Specific issues in clinical trials on the use of barrier membranes in periodontal regeneration

Selection of Collagen Membranes for Bone Regeneration: A Literature Review

Several treatment modalities have been proposed to regenerate bone, including guided bone regeneration (GBR) where barrier membranes play an important role by isolating soft tissue and allowing bone to grow. Not all membranes biologically behave the same way, as they differ from their origin and structure, with reflections on their mechanical properties and on their clinical performance. Collagen membranes have been widely used in medicine and dentistry, because of their high biocompatibility and capability of promoting wound healing. Recently, collagen membranes have been applied in guided bone regeneration with comparable outcomes to non-resorbable membranes. Aim of this work is to provide a review on the main features, application, outcomes, and clinical employment of the different types of collagen membranes. Comparisons with non-resorbable membranes are clarified, characteristics of cross-linked collagen versus native collagen, use of different grafting materials and need for membrane fixation are explored in order to gain awareness of the indications and limits and to be able to choose the right membrane required by the clinical condition.

Clinical and radiographical evaluation of a bioresorbable collagen membrane of fish origin in the treatment of periodontal intrabony defects: A preliminary study

BACKGROUND

Recently, there has been interest in non-mammalian collagen sources such as fish collagen in periodontal regeneration. In the present study, collagen barrier membrane of fish origin was assessed in the treatment of periodontal intrabony defects.

MATERIALS AND METHODS

Ten systemically healthy chronic periodontitis patients having a paired osseous defect in the mandibular posterior teeth were selected and randomly assigned to receive a collagen membrane (test) or open flap debridement (control) in a split mouth design. Clinical parameters such as Plaque index, Gingival bleeding index, Probing pocket depth, Relative attachment level, and Recession were recorded at baseline, 3, 6, and at 9 months, while radiographic evaluation was done to assess alveolar crestal bone level and percentage of defect fill at 6 and 9 months using autoCAD 2007 software. Student's t test (two-tailed, dependent) was used to find the significance of study parameters on continuous scale. Significance was set at 5% level of significance. Wilcoxon signed rank test was used to find the significance of percentage change of defect fill.

RESULTS

The comparison between the two groups did not show any statistically significant differences in the parameters assessed (P > 0.05) but, within each group, clinical parameters showed statistically significant differences from baseline to 9 months (P < 0.05).

CONCLUSION

Within the limits of the study, it can be inferred that no significant differences were found either by using collagen membrane of fish origin or open flap debridement in the treatment of periodontal intrabony defects.

Evaluation of a bioresorbable collagen membrane of fish origin in the treatment of periodontal intrabony defects: A prospective clinical study

BACKGROUND

Recently, there has been interest in non-mammalian collagen sources such as fish collagen in the development of biomatrices and scaffolds for periodontal regeneration. In the present study, a novel collagen barrier membrane of fish origin was assessed in the treatment of periodontal intra-bony defects.

MATERIALS AND METHODS

Ten systemically healthy chronic periodontitis patients having an osseous defect in the mandibular posterior teeth were selected and following the open flap debridement, a collagen membrane was placed over the defect and the flap was sutured with interrupted sutures. Clinical parameters such as Plaque Index, Gingival Bleeding Index, probing pocket depth (PPD), relative attachment level (RAL), and recession (R) were recorded at baseline, 6 and 9 months, whereas radiographic evaluation was done to assess alveolar crestal bone level and defect depth fill at 6 and 9 months using Auto-computer aided design (ACAD) 2007 software. Statistical significance was set at 5% level of significance.

RESULTS

There was statistical significant differences with respect to periodontal clinical parameters such as Plaque Index, Gingival Bleeding Index, PPD, RAL, and gingival recession assessed at baseline, at 6 and 9 months respectively (P < 0.05), and radiographic evaluation showed a defect fill of 58.62 median % at 9 months.

CONCLUSION

This preliminary study has shown predictable results in using fish collagen membrane, for treating periodontal intra-bony defects. Further, long-term clinical trials are needed to validate the effectiveness of this membrane.

Prostanoid- and interleukin-1-induced primary genes in cementoblastic cells

BACKGROUND

Cementum is a key component of a functional periodontal organ. However, regenerating lost cementum is difficult and often incomplete. Identifying molecular mediators of cementoblast differentiation and function should lead to better targeted treatment for periodontitis. Prostaglandins increase mineralization of murine cementoblastic OCCM cells and alveolar bone formation, whereas the cytokine interleukin-1 (IL-1) inhibits alveolar bone formation. We hypothesized that differentially induced primary genes in OCCM cells may mediate anabolic and catabolic responses. Our objective was to identify primary genes differentially induced by the synthetic prostanoid fluprostenol and IL-1 in cementoblastic cells.

METHODS

Confluent OCCM cells were pretreated with the protein synthesis inhibitor cycloheximide followed by fluprostenol or IL-1 for 1.5 hours. cDNA generated from each group was used for cDNA subtraction hybridization to identify differentially induced genes. Preferential gene induction was verified by Northern blot analysis.

RESULTS

Thirteen fluprostenol- and seven IL-1-regulated genes were identified. Among the fluprostenol-induced genes was mitogen-activated protein (MAP) kinase phosphatase 1 (MKP1), a negative regulator of MAP kinase signaling. To verify the cDNA subtraction hybridization results, OCCM cells were treated with fluprostenol or prostaglandin F2 (PGF2), and MKP1 mRNA levels were determined. The 0.001 to 1 microM fluprostenol and 0.01 to 1 microM PGF2 significantly induced MKP1 mRNA levels, which peaked at 1 hour of treatment and returned to baseline at 2 hours.

CONCLUSIONS

Fluprostenol enhanced, whereas IL-1 inhibited, OCCM mineralization. Using cDNA subtraction hybridization, we identified primary genes that correlate with the observed anabolic and catabolic responses. These findings further our understanding of cementoblast function and suggest that differentially induced genes may mediate cementum formation and resorption.

Guided Tissue Regeneration Using A Bioabsorbable Membrane: A 21-Case Series

BACKGROUND

The purpose of this paper is to demonstrate how a bioabsorbable membrane in the treatment of intrabony defects, combined with appropriate case selection, produces a significant improvement in the clinical assessment of affected teeth. This study demonstrates success in 21 successive cases.

METHODS

Consecutive patients presenting advanced intrabony defects (8 to 15 mm) meeting the predetermined criteria were treated by guided tissue regeneration (GTR) with flap debridement and placement of a bioabsorbable copolymer membrane. To evaluate treatment predictability in a variety of patients, only one defect per patient was included in the study. Twenty-one patients completed the study, which included baseline measurement and subsequent surgical reentry of the treated site 9 to 18 months postoperatively. Selection of lesions was made following debridement of the defect; i.e., a membrane was placed only after determining that a lesion was a proper candidate for this procedure. Measurements from the cemento-enamel junction (CEJ) to the deepest apical aspect of the defects were made and documented with photographs. At the time of reentry, defect depths were again measured from the CEJ to the deepest apical point along with measurements of the residual 3-walled component of the defect, and photographs were taken. The re-entry procedure involved an apically positioned and occasionally minor osteoplasty to reduce residual probing depth, when present. Radiographs were taken at baseline and reentry.

RESULTS

The initial mean defect depth, as measured from the CEJ to the base of the lesion, was 10.2 mm. The mean defect depth at the time of reentry was 5 mm. The mean gain in vertical bone fill was 5.2 mm. Perhaps more significantly, in 20 of 21 cases, there was vertical fill to within 1 mm of the 3-walled component of the residual defect.

CONCLUSION

When appropriate case selection and management are applied, the use of bioabsorbable membranes does provide for consistent and predictable bone fill, producing clinically relevant reduction in vertical defect depth.

Healing of periodontal defects treated with enamel matrix proteins and root surface conditioning—an experimental study in dogs

Application of enamel matrix proteins has been introduced as an alternative method for periodontal regenerative therapy. It is claimed that this approach provides periodontal regeneration by a biological approach, i.e. creating a matrix on the root surfaces that promotes cementum, periodontal ligament (PDL) and alveolar bone regeneration, thus mimicking the events occurring during tooth development. Although there have been numerous in vitro and in vivo studies demonstrating periodontal regeneration, acellular cementum formation and clinical outcomes via enamel matrix proteins usage, their effects on the healing pattern of soft and hard periodontal tissues are not well-established and compared with root conditioning alone. In the present study, the effects of Emdogain (Biora, Malmö, Sweden), an enamel matrix derivative mainly composed of enamel matrix proteins (test), on periodontal wound healing were evaluated and compared with root surface conditioning (performed with 36% orthophosphoric acid) alone (control) histopathologically and histomorphometrically by means of the soft and hard tissue profile of periodontium. An experimental periodontitis model performed at premolar teeth of four dogs were used in the study and the healing pattern of periodontal tissues was evaluated at days 7, 14, 21, 28 (one dog at each day), respectively. At day 7, soft tissue attachment evaluated by means of connective tissue and/or epithelial attachment to the root surfaces revealed higher connective tissue attachment rate in the test group and the amount of new connective tissue proliferation in the test group was significantly greater than the control group (p<0.01). New bone formation by osteoconduction initiated at day 14 in the test and control group. At day 21, the orientation of supra-alveolar and PDL fibers established, and new cementum formation observed in both groups. At day 28, although regenerated cementum was cellular in all of the roots in the control samples, an acellular type of cementum (1.32+/-0.83 mm in length and 3.16+/-0.23 microm in width) was also noted in six roots of test samples with an inconsistent distribution on the root surfaces. The amount of new cementum was significantly higher in the test group than the control group samples (p<0.01). The width of the cellular cementum in the control group was more than the cellular cementum in the test group, but the difference was not statistically significant (p>0.05). A firm attachment of acellular cementum to the root dentin with functional organization of its collagen fibers was noted, and, the accumulation and organization of cellular cementum in the control group was more irregular than the cellular cementum formed in the test group. The amount of new bone was 2.41+/-0.75 mm in the test and 1.09+/-0.46 mm in the control group at day 28. The rate of bone maturation (the number of osteons) was found higher in the test group (10.75+/-0.85) than the control group (5.50+/-0.86). Under the limitations of the study, our results reveal that when compared with root surface conditioning, enamel matrix proteins have more capacity for stimulating periodontal regeneration via their positive effects on root surfaces, i.e. inhibition of gingival epithelium down growth and stimulation of connective tissue proliferation and attachment to the root surfaces during wound healing. An acellular type of cementum regeneration and new alveolar bone formation by an accelerated osteoconductive mechanism are also achieved with application of enamel matrix proteins.

In vitro wound healing responses to enamel matrix derivative

BACKGROUND

Enamel matrix derivative (EMD) contains a variety of hydrophobic enamel matrix proteins and is extracted from developing embryonal enamel of porcine origin. EMD has been associated with the formation of acellular cementum and it has been found to stimulate periodontal regeneration. The present study was established to investigate the influence of EMD on human periodontal ligament (PDL) cells, gingival fibroblasts (GF), and osteosarcoma (MG-63) cells on wound-fill rates using an in vitro wound model.

METHODS

Wounds were created by making 3 mm incisions in cell monolayers across the length of tissue culture plates. The wounded PDL, GF, and MG-63 cell monolayers were treated with media containing EMD over a concentration range of 5 to 100 microg/ml, platelet-derived growth factor (PDGF-BB) at 20 ng/ml as a positive control and insulin-like growth factor (IGF-I) at 100 ng/ml as a negative control. PDL cell wounded monolayers also were treated in EMD coated tissue culture plates. After an incubation period (up to 9 days), the cells were fixed and stained and cellular fill was measured across the width of the wound by computer-assisted histomorphometry.

RESULTS

When PDL, GF, and MG-63 cells were exposed to EMD in culture medium, an enhanced wound-fill was observed for all cells compared to untreated conditions. At early time points, PDL wound-fill rates in the presence of EMD were statistically greater than the rates of GF and MG-63 treated with EMD (P<0.001). There were no significant differences in wound-fill rates of PDL cells treated with EMD in medium versus EMD coated on culture plates. At days 3 and 6 post-wounding, PDL cells showed a significantly greater response to EMD than to PDGF-BB (P <0.001). EMD also had a greater effect on GF wound-fill rates than PDGF-BB at days 6 and 9. MG-63 cells were less responsive to PDGF-BB and EMD than PDL cells and GF. All 3 cell types treated with IGF-I showed no significant increase of wound-fill rates.

CONCLUSION

The present data support the concept that clinical application of enamel matrix derivative may enhance periodontal wound regeneration by specifically modifying periodontal ligament cell proliferation and migration.

Acceptance Program Guidelines. Products designed to regenerate periodontal tissues. Council on Scientific Affairs. American Dental Association

SCOPE

These Guidelines apply to products used to promote the regeneration of periodontal tissues lost due to periodontal diseases or other causes. Periodontal regeneration is defined histologically as regeneration of the tooth's supporting tissues, including alveolar bone, periodontal ligament, and cementum over a previously diseased root surface. Regenerative procedures must enhance the formation of a new attachment apparatus demonstrated by randomized controlled histological studies in animals, verified by human histologic evidence, and supported by beneficial results in human randomized controlled clinical trials.