Hydroxylapatite Implants Research Articles

Aesthetic Implantation of Calcium Hydroxylapatite Does Not Interfere With Radiological Assessment of Bones in the Dorsum of the Hands.

Calcium hydroxylapatite (CaHA) is a radiopaque dermal filler used to provide volume correction in the dorsum of the hand. The aim of this study was to evaluate whether CaHA implantation in the dorsum of the hand interferes with radiological assessment by obscuring the bones. This 2-year, prospective, single-center, open-label study enrolled 20 subjects with Merz Hand Grading Scale (MHGS) grades ranging from moderate (MHGS 2 or 3; n = 10) to very severe (MHGS 4; n = 10). All subjects received an initial CaHA treatment and were offered up to 3 retreatments to provide volume correction in the dorsum of the hands, over a period of 18 months. Bone obscuration was assessed by blinded, licensed radiologists responsible for interpreting plain radiographs (X-rays). CaHA was seen to be present in 100% of hands in Month 1 X-rays and in 83.3% in Month 24 X-rays, but no bone obscuration was reported in any X-rays at any evaluated time point. According to blinded radiologists, treatment with CaHA in the dorsum of the hand does not obscure radiographic assessment of the bones seen on X-rays up to 24 months after initial injection. The safety of CaHA retreatment was also demonstrated by the lack of bone obscuration after multiple retreatments.

Radiological evaluation of calcium hydroxylapatite implantation to correct volume loss in the dorsum of the hand

Radiological evaluation of calcium hydroxylapatite implantation to correct volume loss in the dorsum of the hand

MORPHOLOGICAL STRUCTURE OF THE HUMERUS WITH IMPLANTATION INTO THE TIBIAL BONE HYDROXYAPATITE MATERIAL OC-015, ALLOYED BY MANGANESE

In the experiment on 252 albino rats with initial body weight of 135-145g it is established, that making the defect 2,2 mm in diameter on the border of proximal metaphysis and diaphysis of the tibial bone is accompanied by decrease of a mechanical strength of the humeral bones. At the same time the amplitude of deviations depends on the degree of activity of reparative regeneration processes. Implantation of biogenic hydroxylapatite ОC- 015 into the area of defect is accompanied by similar deviations which are completely leveled to the late terms of observation. Implantation of ОC-015 into the osseous defect, alloyed by manganese, substantially smoothes the deviations found.

Revision medialization thyroplasty with hydroxylapatite implants

INTRODUCTION Medialization thyroplasty is a useful tool in the management of dysphonia and dysphagia with aspiration secondary to unilateral vocal fold impairment. A variety of implant materials have been used for medialization thyroplasty including silicone elastomer (Silastic, Dow Corning Corporation, Midland, MI), expanded polytetrafluoroethylene (Gore-Tex, Gore, Newark, DE), and hydroxylapatite (VoCoM, Gyrus ENT, Bartlett, TN). Successful revision with like-material replacement of both Silastic and Gore-Tex medialization thyroplasty has previously been reported; however, no similar description exists for hydroxylapatite revisions. The approach to revision is dependant upon the initial implant material due to varying degrees of incorporation of the prosthesis into the surrounding tissues. Histologic examination following implantation of either Silastic or Gore-Tex prostheses in a rabbit model demonstrated fibrous encapsulation. In contrast, following implantation of a hydroxylapatite prosthesis, osteogenesis with lamellar bone formation was identified between the thyroid lamina fenestra and the implant. This osteogenesis, that provides implant stability and decreased potential for migration, also creates difficulty in regard to removal due to loss of tissue planes. This article will address the surgical method of revision medialization thyroplasty when hydroxylapatite has been used as the initial implant material. In addition, we will present previously unpublished retrospective data to support the safety and effectiveness of this revision technique.

Dose-dependent osteoinductive effects of bFGF in rabbits

Growth factors lead to the induction of tissue regeneration in bone healing when coated on biomaterials. Basic fibroblast growth factor (bFGF) combines osteoinduction and neoangiogenesis. This study evaluated bFGF-coated hydroxylapatite implants in two experimental groups with 10 or 100 μg (n = 5 per group) compared with uncoated control implants in the rabbit patellar groove model. We observed an unexpected ineffectiveness compared to the control groups with no significant difference of bone growth after 35 days. However, all samples from the 100 μg experiment (control and coated implant) showed significantly stronger 19–25 day label than both 10 μg groups (control and coated implant). Earlier bone labels are stronger in the 10 μg group with equal observation of similarity between experiment and control site and may indicate a possible inhibitory effect of the higher dosing or osteoclast induction. This result indicates a possible systemic effect of the transient growth factor coating.

Autologous dermis graft at the time of evisceration or enucleation

Aim:To present a new technique using autologous dermis graft at the time of enucleation or evisceration to replace the ocular surface area lost when the corneal scleral button is excised.Methods:A...

Primary human marrow stromal cells and Saos-2 osteosarcoma cells use different mechanisms to adhere to hydroxylapatite.

One important step in bone formation on hard tissue implants is adhesion of osteoblast precursors to the implant surface. In this study, we used function-blocking antibodies against integrin subunits to characterize the mechanisms used by human marrow stromal cells and Saos-2 osteosarcoma cells to adhere to protein-coated hydroxylapatite (HA). We found that Saos-2 use both alpha5- and alphav-containing integrins, whereas stromal cells use alphav-containing integrins but not alpha5-containing integrins, despite the presence of alpha5-containing integrins on cell surfaces. On the basis of this difference, we examined binding of these cell types to HA coated with fibronectin (FN) or vitronectin (VN), to determine whether these ligands for alpha5 and alphav integrins could enhance the numbers or morphology of cells adhered to them. We also examined the adhesion of cells to HA coated with RGD peptides designed to bind to FN or VN receptors. Morphology and number of adherent stromal cells were markedly enhanced on serum-coated surfaces compared with FN or VN alone, whereas, surprisingly, Saos-2 cells failed to spread on serum-coated HA and displayed superior spreading and stress fiber formation on FN-coated [corrected] HA. Collectively, these results have important implications for the design of protein coatings to enhance the performance of HA implants.

Effect of KTP laser on implants used in middle-ear surgery.

The present study is intended to explore the effects of the KTP laser on various types of implant, used in middle-ear surgery. A laboratory study was undertaken to evaluate the interaction between the KTP laser (KTP-532 Orion Laser, Laserscope, UK) and individual middle-ear implants. A variety of middle-ear implants were used: a silicone sheet, Teflon, hydroxylapatite, ionomeric cement, gold and titanium prostheses as well as gelfoam. Following exposure to the laser, these implants were studied by direct inspection using an operating microscope. The KTP laser induced no detectable alteration in any of the implants when they were clean and dry. However, in the presence of fresh blood, under the influence of the energy of the absorbed laser, the silicone burnt and melted and the Teflon piston was vaporized. Likewise, a few tiny holes appeared on the surface of the ionomeric implant and then the prosthesis deformed. The hydroxylapatite implant broke into two pieces. However, no detectable alteration could be observed on gold or titanium pistons, even in the presence of blood. The authors conclude, that in the presence of blood, interaction between the KTP laser and both silicone and hydroxylapatite implants needs to be avoided. Teflon prostheses can be cautiously vaporized. Gold and titanium prostheses were unaffected by laser even in the presence of blood.

Biomechanical and histological studies of particulate hydroxylapatite implanted in femur bone defects of adult dogs

The purpose of this study was to investigate the biomechanical behavior and the histology of particulate hydroxylapatite (HA) implanted in bone defects created in femurs of 48 adult mongrel dogs. The bone defects, measuring 10×10×25 mm with or without HA implantation, were allowed to heal until the end of the 1 st, 2 nd, 3 rd, 6 th, 9 th and 12 th months after surgery. The harvested tissue specimens from the implant sites were processed into long cubic or rectangular prismatic forms. Their mechanical strengths were assessed using compression and shearing tests to measure the maximal compressive and shear stress by force loading on the middle portions of the specimens. Histological sections of each stage were processed with both decalcified and nondecalcified methods. The results showed that the mechanical strength of the tested specimens was closely related to the tissue regeneration within the bone defect. Progressive regeneration of new bone was observed at each stage, with complete bone formation at the 9-month period. A consistent increase in both maximal compressive stress and maximal shear stress was noted at each stage, responsive to the ossification and maturation of the regenerating tissue within the bone defect. This animal model provides a novel approach to directly estimate the tissue strength of the HA-implanted bone defect.

Biomechanical and histological studies of particulate hydroxylapatite implanted in femur bone defects of adult dogs

The purpose of this study was to investigate the biomechanical behavior and the histology of particulate hydroxylapatite (HA) implanted in bone defects created in femurs of 48 adult mongrel dogs. The bone defects, measuring 10×10×25 mm with or without HA implantation, were allowed to heal until the end of the 1st, 2nd, 3rd, 6th, 9th and 12th months after surgery. The harvested tissue specimens from the implant sites were processed into long cubic or rectangular prismatic forms. Their mechanical strengths were assessed using compression and shearing tests to measure the maximal compressive and shear stress by force loading on the middle portions of the specimens. Histological sections of each stage were processed with both decalcified and nondecalcified methods. The results showed that the mechanical strength of the tested specimens was closely related to the tissue regeneration within the bone defect. Progressive regeneration of new bone was observed at each stage, with complete bone formation at the 9-month period. A consistent increase in both maximal compressive stress and maximal shear stress was noted at each stage, responsive to the ossification and maturation of the regenerating tissue within the bone defect. This animal model provides a novel approach to directly estimate the tissue strength of the HA-implanted bone defect.

Long‐term ingrowth and apposition of porous hydroxylapatite implants

Long‐term ingrowth and apposition of porous hydroxylapatite implants

A comparative study of flexible (PolyactiveR) versus rigid (hydroxylapatite) permucosal dental implants. I. Clinical aspects

Recently, an elastomeric polyethyleneoxide polybutylene-terephthalate (PEO:PBT) copolymer (Polyactive) was introduced, which exhibits bone-bonding characteristics. In contrast to ceramics, bioglass, titanium and other metals, PEO:PBT copolymers are flexible materials that could reduce undesirable peak stresses along the neck of a permucosal implant. The application of three types of Polyactive permucosal dental implants (one dense and two porous types) and one dense hydroxylapatite (HA) implant were clinically tested and compared during 30 weeks of loading in a dog experiment. With respect to the porous Polyactive implants, it was observed that the pore diameter had decreased to such an extent that optimal bone ingrowth was not achieved. Polyactive is known to expand due to water uptake, and, as a consequence, the sizes of the pores of the press-fit inserted implants had decreased to a large extent. This feature explained the high loss of the implants with the porous outer layer (6 out of 22). None of the dense Polyactive implants and only one of the HA implants were lost. Statistical analysis was performed solely on the dense Polyactive and the HA implants. At the lingual sites, plaque scores, gingiva indices, bleeding indices and corresponding pocket depths were statistically significantly lower for both implant types, when compared to the corresponding values at the buccal, mesial and distal sites, irrespective of the observation period. Differences between the dense Polyactive and the HA implants were not observed. A considerable difference in mobility was registered between the Polyactive and the hydroxylapatite implants, as measured by the Periotest. The dense Polyactive implants functioned adequately and had mobility resembling natural teeth. As such, these dense flexible materials showed a favourable clinical function and they seem promising for reducing undesired peak stresses when applied as a dental implant.

A comparative study of flexible (Polyactive®) versus rigid (hydroxylapatite) permucosal dental implants. I. Clinical aspects

summary Recently, an elastomeric polyethylene‐oxide polybutylene‐terephthalate (PEO:PBT) copolymer (Polyactive®) was introduced, which exhibits bone‐bonding characteristics. In contrast to ceramics, bioglass, titanium and other metals, PEO:PBT copolymers are flexible materials that could reduce undesirable peak stresses along the neck of a permucosal implant. The application of three types of Polyactive®permucosal dental implants (one dense and two porous types) and one dense hydroxylapatite (HA) implant were clinically tested and compared during 30 weeks of loading in a dog experiment. With respect to the porous Polyactive® implants, it was observed that the pore diameter had decreased to such an extent that optimal bone ingrowth was not achieved. Polyactive® is known to expand due to water uptake, and, as a consequence, the sizes of the pores of the press‐fit inserted implants had decreased to a large extent. This feature explained the high loss of the implants with the porous outer layer (6 out of 22). None of the dense Polyactive® implants and only one of the HA implants were lost. Statistical analysis was performed solely on the dense Polyactive® and the HA implants. At the lingual sites, plaque scores, gingiva indices, bleeding indices and corresponding pocket depths were statistically significantly lower for both implant types, when compared to the corresponding values at the buccal, mesial and distal sites, irrespective of the observation period. Differences between the dense Polyactive® and the HA implants were not observed. A considerable difference in mobility was registered between the Polyactive® and the hydroxylapatite implants, as measured by the Periotest®. The dense Polyactive® implants functioned adequately and had mobility resembling natural teeth. As such, these dense flexible materials showed a favourable clinical function and they seem promising for reducing undesired peak stresses when applied as a dental implant.

A comparative study of flexible (Polyactive®) versus rigid (hydroxylapatite) permucosal dental implants. II. Histological aspects

summary Of the many materials that are applied in dental implantology, most have a high Young's modulus. In the concept of osseointegration, which is generally preferred, chewing forces are therefore directly transmitted from rigid implant materials to the relatively flexible surrounding bone. Polyactive® is an elastomeric polyethylene‐oxide polybutylene‐terephthalate (PEO:PBT) copolymer, with a low modulus of elasticity, that exhibits bone‐bonding characteristics. Previous finite‐element analysis emphasized the benefit of the application of flexible implant materials. To assess the validity of this finite element model, one dense and two porous types of flexible Polyactive® permucosal dental implants and one rigid hydroxylapatite (HA) implant were clinically tested in a beagle dog study and were compared during 30 weeks of loading. In an earlier report, it was concluded that dense Polyactive® implants function clinically adequately and resemble the mobility of natural teeth. In the current study, the amount of bone contact was quantitatively assessed. Polyactive® implants showed a statistically significantly higher bone contact, as compared to the HA implants, probably due to a significant water uptake and a subsequent increase in the volume of the denser Polyactive®. Morphological analysis, based on back‐scatter electron microscopy and light microscopy, revealed little remodelling activity of the bone surrounding the Polyactive® implants. Few remodelling lacunae were seen and de novo bone formation was rarely observed. At some locations, a continuity between calcification zones with the polymer surface and the surrounding interfacial bone was observed, indicating the occurrence of bone‐bonding. Also, the bone surrounding the HA implants showed little remodelling activity, although large resorption lacunae were observed, in which HA particles were present. Based on the observations of this study, flexible bone bonding implants might be more capable of transferring stresses to the surrounding bone and are therefore promising alternatives to ‘routine’ rigid implants.

Prostaglandin release from rat femurs after implantation of hydroxylapatite and aluminium oxide ceramics

The bony reaction after implantation of uncemented ceramics is of special interest. Therefore porous and dense hydroxylapatite and aluminium oxide ceramics were implanted in rat femurs. One group received no surgical manipulation and another with a sham procedure where no ceramics were implanted served as controls. After 6 and 10 days the rat femurs were harvested and the release of PGE 2 and 6-keto-PGF 1α was measured with specific radioimmunoassays. Decrease in the release of PGE 2 from day 6 to day 10 was present in all three implants. In contrast, 6-keto-PGF 1α increased from day 6 to day 10. Comparing the ceramic types an increase in 6-keto-PGF 1α release was seen in the porous hydroxylapatite group. These prostaglandin (PG) release patterns after ceramic implantation are similar to those of fracture healing, but aluminium oxide seems to be inert, while hydroxylapatite, especially the porous type, stimulates 6-keto-PGF 1α release.

Subperiosteal tissue expansion for mandibular augmentation with hydroxylapatite particles: An experimental study

The utility of subperiosteal tissue expansion (STE) for mandibular augmentation with hydroxylapatite (HA) particles was evaluated experimentally in two groups of dogs. Eight grams of solid HA particles were implanted in previously formed bilateral subperiosteal expanded beds on the mandible. In one group, the HA particles were implanted in the intact subperiosteal expanded bed and in the other the newly formed capsule overlying the bone was removed before implantation of HA. Despite marked augmentation with a large number of HA particles, there was neither deformity nor infection of the implants, which maintained the original desired contour. The firm fibrous capsule formed by STE allowed consolidation of the HA particles and prevented their migration. In the first group, although histologic evidence of bony union of the implanted particles was not seen even after 2 months, clinical immobilization of the grafts was achieved in 1 to 2 months. After 1 year, substantial bone growth into the implants was observed. In the second group, clinical immobilization was observed even after 2 weeks. Histologic evidence of bony union of the particles located along the surface of the mandible was observed after 1 or 2 months. In these specimens, however, marked bone resorption of the mandibular cortex, was also noted. No evidence of bone or osteoid formation on the expanded periosteal side was noted in either group. These results provide fundamental data regarding mandibular augmentation using STE, and indicate that the subperiosteal expanded bed is an excellent recipient site for onlayed implants.

Histomorphometric examination of healing around hydroxylapatite implants in 60Co-irradiated bone

The purpose of this study was to histomorphometrically evaluate the use of hydroxylapatite (HA) implants in 60Co-irradiated bone. HA implants were installed in rabbit mandibles 3 months, 6 months, and 12 months after 15-Gy irradiation. Nonirradiated rabbits served as controls. The rabbits were killed 7, 14, 30, 60, and 90 days after the HA implantation. The histologic features of the healing process were examined and histomorphometric measurements were made to quantify the percentage of HA-bone contact and trabecular bone in the medullary cavity. In the irradiated groups, although HA-bone contact was observed later than that in the controls, recovery increased with time after irradiation and the rate of HA-bone contact bone-contacting implant surface ratio; BCSR exceeded 90% in all groups examined before 90 days. In the radiated groups, the average trabecular bone-specific volume was lower than that in the controls and began to decrease before BCSR exceeded 90%. Based on the present data, as well as data from the literature, it is suggested that the success rate of HA implants in irradiated bone increases with the interval after radiotherapy. It is also recommended that HA implants in irradiated bone be installed so that bearing by the cortical bone is increased.

Discussion: Histomorphometric Examination of Healing Around Hydroxylapatite Implants in 60Co-Irradiated Bone

Discussion: Histomorphometric Examination of Healing Around Hydroxylapatite Implants in 60Co-Irradiated Bone

Hydroxylapatite Laryngeal Implants for Medialization

Laryngeal implantation for medialization has improved our ability to manage the patient with vocal fold motion impairment. We present preliminary data evaluating the use of preformed hydroxylapatite laryngeal implants and instrumentation for rapid determination of implant size and position. A window in the thyroid ala is created by means of a standard fenestra template. One of 5 prosthesis templates is inserted through the window for determination of correct size and position. The corresponding implant is then inserted and secured with a hydroxylapatite shim. Thirty-five patients have been implanted for vocal fold paralysis, and 4 patients were implanted for soft tissue deficits or bowing. Thirty-one of 35 patients have reported subjective improvement (89%). Improvement was demonstrated in 13 of 15 (87%) patients with complete preoperative and postoperative objective voice function measurements. Complications include 1 implant extrusion and 1 case of airway obstruction secondary to edema. Preliminary results indicate that prefabricated hydroxylapatite implants are effective for medialization thyroplasty. Advantages include a readily available implant selection, rapid determination of correct size and position, and improved implant stabilization with a hydroxylapatite shim.

The effect of aging on the healing of hydroxylapatite implants

The purpose of this study was to investigate the effect of aging on the healing process after insertion of a hydroxylapatite (HA) implant into bone. Three groups of eight male Wistar rats, aged 6 weeks (young group), 12 weeks (adult group), and approximately 2 years (old group) were used in this experiment. Two implants were placed into the tibia of each rat. The animals were killed 7, 14, 28, and 56 days after implantation, and 15-microns, hematoxylin-eosin-stained, undecalcified sections were prepared. The healing process was examined histologically, and histomorphometric measurements were made by a computer-based image analyzer to quantify the percentage of HA-bone contact and trabecular bone in the medullary cavity. In the young group, new trabecular bone formed actively around the HA implant and good HA-bone contact was achieved more rapidly than in the adult group. In the old group, both the quantity of newly formed trabecular bone around the implant and the extent of HA-bone contact were less than in the other groups. The results suggest that the rate and volume of new bone formation around implants decrease with increasing age.