Unveiling the consequences of early human saliva contamination on membranes for guided bone regeneration

AIMS

GBR membranes have various surface properties designed to elicit positive responses in regenerative clinical procedures; dental clinicians attempt to employ techniques to prevent the direct interaction of contaminated oral fluids with these biomaterials. However, saliva is uninterruptedly exhibited in oral surgical procedures applying GBR membranes, suggesting a persistent interaction with biomaterials and the surrounding oral tissues. This fundamental study aimed to investigate potential alterations in the physical, chemical, and key biological properties of membranes for guided bone regeneration (GBR) caused by isolated early interaction with human saliva.

METHODS

A reproducible step-by-step protocol for collecting and interacting human saliva with membranes was developed. Subsequently, membranes were evaluated for their physicochemical properties, protein quantification, DNA, and 16S rRNA levels viability of two different cell lines at 1 and 7 days, and ALP activity. Non-interacted membranes and pure saliva of donors were applied as controls.

RESULTS

Qualitative morphological alterations were noticed; DNA extraction and 16S quantification revealed significantly higher values. Furthermore, the viability of HGF-1 and MC3T3-E1 cells was significantly (p < .05) reduced following saliva interaction with biodegradable membranes. Saliva contamination did not prejudice PTFE membranes significantly in any biological assay.

CONCLUSIONS

These outcomes demonstrated a susceptible response of biodegradable membranes to isolated early human saliva interaction, suggesting impairment of structural morphology, reduced viability to HGF-1 and MC3T3-E1, and higher absorption/adherence of DNA/16S rRNA. As a result, clinical oral procedures may need corresponding refinements.

Histological and radiological outcome after horizontal guided bone regeneration with bovine bone mineral alone or in combination with bone in edentulous atrophic maxilla: A randomized controlled trial

OBJECTIVE

To assess the radiological and histological outcome after horizontal guided bone regeneration (GBR) with deproteinized bovine bone mineral (DBBM) alone or in combination with particulate autogenous bone (PAB).

MATERIALS AND METHODS

Eighteen edentulous patients with an alveolar ridge of ≤4 mm were included in this split-mouth randomized controlled trial. Horizontal GBR with a graft composition of 100% DBBM (100:0) on one side and 90% DBBM and 10% PAB (90:10) on the other side were conducted in all patients. Cone beam computed tomography (CBCT) was obtained preoperatively, immediately postoperative, and after 10 months of healing. Width and volumetric changes in the alveolar process were measured on CBCT. Implants were placed after 10 months of graft healing where biopsies were obtained for histomorphometrical evaluation.

RESULTS

The gained widths were 4.9 (±2.4) mm (100:0) and 4.5 (±2.0) mm (90:10) at 3 mm from the top of the crest, and 5.6 (±1.3) mm (100:0) and 4.6 (±2.1) mm (90:10) at 6 mm from the top of the crest. The mean volumetric reductions were 32.8% (±23.8) (100:0) and 38.2% (±23.2) (90:10). Histomorphometry revealed that mean percentages of bone were 50.8% (±10.7) (100:0) and 46.4% (±11.3) (90:10), DBBM were 31.6% (±12.6) (100:0) and 35.4% (±14.8) (90:10), and non-mineralized tissue were 17.6% (±11.7; 100:0) and 18.2% (±18.2) (90:10). No significant differences were evident between in any evaluated parameters.

CONCLUSIONS

There were no additional effects of adding PAB to DBBM regarding bone formation, width changes, or volumetric changes after 10 months of graft healing.

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.

A randomized, multicenter, double-blinded parallel study to evaluate the safety and performance of zoledronate-coated versus uncoated dental implants in partially edentulous patients

OBJECTIVE

To evaluate patient safety, implants survival and implant stability of the bisphosphonate (zoledronate) as a coating on dental implants in patients requiring oral rehabilitation in the posterior maxilla.

MATERIALS AND METHODS

In this multicenter, double-blind, randomized controlled study, 62 patients were randomized to receive either zoledronate-coated or uncoated control implants in the premolar or molar area of the maxilla, using a one stage-protocol. Due to dropouts and exclusion 49 patients completed the study. The implants were examined by resonance frequency analysis (RFA) using an implant stability quotient (ISQ) scale at the time of insertion, and at 8 weeks, and after 12 weeks prior to prosthetic restoration. Radiographs were taken prior to surgery, directly after insertion, and during the follow-up at 12 weeks, 6 months, and 1 year to analyze changes in marginal bone levels (MBL). Finally, all complications and adverse effects (AE) were observed and recorded.

RESULTS

Out of 62 included patients, 49 patients completed the study. No AE were reported by patients receiving zoledronate-coated implants. There was no statistically significant difference between the zoledronate-coated or uncoated implant groups when comparing ISQ levels at insertion and after 12 weeks of healing, the mean of the ISQ values demonstrated a change of 4.64 (95% confidence interval: 15.46; 5.79, p = 0.43) between the two groups. At 8- and 12-weeks, ISQ values remained stable (range 62-70). Radiographic analysis showed no statistically significant difference in MBL between the two implant groups after 1 year of loading neither at the mesial side (p = 0.99) or the distal side (p = 0.97). MBL for coated implants were 0.57 mm at the mesial side and 0.46 mm at the distal side. For the uncoated implants, MBL was 0.48 mm at the mesial side and 0.47 mm at the distal side.

CONCLUSION

The zoledronate-coated dental implants are safe to use in a one-stage surgery protocol in patients requiring oral rehabilitation in the posterior maxilla, after 1 year of loading. There were no statically significant changes in implant stability and marginal bone levels measured by intraoral radiographs in comparison to uncoated control implants.

Guided bone regeneration in implant dentistry: Basic principle, progress over 35 years, and recent research activities

Bone augmentation procedures are frequent today in implant patients, since an implant should be circumferentially anchored in bone at completion of bone healing to have a good long-term stability. The best documented surgical technique to achieve this goal is guided bone regeneration (GBR) utilizing barrier membranes in combination with bone fillers. This clinical review paper reflects 35 years of development and progress with GBR. In the 1990s, GBR was developed by defining the indications for GBR, examining various barrier membranes, bone grafts, and bone substitutes. Complications were identified and reduced by modifications of the surgical technique. Today, the selection criteria for various surgical approaches are much better understood, in particular, in post-extraction implant placement. In the majority of patients, biodegradable collagen membranes are used, mainly for horizontal bone augmentation, whereas bioinert PTFE membranes are preferred for vertical ridge augmentation. The leading surgeons are using a composite graft with autogenous bone chips to accelerate bone formation, in combination with a low-substitution bone filer to better maintain the augmented bone volume over time. In addition, major efforts have been made since the millenium change to reduce surgical trauma and patient morbidity as much as possible. At the end, some open questions related to GBR are discussed.

Radiographic outcome after maxillary sinus floor augmentation with allogeneic adipose tissue-derived stem cells seeded on deproteinized bovine bone mineral. A randomized controlled experimental study

The objective was to test the hypothesis of no difference in radiographic outcome after maxillary sinus floor augmentation (MSFA) with allogeneic adipose tissue-derived stem cells (ASCs) seeded on deproteinized bovine bone mineral (DBBM) (test) compared with excipient on DBBM (control). Eighteen minipigs were assigned into three groups of six animals and euthanised after one month (T1), two months (T2), and four months (T3), respectively. Each maxillary sinus was randomly allocated to either test or control with an equal volume of graft. Computed tomography scans (CTs) after MSFA (T0) were compared with CTs after euthanasia to evaluate graft volume (GV) changes and bone density (BD) using three-dimensional measurements and Hounsfield units. GV was larger in test compared with control at T1 (P = 0.046), whereas GV was larger in control compared with test at T3 (P = 0.01). BD increased from T0 to T1-T3 (P < 0.001) with both treatments. Higher BD was observed in control compared with test at T3 (P = 0.01), while no significant difference was observed at T1 and T2. Conclusively, the present study demonstrate that allogeneic ASCs seeded on DBBM in conjunction with MSFA seemed not to improve the radiographic outcome compared with excipient on DBBM. However, radiological outcomes need to be supplemented by bone histomorphometry before definitive conclusions can be provided about the beneficial use of allogeneic ASCs seeded on DBBM in conjunction with MSFA compared with DBBM alone.

Does saliva contamination interfere or stimulate regenerative processes applying current biomaterials on oral surgical sites?

Innovative dental biomaterials have been developed in order to stimulate higher biocompatibility and faster healing times using responsive surfaces for regenerative procedures. However, saliva is one of the fluids to interact with these biomaterials in the first instance. Studies have revealed significant negative effects on the biomaterials' properties, biocompatibility and bacterial colonisation after saliva contact. Nevertheless, the current literature is unclear about the profound effects of saliva on regenerative procedures. The scientific community urges further detailed studies associating innovative biomaterials/saliva/microbiology/immunology in order to clarify clinical outcomes. This paper discusses and provides information about the challenges of research using human saliva, the lack of standardisation in protocols applying saliva, and tentative applications of saliva proteins associated with innovative dental biomaterials.

Bench-to-bedside: Feasibility of nano-engineered and drug-delivery biomaterials for bone-anchored implants and periodontal applications

Nanotechnology and drug-release biomaterials have been thoroughly explored in the last few years aiming to develop specialized clinical treatments. However, it is rare to find biomaterials associated with drug delivery properties in the current dental market for application in oral bone- and periodontal-related procedures. The gap between basic scientific evidence and translation to a commercial product remains wide. Several challenges have been reported regarding the clinical translation of biomaterials with drug-delivery systems (BDDS) and nanofeatures. Therefore, processes for BDDS development, application in preclinical models, drug delivery doses, sterilization processes, storage protocols and approval requirements were explored in this review, associated with tentative solutions for these issues. The diversity of techniques and compounds/molecules applied to develop BDDS demands a case-by-case approach to manufacturing and validating a commercial biomaterial. Promising outcomes such as accelerated tissue healing and higher antibacterial response have been shown through basic and preclinical studies using BDDS and nano-engineered biomaterials; however, the adequate process for sterilization, storage, cost-effectiveness and possible cytotoxic effects remains unclear for multifunctional biomaterials incorporated with different chemical compounds; then BDDSs are rarely translated into products. The future benefits of BDDS and nano-engineered biomaterials have been reported suggesting personalized clinical treatment and a promising reduction in the use of systemic antibiotics. Finally, the launch of these specialized biomaterials with solid data and controlled traceability onto the market will generate strong specificity for healthcare treatments.

Superhydrophilic Nanotextured Surfaces for Dental Implants: Influence of Early Saliva Contamination and Wet Storage

Hydrophilic and nanotextured surfaces for dental implants have been reported as relevant properties for early osseointegration. However, these surface characteristics are quite sensitive to oral interactions. Therefore, this pilot study aimed to investigate the superficial alterations caused on hydrophilic nanotubular surfaces after early human saliva interaction. Titanium disks were treated using an anodization protocol followed by reactive plasma application in order to achieve nanotopography and hydrophilicity, additionally; surfaces were stored in normal atmospheric oxygen or wet conditioning. Following, samples were interacted with saliva for 10 min and analyzed regarding physical–chemical properties and cellular viability. Saliva interaction did not show any significant influence on morphological characteristics, roughness measurements and chemical composition; however, hydrophilicity was statistically altered compromising this feature when the samples were stored in common air. Cellular viability tested with pre-osteoblasts cell line (MC3T3-E1) reduced significantly at 48 h on the samples without wet storage after saliva contamination. The applied wet-storage methodology appears to be effective in maintaining properties such as hydrophilicity during saliva interaction. In conclusion, saliva contamination might impair important properties of hydrophilic nanotubular surfaces when not stored in wet conditions, suggesting the need of saliva-controlled sites for oral application of hydrophilic surfaces and/or the use of modified-package methods associated with their wet storage.

Effect of peri-implant mucosal thickness on esthetic outcomes and the efficacy of soft tissue augmentation procedures: Consensus report of group 2 of the SEPA/DGI/OF workshop

OBJECTIVES

The aim of this study was to comprehensively assess the literature in terms of the effect of peri-implant mucosal thickness on esthetic outcomes and the efficacy of soft tissue augmentation procedures to increase the mucosal thickness with autogenous grafts or soft tissue substitutes.

MATERIAL AND METHODS

Two systematic reviews (SR) were performed prior to the consensus meeting to assess the following questions. Review 1, focused question: In systemically healthy patients with an implant-supported fixed prosthesis, what is the influence of thin as compared to thick peri-implant mucosa on esthetic outcomes? Review 2, focused question 1: In systemically healthy humans with at least one dental implant (immediate or staged implant), what is the efficacy of connective tissue graft (CTG), as compared to absence of a soft tissue grafting procedure, in terms of gain in peri-implant soft tissue thickness (STT) reported by randomized controlled clinical trials (RCTs) or controlled clinical trials (CCTs)? Review 2, focused question 2: In systemically healthy humans with at least one dental implant (immediate or staged implant), what is the efficacy of CTG, as compared to soft tissue substitutes, in terms of gain in peri-implant STT reported by RCTs or CCTs? The outcomes of the two SRs, the consensus statements, the clinical implications, and the research recommendations were discussed and subsequently approved at the consensus meeting during the group and plenary sessions.

CONCLUSIONS

There was a tendency of superior esthetic outcomes in the presence of a thick mucosa. The connective tissue graft remains the standard of care in terms of increasing mucosa thickness.

Radiographic changes in height and volume after lateral GBR procedures with different ratios of deproteinized bovine bone mineral and autogenous bone at different time points. An experimental study

OBJECTIVE

Estimate changes in augmentation height and volume after lateral guided bone regeneration (GBR) augmentation with different ratios of deproteinized bovine bone mineral (DBBM) and particulate autogenous bone (PAB) and autogenous bone block (ABB), at different time points.

MATERIAL AND METHODS

Twenty-four minipigs were randomly allocated into three healing periods. Lateral augmentation in 96 sites with standardized quantity of graft material was performed with different ratios of DBBM and PAB (50:50, 75:25, and 100:0) and ABB in combination with DBBM, covered by a collagen membrane. Changes in augmentation height and volume were assessed on CT volumes acquired 10, 20, and 30 weeks after surgery.

RESULTS

Reduction in bone augmentation height was as follows: 50:50-1.7 mm (-33.1%), 75:25-1.8 mm (-37.8%), 100:0-1.7 mm (-35.8%), and ABB - 0.2 mm (-3.7%), after 30 weeks. The augmentation height was significantly better preserved with ABB compared to 50:50, 75:25, and 100:0, while no significant difference was present among particulate grafts. No significant difference in volumetric reduction was found among 50:50, 75:25, 100:0 and ABB after 30 weeks, while 100:0 presented significant less reduction compared to 50:50, 75:25 and ABB after 10 and 20 weeks.

CONCLUSIONS

Augmentation height following GBR was better preserved with ABB covered with DBBM. Addition of PAB to DBBM did not affect the changes in height of the graft. The volumetric stability seems to be comparable for ABB covered by DBBM and all particulate grafts after 30 weeks. However, DBBM alone revealed significant less volume reduction in the early healing phase.

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).

Biomaterials and regenerative technologies used in bone regeneration in the craniomaxillofacial region: Consensus report of group 2 of the 15th European Workshop on Periodontology on Bone Regeneration

BACKGROUND AND AIMS

To review the regenerative technologies used in bone regeneration: bone grafts, barrier membranes, bioactive factors and cell therapies.

MATERIAL AND METHODS

Four background review publications served to elaborate this consensus report.

RESULTS AND CONCLUSIONS

Biomaterials used as bone grafts must meet specific requirements: biocompatibility, porosity, osteoconductivity, osteoinductivity, surface properties, biodegradability, mechanical properties, angiogenicity, handling and manufacturing processes. Currently used biomaterials have demonstrated advantages and limitations based on the fulfilment of these requirements. Similarly, membranes for guided bone regeneration (GBR) must fulfil specific properties and potential biological mechanisms to improve their clinical applicability. Pre-clinical and clinical studies have evaluated the added effect of bone morphogenetic proteins (mainly BMP-2) and autologous platelet concentrates (APCs) when used as bioactive agents to enhance bone regeneration. Three main approaches using cell therapies to enhance bone regeneration have been evaluated: (a) "minimally manipulated" whole tissue fractions; (b) ex vivo expanded "uncommitted" stem/progenitor cells; and (c) ex vivo expanded "committed" bone-/periosteum-derived cells. Based on the evidence from clinical trials, transplantation of cells, most commonly whole bone marrow aspirates (BMA) or bone marrow aspirate concentrations (BMAC), in combination with biomaterial scaffolds has demonstrated an additional effect in sinus augmentation and horizontal ridge augmentation, and comparable bone regeneration to autogenous bone in alveolar cleft repair.

Barrier membranes: More than the barrier effect?

AIM

To review the knowledge on the mechanisms controlling membrane-host interactions in guided bone regeneration (GBR) and investigate the possible role of GBR membranes as bioactive compartments in addition to their established role as barriers.

MATERIALS AND METHODS

A narrative review was utilized based on in vitro, in vivo and available clinical studies on the cellular and molecular mechanisms underlying GBR and the possible bioactive role of membranes.

RESULTS

Emerging data demonstrate that the membrane contributes bioactively to the regeneration of underlying defects. The cellular and molecular activities in the membrane are intimately linked to the promoted bone regeneration in the underlying defect. Along with the native bioactivity of GBR membranes, incorporating growth factors and cells in membranes or with graft materials may augment the regenerative processes in underlying defects.

CONCLUSION

In parallel with its barrier function, the membrane plays an active role in hosting and modulating the molecular activities of the membrane-associated cells during GBR. The biological events in the membrane are linked to the bone regenerative and remodelling processes in the underlying defect. Furthermore, the bone-promoting environments in the two compartments can likely be boosted by strategies targeting both material aspects of the membrane and host tissue responses.

In vitro evaluation of barrier function against oral bacteria of dense and expanded polytetrafluoroethylene (PTFE) membranes for guided bone regeneration

AIM

This study evaluates biofilm formation and barrier function against Streptococcus oralis of nonresorbable polytetrafluoroethylene (PTFE) guided bone regeneration membranes having expanded (e-PTFE) and dense (d-PTFE) microstructure.

MATERIALS AND METHODS

Three e-PTFE membranes of varying openness, one d-PTFE membrane, and commercially pure titanium discs were evaluated. All e-PTFE membranes consisted of PTFE nodes interconnected by fibrils. The d-PTFE membrane was fibril-free, with large evenly spaced indentations. The surfaces were challenged with S. oralis and incubated statically for 2-48h. Bacterial colonization, viability, and penetration were evaluated.

RESULTS

S. oralis numbers increased over time on all surfaces, as observed using scanning electron microscopy, while cell viability decreased, as measured by colony forming unit (CFU) counting. At 24h and 48h, biofilms on d-PTFE were more mature and thicker (tower formations) than on e-PTFE, where fewer layers of cells were distributed mainly horizontally. Biofilms accumulated preferentially within d-PTFE membrane indentations. At 48h, greater biofilm biomass and number of viable S. oralis were found on d-PTFE compared to e-PTFE membranes. All membranes were impermeable to S. oralis cells.

CONCLUSIONS

All PTFE membranes were effective barriers against bacterial passage in vitro. However, d-PTFE favored S. oralis biofilm formation.

Histomorphometric analyses of area fraction of different ratios of Bio-Oss® and bone prior to grafting procedures - An in vitro study to demonstrate a baseline

OBJECTIVE

The objective of this study was to estimate the area fraction of different ratios of Bio-Oss^® and bone, prior to grafting in an in vitro model to demonstrate a histomorphometric baseline.

METHODS

Bio-Oss^® particles were mixed with autogenous bone from pig jaw in three different ratios (50:50, 80:20 and 100:0) and packed in rice paper in a standardized procedure. Histomorphometric analyses were performed in 25 specimens and 74 regions of interest. The area percentage of Bio-Oss^® , bone, and non-mineralized tissue (NMT) were calculated. Results were reported as mean values and 95% confidence interval (CI).

RESULTS

The mean area fraction of Bio-Oss^® was 20.6% (CI: 18.2-23) in the 50:50 mixture, 33.6% (CI: 29.7-37.6) in the 80:20 mixture, and 43.4% (CI: 40.5-46.3) in the 100:0 mixture. The mean area fraction of NMT was 60.5% (CI: 57.9-63.1) in the 50:50 mixture, 59.6% (CI: 56.4-62.7) in the 80:20 mixture, and 56.6% (CI: 53.7-59.5) in the 100:0 mixture. The mean area fraction of bone was 18.9% (CI: 16.9-20.9) in the 50:50 mixture and 6.8% (CI: 5-8.6) in the 80:20 mixture.

CONCLUSION

There is a great difference in the clinically estimated percentage and the histomorphometrically evaluated percentage of Bio-Oss^® at baseline, prior to grafting. The area fraction of different tissues presented in this study may be beneficial as guidance for histomorphometrical baseline calculations when different mixtures of Bio-Oss^® and autogenous bone are used as grafting materials.

Guided bone regeneration: materials and biological mechanisms revisited

Guided bone regeneration (GBR) is commonly used in combination with the installment of titanium implants. The application of a membrane to exclude non‐osteogenic tissues from interfering with bone regeneration is a key principle of GBR. Membrane materials possess a number of properties which are amenable to modification. A large number of membranes have been introduced for experimental and clinical verification. This prompts the need for an update on membrane properties and the biological outcomes, as well as a critical assessment of the biological mechanisms governing bone regeneration in defects covered by membranes. The relevant literature for this narrative review was assessed after a MEDLINE/PubMed database search. Experimental data suggest that different modifications of the physicochemical and mechanical properties of membranes may promote bone regeneration. Nevertheless, the precise role of membrane porosities for the barrier function of GBR membranes still awaits elucidation. Novel experimental findings also suggest an active role of the membrane compartment per se in promoting the regenerative processes in the underlying defect during GBR, instead of being purely a passive barrier. The optimization of membrane materials by systematically addressing both the barrier and the bioactive properties is an important strategy in this field of research.

Tissue dynamics and regenerative outcome in two resorbable non-cross-linked collagen membranes for guided bone regeneration: A preclinical molecular and histological study in vivo

OBJECTIVES

To investigate the molecular and structural patterns of bone healing during guided bone regeneration (GBR), comparing two resorbable non-cross-linked collagen membranes.

MATERIALS AND METHODS

Trabecular bone defects in rat femurs were filled with deproteinized bovine bone (DBB) and covered with either a membrane comprising collagen and elastin (CXP) or collagen (BG). Samples were harvested after 3 and 21 days for histology/histomorphometry and gene expression analysis. Gene expression analysis was performed on the membrane (at 3 days) and the underlying defect compartment (at 3 and 21 days).

RESULTS

At the total defect level, no differences in bone area percentage were found between the CXP and BG. When evaluating the central area of the defect, a higher percentage of de novo bone formation was seen for the CXP membrane (34.9%) compared to BG (15.5%) at 21 days (p = .01). Gene expression analysis revealed higher expression of bone morphogenetic protein-2 (Bmp2) in the membrane compartment at 3 days in the BG group. By contrast, higher Bmp2 expression was found in the defect compartment treated with the CXP membrane, both at 3 and 21 days. A significant temporal increase (from 3 to 21 days) in the remodeling activity, cathepsin K (Catk) and calcitonin receptor (Calcr), was found in the CXP group. Molecular analysis demonstrated expression of several growth factors and cytokines in the membrane compartment irrespective of the membrane type. Bmp2 expression in the membrane correlated positively with Bmp2 expression in the defect, whereas fibroblast growth factor-2 (Fgf2) expression in the membrane correlated positively with inflammatory cytokines, tumor necrosis factor-alpha (Tnfa) and interleukin-6 (Il6) in the defect.

CONCLUSIONS

The results provide histological and molecular evidence that different resorbable collagen membranes contribute differently to the GBR healing process. In the BG group, bone formation was primarily localized to the peripheral part of the defect. By contrast, the CXP group demonstrated significantly higher de novo bone formation in the central portion of the defect. This increase in bone formation was reflected by triggered expression of potent osteogenic growth factor, Bmp2, in the defect. These findings suggest that the CXP membrane may have a more active role in regulating the bone healing dynamics.

Lateral ridge augmentation with Bio-Oss alone or Bio-Oss mixed with particulate autogenous bone graft: a systematic review

The objective of this systematic review was to test the hypothesis of no difference in implant treatment outcomes when using Bio-Oss alone or Bio-Oss mixed with particulate autogenous bone grafts for lateral ridge augmentation. A search of the MEDLINE, Cochrane Library, and Embase databases in combination with a hand-search of relevant journals was conducted. Human studies published in English from 1 January 1990 to 1 May 2016 were included. The search provided 337 titles and six studies fulfilled the inclusion criteria. Considerable variation prevented a meta-analysis from being performed. The two treatment modalities have never been compared within the same study. Non-comparative studies demonstrated a 3-year implant survival of 96% with 50% Bio-Oss mixed with 50% autogenous bone graft. Moreover, Bio-Oss alone or Bio-Oss mixed with autogenous bone graft seems to increase the amount of newly formed bone as well as the width of the alveolar process. Within the limitations of this systematic review, lateral ridge augmentation with Bio-Oss alone or in combination with autogenous bone graft seems to induce newly formed bone and increase the width of the alveolar process, with high short-term implant survival. However, long-term studies comparing the two treatment modalities are needed before final conclusions can be drawn.

The bone-implant interface of dental implants in humans on the atomic scale

Osseointegration of dental implants occurs on a hierarchy of length scales down to the atomic level. A deeper understanding of the complex processes that take place at the surface of an implant on the smallest scale is of interest for the development of improved biomaterials. To date, transmission electron microscopy (TEM) has been utilized for examination of the bone-implant interface, providing details on the nanometer level. In this study we show that TEM imaging can be complemented with atom probe tomography (APT) to reveal the chemical composition of a Ti-based dental implant in a human jaw on the atomic level of resolution. As the atom probe technique has equal sensitivity for all elements, it allows for 3 dimensional characterizations of osseointegrated interfaces with unprecedented resolution. The APT reconstructions reveal a Ca-enriched zone in the immediate vicinity of the implant surface. A surface oxide of some 5nm thickness was measured on the titanium implant, with a sub-stoichiometric composition with respect to TiO₂. Minor incorporation of Ca into the thin oxide film was also evident. We conclude that the APT technique is capable of revealing chemical information from the bone-implant interface in 3D with unprecedented resolution, thus providing important insights into the mechanisms behind osseointegration.

STATEMENT OF SIGNIFICANCE

Osseointegration of dental implants occurs on a hierarchy of length scales down to the atomic level. A deeper understanding of the complex processes that take place at the surface of an implant on the smallest scale is of interest for the development of improved biomaterials. To date, transmission electron microscopy (TEM) has been utilized for examination of the bone-implant interface, providing details on the nanometer level. In this study we show that TEM imaging can be complemented with atom probe tomography (APT) to reveal the chemical composition of a Ti-based dental implant in a human jaw on the atomic level of resolution. Correlative microscopy ensures the accuracy of APT reconstructions and helps provide both chemical and structural information of the bone-implant interface on the smallest of length scales.

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.

Host tissue reactions of non-demineralized autogenic and xenogenic dentin blocks implanted in a non-osteogenic environment. An experimental study in rabbits

Dentoalveolar ankylosis with osseous replacement is often seen after replantation of avulsed teeth, and this process may be used for preservation of alveolar crests after trauma. Its exact mechanisms with regard to osteoinductive properties are not yet fully understood and need to be systematically investigated. Dentin can possibly act as a slow-releasing carrier of bone morphogenic proteins (BMP), and this property of dentin has been proposed to be used as an alternative or supplement to bone grafting in the maxillofacial region. We aimed to initially asses host tissue reactions to dentin by implanting dentin blocks of autogenic and xenogenic human origin in rabbit connective tissue of the abdominal wall and femoral muscle. Animals were sacrificed after a period of 3 months, and histological processing, sectioning and examinations were carried out. Bone formation, cell counts and thickness of capsule surrounding the grafts were evaluated. Only minor signs of heterotopic bone formation were seen. There were no significant differences between autografts and xenografts or grafts implanted in connective tissue or muscle with regards to tissue reactions except for a significant difference (P = 0.018) in findings of more local inflammatory cells in relation to grafts placed in connective tissue in the autograft group. We conclude that during the time frame of this study, non-demineralized dentin, whether autogenous or xenogenic did not have the potential to induce bone formation when implanted in non-osteogenic areas such as the abdominal wall and abdominal muscle of rabbits.

Early biocompatibility of poly (ethylene glycol) hydrogel barrier materials for guided bone regeneration. An in vitro study using human gingival fibroblasts (HGF-1)

OBJECTIVES

To evaluate the early cellular attachment and viability to modified polyethylene glycol (PEG) hydrogels with the influence of arginine-glycine-aspartic acid (RGD) in an in vitro model system.

MATERIAL AND METHODS

Human gingival fibroblasts (HGF-1) were cultured on 6 different modalities of PEG hydrogel in hydrophobic polystyrene wells. A total of 7500 cells/well (10,000 cells/cm(2)) were dispersed over the PEG filled wells and incubated in triplicates for 24 h, 7 and 13 days. Cell numbers were calculated by means of a NucleoCounter. Cell viability was determined by measuring lactate dehydrogenase (LDH). For statistical analysis, nonparametric Kruska-Wallis test followed by Dunetts T3 test were used.

RESULTS

All PEG modifications showed good biocompatibility, as demonstrated by low LDH values per cell at the earlier two time points. After 13 days, all PEG modifications showed significantly lower number of cells compared with the controls, and the MX60 configurations demonstrated significantly higher LDH/cell values compared with the other hydrogels.

CONCLUSIONS

Modifications of the physio-chemical properties of PEG hydrogels and the addition of RGD and spacers influenced the initial cellular response of cultured HGF-1 cells. With the exception of MX60 after 13 days, all PEG formulations performed similarly well. Early cellular response should be considered when developing PEG-based material for clinical purposes.

One-year results of a clinical and radiological prospective multicenter study on NEOSS® dental implants

BACKGROUND

NEOSS® (Neoss Ltd., Harrogate, UK) dental implant system was introduced on the clinical arena in 2003. It is important that novel implant systems are systematically evaluated in a multicenter setting.

PURPOSE

The aim of this study was to follow a large number of consecutively treated patients, with NEOSS dental implant system, both clinically and radiographically. The current report constitutes the 1-year data of a planned 5-year study.

MATERIALS AND METHODS

The study included a total of 177 patients treated with 590 NEOSS implants at 13 clinics in Sweden. The material was composed of 72 males and 105 females treated for single, partial, and total edentulism. Clinical, radiographic, and subjective evaluations were performed.

RESULTS

Out of 590 implants, 13 early failures have been reported, corresponding to a 1-year cumulative survival rate (CSR) of 97.8%. Evaluation of function and esthetics at the 1-year visit resulted in 100% success for function and 98% success for the esthetic outcome. The mean marginal bone loss was 0.6 mm (SD 1.1) after 1 year in clinical function. No adverse effects of the NEOSS dental implants were reported, and complications were few and similar to those reported for implant treatment in general.

CONCLUSION

The CSR in the present study was 97.8%. No adverse effects of the NEOSS implants were reported, and complications during the study period were few and similar to those reported to for other well-documented implants system. Based on the present data, we conclude that NEOSS dental implant is a safe and predictable implant system. However, the high number of dropouts in the radiological evaluation must be considered when interpreting the data.

Iliac crest autogenous bone graft versus alloplastic graft and guided bone regeneration in the reconstruction of atrophic maxillae: a 5-year retrospective study on cost-effectiveness and clinical outcome

BACKGROUND

Reconstruction of the atrophic maxillae with autogenous bone graft and jawbone-anchored bridges is a well-proven technique. However, the morbidity associated with the concept should not be neglected. Furthermore, the costs for such treatment, including general anesthesia and hospital stay, are significant. Little data are found in the literature with regard to a cost-benefit approach to various treatment alternates.

PURPOSE

The aim of this retrospective study was to compare from a health-economical and clinical perspective the reconstruction of the atrophic maxillae prior to oral implant treatment either with autogenous bone grafts harvested from the iliac crest or the use of demineralized freeze-dried bone (DFDB) in combination with a thermoplastic carrier (Regeneration Technologies Inc., Alachua, FL, USA) and guided bone regeneration (GBR).

MATERIALS AND METHODS

A total of 26 patients (13 + 13) were selected and matched with regard to indication, sex, and age. The study was performed 5 years after the completion of the treatment. Implant survival, morbidity, and complications were analyzed. Furthermore, a detailed analysis of the total cost for the respective treatment modality was performed, including material, costs for staff, sick leave, etc.

RESULTS

The study revealed no statistical difference with regard to implant survival for the respective groups. The average total cost, per patient, for the DFDB group was 22.5% of the total cost for a patient treated with autogenous bone grafting procedures.

CONCLUSIONS

The study concluded that reconstruction of atrophic maxillae with a bone substitute material (DFDB) in combination with GBR can be performed with an equal treatment outcome and with less resources and a significant reduced cost in selected cases compared with autogenous bone grafts from the iliac crest.

Postoperative Morbidity in Traditional versus Coblation Tonsillectomy

Objectives

The aim of this study was to compare levels of postoperative pain after traditional (cold steel with bipolar cautery) and Coblation tonsillectomies.

Methods

Patients with recurrent or chronic tonsillitis, including tonsillar hyperplasia, were randomized to undergo tonsillectomies using either a traditional cutting technique or the Coblation technique. Patients and staff on the relevant wards were blinded regarding patient allocation. Pain, odynophagia, and activity limitations were recorded on a visual analog scale. Analgesics were self-administered, and daily analgesic consumption by patients was reported. All complications were also registered.

Results

Fifty-seven patients (between 6 and 57 years of age) completed the study. No significant difference was found between the two techniques with regard to reported pain, odynophagia, activity limitations, or use of analgesics. A slight tendency toward decreased pain and decreased use of analgesics in the Coblation group reached statistical significance only when the adult patients were analyzed separately. Two cases of hospital readmission occurred because of postoperative bleeding following Coblation tonsillectomies.

Conclusions

Overall, the two methods are equivalent in terms of postoperative pain, including the use of analgesics. The risk of postoperative bleeding after the Coblation method requires further evaluation with specifically designed studies.

Postoperative morbidity in traditional versus coblation tonsillectomy

OBJECTIVES

The aim of this study was to compare levels of postoperative pain after traditional (cold steel with bipolar cautery) and Coblation tonsillectomies.

METHODS

Patients with recurrent or chronic tonsillitis, including tonsillar hyperplasia, were randomized to undergo tonsillectomies using either a traditional cutting technique or the Coblation technique. Patients and staff on the relevant wards were blinded regarding patient allocation. Pain, odynophagia, and activity limitations were recorded on a visual analog scale. Analgesics were self-administered, and daily analgesic consumption by patients was reported. All complications were also registered.

RESULTS

Fifty-seven patients (between 6 and 57 years of age) completed the study. No significant difference was found between the two techniques with regard to reported pain, odynophagia, activity limitations, or use of analgesics. A slight tendency toward decreased pain and decreased use of analgesics in the Coblation group reached statistical significance only when the adult patients were analyzed separately. Two cases of hospital readmission occurred because of postoperative bleeding following Coblation tonsillectomies.

CONCLUSIONS

Overall,the two methods are equivalent in terms of postoperative pain,including the use of analgesics. The risk of postoperative bleeding after the Coblation method requires further evaluation with specifically designed studies.