A randomized, controlled, clinical study on a new titanium oxide abutment surface for improved healing and soft tissue health.

BACKGROUND: A newly developed, anodized titanium oxide surface containing anatase has been reported to have antimicrobial properties that could reduce bacterial adherence to abutments. PURPOSE: To investigate if abutments with the anodized surface improve healing and soft tissue health in a randomized controlled study. MATERIALS AND METHODS: Test abutments with a nanostructured anodized surface were compared with control machined titanium abutments. In total, 35 subjects each received a pair of test and control abutments. The primary endpoint was reduction of biofilm formation at test abutments at the 6-week follow-up. Secondary endpoints included several soft tissue assessments. qPCR for gene markers was used to indirectly evaluate healing and soft tissue health. RESULTS: No significant differences in biofilm formation were observed between test and control abutments, but soft tissue bleeding upon abutment removal was significantly lower for test abutments compared with control abutments (P = 0.006) at 6 weeks. Keratinized mucosa height was significantly greater at test abutments compared with control abutments at the 6-week, 6-month, and 2-year follow-ups. Significant gene expression differences indicated differences in healing and tissue remodeling. CONCLUSIONS: Abutments with an anodized and nanostructured surface compared with a conventional, machined titanium surface had no significant effect on bacterial colonization and proteolytic activity but were associated with better soft tissue outcomes such as a lower bleeding index at abutment removal and consistently greater height of keratinized mucosa throughout the 2-year follow-up, suggesting improved surface-dependent peri-implant healing and soft tissue health.

A controlled, cross-sectional exploratory study on markers for the plasminogen system and inflammation in crevicular fluid samples from healthy, mucositis and peri-implantitis sites.

PURPOSE: To investigate expression of gene markers for the plasminogen system, inflammation, and bone resorption/remodelling in peri-implant crevicular fluid samples from healthy subjects, subjects with mucositis and subjects with peri-implantitis. A possible inhibitory effect of suppuration on the analysis of gene expression in samples from subjects with peri-implantitis was also analysed. MATERIALS AND METHODS: Peri-implant crevicular fluid (PICF) was sampled from 25 healthy subjects (H), 25 subjects with mucositis (M) and 25 subjects with peri-implantitis (P) using paper points and suction tips. The samples were analysed by quantitative polymerase chain reaction (qPCR). The following biomarkers associated with the plasminogen system, inflammation and bone resorption/ remodelling were investigated: interleukin-1 beta (IL-1ß), interleukin 8 (IL-8), tissue plasminogen activator (tPA), plasminogen activator inhibitor 2 (PAI-2), tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CatK). RESULTS: IL-1ß and IL-8 were significantly upregulated in the P group, and tPA and PAI-2 were significantly upregulated in the M group. These four genetic markers were oppositely regulated in samples from the subjects in the mucositis compared with the peri-implantitis group. TRAP and CatK showed no differences between the groups. The presence of suppuration did not have a detectable effect on gene analysis in samples from subjects with peri-implantitis. CONCLUSIONS: Markers for the plasminogen system and inflammation could be used to distinguish between mucositis and peri-implantitis. The results suggested that the plasminogen system was sufficiently upregulated allowing for resolution of inflammation and healing at the inflamed implant site in subjects with mucositis, whereas such upregulation was insufficient resulting in impaired healing and prolonged inflammation in subjects with peri-implantitis. The combination of tissue inflammation and low levels of tPA was a strong predictor of marginal bone loss in this study. It may be an interesting candidate for the unambiguous diagnosis of mucositis and peri-implantitis independent of radiographs and could possibly constitute a powerful future tool for rapid assessment of the periimplant tissue condition and the effect of subject treatment.

Adherence of human oral keratinocytes and gingival fibroblasts to nano-structured titanium surfaces.

BACKGROUND: A key element for long-term success of dental implants is integration of the implant surface with the surrounding host tissues. Modification of titanium implant surfaces can enhance osteoblast activity but their effects on soft-tissue cells are unclear. Adherence of human keratinocytes and gingival fibroblasts to control commercially pure titanium (CpTi) and two surfaces prepared by anodic oxidation was therefore investigated. Since implant abutments are exposed to a bacteria-rich environment in vivo, the effect of oral bacteria on keratinocyte adhesion was also evaluated. METHODS: The surfaces were characterized using scanning electron microscopy (SEM). The number of adhered cells and binding strength, as well as vitality of fibroblasts and keratinocytes were evaluated using confocal scanning laser microscopy after staining with Live/Dead Baclight. To evaluate the effect of bacteria on adherence and vitality, keratinocytes were co-cultured with a four-species streptococcal consortium. RESULTS: SEM analysis showed the two anodically oxidized surfaces to be nano-structured with differing degrees of pore-density. Over 24 hours, both fibroblasts and keratinocytes adhered well to the nano-structured surfaces, although to a somewhat lesser degree than to CpTi (range 42-89% of the levels on CpTi). The strength of keratinocyte adhesion was greater than that of the fibroblasts but no differences in adhesion strength could be observed between the two nano-structured surfaces and the CpTi. The consortium of commensal streptococci markedly reduced keratinocyte adherence on all the surfaces as well as compromising membrane integrity of the adhered cells. CONCLUSION: Both the vitality and level of adherence of soft-tissue cells to the nano-structured surfaces was similar to that on CpTi. Co-culture with streptococci reduced the number of keratinocytes on all the surfaces to approximately the same level and caused cell damage, suggesting that commensal bacteria could affect adherence of soft-tissue cells to abutment surfaces in vivo.

Crystalline anatase-rich titanium can reduce adherence of oral streptococci.

Dental implant abutments that emerge through the mucosa are rapidly covered with a salivary protein pellicle to which bacteria bind, initiating biofilm formation. In this study, adherence of early colonizing streptococci, Streptococcus gordonii, Streptococcus oralis, Streptococcus mitis and Streptococcus sanguinis to two saliva-coated anodically oxidized surfaces was compared with that on commercially pure titanium (CpTi). Near edge X-ray absorption (NEXAFS) showed crystalline anatase was more pronounced on the anodically oxidized surfaces than on the CpTi. As revealed by fluorescence microscopy, a four-species mixture, as well as individual bacterial species, exhibited lower adherence after 2 h to the saliva-coated, anatase-rich surfaces than to CpTi. Since wettability did not differ between the saliva-coated surfaces, differences in the concentration and/or configuration of salivary proteins on the anatase-rich surfaces may explain the reduced bacterial binding effect. Anatase-rich surfaces could thus contribute to reduced overall biofilm formation on dental implant abutments through diminished adherence of early colonizers.

Evaluation of a novel calcium phosphate-coated titanium porous oxide implant surface: a study in rabbits.

PURPOSE: To evaluate osseointegration of a novel calcium phosphate (CaP)-coated titanium porous oxide implant surface. MATERIALS AND METHODS: Twenty adult male New Zealand White rabbits were used. Each animal received two titanium porous oxide-surfaced implants (benchmark control: TiUnite, Nobel Biocare) and two novel CaP-coated titanium porous oxide-surfaces implants; they were randomly allocated to contralateral tibia implant sites. The animals were sacrificed after 2 or 4 weeks, and tissues were evaluated histometrically. RESULTS: Healing was generally uneventful. A removal torque analysis showed significantly higher mean (± SE) peak values for the control implants than for the test implants at 2 weeks (31.4 ± 2.5 Ncm versus 20.4 ± 1.8 Ncm) and 4 weeks (48.4 ± 5.5 Ncm versus 30.3 ± 3.9 Ncm). Light microscopy showed no significant differences in local bone density around control and test implants at 2 and 4 weeks (range, 85% to 91% within the thread area and 91% to 95% immediately outside the threads). At 2 weeks, bone-implant contact for control and test implants averaged 81.8% ± 2.8% and 75.7% ± 4.6%, respectively, and at 4 weeks the bone-implant contact values were 79.4% ± 2.8% and 73.5% ± 4.2%, respectively; these differences were not significant. Backscatter scanning electron microscopy also showed no significant differences in local bone density at control and test implants at 2 and 4 weeks (range, 55% to 72% within the thread area and 75% to 81% immediately outside the threads). At 2 weeks, bone-implant contact for control and test implants averaged 66.4% ± 2.9% and 61.5% ± 5.1%, respectively, and at 4 weeks mean values were 60.1% ± 4.2% and 53.3% ± 4.6% (differences not significant). CONCLUSIONS: The results suggest that the novel CaP-coated surface effectively supports osseointegration.

The correlation between gene expression of proinflammatory markers and bone formation during osseointegration with titanium implants.

An in vivo interfacial gene expression model combined with biomechanical analysis was used in order to determine the relationship between the molecular events taking place during osseointegration and the biomechanical stability of the implant. Anodically oxidized and machined, threaded titanium implants were characterized topographically, chemically and ultrastructurally. The implants were inserted in rat tibiae and the implant bone torsion stability was evaluated. After measurements, the implants were removed and analyzed with qPCR. Results showed an increase in the breakpoint torque of 140%, 170% and 190%, after 6, 14, and 28 days, respectively, at the oxidized implants as compared to the machined. Gene expression analysis revealed higher expression of runt related transcription factor-2 (Runx2) (after 28 d), osteocalcin (OC) and tartrate resistant acid phosphatase (TRAP) (after 6, 14 and 28 d) and cathepsin K (CATK) (after 6 and 14 d) at the oxidized implants. On the other hand, machined implants were associated with higher expression of tumor necrosis factor-α (TNF-α) (after 6 and 28 d) and interleukin-1ß (IL-1ß) (after 6, 14 and 28 d) compared to the oxidized implants. In conclusion, the favorable cellular and molecular events at the oxidized implants were in parallel with significantly stronger bone anchorage during osseointegration.

The influence of bone type on the gene expression in normal bone and at the bone-implant interface: experiments in animal model.

BACKGROUND: Studies on the biological processes in different bone types and the reaction of different bone types to biomaterials are often hindered because of the difficulties in sampling procedures and lack of sensitive techniques. PURPOSE: The purpose was to assess the suitability of quantitative polymerase chain reaction (qPCR) for investigation of the biological differences between cortical and trabecular bone types and their responses to biomaterials. MATERIALS AND METHODS: Gene expression of selected markers in rat bone samples from different locations was evaluated. Samples were harvested by trephines from the trabecular femoral epiphysis, cortico-trabecular proximal tibial metaphysic, and the cortical distal tibial metaphysis. Gene expression was also evaluated at the surfaces of anodically oxidized implants retrieved from cortical and trabecular sites after 3 days of implantation. mRNA in the bone samples and in the tissue associated with the implant surfaces was extracted and quantified using qPCR. Tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), alkaline phosphatase (ALP), osteocalcin (OC), tartrate-resistant acid phosphatase (TRAP), cathepsin K (CATK), and 18S ribosomal subunits (18S) were analyzed. RESULTS: In the bone samples, higher expression of ALP, OC, TRAP, and CATK was found in femoral epiphysis compared to proximal or distal tibial metaphysis, indicating a higher turnover in the trabecular bone. On the other hand, TNF-α and IL-1ß showed higher expression in both tibia sites compared with the femur site, which suggests higher inflammatory potential in the cortical bone. In response to the oxidized implants trabecular bone expressed a higher level of IL-1ß, whereas the implants in cortical bone were associated with higher expression of ALP and OC. CONCLUSION: There are biological differences between cortical and trabecular bone types, both in the normal steady-state condition and in response to biomaterials. Such differences can be characterized and discriminated quantitatively using a sensitive technique such as qPCR.

A controlled clinical exploratory study on genetic markers for peri-implantitis.

PURPOSE: The objective of this controlled exploratory cross-sectional study was to investigate and compare the presence of gene expression of bone resorption/remodelling in peri-implant crevicular fluid samples from healthy subjects and subjects showing obvious clinical and radiographic signs of peri-implantitis. MATERIALS AND METHODS: Peri-implant crevicular fluid (PICF) was sampled from seven healthy subjects and seven subjects with obvious clinical signs of peri-implantitis using paper points. The samples were analysed by quantitative polymerase chain reaction (qPCR). Biomarkers associated with bone degradation/remodelling, such as tartrate-resistant acid phosphatase (TRAP), dickkopf-related protein- 1 (DKK-1), osteoprotegerin (OPG), cathepsin K (CatK) and osteocalcin (OC), were of particular interest in the study. RESULTS: The measured levels of genetic markers were similar for the subjects in the healthy and the peri-implantitis group. Only one subject out of seven with strong and clear clinical signs of peri-implantitis exhibited a panel of genetic markers for ongoing bone degradation. This subject was also diagnosed with rheumatoid arthritis. CONCLUSION: The present data showed that patients with obvious clinical signs of peri-implantitis and a history of bone loss can exhibit similar gene expressions of bone loss/remodelling as clinically healthy implant patients. Absence of bone resorption markers demonstrated that it was not possible to establish ongoing bone degradation in six of seven subjects in the peri-implantitis group. The results suggest that bone resorption was not in progress at the time of PICF sampling, or that cells expressing such markers were not present in significant numbers at the site of PICF sampling.

Evaluation of implants coated with recombinant human bone morphogenetic protein-2 and vacuum-dried using the critical-size supraalveolar peri-implant defect model in dogs.

BACKGROUND: Endosseous implants coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) in a laboratory bench setting and air-dried induce relevant bone formation but also resident bone remodeling. Thus, the objective of this study is to evaluate the effect of implants fully or partially coated with rhBMP-2 and vacuum-dried using an industrial process on local bone formation and resident bone remodeling. METHODS: Twelve male adult Hound Labrador mongrel dogs were used. Critical-size, supraalveolar, peri-implant defects received titanium porous oxide surface implants coated in their most coronal aspect with rhBMP-2 (coronal-load, six animals), or by immersion of the entire implant in a rhBMP-2 solution (soak-load, six animals) for a total of 30 µg rhBMP-2 per implant. All implants were vacuum-dried. The animals were sacrificed at 8 weeks for histometric evaluation. RESULTS: Clinical healing was unremarkable. Bone formation was not significantly affected by the rhBMP-2 application protocol. New bone height and area averaged (± SE) 3.2 ± 0.5 versus 3.6 ± 0.3 mm, and 2.3 ± 0.5 versus 2.6 ± 0.8 mm(2) for coronal-load and soak-load implants, respectively (P >0.05). The corresponding bone density and bone-implant contact registrations averaged 46.7% ± 5.8% versus 31.6% ± 4.4%, and 28% ± 5.6% versus 36.9% ± 3.4% (P >0.05). In contrast, resident bone remodeling was significantly influenced by the rhBMP-2 application protocol. Peri-implant bone density averaged 72.2% ± 2.1% for coronal-load versus 60.6% ± 4.7% for soak-load implants (P <0.05); the corresponding bone-implant contact averaged 70.7% ± 6.1% versus 47.2% ± 6.0% (P <0.05). CONCLUSIONS: Local application of rhBMP-2 and vacuum-drying using industrial process seems to be a viable technology to manufacture implants that support local bone formation and osseointegration. Coronal-load implants obviate resident bone remodeling without compromising local bone formation.

Alveolar ridge augmentation using implants coated with recombinant human growth/differentiation factor-5: histologic observations.

OBJECTIVES: In vitro and in vivo preclinical studies suggest that growth/differentiation factor-5 (GDF-5) may induce local bone formation. The objective of this study was to evaluate the potential of recombinant human GDF-5 (rhGDF-5) coated onto an oral implant with a purpose-designed titanium porous oxide surface to stimulate local bone formation including osseointegration and vertical augmentation of the alveolar ridge. MATERIALS AND METHODS: Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in 12 young adult Hound Labrador mongrel dogs. Six animals received implants coated with 30 or 60 microg rhGDF-5, and six animals received implants coated with 120 microg rhGDF-5 or left uncoated (control). Treatments were alternated between jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at weeks 3, 4, 7, and 8 post-surgery when they were euthanized for histologic evaluation. RESULTS: The clinical examination showed no noteworthy differences between implants coated with rhGDF-5. The cover screw and implant body were visible/palpable through the alveolar mucosa for both rhGDF-5-coated and control implants. There was a small increase in induced bone height for implants coated with rhGDF-5 compared with the control, induced bone height averaging (+/-SD) 1.6+/-0.6 mm for implants coated with 120 microg rhGDF-5 versus 1.2+/-0.5, 1.2+/-0.6, and 0.6+/-0.2 mm for implants coated with 60 microg rhGDF-5, 30 microg rhGDF-5, or left uncoated, respectively (p<0.05). Bone formation was predominant at the lingual aspect of the implants. Narrow yellow and orange fluorescent markers throughout the newly formed bone indicate relatively slow new bone formation within 3-4 weeks. Implants coated with rhGDF-5 displayed limited peri-implant bone remodelling in the resident bone; the 120 microg dose exhibiting more advanced remodelling than the 60 and 30 microg doses. All treatment groups exhibited clinically relevant osseointegration. CONCLUSIONS: rhGDF-5-coated oral implants display a dose-dependent osteoinductive and/or osteoconductive effect, bone formation apparently benefiting from local factors. Application of rhGDF-5 appears to be safe as it is associated with limited, if any, adverse effects.

Alveolar ridge augmentation using implants coated with recombinant human bone morphogenetic protein-7 (rhBMP-7/rhOP-1): histological observations.

BACKGROUND: Pre-clinical studies have shown that recombinant human bone morphogenetic protein-2 (rhBMP-2) coated onto purpose-designed titanium porous-oxide surface implants induces clinically relevant bone formation and osseointegration. The objective of this study was to examine the potential of rhBMP-7, also known as recombinant human osteogenic protein-1 (rhOP-1), coated onto titanium porous-oxide surface implants to support vertical alveolar ridge augmentation and implant osseointegration. MATERIALS AND METHODS: Bilateral, critical-size, 5 mm, supraalveolar peri-implant defects were created in six young adult Hound Labrador mongrel dogs. The animals received implants coated with rhBMP-7 at 1.5 or 3.0 mg/ml randomized to contra-lateral jaw quadrants. The mucoperiosteal flaps were advanced, adapted, and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at 3, 4, 7, and 8 weeks post-surgery when they were euthanized for histological evaluation. RESULTS: Without striking differences between treatments, the implant sites exhibited a swelling that gradually regressed to become hard to palpation disguising the implant contours. The histological evaluation showed robust bone formation; the newly formed bone assuming characteristics of the contiguous resident bone, bone formation (height and area) averaging 4.1+/-1.0 versus 3.6+/-1.7 mm and 3.6+/-1.9 versus 3.1+/-1.8 mm(2); and bone density 56%versus 50% for implants coated with rhBMP-7 at 1.5 and 3.0 mg/ml, respectively. Both treatments exhibited clinically relevant osseointegration, the corresponding bone-implant contact values averaging 51% and 47%. Notable peri-implant resident bone remodelling was observed for implants coated with rhBMP-7 at 3.0 mg/ml. CONCLUSIONS: rhBMP-7 coated onto titanium porous-oxide surface implants induces clinically relevant local bone formation including osseointegration and vertical augmentation of the alveolar ridge, the higher concentration/dose associated with some local side effects.

Evaluation of implants coated with rhBMP-2 using two different coating strategies: a critical-size supraalveolar peri-implant defect study in dogs.

BACKGROUND: Implants coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) induce relevant bone formation but also resident bone remodelling. OBJECTIVES: To compare the effect of implants fully or partially coated with rhBMP-2 on new bone formation and resident bone remodelling. MATERIALS AND METHODS: Twelve, male, adult, Hound Labrador mongrel dogs were used. Critical-size, supraalveolar, peri-implant defects received titanium porous oxide surface implants coated in their most coronal aspect with rhBMP-2 (coronal-load/six animals) or by immersion of the entire implant in an rhBMP-2 solution (soak-load/six animals) for a total of 30 mug rhBMP-2/implant. All implants were air-dried. The animals were euthanized at 8 weeks for histometric evaluation. RESULTS: Clinical healing was uneventful. Supraalveolar bone formation was not significantly affected by the rhBMP-2 application protocol. New bone height and area averaged (+/- SE) 3.4 +/- 0.2 versus 3.5 +/- 0.4 mm and 2.6 +/- 0.4 versus 2.5 +/- 0.7 mm(2) for coronal-load and soak-load implants, respectively (p>0.05). The corresponding bone density and bone-implant contact (BIC) recordings averaged 38.0 +/- 3.8%versus 34.4 +/- 5.6% and 25.0 +/- 3.8%versus 31.2 +/- 3.3% (p>0.05). In contrast, resident bone remodelling was significantly influenced by the rhBMP-2 application protocol. Bone density outside the implants threads averaged 74.7 +/- 3.8% and 50.8 +/- 4.1% for coronal-load and soak-load implants, respectively (p<0.05); bone density within the thread area averaged 51.8 +/- 1.2% and 37.8 +/- 2.9%, and BIC 70.1 +/- 6.7% and 43.3 +/- 3.9% (p<0.05). CONCLUSION: Local application of rhBMP-2 appears to be a viable technology to support local bone formation and osseointegration. Coronal-load implants obviate resident bone remodelling without compromising new bone formation.

Integrin and chemokine receptor gene expression in implant-adherent cells during early osseointegration.

The mechanisms of early cellular recruitment and interaction to titanium implants are not well understood. The aim of this study was to investigate the expression of pro-inflammatory cytokines, chemokines and adhesion markers during the first 24 h of implantation. Anodically oxidized and machined titanium implants were inserted in rat tibia. After 3, 12, and 24 h the implants were unscrewed and analyzed with quantitative polymerase chain reaction. Immunohistochemistry and scanning electron microscopy revealed different cell types, morphology and adhesion at the two implant surfaces. A greater amount of cells, as indicated by higher expression of small subunit ribosomal RNA (18S), was detected on the oxidized surface. Higher expression of CXC chemokine receptor-4 (at 12 h) and integrins, alphav (at 12 h), beta1 (at 24 h) and beta2 (at 12 and 24 h) was detected at the oxidized surfaces. Significantly higher tumor necrosis factor-alpha (at 3 h) and interleukin-1beta (at 24 h) expression was demonstrated for the machined surface. It is concluded that material surface properties rapidly modulate the expression of receptors important for the recruitment and adhesion of cells which are crucial for the inflammatory and regenerative processes at implant surfaces in vivo.

In vivo gene expression in response to anodically oxidized versus machined titanium implants.

A quantitative polymerase chain reaction technique (qPCR) in combination with scanning electron microscopy was applied for the evaluation of early gene expression response and cellular reactions close to titanium implants. Anodically oxidized and machined titanium miniscrews were inserted in rat tibiae. After 1, 3, and 6 days the implants were unscrewed and the surrounding bone was retrieved using trephines. Both the implants and bone were analyzed with qPCR. A greater amount of cells, as indicated with higher expression of 18S, was detected on the oxidized surface after 1 and 6 days. Significantly higher osteocalcin (at day 6), alkaline phosphatase (at days 3 and 6), and cathepsin K (at day 3) expression was demonstrated for the oxidized surface. Higher expression of tumor necrosis factor-alpha (at day 1) and interleukin-1beta (at days 1 and 6) was detected on the machined surfaces. SEM revealed a higher amount of mesenchymal-like cells on the oxidized surface. The results show that the rapid recruitment of mesenchymal cells, the rapid triggering of gene expression crucial for bone remodeling and the transient nature of inflammation, constitute biological mechanisms for osseointegration, and high implant stability associated with anodically oxidized implants.

Bone formation at recombinant human bone morphogenetic protein-2-coated titanium implants in the posterior mandible (Type II bone) in dogs.

BACKGROUND: Conventional oral/maxillofacial implants reach osseointegration over several months during which the titanium fixtures interact with alveolar bone. The objective of this study was to determine if adsorbing recombinant human bone morphogenetic protein-2 (rhBMP-2) onto a titanium porous oxide (TPO) implant surface might enhance or accelerate local bone formation and support osseointegration in a large animal oral/maxillofacial orthotopic model. MATERIAL AND METHODS: Endosseous implants with a TPO surface were installed into the edentulated posterior mandible in eight adult Hound Labrador mongrel dogs. The implant surface had been adsorbed with rhBMP-2 at 0.2 or 4.0 mg/ml. TPO implants without rhBMP-2 served as control. Treatments were randomized between jaw quadrants. Mucosal flaps were advanced and sutured leaving the implants submerged. Clinical and radiographic evaluations were made immediately post-surgery, at day 10 (suture removal), and week 4 and 8 post-surgery. The animals received fluorescent bone markers at week 3, 4, and at week 8 post-surgery, when they were euthanized for histologic analysis. RESULTS: TPO implants coated with rhBMP-2 exhibited dose-dependent bone remodelling including immediate resorption and formation of implant adjacent bone, and early establishment of clinically relevant osseointegration. The resulting bone-implant contact, although clinically respectable, appeared significantly lower for rhBMP-2-coated implants compared with the control [rhBMP-2 (0.2 mg/ml) 43.3+/-10.8%versus 71.7+/-7.8%, p<0.02; rhBMP-2 (4.0 mg/ml) 35.4+/-10.6%versus 68.2+/-11.0%, p<0.03]. CONCLUSIONS: rhBMP-2 adsorbed onto TPO implant surfaces initiates dose-dependent peri-implant bone re-modelling resulting in the formation of normal, physiologic bone and clinically relevant osseointegration within 8 weeks.

Bone formation at recombinant human bone morphogenetic protein-2-coated titanium implants in the posterior maxilla (Type IV bone) in non-human primates.

BACKGROUND: Studies using ectopic rodent and orthotopic canine models (Type II bone) have shown that titanium porous oxide (TPO) surface implants adsorbed with recombinant human bone morphogenetic protein-2 (rhBMP-2) induce local bone formation including osseointegration. The objective of this study was to evaluate local bone formation and osseointegration at such implants placed into Type IV bone. MATERIAL AND METHODS: rhBMP-2-coated implants were installed into the edentulated posterior maxilla in eight young adult Cynomolgus monkeys: four animals each received three TPO implants adsorbed with rhBMP-2 (2.0 mg/ml) and four animals each received three TPO implants adsorbed with rhBMP-2 (0.2 mg/ml). Contra-lateral jaw quadrants received three TPO implants without rhBMP-2 (control). Treatments were alternated between left and right jaw quadrants. Mucosal flaps were advanced and sutured to submerge the implants. The animals received fluorescent bone markers at weeks 2, 3, 4, and at week 16 when they were euthanized for histologic analysis. RESULTS: Clinical healing was uneventful. Extensive local bone formation was observed in animals receiving implants adsorbed with rhBMP-2 (2.0 mg/ml). The newly formed bone exhibited a specific pinpoint bone-implant contact pattern regardless of rhBMP-2 concentration resulting in significant osseointegration; rhBMP-2 (2.0 mg/ml): 43% and rhBMP-2 (0.2 mg/ml): 37%. Control implants exhibited a thin layer of bone covering a relatively larger portion of the implant threads. Thus, TPO control implants bone exhibited significantly greater bone-implant contact ( approximately 75%; p<0.05). There were no statistically significant differences between rhBMP-2-coated and control implants relative to any other parameter including peri-implant and intra-thread bone density. CONCLUSION: rhBMP-2-coated TPO implants enhanced/accelerated local bone formation in Type IV bone in a dose-dependent fashion in non-human primates resulting in significant osseointegration. rhBMP-2-induced de novo bone formation did not reach the level of osseointegration observed in native resident bone within the 16-week interval.

Alveolar ridge augmentation using implants coated with recombinant human bone morphogenetic protein-2: histologic observations.

BACKGROUND: Studies using ectopic rodent, orthotopic canine, and non-human primate models show that bone morphogenetic proteins (BMPs) coated onto titanium surfaces induce local bone formation. The objective of this study was to examine the ability of recombinant human BMP-2 (rhBMP-2) coated onto a titanium porous oxide implant surface to stimulate local bone formation including osseointegration and vertical augmentation of the alveolar ridge. MATERIAL AND METHODS: Bilateral, critical-size, 5 mm, supra-alveolar, peri-implant defects were created in 12 young adult Hound Labrador mongrel dogs. Six animals received implants coated with rhBMP-2 at 0.75 or 1.5 mg/ml, and six animals received implants coated with rhBMP-2 at 3.0 mg/ml or uncoated control. Treatments were randomized between jaw quadrants. The mucoperiosteal flaps were advanced, adapted and sutured to submerge the implants for primary intention healing. The animals received fluorescent bone markers at weeks 3, 4, 7 and 8 post-surgery when they were euthanized for histologic evaluation. RESULTS: Jaw quadrants receiving implants coated with rhBMP-2 exhibited gradually regressing swelling that became hard to palpate disguising the contours of the implants. The histologic evaluation showed robust bone formation reaching or exceeding the implant platform. The newly formed bone exhibited characteristics of the adjoining resident Type II bone including cortex formation for sites receiving implants coated with rhBMP-2 at 0.75 or 1.5 mg/ml. Sites receiving implants coated with rhBMP-2 at 3.0 mg/ml exhibited more immature trabecular bone formation, seroma formation and peri-implant bone remodelling resulting in undesirable implant displacement. Control implants exhibited minimal, if any, bone formation. Thus, implants coated with rhBMP-2 at 0.75, 1.5 and 3.0 mg/ml exhibited significant bone formation (height and area) compared with the sham-surgery control averaging (+/-SD) 4.4+/-0.4, 4.2+/-0.7 and 4.2+/-1.2 versus 0.8+/-0.3 mm; and 5.0+/-2.2, 5.6+/-2.2 and 7.4+/-3.5 versus 0.7+/-0.3 mm(2), respectively (p<0.01). All the treatment groups exhibited clinically relevant osseointegration. CONCLUSIONS: rhBMP-2 coated onto titanium porous oxide implant surfaces induced clinically relevant local bone formation including vertical augmentation of the alveolar ridge and osseointegration. Higher concentrations/doses were associated with untoward effects.

Hyperaemic blood-flow velocities in systole and diastole relate to coronary risk in divergent ways.

BACKGROUND: A recent study suggested blood-flow velocity in diastole during reactive hyperaemia as a major driver of flow-mediated vasodilation (FMD) of the brachial artery, also being related to cardiovascular risk factors. The present study aimed to investigate the relative importance of hyperaemic systolic and diastolic blood-flow velocity in the forearm regarding both FMD and cardiovascular risk factors. METHODS: In the Prospective Investigation of the Vasculature in Uppsala Seniors study, conducted in 1016 subjects aged 70 years, FMD, systolic and diastolic blood hyperaemic flow velocities in the brachial artery were evaluated by ultrasound. RESULTS: Hyperaemic blood-flow velocity both in systole and diastole were related to FMD (r = 0.14-0.19, P<0.0001). However, while hyperaemic systolic blood-flow velocity was related to coronary risk (Framingham risk score) in a positive way (r = 0.08, P = 0.013), diastolic blood-flow velocity was inversely related to coronary risk (r = -0.08, P = 0.016). Therefore, the systolic to diastolic hyperaemic blood-flow velocity ratio was more powerful related to coronary risk (r = 0.23, P = 0.0001). In a multiple regression model, both FMD and the systolic to diastolic hyperaemic blood-flow velocity ratio were independent predictors of coronary risk (P = 0.018 and P = 0.0001). CONCLUSION: As hyperaemic blood-flow velocities in systole and diastole in the brachial artery were related to coronary risk in divergent ways, the ratio thereof is a promising index of vascular function providing independent information regarding coronary risk when compared with FMD.

Histological and biomechanical evaluation of phosphorylcholine-coated titanium implants.

OBJECTIVE: Compounds considered for drug delivery from oral implant surfaces in support of local bone formation might themselves influence osseointegration. Phosphorylcholine (PC) polymers have been shown to enhance the biocompatibility of medical devices and to serve as drug delivery systems. The objective of this study was to evaluate local bone formation and osseointegration at PC and positively charged PC (PC+)-coated endosseous implants in an established rabbit model. MATERIAL AND METHODS: Sixteen adult female New Zealand White rabbits were used. Eight animals received PC-coated and control titanium porous oxide surface implants placed in the left and right distal femural condyle (trabecular bone) and proximal tibial metaphysis (cortical bone) using aseptic routines. The remaining eight animals similarly received PC+ and control implants. One implant was placed in each femural condyle and two implants in each tibial metaphysis. Experimental and control implants were alternated between the left and right hind legs. Fascia and skin were closed in layers. The animals were euthanized following a 6-week healing interval for biomechanical (removal torque) and histometric analyses. RESULTS: Peri-implant bone density was considerably greater at tibial compared with femoral sites within as well as immediately outside the implant threads. However, there were no significant differences in bone density among PC, PC+, and control implants. Nevertheless, bone-implant contact was significantly lower at PC compared with PC+ and control implants in cortical bone (p<0.05). Numerical differences in trabecular bone did not reach statistical significance. The removal torque evaluation revealed significantly lower values for PC compared with PC+ and control sites (p<0.05). CONCLUSION: The histometric and biomechanical analyses suggest that PC coating may influence biological processes and ultimately osseointegration of endosseous implants. Apparently, incorporation of cationic charges may reverse or compensate for this scenario. Nevertheless, both PC coatings exhibited clinically acceptable osseointegration. In perspective, PC technology appears to be a viable candidate delivery system for agents in support of local bone formation at endosseous implant surfaces.

Bone healing dynamics at buccal peri-implant sites.

BACKGROUND: It is common belief that immediate implant placement into extraction sites may act to preserve the alveolar process. The objective of this study was to evaluate healing dynamics at buccal peri-implant sites in relation to the dimensions of the alveolar ridge. METHODS: Bilateral, critical-size, supraalveolar, peri-implant defects were created in 12 male Hound Labrador mongrel dogs following surgical horizontal cut-down of the alveolar ridge. Each jaw quadrant received three 10-mm titanium implants placed 5 mm into extraction sites of the third and fourth premolar teeth leaving 5 mm in a supraalveolar position. The mucoperiosteal flaps were advanced, adapted, and sutured for primary intention healing. Bone fluorescent markers were administered at weeks 3 and 4 postsurgery, and pre-euthanasia. Incandescent, polarized, and fluorescent light microscopies were used to assess the width of the buccal wall of the alveolar ridge and local bone remodeling over the 8-week healing interval. RESULTS: There was a significant association between the width of the buccal alveolar ridge and extent of bone resorption evaluated by incandescent and fluorescent light microscopy. A non-linear association was observed between the buccal ridge width and resorption of the alveolar ridge. A 2-mm threshold was established to account for this non-linearity. The strength of this association was two times greater in specimens with a buccal ridge width <2 mm compared with a wider ridge (beta=1.62 vs. 0.80) observed by fluorescent light microscopy. Accordingly, mean buccal resorption was significantly greater when the ridge width was <2 mm. Fluorescent light microscopy consistently showed greater buccal resorption compared with incandescent light microscopy (P<0.05). Agreement between the examination techniques was low (concordance correlation coefficient=0.49), especially for higher values of buccal resorption. CONCLUSION: When implants are placed into extraction sites, proximity to the buccal alveolar crest appears a major consideration. The observations herein suggest that the width of the buccal alveolar ridge should be at least 2 mm to maintain the alveolar bone level. These observations likely have general implications for implant placement using most surgical protocols.