Modulation of gene expression and bone formation by expanded and dense polytetrafluoroethylene membranes during guided bone regeneration: An experimental study.

BACKGROUND: Nonresorbable membranes promote bone formation during guided bone regeneration (GBR), yet the relationships between membrane properties and molecular changes in the surrounding tissue are largely unknown. AIM: To compare the molecular events in the overlying soft tissue, the membrane, and the underlying bone defect during GBR using dual-layered expanded membranes versus dense polytetrafluoroethylene (PTFE) membranes. MATERIALS AND METHODS: Rat femur defects were treated with either dense PTFE (d-PTFE) or dual-layered expanded PTFE (dual e-PTFE) or left untreated as a sham. Samples were collected after 6 and 28 days for gene expression, histology, and histomorphometry analyses. RESULTS: The two membranes promoted the overall bone formation compared to sham. Defects treated with dual e-PTFE exhibited a significantly higher proportion of new bone in the top central region after 28 days. Compared to that in the sham, the soft tissue in the dual e-PTFE group showed 2-fold higher expression of genes related to regeneration (FGF-2 and FOXO1) and vascularization (VEGF). Furthermore, compared to cells in the d-PTFE group, cells in the dual e-PTFE showed 2.5-fold higher expression of genes related to osteogenic differentiation (BMP-2), regeneration (FGF-2 and COL1A1), and vascularization (VEGF), in parallel with lower expression of proinflammatory cytokines (IL-6 and TNF-α). Multiple correlations were found between the molecular activities in membrane-adherent cells and those in the soft tissue. CONCLUSION: Selective surface modification of the two sides of the e-PTFE membrane constitutes a novel means of modulating the tissue response and promoting bone regeneration.

Early plaque formation on PTFE membranes with expanded or dense surface structures applied in the oral cavity of human volunteers.

OBJECTIVES: This clinical randomized study aimed to evaluate the early plaque formation on nonresorbable polytetrafluoroethylene (PTFE) membranes having either a dense (d-PTFE) or an expanded (e-PTFE) microstructure and exposed to the oral cavity. MATERIAL AND METHODS: Twelve individuals were enrolled in this study. In a split-mouth design, five test membranes (e-PTFE) with a dual-layer configuration and five control membranes (d-PTFE) were bonded on the buccal surfaces of posterior teeth of each subject. All study subjects refrained from toothbrushing during the study period. Specimens were detached from the teeth at 4 and 24 hr and subjected to viability counting, confocal microscopy, and scanning electron microscopy. Plaque samples were harvested from neighboring teeth at baseline, 4, and 24 hr, as control. Wilcoxon signed rank test was applied. RESULTS: No bond failure of the membranes was reported. Between the early and late time points, viable bacterial counts increased on all membranes, with no difference between the test and control. The number of Staphylococcus spp. decreased on the tooth surfaces and increased on both membranes overtime, with a significant difference compared to teeth. The total biomass and average biofilm thickness of live and dead cells were significantly greater at the d-PTFE barriers after 4 hr. CONCLUSION: This study demonstrated that the e-PTFE membrane was associated with a lesser degree of biofilm accumulation during the initial exposure compared to the d-PTFE membrane. The present experimental setup provides a valuable toolbox to study the in vivo behavior of different membranes used in guided bone regeneration (GBR).

Intra-surgical vs. radiographic bone level assessments in measuring peri-implant bone loss.

OBJECTIVE: To evaluate the accuracy between the intra-surgical and the peri-apical radiographic measurements of bone loss at implant with peri-implantitis. MATERIALS AND METHODS: A total of 46 Brånemark implants in 24 patients with diagnosis of peri-implantitis were included in the study. The amount of peri-implant bone loss occurred at those implants was measured during peri-implant surgery and compared to the radiographic bone loss measured by three independent examiners. RESULTS: The mean bone loss measured on radiographs underestimated the intra-surgical bone loss at the correspondent sites (0.7 mm at the mesial and 0.6 mm at the distal sites); this underestimation was found to be a consistent finding in all the three examiners. Only 21% of the radiographic measurements corresponded to the clinical bone loss assessments, while an over- and underestimation within a range of ± 1-2 mm was recorded in 57% of the cases. There was a moderate positive linear correlation between the radiographic measurements and the clinical bone loss for mesial and distal sites (r = range 0.58-0.65). The variability between the three examiners in the radiographic measurements was frequently on the range of ± 1-2 mm. CONCLUSION: The radiographic measurements of bone loss at implant affected by peri-implantitis often underestimated the clinical bone loss occurred at the implants. A difference of about ± 1-2 mm in the estimation of radiographic bone loss could be merely assigned as inter-examiner different assessments.

Guided bone regeneration is promoted by the molecular events in the membrane compartment.

The working hypothesis of guided bone regeneration (GBR) is that the membrane physically excludes non-osteogenic tissues from interfering with bone healing. However, the underlying mechanisms are insufficiently explained. This study aimed to investigate the molecular and structural pattern of bone healing in trabecular bone defects, with and without naturally derived resorbable membrane. Defects were created in rat femurs and treated with the membrane or left empty (sham). After 3d, 6d and 28d, the defect sites and membranes were harvested and analyzed with histology, histomorphometry, quantitative-polymerase chain reaction (qPCR), Western blot (WB) and immunohistochemistry (IHC). Histomorphometry demonstrated that the presence of the membrane promoted bone formation in early and late periods. This was in parallel with upregulation of cell recruitment and coupled bone remodeling genes in the defect. Cells recruited into the membrane expressed signals for bone regeneration (BMP-2, FGF-2, TGF-ß1 and VEGF). Whereas the native membrane contained FGF-2 but not BMP-2, an accumulation of FGF-2 and BMP-2 proteins and immunoreactive cells were demonstrated by WB and IHC in the in vivo implanted membrane. The results provide cellular and molecular evidence suggesting a novel role for the membrane during GBR, by acting as a bioactive compartment rather than a passive barrier.

Prevalence of Peri-implantitis in Medically Compromised Patients and Smokers: A Systematic Review.

PURPOSE: To verify whether the diversity of systemic medical conditions and smoking act as biologic associated factors for peri-implantitis. MATERIALS AND METHODS: The PICO question was: "In patients with osseointegrated dental implants, does the presence of smoking habits or a compromised medical status influence the occurrence of peri-implantitis compared with the presence of good general health?" Smoking and systemic conditions such as type 2 diabetes mellitus, cardiovascular diseases, rheumatoid arthritis, lung diseases, obesity, cancer, deep depression, and osteoporosis were screened. Selection criteria included at least 10 patients per condition, 1 year of follow-up after implant loading, and strict cutoff levels (probing pocket depth [PPD], bleeding on probing [BOP] and/or pus, marginal bone loss) to define peri-implantitis. RESULTS: From the 1,136 records initially retrieved, 57 were selected after title and abstract analyses. However, only six papers were considered for qualitative evaluation. No randomized controlled clinical trial was found. Smoking was associated with peri-implantitis in only one out of four studies. Poorly controlled type 2 diabetes accentuated only PPD and radiographic marginal bone level prevalence rates in peri-implant patients (one study). Cardiovascular disease was considered a risk (one out of two studies). The chance of peri-implant patients harboring the Epstein-Barr virus was threefold in one report. No associations were found for rheumatoid arthritis. CONCLUSION: Data from existing studies point to smoking and diabetes as biologic associated factors for peri-implantitis. However, the body of evidence is still immature, and the specific contribution of general health problems to peri-implantitis requires additional robust epidemiologic and clinical investigations.

Guided bone regeneration using resorbable membrane and different bone substitutes: Early histological and molecular events.

Bone insufficiency remains a major challenge for bone-anchored implants. The combination of guided bone regeneration (GBR) and bone augmentation is an established procedure to restore the bone. However, a proper understanding of the interactions between the bone substitute and GBR membrane materials and the bone-healing environment is lacking. This study aimed to investigate the early events of bone healing and the cellular activities in response to a combination of GBR membrane and different calcium phosphate (CaP) materials. Defects were created in the trabecular region of rat femurs, and filled with deproteinized bovine bone (DBB), hydroxyapatite (HA) or strontium-doped HA (SrHA) or left empty (sham). All the defects were covered with an extracellular matrix membrane. Defects were harvested after 12h, 3d and 6d for histology/histomorphometry, immunohistochemistry and gene expression analyses. Histology revealed new bone, at 6d, in all the defects. Larger amount of bone was observed in the SrHA-filled defect. This was in parallel with the reduced expression of osteoclastic genes (CR and CatK) and the osteoblast-osteoclast coupling gene (RANKL) in the SrHA defects. Immunohistochemistry indicated fewer osteoclasts in the SrHA defects. The observations of CD68 and periostin-expressing cells in the membrane per se indicated that the membrane may contribute to the healing process in the defect. It is concluded that the bone-promoting effects of Sr in vivo are mediated by a reduction in catabolic and osteoblast-osteoclast coupling processes. The combination of a bioactive membrane and CaP bone substitute material doped with Sr may produce early synergistic effects during GBR. STATEMENT OF SIGNIFICANCE: The study provides novel molecular, cellular and structural evidence on the promotion of early bone regeneration in response to synthetic strontium-containing hydroxyapatite (SrHA) substitute, in combination with a resorbable, guided bone regeneration (GBR) membrane. The prevailing view, based mainly upon in vitro data, is that the beneficial effects of Sr are exerted by the stimulation of bone-forming cells (osteoblasts) and the inhibition of bone-resorbing cells (osteoclasts). In contrast, the present study demonstrates that the local effect of Sr in vivo is predominantly via the inhibition of osteoclast number and activity and the reduction of osteoblast-osteoclast coupling. This experimental data will form the basis for clinical studies, using this material as an interesting bone substitute for guided bone regeneration.

Comparative maxillary bone-defect healing by calcium-sulphate or deproteinized bovine bone particles and extra cellular matrix membranes in a guided bone regeneration setting: an experimental study in rabbits.

OBJECTIVES: The aim of this study was to histologically compare the dynamics of bone healing response between calcium sulphate (CaS) and deproteinized bovine bone mineral (DBBM) particles in guided bone regeneration utilizing an extracellular matrix membrane (ECM) as barrier. MATERIALS AND METHODS: Eighteen rabbits were used in thisstudy. 5 × 5 mm defects were created in the edentulous space between the incisors and molars in the maxilla. The CaS and DBBM particles were placed in the defects, with or without the placement of a membrane by means of random selection. Healing was evaluated at 2, 4 and 8 weeks by histology. RESULTS: A total resorption of the CaS material was seen already at 2 weeks. Only minor resorption could be seen of the DBBM particles. The CaS group showed significantly more bone regeneration at all three healing periods compared to the DBBM group. The addition of an ECM membrane demonstrated significant additional effect on bone regeneration. The CaS group showed significant increased amounts of blood vessels compared to the DBBM group. CONCLUSIONS: Thisstudy showed that CaS in combination with an ECM membrane provided synergistic effects on bone regeneration, seemingly due to stimulating angiogenesis in the early healing process.

Maintenance therapy in patients following the surgical treatment of peri-implantitis: a 5-year follow-up study.

AIM: To evaluate the outcomes of conventional periodontal maintenance therapy on patients surgically treated for peri-implantitis. MATERIAL AND METHODS: 27 patients with 149 dental implants were monitored during 5 years every 6 months. At each recall visit, the prostheses were removed to have proper access for implant examination and supra- and sub-gingival instrumentation. Sub-gingival instrumentation was performed using an ultrasonic instrument with under 0.12% chlorhexidine irrigation. RESULTS: At baseline (6 months following peri-implant surgery), 149 implants (78 not treated and 71 treated) were available for analysis. Of the 71 treated implants, 43 presented healthy peri-implant condition, while 28 had residual peri-implant pockets either of 4-5 mm or ≥ 6 mm associated with bleeding on probing/suppuration. The longitudinal evaluation revealed that the plaque and the bleeding index scores were low during the entire follow-up period, and healthy peri-implant conditions were maintained for both the 78 non-treated and the 43 treated "healthy" implants. Of the 28 implants with residual pockets, nine showed clinical attachment loss during the 5-year follow-up. Thus, of 71 treated implants, probing attachment loss occurred in only in 9 (13%) of the implants in four patients during the 5-year period. The presence of residual pockets at three or four sites of the implants (circumferential type of pockets) was frequently associated with increased probing pocket depth (PPD) and attachment loss, while this was not the case for implants with the presence of pockets at one or two sites only (site specific). CONCLUSION: In patients with a high standard of oral hygiene and enrolled in a recall system every 6 months, the peri-implant conditions obtained following peri-implant surgery were maintained stable for the majority of subjects and implants during a 5-year period. Presence of residual pockets around the circumference of the implants seemed to be a high predictor for disease progression.

Is marginal bone loss around oral implants the result of a provoked foreign body reaction?

BACKGROUND: When a foreign body is placed in bone or soft tissue, an inflammatory reaction inevitably develops. Hence, osseointegration is but a foreign body response to the implant, which according to classic pathology is a chronic inflammatory response and characterized by bone embedding/separation of the implant from the body. PURPOSE: The aim of this paper is to suggest an alternative way of looking at the reason for marginal bone loss as a complication to treatment rather than a disease process. MATERIALS AND METHODS: The present paper is authored as a narrative review contribution. RESULTS: The implant-enveloping bone has sparse blood circulation and is lacking proper innervation in clear contrast to natural teeth that are anchored in bone by a periodontal ligament rich in blood vessels and nerves. Fortunately, a balanced, steady state situation of the inevitable foreign body response will be established for the great majority of implants, seen as maintained osseointegration with no or only very little marginal bone loss. Marginal bone resorption around the implant is the result of different tissue reactions coupled to the foreign body response and is not primarily related to biofilm-mediated infectious processes as in the pathogenesis of periodontitis around teeth. This means that initial marginal bone resorption around implants represents a reaction to treatment and is not at all a disease process. There is clear evidence that the initial foreign body response to the implant can be sustained and aggravated by various factors related to implant hardware, patient characteristics, surgical and/or prosthodontic mishaps, which may lead to significant marginal bone loss and possibly to implant failure. Admittedly, once severe marginal bone loss has developed, a secondary biofilm-mediated infection may follow as a complication to the already established bone loss. CONCLUSIONS: The present authors regard researchers seeing marginal bone loss as a periodontitis-like disease to be on the wrong track; the onset of marginal bone loss around oral implants depends in reality on a dis-balanced foreign body response.

Probing at implants with peri-implantitis and its relation to clinical peri-implant bone loss.

OBJECTIVES: To evaluate the probing depth at implants with signs of peri-implantitis before and following the removal of the prosthetic reconstructions and its relation with the peri-implant bone level as revealed by open access flap surgery. MATERIAL AND METHODS: Twenty-nine patients with 89 implants with diagnosis of peri-implantitis were included in the study. The probing pocket depth at implants before (PPD-1) and following (PPD-2) the removal of the prosthetic reconstructions was measured at four sites of the implants. These measurements were also analysed in relation to the amount of peri-implant bone loss measured during peri-implant surgery. RESULTS: The results showed that in only 119 (37%) of the sites, the measurements were similar between PPD-1 and PPD-2; in 124 sites (39%), the difference was ±1 mm, in 47 sites (15%) it was ±2 mm and in the rest of the sites it was ±3 mm. A high linear and statistically significant (P = <0.001) correlation between PPD-2 and the bone loss measured at implants for all and single surfaces was observed (r = 0.67, range 0.64-0.69), while PPD-1 yielded a weak and no statistically significant correlation (r = 0.35, range 0.27-0.42). The analysis of the bone loss at implants showed that 59 implants (66%) had an amount of bone loss that was similar at all the four surfaces, while in 30 implants, the bone loss differed for the various sites. A higher extent of bone loss was often detected at the buccal compared with the other sites. CONCLUSION: The results of this study yielded differences in the pocket probing measurements at implants with or without the prosthetic reconstruction in place and that the probing pocket depth following the removal of the prosthesis had a high correlation with the amount of bone loss at implants assessed during surgery.

[Risk communication during health crises: results of a cross-sectional study to evaluate the effectiveness of adopted corporate communication strategies during the H1N1 influenza pandemic in Italy and on the training needs of health professionals]. / La comunicazione del rischio in situazioni di crisi sanitaria: risultati di una survey sulla valutazione dell'efficacia della comunicazione istituzionale adottata per fronteggiare la pandemia influenzale AH1N1 in Italia e sui fabbisogni formativi dei professionisti sanitari.

The objectives of this study were to evaluate the effectiveness of corporate communication activities carried out during the A(H1N1) pandemic influenza in Italy and to identify educational needs of health professionals with regards to crisis communication. The study compared two samples representing respectively the general population and health professionals, living in different regions of northern, central and southern Italy. A self-administered questionnaire was used, with questions on knowledge about preventive measures during a pandemic and on satisfaction with the adopted communication campaigns. Study results highlight that both samples had very little knowledge of appropriate preventive behaviors to be adopted during a pandemic. The sample of health professionals received a greater amount of information about the pandemic with respect to the general population and showed a strong interest toward the problem of receiving adequate training in risk communication. The degree of knowledge about preventive measures is directly proportional to the existence of institutional communication activities and to having consulted a health professional.

Outcome of surgical treatment of peri-implantitis: results from a 2-year prospective clinical study in humans.

AIM: The aim of the present study was to evaluate the outcome of a surgical procedure based on pocket elimination and bone re-contouring for the treatment of peri-implantitis. MATERIAL AND METHODS: The 31 subjects involved in this study presented clinical signs of peri-implantitis at one or more dental implants (i.e. ≥6 mm pockets, bleeding on probing and/or suppuration and radiographic evidence of ≥2 mm bone loss). The patients were treated with a surgical procedure based on pocket elimination and bone re-contouring and plaque control before and following the surgery. At the time of surgery, the amount of bone loss at implants was recorded. RESULTS: Two years following treatment, 15 (48%) subjects had no signs of peri-implant disease; 24 patients (77%) had no implants with a probing pocket depth of ≥6 mm associated with bleeding and/or suppuration following probing. A total of 36 implants (42%) out of the 86 with initial diagnosis of peri-implantitis presented peri-implant disease despite treatment. The proportion of implants that became healthy following treatment was higher for those with minor initial bone loss (2-4 mm bone loss as assessed during surgery) compared with the implants with a bone loss of ≥5 mm (74% vs. 40%). Among the 18 implants with bone loss of ≥7 mm, seven were extracted. Between the 6-month and the 2-year examination, healthy implants following treatment tended to remain stable, while deepening of pockets was observed for those implants with residual pockets. CONCLUSION: The results of this study indicated that a surgical procedure based on pocket elimination and bone re-contouring and plaque control before and following surgery was an effective therapy for treatment of peri-implantitis for the majority of subjects and implants. However, complete disease resolution at the site level seems to depend on the initial bone loss at implants. Implants with no signs of peri-implantitis following treatment tended to remain healthy during the 2-year period, while a tendency for disease progression was observed for the implants that still showed signs of peri-implant disease following treatment.

Extent and location of bone loss at dental implants in patients with peri-implantitis.

Peri-implantitis is an infectious disease, which leads to loss of supporting bone around dental implants. To evaluate the extent and location of bone loss, 43 patients with peri-implantitis were examined. The bone loss was clinically measured at the time of dental surgery. Data revealed that 25% of subjects had bone loss associated with all their implants although the majority of the subjects had fewer than 50% of their implants affected by bone loss. A total number of 264 implants were examined and 131 of those had peri-implantitis associated bone loss. The pattern of bone loss at implants varied between and within subjects and location in the jaws. The highest proportion of implants with peri-implantitis was found in the upper jaw and within this group, at implants located in the incisor area of the upper jaw; the lowest was the canine area of the lower jaw. The highest proportion of implants that lost ≥ 2/3 of their bone support was found in the incisor area of the maxilla. We concluded that in the presence of peri-implant inflammation, bone quantity and characteristics may influence the progression of peri-implantitis bone loss at dental implants. We hypothesize that the ability of the bone to withstand occlusal forces will be altered as consequence of the loss of bone at the neck of the implants. To achieve an understanding of the local degradation of bone due to peri-implantitis, we need to analyze the microstructure of the bone as well the cellular biology of the peri-implant inflammation.