Cobalt chromium alloys in fixed prosthodontics: Investigations of mechanical properties and microstructure.

STATEMENT OF PROBLEM: Cobalt chromium (Co-Cr) alloys possess beneficial mechanical properties because alloys, even in thin sections, can resist high mastication forces and exhibit an acceptable bond to the surface porcelain layer. Traditional manufacturing techniques of Co-Cr alloys such as casting have been replaced with newer fabrication techniques, such as milling, laser melting, and presintered milling. Despite scarce documentation, these new manufacturing techniques are being used to fabricate dental and implant constructions. PURPOSE: This in vitro study investigates the hardness, yield strength, elastic modulus, and microstructure of the most commonly used Co-Cr alloys for fixed prosthodontics based on manufacturing technique. In addition, this study investigates the effect of heat treatment on the mechanical properties and microstructure of these materials. MATERIAL AND METHODS: Five Co-Cr alloys were included (dumbbell and rectangular shaped) based on four manufacturing techniques: cast, milled, laser melted, and presintered milled. Commercially pure titanium grade 4 and titanium-6 aluminum-4 vanadium ELI (extra low interstitial) were included for comparison, and yield strength and elongation after fracture were evaluated. The specimens were tested for hardness using the Vickers test and for elastic modulus using a nondestructive impulse excitation technique. The microstructure of selected specimens was analyzed using focused ion beam-scanning electron microscopy (FIB-SEM) and energy dispersive X-ray spectroscopy (EDS). RESULTS: The mechanical properties depend on the manufacturing technique used; the laser-melted and presintered Co-Cr specimens demonstrated the highest mechanical properties, followed by the milled and cast groups. Both the laser-melted and the presintered milled Co-Cr specimens showed smaller grain size compared with the cast and milled Co-Cr specimens. The titanium-6 aluminum-4 vanadium ELI demonstrated higher hardness and yield strength compared to commercially pure titanium grade 4. No major differences were observed for the selected materials regarding the mechanical properties and microstructural appearance after heat treatment. CONCLUSIONS: The laser melting and presintered milling techniques produced higher mechanical properties compared with the cast and milled Co-Cr. These findings were confirmed through microstructural analysis with respect to the grain size, precipitation, and number of pores.

Biopsies from the Distal Radius after Implantation of Calcium Phosphate Cement.

Background: Calcium Phosphate (CaP) bone cement is gradually replaced by new bone when used as a gap-filler. Details of the re-modelling process are still unclear. Uncertainty is also present as to the possible release of cement particles during the resorption phase causing local soft tissue reactions. The objective of this study was to perform a comprehensive histological investigation of the injectable CaP bone cement used as a void filler in corrective radius osteotomies and adjacent tissue reactions. Methods: Fourteen patients, median age 56 years (18-72), 4 men/10 women, underwent removal of distal radius plates (11 dorsal/3 volar) due to tenosynovitis-like symptoms. Eleven study patients went through corrective osteotomies with CaP bone cement and three were control patients. Previous surgery in three controls consisted in (1) corrective osteotomy with bone graft (dorsal plate), and (2) plated distal radius fractures (1 dorsal/1 volar plate). Biopsies were taken of bone-cement-bone junctions (11), bone-bone graft-bone junctions (1), bone (2) and juxtaposing soft tissue (14). The interval from corrective CaP cement surgery to biopsy was median 1.1 (0.6-2.3) years. Results: Biopsies of bone-cement junctions showed the different stages of new bone formation from CaP to immature bone and later mature well-organised bone. The cement showed signs of osteoclast-mediated resorption. Cement particles, macrophages, multinucleated giant cells (MNGC) and plasma cells were observed in most soft tissue biopsies. MNGC with internalised particles were seen. Macrophages were found along and/or within tendon sheaths in all patients in both groups, but rarely containing cement particles. Conclusions: Gradual re-modelling of the cement into well-organised bone was observed confirming osteoclast-osteoblast coupling. There was no indication that cement particles were the cause of the tenosynovitis-like symptoms.

Effect of airborne-particle abrasion and polishing on novel translucent zirconias: Surface morphology, phase transformation and insights into bonding.

PURPOSE: The purpose this study was to investigate the effect of Kern´s air-borne particle abrasion protocol (KAPA) and polishing on two translucent zirconias (4Y, 5Y-zirconias) compared to a traditional zirconia (3Y-zirconia). METHODS: Two different surface treatments were analysed by X-ray diffraction (XRD) and interferometry 1) KAPA (0.1 MPa, 50 µm alumina, 10-12 mm distance, 15 sec and 30 sec and cleaning in ultrasound using isopropyl alcohol 99%) and 2) Clinical-delivery polishing paste (Zircon Brite, Dental Ventures, USA). Shear-bond strength tests (SBS's) were performed with a highly polished and virtually flat surface in combination with a 10-MDP based cement and a surface modified by KAPA in combination with zinc phosphate cement. The SBS was expressed in terms of MPa. RESULTS: The mean values for monoclinic content were 13 wt%, 7 wt% and 2 wt% for 3Y-, 4Y- and 5Y-zirconias respectively, no differences were found between 15 and 30 seconds. Polishing did not result in phase transformation to monoclinic phase in any of the zirconias. The rhombohedral phase was identified in all types of zirconias regardless of surface treatment. Shear-bond strength tests showed 5 MPa for polished/10-MDP based cement and 3 MPa for KAPA/ Zinc phosphate. Statistically significant differences were found between the two different surface treatments but not between the types of zirconias. CONCLUSIONS: KAPA for 15 sec seems to be equal to 30 sec regarding morphology and phase transformation. Sole micro-retention appears not to be fully responsible for the bonding phenomena of 10-MDP and zirconia that underwent KAPA.

Inflammatory Response to Cobalt-Chromium Alloys Fabricated With Different Techniques.

OBJECTIVES: To explore the in vitro cytokine expression of human peripheral blood mononuclear cells exposed to cobalt-chromium alloys, manufactured with different techniques, in comparison with commercially pure titanium grade 4 and titanium alloy grade 23. MATERIAL AND METHODS: Peripheral blood mononuclear cells (PBMC) were collected from 10 healthy blood donors and exposed to machine-ground coin-shaped: (a) cobalt-chromium (Co-Cr) specimens (n = 5) manufactured by four techniques, i.e. cast, milled, laser melted and presintered milled; (b) commercially pure titanium grade 4; and (c) titanium alloy grade 23. The cells were cultured for 4, 24 and 72 hours followed by investigations of pro- and anti-inflammatory cytokine release using Bio-Plex Pro™. RESULTS: In general, the PBMC produced significantly more cytokines when exposed to the cast and presintered milled Co-Cr materials compared to laser melted, milled Co-Cr and titanium materials. CONCLUSIONS: Within the limitation of the present study, it may be suggested that cast and presintered milled cobalt-chromium alloys provoke a stronger inflammatory response compared to milled and laser melted cobalt-chromium alloys and titanium materials.

Cobalt-chromium alloys fabricated with four different techniques: Ion release, toxicity of released elements and surface roughness.

OBJECTIVE: To investigate the metal ion release, surface roughness and cytoxicity for Co-Cr alloys produced by different manufacturing techniques before and after heat treatment. In addition, to evaluate if the combination of materials affects the ion release. METHODS: Five Co-Cr alloys were included, based on four manufacturing techniques. Commercially pure titanium, CpTi grade 4 and a titanium alloy were included for comparison. The ion release tests involved both Inductive Coupled Plasma Optical Emission Spectrometry and Inductive Coupled Plasma Mass Spectrometry analyses. The surface analysis was conducted with optical interferometry. Cells were indirectly exposed to the materials and cell viability was evaluated with the MTT (3-(4.5-dimethylthiazol-2-yl)-2.5-diphenyltetrazolium bromide) method. RESULTS: All alloys showed a decrease of the total ion release when CpTi grade 4 was present. The total ion release decreased over time for all specimens and the highest ion release was observed from the cast and milled Co-Cr alloy in acidic conditions. The cast and laser-melted Co-Cr alloy and the titanium alloy became rougher after heat treatment. All materials were within the limits of cell viability according to standards. SIGNIFICANCE: The ion release from Co-Cr alloys is influenced by the combination of materials, pH and time. Surface roughness is influenced by heat treatment. Furthermore, both ion release and surface roughness are influenced by the manufacturing technique and the alloy type. The clinical implication needs to be further investigated.

Early Cup Loosening After Metal-on-Metal Total Joint Replacement of the Trapeziometacarpal Joint: A Retrieval Study.

PURPOSE: To investigate the possible mechanisms behind early cup loosening in a metal-on-metal trapeziometacarpal joint replacement. METHODS: The trapezia from 5 female patients were removed as part of a salvage procedure after a median of 22 months (range, 7-43 months) after implantation. Three osteoarthritic patients with symptomatic cup loosening and 2 with instability had a median age of 62 years (range, 59-65 years) at primary surgery. The trapezia with cups in situ were preserved and processed for histomorphometry. Studies with laser ablation inductively coupled plasma mass spectrometry and scanning electron microscopy with energy dispersive x-ray spectroscopy were also performed on 2 of the specimens. RESULTS: In all 5 specimens, osteolytic lesions undermined the cups and were also seen at the cup edges, completely surrounding the loose cups. Large amounts of dark particular material were seen in the periprosthetic tissues, mostly internalized by macrophages. The presence of chrome and cobalt in these regions was confirmed. Four of the 5 cups showed marked or complete loss of hydroxyapatite. CONCLUSIONS: We have found several possible explanations for the poor performance of this cup, including its cannulated design and metal-on-metal bearing. The changes seen are early and advanced, raising serious concerns about the implant and particularly the articulation. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.

Biofilm formation on polyetheretherketone and titanium surfaces.

Objective: Polyetheretherketone (PEEK) is a polymer used in devices in orthopedic and dental rehabilitation. The aim of this in vitro study was to compare biofilm formation by a range of important oral bacterial species on PEEK, blasted PEEK, commercially pure titanium (cp-Ti), and titanium-6 aluminium-4 vanadium (Ti6Al4V). Material and methods: Coin-shaped samples were manufactured, and the surfaces were characterized using optical interferometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and contact angle measurements. Bacterial species of Streptococcus sanguinis, Streptococcus oralis, Enterococcus faecalis, and Streptococcus gordonii were cultured on the four material surfaces for varying amounts of time. Biofilms were quantified following staining with crystal violet. Results: Roughness and contact angle results showed blasted PEEK > PEEK > cp-Ti = Ti6Al4V. There was increased biofilm formation on blasted PEEK by S. sanguinis, S. oralis, and S. gordonii, whereas the bacterial adhesion was similar on PEEK, cp-Ti, and Ti6Al4V. The bacterial growth of E. faecalis was significantly higher on cp-Ti compared with the other three groups. Conclusion: The results, taking into consideration the biofilm formation, suggest that PEEK should perform as well as cp-Ti or TiAl6V4 when used as a dental restorative material.

Aseptic Ligatures Induce Marginal Peri-Implant Bone Loss-An 8-Week Trial in Rabbits.

The clinical value of ligature-induced experimental peri-implantitis studies has been questioned due to the artificial nature of the model. Despite repeated claims that ligatures of silk, cotton and other materials may not induce bone resorption by themselves; a recent review showed that the tissue reaction toward them has not been investigated. Hence, the current study aimed to explore the hard and soft tissue reactions toward commonly used ligature materials. A total of 60 dental implants were inserted into the femur (n = 20) and tibia (n = 40) of 10 rabbits. The femoral implants were ligated with sterile 3-0 braided silk in one leg and sterile cotton retraction chord in the other leg. The tibial implants were ligated with silk or left as non-ligated controls. All wounds were closed in layers. After a healing time of 8 weeks, femoral (silk versus cotton) and proximal tibial (silk versus non-ligated control) implants were investigated histologically. Distal tibial (silk versus non-ligated control) implants were investigated with real time polymerase chain reaction (qPCR). The distance from the implant-top to first bone contact point was longer for silk ligated implants compared to non-ligated controls (p = 0.007), but did not vary between cotton and silk. The ligatures triggered an immunological reaction with cell infiltrates in close contact with the ligature materials, adjacent soft tissue encapsulation and bone resorption. qPCR further demonstrated an upregulated immune response toward the silk ligatures compared to non-ligated controls. Silk and cotton ligatures provoke foreign body reactions of soft tissue encapsulation type and bone resorption around implants in the absence of plaque.

Chemical Bonding to Novel Translucent Zirconias: A Mechanical and Molecular Investigation.

PURPOSE: To investigate direct bonding of a 10-MDP-based cement to two novel translucent yttria-stabilized tetragonal zirconia polycrystal ceramics (4Y-TZP, 5Y-TZP) and observe the influence of thermocycling on this bonding. MATERIALS AND METHODS: Powders of presintered and isostatically pressed 5Y-TZP, 4Y-TZP and 3Y-TZP were mixed with a 10-MDP-based cement (Panavia F 2.0), then stored in deionized water for 48 h at 37°C or thermocycled 10,000 times. Raman spectroscopy and Fourier-transform infrared spectroscopy were used to assess the presence of a functional group (PO32-) that could indicate bonding before and after thermocycling. X-ray photoelectron spectroscopy was used to identify the presence of the suspected Zr-O-P bond in the same specimens. A shear-bond strength (SBS) test was conducted based on ISO 29022:2013. RESULTS: Marked peaks assigned to the asymmetric vibrations of the PO32- functional group were observed in both zirconias before and after thermocycling. The binding energy corresponding to Zr-O-P interactions (531.5 eV) was masked by the aluminosilicate in the filler of the cement. Shear bond strengths were approximately 20 MPa after water storage and approximately 6 MPa after thermocycling. No differences were found between the control group and the translucent zirconias. CONCLUSION: Direct bonding of the 10-MDP-based cement to both 4Y-TZP and 5Y-TZP was highly plausible. Both 4Y-TZP and 5Y-TZP may be promising alternatives to glass-ceramic restorations.

A new synthetic granular calcium phosphate compound induces new bone in a sinus lift rabbit model.

OBJECTIVES: The aim of this study was to investigate if a synthetic granular calcium phosphate compound (CPC) and a composite bisphosphonate-linked hyaluronic acid-calcium phosphate hydrogel (HABP·CaP) induced similar or more amount of bone as bovine mineral in a modified sinus lift rabbit model. MATERIAL AND METHODS: Eighteen adult male New Zeeland White rabbits, received randomly one of the two test materials on a random side of the face, and bovine mineral as control on the contralateral side. In a sinus lift, the sinus mucosa was elevated and a titanium mini-implant was placed in the alveolar bone. Augmentation material (CPC, HABP·CaP or bovine bone) was applied in the space around the implant. The rabbits were euthanized three months after surgery and qualitative and histomorphometric evaluation were conducted. Histomorphometric evaluation included three different regions of interest (ROIs) and the bone to implant contact on each installed implant. RESULTS: Qualitative assessment (p = <.05), histomorphometric evaluations (p = < .01), and implant incorporation (p = <.05) showed that CPC and bovine mineral induced similar amount of bone and more than the HABP·CaP hydrogel. CONCLUSION: CPC induced similar amount of bone as bovine mineral and both materials induced more bone than HABP·CaP hydrogel. CLINICAL SIGNIFICANCE: The CPC is suggested as a synthetic alternative for augmentations in the maxillofacial area.

Limited Effect of Cement Material on Stress Distribution of a Monolithic Translucent Zirconia Crown: A Three-Dimensional Finite Element Analysis.

PURPOSE: The literature shows that the performance of densely sintered zirconia single crowns seems to be unaffected by the cement material. The purpose of this study was to evaluate the effects of various cement materials on the stress distribution in a monolithic translucent zirconia crown. MATERIALS AND METHODS: A crown-cement-dentin complex was modeled. Six cements were evaluated: zinc phosphate, glass-ionomer, resin-modified glass-ionomer, dual-cure resin, calcium aluminate-based, and a theoretical or conceptual cement with mechanical properties close to those of dentin (ie, monoblock cement). RESULTS: While varying stress concentrations were found within the cements, the stress concentrations in the crown and dentin were consistent irrespective of cement material. CONCLUSION: Within the limitations of this study, it can be concluded that cement material had a negligible effect on stress distribution in the monolithic zirconia crown.

Cobalt-chromium alloys in fixed prosthodontics in Sweden.

Aim: The aim of this study was to compile the usage of Co-Cr alloys in fixed prosthodontics (FP) among dental laboratories in Sweden. Methods: From March to October 2015, questionnaires were sent to 542 registered dental laboratories in Sweden. The questionnaires were divided in two parts, one for fixed dental-supported prosthodontics (FDP) and one for fixed implant-supported prosthodontics (FIP). Reminders were sent three times. Results: In total of 542 dental laboratories, 55% answered the questionnaires. Most dental laboratories use Co-Cr in FP, 134 (74%) in FDP and 89(66%) in FIP. The laboratories used Co-Cr alloys of various compositions in the prostheses, 35 for FDP and 30 for FIP. The most commonly used Co-Cr alloys for tooth-supported FDPs were (a) Wirobond® 280, (b) Cara SLM and (c) Wirobond® C. For implant-supported frameworks the frequently used alloys were: (a) Cara SLM, (b) Cara Milled and (c) Wirobond® 280. Except for the difference in composition of these alloys, they were also manufactured with various techniques. In tooth-supported prostheses the dominating technique was the cast technique while newer techniques as laser-sintering and milling were more commonly reported for implant-supported constructions. A fourth technique; the 'pre-state' milling was reported in FDP. Conclusion: More than 30 different Co-Cr alloys were reported as being used in FP. Thus, there is a need for studies exploring the mechanical and physical behavior and the biological response to the most commonly used Co-Cr alloys.

Bone tissue response following local drug delivery of bisphosphonate through titanium oxide nanotube implants in a rabbit model.

OBJECTIVES: The objective of this study was to evaluate whether surface chemistry-controlled TiO2 nanotube structures may serve as a local drug delivery system for zoledronic acid improving implant-bone support. METHODS: Twenty-four screw-shaped Ti implants with surface chemistry-controlled TiO2 nanotube structures were prepared and divided into a zoledronic acid-formatted test and a native control group. The implants were inserted into contra-lateral femoral condyles in 12 New Zealand White rabbits. Bone support was evaluated using resonance frequency analysis (RFA) and removal torque (RTQ), as well as histometric analysis following a 3-weeks healing interval. RESULTS: Zoledronic acid-formatted TiO2 nanotube test implants showed significantly improved implant stability and osseointegration measured using RFA and RTQ compared with control (p < 0.05), and showed significantly enhanced new bone formation within the root of the threads compared with control (p < 0.05). CONCLUSIONS: TiO2 nanotube implants may prove to be a significant delivery system for drugs or biologic agents aimed at supporting local bone formation. Additional study of candidate drugs/agents, optimized dosage and release kinetics is needed prior to evaluation in clinical settings.

Molecular Activity and Osseointegration After Single-Dose Irradiation: An In Vivo Study.

PURPOSE: Irradiation results in deleterious effects on bone healing and integration of titanium implants. The impact of irradiation on osseointegration has been demonstrated in histologic studies, but the underlying molecular mechanisms have not been explored. This study aimed to investigate the effects of single-dose irradiation on the expression of biologic mediators crucial for inflammation, bone formation, and bone remodeling and to relate these molecular activities to implant stability after a 5-week healing period. MATERIALS AND METHODS: A rat tibia model was used. An external single-dose irradiation of 20 Gy was administered to one leg while the second leg was used as a control. After 8 weeks, the irradiated and non-irradiated tibiae received titanium implants. Five weeks following implantation, implant stability was evaluated by removal torque measurement. Then, the implant and the bone surrounding the implant were retrieved for gene expression analysis of the implant-adherent cells and peri-implant bone, respectively. RESULTS: Irradiation resulted in 55% reduction in removal torque. The implant-adherent cells in irradiated sites revealed downregulation of genes related to bone formation (ALP and OC) and upregulation of proinflammatory (TNF-α) and pro-fibrogenic (PDGF-b) genes. Conversely, the peri-implant bone in irradiated sites revealed upregulation of bone formation and bone remodeling genes. Removal torque showed a negative correlation with pro-inflammatory activity and a positive correlation with osteoblastic activity in the implant-adherent cells. CONCLUSION: The impact of high (20 Gy) single-dose irradiation on osseointegration involves a reduction in bone formation activity and upregulation of pro-inflammatory and pro-fibrogenic activities in the implant-adherent cells. It is also suggested that this single-dose irradiation elicits a different molecular pattern at a distance from the implant surface, characterized by increased bone formation and remodeling activities in the peri-implant bone.

Access to the brain parenchyma using endovascular techniques and a micro-working channel.

OBJECTIVE Several older studies report a low risk for parenchymal access to the CNS by surgical techniques. In more recent studies, including those with post-puncture CT scans, there are indications that the risk of bleeding might approach 8%. New therapies, such as those that use viral vectors, modified mRNA, or cell transplantation, will probably warrant more parenchymal access to the CNS. Other minimally invasive routes might then be tempting to explore. This study was designed in 2 parts to address the possibility of using the endovascular route. The first aim was to test the ability to create a parenchymal micro-working channel to the CNS in macaque monkeys through the vessel wall. Second, the biocompatibility of a device-associated, detached, distal securing plug that was made of nitinol was investigated in swine for 1 year. METHODS Trans-vessel wall intervention in the middle cerebral artery and associated cerebral parenchyma was performed in 4 rhesus macaque monkeys using a full clinical angiography suite. A contrast agent and methylene blue were injected to test the working channel and then detached at the distal end to act as a securing plug through the vessel wall. One-year follow-ups were also performed using angiography and histological analysis in 10 swine with 24 implants that were distributed in the external carotid artery tree. RESULTS The cerebral interventions were performed without acute bleeding. Both the contrast agent and methylene blue were infused into the brain parenchyma and subarachnoidal space via the endovascular micro-working channel (7 injections in 4 animals). In the 1-year follow-up period, the implant that was left in the external carotid vessel wall in the swine was covered by the endothelium, which was followed by dislodgement just outside the blood vessel with thin capsule formation. No stenosis in the artery was detected on 1-year angiography. The animals showed normal behavior and blood sample results during the follow-up period. This is the first histological demonstration of nitinol biocompatibility when the implant is positioned through an arterial wall and indicates that the trans-vessel wall technique is not comparable with stent placement and its ability to induce intimal hyperplasia and restenosis. CONCLUSIONS This study demonstrates that the trans-vessel wall technique is applicable to brain intervention in macaque monkeys, providing a micro-working channel for delivery or sampling. The long-term follow-up study of the detached device in swine showed no clinical or biochemical complications and a normal angiography appearance.

Improved osseointegration and interlocking capacity with dual acid-treated implants: a rabbit study.

AIM: To investigate how osseointegration is affected by different nano- and microstructures. The hypothesis was that the surface structure created by dual acid treatment (AT-1), applied on a reduced topography, might achieve equivalent biomechanical performance as a rougher surface treated with hydrofluoric acid (HF). MATERIALS AND METHODS: In a preclinical rabbit study, three groups (I, II, and III) comprised of test and control implants were inserted in 30 rabbits. The microstructures of the test implants were either produced by blasting with coarse (I) or fine (II) titanium particles or remained turned (III). All test implants were thereafter treated with AT-1 resulting in three different test surfaces. The microstructure of the control implants was produced by blasting with coarse titanium particles thereafter treated with HF. The surface topography was characterized by interferometry. Biomechanical (removal torque) and histomorphometric (bone-implant contact; bone area) performances were measured after 4 or 12 weeks of healing. RESULTS: Removal torque measurement demonstrated that test implants in group I had an enhanced biomechanical performance compared to that of the control despite similar surface roughness value (Sa ). At 4 weeks of healing, group II test implants showed equivalent biomechanical performance to that of the control, despite a decreased Sa value. Group III test implants showed decreased biomechanical performance to that of the control. CONCLUSIONS: The results of the present study suggest that nano- and microstructure alteration by AT-1 on a blasted implant might enhance the initial biomechanical performance, while for longer healing time, the surface interlocking capacity seems to be more important.

Inflammatory cytokine release is affected by surface morphology and chemistry of titanium implants.

To investigate in vitro cellular cytokine expression in relation to commercially pure titanium discs, comparing a native surface to a fluorinated oxide nanotube surface. Control samples pure titanium discs with a homogenous wave of the margins and grooves and an often smeared-out surface structure. Test samples pure titanium discs with a fluorinated titanium oxide chemistry and surface morphology with nanopore/tube geometry characterized by ordered structures of nanotubes with a diameter of ≈ 120 nm, a spacing of ≈ 30 nm, and a wall thickness of ≈ 10 nm. Cross-section view showed vertically aligned nanotubes with similar lengths of ≈ 700 nm. Peripheral blood mononuclear leucocytes were cultured for 1, 3, and 6 days according to standard procedures. BioPlex Pro™ assays were used for analysis and detection of cytokines. Selected inflammatory cytokines are reported. A pronounced difference in production of the inflammatogenic cytokines was observed. Leucocytes exposed to control coins produced significantly more TNF-α, IL-1ß, and IL-6 than the test nanotube coins. The effect on the TH2 cytokine IL-4 was less pronounced at day 6 compared to days 1 and 3, and slightly higher expressed on the control coins. The morphology and surface chemistry of the titanium surface have a profound impact on basic cytokine production in vitro. Within the limitations of the present study, it seems that the fluorinated oxide nanotube surface results in a lower inflammatory response compared to a rather flat surface that seems to favour inflammation.

Comparing and visualizing titanium implant integration in rat bone using 2D and 3D techniques.

The aim was to compare the osseointegration of grit-blasted implants with and without a hydrogen fluoride treatment in rat tibia and femur, and to visualize bone formation using state-of-the-art 3D visualization techniques. Grit-blasted implants were inserted in femur and tibia of 10 Sprague-Dawley rats (4 implants/rat). Four weeks after insertion, bone implant samples were retrieved. Selected samples were imaged in 3D using Synchrotron Radiation-based µCT (SRµCT). The 3D data was quantified and visualized using two novel visualization techniques, thread fly-through and 2D unfolding. All samples were processed to cut and ground sections and 2D histomorphometrical comparisons of bone implant contact (BIC), bone area (BA), and mirror image area (MI) were performed. BA values were statistically significantly higher for test implants than controls (p < 0.05), but BIC and MI data did not differ significantly. Thus, the results partly indicate improved bone formation at blasted and hydrogen fluoride treated implants, compared to blasted implants. The 3D analysis was a valuable complement to 2D analysis, facilitating improved visualization. However, further studies are required to evaluate aspects of 3D quantitative techniques, with relation to light microscopy that traditionally is used for osseointegration studies.

A randomized and controlled clinical trial of two different compositions of deproteinized bovine bone and autogenous bone used for lateral ridge augmentation.

OBJECTIVE: The aim of the study was to radiologically and histologically evaluate the graft healing and volumetric changes after lateral augmentation with two different compositions of deproteinized bovine bone (DPBB) and autogenous bone (AB). MATERIAL AND METHODS: Thirteen patients with a mean age of 59.6 ± 12.1 years (six men and seven women) were included in this randomized and controlled trial, designed as a split-mouth study. Ten edentulous and four partially edentulous jaws with an alveolar ridge width of ≤4 mm were laterally augmented with a graft composition of 60 : 40 (DPBB/AB) on one side and 90 : 10 (DPBB/AB) on the contralateral side. Cone beam computed tomography (CB/CT) was obtained immediately postoperatively and after a healing period of 7.5 months. Width changes were measured on CB/CT scans. After a mean healing period of 8.1 months (range, 7.9-8.3), biopsies were retrieved perpendicular to the crest from each graft by means of a trephine bur. Histomorphometry was performed, and the following variables were recorded: Ingrowth of new bone (percentage of total graft width), percentage of DPBB, bone and soft tissue, and percentage of DPBB particles in contact with bone. RESULTS: The mean gained width of the alveolar crest after 7.5 months was significantly more for the 60 : 40 mixture compared with the 90 : 10 mixture, 3.5 (±1.3) mm and 2.9 (±1.3) mm, respectively. There was a significant difference in graft width reduction between 60 : 40 and 90 : 10 after 7.5 months, 37 (±19.9)% and 46.9 (±23.5)%, respectively. New bone ingrowth had occurred in 82.1 (±23.3)% and 82.3 (±26.6)% of the graft, respectively. There were no statistical differences between fractions of different tissues between the 90 : 10 and 60 : 40 compositions. However, there were significantly more soft tissue and less new bone formation closer to the periosteum compared with the graft portion closer to the residual bone in both 60 : 40 and 90 : 10 compositions. CONCLUSIONS: There was significantly less graft width reduction with a mixture of 60 : 40 (DPBB/AB) compared with a mixture of 90 : 10 composition, but the results from the histomorphometry showed no statistical differences comparing the groups.

Implant stability and bone remodeling after 3 and 13 days of implantation with an initial static strain.

OBJECTIVE: Bone is constantly exposed to dynamic and static loads, which induce both dynamic and static bone strains. Although numerous studies exist on the effect of dynamic strain on implant stability and bone remodeling, the effect of static strain needs further investigation. Therefore, the effect of two different static bone strain levels on implant stability and bone remodeling at two different implantation times was investigated in a rabbit model. METHODS: Two different test implants with a diametrical expansion of 0.15 mm (group A) and 0.05 mm (group B) creating initial static bone strains of 0.045 and 0.015, respectively. The implants were inserted in the proximal tibial metaphysis of 24 rabbits to observe the biological response at implant removal. Both groups were compared to control implants (group C), with no diametrical increase. The insertion torque (ITQ) was measured to represent the initial stability and the removal torque (RTQ) was measured to analyze the effect that static strain had on implant stability and bone remodeling after 3 and 13 days of implantation time. RESULTS: The ITQ and the RTQ values for test implants were significantly higher for both implantation times compared to control implants. A selection of histology samples was prepared to measure bone to implant contact (BIC). There was a tendency that the BIC values for test implants were higher compared to control implants. CONCLUSION: These findings suggest that increased static bone strain creates higher implant stability at the time of insertion, and this increased stability is maintained throughout the observed period.