicine can benefit both fields.

Porcine-derived soft block bone substitutes for the treatment of severe class II furcation-involved mandibular molars: a prospective controlled follow-up study

PURPOSE

No evidence exists regarding the advantages of periodontal regeneration treatment for furcation defects using soft block bone substitutes. Therefore, this randomized controlled trial aimed to assess the clinical and radiographic outcomes of regenerative therapy using porcine-derived soft block bone substitutes (DPBM-C, test group) compared with porcine-derived particulate bone substitutes (DPBM, control group) for the treatment of severe class II furcation defects in the mandibular molar regions.

METHODS

Thirty-five enrolled patients (test group, n=17; control group, n=18) were available for a 12-month follow-up assessment. Clinical (probing pocket depth [PPD] and clinical attachment level [CAL]) and radiographic (vertical furcation defect; VFD) parameters were evaluated at baseline and 6 and 12 months after regenerative treatment. Early postoperative discomfort (severity and duration of pain and swelling) and wound healing outcomes (dehiscence, suppuration, abscess formation, and swelling) were also assessed 2 weeks after surgery.

RESULTS

For both treatment modalities, significant improvements in PPD, CAL, and VFD were found in the test group (PPD reduction of 4.1±3.0 mm, CAL gain of 4.4±2.9 mm, and VFD reduction of 4.1±2.5 mm) and control group (PPD reduction of 2.7±2.0 mm, CAL gain of 2.0±2.8 mm, and VFD reduction of 2.4±2.5 mm) 12 months after the regenerative treatment of furcation defects (P<0.05). However, no statistically significant differences were found in any of the measured clinical and radiographic parameters, and no significant differences were observed in any early postoperative discomfort and wound healing outcomes between the 2 groups.

CONCLUSIONS

Similar to DPBM, DPBM-C showed favorable clinical and radiographic outcomes for periodontal regeneration of severe class II furcation defects in a 12-month follow-up period.

TRIAL REGISTRATION

Clinical Research Information Service Identifier: KCT0007305.

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.

Treatment of intrabony periodontal defects in controlled diabetic patients with an enamel matrix derivative: a split-mouth randomized clinical trial

OBJECTIVE

This split-mouth randomized controlled trial aimed to evaluate the effect of enamel matrix derivative (EMD) associated with a simplified papilla preservation flap (SPPF) compared to SPPF alone in the surgical treatment of intrabony defects (ID) in type 2 diabetic mellitus (T2DM) patients.

MATERIAL AND METHODS

Thirteen patients with controlled T2DM presenting with ID in at least two quadrants were included. In each patient, the test site (TS) was treated with SPPF plus EMD, whereas the control site (CS) was treated only with SPPF. Prior to surgery and at 6 months after intervention, the following parameters were evaluated: clinical attachment level (CAL), probing pocket depth (PPD), and gingival recession (GR).

RESULTS

The TS and CS demonstrated a mean CAL gain of 3.31 ± 0.96 mm and 1.61 ± 1.12 mm, and a PPD reduction from 8.15 ± 0.98 to 3.00 ± 0.57 mm and 7.53 ± 0.96 to 4.69 ± 0.63 mm after 6 months, respectively. In both sites, the mean CAL gain and PPD reduction improved significantly after 6 months compared to baseline; however, the improvement was higher in the TS (p < 0.001).

CONCLUSIONS

Both surgical procedures presented with clinical improvements in controlled T2DM patients. However, the additional use of EMD showed enhanced clinical results after 6 months with regard to CAL gain and PPD reduction.

CLINICAL RELEVANCE

This study showed a better PPD reduction and CAL gain when an EMD was applied in addition to SPPF. Therefore, EMD may be used to enhance clinical outcomes in periodontal ID of controlled T2DM patients.

Positive Effects of Three-Dimensional Collagen-Based Matrices on the Behavior of Osteoprogenitors

Recent research has demonstrated that reinforced three-dimensional (3D) collagen matrices can provide a stable scaffold for restoring the lost volume of a deficient alveolar bone. In the present study, we aimed to comparatively investigate the migratory, adhesive, proliferative, and differentiation potential of mesenchymal stromal ST2 and pre-osteoblastic MC3T3-E1 cells in response to four 3D collagen-based matrices. Dried acellular dermal matrix (DADM), hydrated acellular dermal matrix (HADM), non-crosslinked collagen matrix (NCM), and crosslinked collagen matrix (CCM) did all enhance the motility of the osteoprogenitor cells. Compared to DADM and NCM, HADM and CCM triggered stronger migratory response. While cells grown on DADM and NCM demonstrated proliferative rates comparable to control cells grown in the absence of a biomaterial, cells grown on HADM and CCM proliferated significantly faster. The pro-proliferative effects of the two matrices were supported by upregulated expression of genes regulating cell division. Increased expression of genes encoding the adhesive molecules fibronectin, vinculin, CD44 antigen, and the intracellular adhesive molecule-1 was detected in cells grown on each of the scaffolds, suggesting excellent adhesive properties of the investigated biomaterials. In contrast to genes encoding the bone matrix proteins collagen type I (Col1a1) and osteopontin (Spp1) induced by all matrices, the expression of the osteogenic differentiation markers Runx2, Alpl, Dlx5, Ibsp, Bglap2, and Phex was significantly increased in cells grown on HADM and CCM only. Short/clinically relevant pre-coating of the 3D biomaterials with enamel matrix derivative (EMD) or recombinant bone morphogenetic protein-2 (rBMP-2) significantly boosted the osteogenic differentiation of both osteoprogenitor lines on all matrices, including DADM and NCM, indicating that EMD and BMP-2 retained their biological activity after being released from the matrices. Whereas EMD triggered the expression of all osteogenesis-related genes, rBMP-2 upregulated early, intermediate, and late osteogenic differentiation markers except for Col1a1 and Spp1. Altogether, our results support favorable influence of HADM and CCM on the recruitment, growth, and osteogenic differentiation of the osteoprogenitor cell types. Furthermore, our data strongly support the biofunctionalization of the collagen-based matrices with EMD or rBMP-2 as a potential treatment modality for bone defects in the clinical practice.

Cellular therapy in periodontal regeneration

Periodontitis is a chronic inflammatory condition leading to destruction of the tooth supporting tissues, which if left untreated may cause tooth loss. The treatment of periodontitis mainly aims to arrest the inflammatory process by infection control measures, although in some specific lesions a limited periodontal regeneration can also be attained. Current regenerative approaches are aimed to guide the cells with regenerative capacity to repopulate the lesion and promote new cementum and new connective tissue attachment. The first phase in periodontal tissue regeneration involves the differentiation of mesenchymal cells into cementoblasts to promote new cementum, thus facilitating the attachment of new periodontal ligament fibers to the root and the alveolar bone. Current regenerative approaches limit themselves to the confines of the lesion by promoting the self-regenerative potential of periodontal tissues. With the advent of bioengineered therapies, several studies have investigated the potential use of cell therapies, mainly the use of undifferentiated mesenchymal cells combined with different scaffolds. The understanding of the origin and differentiation patterns of these cells is, therefore, important to elucidate their potential therapeutic use and their comparative efficacy with current technologies. This paper aims to review the in vitro and experimental studies using cell therapies based on application of cementoblasts and mesenchymal stem cells isolated from oral tissues when combined with different scaffolds.

Histologic evidence of periodontal regeneration in furcation defects: a systematic review

OBJECTIVE

To systematically review the available histologic evidence on periodontal regeneration in class II and III furcations in animals and humans.

MATERIALS AND METHODS

A protocol including all aspects of a systematic review methodology was developed including definition of the focused question, defined search strategy, study inclusion criteria, determination of outcome measures, screening methods, data extraction and analysis, and data synthesis. The focused question was defined as follows: "What is the regenerative effect obtained by using or not several biomaterials as adjuncts to open flap surgery in the treatment of periodontal furcation defects as evaluated in animal and human histological studies?"

SEARCH STRATEGY

Using the MEDLINE database, the literature was searched for articles published up to and including September 2018: combinations of several search terms were applied to identify appropriate studies. Reference lists of review articles and of the included articles in the present review were screened. A hand search of the most important dental journals was also performed.

CRITERIA FOR STUDY SELECTION AND INCLUSION

Only articles published in English describing animal and human histological studies evaluating the effect of surgical treatment, with or without the adjunctive use of potentially regenerative materials (i.e., barrier membranes, grafting materials, growth factors/proteins, and combinations thereof) for the treatment of periodontal furcation defects were considered. Only studies reporting a minimum of 8 weeks healing following reconstructive surgery were included. The primary outcome variable was formation of periodontal supporting tissues [e.g., periodontal ligament, root cementum, and alveolar bone, given as linear measurements (in mm) or as a percentage of the instrumented root length (%)] following surgical treatment with or without regenerative materials, as determined histologically/histomorphometrically. Healing type and defect resolution (i.e., complete regeneration, long junctional epithelium, connective tissue attachment, connective tissue adhesion, or osseous repair) were also recorded.

RESULTS

In animals, periodontal regeneration was reported in class II and III defects with open flap debridement alone or combined with various types of bone grafts/bone substitues, biological factors, guided tissue regeneration, and different combinations thereof. The use of biological factors and combination approaches provided the best outcomes for class II defects whereas in class III defects, the combination approaches seem to offer the highest regenerative outcomes. In human class II furcations, the best outcomes were obtained with DFDBA combined with rhPDGF-BB and with GTR. In class III furcations, evidence from two case reports indicated very limited to no periodontal regeneration.

CONCLUSIONS

Within their limits, the present results suggest that (a) in animals, complete periodontal regeneration has been demonstrated in class II and class III furcation defects, and (b) in humans, the evidence for substantial periodontal regeneration is limited to class II furcations.

CLINICAL RELEVANCE

At present, regenerative periodontal surgery represents a valuable treatment option only for human class II furcation defects but not for class III furcations.

Furcation Therapy With Enamel Matrix Derivative: Effects on the Subgingival Microbiome

BACKGROUND

Although enamel matrix derivative (EMD) has been used to promote periodontal regeneration, little is known of its effect on the microbiome. Therefore, this investigation aims to identify changes in periodontal microbiome after treatment with EMD using a deep-sequencing approach.

METHODS

Thirty-nine patients with mandibular Class II buccal furcation defects were randomized to beta-tricalcium-phosphate/hydroxyapatite graft (BONE group), EMD+BONE, or EMD alone. Plaque was collected from furcation defects at baseline and 3 and 6 months post-treatment. Bacterial DNA was analyzed using terminal restriction fragment length polymorphism and 16S pyrotag sequencing, resulting in 169,000 classifiable sequences being compared with the Human Oral Microbiome Database. Statistical comparisons were made using parametric tests.

RESULTS

At baseline, a total of 422 species were identified from the 39 defects, belonging to Fusobacterium, Pseudomonas, Streptococcus, Filifactor, and Parvimonas. All three regenerative procedures predictably altered the disease-associated microbiome, with a restitution of health-compatible species. However, EMD and BONE+EMD groups demonstrated more long-term reductions in a higher number of species than the BONE group (P <0.05), especially disease-associated species, e.g., Selenomonas noxia, F. alocis, and Fusobacterium.

CONCLUSIONS

EMD treatment predictably alters a dysbiotic subgingival microbiome, decreasing pathogen richness and increasing commensal abundance. Further investigations are needed to investigate how this impacts regenerative outcomes.

Are Cementoblasts a Subpopulation of Osteoblasts or a Unique Phenotype?

Experimental studies have shown a great potential for periodontal regeneration. The limitations of periodontal regeneration largely depend on the regenerative potential at the root surface. Cellular intrinsic fiber cementum (CIFC), so-called bone-like tissue, may form instead of the desired acellular extrinsic fiber cementum (AEFC), and the interfacial tissue bonding may be weak. The periodontal ligament harbors progenitor cells that can differentiate into periodontal ligament fibroblasts, osteoblasts, and cementoblasts, but their precise location is unknown. It is also not known whether osteoblasts and cementoblasts arise from a common precursor cell line, or whether distinct precursor cell lines exist. Thus, there is limited knowledge about how cell diversity evolves in the space between the developing root and the alveolar bone. This review supports the hypothesis that AEFC is a unique tissue, while CIFC and bone share some similarities. Morphologically, functionally, and biochemically, however, CIFC is distinctly different from any bone type. There are several lines of evidence to propose that cementoblasts that produce both AEFC and CIFC are unique phenotypes that are unrelated to osteoblasts. Cementum attachment protein appears to be cementum-specific, and the expression of two proteoglycans, fibromodulin and lumican, appears to be stronger in CIFC than in bone. A theory is presented that may help explain how cell diversity evolves in the periodontal ligament. It proposes that Hertwig’s epithelial root sheath and cells derived from it play an essential role in the development and maintenance of the periodontium. The role of enamel matrix proteins in cementoblast and osteoblast differentiation and their potential use for tissue engineering are discussed.

Twenty years of enamel matrix derivative: the past, the present and the future

BACGROUND

On June 5th, 2015 at Europerio 8, a group of leading experts were gathered to discuss what has now been 20 years of documented evidence supporting the clinical use of enamel matrix derivative (EMD). Original experiments led by Lars Hammarström demonstrated that enamel matrix proteins could serve as key regenerative proteins capable of promoting periodontal regeneration including new cementum, with functionally oriented inserting new periodontal ligament fibres, and new alveolar bone formation. This pioneering work and vision by Lars Hammarström has paved the way to an enormous amount of publications related to its biological basis and clinical use. Twenty years later, it is clear that all these studies have greatly contributed to our understanding of how biologics can act as mediators for periodontal regeneration and have provided additional clinical means to support tissue regeneration of the periodontium.

AIMS

This review article aims to: (1) provide the biological background necessary to understand the rational for the use of EMD for periodontal regeneration, (2) present animal and human histological evidence of periodontal regeneration following EMD application, (3) provide clinically relevant indications for the use of EMD and (4) discuss future avenues of research including key early findings leading to the development of Osteogain, a new carrier system for EMD specifically developed with better protein adsorption to bone grafting materials.

Interaction of enamel matrix proteins with human periodontal ligament cells

Objectives

It has recently been shown that enamel matrix derivative (EMD) components (Fraction C, containing <6 kDa peptides (mainly a 5.3 kDa tyrosine-rich amelogenin peptide (TRAP)), and Fraction A, containing a mixture of >6 kDa peptides (including a leucine-rich amelogenin peptide (LRAP))) differentially regulate osteogenic differentiation of periodontal ligament (PDL) cells. The present study examined whether EMD and the EMD Fractions (i) bind and internalize into PDL cells and (ii) precipitate and form insoluble complexes on PDL cells.

Materials and methods

Biotin-labelled EMD/EMD Fractions were incubated with PDL cells under various different culture conditions and confocal and electron microscopies were carried out to examine the binding and intracellular trafficking of these proteins.

Results

The results reported here show, for the first time, that at least some components in Fraction A and the TRAP peptide in Fraction C can bind and be internalized by human PDL cells via receptor-mediated endocytosis. In addition, Fraction A was found to form insoluble aggregate-like structures on PDL cells, whereas Fraction C was soluble in culture media.

Conclusion

Soluble amelogenin isoform TRAP appears to be internalizing into a subset of PDL cells. Moreover, TRAP uptake is most likely controlled by receptor-mediated endocytosis.

Clinical relevance

Information on interaction between PDL cells and EMD/TRAP might prove useful in designing targeted interventions (i.e. use of chemically prepared soluble amelogenin peptides) to repair/regenerate periodontal tissues. Such interventions can also (i) avoid the use of rather crude animal-derived enamel matrix protein (EMP)/EMD preparation and (ii) preparation of cost-effective and more controlled chemically synthesized amelogenin peptides for the clinical use.

Electronic supplementary material

The online version of this article (doi:10.1007/s00784-015-1510-8) contains supplementary material, which is available to authorized users.

A tyrosine-rich amelogenin peptide promotes neovasculogenesis in vitro and ex vivo

The formation of new blood vessels has been shown to be fundamental in the repair of many damaged tissues, and we have recently shown that the adult human periodontal ligament contains multipotent stem/progenitor cells that are capable of undergoing vasculogenic and angiogenic differentiation in vitro and ex vivo. Enamel matrix protein (EMP) is a heterogeneous mixture of mainly amelogenin-derived proteins produced during tooth development and has been reported to be sometimes effective in stimulating these processes, including in clinical regeneration of the periodontal ligament. However, the identity of the specific bioactive component of EMP remains unclear. In the present study we show that, while the high-molecular-weight Fraction A of enamel matrix derivative (a heat-treated form of EMP) is unable to stimulate the vasculogenic differentiation of human periodontal ligament cells (HPC) in vitro, the low-molecular-weight Fraction C significantly up-regulates the expression of the endothelial markers VEGFR2, Tie-1, Tie-2, VE-cadherin and vWF and markedly increases the internalization of low-density lipoprotein. Furthermore, we also demonstrate, for the first time, that the synthetic homolog of the 45-amino acid tyrosine-rich amelogenin peptide (TRAP) present in Fraction C is likely to be responsible for its vasculogenesis-inducing activity. Moreover, the chemically synthesized TRAP peptide is also shown here to be capable of up-regulating the angiogenic differentiation of the HPC, based on its marked stimulation of in vitro cell migration and tubule formation and of blood vessel formation assay in a chick embryo chorioallantoic membrane model ex vivo. This novel peptide, and modified derivatives, might thereby represent a new class of regenerative drug that has the ability to elicit new blood vessel formation and promote wound healing in vivo.

Outcome of enamel matrix derivative treatment in the presence of chronic stress: histometric study in rats

BACKGROUND

Psychologic stress and clinical hypercortisolism have been related to direct effects on bone metabolism. However, there is a lack of information regarding the outcomes of regenerative approaches under the influence of chronic stress (CS). Enamel matrix derivative (EMD) has been used in periodontal regenerative procedures, resulting in improvement of clinical parameters. Thus, the aim of this histomorphometric study is to evaluate the healing of periodontal defects after treatment with EMD under the influence of CS in the rat model.

METHODS

Twenty Wistar rats were randomly assigned to two groups; G1: CS (restraint stress for 12 hours/day) (n = 10), and G2: not exposed to CS (n = 10). Fifteen days after initiation of CS, fenestration defects were created at the buccal aspect of the first mandibular molar of all animals from both groups. After the surgeries, the defects of each animal were randomly assigned to two subgroups: non-treated control and treated with EMD. The animals were euthanized 21 days later.

RESULTS

G1 showed less bone density (BD) compared to G2. EMD provided an increased defect fill (DF) in G1 and higher BD and new cementum formation (NCF) in both groups. The number of tartrate-resistant acid phosphatase-positive osteoclasts was significantly higher in G1 when compared to G2 and in EMD-treated sites of both groups.

CONCLUSIONS

CS may produce a significant detrimental effect on BD. EMD may provide greater DF compared to non-treated control in the presence of CS and increased BD and NCF in the presence or absence of CS.

Effects of enamel matrix proteins on multi-lineage differentiation of periodontal ligament cells in vitro

The adult periodontal ligament (PDL) is considered to contain progenitor cells that are involved in the healing of periodontal wounds. Treatment with enamel matrix derivative (EMD), a heat-treated preparation derived from enamel matrix proteins (EMPs), has been shown to be of some clinical benefit in eliciting periodontal regeneration in vivo. Although there is extensive information available about the effects of EMD on periodontal regeneration, the precise influence of this material on alveolar bone and the formation of blood vessels and proprioceptive sensory nerves, prominent features of functionally active periodontal tissue, remain unclear. The aim of the present study was therefore to examine the effects of EMD on the ability of human periodontal ligament cells (HPCs) to undergo multi-lineage differentiation in vitro. Our results showed that HPCs treated with EMD under non-selective growth conditions did not show any evidence of osteogenic, adipogenic, chondrogenic, neovasculogenic, neurogenic and gliogenic "terminal" differentiation. In contrast, under selective lineage-specific culture conditions, EMD up-regulated osteogenic, chondrogenic and neovasculogenic genes and "terminal" differentiation, but suppressed adipogenesis, neurogenesis and gliogenesis. These findings thus demonstrate for the first time that EMD can differentially modulate the multi-lineage differentiation of HPCs in vitro.

Differential effect of amelogenin peptides on osteogenic differentiation in vitro: identification of possible new drugs for bone repair and regeneration

Enamel matrix proteins (EMP) have been shown to promote regeneration of periodontal ligament and root cementum, and sometimes to enhance the differentiation of bone-forming cells in vitro and new bone growth in vivo. However, the inconsistent and unpredictable effects of EMP that have been reported for bone regeneration may be due to the highly variable composition of this heterogeneous material, which is comprised mainly of amelogenin and amelogenin-derived peptides. The present study has therefore examined the effects of naturally occurring low-molecular-weight (LMW) and high-molecular-weight (HMW) fractions of Emdogain(®) (EMD; Institut Straumann, Basel, Switzerland), a commercially available form of EMP, on osteogenic differentiation of bone precursor cells in vitro. In addition, the effects of chemically synthesized specific components of LMW and HMW-namely, the tyrosine-rich amelogenin peptide (TRAP), a specific amelogenin isoform derived by proteolytic clipping, and a leucine-rich amelogenin peptide (LRAP), an isoform derived by alternative splicing-on bone-forming cell activity were also investigated. Our findings demonstrate that while TRAP suppressed the formation of bone-like mineralized nodules, LRAP upregulated osteogenic differentiation. Furthermore, synthetically produced TRAP and its unique C-terminal 12 amino acid sequence (TCT) also suppressed bone-forming cells, whereas LRAP and its unique C-terminal 23 amino acid sequence (LCT) markedly enhanced terminal differentiation of bone-forming cells. These findings suggest that the differential effects of amelogenin-derived peptide sequences present in EMP could be of potential clinical value, with the novel bioactive TCT peptide as a useful tool for limiting pathological bone cell growth and the unique LCT sequence having therapeutic benefits in the treatment of periodontal and orthopedic diseases.

Enamel matrix protein derivatives: role in periodontal regeneration

The role of regenerative periodontal therapy is the reconstitution of lost periodontal structures, ie, new formation of root cementum, periodontal ligament, and alveolar bone. The outcome of basic research has pointed to the important role of enamel matrix protein derivative (EMD) in periodontal wound healing. Histologic results from animal and human studies have shown that treatment with EMD promotes periodontal regeneration. Moreover, clinical studies have indicated that treatment with EMD positively influences periodontal wound healing in humans. The goal of this paper is to review the existing literature on EMD.

Wound healing following regenerative procedures in furcation degree III defects: histomorphometric outcomes

Degree III furcation involvements were surgically created at four first molars in each of three monkeys. Following 6 weeks of healing, full-thickness flaps were elevated. Following 24% EDTA gel conditioning, the defects were treated with one of the following: (1) enamel matrix proteins (EMD), (2) guided tissue regeneration (GTR) or (3) a combination EMD and GTR. The control defects did not receive any treatment. After 5 months of healing, the animals were sacrificed. Three 8 μm thick histological central sections, 100 μm apart, were used for histomorphometric analysis in six zones of each tooth either within the furcation area or on the pristine external surface of the root. In all specimens, new cementum with inserting collagen fibres was formed. Following GTR or GTR + EMD, cementum was formed up to and including the furcation fornix indicating complete regeneration on the defect periphery. Periodontal ligament fibres were less in all four modalities compared to pristine tissues. In the teeth treated with GTR and GTR + EMD a higher volume of bone and periodontal ligament tissues was observed compared to EMD. After 5 months of healing, regenerated tissues presented quantitative differences from the pristine tissues. In the two modalities where GTR alone or combined with EMD was used, the regenerated tissues differed in quantity from the EMD-treated sites.

The impact of cigarette smoke inhalation on the outcome of enamel matrix derivative treatment in rats: histometric analysis

BACKGROUND

Tobacco use is the most significant risk factor of periodontal disease. Clinical evidence has demonstrated that tobacco may negatively influence the results after surgical and non-surgical periodontal therapy. Enamel matrix derivative (EMD) have been used in periodontal regenerative procedures resulting in improvement of clinical parameters. The effect of EMD in the presence of tobacco compounds is unclear. Thus, the aim of the present study is to evaluate the impact of cigarette smoke inhalation (CSI) on the results of EMD treatment.

METHODS

Twenty-two Wistar rats were assigned to two groups: Group 1, CSI (n = 11); Group 2, non-exposed (n = 11). Thirty days after initiation of CSI, fenestration defects were created at the buccal aspect of the first mandibular molar. The study followed a split-mouth design. After the surgeries the defects were randomly assigned to two subgroups: non-treated control and treated with EMD. The animals were sacrificed 21 days later and the percentage of defect fill, density of newly formed bone, and new cementum formation were histometrically assessed. The number of osteoclasts was determined by tartrate-resistant acid phosphatase.

RESULTS

CSI was associated with less bone density compared to the non-exposed group. EMD provided an increased defect fill and new cementum formation in both groups. The number of tartrate-resistant acid phosphatase-positive osteoclasts was significantly higher in the CSI non-treated control group compared to the non-treated control of the non-exposed animals.

CONCLUSIONS

EMD may provide increased defect fill and cementum formation in the presence or absence of CSI. However, tobacco smoke produced a detrimental effect on bone healing when density of newly formed bone was considered.

Experimental animal models in periodontology: a review

In periodontal research, animal studies are complementary to in vitro experiments prior to testing new treatments. Animal models should make possible the validation of hypotheses and prove the safety and efficacy of new regenerating approaches using biomaterials, growth factors or stem cells. A review of the literature was carried out by using electronic databases (PubMed, ISI Web of Science). Numerous animal models in different species such as rats, hamsters, rabbits, ferrets, canines and primates have been used for modeling human periodontal diseases and treatments. However, both the anatomy and physiopathology of animals are different from those of humans, making difficult the evaluation of new therapies. Experimental models have been developed in order to reproduce major periodontal diseases (gingivitis, periodontitis), their pathogenesis and to investigate new surgical techniques. The aim of this review is to define the most pertinent animal models for periodontal research depending on the hypothesis and expected results.

Histological characteristics of newly formed cementum in surgically created one-wall intrabony defects in a canine model

PURPOSE

Periodontal regenerative therapies for defects created by severe periodontitis are mainly focused on bone regeneration. Although cementum regeneration needs to be better understood, it is believed to play an important role in periodontal regeneration. The first step toward a full understanding of cementum regeneration is to compare repaired cementum to pristine cementum. This study, which used histological techniques, was designed to focus on cementum regeneration and to compare pristine cementum to repaired cementum after surgical procedures with 8 and 24 week healing periods in a canine model.

METHODS

Buccal and lingual mucoperiosteal flaps of 10 beagle dogs were surgically reflected to create critical-sized defects. Intrabony one-wall defects, of which dimension is 4 mm width and 5 mm depth, were made at the distal aspect of mandibular second premolars and the mesial aspect of mandibular fourth premolars in the right and left jaw quadrants. Animals were sacrificed after 8 and 24 weeks post-surgery for histological specimen preparation and histometric analysis.

RESULTS

The repaired cementum was composed mostly of acellular cementum and cellular mixed fiber cementum and was thicker in the apical area than in the coronal area. The acellular cementum of the supracrestal area appeared to be amorphous. The newly formed cellular cementum was partially detached from the underlying circumpulpal dentin, which implied a weak attachment between new cementum and dentin, and this split was observed to a lesser extent in the 24 week group than in the 8 week group. The vertical height of the repaired cementum was greater in the 24 week group than in the 8 week group.

CONCLUSIONS

Within the limitations of this study, we can conclude that repaired cementum after root planing was mainly acellular cementum and cementum tissue that matured to a shape similar to pristine cementum as the healing progressed from 8 to 24 weeks.

The effect of enamel matrix derivative (Emdogain) on bone formation: a systematic review

This systematic review focused on the question, if and to what extent enamel matrix derivative (Emdogain) [EMD]) promotes the regeneration of bone. The influence of combinations with other biomaterials was additionally evaluated. Twenty histomorphometric studies were included in this systematic review. Main results of the reviewed articles were (i) guide tissue regeneration (GTR) of infrabony defects seems to result in a higher degree of bone regeneration compared to treatment with EMD; (ii) combined therapy (GTR + EMD) of infrabony defects might not lead to better results than GTR therapy alone; (iii) there seems to be no additional benefit of combined therapy (GTR + EMD) in furcation defects over GTR therapy alone; (iv) EMD seems to lead to more bone regeneration of infrabony defects compared to open flap debridement; (v) however, EMD application might result in more bone formation when applied in supporting defects compared to nonsupporting defects; and (vi) EMD does not seem to promote external jaw/parietal bone formation in the titanium capsule model. The results of one study that suggest that EMD increases the initial growth of trabecular bone around endosseous implants by new bone induction need to be confirmed by additional research.

Pre-clinical models for oral and periodontal reconstructive therapies

The development of new medical formulations (NMF) for reconstructive therapies has considerably improved the available treatment options for individuals requiring periodontal repair or oral implant rehabilitation. Progress in tissue engineering and regenerative medicine modalities strongly depends on validated pre-clinical research. Pre-clinical testing has contributed to the recent approval of NMF such as GEM 21S and INFUSE bone grafts for periodontal and oral regenerative therapies. However, the selection of a suitable pre-clinical model for evaluation of the safety and efficacy of a NMF remains a challenge. This review is designed to serve as a primer to choose the appropriate pre-clinical models for the evaluation of NMF in situations requiring periodontal or oral reconstruction. Here, we summarize commonly used pre-clinical models and provide examples of screening and functional studies of NMF that can be translated into clinical use.

Stimulation of cytokines in osteoblasts cultured on enamel matrix derivative

OBJECTIVE

The purpose of this study was to evaluate the influence of enamel matrix derivative (EMD) on the release of transforming growth factor beta 1 (TGF-beta1), interleukin-6 (IL-6), insulin-like growth factor I (IGF-I), bone morphogenetic protein 2 (BMP-2), and osteoprotegerin (OPG) in human and mouse osteoblasts.

STUDY DESIGN

Human MG-63 and mouse MC3T3-E1 cells were seeded onto 6-well culture plates at an initial density of 5,000/cm(2) and grown in Dulbecco's eagle medium (DMEM) with 10% fetal bovine serum for 24 h. Then cells were cultured either with 100 microg/mL EMD added to DMEM or with DMEM only. After 2, 5, and 9 days' incubation the culture medium was collected and analyzed by enzyme-linked immunosorbent analysis. Data were analyzed using Student t test.

RESULTS

The EMD treatment significantly increased the production of IL-6 and TGF-beta1 (P < .05) at all time points. The release of OPG was also increased in mouse osteoblasts (P < .05). IGF-I and BMP-2 were not detected in both control and EMD-treated groups.

CONCLUSION

This study suggests that the stimulatory effects of EMD on tissue regeneration are mediated by the up-regulation of local mediators released by osteoblasts.

Regenerative approaches in the craniofacial region: manipulating cellular progenitors for oro-facial repair

This review aims to highlight the potential for regeneration that resides within the bony tissues of the craniofacial region. We examine the five main cues which determine osteogenic differentiation: heritage of the cell, mechanical cues, the influence of the matrix, growth factor stimulation and cell-to-cell contact. We review how successful clinical procedures, such as guided tissue regeneration and distraction osteogenesis exploit this resident ability. We explore the developmental origins of the flat bones of the skull to see how such programmes of differentiation may inform new therapies or regenerative techniques. Finally we compare and contrast existing approaches of hard tissue reconstruction with future approaches inspired by the regenerative medicine philosophy, with particular emphasis on the potential for using chondrocyte-inspired factors and replaceable scaffolds.

Efficacy of open flap debridement with and without enamel matrix derivatives in the treatment of mandibular degree II furcation involvement

The aim of the present study was the evaluation of the efficacy of open flap debridement (OFD) with and without enamel matrix derivatives (EMD) in the management of class II furcation involvement. Twenty similar bilateral class II furcation defects in ten healthy nonsmoker patients were selected. One defect in each subject was treated with OFD alone (OFD group) and the contralateral one with OFD and simultaneous application of enamel matrix derivatives (EMD group). Clinical probing depth, vertical clinical attachment level, horizontal clinical attachment level, and the location of the gingival margin, horizontal probing depth of bony defect (E-HPD), vertical depth of bone crest, vertical depth of the base of bony defect (V-DBD), and length of the intrabony defect were measured at baseline and during reentry surgery after 6 months. Wilcoxon signed-rank test and Mann-Whitney U test were used to analyze the data. Among soft tissue parameters, only horizontal attachment gain in EMD was significantly more than OFD (P = 0.002). Application of EMD significantly enhanced the horizontal (E-HPD) and vertical (V-DBD) resolution of the bony defect (P < 0.05). In conclusion, it seems that the adjunctive use of EMD enhances the efficiency of OFD in the management of mandibular class II furcation defects.

Favorable Periodontal Healing of 1-Wall Infrabony Defects After Application of Calcium Phosphate Cement Wall Alone or in Combination With Enamel Matrix Derivative: A Pilot Study With Canine Mandibles

BACKGROUND

Although various periodontal regenerative therapies are used, their effects on non-contained infrabony defects are unpredictable. Our previous studies showed that injectable, moldable, fast-setting calcium phosphate cement (CPC) promoted histocompatible periodontal healing in 3-wall intrabony defects. The present study evaluated healing patterns after surgical application of CPC walls with and without an enamel matrix derivative (EMD) in 1-wall infrabony defects in dogs.

METHODS

One-wall infrabony defects (5 x 5 x 4 mm) were created surgically on the mesial and distal sides of bilateral mandibular fourth premolars in four beagle dogs. After elevating a full-thickness flap, exposed root surfaces were planed thoroughly. The 16 defects were assigned randomly to one of the following experimental conditions: CPC, CPC+EMD, EMD, and open flap debridement (OFD). Ten weeks post-surgery, the animals were sacrificed, and histologic specimens were prepared for histomorphometric evaluation.

RESULTS

Defect sites treated with EMD only exhibited varying degrees of new cementum and new bone formation, whereas the OFD group presented only limited new cementum and bone formation. Defect sites where a CPC wall was implanted (CPC and CPC+EMD groups) revealed significantly greater regeneration of new bone and new cementum than in the EMD and OFD groups. No significant differences were observed between the CPC and CPC+EMD groups.

CONCLUSIONS

CPC walls with and without EMD promoted regeneration of alveolar bone and cementum in 1-wall infrabony defects. Space and stable wound healing are believed to be crucial for periodontal regeneration in non-contained infrabony defects.

Effect of two different approaches for root decontamination on new cementum formation following guided tissue regeneration: a histomorphometric study in dogs

BACKGROUND AND OBJECTIVE

The aim of the present study was to evaluate comparatively the effect of two different approaches for root decontamination on new cementum formation following guided tissue regeneration (GTR).

MATERIAL AND METHODS

Nine mongrel dogs were used to obtain bilateral chronic class III furcation defects by placing cotton ligatures around both third mandibular premolars. The teeth were randomly assigned to receive one of the following treatments: scaling and root planing, by means of hand and rotatory instruments, in order to remove soft and hard deposits as well as all root cementum (group A); or removal of only soft microbial deposits, by polishing the root surface with rubber cups and polishing paste, aiming for maximum root cementum preservation (group B). Both groups were treated with GTR, with the use of resorbable polyglycolic-lactic acid membranes (RESOLUT XT).

RESULTS

Four months later, data analysis showed that a superior length (mm) (3.59 +/- 1.67 and 6.20 +/- 2.26 for groups A and B, respectively; p = 0.004) and a thicker layer (microm) (18.89 +/- 9.47 and 52.29 +/- 22.48 for groups A and B, respectively; p = 0.001) of new cementum was achieved by keeping the root cementum in place during root decontamination (group B). Regardless of the treatment modality, the new cementum was predominantly of a reparative, cellular extrinsic and intrinsic fiber type.

CONCLUSION

Within the limits of the present study, it may be concluded that root cementum preservation may affect the new cementum formation following GTR in class III furcation defects, and the treatment modality did not influence the type of newly formed cementum.

The application of an enamel matrix protein derivative (Emdogain) in regenerative periodontal therapy: a review

Regenerative periodontal therapy aims at reconstitution of the lost periodontal structures such as new formation of root cementum, periodontal ligament and alveolar bone. Findings from basic research indicate that enamel matrix protein derivative (EMD) has a key role in periodontal wound healing. Histological results from animal and human studies have shown that treatment with EMD promotes periodontal regeneration. Moreover, clinical studies have indicated that treatment with EMD positively influences periodontal wound healing in humans. This review aims to present an overview of evidence-based clinical indications for regenerative therapy with EMD.

Emdogain-gel stimulates proliferation of odontoblasts and osteoblasts

OBJECTIVE

The purpose of this study was to determine whether a premixed form of enamel matrix derivative (EMD), Emdogain-gel, has the same property as the original formula of EMD in stimulating the proliferation of osteoblasts and odontoblasts.

STUDY DESIGN

Osteoblast cell line (MC3T3) and odontoblast cell line (MDPC) were cultured in the 6-well culture plates and treated in 4 different groups: (1) culture medium control, (2) 100 microg/mL Emdogain-gel directly added to the culture medium, (3) culture medium with a culture plate insert, and (4) 100 microg/mL Emdogain-gel added onto a culture plate insert. The culture plate insert prevented direct contact between Emdogain-gel and the cells. After 3-day incubation, cell morphology was examined and the total cell number per well was counted. Data were analyzed using 1-way ANOVA.

RESULTS

Emdogain-gel significantly increased cell number of both osteoblasts and odontoblasts regardless the presence of the culture plate insert.

CONCLUSION

Emdogain-gel stimulates cell proliferation of odontoblasts and osteoblasts. The direct contact between Emdogain-gel and cells is not required. Heat treatment of EMD and premix with propylene glycol alginate did not change its property of releasing bioactive molecules for promoting cell proliferation.

The structure of periodontal tissues formed following guided tissue regeneration therapy of intra-bony defects in the monkey

OBJECTIVE

To describe the periodontal tissues formed following guided tissue regeneration (GTR) therapy of intra-bony defects (IBD).

METHODS

Eight adult Macaca fascicularis monkeys were used. Proximal IBD were created at the mandibular second pre-molars and second molars. After 3 months, GTR surgery was performed. The animals were euthanized at 6 months and 2 years after surgery. Block biopsies were harvested, and prepared for histological analysis.

RESULTS

At 6 months the defect had healed with new cementum (NC), periodontal ligament (PDL) and bone. The NC seemed to be firmly anchored to the dentin. Supra-crestally, the NC consisted of a 10 microm thick layer of acellular extrinsic fibre cementum (AEFC). Sub-crestally, the NC was considerably thicker and consisted of an inner layer of AEFC and an outer thicker layer of cellular mixed fibre cementum (CMFC). The extrinsic fibre density amounted to about 10 fibres per 100 microm. The PDL was wider than the pristine PDL and widened in coronal direction. After 2 years of healing, the thickness of the NC in the sub-crestal compartment had increased by about 20 microm and the fibre density had increased by about 50%.

CONCLUSION

After 2 years of healing the structure of the regenerated tissues resembled that of pristine periodontal tissues.

The effect of enamel matrix proteins and deproteinized bovine bone mineral on heterotopic bone formation

To evaluate the osteoinductive potential of deproteinized bovine bone mineral (DBBM) and an enamel matrix derivative (EMD) in the muscle of rats. Sixteen rats were used in this study. The animals were divided in three groups. Group A: a pouch was created in one of the pectoralis profundis muscles of the thorax of the rats and DBBM particles (Bio-Oss) were placed into the pouch. Healing: 60 days. Group B: a small pouch was created on both pectoralis profundis muscles at each side of the thorax midline. In one side, a mixture of EMD (Emdogain) mixed with DBBM was placed into one of the pouches, whereas in the contralateral side of the thorax the pouch was implanted with DBBM mixed with the propylene glycol alginate (PGA--carrier for enamel matrix proteins of EMD). Healing: 60 days. Group C: the same procedure as group B, but with a healing period of 120 days. Qualitative histological analysis of the results was performed. At 60 days, the histological appearance of the DBBM particles implanted alone was similar to that of the particles implanted together with EMD or PGA at both 60 and 120 days. The DBBM particles were encapsulated into a connective tissue stroma and an inflammatory infiltrate. At 120 days, the DBBM particles implanted together with EMD or PGA exhibited the presence of resorption lacunae in some cases. Intramuscular bone formation was not encountered in any group. The implantation of DBBM particles alone, combined with EMD or its carrier (PGA) failed to exhibit extraskeletal, bone-inductive properties.

Effect of EDTA Root Conditioning on the Healing of Intrabony Defects Treated With an Enamel Matrix Protein Derivative

BACKGROUND

Regenerative periodontal therapy with an enamel matrix protein derivative (EMD) has been shown to promote regeneration in intrabony periodontal defects. However, in most clinical studies, root surface conditioning with EDTA was performed in conjunction with the application of EMD, and, therefore, it cannot be excluded that the results may also be attributable to the effect of the root conditioning procedure. The purpose of this study was to determine the effect of root conditioning on the healing of intrabony defects treated with EMD.

METHODS

Twenty-four patients, each of whom exhibited one deep intrabony defect, were randomly treated with either open flap debridement (OFD) followed by root surface conditioning with EDTA and application of EMD (OFD+EDTA+EMD) or with OFD and application of EMD only (OFD+EMD). The following parameters were recorded at baseline and at 1 year: plaque index (PI), gingival index (GI), bleeding on probing (BOP), probing depth (PD), and clinical attachment level (CAL).

RESULTS

No differences in any of the investigated parameters were observed at baseline between the two groups. Healing was uneventful in all patients. At 1 year after therapy, the OFD+EDTA+EMD group showed a reduction in mean PD from 9.3+/-1.3 mm to 4.0+/-0.9 mm (P<0.001), and mean CAL changed from 10.8+/-2.2 mm to 7.1+/-2.8 mm (P<0.001). In the OFD+EMD group, mean PD was reduced from 9.3+/-1.2 mm to 4.2+/-0.9 mm (P<0.001), and a change in mean CAL from 11.0+/-1.7 mm to 7.3+/-1.6 mm (P<0.001). There were no significant differences in any of the investigated parameters between the two groups.

CONCLUSION

In intrabony defects, regenerative surgery including OFD+EDTA+EMD failed to show statistically significant differences in terms of PD reduction and CAL gain compared to treatment with OFD+EMD.

Enamel matrix derivative alone or in combination with a bioactive glass in wide intrabony defects

This controlled clinical study investigated the clinical and radiographic outcome of wide intrabony periodontal defects treated by enamel matrix derivatives alone or in combination with a bioactive glass over a period of 8 months. Twenty-three chronic periodontitis patients, who received initial therapy and had radiographical interproximal defects with an associated probing depth of 6 mm or more and an intrabony component of at least 4 mm, were included. Each of the patients, contributing at least one intrabony defect, was treated with either enamel matrix derivative alone (group 1, n=10) or the combination (group 2, n=13). In both groups, all clinical and radiographical parameters were improved. Groups 1 and 2 presented a mean pocket reduction of 5.03+/-0.89 and 5.73+/-0.80 mm, recession of 0.97+/-0.24 and 0.56+/-0.18 mm, relative attachment gain of 4.06+/-1.06 and 5.17+/-0.85 mm, and radiographic bone gain of 2.15+/-0.42 and 2.76+/-0.69 mm, respectively. An intergroup comparison revealed significant differences for all of the parameters, yielding a more favorable outcome towards the combined approach. Within the limits of the study, both treatments resulted in marked clinical and radiographical improvements, but combined treatment seemed to enhance the results in the treatment of wide intrabony defects.

Moderate effect of enamel matrix derivative (Emdogain® Gel) on Porphyromonas gingivalis growth in vitro

OBJECTIVE

The aim of this study was to analyse the antibacterial effects of Emdogain Gel or its constituents on the growth of the suspected periodontopathogen Porphyromonas gingivalis.

STUDY DESIGN

The effects of the proteins of enamel matrix derivative (EMD), the commercial product Emdogain Gel or its vehicle propylene glycol alginate (PGA) (Straumann, Switzerland) on P. gingivalis growth were determined by two methods: broth dilution assay (BDA) and agar diffusion assay (ADA).

RESULTS

BDA-Emdogain Gel inhibited moderately the growth of P. gingivalis, whereas EMD showed no effect. The PGA vehicle inhibited the growth completely. ADA-Emdogain Gel resulted in some inhibition in growth but was not significantly different from control. EMD revealed no zone of inhibition. PGA demonstrated statistically significant zones of inhibition.

CONCLUSION

Emdogain Gel shows moderate antibacterial activities against P. gingivalis. These properties seem to be due to the PGA component of the gel preparation.

EDTA Gel Root Conditioning: Lack of Effect on Clinical and Radiographic Outcomes of Intrabony Defect Treatment With Enamel Matrix Derivative

BACKGROUND

The adjunctive use of enamel matrix derivative (EMD) in the surgical therapy of intrabony defects results in improved outcomes compared to surgical debridement alone. However, the role of EDTA root conditioning in EMD therapy has not been investigated. The purpose of this study was to compare the 12-month outcomes of EMD application with and without EDTA root conditioning in intrabony defect surgical therapy.

METHODS

Twenty-eight chronic periodontitis patients, each contributing a 2- or 3-wall intrabony defect (> or = 4 mm deep and > or = 2 mm wide), participated. Patients consecutively received surgical treatment with either EMD alone (first 13 patients) or EMD + EDTA (subsequent 15 patients). Probing depth (PD), clinical attachment level (CAL), and gingival margin position, i.e., recession (REC) were the clinical parameters recorded. Recorded radiographic parameters were the distances from 1) cemento-enamel junction to bone crest (CEJ to BC), 2) CEJ to base of the defect (CEJ to BD), and 3) BC to BD.

RESULTS

Intragroup analysis showed that both EMD alone and EMD + EDTA led to significant PD reduction, CAL gain, and REC increase 1 year postoperatively. Both groups had >60% mean radiographic defect resolution (change in BC to BD). None of the recorded parameters were significantly different between the two groups, either at baseline or postoperatively.

CONCLUSIONS

These results suggest that clinical and radiographic outcomes of intrabony defect EMD therapy do not depend on the use of EDTA gel root conditioning. The potential contribution of EDTA gel root conditioning to the histological outcomes reported with EMD therapy remains to be determined.

Periodontal wound healing following GTR therapy of dehiscence-type defects in the monkey: short-, medium- and long-term healing

OBJECTIVE

To describe periodontal wound healing in dehiscence-type defects following guided tissue re-generation (GTR) therapy.

METHODS

Ten adult Macaca fascicularis monkeys were used. Buccal dehiscence-type defects were created at the maxillary second pre-molars and second molars. After 3 months, GTR surgery was performed. The animals were euthanized at 6 weeks, 6 months and 2 years after surgery. Block biopsies were harvested, and prepared for histological analysis.

RESULTS

A new attachment apparatus was structured already after 6 weeks of healing. A 10-20 microm thin layer of acellular extrinsic fibre cementum (AEFC) had formed along the instrumented root surface. At 6 months, the thickness of the supracrestal cementum was comparable with that at 6 weeks, while the thickness of the subcrestal cementum had increased to 40-60 microm. In this zone, the cementum consisted of an inner layer of AEFC attached to the circum-pulpal dentin and an outer layer of cellular mixed fibre cementum (CMFC). The numerical extrinsic fibre density was twice that at 6 weeks. At 2 years, the periodontal tissues resembled the pristine periodontium.

CONCLUSION

Periodontal healing following GTR therapy of recession-type defects will result in a restitutio ad integrum, i.e. healing by re-generation. A continuous maturation process occurs over at least 2 years.

Bone formation by enamel matrix proteins and xenografts: an experimental study in the rat ramus

The aim of this study was to evaluate whether the use of enamel matrix proteins with or without the use of deproteinized bovine bone influences bone formation when used as an adjunct to guided bone regeneration (GBR). Twenty rats, divided into four groups of five animals each, were used in this study. Group A1: A hemispherical PTFE capsule was placed empty on the lateral aspect of the mandibular ramus (GBR). At the contralateral side of the jaw, the capsule was filled with an enamel matrix derivative (EMD) before its placement. The healing period was 60 days. Group A2: The animals were treated in the same manner as in Group A1 but with a healing period of 120 days. Group B1: The animals were treated in the same manner as in Group A1 with the difference that deproteinized bovine bone mineral (DBBM) particles were packed in the capsule. At the contralateral side of the jaw, the capsule was filled with a mixture of EMD and DBBM. The healing period was 60 days. Group B2: The same treatment as in B1 but with a healing period of 120 days. The histological analysis revealed that in Groups A1 and A2 newly formed bone was covering a significant part of the empty capsules (GBR). The use of EMD in the capsule did not offer any added benefit to the use of the capsule alone in terms of new bone formation. At Groups B1 and B2, the presence of DBBM and/or EMD did not positively affect the amount of new bone formation. It can be suggested that neither the application of EMD nor the use of DBBM or the combination of EMD and DBBM results in enhanced amounts of bone formation in comparison with the GBR procedure alone.

Effects of enamel matrix proteins on tissue formation along the roots of human teeth

OBJECTIVE

Enamel matrix-derived proteins (EMD) are thought to trigger the formation of acellular extrinsic fibre cementum (AEFC), while other reports indicate that EMD may have osteogenic potential. The aim of the present study was to characterize the tissues developing on the root surface following application of EMD.

METHODS

Twelve human periodontitis-affected teeth, scheduled for extraction, were treated with EMD. Two to 6 weeks later, the teeth were extracted, demineralized and processed for embedding in acrylic and epoxy resins. New tissue formation was analysed by light and transmission electron microscopy.

RESULTS

New tissue formation on the root was observed in the notch and on both scaled and unscaled root surfaces distant of the notch area in six defects. The newly formed tissues on the root were thick, collagenous, devoid of extrinsic fibres, and had an irregular surface contour. The presence of electron-dense, organic material in the collagenous matrix indicated at least partial mineralization. Embedded cells were numerous and the cells on the matrix surface were very large in size. Abundant rough endoplasmic reticulum and a prominent Golgi complex were evident. The presence of a split between the treated root surfaces and the newly formed tissue was a common observation, as was the presence of bacteria and host cells in the interfacial gap.

CONCLUSION

Following treatment with EMD, a bone-like tissue resembling cellular intrinsic fibre cementum may develop on the root surfaces, instead of AEFC. Furthermore, EMD may both induce de novo formation of a mineralized connective tissue on scaled root surfaces and stimulate matrix deposition on old native cementum. Interfacial bonding appeared to be weak after 6 weeks of healing.

Apatite formed on/in agarose gel as a bone-grafting material in the treatment of periodontal infrabony defect

The present study was designed to evaluate the effects of a hydroxyapatite/agarose (HA/agarose) composite gel formed by a novel alternate soaking process for the treatment of periodontal infrabony defects in three dogs. After creating two-wall infrabony periodontal defects on the medial aspect of the maxillary and mandibular second and forth premolars, the defects were implanted with temporary dental filling material (stopping) to induce inflammatory periodontal disease. Two months later, the mucoperiosteal flaps were raised, and after debridement, the infrabony defects were filled with one of the following three materials: (a) HA/agarose, (b) Bone ject (True-Bone Ceramic-collagen combined bone graft material, Koken, Japan), or (c) no material implantation (negative control). The animals were then randomly scheduled for sacrifice at 1, 2, and 6 months, and samples were taken for histological examination. In the HA/agarose gels, the 2-month postoperative cavities exhibited regeneration to new attachments with the apposition of a new cementum and well-oriented fibers. The neocementum was narrow and acellular, and the new bone apposition was limited. Six months postoperatively, newly formed bone was predominantly observed. The neocementum was wider and cellular. In the negative control, the 2-month postoperative cavities exhibited no regeneration of the cementum, nor any formation of periodontal pockets. The six-month postoperative cavities were nearly the same as the 2-month cavities. The Bone ject, 2-month postoperative cavities exhibited no regeneration of the periodontal tissue, nor any formation of periodontal pockets. Six months postoperatively, inflammatory granulation tissue was observed around the particles. The present study suggests that HA/agarose gels may play an important role in the regeneration of lost periodontal tissue.