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PubMed2004

Hydroxyapatite and carbon coatings for fixation of unloaded titanium implants.

The aim of this study was to investigate the interaction between bone and pure titanium, titanium coated with hydroxyapatite (HA), and titanium coated with carbon in a rat femur model. In 25 rats, the medullary cavity of both femurs was entered by an awl from the trochanteric area. With steel burrs it was successively reamed to a diameter of 2.0 mm. Nails with a diameter of 2.0 mm and with a length of 34 mm were inserted in a random manner; either a pure titanium nail, a titanium nail entirely plasma-sprayed with a 75-100-microm layer of HA or a titanium nail coated with 2-10-microm carbon. The surface roughness of the pure titanium was characterized by Ra 2.6 microm and Rt 22 microm. Ra of HA was 7.5 microm and Rt 52 microm, and of carbon Ra was 0.4 microm and Rt 4.0 microm. Twelve rats were randomized to a follow up of 8 weeks, and the remaining 13 rats were followed for 16 weeks. At sacrifice both femora were dissected free from soft tissues and then immersed in fixative. A specimen slice of about 5 mm thickness was prepared from the subtrochanteric region with a water-cooled band-saw. Sample preparation for un-decalcified tissue followed the internal guidelines at the laboratories of Biomaterials/Handicap Research. At 8 weeks the median bone bonding contact of the implants was 43% (range 0-74) in the titanium group, 39% (0-75) in the HA group, and 3% (0-59) in the carbon group. At 16 weeks the corresponding figures were 58% (0-78) in the titanium group, 51% (15-75) in the HA group, and 8% (0-79) in the carbon group. In conclusion, we found great variability in bone bonding contact. In general, carbon-coated nails had reduced bone bonding contact both at 8 and at 16 weeks as compared to pure titanium or titanium coated with hydroxyapatite.

Analysis of Variance↗
PubMed1990

Comparative clinical study of porous hydroxyapatite and decalcified freeze-dried bone in human periodontal defects.

Interproximal bony defects were treated with either porous hydroxyapatite (PHA) or decalcified freeze-dried bone allograft (DFDB) implants at two different clinical centers. Twelve paired defects in 12 patients were treated at each center. Six months post-surgically the defects were measured to assess changes from the presurgical status. No statistically significant differences were found between the groups in changes in gingival fluid, bleeding index, plaque index, or tooth mobility. The porous hydroxyapatite implant produced greater reduction in pocket depth (P = 0.03) and more gain in clinical attachment level (P = 0.001) and defect fill (P = 0.001) when compared with DFDB grafted sites. This study indicates that more clinical resolution of interproximal periodontal defects in humans can be obtained with the use of PHA than with the use of DFDB.

Adult↗
PubMed1991

Clinical comparison of hydroxyapatite-coated titanium dental implants placed in fresh extraction sockets and healed sites.

The placement of hydroxyapatite-coated dental implants in fresh extraction sockets was compared to placement in adjacent healed sites in 14 patients. Systematic sequential documentation was obtained regarding periodontal health, radiographic bone levels, and implant stability at the time of implant placement, at uncovering, and from 8 to 24 months (mean 16 months) after loading and restoration delivery. There were no significant differences in any clinical parameter between those implants placed in fresh extraction sockets and those placed in healed areas. Periodontal health, maintenance of crestal bone levels, and implant stability were excellent for implants placed in both types of recipient sites. The results of this study suggest that hydroxyapatite-coated dental implants can be successfully placed in fresh extraction sockets utilizing otherwise standard implant placement techniques, and that they appear to clinically perform equally well in fresh sockets and healed sites.

Adult↗
PubMed1997

Histological comparison of early wound healing following dense hydroxyapatite granule grafting and barrier placement in surgically-created bone defects neighboring implants.

The purpose of this study was to examine early wound healing following grafting of dense hydroxyapatite granules (HA granules) and barrier placement in surgically-created bone defects surrounding implants. Eight healthy adult dogs with an average weight of 15 kg were used in this study. Thirty-two bone defects measuring 4 mm x 4 mm were removed with a surgical bur to form continuous bucco-lingual bone defects and 32 implants (16 titanium [Ti]) and 16 hydroxyapatite-coated [HA]) were then placed into the defects. Four implant groups were created: 1) grafting HA; 2) covering with an expanded polytetrafluoroethylene (ePTFE) membrane; 3) grafting HA and covering with ePTFE membrane; and 4) control (no treatment). Animals were sacrificed 28 days after surgery. Histological sections revealed large amounts of newly-formed bone in all bone defects surrounding the implants treated with ePTFE membranes alone. Fibrous encapsulation of HA granules was observed in the defects of the HA granules grafting group. In the group with grafting of HA granules and covering with ePTFE membranes, small amounts of bone tissue were observed among HA granules, but most HA granules were surrounded with fibrous tissue. Bone defects were completely filled with connective tissue in the control group. There were no differences in the histological findings between Ti and HA-coated implants in all cases. Histomorphometric data disclosed that the presence of HA granules in the bone defects significantly arrested bone formation. Our study suggests that the grafting of dense HA into bone defects surrounding implants will result in fibrous healing during the early healing stage.

Alveolar Bone Loss↗
PubMed2006

Effect of a hydroxyapatite tricalcium phosphate alloplast on osseous repair in the rat calvarium.

BACKGROUND: Bony defects caused by periodontitis are often treated by regenerative therapy using autografts and/or allografts. Alloplasts, such as hydroxyapatite or ceramics, are also used as osteoconductive materials that serve as a scaffold for new bony ingrowth. The purpose of this study was to determine the effect of hydroxyapatite tricalcium phosphate (HA-TCP) on osseous repair in the rat calvarium. METHODS: Forty-four adult male Harlan Sprague-Dawley rats were assigned to one of four treatment groups: HA-TCP macroporous disk, HA-TCP microporous disk, HA-TCP granules, and demineralized freeze-dried bone (DFDB). The materials were placed into 8-mm calvarial critical-size defects (CSD). Calvariae were harvested at 10 weeks post-surgery and evaluated histomorphometrically. RESULTS: The DFDB group had significantly (P <0.05) more new bone formation (47%) than any other group. The HA-TCP macroporous disk group had significantly (P <0.05) more new bone formation (19.7%) than the HA-TCP microporous disk (8.5%) or HA-TCP granule (6.9%) groups. CONCLUSIONS: The HA-TCP macroporous disk may elicit significant new bone formation due to its rigid space-maintaining scaffold and pore size for vascular ingrowth. It is well tolerated by host tissues and may be a suitable carrier for growth factors.

Animals↗
PubMed1989

[Dynamic study of titanium-hydroxyapatite implant by finite element method].

In order to evaluate the strength of titanium-hydroxyapatite implant, adhesive tests and loading tests were performed. The results of the loading tests were compared with the computed results by finite element method. Axisymmetric 8-node quadrilateral element for arbitrary loading was used for the analysis. Implants of 3.2 mm diameter were loaded at 45 degrees of the implant axis by using an Instron testing machine at crosshead speed of 0.5 mm/min. The results were obtained as follows: 1. The mean value of the adhesive test of titanium-resin (Panavia)-hydroxyapatite was 2.3 kgf/mm2. The fracture was caused at Panavia layer. 2. The mean value of the fracture loads of implants was 10.9 kgf. The fracture was caused at Panavia layer, similarly to the result described in 1. 3. The principal stress caused at Panavia layer of the implant was approximately 2.3 kgf/mm2, which was calculated under the load of 10.9 kgf by the finite element method. This result corresponds to that of the loading test described in 1 and 2. It was ascertained by these findings that finite element method is effective for the evaluation of the strength of this implant.

Dental Implants↗
PubMed1980

Interaction between sulphated macromolecules and hydroxyapatite studied by infrared spectroscopy.

Transmission infrared spectroscopy has been used to study some aspects of the mechanism of binding of chondroitin-4-sulphate to hydroxyapatite. The disappearance of absorption maxima characteristic of the covalently bound sulphate groups indicates that these groups may be involved in bridging the chondroitin sulphate molecule to the crystal lattice of the hydroxyapatite. The technique may be valuable, both in studying the formation of organic films on tooth surfaces and the mechanisms of endogenous mineralisation.

Adsorption↗
PubMed1994

Orbital reconstruction with hydroxyapatite ceramic implants.

Thirteen patients with fractures of the orbital floor (inferior wall), medial and lateral walls, or so-called "blowout" fractures with or without fractures of the zygoma were treated with artificially made hydroxyapatite ceramic implants made entirely from limestone, some of which were made with computer aided design and computer aided machinery (CAD-CAM) from data obtained from helical computed tomography. Orbital reconstruction with hydroxyapatite ceramic implants is a safe technique which is superior to previous ones in which autogenous or plastic materials were used.

Adult↗
PubMed1990

Hydroxyapatite coating enhances fixation of porous coated implants. A comparison in dogs between press fit and noninterference fit.

Intimate contact at the bone-porous surface interface is not always achievable in noncemented prosthetic implantation. We investigated the effect of hydroxyapatite (HA) coating on skeletal attachment in noninterference fit 4 weeks after implantation in 6 mature dogs. The push-out test of HA-coated implants surrounded by a 1-mm gap showed a twofold increased shear strength and fivefold increased shear stiffness compared with titanium alloy (Ti) coated implants. The fixation of Ti implants was reduced by two thirds when inserted in a gap as compared with press fit, whereas HA-coated implants in gap showed anchorage close to implants in press fit. Only minor differences were found between HA and Ti implants in press fit. Histomorphometric analysis showed a significant increase in bone in direct contact to HA-coated implant as compared with Ti implants inserted both in gap and press fit. The study indicates that tightness of surgical fit is an important factor for sufficient fixation of the implant. However, our results demonstrate that hydroxyapatite coating almost eliminates the negative influence of noninterference fit between bone and unloaded implant.

Animals↗
PubMed1996

Transforming growth factor-beta stimulates bone ongrowth. Hydroxyapatite-coated implants studied in dogs.

Unloaded cylindrical grit-blasted titanium (Ti-6A-4V) implants (6 x 10 mm) coated with hydroxyapatite ceramic were inserted into the proximal part of the humerus of 20 skeletally mature Labrador dogs. The implants were initially surrounded by a 2 mm gap. In 10 dogs, HA-coated implants without growth factor were inserted in one humerus and implants with 0.3 microgram rhTGF-beta 1 adsorbed onto the HA coating were inserted in the contralateral humerus. In another group of 10 dogs, a dose of 3.0 micrograms rhTGF-beta 1 was tested in a similar design. All dogs were killed at 6 weeks after treatment. Results were evaluated by histomorphometry and mechanical push-out testing. Bone ongrowth was increased by one third, using the 0.3 mg rhTGF-beta 1 stimulation. Bone volume in the gap and mechanical testing showed no statistically significant differences between control and rhTGF-beta 1 stimulated implants. RhTGF-beta 1 only moderately enhanced bone ongrowth to hydroxyapatite-coated implants.

Alloys↗
PubMed1999

Hydroxyapatite coated with insulin-like growth factor 1 (IGF1) stimulates human osteoblast activity in vitro.

We studied the effects of a hydroxyapatite-tricalcium phosphate material coated with Insulin-like Growth Factor 1 (IGF1) on cell growth, collagen synthesis and alkaline phosphatase activity (ALP) of human osteoblasts in vitro. Cell proliferation was stimulated when osteoblasts were incubated with untreated hydroxyapatite (HA) and it was further increased by exposure to IGF1-coated HA. 3H-Proline uptake was significantly increased by treatment with either HA or IGF1-coated HA but no significant differences were found between these two groups. ALP activity was enhanced by exposure to HA, with respect to the control, and further increased by treatment with IGF1-coated HA. Our findings suggest that HA is useful for promoting osteoblast activity and IGF1 may help to improve its biological characteristics.

Alkaline Phosphatase↗
PubMed1989

Experimental and clinical experience with hydroxyapatite-coated hip implants.

Published experimental studies have founded the principles of implant fixation using hydroxyapatite coatings. Clinical results are given on the first 100 consecutive cases of hydroxyapatite-coated total hip replacement performed since 1986. The Harris hip score rating at 1 year and longer is 98 and the specific radiologic characteristics are discussed.

Animals↗
PubMed2002

Platelet concentrate increases bone ingrowth into porous hydroxyapatite.

Platelets contain growth factors that are believed to stimulate early fracture repair. Autologous platelets can be sequestered, concentrated, and mixed with thrombin to yield a so-called autologous growth factor gel, which might enhance bone repair or bone graft incorporation. The effect of this platelet concentrate on total tissue and bone ingrowth into porous coralline hydroxyapatite was studied in a bone chamber rat model. Chambers with the platelet concentrate showed a significant increase in bone and total tissue ingrowth distance compared to untreated controls, indicating a platelet concentrate might enhance the clinical performance of porous hydroxyapatite in bone replacement.

Animals↗
PubMed1991

Laser-Raman Spectroscopic study of the adhesive interface between 4-MET/MMA-TBB resin and hydroxyapatite or bovine enamel.

The possible chemical interaction between synthetic hydroxyapatite or bovine enamel and a functional monomer of 4-methacryloxyethyl trimellitic acid (4-MET) diluted in methyl methacrylate (MMA) was examined by measuring the Raman spectra. It was concluded that the carboxyl group of 4-MET reacted with the calcium in the substrate to form a salt that was detected by the Raman band at around 1,380 cm-1. However, formation of the salt on the surface of the hydroxyapatite (HAP) with the carboxyl group, and polymerization of the 4-MET in the methacryl group near the surface were mutually exclusive reactions for the same 4-MET molecule.

Adhesives↗
PubMed1993

Chin augmentation with porous hydroxyapatite blocks.

The results of chin augmentation by porous hydroxyapatite blocks were evaluated clinically and radiographically in nine patients. Recovery of a satisfactory facial profile was achieved by the procedure, and all patients but one, with removal of the implant because of infection, were satisfied with the results of the surgery. Radiographically, the implants were incorporated into the bony structure of the mandible by deposition of bone at and around the bone-implant interface and ingrowth of bone into pores. Cephalometrically, the procedure was found to provide very stable results, with little change in the position of the implants and no appreciable resorption of the implants and bone. Despite heavy chemotherapy, histologic examination of the removed hydroxyapatite showed the presence of areas with numerous inflammatory cell infiltration and no bone formation. Thus, the procedure is quite useful for chin augmentation, but utmost care should be taken to avoid infection.

Adolescent↗
PubMed1997

[Ocular socket plasty with orbital implant of hydroxyapatite].

OBJECTIVE: To evaluate the clinical effect of a new surgical procedure to reconstruct socket with sclera-encapsulated hydroxyapatite after enucleation and evisceration. METHODS: Hydroxyapatite spheres were implanted primarily into auto-sclera capsule in 41 cases. Secondary implantation was performed with heterosclera-encapsulated ones in 9 cases. RESULTS: No inflammation, implant extrusion and implant dislocation occurred in 7-23 months (mean = 15.6 months) of follow-up. CONCLUSION: Satisfactory prothetic motility was obtained in all cases.

Adolescent↗
PubMed2000

Porous hydroxyapatite granules for alloplastic enhancement of the facial region.

Hydroxyapatite is a biocompatible alloplast with the same chemical composition as bone. It is readily incorporated into host bone, does not undergo appreciable resorption, does not incite a clinically significant foreign body reaction, and resists infection. This article describes forms of hydroxyapatite, procedures for use, and clinical examples.

Adolescent↗
PubMed2001

Coralline hydroxyapatite as bone substitute in orthopedic oncology.

We retrospectively reviewed the results of 71 consecutive patients managed with coralline hydroxyapatite (Pro-Osteon 500; Interpore Cross International) for bone defects produced as a result of surgical extirpation of bone tumors. All patients underwent a thorough physical examination and a radiographic evaluation at baseline and follow-up by the same senior surgeon (R.B.I.). Seventy-one patients were followed up for an average of 2.4 years (range, 8.1 months to 3.5 years); mean age of female patients was 39.8 years and that of male patients was 30 years. The functional status of patients at follow-up was evaluated based on comparison with preoperative functional status. Radiographic evaluation was performed and graded as follows: stage I (obvious margins), stage II (hazy margins), and stage III (obvious incorporation). The average time of return of preoperative function was 7.6 weeks. There were 3 major and 9 minor complications. We conclude that coralline hydroxyapatite graft in the form of Pro-Osteon 500 is a viable option for the management of bone defects in orthopedic oncology.

Adolescent↗