Control Implants Research Articles

Local, Controlled Release In Vivo of Vascular Endothelial Growth Factor Within a Subcutaneous Scaffolded Islet Implant Reduces Early Islet Necrosis and Improves Performance of the Graft

Islet transplantation remains the only alternative to daily insulin therapy for control of type 1 diabetes (T1D) in humans. To avoid the drawbacks of intrahepatic islet transplantation, we are developing a scaffolded islet implant to transplant islets into nonhepatic sites. The implant test bed, sized for mice, consists of a limited (2-mm) thickness, large-pore polymeric sponge scaffold perforated with peripheral cavities that contain islets suspended in a collagen hydrogel. A central cavity in the scaffold holds a 2-mm diameter alginate sphere for controlled release of the angiogenic cytokine vascular endothelial growth factor (VEGF). Host microvessels readily penetrate the scaffold and collagen gel to vascularize the islets. Here, we evaluate the performance of the implant in a subcutaneous (SC) graft site. Implants incorporating 500 syngeneic islets reversed streptozotocin-induced diabetes in mice approximately 30 d after SC placement. Controlled release of a modest quantity (20 ng) of VEGF within the implant significantly reduced the time to normoglycemia compared to control implants lacking VEGF. Investigation of underlying causes for this effect revealed that inclusion of 20 ng of VEGF in the implants significantly reduced central necrosis of islets 24 h after grafting and increased implant vascularization (measured 12 d after grafting). Collectively, our results demonstrate (1) that the scaffolded islet implant design can reverse diabetes in SC sites in the absence of prevascularization of the graft site and (2) that relatively low quantities of VEGF, delivered by controlled release within the implant, can be a useful approach to limit islet stress after grafting.

Immediate and delayed loading of fixed dental prostheses supported by single or two splinted implants: A histomorphometric study in dogs.

To evaluate presumptive differences in osseointegration at implants supporting crowns that are physiologically loaded either immediately or 3months after installation. All premolars and first molars were extracted bilaterally in six dogs. After 3months of healing, three implants were installed on the premolar region and two in the molar region in one side of the mandible. Likewise, after another 3months, five implants were installed in the contralateral side, and impressions were taken bilaterally. Within 48hours, two single crowns were screwed bilaterally onto two implants in the premolar region, and two splinted crowns reproducing the shape of the first molar were screwed bilaterally onto the implants in the molar region. The mesial implants were used as no-loaded controls. Sacrifices were performed after 3months, and histological analyses were performed. At the premolar sites, mineralised bone-to-implant contact (MBIC%) was 78.0±4.0% and 70.9±7.9% at the delayed and immediately loaded sites, respectively. This difference was statistically significant. At the control implants, MBIC% was 61.4±14.7% and 63.1±13.1% at the delayed and the immediately loaded sites, respectively. At the molar sites, MBIC% was 79.2±10.9% and 61.1±10.3% at the delayed and immediately loaded sites, respectively. Applying a delayed loading to fixed dental prostheses supported by single or two splinted implants yielded higher proportions of bone-to-implant contact (osseointegration) compared to immediately loaded implants. Moreover, both types of loading protocols yielded a higher rate of osseointegration compared to unloaded implant sites after 3months following implant installation.

Antimicrobial Peptides for Topical Treatment of Osteomyelitis and Implant-Related Infections: Study in the Spongy Bone.

We examined the benefits of short linear α-helical antimicrobial peptides (AMPs) invented in our laboratory for treating bone infection and preventing microbial biofilm formation on model implants due to causative microorganisms of osteomyelitis. For this purpose, we introduced a model of induced osteomyelitis that utilizes human femur heads obtained from the hospital after their replacement with artificial prostheses. We found that the focus of the infection set up in the spongy part of this bone treated with AMP-loaded calcium phosphate cement was eradicated much more effectively than was the focus treated with antibiotics such as vancomycin or gentamicin loaded into the same cement. This contradicts the minimum inhibitory concentrations (MIC) values of AMPs and antibiotics against some bacterial strains obtained in standard in vitro assays. The formation of microbial biofilm on implants made from poly(methylmethacrylate)-based bone cement loaded with AMP was evaluated after the implants’ removal from the infected bone sample. AMPs loaded in such model implants prevented microbial adhesion and subsequent formation of bacterial biofilm on their surface. Biofilms did form, on the other hand, on control implants made from the plain cement when these were implanted into the same infected bone sample. These results of the experiments performed in human bone tissue highlight the clinical potential of antimicrobial peptides for use in treating and preventing osteomyelitis caused by resistant pathogens.

Controllable defects implantation in MoS2 grown by chemical vapor deposition for photoluminescence enhancement

Photoluminescence (PL) of transition metal dichalcogenides (TMDs) can be engineered by controlling the density of defects, which provide active sites for electron-hole recombination, either radiatively or non-radiatively. However, the implantation of defects by external stimulation, such as uniaxial tension and irradiation, tends to introduce local damages or structural non-homogeneity, which greatly degrades their luminescence properties and impede their applicability in constructing optoelectronic devices. In this paper, we present a strategy to introduce a controllable level of defects into the MoS2 monolayers by adding a hydrogen flow during the chemical vapor deposition, without sacrificing their luminescence characteristics. The density of the defect is controlled directly by the concentration of hydrogen. For an appropriate hydrogen flux, the monolayer MoS2 sheets have three times stronger PL emission at the excitonic transitions, compared with those samples with nearly perfect crystalline structure. The defect-bounded exciton transitions at lower energies arising in the defective samples and are maximized when the total PL is the strongest. However, the B exciton, exhibits a monotonic decline as the defect density increases. The Raman spectra of the defective MoS2 reveal a redshift (blueshift) of the in-plane (out-of-plane) vibration modes as the hydrogen flux increases. All the evidence indicates that the generated defects are in the form of sulfur vacancies. This study renders the high-throughput synthesis of defective MoS2 possible for catalysis or light emitting applications.

Evaluation of primary stability in modified implants: Analysis by resonance frequency and insertion torque.

Changes in the macrogeometry of dental implants are known to influence primary stability and the osseointegration process. The purpose of the present in vitro study was to evaluate the mechanical behavior of geometric changes in the apex region of dental implants. Thirty-five cylindrical dental implants (Titamax Ti; Neodent) were machined at the apical third to reproduce the experimental groups: without apical cut (Wc), apical bi-split cut, apical tri-split cut, apical quadri-split cut (Qs). One (control group) (Titamax Ti Ex) (n = 7) without any modifications was added. The implants had the same final dimensions (4.1 x 11 mm2 ). All implants were inserted into artificial bone blocks and were evaluated by insertion torque and resonance frequency by ISQ values (Osstell). Two-tailed analysis of variance (One-way ANOVA) and Tukey's post-test (P < .05). Control and Qs implants showed a significant increase of the insertion torque (P < .001). For the resonance frequency, Wc and (control) implants had the greatest ISQ values. However, there's no significant difference between (control) and Qs for the ISQ values (P < .001). Within the limitations of the present study, the proposed geometries at the apical third of dental implants greatly influenced its insertion torque and primary stability in vitro.

Co-registration of cone beam CT and preoperative MRI for improved accuracy of electrode localization following cochlear implantation

Objectives: To investigate the clinical usefulness and practicality of co-registration of Cone Beam CT (CBCT) with preoperative Magnetic Resonance Imaging (MRI) for intracochlear localization of electrodes after cochlear implantation.Methods: Images of 20 adult patients who underwent CBCT after implantation were co-registered with preoperative MRI scans. Time taken for co-registration was recorded. The images were analysed by clinicians of varying levels of expertise to determine electrode position and ease of interpretation.Results: After a short learning curve, the average co-registration time was 10.78 minutes (StdDev 2.37). All clinicians found the co-registered images easier to interpret than CBCT alone. The mean concordance of CBCT vs. co-registered image analysis between consultant otologists was 60% (17-100%) and 86% (60-100%), respectively. The sensitivity and specificity for CBCT to identify Scala Vestibuli insertion or translocation was 100 and 75%, respectively. The negative predictive value was 100%.Discussion: CBCT should be performed following adult cochlear implantation for audit and quality control of surgical technique. If SV insertion or translocation is suspected, co-registration with preoperative MRI should be performed to enable easier analysis. There will be a learning curve for this process in terms of both the co-registration and the interpretation of images by clinicians.

Influence of the Presence of Alveolar Mucosa at Implants: A Histological Study in Humans.

To evaluate the influence of the presence or absence of keratinized mucosa on hard and soft tissues around implants. Sixteen volunteers with edentulous regions in the distal aspect of the mandible participated in the study. In each patient, 2 solid titanium screw-shaped devices, 3.5 mm in diameter and 5 mm long, were installed. The incision of the mucosa was performed in such a way to allow that, after the suture of the flaps, only the alveolar mucosa surround the test sites and the keratinized mucosa surround the control implants. After 3 months of healing, biopsies were retrieved and ground sections were prepared for histological analysis. Eighteen biopsies from 9 patients were collected for analysis. Both buccal bone resorption and most coronal level of osseointegration were higher at the test sites compared with the control sites, the difference between the 2 sites being 0.2 and 0.5 mm, respectively. The difference in the coronal level of osseointegration between the test and control sites was statistically significant. Mineralized bone-to-implant contact was 70.6% ± 10.9% at the test sites and 71.5% ± 9.2% at the control sites. The presence of alveolar mucosa at implants resulted in a more apical position of the coronal level of osseointegration in respect of the implant margin compared with the presence of keratinized mucosa.

Does Oral Implant Design Affect Marginal Bone Loss? Results of a Parallel-Group Randomized Controlled Equivalence Trial.

Objective To test whether or not the modified design of the test implant (intended to increase primary stability) has an equivalent effect on MBL compared to the control. MethodsForty patients were randomly assigned to receive test or control implants to be installed in identically dimensioned bony beds. Implants were radiographically monitored at installation, at prosthetic delivery, and after one year. Treatments were considered equivalent if the 90% confidence interval (CI) for the mean difference (MD) in MBL was in between −0.25 and 0.25 mm. Additionally, several soft tissue parameters and patient-reported outcome measures (PROMs) were evaluated. Linear mixed models were fitted for each patient to assess time effects on response variables. Results Thirty-three patients (21 males, 12 females; 58.2 ± 15.2 years old) with 81 implants (47 test, 34 control) were available for analysis after a mean observation period of 13.9 ± 4.5 months (3 dropouts, 3 missed appointments, and 1 missing file). The adjusted MD in MBL after one year was −0.13 mm (90% CI: −0.46–0.19; test group: −0.49; control group: −0.36; p = 0.507). Conclusion Both implant systems can be considered successful after one year of observation. Concerning MBL in the presented setup, equivalence of the treatments cannot be concluded. Registration This trial is registered with the German Clinical Trials Register (ID: DRKS00007877).

Wool-derived keratin hydrogel enhances implant osseointegration in cancellous bone.

This study investigated whether a keratin hydrogel derived from wool enhances ossointegration of dental implants, using a cancellous bone model in sheep. Ten female sheep received one dental implant per hind leg in the distal femoral condyles. Test implants were coated with 1 mL of keratin hydrogel containing sulphonated keratin and hydroxyapatite; control implants remained uncoated; implants were not functionally loaded axially. Biomechanical stability was tested with resonance frequency analysis (RFA) at placement and euthanasia. Animals were sacrificed after 4 weeks and resin-embedded histomorphometry performed. Bone appeared denser and more mature around the keratin-treated test implants. Average % bone-implant contact was significantly increased for the test (58.1 ± 4.6 [SD]%) compared to control implants (34.4 ± 7.5%) (p = 0.01). RFA values were lower for control (76.5 ± 4.2 ISQ) than test implants (80.4 ± 1.4) after 4 weeks (p = 0.04). the increase in osseointegration found in this model suggests that keratin hydrogel has the potential to enhance the successful osseointegration of dental implants placed into poor quality bone. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2447-2454, 2018.

The Neuroinflammatory Response to Nanopatterning Parallel Grooves into the Surface Structure of Intracortical Microelectrodes

AbstractThe smooth surface structure of intracortical microelectrodes implanted within the nanometer‐scale architecture of brain tissue may contribute to the foreign body response. Here, the neuroinflammatory response to nanopatterning surface grooves etched directly on nonfunctional Michigan‐style microelectrodes is explored. Rats implanted with nanopatterned silicon microelectrodes are compared to smooth control implants to observe the effects the grooves have on neuroinflammation. Histology and real‐time PCR at 2 and 4 weeks postimplantation quantify glial cell reactivity and activation, inflammation, oxidative stress, and neuronal survival. Histological observations of glial cells and blood–brain barrier permeability do not show appreciable differences between the nanopatterned and control implants. However, silicon microelectrodes with nanopatterned grooves have more high mobility group box 1 (HMGB1) gene expression at 2 weeks and less nitric oxide synthase (NOS2) gene expression at 4 weeks compared to control surfaces. Control samples have increased NOS2, HMGB1, and tumor necrosis factor gene expression from 2 to 4 weeks, while nanopatterned implants have significant decrease in CD14 gene expression from 2 to 4 weeks. Collectively the results indicate that etching nanopatterned grooves do not reduce histological markers of neuroinflammation compared to control implants, but gene expression results encourage further investigation.

Influence of diabetes on the foreign body response to nitric oxide-releasing implants

The foreign body response (FBR) to nitric oxide (NO)-releasing subcutaneous implants was compared between healthy and streptozotocin-induced diabetic swine by evaluating inflammation, collagen capsule formation, and angiogenesis. Steel wire substrates were first modified with polyurethane membranes capable of diverse NO-release kinetics (NO fluxes and release durations of 0.8–630.0 pmol cm−2 s−1 and 2–13 d, respectively). The NO-releasing materials were implanted in the subcutis for 3, 10, or 25 d for histological and immunohistochemical evaluation of the FBR. A delayed, more severe inflammatory response to control (i.e., non-NO-releasing) implants was observed in diabetic pigs relative to healthy swine. Regardless of the animal disease state, each NO-releasing implant tested elicited reduced inflammation compared to controls at both 3 and 10 d. However, only the NO-release materials capable of releasing low NO fluxes (0.8–3.3 pmol cm−2 s−1) for 7–13 d durations mitigated the inflammatory response at 25 d. Using immunohistochemical staining for the endothelial cell surface marker CD-31, we also observed poor blood vessel development at non-NO-releasing implants in diabetic swine. Relative to controls, NO-releasing implants with the longest NO-release duration (13 d) increased blood vessel densities by 47.1 and 70.4% in the healthy and diabetic pigs, respectively. In the healthy model, tissues surrounding the long NO-release materials contained sparse amounts of collagen, whereas implants with shorter NO-release durations (2, 3, and 7 d) were characterized with a dense collagen encapsulation layer, similar to controls. Collagen deposition in diabetic swine was inhibited, and unaffected by NO. These results emphasize several key differences in the FBR in the setting of acute onset diabetes. The observation that NO release counteracts the more severe FBR in diabetic swine while simultaneously promoting tissue integration may help guide the design of medical implants (e.g., glucose sensors) with improved performance for diabetes management.

Topical zoledronic acid decreases micromotion induced bone resorption in a sheep arthroplasty model

BackgroundInitial micromotion of a total hip replacement is associated with aseptic loosening. The use of bisphosphonates could be one way to reduce peri-implant bone resorption induced by micromotion. Bisphosphonates compounds are inhibitors of bone resorption. The aim of this study was to investigate whether local treatment with bisphosphonate would reduce bone resorption and fibrous tissue around an experimental implant subjected to micromotion.MethodsOne micromotion implant were inserted into each medial femoral condyle in ten sheep. During each gait cycle the implant axially piston 0.5 mm. During surgery one of the femoral condyles were locally treated with 0.8 mg zoledronate. The other condyle served as control. Observation period was 12 weeks.ResultsHistological evaluation showed a fibrous capsule around both the control and bisphosphonate implants. Histomorphometrical analysis showed that 97% of the surface on both control and bisphosphonate implants were covered by fibrous tissue. However, the bisphosphonate was able to preserve bone in a 1 mm zone around the implants.ConclusionThis study indicates that local treatment with bisphosphonate cannot prevent the formation of a fibrous capsule around an implant subjected to micromotion, but bisphosphonate is able to reduce resorption of peri-prosthetic bone.

Impact of medialization laryngoplasty on dynamic nanomechanical vocal fold structure properties.

Although the primary goal of medialization laryngoplasty is to improve glottic closure, implant placement is also likely to alter the biomechanical properties of the vocal fold (VF). We sought to employ novel, nanoscale technology to quantify these properties following medialization based on the hypothesis that different medialization materials will likely yield differential biomechanical effects. Ex vivo. Nine pig larynges were divided into three groups: control, Silastic (Dow Corning, Midland, Michigan, U.S.A.) block medialization, or Gore-Tex (W.L. Gore & Associates, Newark, Delaware) medialization. Laryngoplasty was performed on excised, intact larynges. The larynges were then bisected in the sagittal plane and each subjected to dynamic nanomechanical analysis (nano-DMA) at nine locations using a 250-μm flat-tip punch and frequency sweep-load profile across the free edge of the VF and inferiorly along the conus elasticus. Silastic block and Gore-Tex implant introduced increased storage and loss moduli. Overall, storage moduli mean (maximum) increased from 38 kilopascals (kPa) (119) to 72 kPa (422) and 129 kPa (978) in control, Gore-Tex, and Silastic implants, respectively. Similarly, loss moduli increased from 13 kPa (43) to 22 kPa (201) and 31 kPa (165), respectively. Moduli values varied widely by location in the Silastic block and Gore-Tex groups. At the free VF edge, mean (maximum) storage moduli were lowest in the Gore-Tex group, 20 kPa (44); compared to control, 34.5 kPa (86); and Silastic, 157.9 kPa (978), with similar loss and complex moduli trends. Medialization laryngoplasty altered VF structure biomechanical properties; Silastic and Gore-Tex implants differentially impact these properties. NA. Laryngoscope, 128:1163-1169, 2018.

(Invited) New Approaches for Shrinking the Performance Gap for GaN Power Devices

The expected performance of GaN and SiC based power devices far exceeds that of Si power transistors, but the gap between the expected and achieved performance is much larger for these wide band gap materials. In these paper, we discuss new approaches for shrinking this performance gap for GaN power devices. They include using the quantum well channel designs that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of a high mobility in the device channel. The gate edge engineering (beyond just using field plates) that optimizes the voltage distribution in the drain-to-gate spacing could be combined with a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges. Additional contacts in the drain-to-gate spacing for the field control and variable doping implants should allow for further optimization. The perforated channel designs could alleviate both the parasitic series resistance problem and the heat dissipation problem. Extending the gate perforations into the drain-to-gate region allows for a considerable reduction of the switching RC constant with a commensurate decrease in power dissipation. The ultimate design should use the lateral-vertical structures. The AlInN/AlN/GaN technology is uniquely poised for the breakthrough in high temperature performance. We predict that the combination of these approaches will dramatically shrink the performance gap firmly establishing GaN as a superb material for power applications.

Clearing up the court: sex and the endocrine basis of display-court manipulation

Sexual selection can drive the evolution of novel traits, including behaviours, that may arise in sex-specific patterns and be under sex-steroid hormone control. In some polygynous species, males actively manipulate their display environment, likely to influence female perception of male sexual traits. As a presumptive appetitive reproductive behaviour, the motivation to manipulate the display environment may be activated by reproductive hormones and the degree of motivation may vary across individuals. To evaluate these possibilities, we examined the hormone dependence of court-clearing behaviour in lek-breeding golden-collared manakins, Manacus vitellinus, of Panama where males clean the rainforest floor of debris within display courts and maintain these cleaned courts during the long breeding season and during subsequent years. Nonbreeding females and juvenile males were given implants containing testosterone (T) or empty (control) implants and observed in a large aviary situated in the middle of Panamanian rainforest. The aviary was planted with saplings around which males display; the bare ground was covered with dried leaves. Control-treated males removed only a few leaves from their courts. T treatment dramatically stimulated court-cleaning behaviour, including both the removal of leaves and attempts to extract small seedlings from the soil. None of the females displayed court-cleaning behaviour, although T-treated females showed low levels of some male courtship displays as well as significant levels of aggressive behaviour. To assess wild adult males' motivation to clear courts, we presented lekking males with weighted artificial leaves. Males were attentive to the leaves and motivated to remove them. With increasing weight, males utilized different methods, which often involved multiple repeated attempts to move leaves. These findings demonstrate that manakins exhibit sex-specific and hormone-dependent court-cleaning behaviours and that males are highly motivated and physically adapted to keep their courts clean.

(Invited) New Approaches for Shrinking the Performance Gap for GaN Power Devices

The expected performance of GaN and SiC based power devices far exceeds that of Si power transistors, but the gap between the expected and achieved performance is much larger for GaN transistors. In this paper, we discuss new approaches for shrinking the performance gap for GaN power devices. They include using the quantum well channel designs that lead to the electron wave function penetration into wide band gap cladding layers with the commensurate increase in the breakdown voltage while keeping the advantage of a high mobility in the device channel. The gate edge engineering (beyond just using field plates) optimizes the voltage distribution in the drain-to-gate spacing. It could be combined with a low conducting passivation for smoothing or even eliminating the sharp maximum of the electric field in the vicinity of the gate and field plate edges. Additional contacts in the drain-to-gate spacing for the field control and variable doping implants should allow for further optimization. The perforated channel designs could alleviate both the parasitic series resistance problem and the heat dissipation problem. Extending the gate perforations into the drain-to-gate region allows for a considerable reduction of the switching RC constant with a commensurate decrease in power dissipation. The ultimate design could use the lateral-vertical structures. The AlInN/AlN/GaN technology is uniquely poised for the breakthrough in high temperature performance. We predict that the combination of these approaches will dramatically shrink the performance gap firmly establishing GaN as a superb material for power applications.

Maintenance Tools applied to Electric Generators to Improve Energy Efficiency and Power Quality of Thermoelectric Power Plants

This paper presents a specific method to improve the reliability of the equipment and the quality of power supplied to the electrical systems with the frequency and voltage control of a thermoelectric plant, to guarantee a more stable system. The method has the novelty of combining Total Productive Maintenance (TPM) using only four pillars, with Electrical Predictive Maintenance based in failure analysis and diagnostic. It prevents voltage drops caused by excessive reactive consumption, thus guaranteeing the company a perfect functioning of its equipment and providing a longer life of them. The Maintenance Management Program (MMP) seeks to prevent failures from causing the equipment to be shut down from the electrical system, which means large financial losses, either by reducing billing or by paying fines to the regulatory agency, in addition to prejudice the reliability of the system. Using management tools, but applying only four TPM pillars, it was possible to achieve innovation in power plants with internal combustion engines. This study aims to provide maintenance with a more reliable process, through the implantation of measurement, control and diagnostic devices, thus allowing the management to reduce breakdown of plant equipment. Some results have been achieved after the implementation, such as reduction of annual maintenance cost, reduction of corrective maintenance, increase of MTBF (Mean Time between Failures) and reduction of MTTR (Mean Time to Repair) in all areas. Probabilistic models able to describe real processes in a more realistic way, and facilitate the optimization at maximum reliability or minimum costs are presented. Such results are reflected in more reliable and continual power generation.

Enhanced bone formation in the vicinity of porous β-TCP scaffolds exhibiting slow release of collagen-derived tripeptides.

It has been experimentally proven that orally ingested collagen-derived tripeptides (Ctp) are quickly absorbed in the body and effectively promote the regeneration of connective tissues including bone and skin. Ctp are capable to activate osteoblasts and fibroblasts, which eventually promotes tissue regeneration. Based on these findings, a hypothesis was formulated in this study that direct delivery of Ctp to bone defect would also facilitate tissue regeneration as well as oral administration. To test the hypothesis, we prepared a bone augmentation material with the ability to slowly release Ctp, and investigated its in vivo bone regeneration efficacy. The implant material was porous β-tricalcium phosphate (β-TCP) scaffold which was coated with a co-precipitated layer of bone-like hydroxyapatite and Ctp. The β-TCP was impregnated with approximately 0.8%(w/w) Ctp. Then, the Ctp-modified β-TCP was implanted into bone defects of Wistar rats to evaluate in vivo efficacy of Ctp directly delivered from the material to the bone defects. The control was pristine porous β-TCP. In vitro tests showed that Ctp were steadily released from the co-precipitated layer for approximately two weeks. The Ctp-modified scaffolds significantly promoted new bone formation in vivo in their vicinity as compared with pristine β-TCP scaffolds; 6 weeks after the implantation, Ctp-modified scaffolds promoted twice as much bone formation as the control implants. Consequently, we achieved the slow and steady release of Ctp, and found that direct delivery of Ctp from implant materials was effective for bone regeneration as well as oral administration. A β-TCP scaffold capable of slowly releasing bone-enhancing substances significantly promoted bone formation.

Effect of implantoplasty on fracture resistance and surface roughness of standard diameter dental implants.

To assess the effect of implantoplasty on the fracture resistance, surface roughness, and macroscopic morphology of standard diameter (4.1mm) external connection dental implants. An in vitro study was conducted in 20 screw-shaped titanium dental implants with an external connection. In 10 implants, the threads and surface were removed and polished with high-speed burs (implantoplasty), while the remaining 10 implants were used as controls. The final implant dimensions were recorded. The newly polished surface quality was assessed by scanning electron microscopy (SEM) and by 3D surface roughness analysis using a confocal laser microscope. Finally, all the implants were subjected to a mechanical pressure resistance test. A descriptive analysis of the data was made. Also, Student's t tests were employed to detect differences regarding the compression tests. Implantoplasty was carried out for a mean time of 10min and 48s (standard deviation (SD) of 1min 22s). Macroscopically, the resulting surface had a smooth appearance, although small titanium shavings and silicon debris were present. The final surface roughness (Sa values 0.1±0.02μm) was significantly lower than that of the original (0.75±0.08μm Sa ) (p=.005). There was minimal reduction in the implant's inner body diameter (0.19±0.03mm), and no statistically significant differences were found between the test and control implants regarding the maximum resistance force (896 vs 880N, respectively). Implantoplasty, although technically demanding and time-consuming, does not seem to significantly alter fracture resistance of standard diameter external connection implants. A smooth surface with Sa values below 0.1μm can be obtained through the use of silicon polishers. A larger sample is required to confirm that implantoplasty does not significantly affect the maximum resistance force of standard diameter external connection implants.

Sinus floor elevation using implants coated with recombinant human bone morphogenetic protein-2: micro-computed tomographic and histomorphometric analyses.

The objective of this study was to determine the validity of a graft-free sinus floor elevation (SFE) procedure with simultaneous placement of recombinant morphogenetic protein-2 (rhBMP-2)-coated implants compared to uncoated control implants. In 10 rabbits, SFE was performed on both sides. Dental implants were randomly placed in the sinus filled with a blood clot. Test implants were coated with rhBMP-2, whereas in the control group, implants were uncoated. Micro-computed tomographic and histomophometric analyses were performed at 4 and 8weeks, including measurement for newly formed bone height (NBHm). Bone formation was evident along the implant surfaces up to the apex in test, but limited in control implants at 4weeks. NBHm amounted to 5.1mm (Q1=4.1; Q3=5.3) for test implants and to 3.4mm (2.6; 3.7) for control implants at 4weeks. NBHm then decreased to 8weeks (3.4mm (3.3; 3.7)) for test implants, whereas in control sites, NBHm increased slightly to 4.4mm (4.1; 4.5) (p=0.1250; p=0.6250). Implants coated with rhBMP-2 presented a strong osteogenic reaction at 4weeks with more favorable outcomes in terms of bone formation along the implant surface up to the apex compared to uncoated control implants. Remodeling and resorption process between 4 and 8weeks did not further improve the outcomes in the test, but in the control group. The use of rhBMP-2-coated implants in a graft-free SFE might show an advantage in early implant stability to prevent collapse of membrane. However, a potential clinical benefit still needs to be proven.