The use of collagen membranes to guide regeneration of new connective tissue attachment in dogs

Characterization and biocompatibility of a bilayer PEEK-based scaffold for guiding bone regeneration

BACKGROUND

Polyetheretherketone (PEEK) is well known for its excellent physical-chemical properties and biosafety. The study aimed to open up a new method for clinical application of PEEK to reconstruct large-scale bone defects.

METHODS

A bilayer scaffold for bone regeneration was prepared by combining a sulfonated PEEK barrier framework (SPEEK) with a hydrogel layer loaded with aspirin (ASA) and nano-hydroxyapatite (nHAP) by the wet-bonding of Polydopamine (PDA).

RESULTS

The hydrogel was successfully adhered to the surface of SPEEK, resulting in significant changes including the introduction of bioactive groups, improved hydrophilicity, and altered surface morphology. Subsequent tests confirmed that the bilayer scaffold exhibited enhanced compression resistance and mechanical compatibility with bone compared to a single hydrogel scaffold. Additionally, the bilayer scaffold showed stable and reliable bonding properties, as well as excellent biosafety verified by cell proliferation and viability experiments using mouse embryo osteoblast precursor (MC3T3-E1) cells.

CONCLUSION

The bilayer bone regeneration scaffold prepared in this study showed promising potential in clinical application for bone regeneration.

3D-printed bi-layered polymer/hydrogel construct for interfacial tissue regeneration in a canine model

OBJECTIVES

There are complications in applying regenerative strategies at the interface of hard and soft tissues due to the limited designs of constructs that can accommodate different cell types in different sites. The problem originates from the challenges in the adhesion of dissimilar materials, such as polymers and hydrogels, that can be suitable for regenerating different tissues such as bone and soft tissues. This paper presents a design of a new hybrid construct in which a polymer (polycaprolactone (PCL)) membrane firmly adheres to a layer of hydrogen (gelatin).

METHODS

PCL membranes with defined size and porosity were fabricated using 3D printing. The gelatin layer was attached to the PCL membranes using the aminolysis procedure. We have examined this construct for the application of Guided Bone Regeneration (GBR) as a typical surgical regenerative procedure of the oral cavity at the interface of bone and soft tissue. Complete in vitro and in vivo investigations on canine tibia bone defects have been performed. Histological analyses for fibrosis morphometric and bone morphometric evaluation, as well as bone-fibrosis histological grading and CBCT imaging, were conducted.

RESULTS

Chemical and morphological studies of the membrane proved that gelatin was uniformly attached to the aminolyzed PCL membranes. The in vitro and in vivo studies indicated the membrane's biocompatibility, mechanical stability, and barrier function for the GBR application. Furthermore, in vitro study showed that the membranes could improve osteogenesis and the regeneration of bone defects. The results illustrated that the mean bone density in the membrane groups was about three times more than that of the control group.

SIGNIFICANCE

The fabricated 3D-printed hybrid Gelatin/PCL bi-layered membrane can be a good candidate for interfacial tissue engineering and a promising membrane for GBR procedure.

Structure, Barrier Function, and Bioactivity of Platelet-Rich Fibrin Following Thermal Processing

Platelet-rich fibrin (PRF) has been utilized as a substitute for resorbable membranes during guided bone regeneration therapy as it is a more bioactive biomaterial with living cells and growth factors than resorbable membranes. Nevertheless, PRF poses obvious disadvantages in its mechanical strength since its rapid degradability has been shown to typically resorb within a 2-week time period. In the present study, the barrier function and biological and mechanical properties of PRF were investigated both as standard therapy and after thermal processing. Two heating processes were applied: both single-side heating and double-side heating at 90°C for 10 s using a metal plate heater. The appearance and weight of PRF membranes were documented after heating, along with their morphological and mechanical properties evaluated by scanning electron microscope and tensile strength tests. The viability of cells found within PRF membranes was also evaluated using live/dead cell viability and CCK-8 (cell counting kit-8) assays. To comprehensively evaluate the barrier function of PRF membranes, Hoechst staining of human gingival fibroblasts, which can be distinguished from cells within the PRF membrane by emitting blue light at an excitation wavelength of 488 nm, was seeded onto the surface of PRF membranes. Furthermore, osteoblasts were cultured with extracts from different PRF groups to evaluate the biocompatibility of PRF membranes. The degradation rate of PRF membranes was examined by digestion assay. Compared with the nonheated PRF control, the size and weight of PRF membranes led to a significant decrease with a denser PRF microstructure following heating. In summary, the double-sided heating of PRF membranes not only demonstrated an improvement in mechanical and degradation properties but also led to a decrease in cell viability and proliferation.

Is the Bacterial Cellulose Membrane Feasible for Osteopromotive Property?

Guided bone regeneration was studied to establish protocols and develop new biomaterials that revealed satisfactory results. The present study aimed to comparatively evaluate the efficiency of the bacterial cellulose membrane (Nanoskin^®) and collagen membrane Bio-Gide^® in the bone repair of 8-mm critical size defects in rat calvaria. Seventy-two adult male rats were divided into three experimental groups (n = 24): the CG—membrane-free control group (only blood clot, negative control), BG—porcine collagen membrane group (Bio-Guide^®, positive control), and BC—bacterial cellulose membrane group (experimental group). The comparison periods were 7, 15, 30, and 60 days postoperatively. Histological, histometric, and immunohistochemical analyses were performed. The quantitative data were subjected to 2-way ANOVA and Tukey’s post-test, and p < 0.05 was considered significant. At 30 and 60 days postoperatively, the BG group showed more healing of the surgical wound than the other groups, with a high amount of newly formed bone (p < 0.001), while the BC group showed mature connective tissue filling the defect. The inflammatory cell count at postoperative days 7 and 15 was higher in the BC group than in the BG group (Tukey’s test, p = 0.006). At postoperative days 30 and 60, the area of new bone formed was greater in the BG group than in the other groups (p < 0.001). Immunohistochemical analysis showed moderate and intense immunolabeling of osteocalcin and osteopontin at postoperative day 60 in the BG and BC groups. Thus, despite the promising application of the BC membrane in soft-tissue repair, it did not induce bone repair in rat calvaria.

Bone-conditioned medium modulates the osteoconductive properties of collagen membranes in a rat calvaria defect model

OBJECTIVES

Collagen membranes are not limited to be occlusive barriers as they actively support bone regeneration. However, the impact of bone-derived growth factors on their osteoconductive competence has not been examined.

METHODS

Twenty adult Sprague Dawley rats were included in the study. Calvaria defects with a diameter of five millimeter were created. The defect was covered with one layer of a collagen membrane previously soaked in conditioned medium of porcine bone chips or in culture medium alone. After 4 weeks, microcomputed tomography was performed. Undecalcified thin-ground sections were subjected to light and scanning electron microscopy. Primary outcome parameter was the bone volume in the defect. Unit of analysis was the bone-conditioned medium (BCM).

RESULTS

In the central defect area of the control and the BCM group, median new bone connected to the host bone was 0.54 and 0.32 mm³, respectively (p = .10). In the ectocranial defect area, the control group showed significantly more bone than the BCM group (0.90 and 0.26 mm³; p = .02). Based on an exploratory interpretation, the control group had smaller bony islands than the BCM group. Scanning electron microscopy and histology indicate the formation of bone but also the collagen membrane to be mineralized in the defect site.

CONCLUSIONS

These results demonstrate that the commercial collagen membrane holds an osteoconductive competence in a rat calvaria defect model. Soaking collagen membranes with BCM shifts bone formation toward the formation of bony islands rather than new bone connected to the host bone.

Comparative efficacy of placental membrane and Healiguide™ in treatment of gingival recession using guided tissue regeneration

Background

Guided tissue regeneration-based root coverage has emerged as a promising treatment modality in the treatment of gingival recession. A variety of nonresorbable and bioresorbable membranes have been successfully used. Among resorbable membranes, collagen has been extensively studied. Recently, a third generation barrier membrane derived from placenta has been introduced for periodontal regeneration.

Aim

The objective of the present study is to clinically compare the efficacy of placental membrane (Amnion) and collagen membrane (Healiguide) for the treatment of gingival recession.

Materials and Methods

Twelve patients having isolated bilateral gingival recession defects were included in the study and were divided into two groups randomly. Group I were treated by coronally positioned flap and amnion membrane and Group II were treated by coronally positioned flap and collagen membrane (Healiguide)™. Clinical parameters, including dental plaque index (PI), gingival index (GI), gingival recession depth, probing pocket depth, clinical attachment level, and gingival biotype, were recorded before surgery at baseline and then reevaluated at 3 and 6 months postoperatively.

Statistical Analysis

Nonparametric test, i.e., Wilcoxon Signed-Ranks Test was used in the present study. Significance was reported at 95% confidence level.

Results

The results of the present study revealed statistically no significant difference (P > 0.05) in dental PI improved, GI and probing pocket depth in both groups. Significant reduction in gingival recession defects and gain in clinical attachment level was observed in both the groups. Intergroup comparison of gingival recession defects and clinical attachment level yielded nonsignificant differences. However, a statistically significant increase (P < 0.05) in gingival tissue thickness was observed in Group II as compared to Group I.

Conclusion

Both membranes are equally efficacious in the treatment of gingival recession. More gingival tissue thickness (gingival biotype) enhancement was observed in sites treated with collagen membrane.

The heat-compression technique for the conversion of platelet-rich fibrin preparation to a barrier membrane with a reduced rate of biodegradation

Platelet-rich fibrin (PRF) was developed as an advanced form of platelet-rich plasma to eliminate xenofactors, such as bovine thrombin, and it is mainly used as a source of growth factor for tissue regeneration. Furthermore, although a minor application, PRF in a compressed membrane-like form has also been used as a substitute for commercially available barrier membranes in guided-tissue regeneration (GTR) treatment. However, the PRF membrane is resorbed within 2 weeks or less at implantation sites; therefore, it can barely maintain sufficient space for bone regeneration. In this study, we developed and optimized a heat-compression technique and tested the feasibility of the resulting PRF membrane. Freshly prepared human PRF was first compressed with dry gauze and subsequently with a hot iron. Biodegradability was microscopically examined in vitro by treatment with plasmin at 37°C or in vivo by subcutaneous implantation in nude mice. Compared with the control gauze-compressed PRF, the heat-compressed PRF appeared plasmin-resistant and remained stable for longer than 10 days in vitro. Additionally, in animal implantation studies, the heat-compressed PRF was observed at least for 3 weeks postimplantation in vivo whereas the control PRF was completely resorbed within 2 weeks. Therefore, these findings suggest that the heat-compression technique reduces the rate of biodegradation of the PRF membrane without sacrificing its biocompatibility and that the heat-compressed PRF membrane easily could be prepared at chair-side and applied as a barrier membrane in the GTR treatment.

Ridge preservation for implant therapy: a review of the literature

Healing of the extraction socket after tooth removal involves retention of the blood clot followed by a sequence of events that lead to changes in the alveolar process in a three dimensional fashion. This normal healing event results in a minimal loss of vertical height (around 1 mm), but a substantial loss of width in the buccal-lingual plane (4-6 mm). During the first three months following extraction that loss has been shown to be significant and may result in both a hard tissue and soft tissue deformity affecting the ability to restore the site with acceptable esthetics. Procedures that reduce the resorptive process have been shown to be predictable and potentially capable of eliminating secondary surgery for site preparation when implant therapy is planned. The key element is prior planning by the dental therapist to act at the time of extraction to prevent the collapse of the ridge due to the loss of the alveolus. Several techniques have been employed as ridge preservation procedures involving the use of bone grafts, barrier membranes and biologics to provide a better restorative outcome. This review will explore the evidence behind each technique and their efficacy in accomplishing site preparation. The literature does not identify a single technique as superior to others; however, all accepted therapeutic procedures for ridge preservation have been shown to be more effective than blood clot alone in randomized controlled studies.

Evaluation of relative efficacy of β-tricalcium phosphate with and without type I resorbable collagen membrane in periodontal infrabony defects: a clinical and radiographic study

BACKGROUND AND OBJECTIVES

To compare clinically and radiographically, the regenerative potential of a β-tricalcium phosphate bone graft, Cerasorb(®) with and without a bioresorbable type I collagen membrane, BioMend Extend™, in treating periodontal infrabony osseous defects.

MATERIALS AND METHODS

A total of 20 sites from 10 patients showing bilateral infrabony defects were selected and selected sites were randomly divided into experimental site A (Cerasorb(®)) and experimental site B (Cerasorb(®) and BioMend Extend™) by using split mouth design. The clinical parameters like plaque index, gingival index, probing pocket depth, clinical attachment level and gingival recession were recorded at baseline, 6 weeks, 3, 6 and 9 months. Radiographic evaluation (Linear CADIA) at 6 and 9 months; and intrasurgical measurements at baseline and 9 months were carried out to evaluate the defect fill, change in alveolar crest height and defect resolution.

RESULTS

Significant reduction in all clinical parameters was observed in both the groups. On comparison no statistical significance was observed between the two groups. Radiographically, in site A there was significant defect fill of 78.4 and 97.2% at 6 and 9 months respectively. Whereas in site B reduction was 78.4 and 97.2% at 6 and 9 months respectively. After surgical re-entry, there was significant defect fill of 89.2 and 74% in both groups.

INTERPRETATION AND CONCLUSION

Individually both the graft and membrane have shown promising results in the management of periodontal intrabony defects. But the added benefit by combining Cerasorb(®) with BioMend Extend™ was not observed statistically in both clinical radiographic findings.

FABRICATION AND EVALUATION OF CHITOSAN MEMBRANES FOR GUIDED TISSUE REGENERATION

Chitosan membranes were prepared by a thermal induced phase separation method, following treatment with nontoxic NaOH gelating and Na5P3O10, Na5SO3 crosslinking agents. Effects of these reaction agents on chitosan membranes were evaluated to survey the feasibility of using these membranes in guided tissue regeneration (GTR) application. The preliminary results showed chitosan membranes crosslinked with Na5P3O10 and Na2SO3 had gel content of 53.5% and 52.2%r, respectively. Contrarily, the chitosan matrix gelated with NaOH dissolved completely during gel content measurement. Chitosan membrane treated with Na5P3O10 had lowest elastic modulus of 12.9 Mpa as compared with other membranes treated with Na2SO3 (17.9Mpa) and NaOH(23.6Mpa). From SEM observations, NaOH gelated chitosan membrane had the smoothest surface morphology than others. However, Na5P3O10 crosslinked chitosan membrane had better cell adhesion and proliferation results in cell culture test. All three chitosan membranes degraded by about 23%∼28% of initial weight after a 90-day in vitro shaking test.

Recession defects associated with scraped roots treated with subepithelial connective tissue graft

The objective of the current study was to assess histomorphometrically the healing process of recession defects associated with scraped roots treated with subepithelial connective tissue graft (SCTG). Six dogs were used. Bone dehiscence defects (6 × 8 mm) and root planing were carried out on maxillary canine teeth. Following a split-mouth model, according to the treatment, left canines (control) were covered with coronally positioned flap (CPF). Right canines were submitted to treatments with SCTG. After a 3-month postoperative period, the animals were killed, and the blocks processed for the histomorphometric assessment. Data assessment demonstrated that the CPF group showed parameters of a new connective tissue attachment, length of new cement (NC), length of new bone (mean ± SD: 0.95 ± 0.53, 2.44 ± 1.97, and 1.96 ± 2.29 mm, respectively), which were higher than those of SCTG group (mean ± SD: 0.71 ± 0.36, 2.21 ± 1.28, and 1.52 ± 1.31 mm, respectively), although not significantly (P > 0.05). The length of both epithelial tissue and connective tissue apposition in the SCTG group (mean ± SD: 1.70 ± 0.53 and 2.62 ± 1.52 mm, respectively) were higher than those of the CPF group (mean ± SD: 1.18 ± 0.49 and 2.03 ± 1.03 mm, respectively), although showing no significant differences (P > 0.05). Within the limits of the current study, it was possible to conclude that there were no significant differences between the groups according to the histologic parameters assessed.

Evaluation of Alginate coated Chitosan Membrane for Guided Tissue Regeneration

Chitosan membranes prepared by a thermal induced phase separation method and then alginate was coated onto the membrane on one side by a modified dialysis apparatus to prepare alginate/chitosan membranes (A/C membranes). ESCA analysis, SEM observation and contact angle measurements were conducted to evaluate the differences existed in the surface properties. Besides, mechanical strength, degradation behavior and especially, cell adhesion test was also examined to survey the feasibility of using this type of A/C membrane in guided tissue regeneration (GTR) application. The preliminary results obtained revealed that alginate could effectively be coated onto the chitosan membrane (from ESCA and SEM results). The contact angle decreased on the alginate side as compared with the chitosan-side (from 88.4deg to 34.2deg). The A/C membrane had a water higher content of 71.8 % as compare with the chitosan membrane (61.8%). Chitosan membranes coated with alginate also increased the Young's modulus and the ultimate strength, whereas, the elongation of these membranes were remained at the same range. A/C membrane and chitosan membrane prepared in this study degraded to about 75% of initial weight after a 30-day in vitro shaking test. The 3T3 fibroblast cells showed less adhesive on alginate side as compared with the chitosan side and glass surface in cell adhesion test. The obtained results from this study suggested that the alginate molecules could be coated onto the chitosan membrane by our modified dialysis apparatus and provided a different surface morphological structures and properties of chitosan membrane. This A/C membrane could provide extra benefits and potentials than chitosan membrane used in GTR applications.

Guided tissue regeneration for using a chitosan membrane: An experimental study in rats

Barrier membranes are employed clinically to deflect the growth of gingival tissues away from root surface. They provide an isolated space over the regions with the defective tissues that allow the relatively slow growing periodontal ligament fibroblasts to be repopulated onto the root surface. Several makes of bioabsorbable membranes are now commercially available. In this study, we have employed chitosan as barrier membrane material and evaluated it for a guided tissue regeneration application. Three types of chitosan membranes: Chi-NaOH, Chi-Na(5)P(3)O(10), and Chi-Na(2)SO(3)(each was gelated by NaOH, crosslinked by Na(5)P(3)O(10) and Na(2)SO(3), respectively), were prepared to be evaluated by the following categories: the mechanical strength to create an effective space, the rapid rate to reach hydrolytic equilibrium in phosphate-buffered solution, and the ease of clinical manipulative operations. Consequently, standardized, transosseous and critical sized skull defects were made in adult rats and the defective regions were covered with the specifically prepared chitosan membranes. After 4 weeks of recovering, varying degrees of bone healing were observed beneath the chitosan membranes in comparison to the control group. The chitosan covered regions showed a clear boundary space between connective tissues and bony tissues. Apparently, this process resulted in a good cell occlusion and beneficial osteogenesis effect to the bone. As for the control group, the bone defect was filled with connective tissue, and a destruction of the integrity of newly formed bone was observed. Among the chitosan membranes tested in this study, Chi-NaOH membrane provided a higher percentage of new bone formation than those from the Chi-Na(5)P(3)O(10) and Chi-Na(2)SO(3) families.

Effect of Enamel Matrix Derivative on Collagen Guided Tissue Regeneration-Based Root Coverage Procedure

BACKGROUND

Enamel matrix derivative (EMD) has been shown to promote periodontal wound healing and/or regeneration when applied to tooth root surfaces in soft tissue dehiscence models. In addition, guided tissue regeneration (GTR)-based root coverage using collagen membrane (GTRC) has shown promising results. However, limited information is available regarding how EMD may influence GTRC outcome.

METHODS

Twenty-six patients with Miller's Class I or II gingival recession defects of 2.5 mm were recruited for the study. Subjects were randomly assigned to receive either EMD + collagen (EMDC; test group) or collagen membrane (GTRC; control group). Clinical parameters, including plaque index (PI), gingival index (GI), relative clinical attachment levels (RCAL) to the stent, recession depth (RD), recession width (RW), probing depth (PD), gingival tissue thickness (GTT), and width of keratinized gingiva (KG) were assessed at baseline, and 3 and 6 months after surgery. A repeated measure of analysis of variance (ANOVA) was used to determine differences between treatment groups and time effect.

RESULTS

Both treatments (GTRC and EMDC) resulted in a statistically significant decrease in RD and RW between baseline and 6 months (P <0.05). However, no difference was noted between treatment groups. The percent of root coverage after 6 months was 75% for GTRC and 63% for EMDC. Complete 100% root coverage was achieved in five patients in the GTRC group, compared to only one patient in the EMDC group. There was a statistically significant gain (P <0.05) in the clinical attachment level (CAL) between baseline and 6 months in both groups, as reflected on the RCAL data. No other significant differences were noted on other clinical parameters (PD, GTT, KG, GI, and PI).

CONCLUSIONS

GTR-based root coverage utilizing collagen membrane, with or without enamel matrix derivative, can be successfully used in obtaining gingival recession coverage. The application of EMD during GTRC procedures did not add additional benefit to the final clinical outcome.

Generation of porous microcellular 85/15 poly (DL-lactide-co-glycolide) foams for biomedical applications

Porous 85/15 poly (DL-lactide-co-glycolide) or PLGA foams were produced by the pressure quench method using supercritical CO2 as the blowing agent. The rate of CO2 uptake and CO2 equilibrium concentration in PLGA at different processing conditions were studied by performing sorption experiments. The effects of saturation pressure and temperature on average cell size and relative density of the resulting foams were also studied. The time required to approach equilibrium exhibited a minimum with increasing saturation pressure. The diffusion coefficient and equilibrium concentration of CO2 in PLGA increased with an increasing pressure in an approximately linear relationship. Porous PLGA foams were generated with relative densities ranging from 0.107 to 0.232. Foams showed evidence of interconnected cells with porosities as high as 89%. The pore size ranged from 30 to 100 microm.

In vitro effect of platelet-derived growth factor-BB on collagen synthesis and proliferation of human periodontal ligament cells

OBJECTIVES

Platelet-derived growth factor (PDGF)-BB is a polypeptide growth factor which has been shown to stimulate periodontal regeneration. In this study, we investigated the time- and dose-dependent effect of PDGF-BB on the proliferation and collagen synthesis of human periodontal ligament (PDL) cells.

MATERIALS AND METHODS

For the proliferation assay, PDL cells were cultured in 0.01-10 ng ml(-1) of PDGF-BB for 12 or 24 h, and cell numbers were counted. For the collagen synthesis assay, PDL cells were cultured in 0.1-10 ng ml(-1) of PDGF-BB for 1 to 24 h. The ratio of collagen content in total protein was evaluated, and the gene expression of type I collagen was assessed quantitatively by Northern blotting analysis.

RESULT AND CONCLUSIONS

PDGF-BB stimulated the proliferation of PDL cells in a time- and dose-dependent manner with the maximum effect at 10 ng ml(-1). PDGF-BB induced the collagen synthesis of PDL cells with the maximum effect for 24-h treatment, and 1 ng ml(-1) of PDGF-BB. PDGF-BB exhibits an inverse dose-dependent effect on proliferation and collagen synthesis by PDL cells. These findings suggest that PDGF-BB is one of the important regulators of the maintenance of the extracellular matrix in PDL, and may play an important role in the regeneration of PDL.

Comparative analysis of collagen membranes for the treatment of implant dehiscence defects

Guided bone regeneration (GBR) evolved from the concept of guided tissue regeneration (GTR) and has been used for reconstructing sites with bone deficiencies associated with dental implants. For GBR, the use of absorbable collagen membranes has been increasing, but, at present, scientific information on the use of collagen membranes for GBR is limited. This study was aimed to clinically and histomorphometrically compare two collagen membranes, Bio-Gide(R) and BioMend ExtendTM, for the treatment of implant dehiscence defects in eight mongrel dogs. Implant dehiscence defects were surgically created in edentulous ridges, followed by the placement of three endosseous implants bilaterally in the mandible. Each implant dehiscence defect was randomly assigned to one of three treatment groups: (1) control (no membrane), (2) porcine dermis collagen barrier (Bio-Gide) or (3) bovine tendon collagen barrier (BioMend Extend). Dogs were sacrificed at 4 and 16 weeks (four dogs each) after treatment. Histomorphometric analysis included percentage linear bone fill (LF), new bone-to-implant contact (BIC) and area of new bone fill (BF). The results of the study revealed no significant differences among groups for any parameter at 4 weeks. However, at 16 weeks, more LF, BIC, and BF were noted in the membrane-treated groups than controls. BioMend Extend-treated defects demonstrated significantly greater BIC than control (P < 0.05) at this time point. BIC at 16 weeks was significantly greater than 4-week BIC (P < 0.05). Membrane exposure occurred in 9 out of 15 sites examined, resulting in significantly less LF and BIC than the sites without membrane exposure (P < 0.05). The results of this study indicate that: (1) GBR treatment with collagen membranes may significantly enhance bone regeneration, manifested at late stage (16 weeks) of healing; and (2) space maintenance and membrane coverage were the two most important factors affecting GBR using bioabsorbable collagen membranes.

Defect-determined regenerative options for treating periodontal intrabony defects in baboons

BACKGROUND

In an effort to regenerate periodontal intrabony defects, the healing potential of the defect should determine what therapeutic modalities and materials are employed. The purpose of this study was to compare regenerative outcomes in baboon intrabony defects that were contained versus non-contained, using various regenerative therapies.

METHODS

Nine adult baboons (Papio anubis) in good health were treated. Eighty-six interproximal, intrabony defects were surgically created: 43 contained by 3 walls of bone; 43 non-contained with a missing buccal wall. Chronicity and plaque accumulation were encouraged with wire ligature placement for 8 weeks. After ligature removal, scaling, and a 2- to 4-week healing period, the defects were treated with the following therapies: collagen membrane (GTR), human demineralized freeze-dried bone (DFDB) grafting (BG), combined therapy (GTR + BG) and a DFDB-glycoprotein sponge matrix (MAT). Clinical healing responses were evaluated in 58 sites by changes in soft tissue (recession, probing, clinical attachment) and hard tissue (resorption, defect fill) parameters 6 months post-treatment. Histologic evaluation (defect regeneration, connective tissue attachment, epithelial migration) was done on 26 sites.

RESULTS

For contained defects, no real significant clinical (ANOVA) or histologic differences existed among treatments. However, for non-contained defects, combined therapy (GTR + BG) demonstrated clinically significant (P < or = 0.05, ANOVA) and histologically superior healing results over the other therapies tested.

CONCLUSION

These results confirm a defect morphology directed rationale for periodontal intrabony therapy.

A composite graft material containing bone particles and collagen in osteoinduction in mouse

Demineralized allogenic bone matrices (DABM) and demineralized freeze-dried bone allograft (DFDBA) have been successfully used as bone-graft materials in the treatment of acquired and congenital cranio-maxillofacial defects and in some orthopedic surgery. However, these bone-graft "powders" have many shortcomings. For example, placement of particulate graft material in a hemorrhaging site can result in inadequacies or inaccurate attachment as well as loss of the graft materials. To minimize the inadequacies of powderlike graft materials, xenogenic collagen isolated from human tendon, skin, or bone was added to the bone-graft particles to form a composite spongelike implant. This material is commercially available and consists of 60% collagen and 40% DFDBA (DynaGraft, GenSci Co., Irvine, CA). The goal of this study was to evaluate the characteristics of composite graft implants in the mineralization process in an animal model in comparison with DFDBA powder and pure collagen. Seventy-two Swiss Webster mice were divided into three groups: an experimental group implanted with DynaGraft, two comparison groups implanted with either DFDBA or collagen only. All the graft materials were surgically implanted and inserted into the left thigh muscle. Mice were humanely killed at 1, 2, 3, 4, 6, 8, and 12 weeks. Then the muscle tissues in the vicinity of the implants were excised and processed for histology. Paraffin sections were stained with hematoxylin and eosin (H&E), the Von Kossa method, and Masson's trichrome. Some selected specimens were processed for transmission electron microscopic observation. After 1 week of implantation, the DynaGraft group showed calcium deposition on the collagen material and on the periphery of the DFDBA particles. Increased calcification and bone-forming cells were observed at 4-6 weeks. After 8 weeks, the implant formed a calcified nodule and only heavily mineralized connective tissue was observed at the implanted site. The group implanted with DFDBA powder showed calcification around the particulates. The collagen-sponge control group revealed no calcification or bone formation during the period of implantation. The light microscopic findings were confirmed by electron microscopy. Quantitative radiographic density DynaGraft and DFDBA graft followed sequentially over a period 120 days. It was concluded that a higher rate of calcification and bone formation was produced in the composite graft implant compared to the DFDBA implant. The composite graft material (DynaGraft), which contains both collagen and DFDBA, proved to be more effective for bone formation than particle components alone.

Comparison of 2 clinical techniques for treatment of gingival recession

BACKGROUND

In early case studies, use of a collagen barrier as a guided tissue regeneration (GTR) material has shown particular promise in procedures aimed at root coverage. The similarities between collagen membrane and subepithelial connective tissue graft (SCTG) have made collagen membrane an attractive and a possible alternative material for root coverage. The purpose of this randomized clinical trial was to compare these 2 techniques, SCTG versus a GTR-based procedure (GTRC), for root coverage/recession treatment.

METHODS

Sixteen patients with bilateral Miller's Class I or II (gingival recession > or = 3.0 mm) recession defects were treated either with SCTG or GTRC using a newly designed collagen membrane. Clinical parameters monitored included recession depth (RD), clinical attachment level (CAL), probing depth (PD), width of keratinized gingiva (KG), attached gingiva (AG), and recession width (RW), each measured at the mid-buccal area to the nearest 0.5 mm. Measurements were taken at baseline and 6 months. A standard mucogingival surgical procedure was performed. Data were reported as means +/- SD and were analyzed using the paired t test for univariate analysis and restricted/residual maximal likelihood (REML)-based mixed effect model for multivariate analysis.

RESULTS

No statistically significant differences were observed in RD, CAL, KG, and AG between test and control groups at either time period. However, SCTG showed significantly more residual PD and more RW gain when compared to GTRC at 6 months. Both treatments resulted in a statistically significant (P < 0.05) reduction of recession defects (2.5 mm and 2.8 mm), gain of CAL (2.8 mm and 2.3 mm), reduction of RW (1.9 mm and 2.7 mm), and increase of KG (0.7 mm and 1.1 mm) and AG (0.7 mm and 0.5 mm) for GTRC and SCTG, respectively, when comparing 6-month data to baseline. Mean root coverage of 73% (collagen membrane) and 84% (subepithelial connective tissue graft) was achieved.

CONCLUSIONS

The 2 techniques are clinically comparable. Use of a modified collagen membrane to attain root coverage may alleviate the need for donor site procurement of connective tissue.

Collagen membrane resorption in dogs: a comparative study

Guided tissue barriers using materials such as collagen are used in the hope of excluding epithelium and the gingival corium from the root surface or alveolar bone to facilitate regeneration. Convention suggests that the longer a membrane remains intact, the better the regeneration results. The purpose of this study was to determine the resorption rates of various collagen membranes in the oral cavity of dogs. Twelve adult mongrel dogs had three different collagen membranes (BioGide, AlloDerm porcine-derived, and AlloDerm human-derived) randomly inserted and secured into surgical pouches made in their palates. Full-thickness tissue punch biopsy specimens taken at 1, 2, 3, or 4 months after surgery were evaluated histologically for membrane intactness and other associated changes. At 1 month, all membranes had slight to moderate degradation. At 2 months, all membranes had moderate to severe degradation with the exception of one AlloDerm human-derived membrane that was intact. At 3 months, all membranes had severe degradation to not identifiable. At 4 months, all membranes had severe degradation to completely absent. Blood vessel penetration varied from none to moderate. Inflammation was found in only two samples. In the dog, all three tested collagen membranes showed slight to moderate degradation at 1 month and were severely degraded to completely absent at 4 months. Within the limits of transferring animal data to humans, clinicians need to be aware of these resorption rates when selecting membranes for guided tissue and bone regeneration.

Collagen membranes: a review

Collagen materials have been utilized in medicine and dentistry because of their proven biocompatability and capability of promoting wound healing. For guided tissue regeneration (GTR) procedures, collagen membranes have been shown to be comparable to non-absorbable membranes with regard to probing depth reduction, clinical attachment gain, and percent of bone fill. Although these membranes are absorbable, collagen membranes have been demonstrated to prevent epithelial down-growth along the root surfaces during the early phase of wound healing. The use of grafting material in combination with collagen membranes seems to improve clinical outcomes for furcation, but not intrabony, defects when compared to the use of membranes alone. Recently, collagen materials have also been applied in guided bone regeneration (GBR) and root coverage procedures with comparable success rates to non-absorbable expanded polytetrafluoroethylene (ePTFE) membranes and conventional subepithelial connective tissue grafts, respectively. Long-term clinical trials are still needed to further evaluate the benefits of collagen membranes in periodontal and peri-implant defects. This article will review the rationale for each indication and its related literature, both in vitro and in vivo studies. The properties that make collagen membranes attractive for use in regenerative therapy will be addressed. In addition, varieties of cross-linking techniques utilized to retard the degradation rate of collagen membranes will be discussed.

Comparison of bioabsorbable and non-resorbable membranes in the treatment of dehiscence-type defects. A histomorphometric study in dogs

BACKGROUND

The goal of this investigation was to compare, histologically and histometrically, the healing process of dehiscence-type defects treated by guided tissue regeneration (GTR) with bioabsorbable polylactic acid (PLA) membranes and non-resorbable expanded polytetrafluoroethylene (ePTF) membranes.

METHODS

Six mongrel dogs were used. Buccal osseous dehiscences were surgically created on the distal roots of the mandibular third and fourth premolars. The defects were exposed to plaque accumulation for 3 months. After this period, the defects were randomly assigned to one of the treatments: GTR with bioabsorbable membrane (PLA), GTR with non-resorbable membrane (ePTFE), open flap debridement (OFD), and non-treated control (NTC). After 3 months of healing, the dogs were sacrificed and the blocks were processed. The histometric parameters evaluated included: gingival recession, epithelial length, connective tissue adaptation, new cementum, and new bone area.

RESULTS

A superior length of new cementum was observed in the sites treated by GTR, regardless of the type of barrier used, in comparison with OFD (P <0.05). No statistically significant differences were found between PLA and ePTFE in any of the parameters with the exception of bone area. PLA presented a greater bone area when compared to ePTFE, OFD, and NTC (P <0.05).

CONCLUSIONS

Within the limits of this study, it can be concluded that both barriers are equally effective for new cementum formation. The bioabsorbable membrane may provide a greater bone area than the non-resorbable membrane.

The use of 2 bioabsorbable barrier membranes in the treatment of interproximal intrabony periodontal defects

BACKGROUND

The use of barrier membranes in the treatment of periodontal defects is well documented. There has been an increase in the use of bioabsorbable materials which do not require a second surgical procedure for removal. However, there are little data evaluating the efficacy of bioabsorbable membranes in the treatment of intrabony defects. The purpose of this investigation was to evaluate the regenerative potential of 2 bioabsorbable barrier membranes without the use of grafting materials in the treatment of interdental intrabony defects.

METHODS

Twenty-three 2- or 3-walled intrabony defects were treated in 19 patients with a mean age of 50.4 years. All had completed nonsurgical treatment and a period of supportive periodontal therapy. The sites were randomly chosen to receive a barrier membrane composed of type I bovine collagen (11) or a copolymer of polylactic acid (PGA/PLA;12). A pressure sensitive disc probe was used to evaluate the following criteria at baseline and re-entry: 1) occlusal surface to the apical depth of probe penetration (OS-DP); 2) occlusal surface to the gingival margin (OS-GM); 3) occlusal surface to the alveolar crest (OS-AC); and 4) occlusal surface to the base of the osseous defect (OS-BD). Full thickness mucoperiosteal flaps were reflected to expose the surgical sites. The defects were debrided of the granulomatous tissue, the root surfaces instrumented and conditioned with 4 one-minute applications of 50 mg/ml of tetracycline. The barrier membranes were adapted to cover the defects and the flaps replaced. The postsurgical healing was uneventful and similar in both treatment modalities.

RESULTS

Twenty-three sites were surgically re-entered 6 months from the time of the initial surgery. The deepest probe depth for each site was used for statistical analysis. There was a mean relative attachment gain of 2.58+/-1.90 mm for the collagen, and 2.77+/-2.13 mm for the copolymer. There was a decrease in probing depth of 3.27+/-1.91 mm and 0.69+/-1.35 mm of recession for the collagen. The PGA/PLA copolymer had 3.55+/-2.47 mm reduction in probe depth and 0.78+/-1.14 mm of recession.

CONCLUSIONS

The data indicated the bioabsorbable collagen and copolymer membranes resulted in comparable results. A larger sample size would be necessary to determine if one membrane was superior to the other.

Guided tissue regeneration with bioabsorbable and expanded polytetrafluoroethylene barrier membranes in the treatment of naturally occurring periodontal defects in dogs

The purpose of the present study was to evaluate the healing events and compare the effects of guided tissue regeneration (GTR) using 3 different membranes: a weakly cross-linked bioabsorbable bovine collagen membrane; a strongly cross-linked bioabsorbable bovine collagen membrane; and a non-resorbable ePTFE membrane. Twenty adult female beagle dogs with naturally occurring periodontitis were subjected to periodontal probing and scaling. In both right and left mandibular quadrants, mucoperiosteal flaps were raised, and after debridement, the roots of experimental premolar teeth received apical reference notches. The following treatments were randomly assigned: 1) gingival flap curettage (GFC) + ePTFE membrane, control membrane; 2) GFC + slightly cross-linked collagen membrane, 1st test membrane; and 3) GFC + strongly cross-linked collagen membrane, 2nd test membrane. The flaps were sutured in such a manner that the membranes were completely covered. All dogs received a soft diet for a 2-week period and an oral hygiene program until time of sacrifice. The animals were randomly scheduled for sacrifice at 2, 4, 12, and 24 weeks. The ePTFE membranes still in place were removed at 6 weeks. The jaws were dissected and specimens prepared for descriptive histology and histomorphometry. The early resorption of the 1st test membrane was achieved at 4 weeks, and the 2nd test membrane at 12 weeks, both with normal inflammatory reaction. Measurements of epithelium, connective tissue attachment, new bone, and neocementum were compared within an animal (paired t test). Analyses were performed on data at 4, 12, and 24 weeks post-healing; little differences were found between these periods. Limited connective tissue repair was favored by the placement of all the membranes (about 20%), with no statistically significant difference. These findings indicate that bioabsorbable collagen membranes with different cross-linking and ePTFE barriers promote similar new attachment in GTR procedures on naturally occurring periodontal defects in dogs.

A 2-year clinical evaluation of a diphenylphosphorylazide-cross-linked collagen membrane for the treatment of buccal gingival recession

To retard collagen membrane enzymatic degradation and to increase its mechanical strength, the diphenylphosphorylazide (DPPA) technique has been demonstrated to achieve natural cross-links between peptide chains of collagen without leaving any foreign product in the cross-linked molecule. In the present prospective clinical trial, the potential of a DPPA-cross-linked type I bovine collagen membrane was evaluated in the healing of 15 buccal soft tissue recessions in 15 patients according to the biological concept of guided tissue regeneration. The recession decreased from 3.7 mm (SD 1.4) at baseline to 0.8 mm (SD 1.2) at 2 years postsurgery, corresponding to a mean root coverage of 82.2% (P <0.0001). Concurrently, the clinical attachment level decreased from 5.4 mm (SD 1.6) at baseline to 1.9 mm (SD 1.2) 2 years postsurgery, corresponding to an average clinical attachment gain of 3.5 mm (SD 1.3) (P <0.0001). The 2-year postsurgical width of the keratinized tissue was not significantly different from baseline values. More than half (53%) of the treated sites showed complete root coverage and about two-thirds (73%) of the total cases showed a 75% to 100% disappearance of the mucogingival defect. The present investigation demonstrated that the use of DPPA-cross-linked collagen membranes in the treatment of human buccal soft tissue recessions results in predictable amounts of root coverage and clinical attachment gain. Long-term randomization controlled clinical trials of this material are needed to fully evaluate its potential for treating periodontal recession.

Elastic modulus, permeation time and swelling ratio of a new porcine dermal collagen membrane

The goal of a single step therapy has been an important consideration in the development of guided tissue regeneration devices. It would spare the patient from the need for repeated surgery and eliminate many problems associated with a non-resorbable barrier. Animal studies of a collagen membrane extracted from porcine dermis (PDCM), as conditioned by different concentrations of glutaraldehyde (GA), have shown it to be biocompatible and biodegradable (up to 9 wk). This in vitro study further investigated the physical properties of this membrane. A PDCM modified and cross-linked with various concentrations (0.01%, 0.05% and 3.00%) of GA was used. A similar control series was not conditioned. At least 4 specimens for each experimental condition were prepared. The elastic modulus (EM) was measured by a universal testing machine. In the permeability test, Al2O3 particles of different sizes (5-23 microns) were mixed with normal saline to make 5 v/v% suspension and the time needed for collecting 7.5 ml of the filtered suspension from 10 ml suspension was recorded. Swelling ratio (gamma) was also measured according to gamma = 1/Vf (volume fraction). Data were analysed using ANOVA and Tukey's LSD test. The EM (40.8 +/- 3.8 gf/mm2) for the GA conditioned membranes showed no significant difference but was greater (p < 0.05) than that of the control. There was a significant increase (100-300%) in the permeation time with GA concentration (control 0.168 vs. 3% GA 0.100). The results suggest that the physical properties of the GA conditioned PDCM (especially in 3%) may fit the clinical requirements of membrane materials used in guided tissue regeneration techniques.

Awareness of periodontal disease--the role of industry

Recently periodontal treatments have been performed intensively in daily clinical work and the definitive approach to periodontal therapy has been established in various types of periodontal diseases. It is no exaggeration to say that this is impossible without the co-operation of the dental industry. Furthermore, industry has also contributed greatly to the improvement of the 'quality of life', concerning masticatory function in the elderly. Both the progression of dental devices and the development of diagnostic methods have been considered to be the primary prerequisite for success in treatment and in the prevention of recurrence of the periodontal diseases. It is necessary that dental devices and medications for treatment should be developed corresponding to the advanced scientific evaluation of periodontal disease. This paper reviews our present knowledge about the role or contribution of industry to periodontology in terms of periodontal health care products, diagnostic kits, and therapeutic drugs.

Clinical comparison of resorbable and non-resorbable barriers for guided periodontal tissue regeneration

The purpose of this study was to compare the clinical results of guided periodontal tissue regeneration (GPTR) using a resorbable barrier manufactured from a copolymer of polylactic and polyglycolic acids (Resolut Regenerative Material) with those of non-resorbable e-PTFE barrier (Gore-Tex Periodontal Material). 12 subjects participated, 6 with similarly paired class II furcations and 6 with 2 similar 2, 3-wall periodontal lesions. The resorbable and non-resorbable barriers were randomly assigned to 1 defect in each subject. Non-resorbable barriers were removed in six weeks. Plaque index (PlI), gingival index (GI), probing depth (PD), clinical attachment level (CAL) and gingival recession (R) were recorded at baseline, (i.e., immediately prior to surgery) and at 12 months postsurgically. The clinical healing was similar and uneventful in both groups. Intrabony pockets depicted significant changes from baseline (p < 0.05) for probing depth reduction and gain in clinical attachment levels. No differences were found between treatments. Class II furcations showed significant improvements from baseline (p < or = 0.05) for probing depth reduction and clinical attachment gain. No differences were detected between treatments. It is concluded that the resorbable barrier tested is as effective as the nonresorbable e-PTFE barrier for the treatment of class II furcations and intrabony defects.

Evaluation of anionic collagen membranes in the treatment of class II furcation lesions: an histometric analysis in dogs

This study aims to evaluate the effect of using anionic collagen membranes in guided tissue regeneration treatment of Class II furcation lesions in dogs. The defects were created in the buccal furcation of 16 mandibular premolars of four dogs. After 56 days without plaque control, the sites were scaled and divided into two groups according to the treatment applied: control sites, open flap debridement; and test sites, guided tissue regeneration treatment. The animals were killed after 3 months. Histological and histometrical analyses showed that the collagen membrane was better than open flap debridement in terms of newly formed cementum and epithelial migration prevention. It provided effective blockade of epithelial tissue and promoted regeneration of lost periodontal tissues, suggesting that the membrane warrants further study.

Development and clinical evaluation of a root coverage procedure using a collagen barrier membrane

The use of guided tissue regeneration (GTR) procedures in the treatment of gingival recession has shown promising results and is gaining clinical acceptance. The purpose of this study was to assess the use of a bioabsorbable collagen membrane as a barrier device in root coverage treatment of gingival recession defects. The study consisted of 10 patients with 10 defects of either Miller Class I or II description and gingival recession > or =2.5 mm. Clinical measurements taken at baseline included plaque index (PI) and gingival index (GI), clinical attachment level (CAL) measured with an automated probe and reference stent, recession depth (RD; mean = 3.19 +/- 0.26 mm), recession width (RW; 3.95 +/- 0.41 mm), probing depth (PD; 2.3 +/- 0.2 mm), and width of keratinized tissue (KT; 2.4 +/- 0.3 mm); measurements were repeated at 1, 2, and 4 weeks and 3 and 6 months post-treatment. During the surgical procedure, a mucoperiosteal flap was elevated and the respective root thoroughly planed. The collagen membrane was cut to cover the defect and surrounding bone, positioned over the root, and secured with 5-0 gut interdental sutures. The flap was coronally positioned to cover the membrane and sutured with 5-0 silk. Data were analyzed using the Student paired t-test to compare pre- and postsurgery measurements. The nonparametric Wilcoxon matched pairs test was used to analyze the significance of PI and GI at different time intervals. A statistically significant (P < 0.01) reduction in RD (-1.66 +/- 0.25 mm) was observed at 6 months, representing 51.6% total attainable root coverage. Clinically, a statistically significant mean gain of 1.34 +/- 0.47 mm CAL and 0.90 +/- 0.32 mm KT was observed at 6 months. No statistical differences were found in PD and RW between baseline and 6 months postoperatively. PI and GI remained low and showed no statistically significant change (P < 0.05) throughout the study period. Results from this study suggest that a collagen membrane can be used successfully as a barrier device in GTR-based root coverage procedures.

Combined collagen membrane and hydroxyapatite/collagen chondroitin-sulfate spacer placement in the treatment of 2-wall intrabony defects in chronic adult and rapidly progressive periodontitis patients

This study, confined to non-smokers, evaluated guided-tissue regeneration in deep 2-wall intrabony defects using a diphenylphosphorylazide-cross-linked bovine type I collagen membrane supported by a hydroxyapatite/collagen/chondroitin-sulfate spacer in 43 adult periodontitis (AP) and 14 rapidly progressive periodontitis (RPP) patients, no more than 1 defect being randomly selected for each patient. Before surgery and 6 months after surgery, plaque (PI) and sulcus bleeding (SBI) indices, probing pocket depths (PPD), gingival margin locations (GML) and probing attachment levels (PAL) were recorded. During the post-surgical period, the biomaterials were well tolerated in all patients and PI and SBI were kept at a low level. Following therapy, there was a significant gain in PAL (4.2 mm for AP; 3 mm for RPP) and reduction in PPD (6.1 mm for AP; 4.7 mm for RPP) for both groups of patients (p < 0.05). A significantly greater gain in PAL and reduction in PPD were observed for AP compared to RPP patients (p < 0.05). The change in GML was not statistically different between groups (1.8 mm for AP; 1.6 mm for RPP). It is concluded that the combined use of a diphenylphosphorylazide-cross-linked bovine type-I collagen membrane, supported by a hydroxyapatite/collagen/chondroitin-sulfate spacer, is beneficial in improving PAL and reducing PPD in 2-wall intrabony defects in both AP and RPP patients during the quiescent phase of the disease, with statistically better results for the former group. However, longer observation periods are necessary to evaluate the stability of the improvements obtained by this combined treatment approach between and for each group of patients.

Assessment of guided tissue regeneration procedures in intrabony defects with bioabsorbable and non-resorbable barriers

THE PURPOSE OF THIS STUDY was to assess periodontal regenerative techniques in intrabony defects utilizing a bioabsorbable, polylactic acid (PLA) barrier or the non-resorbable, expanded polytetrafluoroethylene (ePTFE) barrier. Thirty patients (26 to 64 years old) each with one radiographically evident intrabony periodontal lesion of probing depth > or = 6 mm participated in a 12-month controlled clinical trial. The subjects were randomly divided into two independent groups. The test group (n = 16) received a PLA barrier. The control group (n = 14) received an ePTFE barrier. Plaque index (PI), gingival index (GI), probing depth (PD), clinical attachment level (CAL), and bone fill were recorded by a single calibrated examiner not involved with the surgical treatment prior to surgery, and at 6, 9, and 12 months postsurgery. The treatment results were statistically analyzed utilizing two sets of data. The "averaged-site" data set consisted of values computed from the averaging of measurements from all sites encompassing the defect. The second data set was comprised of only the deepest measurement of the defect. Statistical tests used to analyze these data sets included the t-test and paired t-test for parametric data and the Wilcoxon rank sum test and the Wilcoxon signed rank test for non-parametric data. Analyses with both the averaged-site data and deepest-site data resulted in significant improvements in PD reductions, CAL, and bone fill, after 12 months of healing with both the PLA and ePTFE barrier devices. Comparisons of healing response between treatments found no significant differences when the averaged-site data were analyzed. When only the deepest site of the defect was considered, the control group resulted in significantly more attachment gain (ePTFE, 3.36 mm; PLA, 1.75 mm; P < 0.02) and shallower probing depths (ePTFE, 3.29 mm; PLA, 4.69 mm; P < 0.01) than the test group. In intrabony defects, the use of PLA or ePTFE barriers in GTR procedures yielded comparable clinical results; however, in this study, data analysis using the deepest site of the defect found, after 12 months of healing, significantly more attachment gain and shallower probing depths with ePTFE.

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

There are presently a number of different barriers available for use clinically in guided tissue regeneration (GTR) procedures. A number of trials using these techniques and comparing different types of barrier membranes are being published in the scientific literature. This review discusses issues related to clinical trials on the use of barrier membranes in periodontal regeneration. Outcome measures, both clinical and histological, are discussed in relation to results following GTR procedures. The difference between regeneration and repair is reviewed as well as methods of clinical and histologic assessment of both these outcomes. Data regarding the impact of patient variables and tooth or defect variables on outcomes are presented and suggestions for study designs are made based on these variables. Aspects of assessing for an appropriate sample size in superiority and equivalency trials using GTR techniques are presented as well as interpretation of results following these trials and their clinical significance.

Vascular response to guided tissue regeneration procedures using nonresorbable and bioabsorbable membranes in dogs

Revascularization of the periodontal tissues was studied following guided tissue regeneration (GTR) procedures using both nonresorbable and bioabsorbable membranes. The procedures were performed in 8 female beagle dogs, 4 to 6 years old. Second, third, and fourth mandibular premolars were involved; experimental periods covered from 3 days to 49 days. After elevation of soft tissue flaps, Class II furcation defects were prepared by removing buccal alveolar bone from the teeth and exposed root surfaces were planed in order to remove root cementum. The quadrant was then flushed with sterile saline. Randomly selected, in one quadrant, the second and fourth premolars received nonresorbable expanded polytetrafluoroethylene (ePTFE) membranes. The other quadrant, second and fourth premolars, received the bioabsorbable membranes, made of glycolide and lactide polymers. After the membranes were in place, they were sutured. The third premolars of both quadrants served as negative controls. The animals were sacrificed by exsanguination under general anesthesia and then perfused through the carotid arteries with a combined solution of equal parts of India ink and 10% buffered formalin. Following fixation and demineralization, part of the blocks were processed to obtain cleared specimens following the method of Spalteholtz. The remaining blocks were processed for routine histologic examination. The findings, mainly from the cleared specimens, showed that at the early phase of healing, ePTFE membranes interfered with the revascularization while they were in place. Contrary to this, bioabsorbable membranes allowed earlier anastomosis of the vasculature of the flap and regenerated tissues. However, the long-term vascular response was similar for both membranes.

Periodontal regeneration around natural teeth

1. Evidence is conclusive (Table 2) that periodontal regeneration in humans is possible following the use of bone grafts, guided tissue regeneration procedures, both without and in combination with bone grafts, and root demineralization procedures. 2. Clinically guided tissue regeneration procedures have demonstrated significant positive clinical change beyond that achieved with debridement alone in treating mandibular and maxillary (buccal only) Class II furcations. Similar data exist for intraosseous defects. Evidence suggests that the use of bone grafts or GTR procedures produce equal clinical benefit in treating intraosseous defects. Further research is necessary to evaluate GTR procedures compared to, or combined with, bone grafts in treating intraosseous defects. 3. Although there are some data suggesting hopeful results in Class II furcations, the clinical advantage of procedures combining present regenerative techniques remains to be demonstrated. Additional randomized controlled trials with sufficient power are needed to demonstrate the potential usefulness of these techniques. 4. Outcomes following regenerative attempts remain somewhat variable with differences in results between studies and individual subjects. Some of this variability is likely patient related in terms of compliance with plaque control and maintenance procedures, as well as personal habits; e.g., smoking. Variations in the defects selected for study may also affect predictability of outcomes along with other factors. 5. There is evidence to suggest that present regenerative techniques lead to significant amounts of regeneration at localized sites on specific teeth. However, if complete regeneration is to become a reality, additional stimuli to enhance the regenerative process are likely needed. Perhaps this will be accomplished in the future, with combined procedures that include appropriate polypeptide growth factors or tissue factors to provide additional stimulus.

Influence of three membrane types on healing of bone defects

OBJECTIVES

To determine and compare osseous regeneration associated with three guided tissue regeneration membrane types (expanded polytetrafluoroethylene, dense polytetrafluoroethylene, and an absorbable polylactic acid/citric acid ester base) and removal forces required for expanded and dense polytetrafluoroethylene membranes.

STUDY DESIGN

Bilateral osseous defects were created in 30 adult rat calvaria; one defect was covered with a test membrane and the other received no membrane (control). After 2 or 4 weeks, forces required for membrane removal from the tissues were electronically determined, and the calvaria removed and decalcified. Sections through the defects were stained and evaluated electronically and microscopically. Data were analyzed statistically.

RESULTS

Microscopic evaluation with Mann-Whitney U test revealed that dense polytetrafluoroethylene was associated with significantly greater bone formation than expanded polytetrafluoroethylene (p = 0.02) at 2 weeks and absorbable polylactic acid/citric acid ester base (p = 0.004) at 4 weeks. Electronic evaluation of the linear degree of fill with one way ANOVA and Tukey's test found no significant difference (p > 0.05) among the experimental or the control groups. In addition, the Mann-Whitney U test indicated that removal forces required for dense polytetrafluoroethylene were significantly less than for expanded polytetrafluoroethylene (p = 0.003).

CONCLUSIONS

The use of dense polytetrafluoroethylene as a membrane barrier deserves further investigation as it allows osseous regeneration, it is easier to remove from healing soft tissues, and it is inexpensive. A study with larger sample sizes should be conducted.

Effects of polyglactin mesh combined with resorbable calcium carbonate or replamineform hydroxyapatite on periodontal repair in dogs

This study evaluates periodontal repair and biomaterial reaction following implantation of a polyglactin mesh with or without porous resorbable calcium carbonate (RCC) or porous replamineform hydroxyapatite (RHA) in conjunction with reconstructive surgery. Ligature- and surgically-induced interproximal periodontal defects of left and right mandibular premolar teeth in 7 dogs were used. Bilaterally, mesial defects of the 2nd, 3rd and 4th premolar teeth were treated with polyglactin mesh, polyglactin mesh and RHA, or polyglactin mesh and RCC, respectively. The polyglactin mesh, shaped according to the contour of the defect, was adapted to the experimental teeth; its coronal margin positioned immediately apical to the cemento-enamel junction. Gingival flap margins were adapted and sutured to cover the polyglactin mesh completely. Clinical healing was generally uneventful. The dogs were sacrificed to provide block sections for histologic evaluation at 1, 3, 6, 12, 26, 32 and 56 weeks following wound closure. Generally, cementum regeneration was observed beginning at week 6 in all groups. Bone regeneration was observed from week 3 in polyglactin mesh-treated groups, and from week 6 in polyglactin mesh+RCC or polyglactin mesh+RHA treated groups. Bone regeneration appeared enhanced in polyglactin mesh+RCC or polyglactin mesh+RHA treated defects at week 12 and 26, with little difference between the three experimental conditions at week 56. Polyglactin mesh degradation was observed at week 3 and appeared complete at week 12. The RHA did not appear to resorb, while the RCC was gradually replaced by bone from week 3. Within limitations of the study conditions, periodontal regeneration was observed following implantation of a polyglactin mesh with or without RCC or RHA in conjunction with reconstructive surgery. As a conclusion, there seems to be no significant difference in periodontal regeneration after 12 months of healing between the group treated with the membrane only, and the group treated with the membrane and the bone substitution material. Changes in connective fiber orientation over the 1st 12 weeks of healing may suggest that "fibrous encapsulation" observed in earlier studies may only represent a transient stage in periodontal regeneration.

A prospective multi-center study evaluating periodontal regeneration for Class II furcation invasions and intrabony defects after treatment with a bioabsorbable barrier membrane: 1-year results

The purpose of this prospective multi-center study was to evaluate a resorbable barrier membrane designed for periodontal regeneration. Thirty-one Class II furcations and 30 two- and three-wall intrabony defects were treated by flap debridement and bioabsorbable barrier membrane augmentation. The efficacy of treatment was evaluated in terms of changes in vertical probing depth (PD), horizontal probing depth (HPD), clinical attachment levels (CAL), and recession. Five centers participated in the study. Changes in clinical parameters are reported by individual center and by the average of the centers. All patients had either one molar with a Class II furcation or an intrabony defect. Baseline data were taken on the day of surgery. Post-treatment data were collected at 6 months and 1 year. This report is based on the 1-year findings. The average initial PD for Class II furcations was 6.1 mm. At 1 year the average PD was reduced to 3.6 mm, a 2.5 mm change. These differences were clinically and statistically significant (P < 0.0001). There was an average gain of 2.1 mm of clinical attachment (P < 0.0001) and 0.4 mm of recession (P < 0.04). There was a mean of 1.8 mm change in HPD (P < 0.0001). For intrabony defects, at 1 year there was an average PD reduction of 4.1 mm (P < 0.0001) and a mean gain of CAL of 2.9 mm (P < 0.0001). At 1 year the average recession was 0.9 mm which was statistically significant. When treatment outcomes were compared between centers there were no differences for either group of treated defects. There were differences between centers when baseline PD for furcations and intrabony sites were compared. The results of this study indicate that clinically and statistically significant improvements in PD, CAL, and HPD occurred after treatment of Class II furcations and 2- to 3-wall intrabony defects with the bioabsorbable periodontal membrane.