Bacterial colonization of barrier material and periodontal regeneration

Membrane barriers for guided bone regeneration: An overview of available biomaterials

Dental implants revolutionized the treatment options for restoring form, function, and esthetics when one or more teeth are missing. At sites of insufficient bone, guided bone regeneration (GBR) is performed either prior to or in conjunction with implant placement to achieve a three-dimensional prosthetic-driven implant position. To date, GBR is well documented, widely used, and constitutes a predictable and successful approach for lateral and vertical bone augmentation of atrophic ridges. Evidence suggests that the use of barrier membranes maintains the major biological principles of GBR. Since the material used to construct barrier membranes ultimately dictates its characteristics and its ability to maintain the biological principles of GBR, several materials have been used over time. This review, summarizes the evolution of barrier membranes, focusing on the characteristics, advantages, and disadvantages of available occlusive barrier membranes and presents results of updated meta-analyses focusing on the effects of these membranes on the overall outcome.

In vitro evaluation of membranes for regenerative procedures against oral bacteria

The current literature on guided bone regeneration (GBR) and guided tissue regeneration (GTR) membrane contamination reports that the physicochemical characteristics of these biomaterials might influence affinity to bacteria, which appears to be a major drawback for the clinical outcome of the regenerative procedures. Thus, this study aimed to evaluate, in vitro, a multispecies biofilm adherence and passage of bacteria through different types of commercially available membranes for GTR/GBR. Four types of membranes were tested (n=12): LC) Lumina Coat®; JS) Jason®; BG) Biogide®; and LP) Lumina PTFE®. Aluminum foil (AL) simulated an impermeable barrier and was used as the control. The membranes were adapted to specific apparatus and challenged with a mixed bacterial culture composed of A. actinomycetemcomitans b, S. mutans, S. mitis, and A. israelii. After 2 h or 7 days, bacterial adhesion and passage of bacteria were evaluated through CFU counting, which was analyzed by two-way ANOVA e post hoc Tukey, at a 5% significance level. Representative areas of two membranes of each group were analyzed through scanning electron microscopy (SEM) to assess the morphology and organization of the biofilm over the membrane fibers. LC and LP presented similar values of adhered bacterial cells (p > 0.05), significantly inferior when compared to the other groups, in both time points (p < 0.05). All the tested groups were permeable to bacterial cells, with no significant difference between the trial period of 2 h and 7 days (p > 0.05). SEM analyses demonstrated that adhered bacteria number increased throughout the time points (2 h < 7 days). Commercially available biological membranes demonstrated intense bacterial adherence and passage of bacteria, which increased throughout the trial period.

Bacterial Growth on Three Non-Resorbable Polytetrafluoroethylene (PTFE) Membranes-An In Vitro Study

GBR (Guided Bone Regeneration) procedure is challenged by the risk of membrane exposure to the oral cavity and contamination. The barrier quality of these membranes serve as a mechanical block from bacterial penetration into the GBR site. The purpose of this in vitro study was to evaluate the antibacterial effect of three commercial non-resorbable polytetrafluoroethylene membranes. (Two d-PTFE membranes and one double layer e-PTFE +d-PTFE membrane). A validated in vitro model with two bacterial species (Streptococcus sanguinis and Fusobacterium nucleatum) was used. Eight samples from membrane each were placed in a 96-well microtiter plate. The experimental and positive control groups were exposed to a bacterial suspension which involved one bacterial species in each plate. Bacterial growth was monitored spectrophotometrically at 650 nm for 24 h in temperature controlled microplate spectrophotometer under anaerobic conditions. One- Sample Kolmogorov−Smirnov Normal test and the Kruskal−Wallis test was used for the statistical analysis. As shown by the bacterial growth curves obtained from the spectrophotometer readings, all three membranes resulted in bacterial growth. We have not found a statistical difference in F. nucleatum growth between different membrane samples and the positive control group. However, S. sanguinis growth was reduced significantly in the presence of two membranes (CYTOPLAST TXT-200 and NeoGenTM) when compared to the control (p < 0.01). The presence of Permamem® had no significant influence on S. sanguinis growth. Some types of commercial non-resorbable PTFE membranes may have an impact on the growth dynamics of specific bacterial species.

Periodontal granulation tissue preservation in surgical periodontal disease treatment: a pilot prospective cohort study

Purpose

Methods

Results

Conclusions

The recent advances in scaffolds for integrated periodontal regeneration

The periodontium is an integrated, functional unit of multiple tissues surrounding and supporting the tooth, including but not limited to cementum (CM), periodontal ligament (PDL) and alveolar bone (AB). Periodontal tissues can be destructed by chronic periodontal disease, which can lead to tooth loss. In support of the treatment for periodontally diseased tooth, various biomaterials have been applied starting as a contact inhibition membrane in the guided tissue regeneration (GTR) that is the current gold standard in dental clinic. Recently, various biomaterials have been prepared in a form of tissue engineering scaffold to facilitate the regeneration of damaged periodontal tissues. From a physical substrate to support healing of a single type of periodontal tissue to multi-phase/bioactive scaffold system to guide an integrated regeneration of periodontium, technologies for scaffold fabrication have emerged in last years. This review covers the recent advancements in development of scaffolds designed for periodontal tissue regeneration and their efficacy tested in vitro and in vivo. Pros and Cons of different biomaterials and design parameters implemented for periodontal tissue regeneration are also discussed, including future perspectives.

Efficacy of periodontal minimally invasive surgery with and without regenerative materials for treatment of intrabony defect: a randomized clinical trial

OBJECTIVES

The minimally invasive surgical technique was modified in suture (MISTms) in this study. The trial was to determine the efficacy of MISTms with and without regenerative materials for the treatment of intrabony defect and to identify factors influencing 1-year clinical attachment level (CAL) gain.

METHODS

Thirty-six patients with interdental intrabony defects were randomly assigned to MISTms (MISTms alone, 18) or MISTms plus deproteinized bovine bone mineral and collagen membrane (MISTms combined, 18). Wound healing was evaluated by early healing index (EHI) at 1, 2, 3, and 6 weeks. Probing depth (PD), CAL, gingival recession, radiographic defect depth, and distance from the base of defect to the cementoenamel junction were recorded at baseline and 1 year postoperatively. A one-year composite outcome measure based on the combination of CAL gain and post-surgery PD was evaluated. Factors influencing 1-year CAL gain were analyzed.

RESULTS

Fifteen patients in MISTms-alone and 16 in the MISTms-combined group finished the study. The MISTms-alone group showed significantly better wound healing at 1 week. CAL significantly gained in the MISTms-alone and MISTms-combined group, with 2.53 ± 1.80 mm and 2.00 ± 1.38 mm respectively. The radiographic bone gain was 3.00 ± 1.56 mm and 3.85 ± 1.69 mm respectively. However, there were no significant differences between the two groups about 1-year outcomes. Lower EHI (optimal wound healing) and more baseline CAL positively influenced 1-year CAL gain.

CONCLUSIONS

MISTms is an effective treatment for intrabony defects. The regenerative materials do not show an additional effect on 1-year outcomes. Early wound healing and baseline CAL are factors influencing 1-year CAL gain.

CLINICAL RELEVANCE

MISTms with and without regenerative materials are both effective treatments for intrabony defect.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: ChiCTR2100043272.

Critical features of periodontal flaps with regard to blood clot stability: A review

BACKGROUND

Wound healing is a multifactorial procedure involving different cell types and biological mediators. The principles of wound healing are also applicable to periodontal tissues. The formation and stability of blood clots play a vital role in successful healing of wounds in periodontal tissues. The aim of the present review was to highlight the vital factors of periodontal flaps associated with blood clot stability.

HIGHLIGHT

The data on periodontal regeneration and wound healing have evolved greatly in light of several factors, including space for blood clots and blood clot stabilization. In periodontal osseous defects, the stability of blood clots seems critical to wound healing. If mechanical forces can be managed by wound stabilization, the gingival flap-tooth root interface may show connective tissue repair. However, compromised adhesion is susceptible to mechanical forces and can cause wound breakage and epithelialization.

CONCLUSION

The presence of a thick blood clot may hinder the plasmatic circulation between the recipient bed and graft during the initial stage of healing, which is critical in cases of mucogingival surgery. Root conditioning can also determine the healing consequence by enhancing blood clot adhesion.

Reconstructive surgical treatment of isolated deep intrabony defects with guided tissue regeneration using entire papilla preservation technique: A prospective case series

BACKGROUND

The aim of this prospective study is to evaluate the clinical applicability of the entire papilla preservation (EPP) technique in the regenerative treatment of isolated deep intrabony defects using native collagen membrane and bone grafting materials.

METHODS

Fifteen healthy and non-smoker patients (nine males and six females; mean age: 47.73 ± 12.18; range 21 to 63 years) with one isolated deep intrabony defect each (baseline probing depth (PD): 9.03 ± 1.62 mm; clinical attachment level (CAL): 11.16 ± 1.81 mm) were treated with guided tissue regeneration. Surgical access to the defect was provided by a single buccal vertical incision with an interdental tunneling flap. Following the granulation tissue removal, intrabony defect was filled with bone substitutes. A collagen barrier was trimmed and placed under the intact defect-associated papilla with palatal positioning suture. Microsurgical sutures were used for primary closure.

RESULTS

At 1 week, healing of the 15 sites was uneventful. During the study, all sites showed 100% primary closure rate. At 1-year follow-up, an average CAL gain of 5.86 ± 1.28 mm (P < 0.0001), PD reduction of 6.1 ± 1.47 mm (P < 0.0001), and minimal increase in gingival recession of 0.23 ± 0.62 mm (P = 0.168) were observed.

CONCLUSION

This novel surgical technique, that keeps the interdental papilla intact, seems promising to provide optimal biomaterial protection and healing conditions, even when a collagen barrier and bone substitutes are applied.

Degradation, Bone Regeneration and Tissue Response of an Innovative Volume Stable Magnesium-Supported GBR/GTR Barrier Membrane

Introduction: Bioresorbable collagenous barrier membranes are used to prevent premature soft tissue ingrowth and to allow bone regeneration. For volume stable indications, only non-absorbable synthetic materials are available. This study investigates a new bioresorbable hydrofluoric acid (HF)-treated magnesium (Mg) mesh in a native collagen membrane for volume stable situations. Materials and Methods: HF-treated and untreated Mg were compared in direct and indirect cytocompatibility assays. In vivo, 18 New Zealand White Rabbits received each four 8 mm calvarial defects and were divided into four groups: (a) HF-treated Mg mesh/collagen membrane, (b) untreated Mg mesh/collagen membrane (c) collagen membrane and (d) sham operation. After 6, 12 and 18 weeks, Mg degradation and bone regeneration was measured using radiological and histological methods. Results: In vitro, HF-treated Mg showed higher cytocompatibility. Histopathologically, HF-Mg prevented gas cavities and was degraded by mononuclear cells via phagocytosis up to 12 weeks. Untreated Mg showed partially significant more gas cavities and a fibrous tissue reaction. Bone regeneration was not significantly different between all groups. Discussion and Conclusions: HF-Mg meshes embedded in native collagen membranes represent a volume stable and biocompatible alternative to the non-absorbable synthetic materials. HF-Mg shows less corrosion and is degraded by phagocytosis. However, the application of membranes did not result in higher bone regeneration.

Periodontal reconstructive surgery of deep intraosseous defects using an apical approach. Non-incised papillae surgical approach (NIPSA): A retrospective cohort study

BACKGROUND

The objective of this study was to compare a minimally-invasive surgical technique (MIST) and a non-incised papilla surgical approach (NIPSA) in periodontal reconstructive surgery of deep intraosseous defects.

METHODS

Data on 30 patients with a deep intraosseous defect treated with MIST (n = 15) or NIPSA (n = 15) were analyzed retrospectively. All patients met the same inclusion criteria and were treated following the same protocol, except for the surgical management of soft tissue (MIST versus NIPSA). Clinical parameters at baseline and at 1-year post-surgery, early healing at 1 week, and postoperative pain were assessed.

RESULTS

NIPSA and MIST resulted in significant clinical attachment gain (CAG) (P < 0.001) and probing depth reduction (PDr) (P < 0.001) at 1-year post-surgery. However, NIPSA resulted in significantly lower recession of the tip of the interdental papilla compared with MIST (P < 0.001). Smoking negatively influenced early healing in both techniques (P < 0.05).

CONCLUSIONS

NIPSA and MIST both resulted in significant improvements in clinical parameters. NIPSA showed significant soft tissue preservation. NIPSA may represent a promising papillae preservation technique in the treatment of intraosseous periodontal defects.

A multilevel modelling solution to mathematical coupling

Owing to mathematical coupling, statistical analyses relating change to baseline values using correlation or regression are erroneous, where the statistical procedure of testing the null hypothesis becomes invalid. Alternatives, such as Oldham’s method and the variance ratio test, have been advocated, although these are limited in the presence of measurement errors with non-constant variance. Furthermore, such methods prohibit the consideration of additional covariates (e.g., treatment group within trials) or confounders (e.g., age and gender). This study illustrates the more sophisticated approach of multilevel modelling (MLM) which overcomes these limitations and provides a comprehensive solution to the analysis of change with respect to baseline values. Although mathematical coupling is widespread throughout applied research, one particular area where several studies have suggested a strong relationship between baseline disease severity and treatment effect is guided tissue regeneration (GTR) within dental research. For illustration, we use GTR studies where the original data were found to be available in the literature for reanalysis. We contrast the results from an MLM approach and Oldham’s method with the standard (incorrect) approach that suffers from mathematical coupling. MLM provides a robust solution when relating change to baseline and is capable of simultaneously dealing with complex error structures and additional covariates and/or potential confounders.

Impact of smoking on guided tissue regeneration using a biocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite with a rubber dam as an alternative barrier

The purpose of our study was to critically evaluate the results obtained from a guided tissue regeneration technique after 12 months using a bocomposite poly (lactic-co-glycolic) acid/sub-micron size hydroxyapatite (PLGA/HA) with a rubber dam as a barrier in smoking and non-smoking patients. We selected 36 patients (18 current smokers and 18 non-smokers) diagnosed with chronic advanced periodontitis with a periodontal site (probing depth [PD] >5) amenable to regenerative surgery. Twelve months after surgery, the periodontal parameters were found to have statistically improved, when non-smokers were compared with smokers, in: PD reduction (6.3 ± 2.1 mm vs. 3.6 ± 1.9 mm); CAL gain (4.4 ± 1.1 vs. 2.8 ± 2.2 mm); recession (1.8 ± 1.4 mm vs. 0.8 ± 0.9 mm); and hard tissue fill (4.7 ± 0.8 mm vs. 2.8 ± 2.1 mm). Furthermore, since we found PD baseline differences between groups, smoking seemed not to influence the outcomes achieved (CAL gain and ΔREC) 12 months post surgery with respect to PD baseline. The use of PLGA/HA with a rubber dam significantly improved the periodontal parameters in both smoking and non-smoking subjects. This improvement was nevertheless lower in smokers than the non-smokers, confirming the negative impact of smoking on periodontal regeneration.

Influence of a collagen membrane and recombinant platelet-derived growth factor on vertical bone augmentation in implant-fixed deproteinized bovine bone--animal pilot study

OBJECTIVES

Combinations of bone substitute block materials with membrane techniques as well as with growth factors are possible options to enhance the prognosis of vertical bone augmentation. Therefore, the aim of the pilot study was to compare the influence of a collagen membrane and a signal protein (rhPDGF-BB) on vertical bone augmentation with a stable fixed block material (deproteinized bovine bone [DBB]).

MATERIALS AND METHODS

In 12 rabbits, a DBB-block was implant-fixed on the tibia in a split-leg-design. Included were: DBB only (control), DBB + collagen membrane (test), DBB + rhPDGF-BB (test) and DBB + rhPDGF-BB + collagen membrane (test). 24 samples were examined after 3 (n = 12) and 6 weeks (n = 12). Calculated parameters were new bone area (NBA;%), new vertical bone height (VBH; mm). Due to the pilot character of this study, single values are shown descriptively only.

RESULTS

After 3 weeks, there were constant higher NBA values in the rhPDGF-BB-group without membrane (NBA (%) DBB: 30/16/4; DBB + membrane: 25/17/7, DBB + rhPDGF-BB: 40/33/34, DBB + rhPDGF-BB + membrane: 0/30/16; VBH (mm) DBB: 1.2/1.2/1, DBB + membrane: 0.7/0.9/1, DBB + rhPDGF-BB: 0.7/0.9/1, DBB + rhPDGF-BB + membrane: 0/1.1/1). After 6 weeks, both membrane groups showed a constant higher NBA and VBH independent to the use of rhPDGF-BB (NBA DBB: 3/0/5, DBB + membrane: 20/35/31, DBB + rhPDGF-BB: 5/8/4, DBB + rhPDGF-BB + membrane: 31/35/40; VBH DBB: 0.3/0.3/0.6, DBB + membrane: 1.6/2.4/2.1, DBB + rhPDGF-BB: 0.4/0.7/0.8, DBB + rhPDGF-BB + membrane: 1.8/2/1.8).

CONCLUSIONS

For vertical augmentation, the addition of rhPDGF-BB to DBB-blocks may increase early bone growth. In the later phase, the use of a collagen membrane enhances new bone volume and height to a significant greater extend. Even if the results are higher than those in the non-membrane groups, the low gain of bone after the short time periods still needs improvement.

Minimally invasive periodontal therapy

Minimally invasive dentistry is a concept that preserves dentition and supporting structures. However, minimally invasive procedures in periodontal treatment are supposed to be limited within periodontal surgery, the aim of which is to represent alternative approaches developed to allow less extensive manipulation of surrounding tissues than conventional procedures, while accomplishing the same objectives. In this review, the concept of minimally invasive periodontal surgery (MIPS) is firstly explained. An electronic search for all studies regarding efficacy and effectiveness of MIPS between 2001 and 2009 was conducted. For this purpose, suitable key words from Medical Subject Headings on PubMed were used to extract the required studies. All studies are demonstrated and important results are concluded. Preliminary data from case cohorts and from many studies reveal that the microsurgical access flap, in terms of MIPS, has a high potential to seal the healing wound from the contaminated oral environment by achieving and maintaining primary closure. Soft tissues are mostly preserved and minimal gingival recession is observed, an important feature to meet the demands of the patient and the clinician in the esthetic zone. However, although the potential efficacy of MIPS in the treatment of deep intrabony defects has been proved, larger studies are required to confirm and extend the reported positive preliminary outcomes.

Randomized controlled trial on lateral augmentation using two collagen membranes: morphometric results on mineralized tissue compound

BACKGROUND

Guided bone regeneration is considered an effective tool for gaining mineralized tissue either at exposed implant surface or in deficient alveolar ridge areas before implant placement.

MATERIAL AND METHODS

Customized casts obtained following impression taking at surgery and re-entry allowed for morphometric assessment of alveolar ridge alterations 6 months after one-stage augmentation of bone dehiscences. In a randomized pilot study using biphasic calcium phosphate tests (n=17) received treatment with ribose cross-linked collagen membranes (RCLM), whereas controls (n=20) received non-cross-linked membranes. The primary endpoint was to quantify the effect of membrane type on dimensional changes in bone margins at crestal level of endosseous implants.

RESULTS

Soft tissue dehiscencies occurred at 70.5% and 55% frequency for tests and controls, respectively. Gain in clinically hard newly mineralized tissue at the crestal level was significantly higher in test group in lateral (1.8 versus 0.7 mm; p=.046) and in vertical dimensions (1.1 versus 0.2 mm; p=.035) compared with controls. Second measurement obtained at the border of reflected flap revealed no significant difference between groups (3.0 versus 2.1 mm; p=0.57) for lateral dimension.

CONCLUSIONS

Both collagen devices were effective in bone augmentation. RCLMs supported mineralization process and remodelling even in sites showing compromised healing as indicated by morphometric outcome.

Regeneration of periodontal tissues: guided tissue regeneration

The concept that only fibroblasts from the periodontal ligament or undifferentiated mesenchymal cells have the potential to re-create the original periodontal attachment has been long recognized. Based on this concept, guided tissue regeneration has been applied with variable success to regenerate periodontal defects. Quantitative analysis of clinical outcomes after guided tissue regeneration suggests that this therapy is a successful and predictable procedure to treat narrow intrabony defects and class II mandibular furcations, but offers limited benefits in the treatment of other types of periodontal defects.

Bacterial penetration through antibiotic-loaded guided tissue regeneration membranes

BACKGROUND

This study compared bacterial penetration through guided tissue regeneration (GTR) membranes impregnated with antibiotics.

METHODS

Three barrier membranes, expanded polytetrafluoroethylene (ePTFE) membrane, collagen membrane, and glycolide fiber composite membrane, were loaded with amoxicillin or tetracycline. The penetration of Streptococcus mutans and Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans) through the GTR membranes was achieved using a device consisting of an inner tube and an outer bottle filled with culture media.

RESULTS

The penetration of S. mutans or A. actinomycetemcomitans into the inner tubes significantly decreased with all of the antibiotic-loaded membranes compared to membranes without antibiotics. However, differences were found in the behavior of the three membranes. The antibiotic-loaded ePTFE membranes showed the best barrier effect. Moreover, the inhibitory effect of tetracycline on S. mutans was greater than that of amoxicillin for all GTR membranes. Furthermore, the inhibitory effect of tetracycline on A. actinomycetemcomitans was lower than that of amoxicillin with the glycolide fiber membrane.

CONCLUSIONS

The results showed that penetration of S. mutans and A. actinomycetemcomitans through amoxicillin- or tetracycline-loaded ePTFE membrane, glycolide fiber membrane, and collagen membrane was delayed and/or reduced. Thus, incorporation of an antibiotic into the membrane may be of value when controlling membrane-associated infection during GTR therapy.

Long-term clinical evaluation and SEM analysis of the e-PTFE and titanium membranes in guided tissue regeneration

AIM

This study aimed to evaluate clinical outcomes of titanium membrane and compare these findings with clinical outcomes of e-PTFE membrane, and to investigate the effect of bacterial contamination on both membranes with SEM during long-term healing.

RESULTS

Sixteen titanium and sixteen e-PTFE membranes were surgically placed adjacent to periodontally involved teeth. Seven titanium and 8 e-PTFE membranes were exposed between 4 and 6 weeks. There were no significant difference between groups for plaque and gingival index. Probing depth and clinical attachment level (CAL) were decreased in both groups when compared with baseline; however, these differences were not statistically significant. The CAL gains between the groups were statistically different in 3rd, 6th, 9th, 12th, and 24th months (p < 0.05), and the CAL gain was significantly higher in titanium membrane (p < 0.05). There was significant decrease in bleeding on probing from baseline in both groups (p < 0.05). Surfaces of 15 membranes were studied using SEM. The largest amount of bacteria was found on the external cervical surfaces of 15 exposed specimens. The entire surface showed the presence of slough epithelial cells, leukocytes, red blood cells, yeast, and microbial plaque. Thirteen external mid surfaces of the 15 specimens, external apical surfaces of three e-PTFE and 1 titanium membrane, internal collar surfaces of all specimens, internal mid surfaces of 5 e-PTFE and three titanium membranes and internal apical surface of only one e-PTFE membrane were infected.

CONCLUSIONS

This study demonstrated that titanium membrane is equivalent to e-PTFE membranes for GTR in the treatment of periodontal defects.

Degradation of collagen-guided tissue regeneration membranes by proteolytic enzymes of Porphyromonas gingivalis and its inhibition by antibacterial agents

Previous studies have shown that whole cells of several periodontal pathogenic bacteria including Porphyromonas gingivalis may degrade the clinically used regeneration membranes Biomend Extend and Bio-Gide. Fractionation of P. gingivalis cells revealed that cell membrane-associated proteases are responsible for the in vitro degradation of the collagen membranes. In the present study, the specific role of extracellular vesicles and the purified Arg-gingipain enzyme of P. gingivalis in the degradation of three differently cross-linked collagen membranes (Ossix; Bio-Gide and Biomend Extend) was examined. In addition, the inhibitory effect of antibacterial agents and antibiotics used in local periodontal therapy on the enzymatic degradation was evaluated. The data presented show that while all tested collagen membranes, are prone to lysis by oral bacterial proteases, cross-linked membranes are more resistant to proteolysis. Furthermore, therapeutical concentrations of the antibacterial and antibiotic agents chlorhexidine, cetylpyridiniumchloride, minocycline and doxycycline were found to partially inhibit the enzymatic breakdown of the membranes, while metronidazole had no such effect. These results suggest that the presence of P. gingivalis cells, extracellular vesicles and enzymes in the vicinity of regeneration membranes in the periodontium, may change their physical structure and therefore alter their biological properties. Furthermore, the use of cross-linked collagen membranes and antibacterial agents may significantly inhibit this proteolytic process.

Biodegradation of three different collagen membranes in the rat calvarium: a comparative study

BACKGROUND

Collagen barrier membranes are commonly applied in periodontal and bone-regenerative procedures. Membranes differ in their resorption pattern following implantation, thus influencing clinical outcome. The purpose of this study was to quantitatively evaluate the biodegradation of three different commercially available collagen membranes.

METHODS

Collagen membranes were cut into 5-mm-diameter disks and labeled with aminohexanoyl-biotin-N-hydroxy-succinimide ester. One membrane disk of each type (non-cross-linked [NCL], glutaraldehyde cross-linked [GCL], and ribose cross-linked [RCL]) was implanted on the calvaria of 20 Wistar rats. Block sections were retrieved after 2 days (baseline, two animals), 14 days (10 animals), or 28 days (eight animals). Decalcified histologic sections were stained with streptavidin horseradish peroxidase. Residual membrane thickness and area were measured. Statistical analysis consisted of analysis of variance (ANOVA) with repeated measures.

RESULTS

Statistically significant differences in the amount of residual membrane material were recorded within each membrane (among different time points) and among different membranes at the same time points (P <0.001). At 28 days, the least amount of residual collagen area, expressed as the percentage of baseline, was observed in the NCL group (13.9% +/- 10.25%), followed by the GCL (24.7% +/- 35.11%) and RCL (91.3% +/- 10.35%) groups. Residual membrane thickness, expressed as the percentage of baseline thickness, presented a similar pattern (31% +/- 16.55%, 37% +/- 41.90%, and 94.1% +/- 12.22%, respectively). ANOVA with repeated measures showed a significant interaction between membranes and time (P <0.001).

CONCLUSIONS

The tested membranes differed in their degradation patterns and collagen contents. Membranes should be chosen for each clinical case according to the desired biodegradation characteristics.

Characterization and Antibacterial Effect of a Novel Nanocomposite Membrane

In this experiment, un-dried silver-hydroxyapatite-titania nanoparticles slurry was used to make membrane with Polyamide-66 by co-polymerization method. The morphology, chemical components and structures of the membrane were characterized by AAS, XRD, SEM and EDX. S. aureus, E. eoli, P.gingivalis, F.nucleatum and S.mutans were utilized to test the antibacterial effect. XRD results demonstrated that the membrane have characteristic diffraction peaks of pure HA. A homogeneous distribution of the Ca, P, Ti, and Ag element in the membrane was confirmed by EDX. Both surface and section showed porous structure which was confirmed by SEM and the holes size was average 20-30μm. The bacteria assay reflects to the antibacterial effect, 56.31 % of S. aureus and 50.10 % of E. eoli were killed after 24 hours incubation. However, 91.84 % of P. gingivalis, 90.64 % of F. nucleatum and 90.49 % of S. mutans were killed and pictures of SEM showed obviously fewer cells on the surface. So the nanocomposite membrane could be one of the bioactive materials with antibacterial properties for oral GBR technique.

A minimally invasive surgical technique with an enamel matrix derivative in the regenerative treatment of intra-bony defects: a novel approach to limit morbidity

AIMS

This study was undertaken to describe a new surgical approach (minimally invasive surgical technique, MIST) and to evaluate preliminarily its clinical performance and patient perception associated with the application of enamel matrix derivative (EMD) in the treatment of isolated deep intra-bony defects.

METHODS

Thirteen deep isolated intra-bony defects in 13 patients were surgically accessed with the MIST. This technique was designed to limit the mesio-distal flap extension and the corono-apical reflection in order to reduce the surgical trauma and increase flap stability. The incision of the defect-associated papilla was performed according to the principles of the papilla preservation techniques. EMD was applied on the debrided root surfaces. Stable primary closure of the flaps was obtained with internal modified mattress sutures. Surgery was performed with the aid of an operating microscope and microsurgical instruments. Clinical outcomes were collected at baseline and at 1 year. Intra-operative and post-operative patient perception was also recorded.

RESULTS

Early wound healing was uneventful: primary wound closure was obtained and maintained in all sites with the exception of one site with a small wound dehiscence at week 1. No oedema or haematoma were noted. Patients did not report any pain. Three patients experienced slight discomfort for 2-days post-operatively. The 1-year clinical attachment level (CAL) gain was 4.8+/-1.9 mm. The 1-year percent resolution of the defect was 88.7+/-20.7%, and reached 100% of the baseline intra-bony component in seven sites. Residual probing depths (PD) were 2.9+/-0.8 mm. Differences between baseline and 1-year CAL and PD were both clinically and statistically highly significant (p<0.0001). A minimal increase of 0.1+/-0.9 mm in gingival recession between baseline and 1 year was recorded (p=0.39).

CONCLUSIONS

This case cohort indicates that MIST associated with EMD resulted in excellent clinical improvements while limiting patient morbidity. These preliminary findings need to be confirmed in a larger study.

The papilla amplification flap for the treatment of a localized periodontal defect associated with a palatal groove

BACKGROUND

Teeth with a palatal groove often present with severe localized periodontal attachment loss including pocket formation and alveolar bone loss. The aim of the present case report was to describe the regenerative surgical treatment of periodontal and bone lesions associated with the subgingival extension of a palatal groove affecting a maxillary lateral incisor.

METHODS

The left maxillary lateral incisor of a systemically healthy young subject presented with a palatal probing depth of 10 mm with no gingival recession at the buccal and palatal surfaces; the neighboring interdental papillae were intact. The radiograph showed a radiolucency area distal to the affected tooth. Treatment procedures consisted of: 1) the papilla amplification flap with the use of enamel matrix proteins as the regenerative periodontal material; 2) the elimination/flattening of the radicular portion of the palatal groove; and 3) the sealing of the coronal portion of the groove with composite flow.

RESULTS

The clinical examination at 1 year revealed a clinical attachment gain (8 mm) with a shallow residual probing depth (2 mm) and no increase in gingival recession. The radiographic examination showed the complete disappearance of the radiolucency area suggesting bone fill.

CONCLUSIONS

The present study indicated that localized periodontal defects associated with a palatal groove can be successfully treated by means of the papilla amplification flap with the use of enamel matrix protein as the regenerative material. The long-term stability of such successful results needs to be determined.

Reconstructive periodontal surgery: A challenge for modern periodontology

The overall rationale for the proposed clinical approach in this paper comes from consideration of different regenerative approaches reported in the literature. The protocol proposed is based mainly on evidence and partly on the clinical experience of the author and co-workers, who have found that patient associated factors such as plaque control, residual periodontal infection, and smoking habits are those of particular relevance. Among the technical/surgical associated factors, lack of primary closure of the interdental space and consequent bacterial contamination of the regenerating wound represent the most significant factors leading to compromised outcomes. Modified flap designs and a microsurgical approach have been shown to improve the outcomes. There is now sufficient evidence to suggest that clinicians can incorporate periodontal regeneration in their surgical armamentarium. Periodontal regeneration can be predictably used to treat deep pockets associated with deep intrabony defects in young and old people, aimed at pocket/defect resolution with aesthetic preservation, gain of clinical attachment and bone.

A resin-modified glass ionomer cement barrier for treating degree II furcation defects: a pilot study in dogs

OBJECTIVE

The aim of this study was to evaluate in an animal model the healing of degree II furcation defects treated with: an experimental barrier of resin-modified glass-ionomer cement (GIC), a polylactic acid barrier (GUI), and flap surgery (CTR).

MATERIAL AND METHODS

In 3 beagles, 18 class II furcation defects were surgically produced in mandibular and maxillary premolars and exposed to plaque accumulation for 21 days. Following a full flap, notches were made at the base to the bone defect. GIC barriers were prepared immediately before use from a commercial product and fit to place with the same product. The GIC barriers were removed after 30 days and the dogs euthanized after 120 days. Histologic sections were analyzed in a computer-assisted microscope. Epithelium, new cementum with inserting fibers, and connective tissue lining the root surface in-between notches were measured and medians of percentage values calculated.

RESULTS

In the GIC, epithelium constituted 3.5% (median values) of the notch-to-notch root area; new cementum was 83.6% and connective tissue 12.9%. These values were 0%, 73.6%, and 26.4% for the GUI group and 35.6%, 43.2%, and 0% for the CTR group. Bone fill median values were 54.3% for GIC, 20.6% for GUI, and 24.6% for CTR.

CONCLUSION

GIC and GUI prevented epithelial migration and promoted the formation of new periodontal tissues in experimentally induced class II furcation defects in dogs.

Improved drug delivery properties of PVDF membranes functionalized with β-cyclodextrin—Application to guided tissue regeneration in periodontology

The purpose of this study was to develop a membrane for guided tissue regeneration applicable in periodontology that could release antimicrobial agent during the healing period. Our strategy consisted to graft beta-cyclodextrin (beta-CD), a molecule that is known to form inclusion complexes with a large variety of drugs, onto PVDF membranes. Grafting occurred by using citric acid that provoked a crosslinking reaction of beta-CD, and the resulting polymer was imprisoned into the porous structure of the PVDF membrane. The reaction produced a weight increase of the membrane, the range of which depended on the temperature and on the time of curing applied in the process. The biological behavior of the membranes evaluated by proliferation and vitality tests showed good proliferation and improved activity of L132 epithelial cells on the raw and on the grafted membranes. Doxycyclin (DOX) and chlorhexidine (CHX) were used as antimicrobial agents. Their inclusion into the beta-CD cavity in aqueous solutions was confirmed by NMR spectroscopy. After the impregnation of the membranes with DOX and CHX, their release was studied in vitro in batch type experiments and measured by UV spectrophotometry. Low amounts of DOX and CHX were delivered from the raw membranes within the first few hours of tests. Grafted membranes, however, delivered DOX and CHX in larger quantities within 24 h and 10 days respectively.

The problem of analysing the relationship between change and initial value in oral health research

The relationship between initial disease status and subsequent change following treatment has attracted great interest in dental research. However, medical statisticians have repeatedly warned against correlating/regressing change with baseline because of two methodological concerns known as mathematical coupling and regression to the mean. In general, mathematical coupling occurs when one variable directly or indirectly contains the whole or part of another, and the two variables are then analyzed by using correlation or regression. Consequently, the statistical procedure of testing the null hypothesis - that the coefficient of correlation or the slope of regression is zero - may become inappropriate. Regression to the mean occurs with any variable that fluctuates within an individual or a population, either owing to measurement error and/or to physiological variation. The aim of this article was to clarify the conceptual confusion around mathematical coupling and regression to the mean within the statistical literature, and to correct a popular misconception about the correct analysis of the relationship between change and initial value. As examples that use inappropriate methods to analyze the relationship between change and baseline are still found in leading dental journals, this article seeks to help oral health researchers understand these problems and explain how to overcome them.

Regeneration of class II furcation defects: determinants of increased success

One of the most important indications for guided tissue regeneration (GTR) treatment is class II furcation lesion. However, periodontal regeneration of this type of defect, although possible, is not considered totally predictable, especially in terms of complete bone fill. Many factors may account for variability in the response to regenerative therapy in class II furcation. The purpose of this review is to assess the prognostic significance of factors related to the patient (smoking, stress, diabetes mellitus, acquired immunodeficiency syndrome and other acute and debilitating diseases, and the presence of multiple deep periodontal pockets), local factors (furcal anatomy, defect morphology, thickness of gingival tissue and tooth mobility), surgical treatment (infection control, bone replacement grafts combined with barriers or GTR alone, type of barrier and surgical technique), and postoperative period (plaque control, membrane exposure, membrane retrieval and a regular supportive periodontal care program) for successful of GTR in class II furcations.

Microvascular Response in the Periosteum Following Mucoperiosteal Flap Surgery in Dogs: 3-Dimensional Observation of an Angiogenic Process

BACKGROUND

An increase in blood flow from the periosteum after mucoperiosteal flap surgery is essential for healing and angiogenesis and repair may work in close cooperation to facilitate this process. To investigate the role of the periosteal vascular plexus in the healing process, we used 3-dimensional (3-D) and ultrastructural monitoring of the angiogenic process after elevation of the mucoperiosteal flap.

METHODS

Mucoperiosteal flap surgery was performed on nine adult beagle dogs. The periosteal vascular plexus was observed 3, 5, and 7 days after surgery in histological specimens in which blood vessels were injected with India ink under a light microscope, in ultrathin sections under a transmission electron microscope, and in acryl plastic vascular cast specimens under a scanning electron microscope.

RESULTS

On day 3 after surgery, new blood vessels, formed through sprouting, bridging, and intussusception, were observed in ultrathin sections and vascular casts. In addition, blood island-like structures consisting of clustered immature endothelial cells were noted in the repaired tissue. On days 5 to 7 after surgery, 3-D observation of vascular casts clarified that these new blood vessels had a sinus-like morphology in the interstitium of the periosteal vascular plexus. These new sinusoidal vessels exhibited a stereoscopic structure with increased continuity as the blood vessels matured and ultrastructurally the vascular endothelium was thinned.

CONCLUSIONS

After mucoperiosteal flap elevation, the periosteal vasculature exhibited potent blood vessel-forming activity through various angiogenic mechanisms and through repair activity. Our results provide a 3-dimensional clarification that the periosteal vascular plexus has an important role in the healing process after flap surgery.

The relationship between baseline value and its change: problems in categorization and the proposal of a new method

Oral health researchers have shown great interest in the relationship between the initial status of diseases and subsequent changes following treatment. Two main approaches have been adopted to provide evidence of a positive association between baseline values and their changes following treatment. One approach is to use correlation or regression to test the relationship between baseline measurements and subsequent change (correlation/regression approach). The second approach is to categorize the lesions into subgroups, according to threshold values, and subsequently compare the treatment effects across the two (or more) subgroups (categorization approach). However, the correlation/regression approach suffers a methodological weakness known as mathematical coupling. Consequently, the statistical procedure of testing the null hypothesis becomes inappropriate. Categorization seems to avoid the problem of mathematical coupling, although it still suffers regression to the mean. We show, first, how the appropriate null hypothesis may be established to analyze the relationship between baseline values and change in the correlation approach and, second, we use computer simulations to investigate the impact of regression to the mean on the significance testing of the differences in the average treatment effects (or average baseline values) in the categorization approach. Data available from previous literature are reanalyzed by testing the appropriate null hypotheses and the results are compared to those from testing the usual (incorrect) null hypothesis. The results indicate that both the correlation and categorization approaches can give rise to misleading conclusions and that more appropriate methods, such as Oldham's method and our new approach of deriving the correct null hypothesis, should be adopted.

Healing of dehiscence-type defects in implants placed together with different barrier membranes: a comparative clinical study

OBJECTIVE

Premature exposure of membranes used in guided bone regeneration (GBR) results in decreased bone formation. The effect of an expanded polytetrafluoroethylene (e-PTFE) and two collagen membrane on bone healing of buccal dehiscence defects around implants in cases with and without premature membrane exposure was clinically evaluated.

METHODS

Three groups were established: Group OS (Ossix, n=73 implants, 41 patients), Group BG (Bio-Gide, n=53 implants, 28 patients) and Group GT (e-PTFE, Gore-Tex, n=34 implants, 17 patients). Defect height and width were measured at the time of implant placement and at second stage surgery. Surface area was calculated as half ellipses. When several implants were placed simultaneously, a mean of their defect width and height was calculated.

RESULTS

Mean percentage reduction of defect area (92.2+/-13.78% Group OS, 94.6+/-6.69% Group BG, and 97.3+/-4.91% Group GT) and height (81.6+/-23.19%, 85.4+/-12.26%, and 93.4+/-9.39% respectively) did not show statistically significant differences between groups. Differences between groups were not statistically significant for all parameters when cases without spontaneous membrane exposure were compared. However, differences were significant when spontaneous membrane exposure occurred. Mean percentage reduction of defect area among cases where membrane exposure occurred was 91.5+/-10.86% Group OS, 71.5+/-8.61% Group BG, and 73.7+/-13.97% Group GT. Mean percentage reduction of defect height among cases with membrane exposure was 76.4+/-18.28%, 53.4+/-9.86%, and 49.4+/-11.05%, respectively.

CONCLUSIONS

Premature exposure of membranes and subsequent and consequent exposure of implants results in impaired bone healing. Certain barrier membranes, as used in group OS, are apparently capable of supporting gingival healing even when prematurely exposed that could be advantageous in GBR procedures.

Clinical Performance of a Regenerative Strategy for Intrabony Defects: Scientific Evidence and Clinical Experience

BACKGROUND

The aim of the present study was to evaluate the clinical performance of a regenerative strategy for the treatment of deep intrabony defects.

METHODS

This patient cohort study involved 40 patients with one deep interdental intrabony defect each. They were treated with periodontal regeneration using four different regenerative methods (expanded polytetrafluoroethylene [ePTFE] titanium reinforced membranes, bioabsorbable membranes alone, bioabsorbable membranes with a bone replacement graft [combination], or enamel matrix derivative), according to predefined criteria and decision-making algorithms. Defects were accessed with papilla preservation flaps performed with the aid of an operating microscope and microsurgical instruments. A stringent plaque control regimen was enforced in all the patients during the 1-year observation period. Outcomes included evaluation of the complete primary closure of the interdental space (CLOSURE), gains in clinical attachment (CAL), and reductions in probing depths (PD).

RESULTS

CLOSURE was achieved in all treated defects and was maintained in 90% of cases for the entire healing period. At 1 year the observed CAL gains were 6 +/- 1.8 mm on average, corresponding to a resolution of 92.1% +/- 12% of the initial intrabony (CAL%) component of the defect. Average PD reduction was 6.1 +/- 1.9 mm and was associated with minimal increase in gingival recession (-0.1 +/- 0.7 mm). The 12 sites treated with titanium reinforced ePTFE membranes resulted in a 1-year CAL gain of 6.8 +/- 2.2 mm (CAL%: 94.7 +/- 13.4); the 11 cases treated with combination therapy showed a 1-year CAL gain of 5.4 +/- 1.7 mm (CAL%: 88.2 +/- 9.6); the seven sites treated with bioabsorbable barriers resulted in 5.9 +/- 1.2 mm of CAL gain (CAL%: 88.9 +/- 11.5); and the 10 sites treated with enamel matrix gained on average 5.9 +/- 1.5 mm of CAL (CAL%: 88.9 +/- 11.5). No significant differences were observed among the four approaches.

CONCLUSION

The use of an evidence-based regenerative strategy resulted in clinically relevant amounts of CAL gains, shallow pockets, and minimal gingival recession with the four regenerative approaches.

The drug delivery and biomaterial attributes of the ATRIGEL®technology in the treatment of periodontal disease

Two new products, ATRIDOX Periodontal Treatment and ATRISORB Guided Tissue Regeneration (GTR) Barrier have been evaluated as therapies for periodontal disease. Both products are based on the unique ATRIGEL technology. The system consists of a solution of a resorbable polymer in a biocompatible carrier. On in vivo administration, the polymer undergoes a phase change from a liquid to an in situ formed implant. Being in liquid form, it initially provides the advantage of in vivo placement by simple means, such as syringes to form implants at the site of use. The system is biocompatible and has the capability of serving as a biomaterial and a drug delivery system. The bioabsorption rates of various polymers and the release rates for a wide variety of drugs ranging from simple organics to proteins and peptides are tailored to the desired indication. Release periods ranging from one week to four months have been achieved with one month being the most often desired. For these reasons the ATRIGEL system is being applied to a number of medical applications ranging from site and systemic oncology to post-operative pain control and bone regeneration using growth factors. However, its most visible application to date has been in the development of a pipeline of products for the treatment of periodontal disease, which is the focus of this paper.

Radiographic parameters as prognostic indicators for healing of class II furcation defects

OBJECTIVE

To evaluate radiographic measurements for use as prognostic indicators for healing of class II furcation defects following regenerative therapy.

MATERIAL AND METHODS

In 17 patients (eight females), 33 class II furcation defects (mandibular buccal (n=10) and lingual (n=12), and maxillary buccal (n=11)) were treated using the barrier membrane technique. Twenty-six furcations were treated using a bioabsorbable membrane, while a nonresorbable membrane was used to treat the remaining seven furcation defects. Clinical parameters and standardized radiographs were obtained before as well as 6 and 24 months after therapy. All radiographs were digitized and evaluated by an examiner blinded to the clinical data. The following distances were measured: cemento-enamel junction line (CEJ-line) to alveolar crest (AC) at the furcation site (AC-CEJ line), CEJ-line to the furcation fornix (Fx-CEJ line), width of the furcation at the level of the AC (FW) as well as the distance from Fx to a straight line between the AC mesial and distal of the tooth (Fx-AC line).

RESULTS

Statistically significant (p<0.001) horizontal attachment gains could be observed 6 and 24 months after therapy (6 months: 1.49+/-0.85 mm; 24 months: 1.14+/-0.91 mm). However, a small but statistically significant (p=0.031) attachment loss of 0.35 mm was observed between the 6 and 24 months examination. Multilevel regression analyses identified baseline probing depth (p=0.0017) and 3 of the radiographic distances as prognostic factors: Fx-CEJ line (p=0.014), FW (p=0.0535), Fx-AC line (p=0.0827).

CONCLUSION

The analysis of presurgical radiographs may yield information on the success of the regenerative therapy of buccal and lingual class II furcation defects. A long root trunk, a wide furcation entrance and an Fx coronal to the AC have negative influences on the success of therapy. Further, a deep probing depth at the furcation site at baseline increases the likelihood for more favourable horizontal attachment gain in furcations.

Bacterial colonization during de novo plaque formation

OBJECTIVE

To determine microbial changes that occur during plaque formation in a dentition free of gingival inflammation.

MATERIAL AND METHODS

Ten subjects were recruited. The study included one preparatory period (2 weeks) and a plaque accumulation period (4 days). The volunteers exercised proper tooth cleaning methods, were scaled and received repeated professional mechanical tooth cleaning during the preparatory period. During the plaque accumulation period, the participants abstained from plaque control measures. Plaque was scored on the approximal surfaces of maxillary and mandibular premolars on Days 0, 1, 2 and 4 using a scale from 0 to 5 and according to the criteria of the Quigley and Hein Plaque Index (QHI). Supragingival plaque samples were obtained from the same intervals and surfaces and evaluated using a checkerboard DNA-DNA hybridization technique.

RESULTS

The mean QHI increased from 0 to 1.6 (Day 4). The total number of organisms on Day 0 averaged 140 x 10(5) and increased to about 210 x 10(5) after 4 days without oral hygiene. The most dominant species on Day 0 were members of the genus Actinomyces. These organisms comprised almost 50% of the microbiota evaluated. None of the Actinomyces species increased significantly during the 4 days. Some Streptococcus species increased significantly over time as well as species of the genera Capnocytophaga, Campylobacter, Fusobacteria and Actinomyces actinomycetemcomitans.

CONCLUSION

In the present investigation, the preparatory phase established a situation with minimal gingival inflammation and close to zero amounts of dental plaque. The Day 0 plaque samples exhibited high proportions of Actinomyces species. During the 4 days of no oral hygiene, there was a small increase in total numbers of organisms as well as a modest increase in the proportion of "disease-associated" taxa such as species of the "orange complex" species.

Effects of autoclave sterilization on properties of dental rubber dam as related to its use as barrier membrane in guided tissue regeneration

BACKGROUND AND OBJECTIVE

Dental rubber dams (RDs) were used as barrier membranes in guided tissue regeneration for the treatment of periodontal intraosseous defects with acceptable clinical results. The aim of the present study was to investigate the effects of autoclave sterilization on properties of RD as related to its use as a barrier membrane in guided tissue regeneration.

METHODS

RDs were sterilized by either an autoclave, gamma irradiation, or chemical agents and then co-cultured with human gingival fibroblasts. The cell responses to sterilized RDs were investigated by inverted phase contrast microscopy, scanning electron microscopy (SEM) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) technique. The surface alterations of the autoclaved RDs were observed under SEM. The tensile strength, tear strength and elongation at break of the autoclaved RDs were tested by a universal testing machine.

RESULTS

The results from cell culture, microscopic and MTT studies showed that RDs sterilized by autoclave and gamma irradiation did not deteriorate gingival fibroblasts and provided surfaces suitable for cell attachment, whereas chemical-sterilized RDs were toxic to these cells. Ultrastructurally, surface changes from the non-autoclaved RDs, including some melted areas, small pores and folds were observed on the autoclaved RD surface. The tensile strength and tear strength of the autoclaved RDs were significantly lower than those of the non-autoclaved RDs (p = 0.042, p < 0.001, respectively). In contrast, the elongation at break of the autoclaved RDs was higher than that of the non-autoclaved RDs (p < 0.001).

CONCLUSION

These results suggest that the autoclave sterilization deteriorated the physical properties of RDs even though they seemed to be compatible to the cultured human cells. Therefore, the sterilization method should be taken into consideration when RDs are utilized as barrier membranes.

Enzymatic degradation of collagen-guided tissue regeneration membranes by periodontal bacteria

Bacterial infection in the vicinity of guided tissue regeneration barrier membranes was shown to have a negative effect on the clinical outcomes of this increasingly used technique. Several oral and specifically periodontal bacteria were shown to adhere to such membranes in vivo and in vitro with a higher affinity to membranes constructed from collagen. The present study examined the role of periodontal bacteria and their enzymes in the degradation of commercially used collagen membranes. Degradation of two collagen membranes [Biomend (Calcitek, Colla-Tec Inc., Plainsboro, NJ) and Bio-Gide (Geistlich Biomaterials, Wolhousen, Switzerland)] labeled by fluorescein isothiocyanate was examined by measuring soluble fluorescence. Porphyromonas gingivalis, Treponema denticola and Actinobacillus actinomycetemcomitans and their enzymes were evaluated. Collagenase from Clostridium hystolyticum was used as a positive control. While whole cells of P. gingivalis were able to degrade both types of membranes, T. denticola could degrade Bio-Gide membranes only and A. actinomycetemcomitans whole cells could degrade none of the membranes. Fractionation of P. gingivalis cells revealed that cell membrane associated proteases were responsible for the degradation of the two collagen membranes. In T. denticola, the purified major phenylalanine protease was found to be responsible for the degradation of Bio-Gide membranes. These results suggest that proteolytic bacterial enzymes may take part in the degradation of collagen barrier membranes used for guided tissue regeneration.

Microsurgical access flap and enamel matrix derivative for the treatment of periodontal intrabony defects: a controlled clinical study

OBJECTIVES

Application of the guided tissue regeneration (GTR) principle and utilization of enamel matrix derivative (EMD) have both been shown to result in periodontal regeneration. While clinical investigations have demonstrated that the use of a microsurgical concept in combination with the GTR technique positively affects the percentage of primary closure and the amount of tissue preservation, no such information is available for EMD-treated periodontal defects. It was the aim of the present investigation to assess the clinical effect of the microsurgical access flap and EMD treatment with an emphasis on the evaluation of early wound healing.

MATERIAL AND METHODS

Eleven patients displaying at least one pair of intrabony periodontal defects with an intrabony component of > or =3 mm participated in the study. At baseline and at 6 and 12 months after surgery, the following clinical parameters were assessed by a blinded examiner: oral hygiene status (API), gingival inflammation (BOP), probing pocket depth (PPD), clinical attachment level (CAL) and gingival recession (GR). Defects were randomly assigned to test or control treatment, which both consisted of a microsurgical access flap procedure designed for maximum tissue preservation. The exposed root surfaces of the test sites were conditioned with a 24% EDTA gel followed by EMD (Emdogain(R)) application. Primary flap closure was achieved by a 2-layered suturing technique. Postoperative healing was evaluated by a newly introduced early wound-healing index (EHI) at 1 and 2 weeks after surgery.

RESULTS

Both test and control treatment resulted in a statistically significant mean CAL gain of 2.8 and 2.0 mm at 6 months, and 3.6 and 1.7 mm at 12 months, respectively (p<0.05). Differences in CAL gain between the two treatment modalities were statistically significant at both time points (p<0.05). Additional GR values after 12 months averaged 0.3 and 0.4 mm for test and control sites, respectively, and did not reach statistical significance (p> or =0.05). Two weeks after surgery, primary closure was maintained in 89% of the test sites and in 96% of the control sites.

CONCLUSION

Both treatment modalities using the microsurgical flap procedure resulted in a high percentage of primary flap closure and maximum tissue preservation. In terms of PPD reduction and CAL gain, the combination with EMD application appeared to be superior to the microsurgical access flap alone.

Guided tissue regeneration in smokers: effect of aggressive anti-infective therapy in Class II furcation defects

BACKGROUND

Guided tissue regeneration (GTR) using membrane barriers is still the reconstructive treatment of choice for a variety of periodontal defects. Smokers, however, present a reduced regenerative response to GTR. The purpose of the present study was to design and examine a new protocol with emphasis on anti-infective therapy for patients who are cigarette smokers and who require GTR procedures for the treatment of Class II furcation defects.

METHODS

Chronic periodontitis patients who were smokers and who exhibited mandibular Class II furcations were initially pooled for further assessment. Patients were randomly assigned to either the experimental group (EG) or a control group (CG). Clinical measurements and indices were recorded at baseline and at 6, 9, and 12 months, and included: plaque assessment index; gingival assessment index; probing depth; and probing attachment level (vertical [PAL-V] and horizontal [PAL-H]) using a prefabricated acrylic stent as a reproducible reference point. All patients underwent hygienic phase periodontal therapy. Next, GTR was performed, and the furcation dimensions (height, width, and depth) were measured. A membrane was placed, and a 25% metronidazole gel was then applied over the outer surface of the membrane (EG only) and the flaps repositioned so that the membrane was completely submerged. Instructions included twice daily rinses with chlorhexidine gluconate 0.2% for 1 week (CG) or as long as the membrane was in place (EG), doxycycline 100 mg x 1/day for 1 week (CG) or 6 to 8 weeks (EG), and ibuprofen 3 x 400 mg/day for 7 days. Patients were initially seen for prophylaxis weekly (EG) or biweekly (CG). Metronidazole was applied to the free gingival margins and/or over the exposed membrane at every prophylactic visit (EG). Six to 8 weeks after surgery, the membrane was removed surgically, and the amount of new tissue growth (NTG) from the cemento-enamel junction (CEJ) to the most coronal extension of the new tissue was recorded. Following membrane retrieval, patients were seen for prophylaxis and oral hygiene reinforcement every month (EG) or quarterly (CG). At 12 months postoperatively, the area was surgically reentered and the surgical measurements repeated.

RESULTS

Thirty-eight subjects, 21 females and 17 males, aged 35 to 61 were accepted in this study. Baseline clinical parameters were similar for both groups. One year postoperatively, there was no statistically significant difference in probing depth reduction or in horizontal PAL between EG and CG, but vertical PAL gain was significantly greater in EG. As for alveolar parameters 1 year postoperatively, the mid CEJ-crest distance and furcation width decreased in EG but increased in CG. A similar trend was observed for furcation height. Furcation depth reduction in both groups was similar. A comparison between new tissue growth at retrieval and eventual bone formation 1 year postoperatively demonstrated a smaller change in EG patients compared to CG patients, which was statistically significant for both the distal and the mid-tooth area, as well as for the tooth mean.

CONCLUSIONS

While smoking prevented tissue maturation and mineralization, the anti-infective protocol enhanced these processes, resulting in a more favorable outcome. It is therefore suggested that when GTR is performed for Class II furcation defects in smokers, anti-infective therapy should be incorporated into the treatment protocol to enhance the regenerative outcome in these patients.