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PubMed1994

Hydroxyapatite orbital implant abscess: histopathologic correlation of an infected implant following evisceration.

A 60-year-old diabetic man with a history of ocular trauma and absolute glaucoma underwent evisceration with placement of an 18 mm hydroxyapatite orbital implant. The host scleral shell was left intact with no posterior opening for vascular ingrowth. One year later the patient presented with implant exposure, limited fibrovascular ingrowth into the implant, and a Staphylococcus aureus orbital abscess. The implant was removed, and pathology demonstrated suppurative inflammation with limited vascular ingrowth. This patient's risk factors for an implant-associated wound infection included diabetes, impaired wound healing, history of trauma, early implant exposure, and delayed fibrovascular ingrowth. Awareness of the infectious complications of any orbital implant including hydroxyapatite allows the surgeon to alter management strategies in an attempt to reduce such risk. Surgeons may consider posterior scleral portals with evisceration surgery to facilitate hydroxyapatite vascularization. Patient selection, implant size, and surgical technique are key factors for a management strategy designed to reduce the risk of implant infection.

Abscess↗

PubMed1993

Lack of complications of the hydroxyapatite orbital implant in 250 consecutive cases.

The coral-derived hydroxyapatite sphere is a popular, new integrated orbital implant designed to provide improved motility of the ocular prosthesis following enucleation. Although the implant has rapidly become widely used by ophthalmologists, there is little information available regarding the complications of this technique in a large series of cases. We report our results on our initial 250 consecutive cases of hydroxyapatite implantation for eyes enucleated primarily for intraocular neoplasms, with specific emphasis on the complication an their management. The reasons for enucleation included uveal melanoma (157 cases), retinoblastoma (70 cases), blind painful eye (22 cases), and intraocular medulloepithelioma (1 case). Prior treatment to the eye was performed before enucleation in 47 cases and included repair of ruptured globe (17 cases), plaque radiotherapy (18 cases), external beam radiotherapy (6 cases), and others (6 cases). During a mean of 23 months follow-up (range, 6 to 42 months), there have been no recognizable cases of orbital hemorrhage related to the implant and no cases of implant extrusion or implant migration. There was one case of presumed orbital infection (culture-negative) that resolved with intravenous antibiotics, and the implant was retained within the orbit. Other problems included conjunctival thinning in eight cases managed by observation and prosthesis adjustment and conjunctival erosion in four cases managed by combinations of scleral patch graft, conjunctival flap, and prosthesis adjustment. The conjunctival erosion was caused by a poorly fitting prosthesis in three cases and wound dehiscence in one case. The complication rate in eyes receiving prior radiotherapy or surgery was not increased. The hydroxyapatite integrated orbital implant is a well-tolerated motility implant without the high rate of extrusion and infection seen with other motility implants.

Adult↗

PubMed1993

[Use of hydroxyapatite (Ceros-80) in dental implantology].

The use of lyodura prevents the loss of hydroxyapatite crystals from the operated area during the healing period. Its protective membrane effect prevents infection and other problems during healing. Histological studies have shown that the combined use of "Ceros 80" hydroxyapatite and lyodura within 20 months resulted in the development of new, osseointegrated considerable amount of bone. This bone-hydroxyapatite bond is the base for further implantological and prosthodontic procedures.

Adult↗

PubMed1995

Indications for hydroxyapatite cement reconstruction in lateral skull base surgery.

Preliminary data on the use of hydroxyapatite cement to restore cranial bone integrity has shown excellent results. Cranial base reconstruction has been accomplished for translabyrinthine, middle cranial fossa, and suboccipital craniectomy defects, as well as extensive temporal bone fractures. Fifteen patients have been followed for up to 2 years with no evidence of complication from use of the hydroxyapatite cement. Exposure to cerebrospinal fluid does not appear to alter its stability, and pre-existing infection appears to be the only contraindication to its use. Stability of the cement has been confirmed by serial radiographic analyses. This paper reviews the chemical structure and bioactivity of hydroxyapatite cement and employs case studies to illustrate the applications of this new biomaterial in lateral skull base surgery.

Adult↗

PubMed1996

[An experimental trial of a hydroxyapatite-based root paste].

Hydroxyapatite-based radicular paste was tried in 12 dogs with experimental chronic periodontitis. Hydroxyapatite, zinc-eugenol, and resorcin-formal pastes were compared. The periodontal status was assessed by morphometric methods. Hydroxyapatite-based radicular paste was found to be the most effective means of treating experimental chronic periodontitis. In control groups the therapeutic effect was either null or minimal.

Animals↗

PubMedDate not supplied

Effects of dentin air abrasion with aluminum oxide and hydroxyapatite on adhesive bond strength.

Shear bond strengths to dentin were determined with six current-generation resin adhesive systems following air abrasion of the dentin surface with aluminum oxide and hydroxyapatite. In addition, scanning electron microscopy was used to examine the effects of air abrasive techniques and conditioners/primers on the dentin surfaces. Altering the dentin surface with air abrasion using aluminum oxide and hydroxyapatite did not enhance dentin bond strengths with current-generation adhesive systems. Air abrasion of dentin with aluminum oxide created more surface irregularity than hydroxyapatite. Dentin surfaces air abraded with aluminum oxide and the treated with conditioners that removed the smear layer appeared more irregular than flat ground dentin surfaces treated with the same conditioners.

Acid Etching, Dental↗

PubMedDate not supplied

Eight-year clinical retrospective study of titanium plasma-sprayed and hydroxyapatite-coated cylinder implants.

A total of 1,202 press-fit cylinder implants were placed in 479 patients from March 1986 to March 1994. The patients' ages ranged from 14 to 88 years. The implants included 889 titanium plasma-sprayed implants and 313 hydroxyapatite-coated implants. There were no statistically significant differences in the distribution of hydroxyapatite-coated and titanium plasma-sprayed implants based on implant location, type of restoration, age, and sex. Although differences in long-term success rates based on simple percentages were also not statistically significant, cumulative survival rates based on life table analysis up to 96 months were 92.7% for titanium plasma-sprayed systems and 77.8% for hydroxyapatite-coated systems. Graphical interpretations of these data revealed interesting contrasts, including the timing and results of implant failure, which are discussed in detail.

Adolescent↗

PubMed1996

Resorption kinetics of osseous substitute: natural coral and synthetic hydroxyapatite.

Coral and hydroxyapatite may be used as substitution biomaterials for bone grafts. In this work, we extracted the implants from the femora to study the kinetics of elementary mineral transformation of the osseous substitutes. The use of physical analysis methods such as PIXE (particle-induced X-ray emission) shows that coral and hydroxyapatite, after their implantation in vivo, reach a mineral composition comparable with that of bone. For the first time we have measured the concentration of mineral elements, at different time intervals after implantation, along a cross-section. The distribution according to mineral elements (Ca, P, Sr, Zn, Fe) in the implant, in the receiver site and also at the interface, showed that the kinetics of coral resorption was faster than that of hydroxyapatite; in the same way, the osseous attack was not global but, rather, centripetal.

Animals↗

PubMed1995

Clinical application of coralline hydroxyapatite ocular implants in the eviscerated eyes.

BACKGROUND: During the past several years, coralline hydroxyapatite ocular implant has gained increasingly wide acceptance among ophthalmologists. This ocular implant is used in eviscerated eyes to restore volume loss. Its advantages and complications are presented. METHODS: Seventy-three patients received a coralline hydroxyapatite sphere as a buried integrated ocular implant after evisceration surgery between August 1991 and May 1994. The follow-up period was from 4 to 33 months, with mean of 13.5 months. RESULTS: There have been no recognizable cases of orbital infection, implant extrusion, or implant migration. Complications have been minimal and easily managed. Motility of the socket and fornices has been excellent, and most patients have cosmetically satisfactory motility of the prosthesis. CONCLUSIONS: The hydroxyapatite implant appears to offer excellent cosmetic reconstruction without the unacceptable infection and extrusion rates seen with other implants.

Adolescent↗

PubMed1996

Self-setting hydroxyapatite cement as a carrier for bone-forming cells.

To investigate the feasibility of using self-setting hydroxyapatite cement as a carrier for marrow cells having a high osteogenic ability, a porous form of this cement was fabricated and combined with cultured marrow cells. Marrow cells were obtained from the femurs of a seven-week-old male Fischer 344 rat and cultured in Eagle's MEM containing 15% fetal bovine serum for ten days before being combined with the porous cement or with Interpore 200 hydroxyapatite as a control. The composites were subcutaneously implanted into syngeneic rats and harvested after six weeks. In both types of implants, active osteoblasts together with bone formation were detected in contact with the pore surfaces. No cartilage formation was observed in any of the pores. Both types of implants with and without marrow cells caused very little foreign body reaction. These results indicate that self-setting hydroxyapatite cement containing marrow cells possesses a high osteogenic ability and may be useful as a bone graft substitute as well as a novel delivery system for bone-forming cells.

Animals↗

PubMed1996

[A biological compatibility study of hydroxyapatite].

The biological compatibility of coatings of subcutaneous implants was studied in rat experiments. The implants were coated with hydroxyapatite and hydroxyapatite modified by chloromethylsilanthrane (silamine). The coatings were found to inhibit lipid peroxidation and form the optimal ratio of connective tissue biopolymers in capsules forming round the implants. Both types of hydroxyapatites used were characterized by high biological compatibility.

Animals↗

PubMed1997

The effects of magnesium on hydroxyapatite formation in vitro from CaHPO4 and Ca4(PO4)2O at 37.4 degrees C.

The effects of magnesium ion on the formation of calcium-deficient hydroxyapatite [Ca9HPO4(PO4)5OH, CDHAp] from CaHPO4 and Ca4(PO4)2O dissolution were investigated using two magnesium sources: Mg3(PO4)2 (chemical system 1) or MgCl2 . H2O (chemical system 2) solutions. Because chloroapatite does not form from aqueous solutions, the use of two magnesium sources facilitated the determination of magnesium's role during synthetic hydroxyapatite formation in vitro and possible related effects during biomineralization. Isothermal calorimetry determined the progress of reactions. Two peaks are observed as heat is evolved during the formation of CDHAp in water at 37.4 degrees C. The nucleation and growth of CDHAp are the corresponding mechanisms. Although the time for complete reaction and total heat-of-reaction DeltaHr remain constant, the height of the first peak is reduced as the concentration of magnesium ion approaches 4 mM in either chemical system. Magnesium does not substitute into CDHAp even though there are calcium vacancies available. Subsequent increases cause the remaining heat peak to broaden and the time required for complete reaction to approach 24 hours as the initial MgCl2 concentration reaches 100 mM. Supersaturation limits chemical system 1 to Mg3(PO4)2 concentrations below 10 mM. A MgCl2 concentration of 3.16 M precludes CDHAp from forming for over 3 months; rather newberyite, MgHPO4 . 3H2O, precipitates. The morphology and surface area of the CDHAp formed in 100 mM MgCl2 solution are comparable to those of CDHAp formed in water. The surface areas are approximately 80 m2/g. Magnesium concentrations below 4 mM only inhibit nucleation whereas those above 4 mM inhibit growth as well. Magnesium phosphate complexes are more inhibitory than magnesium chloride complexes. Increasing the liquid-to-solids ratio or agitation significantly increases the induction period before reaction initiates. Increasing the liquid-to-solids ratio increases the time span for growth whereas increasing agitation decreases the time span for growth. The large inhibitory effect of agitation suggests quiescent systems are more suitable for determining the kinetics of HAp formation. A magnesium inorganic chemical activity (alphaMg = gammaMg[Mg2+]) many times greater than that in biological fluids is required before inhibition of hydroxyapatite formation is realized.

Calcium↗

PubMed1997

Liposomes-coated hydroxyapatite and tricalcium phosphate implanted in the mandibular bony defect of miniature swine.

Hydroxyapatite and tricalcium phosphate have been used as bone implants for some period of time. Now unfortunately, these materials have failed to become the nucleation sites for bone regeneration. We hypothesized that coating hydroxyapatite and tricalcium phosphate with negatively charged liposomes may improve the nucleation process for new bone formation. The present study was designed to test this hypothesis. Experiments were carried out in 15 miniature swines' mandibular angle with artificial bony defects. In each of the swine, the bony defects on one side were implanted with either liposomes coated with hydroxyapatite or liposomes coated with tricalcium phosphate, while the other side served as control. At the end of the third and sixth weeks following the operation, we observed result, took histology and radiographs of the operated area. The results showed that liposomes-coated materials were biocompatible and their clinical endpoint was enhanced. At the end of the third week, the implant material was surrounded by dense connective tissues. At the end of the sixth week, there were new bone formations near the implanted material. In addition, liposomes which were immobilized in agarose gel and implanted in the defects showed new bony bridge formation. These observations suggest that liposomes have the ability in promoting repair of osseous deficiencies.

Alveolar Process↗

PubMed1998

[The surgical treatment of jaw cysts using hydroxyapatite with an ultrahigh degree of dispersity].

Ultrahighly dispersed hydroxyapatite, a biochemically active form of hydroxyapatite, stimulates the repair osteogenesis at the early stages. Drugs with ultrahighly dispersed hydroxyapatite: 33% OSTIM-100 paste and its composition with lincomycin Lincogap, which ensures a prolonged release of the antibiotic at the site of implantation, were used for filling the bone cavity formed after cystectomy in 49 patients. In controls (n = 43) the postoperative cavity was filled with blood clot. The results of clinical, x-ray, and radiovisiographic studies indicate that use of the above preparations decreased the incidence of postoperative complications and created the optimal conditions for bone repair at the site of defects of different size. The therapeutic efficacy was the highest when the intervention was preceded by inflammatory symptoms at the site of the cyst.

Adolescent↗

PubMed1997

A hydroxyapatite system for the continuous release of coumadin an anticoagulant.

Coumadin is an anticoagulant used in the treatment of patients with pulmonary thromboembolisms or those implanted with mechanical vascular devices. Its efficacy is complicated by side effects such as hemorrhaging. Administration of coumadin by the traditional routes of pills and injections causes wide fluctuations of the drug in plasma. Thus, experiments were conducted to develop a hydroxyapatite ceramic system for releasing coumadin in vivo continuously for 7-10 days. A series of preliminary in vivo experiments was conducted to determine an effective non-lethal therapeutic dosage of coumadin for rats. Homogenous matrices containing varying amounts of coumadin were implanted subcutaneously in rats and the blood clotting time was determined. Results of these experiments showed that one mg coumadin delivered from HA implants doubled the blood clotting time and did not induce fatal hemorrhage. Subsequent in vitro studies were conducted to determine the most efficient way to deliver coumadin at a slow and sustained rate. Results of these experiments suggested that a solid insert of one mg of compressed coumadin in a hydroxyapatite ceramic shell released the drug more slowly and efficiently than a homogenous matrix consisting of compressed coumadin and hydroxyapatite.

Animals↗

PubMed2006

Physiologic reestablishment of ossicular continuity during excision of retraction pockets: use of hydroxyapatite bone cement for rebridging the incus.

OBJECTIVE: To analyze the results obtained from hydroxyapatite bone cement repair of ossicular discontinuity between the incus and stapes during surgery of retraction pockets. DESIGN: Clinical study of a case series. SETTING: Otolaryngology Department, Tanta University Hospitals, Tanta, Egypt. PATIENTS: A total of 62 previously untreated patients (82 ears) with retraction pockets. INTERVENTIONS: Hydroxyapatite bone cement was used to repair defects at the incudostapedial connection in 82 ears with retraction pockets. The ears were divided into 2 groups: group 1 included 48 ears with a small defect in the long process of the incus; group 2 included 34 ears with a large defect in the long process of the incus. In addition, 20 control patients underwent surgery using plastipore partial ossicular replacement prostheses. Hearing results were reported in 4 frequencies (0.5, 1, 2, and 3 kHz). Analysis of the results was performed using the paired t test with significance level at .05. MAIN OUTCOME MEASURES: Anatomic and audiologic results. RESULTS: Significant postoperative improvement of pure-tone air conduction threshold averages and air-bone gap averages were reported in the 3 studied groups. The postoperative air-bone gap averages showed significantly better outcome in groups 1 and 2 compared with controls (P<.001), while there was no statistically significant difference between groups 1 and 2 (P>.05). CONCLUSIONS: Bone cement ossiculoplasty offers cost-effective and significant improvement in conductive hearing loss. It provides an excellent alternative to ossiculoplasty with preformed prostheses. We believe the indications for bone cement were validated by these results.

Adult↗

PubMed1997

Bending strength of synthetic OH-carbonated hydroxyapatite single crystals.

Although hydroxyapatite (HAP) is applied to medical implants because of its biocompatibility, no data on mechanical strength of HAP single crystals were yet available, partly due to the difficulty in obtaining sufficiently large single crystals. In the present study the bending strength of OH-carbonated hydroxyapatite (CHAP) single crystals containing carbonate of 0.09 CO2 wt % prepared hydrothermally was determined in three-point bending tests. The three-point bending tests were performed using a modified ultra micro-hardness tester with a span of 380 micrograms and a bending direction of <210>. The CHAP single crystals were broken in air, water, and air after immersion in alpha minimum essential medium (alpha MEM) + 10% fetal bovine serum (FBS) for 3 weeks. The average bending strength of the CHAP single crystals was 468 +/- 205, 361 +/- 199 and 501 +/- 212 MPa in air, water, and air after immersion in alpha MEM + 10% FBS, respectively. In all cases the maximum strength at each crystal thickness value decreased in inverse proportion to the thickness.

Animals↗

PubMed1998

Influence of sterilization by gamma irradiation and of thermal annealing on creep of hydroxyapatite-reinforced polyethylene composites.

Sterilization of medical devices by gamma (gamma)-irradiation is common. The effect of irradiation on a bone replacement material, HAPEX (hydroxyapatite-reinforced polyethylene composite), was investigated. Unfilled and hydroxyapatite-filled polyethylene at 0.20 and 0.40 filler volume fractions were gamma-irradiated at 2.5 Mrad, and the modified properties were studied by differential scanning calorimetery, isochronous experiments, and creep tests. The effect of thermal annealing of the samples from 140 degrees C also was examined. The results suggest that both irradiation and annealing increase creep resistance of the materials. These are associated with the formation of crosslinks and an increase in crystallinity, respectively.

Biocompatible Materials↗