Clinical evaluation of guided bone regeneration at exposed parts of Brånemark dental implants with and without bone allograft

Efficacy of biomaterials for lateral bone augmentation performed with guided bone regeneration. A network meta-analysis

Bone regeneration is often required concomitant with implant placement to treat a bone fenestration, a dehiscence, and for contouring. This systematic review assessed the impact of different biomaterials employed for guided bone regeneration (GBR) simultaneous to implant placement on the stability of radiographic peri-implant bone levels at ≥12 months of follow-up (focused question 1), as well as on bone defect dimension (width/height) changes at re-assessment after ≥4 months (focused question 2). Only randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that compared different biomaterials for GBR were considered. A Bayesian network meta-analysis (NMA) was performed using a random-effects model. A ranking probability between treatments was obtained, as well as an estimation of the surface under the cumulative ranking value (SUCRA). Overall, whenever the biological principle of GBR was followed, regeneration occurred in a predictable way, irrespective of the type of biomaterial used. A lower efficacy of GBR treatments was suggested for initially large defects, despite the trend did not reach statistical significance. Regardless of the biomaterial employed, a certain resorption of the augmented bone was observed overtime. While GBR was shown to be a safe and predictable treatment, several complications (including exposure, infection, and soft tissue dehiscence) were reported, which tend to be higher when using cross-linked collagen membranes.

Bone regeneration in implant dentistry: Which are the factors affecting the clinical outcome?

The key factors that are needed for bone regeneration to take place include cells (osteoprogenitor and immune-inflammatory cells), a scaffold (blood clot) that facilitates the deposition of the bone matrix, signaling molecules, blood supply, and mechanical stability. However, even when these principles are met, the overall amount of regenerated bone, its stability over time and the incidence of complications may significantly vary. This manuscript provides a critical review on the main local and systemic factors that may have an impact on bone regeneration, trying to focus, whenever possible, on bone regeneration simultaneous to implant placement to treat bone dehiscence/fenestration defects or for bone contouring. In the future, it is likely that bone tissue engineering will change our approach to bone regeneration in implant dentistry by replacing the current biomaterials with osteoinductive scaffolds combined with cells and mechanical/soluble factors and by employing immunomodulatory materials that can both modulate the immune response and control other bone regeneration processes such as osteogenesis, osteoclastogenesis, or inflammation. However, there are currently important knowledge gaps on the biology of osseous formation and on the factors that can influence it that require further investigation. It is recommended that future studies should combine traditional clinical and radiographic assessments with non-invasive imaging and with patient-reported outcome measures. We also envisage that the integration of multi-omics approaches will help uncover the mechanisms responsible for the variability in regenerative outcomes observed in clinical practice.

The Role of Blood Clot in Guided Bone Regeneration: Biological Considerations and Clinical Applications with Titanium Foil

In Guided Bone Regeneration (GBR) materials and techniques are essential to achieve the expected results. Thanks to their properties, blood clots induce bone healing, maturation, differentiation and organization. The preferred material to protect the clot in Guided Bone Regeneration is the titanium foil, as it can be shaped according to the bone defect. Furthermore, its exposition in the oral cavity does not impair the procedure. We report on five clinical cases in order to explain the management of blood clots in combination with titanium foil barriers in different clinical settings. Besides being the best choice to protect the clot, the titanium foil represents an excellent barrier that is useful in GBR due to its biocompatibility, handling, and mechanical strength properties. The clot alone is the best natural scaffold to obtain the ideal bone quality and avoid the persistence of not-resorbed granules of filler materials in the newly regenerated bone. Even though clot contraction still needs to be improved, as it impacts the volume of the regenerated bone, future studies in GBR should be inspired by the clot and its fundamental properties.

Clinical and radiographical performance of implants placed with simultaneous guided bone regeneration using resorbable and nonresorbable membranes after 22-24 years, a prospective, controlled clinical trial

Aim

The aim was to evaluate the performance of implants placed with simultaneous guided bone regeneration (GBR) using resorbable or nonresorbable membranes compared to implants placed in pristine bone without bone regeneration after an observation period of 22–24 years.

Material and Methods

The patient cohort of this clinical trial was treated from 1994 to 1996. Dehiscence defects were treated with GBR by either using resorbable collagen membranes (BG) or nonresorbable ePTFE membranes (GT). Implants placed in pristine bone served as a control (CT). Clinical parameters, marginal bone levels, and technical outcomes were evaluated following restoration placement and at the present follow‐up. A 3D radiographic analysis was conducted in order to assess buccal and oral bone dimensions. Implant survival was assessed with Kaplan–Meier analysis and a frailty model (level of significance 5%).

Results

Out of the originally 72 patients (mean age 75.4 ± 15.70 years) with 265 implants, 39 patients with 147 implants were included in the study after a median period of 23.5 years. Implant survival was 89.3% in group BG (n = 100), 90.2% in group GT (n = 37), and 93.8% in group CT (n = 105), without significant differences (Frailty proportional hazard model p = .79). Smoking had a negative effect on survival (p = .0122). Mean vertical marginal bone levels were −2.3 ± 1.4 mm (BG, n = 59), −3.0 ± 1.5 mm (GT, n = 21), and −2.3 ± 1.6 mm (CT, n = 52). The vertical buccal bone levels were −3.0 ± 1.9 mm (BG, n = 57), −3.5 ± 2.2 mm (GT, n = 21), and −2.6 ± 1.8 mm (CT, n = 49), without significant differences.

Conclusion

Implant placement with GBR procedures provides treatment outcomes with favorable implant survival rates (89.3%–93.8%) after 23.5 years. Smoking, however, affected implant survival negatively.

Evaluation of a Double Layer Technique to Enhance Bone Formation in Atrophic Alveolar Ridge: Histologic Results of a Pilot Study

The atrophic alveolar ridge has been a challenge in implant dentistry; various techniques using the principle of guided bone regeneration (GBR) have been applied in the past 2 decades.The aim of this study was to introduce and evaluate-clinically, histologically, and radiographically-a novel technique of regenerating a new bone in the atrophic alveolar ridge, which is based on the GBR principles, the double layer technique (DLT). Six patients with partially edentulous jaws with a residual bone width less than or equal to 4 mm in the maxilla were subjected to GBR. The sites were grafted using a DLT. At first, sites were grafted with allogenic bone and then a second layer of deproteinized bovine bone was placed. Next, grafted sites were covered with a resorbable membrane tucked with 2 titanium pins. Cone-beam computed tomography scans were obtained before and 5 months after DLT. In the latter case and during implant site preparation, trephine biopsies were obtained and processed for histologic and histomorphometric evaluation. In all cases, implants were successfully installed and primary stability was established. Implant diameter ranged from 3.8 to 4.1 mm. In all cases, radiographic findings showed increased alveolar ridge width before and after surgery. The new tissues consisted mostly of a variable amount of new trabecular bone, some loose connective tissue, blood vessels, and occasional inflammatory cells. All 15 implants placed had 100% survival rate after a 5-year follow-up. On the basis of these preliminary results, it seems that the double layer GBR technique may achieve satisfactory results from a clinical, radiographic, and histologic perspective favoring placement of dental implants in the atrophic maxillary alveolar ridge.

Efficacy of lateral bone augmentation performed simultaneously with dental implant placement: A systematic review and meta-analysis

OBJECTIVES

To analyse the evidence regarding the efficacy of lateral bone augmentation procedures in terms of defect resolution in cases of horizontal ridge deficiencies after implant placement.

MATERIALS AND METHODS

Included studies met the following inclusion criteria: randomized controlled trials (RCTs) or controlled clinical trials (CCTs), re-entry procedure to assess defect resolution, minimum of 10 patients (5 per group). Meta-analyses were performed whenever possible, including subgroup analysis based on membranes and grafting materials.

RESULTS

Twenty-eight publications (20 short-term, 8 follow-up studies) were included. The most often used type of intervention was a xenogeneic particulated grafting material (XE) and a resorbable collagen membrane (CM). The mean defect height at baseline amounted to 5.1 mm (range 2.4-7.8) and decreased to a mean of 0.9 mm (range 0.2-2.2) at re-entry, and the mean defect resolution was 81.3% (range 56.4%-97.1%). Defect height reduction was not significantly different using CM+XE as control treatment compared to the combined data of the respective test groups [n = 11; weighted mean difference (WMD) = -0.006 mm; 95% CI, -0.61, 0.60; p = 0.985]. The absence of any lateral bone augmentation was less favourable than the conjunction of a membrane and a bone grafting material (n = 1; MD = -1.96 mm; 95% CI, -3.48, -0.44; p = 0.011). The lack of a grafting material was less favourable than the conjunction of grafting material and membrane (n = 1; MD = -2.44 mm; 95% CI, -4.53, -0.35; p = 0.022), and the addition of a membrane compared to a grafting material alone was more favourable (n = 3; WMD = 0.97 mm; 95% CI, 0.31, 1.64; p = 0.004).

CONCLUSIONS

Lateral bone augmentation is a successful treatment modality. For optimal defect height reduction, a barrier membrane and a grafting material should be combined.

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.

Effect of absorbable membranes on sandwich bone augmentation

OBJECTIVES

This study was conducted to evaluate the effect of barrier membranes on sandwich bone augmentation (SBA) for the treatment of implant dehiscence defects.

MATERIAL AND METHODS

Twenty-six implant-associated buccal dehiscence defects in 22 patients were treated according to the SBA concept - mineralized human cancellous allograft (inner layer), mineralized human cortical allograft (outer layer) and coverage with barrier membrane. The defects were randomly assigned to the bovine collagen membrane (BME) group; acellular dermal matrix (ADM) group; and no membrane group. Measurements at baseline and 6 months re-entry included defect height (DH: from smooth-rough junction to the most apical part of the defect), defect width (DW: at the widest part of the defect), and horizontal defect depth (HDD: at three locations - smooth-rough junction, middle, and most apical portion of the defect). All measurements were taken from a reference stent. Statistical analyses were performed for comparison of intra- and inter-group comparisons.

RESULTS

All implants placed were successfully osseointegrated. DH at baseline for three groups were not significantly different (P=0.858). Mean % DH reductions for ADM, BME, and control groups at 6 months were 73.9+/-17.6%, 68.1+/-30.1%, and 63.6+/-23.9%, respectively, with no significant difference among the groups (P=0.686). Mean horizontal bone gain, however, was significantly greater for membrane groups (1.7 mm for ADM, 1.6 mm for BME) compared with control group (1 mm) (P=0.044). Implant exposure resulted in significant reduction in total height gain (79.1+/-14.3% vs. 57+/-23.5%, P=0.021).

CONCLUSIONS

Within the limit of this study, it is concluded that SBA technique achieved predictable clinical outcomes. The addition of absorbable membranes enhanced bone gain in thickness compared with membrane-treated sites.

Healing of intrabony peri-implantitis defects following application of a nanocrystalline hydroxyapatite (Ostimtm) or a bovine-derived xenograft (Bio-Osstm) in combination with a collagen membrane (Bio-Gidetm). A case series

OBJECTIVES

The aim of the present case series was to evaluate the healing of intrabony peri-implantitis defects following application of a nanocrystalline hydroxyapatite (NHA) or a bovine-derived xenograft in combination with a collagen membrane (BDX+BG).

MATERIAL AND METHODS

Twenty-two patients having moderate peri-implantitis (n=22 intrabony defects) were randomly treated with (i) access flap surgery (AFS) and the application of NHA, or with AFS and the application of BDX+BG. Clinical parameters were recorded at baseline and after 6 months of non-submerged healing.

RESULTS

Post-operative wound healing revealed that NHA compromized initial adhesion of the mucoperiosteal flaps in all patients. At 6 months after therapy, NHA showed a reduction in the mean PD from 7.0+/-0.6 to 4.9+/-0.6 mm and a change in the mean clinical attachment loss (CAL) from 7.5+/-0.8 to 5.7+/-1.0 mm. In the BDX+BC group, the mean PD was reduced from 7.1+/-0.8 to 4.5+/-0.7 mm and the mean CAL changed from 7.5+/-1.0 to 5.2+/-0.8 mm.

CONCLUSION

Within the limits of the present case series, it can be concluded that at 6 months after surgery both therapies resulted in clinically important PD reductions and CAL gains.

Effects of cortical bone perforation on experimental guided bone regeneration

This study was designed to evaluate the effects of cortical bone perforation histologically and histomorphometrically on guided bone regeneration (GBR) in rabbits. After elimination of the periosteum, cortical bone defects of two sizes were made in the external cortical plate of the frontal bone (Group A: 1 x 15 mm; Group B: 3 x 15 mm). A non-resorbable membrane filled with autogenous blood was placed in the experimental area and secured with titanium pins. After 1 and 2 weeks, vascularized connective tissue and new bone were generated in the space surrounding the defects in both the groups. The amount of vascularized connective tissue generated in Group B was greater than that in Group A at 1 week. Alkaline phosphatase (ALP) was expressed on the bone surrounding the perforation. The expression of ALP was more extensive in Group B than in Group A and was proportional to the breadth of perforation. At 2 weeks, the perforated region was almost covered with new bone in Group A. ALP was expressed at the periphery of newly formed bone. The expression of ALP was proportional to the breadth and height of perforation. At 6 weeks, semicircular outgrowth of bone towards the periphery of the perforated region was observed in both the groups. Newly formed bone volume and ALP expression in Group B were more extensive than those in Group A. At 12 weeks, the space was filled with bone and connective tissue in both the groups. There was no difference in ALP expression between Groups A and B. Histomorphometric analysis showed significant differences between both the groups (two-way ANOVA, P<0.01). We conclude that a larger perforation is associated with prompter bone formation in the secluded space during GBR.

Effect of bioresorbable fibres (Polyfibre® ) and a bioresorbable foam (Polyfoam® ) on new bone formation

The aim of the study was to evaluate two bioresorbable polylactic acid (PLA) filler materials in a guided bone regeneration (GBR) model system. The first was Polyfibre, a fibrous PLA filler material. Polyfoam, the second material tested, consisted of a spongy PLA filler material. In each group there were eight rabbits. In test rabbits a flap was raised uncovering the calvaria. A hemispherical PLA dome was filled with Polyfibre or Polyfoam material and periphereal blood and anchored onto the calvaria. Eight rabbits with the same domes, filled with blood alone, served as controls. The rabbits were sacrificed at 1 or 2 months. Histomorphometric measurements of regenerated total tissue volume, bone height and bone volume were carried out in undecalcified sections under a light microscope. At 1 month the totally filled volume attained 87% (range 82-91) in the fibre group, including 25% (23-27) fibres, 87% (85-95) in the foam group, including 15% (15-16) foam, and 55% (16-100) in the controls. The volume of mineralized bone was 12% (7-15) in the fibre group, 15% (12-18) in the foam group and 6% (1-11) in control domes. Bone height attained 48% (27-79) in the fibre group, 37% (31-58) in the foam group and 45% (14-67) in the control group. At 2 months, tissue volume attained 86% (85-87) including 26% (22-29) fibres, bone volume attained 13% (7-21) and bone height attained 56% (42-78) in the Polyfibre group. In the Polyfoam group, they were 83% (55-99) including 18% (15-19) foam, 13% (7-24) and 49% (29-74). In control domes, tissue volume was 82% (35-100), bone volume 20% (9-27) and bone height 86% (60-100). The Polyfibre and Polyfoam material was excellently integrated. No adverse reactions were found in the surrounding tissues. Direct bone apposition was observed onto the material. In conclusion, Polyfibre and Polyfoam material had a positive effect on initial bone and tissue formation but was a hindrance to increasing tissue volume, bone volume or bone height at 2 months compared to control specimens. The Polyfibre and Polyfoam material provoked no adverse reactions in the surrounding tissues and allowed for extensive angiogenesis.

Enhanced bone augmentation by controlled release of recombinant human bone morphogenetic protein-2 from bioabsorbable membranes

BACKGROUND

The present study was undertaken to determine the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded biodegradable membranes on bone augmentation in a rabbit calvarial model.

METHODS

Five microg of rhBMP-2 was loaded into a stiff hemispherical dome membrane made of poly(L-lactide) and tricalcium phosphate (PLLA/TCP). The release kinetics of rhBMP-2 from the membrane were determined in vitro using a human BMP-2 immunoassay. Twelve rhBMP-2-loaded dome membranes (test group) and 12 control dome membranes (control group) were placed on the partial-thickness calvarial defects of 24 rabbits. The animals were sacrificed at 4 and 8 weeks, and undecalcified ground sections were prepared. Newly formed bone area and height were measured histomorphometrically and calculated by percentage ratio to the total submembranous space area and height below the dome.

RESULTS

In vitro release results demonstrated that rhBMP-2 was released consistently over a 4-week period following a high initial burst release on the first day. At both 4 and 8 weeks, histomorphometric analysis revealed that the test group showed significantly higher newly formed bone heights and areas than the control group (P < 0.01). In the control group, new bone height was 36.3% of the dome height and the new bone area reached 8.2% of the submembranous space area at 8 weeks, while the test group reached 87.3% and 35.4%, respectively.

CONCLUSION

These results suggest that the use of rhBMP-2-loaded PLLA/TCP membranes can result in additional bone augmentation, which is due to the osteoinductive properties of rhBMP-2 released from the membrane during healing.

Evaluation of implants placed with barrier membranes. A restrospective follow-up study up to five years

This follow-up study evaluated clinical and radiographic parameters of dental implants placed in combination with guided bone regeneration with barrier membranes. All implants functioned well up to 60 months after insertion. Forty-one patients, with a total of 72 augmented implants, who participated in a regular maintenance protocol, were investigated. Annual Periotest values (median value, - 3) revealed stable periimplant conditions and sustained osseointegration. At 6 months and annually thereafter up to five years, the radiographic evaluation yielded mean bone losses of 0.8, 1.25, 1.39, 1.42, 1.42 and 1.39 mm, respectively, with a range from 0 to 3.5 mm. No implant failures or losses were recorded. The results demonstrated stable periimplant conditions up to five years after membrane-protected osseous regeneration, with no significant differences in the radiographic bone level in regard to region, jaw or bone graft. Premature membrane exposure resulted in a significantly higher crestal bone loss up to 24 months. The newly formed bone appeared to be able to withstand functional loading for up to 60 months in a predictable manner.

A survey of clinical members of the Association of Dental Implantology in the United Kingdom. Part III. The use of augmentation techniques in dental implant surgery

The aims of the survey were to: (1) determine the use of the staged and simultaneous augmentation techniques; (2) determine trends in the use of barrier membranes; (3) establish the perceived reliability of techniques used to monitor implants that have undergone simultaneous augmentation; and (4) assess the use of biopsy techniques to confirm the histologic outcome of bone augmentation. One hundred seventy-two respondents replied to this section of the survey and indicated that the "staged" and "simultaneous" augmentation techniques were used in roughly equal numbers during 1997, and a wide range of complications was reported with the latter. The majority used barrier membranes to correct defects of between 5 and 10 mm3, and resorbable membranes were preferred. With regard to clinical techniques used to monitor augmented implants, these were mainly considered to be "adequate" or "poor." Tissue biopsy was recognized as an important tool for determining the outcome of augmentation procedures but was rarely used. The use of resorbable membranes is likely to increase. The diagnostic tools currently used to monitor augmented implants are considered to have limited reliability, and they should be evaluated by prospective, comparative studies. More widespread use of biopsy techniques might help establish an evidence base for the histologic outcome of augmentation materials and techniques.

Infectious risks for oral implants: a review of the literature

The use of oral implants in the rehabilitation of partially and fully edentulous patients is widely accepted even though failures do occur. The chance for implants to integrate can for example be jeopardised by the intra-oral presence of bacteria and concomitant inflammatory reactions. The longevity of osseointegrated implants can be compromised by occlusal overload and/or plaque-induced peri-implantitis, depending on the implant geometry and surface characteristics. Animal studies, cross-sectional and longitudinal observations in man, as well as association studies indicate that peri-implantitis is characterised by a microbiota comparable to that of periodontitis (high proportion of anaerobic Gram-negative rods, motile organisms and spirochetes), but this does not necessarily prove a causal relationship. However, in order to prevent such a bacterial shift, the following measures can be considered: periodontal health in the remaining dentition (to prevent bacterial translocation), the avoidance of deepened peri-implant pockets, and the use of a relatively smooth abutment and implant surface. Finally, periodontitis enhancing factors such as smoking and poor oral hygiene also increase the risk for peri-implantitis. Whether the susceptibility for periodontitis is related to that for peri-implantitis may vary according to the implant type and especially its surface topography.

Conditions for success in guided bone regeneration: retrospective study on 376 implant sites

BACKGROUND

Used alone or in association with bone, guided bone regeneration is a clinically accepted method to increase the volume of bone during implant placement. Concerns about appropriate surgical techniques and the predictability of the results questions still exist. The aim of this study was to assess the conditions for success.

METHODS

Three-hundred-seventy-six implants were placed in association with 214 non-resorbable membranes. In 109 implants, the membrane was secured on a blood clot; for 213 implants, membrane was placed with autogenous bone; and for 54 implants it was placed with allogenic bone. The surgical procedure, the primary closure, the timing of re-entry, and the density of regenerated tissue were studied.

RESULTS

In 19 membranes, barrier exposure occurred before 3 months in these instances, the regenerated tissue was removed; another 7 membranes were exposed between 3 and 6 months. The 188 non-exposed membranes were removed between 6 and 12 months. In cases of exposure before 3 months, the regenerated tissue was soft and then removed. After closure for 6 months or more, the regenerated tissue was dense and resistant to probe pressure. The best results were obtained when the membranes were placed with autogenous bone.

CONCLUSIONS

If all the clinical steps are appropriately followed, guided bone regeneration using an autogenous bone graft and implant placement is a predictable technique for increasing bone volume.

Distraction implants: a new operative technique for alveolar ridge augmentation

In the past alveolar ridge augmentation was mainly based on autologous or allogenic bone transplants. Since 1996 alveolar ridge distraction has enabled local osseous build-up without bone transplantation. The 'distraction implant', uniting qualities of a distraction apparatus with those of a dental implant, has been in use for three years at the Department of Oral and Maxillofacial Surgery of Graz University. Its application in patients with alveolar ridge atrophy and other defects is demonstrated and the first results are presented in this study. Three patients with severe alveolar ridge atrophy of the edentulous mandible, three with extensive alveolar ridge defects and three with local alveolar defects following traumatic loss of a single tooth were treated with distraction implants. Segmental osteotomy was carried out in all patients and one or two distraction implants were positioned. Following this alveolar ridge distraction was carried out. In seven cases there were no complications, whereas in one patient distraction was discontinued, and altogether two distraction implants had to be removed. All complications were treated by conventional operative techniques. Fifteen of 17 distraction implants were loaded successfully. Alveolar ridge distraction by means of distraction implants is an adequate method of alveolar ridge augmentation resulting in improved implant sites and gingival conditions. The segment for distraction should not be smaller than an upper central incisor. The implants can be used for prosthetic treatment, but long-term results are still not finalised.

Mandibular bone graft in the anterior maxilla for single-tooth implants. Presentation of surgical method

Nine patients with 10 implants were included in the study. A bone graft from the symphyseal region of the mandible was used to augment the ridge 4 months before implant insertion. All implant sites showed a sufficient amount of bone at the time of implant insertion. One implant was not integrated at the time of abutment connection. Bone resorption after augmentation was assessed by measurements of the width of the alveolar ridge at four different levels. The measurements were performed before and after the bone-grafting procedure, at implant insertion and at abutment connection. The bone resorption in the buccal/palatal direction was 60% when measured from the time of bone grafting to abutment connection. The bone resorption was already obvious after 4 months (25%). The results indicate that the described bone grafting technique is applicable in patients with a narrow alveolar ridge, even though the resorption of the graft was extensive.

Cytokine production by cells adherent to regenerative membranes

Since cytokines play a critical role in tissue regeneration, we have assayed cytokine production by cells from tissue adherent to regenerative membranes. Cells were recovered from Gore-tex membranes in guided tissue regeneration (GTR) procedures to regenerate that attachment apparatus around teeth and from Gore-tex augmentation membranes (GTAM) used for guided gone regeneration (GBR) procedures in edentulous ridge augmentation with or without implant placement. Cells were screened for mineralized nodule formation in vitro to mRNA analysis to demonstrate that they could form mineralized tissue. Production in interleukin-1 alpha (IL-1 alpha) interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) was evaluated by reverse transcribed-polymerase chain reaction (RT-PCR) of mRNA from rescued regenerative cells, human gingival fibroblasts and periodontal ligament (PDL) cells. Both the gingival fibroblast and PDL cells isolates produced all 4 cytokines. However, the cell isolates from the regenerative membranes had various profiles of cytokine expression. Most GTR cell isolates were positive for all 4 cytokines. IL-1 beta was produced by all 6 GTR cell isolates but was not detected at the same number of cycles of RT-PCR amplification in any of the 6 GBR cell isolates. IL-1 beta transcripts were also not observed in cells derived from a direct biopsy of GBR tissue. Cells were recovered from unexposed GBR membranes did not produce detectable amounts of IFN-gamma, whereas cells recovered from exposed GBR and all GTR membranes produced IFN-gamma. These findings indicate that cells from regenerative tissues express different cytokines and that exposure to the tissue to the oral cavity during healing may modulate this expression.

Periodontitis vs. peri-implantitis: the same disease? The same treatment?

The microbial flora in the natural dentition sulcus/pocket and the implant crevice/pocket is very similar in both health and disease. In health, coccal forms predominate, and in disease, large numbers of Gram-negative pathogens are associated with both tooth and implant. It has also been demonstrated that the bacteria in the partially edentulous implant case may be more pathogenic (especially Gram-negative rods and spirochetes) than in the fully edentulous case, indicating a possible seeding mechanism from tooth pocket to implant crevice. Detoxification procedures involving the use of tetracycline and citric acid prior to regenerative procedures with the use of barrier membranes and grafting materials are necessary, and the same problems attendant to premature exposure of the barrier membrane(s) in the natural dentition situation apply to the implant case. It is apparent that periodontitis = peri-implantitis in etiology and therapy.