Daniel Ferrari

Composition of supra- and subgingival biofilm of subjects with healthy and diseased implants

OBJECTIVES The purpose of this study was to compare the microbial composition of supra- and subgingival biofilm in subjects with and without peri-implantitis. MATERIAL AND METHODS Forty-four subjects (mean age 48.9 +/- 13.51 years) with at least one implant restored and functional for at least 2 years were assigned to two groups: a peri-implantitis group (n=22), consisting of subjects presenting peri-implant sites with radiographic defects >3 mm, bleeding on probing and/or suppuration; and a control group (n=22), consisting of subjects with healthy implants. The clinical parameters evaluated were plaque index, gingival bleeding, bleeding on probing, suppuration, probing depth and clinical attachment level. Supra- and subgingival biofilm samples were taken from the deepest sites of each implant and analyzed for the presence of 36 microorganisms by checkerboard DNA-DNA hybridization. RESULTS Higher mean counts of Porphyromonas gingivalis, Treponema denticola and Tannerella forsythia were observed in the peri-implantitis group, both supra- and subgingivally (P<0.05). The proportions of the pathogens from the red complex were elevated, while host-compatible beneficial microbial complexes were reduced in diseased compared with healthy implants. The microbiological profiles of supra- and subgingival environments did not differ substantially within each group. CONCLUSION Marked differences were observed in the composition of supra- and subgingival biofilm between healthy and diseased implants. The microbiota associated with peri-implantitis was comprised of more periodontal pathogenic bacterial species, including the supragingival biofilm.

Immunohistochemical characterization of guided bone regeneration at a dehiscence‐type defect using different barrier membranes: an experimental study in dogs

OBJECTIVES The aim of the present study was to evaluate immunohistochemically the pattern of guided bone regeneration (GBR) using different types of barrier membranes. MATERIAL AND METHODS Standardized buccal dehiscence defects were surgically created following implant bed preparation in 12 beagle dogs. Defects were randomly assigned to six different GBR procedures: a collagen-coated bone grafting material (BOC) in combination with either a native, three cross-linked, a titanium-reinforced collagen membrane, or expanded polytetrafluorethylene (ePTFE), or BOC alone. After 1, 2, 4, 6, 9, and 12 weeks of submerged healing, dissected blocks were processed for immunohistochemical (osteocalcin - OC, transglutaminase II - angiogenesis) and histomorphometrical analysis [e.g., bone-to-implant contact (BIC), area of new bone fill (BF)]. RESULTS In general, angiogenesis, OC antigen reactivity, and new bone formation mainly arose from open bone marrow spaces at the bottom of the defect and invaded the dehiscence areas along the implant surface and BOC. At 4 weeks, membranes supporting an early transmembraneous angiogenesis also exhibited some localized peripheral areas of new bone formation. However, significantly increasing BIC and BF values over time were observed in all groups. Membrane exposure after 10-12 weeks was associated with a loss of the supporting alveolar bone in the ePTFE group. CONCLUSION Within the limits of the present study, it was concluded that (i) angiogenesis plays a crucial role in GBR and (ii) all membranes investigated supported bone regeneration on an equivalent level.

Lateral ridge augmentation using particulated or block bone substitutes biocoated with rhGDF-5 and rhBMP-2: an immunohistochemical study in dogs.

OBJECTIVES The aim of the present study was to immunohistochemically evaluate lateral ridge augmentation using a particulated (BOG) or block (BOB) natural bone mineral biocoated with rhGDF-5 and rhBMP-2 in dogs. MATERIALS AND METHODS Three standardized box-shaped defects were surgically created at the buccal aspect of the alveolar ridge in each quadrant of eight beagle dogs. After 2 months of healing, the chronic-type defects were randomly allocated in a split-mouth design to either (i) BOG or (ii) BOB biocoated with (a) rhGDF-5 or (b) rhBMP-2, respectively. Uncoated grafts served as controls. After 3 and 8 weeks, dissected blocks were prepared for immunohistochemical [osteocalcin (OC)] and histomorphometrical analysis [e.g. area (mm(2)) of new bone fill (BF), newly formed mineralized (MT) and non-mineralized tissue (NMT)]. RESULTS rhBMP-2 biocoated BOG revealed significantly highest BF and MT values at 3 (upper and lower jaws - UJ/LJ - compared with BOG) and 8 weeks (UJ - compared with rhGDF-5). Biocoating of BOB using both rhGDF-5 and rhBMP-2 resulted in significantly increased MT values at 8 weeks (UJ/LJ - compared with BOB). In all groups, NMT adjacent to BOG and BOB scaffolds revealed pronounced signs of an OC antigen reactivity. CONCLUSIONS Within the limits of the present study, it was concluded that both rhGDF-5 and rhBMP-2 have shown efficacy; however, their bone regenerative effect was markedly influenced by the carrier.

Two‐year clinical results following treatment of peri‐implantitis lesions using a nanocrystalline hydroxyapatite or a natural bone mineral in combination with a collagen membrane

OBJECTIVES The aim of the present case series was to evaluate the 2-year results obtained following treatment of peri-implantitis lesions using either a nanocrystalline hydroxyapatite (NHA) or a natural bone mineral in combination with a collagen membrane (NBM+CM). MATERIAL AND METHODS Twenty-two patients suffering from moderate peri-implantitis (n=22 intra-bony defects) were randomly treated with (i) access flap surgery (AFS) and the application of NHA, or with AFS and the application of NBM+CM. Clinical parameters were recorded at baseline and after 12, 18, and 24 months of non-submerged healing. RESULTS Two patients from the NHA group were excluded from the study due to severe pus formation at 12 months. At 24 months, both groups revealed clinically important probing depth (PD) reductions (NHA: 1.5+/-0.6 mm; NBM+CM: 2.4+/-0.8 mm) and clinical attachment level (CAL) gains (NHA: 1.0+/-0.4 mm; NBM+CM: 2.0+/-0.8 mm). However, these clinical improvements seemed to be better in the NBM+CM group (difference between groups: PD reduction: 0.9+/-0.2 mm; CAL gain: 1.0+/-0.3 mm). CONCLUSION Both treatment procedures have shown efficacy over a period of 24 months, however, the application of NBM+CM may result in an improved outcome of healing.

Influence of different air-abrasive powders on cell viability at biologically contaminated titanium dental implants surfaces

Studies have indicated that oral biofilm formation at structured titanium surfaces interferes with cell adhesion and proliferation, and its removal by means of conventional treatment procedures may not be sufficient to render these surfaces biologically acceptable. Therefore, the aim of the study was to evaluate the influence of different air-abrasive powders on cell viability at biologically contaminated titanium dental implant surfaces. Intraoral splints were used to collect an in vivo biofilm on sandblasted and acid-etched titanium discs for 48 h. A single (1x) and repeated (2x) use of four different powders (amino acid glycine or sodium bicarbonate particles; range of mean particle size (d(v50)):20-75 microm) was applied at two distances (1 and 2 mm) and angles (30 degrees and 90 degrees) to the surfaces. Specimens (2x) were incubated with SaOs-2 cells for 7 days. Residual biofilm (RB) areas (%), and surface alterations (SEM) (1x and 2x), as well as SaOs-2 cell viability, expressed as mitochondrial cell activity (MA) (counts/second) (2x specimens), were assessed. Comparable mean RB areas were observed within and between groups after both 1x (RB: 0.0% +/- 0.0% to 5.7% +/- 5.7%) and 2x (RB: 0.0% +/- 0.0%) treatments. All surface treatments did not lead to MA (2x) values comparable to the sterile control group. However, sodium bicarbonate particles resulted in significantly higher MA (2x) values than amino acid glycine powders of different sizes. This was associated with pronounced alterations of the surface morphology (2x). Within the limits of the present study, it was concluded that SaOs-2 cell viability at biologically contaminated titanium surfaces was mainly influenced by the particle type of the powder.

Stability of crestal bone level at platform-switched non-submerged titanium implants: a histomorphometrical study in dogs.

OBJECTIVES To investigate the influence of platform switching on crestal bone level changes at non-submerged titanium implants over a period of 6 months. MATERIAL AND METHODS Titanium implants (n=72) were placed at 0.4 mm above the alveolar crest in the lower jaws of 12 dogs and randomly assigned to either matching or non-matching (circumferential horizontal mismatch of 0.3 mm) healing abutments. At 4, 8, 12, and 24 weeks, dissected blocks were processed for histomorphometrical analysis. Measurements were made between the implant shoulder (IS) and the apical extension of the long junctional epithelium (aJE), the most coronal level of bone in contact with the implant (CLB), and the level of the alveolar bone crest (BC). RESULTS At 24 weeks, differences in the mean IS-aJE, IS-CLB, and IS-BC values were 0.2 +/- 1.2, 0.3 +/- 0.7, and 0.3 +/- 0.8 mm at the buccal aspect, and 0.2 +/- 0.9, 0.3 +/- 0.5, and 0.3 +/- 0.8 mm at the lingual aspect, respectively. Comparisons between groups revealed no significant differences at either the buccal or the lingual aspects. CONCLUSIONS It was concluded that (i) bone remodelling was minimal in both groups and (ii) platform switching may not be of crucial importance for maintenance of the crestal bone level.

Biodegradation of different synthetic hydrogels made of polyethylene glycol hydrogel/RGD-peptide modifications: an immunohistochemical study in rats

AIM The aim of the present study was to investigate the pattern of biodegradation of different polyethylene glycol (PEG) hydrogel/RGD-peptide modifications in rats. MATERIAL AND METHODS Two different hydrogels were employed: (i) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and eight-arm PEG-acrylate, M(n)=2.3 kDa (PEG1); and (ii) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and four-arm PEG-acrylate, M(n)=15 kDa (PEG2). Both PEG1 and PEG2 were either used alone or combined with a nine amino acid cys-RGD peptide (RGD). A non-cross-linked porcine type I and III collagen membrane [BioGide (BG)] served as control. Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 60 wistar rats, which were divided into six groups (1, 2, 4, 8, 16, and 24 weeks). Specimens were prepared for histological (tissue integration, foreign body reactions, biodegradation) and immunohistochemical (angiogenesis) analysis. RESULTS All materials investigated revealed unimpeded and comparable tissue integration without any signs of foreign body reactions. While BG exhibited transmembraneous blood vessel formation at 1 week, all PEG specimens were just surrounded by a well-vascularized connective tissue. The hydrolytic disruption of PEG1 and PEG1/RGD specimens was associated with an ingrowth of blood vessels at 4 weeks. Biodegradation times were highest for PEG1 (24 weeks)>PEG1/RGD (16 weeks)>BG (4 weeks)>PEG2=PEG2/RGD (2 weeks). CONCLUSION Within the limits of the present study, it was concluded that (i) all materials investigated revealed a high biocompatibility and tissue integration, and (ii) hydrogel biodegradation was dependent on PEG composition.

Lateral ridge augmentation using equine- and bovine-derived cancellous bone blocks: a feasibility study in dogs.

OBJECTIVES The aim of the present study was to histologically evaluate and compare a new prototype collagen type I/III-containing equine- (EB) and a bovine- (BB) derived cancellous bone block in a dog model. MATERIALS AND METHODS Four standardized box-shaped defects were bilaterally created at the buccal aspect of the alveolar ridge in the lower jaws of five beagle dogs and randomly allocated to either EB or BB. Each experimental site was covered by a native (non-crosslinked) collagen membrane and left to heal in a submerged position for 12 weeks. Dissected blocks were processed for semi-/and quantitative analyses. RESULTS Both groups had no adverse clinical or histopathological events (i.e. inflammatory/foreign body reactions). BB specimens revealed no signs of biodegradation and were commonly embedded in a fibrous connective tissue. New bone formation and bony graft integration were minimal. In contrast, EB specimens were characterized by a significantly increased cell (i.e. osteoclasts and multinucleated giant cells)-mediated degradation of the graft material (P<0.001). The amount and extent of bone ingrowth was consistently higher in all EB specimens, but failed to reach statistical significance in comparison with the BB group (P>0.05). CONCLUSIONS It was concluded that the application of EB may not be associated with an improved bone formation than BB.

Influence of titanium implant surface characteristics on bone regeneration in dehiscence-type defects: an experimental study in dogs.

OBJECTIVES The aim of the present study was to compare bone regeneration in dehiscence-type defects at titanium implants with chemically modified sandblasted/acid-etched (modSLA) or dual acid-etched surfaces with a calcium phosphate nanometre particle modification (DCD/CaP). MATERIALS AND METHODS Buccal dehiscence-type defects were surgically created following implant site preparation in both the upper and the lower jaws of 12 fox hounds. Both types of implants were randomly allocated in a split-mouth design and left to heal in a submerged position for 2 and 8 weeks. Dissected blocks were processed for histomorphometrical analysis [e.g. new bone height (NBH), percentage of bone-to-implant contact (BIC), area of new bone fill (BF), and area of mineralized tissue (MT) within BF]. RESULTS At 2 and 8 weeks, both groups revealed comparable mean BF (2.3+/-0.6 to 2.5+/-0.6 mm(2)versus 2.0+/-0.6 to 1.4+/-0.5 mm(2)) and MT (31.1+/-14.3-83.2+/-8.2%versus 38.9+/-15.9-84.4+/-6.3%) values. However, modSLA implants revealed significantly higher mean NBH (2.4+/-0.8 to 3.6+/-0.3 mm versus 0.9+/-0.8 to 1.8+/-1.4 mm) and BIC (53.3+/-11.3-79.5+/-6.6%versus 19.3+/-16.4-47.2+/-30.7%) values than DCD/CaP implants. CONCLUSION ModSLA implants may have a higher potential to support osseointegration in dehiscence-type defects than DCD/CaP implants.

Influence of direct laser fabrication implant topography on type IV bone: A histomorphometric study in humans

The aim of this histologic study was to evaluate the influence of the direct laser fabrication (DFL) surface topography on bone-to-implant contact (BIC%), on bone density in the threaded area (BA%) as well as bone density outside the threaded area (BD%) in type IV bone after 8 weeks of unloaded healing. Thirty patients (mean age 51.34 +/- 3.06 years) received 1 micro-implant (2.5-mm diameter and 6-mm length) each during conventional implant surgery in the posterior maxilla. Thirty micro-implants with three topographies were evaluated: 10 machined (cpTi); 10 sandblasted and acid etched surface (SAE) and 10 DFL micro-implants. After 8 weeks, the micro-implants and the surrounding tissue were removed and prepared for histomorphometric analysis. Four micro-implants (2 cpTi, 1 SAE and 1DLF) showed no osseointegration after the healing period. Histometric evaluation indicated that the mean BIC% was higher for the DFL and SAE surfaces (p = 0.0002). The BA% was higher for the DFL surface, although there was no difference with the SAE surface. The BD% was similar for all topographies (p > 0.05). Data suggest that the DFL and SAE surfaces presented a higher bone-to-implant contact rate compared with cpTi surfaces under unloaded conditions, after a healing period of 8 weeks.