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PubMed1995

Bonding capacity in bone of HIP-processed HA-coated titanium: mechanical and histological investigations.

The main problems using plasma-sprayed hydroxyapatite (HA) as a coating material on metallic implants are its porosity, low fatigue strength, and weak adherence to the metallic substrate. To overcome these problems a new technique using hot isostatic pressing (HIP) has been developed for producing HA-coated titanium (Ti) implants. Specimens produced at a maximum temperature of 850 degrees C and a maximum pressure of 720 bar displayed a dense, glassy, 25-microns thick coating with small amounts of porosity and a mean surface roughness of 0.7 microns, as compared with 1.6 microns for sandblasted Ti. Twenty conical HA-coated (720 and 100 bar pressure) and 10 noncoated Ti implants were inserted through the cortex of the lower margin of the mandibles of sheep and allowed to heal for 60 days. Push-out tests for implants processed at 720 bar pressure showed substantially higher bone/implant bonding values than for sandblasted Ti implants. Histological studies indicated a direct contact and probably chemical bonding between bone tissue and the HA coatings. The area of contact was almost 3 times as large as for the Ti implants. The adherence of the 100-bar coating to the Ti surface was inferior to the 720-bar coating, as shown by the loosening of the coatings in several areas.

Animals↗

PubMed2000

Bone changes around hydroxyapatite and titanium implants after abutment placement in rabbits-observations using histological and three-dimensional examinations.

We have previously developed a computer-aided system for examination of the three-dimensional bone structure around implants and observed the bone changes in the healing period after implant placement. This paper describes the bone changes around hydroxyapatite (HA) and titanium (Ti) implants after abutment placement using histological and three-dimensional examinations. Twenty-four HA and Ti implants were embedded in the tibias of adult male New Zealand white rabbits. After 8 weeks, the abutment had passed through periosteum and was placed under the skin. Rabbits were sacrificed 4 and 8 weeks following abutment placement. In conclusion, histological examination showed that, at 4 weeks after abutment placement, bone resorption around the implant neck was seen in both HA and Ti implants, and at 8 weeks, excessive bone formation was seen around the implant neck. Three-dimensional bone examination showed that abutment placement may affect bone formation and cause additional bone hypertrophy in the bone marrow area.

Animals↗

PubMed2000

Ultrastructural and immunoelectron microscopic studies of the peri-implant epithelium-implant (Ti-6Al-4V) interface of rat maxilla.

BACKGROUND: The role played by the internal basal lamina (IBL) and hemidesmosomes between an implant and the peri-implant epithelium (PIE) in the adherence of the epithelium to the implant is controversial. This study used rat maxilla implantation models to clarify the ultrastructure of the PIE-implant interface. METHODS: Ti-6Al-4V implants were inserted either immediately or 2 weeks after the extraction of the upper left first molar of 6- or 4-week-old rats, respectively. The junctional epithelium (JE) of the upper right molars in the same animals was used as a control. Four weeks after implantation, the animals were sacrificed to prepare specimens for light and immunoelectron microscopy. RESULTS: Under light microscopy, the PIE appeared to attach to the implant surface. Ultrastructurally, IBL, consisting of the lamina densa and lamina lucida, and hemidesmosomes were formed only in the lower region, and rarely in the middle region, of the PIE-implant interface. In control teeth, the IBL and hemidesmosomes formed throughout the dento-JE interface. Laminin-1 was found in the IBL and also in the vesicles and vacuoles of the PIE and JE cells. Statistical analysis showed that there was also a significant difference in the amount of IBL between the PIE-implant and dento-JE interfaces. CONCLUSIONS: PIE attached to the implant via hemidesmosomes and IBL in the lower region of the PIE-implant interface. Although PIE cells may secrete laminin-1, which contributes to epidermal cell adhesion, the PIE which attaches to implants only in the lower region of the interface is considered to be the poorly adhered epithelium.

Alloys↗

PubMed2003

Galvanic corrosion behavior of implant suprastructure dental alloys.

OBJECTIVE: The purpose of this study was to evaluate and compare in vitro, the galvanic corrosion behavior of Co-Cr alloys (R2000, R800), Ni-Cr (RCS), silver-palladium (Jelstar), Gold (Pontallor-4) and Ternary Ti (experimental Ter Ti) when coupled with endosseous Ti implant abutment material. Amalgam alloy and commercially pure Ti cylinders (SSTi) were coupled with endosseous Ti implants as negative and positive controls, respectively. METHODS: An EG&G Model 263 Scanning Potentiostat was used for this purpose. Specimens were prepared and fresh artificial saliva was used as an electrolyte solution. The experiment run time was 24h for each couple. The common potential, galvanic current and current integration during the last 6h were recorded for each couple. RESULTS: The results showed that the best couples were Ti/Pontallor-4, Ti/Ter Ti, Ti/R800 and Ti/Jelstar. The least acceptable couples were Ti/amalgam, SSTi/SSTi and Ti/R2000, while the Ti/RCS couple showed unstable galvanic corrosion behavior. SIGNIFICANCE: It is concluded that the following alloys can be used as suprastructure alloys with Ti implants: Pontallor-4, R800, Jelstar and Ter Ti. Although Ter Ti alloy is an experimental alloy, it showed good results, but cannot be used in the clinical field unless extensive investigations are carried out. The SSTi/SSTi couple showed unexpected galvanic corrosion behavior which needs further investigation.

Corrosion↗

PubMed1998

Uncontrolled diabetes hinders bone formation around titanium implants in rat tibiae. A light and fluorescence microscopy, and image processing study.

This study examined the influence of diabetes mellitus on bone formation around cylindrical titanium (Ti) implants (1.0 mm in diameter and 1.5 mm in length) inserted transcortically and extending into the medullary canal of rat tibiae using light and fluorescence microscopies and image processing. Forty-eight male Wistar King A rats (age 5 weeks) were used in this experiment. Streptozotocin was injected intraperitoneally to induce diabetes and the serum glucose concentration was checked to ensure the induction of diabetes prior to implant placement and at the time of sacrifice. The animals were sacrificed 7, 28, 56, or 84 days after placement. Toluidine blue-stained undecalcified sections were prepared for histological observation and image analysis. The Ti implants in the control group became increasingly encapsulated with a bone layer. The implants in the diabetes-induced (DI) group were also surrounded with a thin bone layer. Abundant adipocytes were observed in the DI group as compared with the control group. Quantitative evaluation indicated that the control group showed a significantly higher percent of bone contact, and thickness of surrounding bone and area than the DI group. Consequently, the present study suggests that uncontrolled diabetes would hinder bone formation around Ti implants in rats.

Adipocytes↗

PubMed2003

The role of titanium in the altered endotoxin-induced nitric oxide synthase expression in alveolar macrophages from titanium-alloy-implanted rats.

We have found that the concentration of titanium (Ti) in the blood of patients with loosened Ti-alloy prostheses is elevated. An increase in the levels of elemental Ti in the blood and lung tissues of rats with an alloyed-Ti implant also has been found. The cellular reaction to elevated elemental Ti in the circulation remains unclear. We further performed experiments to examine the changes of inducible nitric oxide synthase (iNOS) expression in alveolar macrophages from alloyed-Ti-implanted rats. The elevation of nitrite and iNOS expression induced by lipopolysaccharide (LPS) was suppressed. The in vitro effect of a soluble form of Ti was further investigated. Ti (0.01-0.06 mM) inhibited the LPS-induced nitrite production and iNOS expression in alveolar macrophages from normal rats without any cytotoxic effects. LPS induced protein tyrosine phosphorylation, tyrosine-phosphorylation of lyn (a CD14-receptor-associated-tyrosine kinase), and degradation of IkappaB-alpha protein (inhibitor of NF-kappaB) in alveolar macrophages. These events were inhibited by co-incubation with Ti. These results indicate that elemental Ti may impair iNOS expression in alveolar macrophages through the alteration of protein tyrosine phosphorylation and NF-kappaB activation. The inhibitory action of Ti on cellular responses of alveolar macrophages may be anti-inflammatory and thus may depress local defense mechanisms related to microbial killing.

Alloys↗

PubMed1992

In-vivo comparisons of clot formation on titanium and hydroxyapatite-coated titanium.

We investigated in vivo clot formation on the surface of hydroxyapatite (HA)-coated titanium (Ti) implants and on non-coated Ti implants. Immediately after tooth extraction implant samples were inserted into the blood clot, in the same extraction site, for 1, 30, 60, or 120 seconds. Samples were processed for scanning electron microscopy (SEM). Qualitative observations of clotting topography were made by direct SEM viewing. Neither of the implant surfaces appeared to differ markedly in the degree of clotting during the 120 seconds of implantation; they revealed very early clot formation and limited clot attachment. These results were compared to the findings obtained in a previous study using identical methods with an intact periodontal ligament (PDL), root planed roots, and roots planed and treated with pH 1 citric acid. The PDL surface had the most rapid clot formation at all time periods. By 120 seconds, all root surfaces had completed clot formation.

Alloys↗

PubMed2004

Effect of the difference of bone turnover on peri-titanium implant osteogenesis in ovariectomized rats.

High and low bone turnover situations, both of which are typically observed as postmenopausal and senile osteoporosis, were created by ovariectomy (OVX), and then an investigation of whether or not the difference of bone turnover affected peri-titanium (Ti) implant osteogenesis in rats was conducted. Female rats were divided into four groups. The experimental and control groups underwent OVX or sham operations at 15 or 27 weeks of age, as high or low bone turnover groups, respectively. Ti implants were inserted into the tibiae at 30 weeks, then fluorochromes were injected 10 or 20 days after the implantation for histometry. The implants were retained for 30 days and then ground sections were prepared. Afterward, the cortical bone growth rate, bone contact ratio (BCR) of the implant in both the cortical bone area and medullary canal area, and the average trabecular bone thickness around the implant were evaluated. Biochemical markers of bone turnover were also measured. Biochemical measurements indicated both increasing osteocalcin production in OVX rats and decreasing tartrate-resistant acid phosphatase activity in the low-turnover group. Histometrical measurements showed decreasing cortical growth and low BCR in the medullary canal of the low-turnover group. The high-turnover group demonstrated BCR as high as that of the control group. There was no significant difference in the average trabecular bone thickness around the implant among the groups. As a result, two types of osteoporotic situations were confirmed and it was shown that the difference of bone turnover was clearly due to the diverse osteogenesis around the Ti implant.

Acid Phosphatase↗

PubMed2004

Evaluation of titanium plasma-sprayed and plasma-sprayed hydroxyapatite implants in vivo.

In this study, bone interfacial strength and bone contact length at the plasma-sprayed hydroxyapatite (HA) and titanium plasma-sprayed (TPS) implants were evaluated in vivo. Non-coated titanium (Ti) implants were used as controls. Cylindrical coated or non-coated implants (4.0mm diameter by 8mm long) were implanted in the dogs' mandibles. Loading of the implants was performed at 12 weeks after implantation. At 12 weeks after implantation (prior to loading) and 1 year after loading, implants were evaluated for interfacial bone-implant strength and bone-implant contact length. No significant differences in interfacial bone-implant strength for all groups at 12 weeks after implantation and after 1 year loading in normal bone were found. However, bone contact length for HA implants was significantly higher than the TPS and Ti implants for both periods tested (12 weeks after implantation and 1 year after loading). It was concluded that TPS implants exhibited similar pull-out strength compared to the HA implants. In addition, the lower bone contact length on the TPS surface compared to HA surfaces did not affect the interfacial bone-implant strength for both implants.

Aerosols↗

PubMed2006

Wear and corrosion in retrieved thoracolumbar posterior internal fixation.

STUDY DESIGN: Posterior thoracolumbar spine implants retrieved as part of routine clinical practice over a 2-year period were analyzed to identify wear and corrosion. OBJECTIVE: Engineering analyses of retrieved posterior instrumentation for indications of performance and failure and correlation of this information with clinical factors. SUMMARY OF BACKGROUND DATA: Recent studies have reported spinal instrumentation particulate wear debris and have noted the importance of design considerations at implant connector interfaces. METHODS: A total of 57 implants were analyzed from patients (39 female, 18 male) whose average age at implantation was 43.9 years (range, 13.7-77.4 years). Time of implantation ranged from 2 months to 13.5 years. The top 3 implantation diagnoses were radiculopathy (33%), scoliosis (30%), and back pain (25%). Metallurgical analyses were performed to characterize the wear and/or corrosion, and fractures of the implants. RESULTS: Wear was present in 75%, corrosion in 39%, and fractures in 7% of the retrieved implants. Wear and/or corrosion was more prevalent, with respect to the total number of implants retrieved, in implants that had been in service at least 1 year. There was no evidence of corrosion in any of the Ti implants, whereas corrosion was present (with wear) in 58% of the stainless steel (SS) implants. Wear and corrosion were more frequently observed in long rods than in short rods. Implantation times were longer for SS implants than for Ti implants. CONCLUSIONS: Retrieved rods exhibited corrosion, wear, and fracture, with wear and corrosion mainly located at the interfaces with hooks, screws, or cross-connectors. The mechanisms causing this material loss in situ, as well as what local or systemic responses it may stimulate are of clinical significance and should be studied further.

Adolescent↗

PubMed1997

Bonding of chemically treated titanium implants to bone.

A study was undertaken in rabbit tibiae to determine the effects of chemical treatments and/or surface-induced bonelike apatite on the bone-bonding ability of titanium (Ti) implants. Smooth-surfaced plates (10 x 10 x 2 mm) of pure Ti, alkalil- and heat-treated Ti, and bonelike apatite-formed Ti after the treatments were implanted into the tibial metaphyses of mature rabbits. The tibiae containing the implants were harvested at 4, 8, and 16 weeks after implantation and subjected to a tensile testing and histologic evaluation. Biomechanical results showed that both treated implants exhibited significantly higher failure loads compared with untreated Ti implants at all time periods. Histologic examination by Giemsa surface staining, contact microradiography (CMR), and scanning electron microscopy (SEM) in backscatter mode revealed that both treated Ti implants directly bonded to bone tissue during the early postimplantation period, whereas untreated Ti implants formed direct contact with the bone only at 16 weeks. SEM-electron-probe microanalysis (EPMA) examination showed a Ca-P-rich layer at the interface between the treated implants and bone, although the Ca-P-rich layer was not detected on the surface of untreated implants during observation periods. The results of this study suggest that chemical treatments may accelerate the bone-bonding behavior of titanium implants and enhance the strength of bone-implant bonding by inducing a bioactive surface layer on Ti implants.

Animals↗

PubMed1993

The surface analysis of implant materials. 1. The surface composition of a titanium dental implant material.

The surfaces of titanium (Ti) plates, as models for Ti implants, have been characterized by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (TOF SIMS). Plates were prepared with rough and smooth surface topographies--the rough being similar to that of an implant. The XPS data has been used to construct a model of the plates' surface chemical structure, from the gas-solid interface through to pure Ti metal. At the surface of as-received plates, which underwent the same preparative procedure as an implant, considerable surface contamination was detected. In particular, high levels of carbon (C) contaminants were detected; the nature of this C was elucidated by fitting the C 1s core line and from the secondary ion mass spectra. The oxygen (O) 1s core line could not be fitted using a minimum of 2 gaussian peaks, demonstrating the multiplicity of O environments. The detection of other elements in the XPS analysis further demonstrated that, in nominally pure Ti plates, the surface chemical composition deviates considerably from that of the bulk. The data obtained from the plates were confirmed by examination of a Ti abutment. The handling of Ti plates with stainless steel tweezers was investigated. No obvious change in surface chemistry was detected. All the above results bring into serious questions the validity of rigorous protocols demanded, in some techniques, in the handling and use of Ti implants.

Dental Implants↗

PubMed1997

Apatite layer-coated titanium for use as bone bonding implants.

For development of thin bioactive coatings on metal implants, a dense and uniform apatite layer was coated onto titanium (Ti) implants in situ by using a new biomimetic method, which is composed of apatite nucleation and growth steps in simulated body fluid (SBF). Analysis of the coatings by thin film X-ray diffraction and scanning electron microscopy-energy dispersive X-ray microanalysis (SEM-EMPA) before implantation showed that its characteristics were very similar to those of natural bone. The coated and uncoated rectangular plates were bilaterally implanted into the tibial proximal metaphyses of rabbits. After 6, 10 and 25 weeks post-implantation, the bone bonding and bone formation at the bone-implant interfaces were evaluated by a detachment test and undecalcified histological examination. Mechanical testing in tension showed that the failure load of apatite layer-coated Ti implants was significantly higher than that of uncoated control at each time period (all P < 0.001). Histologically, it was shown that bone was deposited directly onto the apatite coating without any intervening soft tissue, while in the paired controls, interpositional soft tissue was seen at the bone-implant interface. By SEM-EPMA, a uniform calcium- and phosphorus-rich layer was detected between the coated implants and bone, but not in uncoated controls at either earlier or later time periods. The results indicate that the apatite layer deposited on Ti in situ may significantly increase the bone bonding strength by providing a bioactive surface, which allows for an early bone apposition to the implant. In addition, the apatite layer-coated Ti produced by the biomimetic process may fulfil the requirements of favourable thin coatings and strong adhesion at the metal-coating interface.

Analysis of Variance↗

PubMed2003

Interfacial kinetics of titanium- and cobalt-based implant alloys in human serum: metal release and biofilm formation.

The biocompatibility of metallic implant surfaces is governed in large part by the interfacial kinetics associated with metal release and protein binding. The kinetics of metal release from, and protein binding to, cobalt- and titanium-based implant alloys in human serum were investigated by (1). measuring the temporal release of Cr and Ti into serum from Co-Cr-Mo (ASTM F-75) and Ti implant alloys (Ti-6Al-4V: ASTM F136, and commercially pure Ti, cpTi: ASTM F67), respectively; (2). examining the composition of human serum proteins adsorbed onto the surfaces of Co- and Ti-based implant alloys; and (3). identifying the serum proteins associated with the binding of soluble Cr and Ti degradation products. Analysis of metal dissolution kinetics found that Cr was released from Co-based implant alloy at an order of magnitude higher than Ti was released from Ti-based implant alloys. Serum became saturated with soluble CR and Ti at levels as high as 3250 ng/mL Ti from cpTi; 3750 ng/mL Ti from Ti-6Al-4V; and 35400 ng/mL Cr from Co-Cr-Mo degradation. The observation that human serum binds more released metal from Co-based alloy dissolution was consistent with the observed differences in biofilm composition between the two alloys, where additional serum protein(s) of approximately approximately 140 (kDa) molecular weight were detected on Co-based implant alloy surfaces. However, both Cr and Ti released from Co- and Ti-based alloys exhibited a bimodal binding pattern to both low molecular weight serum protein(s) (<32 kDa), and to higher molecular weight protein(s) in the 180-250 kDa range. Identification of metal alloy-dependent biofilm compositions and dissolution products provides the basis for understanding the bioavailability and bioreactivity of these implant alloys and their degradation products.

Alloys↗

PubMedDate not supplied

Prevention of bacterial leakage into and from prefabricated screw-retained crowns on implants in vitro.

Previous in vitro studies have shown that a mean gap of less than 4 microns between prefabricated crowns and implants of the Ha-Ti implant system is not a barrier to infiltration by Staphylococcus aureus. These studies confirmed earlier in vivo work showing that a multitude of oral microorganisms could colonize and infiltrate these gaps. In the present investigation, 30 Ha-Ti implant-crown assemblies were tested for bacterial leakage after the gaps were sealed with the chlorhexidine-containing varnish Cervitec. S. aureus leakage into the totally submerged test specimens was detected in 1 of 5 samples incubated for 4 weeks, while no leakage was detected in specimens incubated for 3, 5, 6, 7, and 8 weeks. When the sealed test specimens were partially submerged (that is, excluding the screw hole of the crown) and incubated for 3 to 11 weeks, none of the internal surfaces of the 30 test specimens manifested contamination. The clinical relevance of gap sealing in maintaining inflammation-free marginal mucosa and in achieving clinically successful treatment of peri-implantitis has yet to be determined.

Anti-Infective Agents, Local↗

PubMed1997

Hydroxyapatite-coating on titanium arc sprayed titanium implants.

We developed a new titanium spray technique using an inert gas shielded arc spray (titanium arc spray). Hydroxyapatite (HA)-coating can be applied to the implant without any surface pore obstruction after the rough surface is made by this technique. Scanning electron microscopy (SEM) of various porous implant surfaces after HA-coating revealed that the bead and fiber metal-coated implants had either a pore obstruction or an uneven HA-coating. On the other hand, the titanium arc sprayed implant demonstrated an even HA-coating all the way to the bottom of the surface pore. In the first set of animal experiments (Exp. 1), the interfacial shear strength to bone of four kinds of cylindrical Ti-6A1-4V (Ti) implants were compared using a canine transcortical push-out model 4 and 12 weeks after implantation. The implant surfaces were roughened by titanium arc spray (group A-C) and sand blasting (group D) to four different degrees (roughness average, Ra = group A: 56.1, B: 44.9, C: 28.3, D: 3.7 microns). The interfacial shear strength increased in a surface roughness-dependent manner at both time periods. However, the roughest implants (group A) showed some failed regions in the sprayed layers after pushout test. In the second set of animal experiments (Exp. 2), four kinds of Ti implants; HA-coated smooth Ti (sHA) with Ra of 3.4 microns, bead-coated Ti (Beads), titanium arc sprayed Ti (Ti-spray) with Ra of 38.1 microns and HA-coated Ti-spray (HA + Ti-spray) with Ra of 28.3 microns were compared using the same model as that in Exp. 1. The interfacial shear strength of HA + Ti-spray was significantly greater than that of sHA and Beads at both time periods, and that of Ti-spray at 4 weeks. Although a histological examination revealed that HA-coating enhanced bone ingrowth, sHA showed the lowest shear strength at both time periods. SEM after pushout test showed that sHA consistently demonstrated some regional failure at the HA-implant substrate interface. HA + Ti-spray had many failed regions either at the HA-bone interface or within the bone tissue rather than at the HA-implant substrate interface. These results suggested that the HA-coated smooth surfaced implants had a mechanical weakness at the HA-substrate interface. Therefore, HA should be coated on the rough surfaced implants to avoid a detachment of the HA-coating layer from the substrate and thus obtain a mechanical anchoring strength to bone. HA-coating on this new type of surface morphology may thus lead to a solution to the problems of conventional HA-coated and porous-coated implants.

Alloys↗

PubMed2005

No adverse effects of bone compaction on implant fixation after resorption of compacted bone in dogs.

BACKGROUND: A new bone preparation technique, compaction, has been shown to enhance initial implant fixation. However, short-term compaction has resulted in more non-vital bone being in contact with the implant. Also, compaction may result in inferior long-term implant fixation as the compacted non-vital bone at the bone-implant interface is resorbed. METHODS: We tested the hypothesis that compaction would result in inferior implant fixation after 10 weeks of weight bearing. We compared compaction with the conventional bone removal technique (drilling) for (1) porous coated titanium (Ti) implants inserted exact-fit into medial femoral condyles, and for (2) hydroxy-apatite (HA) porous coated implants inserted press-fit into lateral femoral condyles. In each of 8 dogs, we prepared the implant cavities of one knee joint with drilling, and the other with compaction. Implants were tested mechanically to failure by push-out test, and histomorphometry was done. RESULTS: For all specimens, non-vital bone implant contact contributed very little to the total bone implant contact. Inferior mechanical or histological implant fixation with compaction was not found for either Ti implants or HA implants. INTERPRETATION: Compaction does not appear to result in inferior implant fixation as the compacted bone at the bone implant interface is resorbed.

Animals↗

PubMed1997

Surface-dimpled commercially pure titanium implant and bone ingrowth.

The purpose of this investigation was to examine the effect of the surface macrostructure of a dimpled commercially pure titanium (cp Ti) implant on bone ingrowth in vivo by means of histological examination and a push-out test. Cylindrical implants were inserted in one femur of each experimental rabbit and the animals were killed at 1.5, 3 and 13 months after implantation. The femur with the implant of each animal was then examined in a push-out test. The fracture surfaces of the bone-implant interface after the push-out test were examined under light and electron microscopy. It seems that the dimpled cp Ti surface results in the increased retention of the cp Ti implant in bone due to interlocking between vital bone and the dimples.

Animals↗