A bioceramic scaffold composed of strontium-doped three-dimensional hydroxyapatite whiskers for enhanced bone regeneration in osteoporotic defects

Reconstruction of osteoporotic bone defects is a clinical problem that continues to inspire the design of new materials. Methods: In this work, bioceramics composed of strontium (Sr)-doped hydroxyapatite (HA) whiskers or pure HA whiskers were successfully fabricated by hydrothermal treatment and respectively named SrWCP and WCP. Both bioceramics had similar three-dimensional (3D) porous structures and mechanical strengths, but the SrWCP bioceramic was capable of releasing Sr under physiological conditions. In an osteoporotic rat metaphyseal femoral bone defect model, both bioceramic scaffolds were implanted, and another group that received WCP plus strontium ranelate drug administration (Sr-Ran+WCP) was studied for comparison. Results: At week 1 post-implantation, osteogenesis coupled blood vessels were found to be more common in the SrWCP and Sr-Ran+WCP groups, with substantial vascular-like structures. After 12 weeks of implantation, comparable to the Sr-Ran+WCP group, the SrWCP group showed induction of more new bone formation within the defect as well as at the implant-bone gap region than that of the WCP group. Both the SrWCP and Sr-Ran+WCP groups yielded a beneficial effect on the surrounding trabecular bone microstructure to resist osteoporosis-induced progressive bone loss. While an abnormally high blood Sr ion concentration was found in the Sr-Ran+WCP group, SrWCP showed little adverse effect. Conclusion: Our results collectively suggest that the SrWCP bioceramic can be a safe bone substitute for the treatment of osteoporotic bone defects, as it promotes local bone regeneration and implant osseointegration to a level that strontium ranelate can achieve.

A Comparative Study with Biphasic Calcium Phosphate to Deproteinized Bovine Bone in Maxillary Sinus Augmentation: A Prospective Randomized and Controlled Clinical Trial

PURPOSE

The purpose of this study was to evaluate a new graft material, biphasic calcium phosphate, composed of 60% hydroxyapatite and 40% β-Tricalcium phosphate and deproteinized bovine bone mineral, which is established as a predictable graft material for maxillary sinus augmentation.

MATERIALS AND METHODS

Maxillary sinus augmentation was performed with different bone materials. Bone biopsies were performed on tissue harvested from the future implant bed using a trephine bur at 6 months after maxillary sinus augmentation. Resonance frequency analysis was performed immediately and at 6 months after the implant placement. Microcomputed tomography and histomorphometric analysis were performed in all patients.

RESULTS

Fifty-six patients (60 sinuses) were included in the study. At 6 months postoperative, 31 biopsies were performed on tissues harvested from the calcium phosphate, and 29 biopsies on tissues from the bovine bone grafts. There was no implant failure during the 21-month mean follow-up period. The overall implant stability quotient values were higher than 60, and gradually increased for 6 months. Higher new bone volume fraction and new bone surface density were observed in the calcium phosphate group compared with the bovine bone group. In contrast, residual bone graft volume in the bovine bone group was higher than that in the calcium phosphate group. Nevertheless, there was no significant difference between groups in the microcomputed tomography and histomorphometric parameters.

CONCLUSION

Within the study's limitations, both graft materials demonstrated similar biocompatibility and osteoconductivity in the maxillary sinus augmentation.

The Influences of Different Ratios of Biphasic Calcium Phosphate and Collagen Augmentation on Posterior Lumbar Spinal Fusion in Rat Model

PURPOSE

To determine the influence of different ratios of hydroxyapatite (HA)/beta tricalcium phosphate (β-TCP) and collagen augmentation for posterior lumbar fusion in a rat model.

MATERIALS AND METHODS

We generated a posterior lumbar fusion model in 50 rats and divided it into five groups of equal number as follows; 1) autologous bone graft as group A, 2) 70% HA+30% β-TCP as group B, 3) 70% HA+30% β-TCP+collagen as group C, 4) 30% HA+70% β-TCP as group D, and 5) 30% HA+70% β-TCP+collagen as group E. Rats were euthanized at 12 weeks after surgery and fusion was assessed by manual palpation, quantitative analysis using microCT and histology.

RESULTS

The score of manual palpation was significantly higher in group C than group E (3.1±1.1 vs. 1.8±0.8, p=0.033). However, in terms of microCT analysis, group D showed significantly higher scores than group B (5.5±0.8 vs. 3.1±1.1, p=0.021). According to quantitative volumetric analysis, 30% HA+70% β-TCP groups (group D and E) showed significantly reduced fusion mass at 12 weeks after surgery (123±14.2, 117±46.3 vs. 151±27.3, p=0.008, 0.003, respectively). Collagen augmentation groups revealed superior results in terms of both microCT score and histologic grade.

CONCLUSION

A 7:3 HA/β-TCP ratio with collagen augmentation rather than a 3:7 HA/β-TCP ratio could be a more favorable graft substitute for lumbar spinal fusion. There was positive role of collagen as an adjunct for spinal bone fusion process.

[Computed tomographic evaluation of the healing of experimental defect of a long bone of the skeleton after implantation into its cavity osteoplastic material "Cerabone®"]

Described in the literature properties of osteoplastic material "Cerabone®" have been obtained from studies in the maxilla and cancellous bone. The lack of data on the impact of «Cerabone®» on the dynamics of the healing of defects of compact substance of the long bones of the skeleton dictates the need for such studies. Implantation of osteoplastic material «Cerabone ®» was performed into the defect of rat femoral shaft followed by computer-tomographic analysis of its healing. Starting from the 30th day until the end of the experiment (120th day) there were found faint signs of rarefaction in the distal part adjacent to the defect of parent bone, with no signs of bone resorption in its proximal part. There was identified an extremely high density of the implantation site «Cerabone®», no visible radiographic evidence of resorption of osteoplastic material and ensuring by the latter the stability of volume of the defect in cortical bone at all stages of the experiment.

Hollow hydroxyapatite microspheres: a novel bioactive and osteoconductive carrier for controlled release of bone morphogenetic protein-2 in bone regeneration

The regeneration of large bone defects is a common and significant clinical problem. Limitations associated with existing treatments such as autologous bone grafts and allografts have increased the need for synthetic bone graft substitutes. The objective of this study was to evaluate the capacity of novel hollow hydroxyapatite (HA) microspheres to serve as a carrier for controlled release of bone morphogenetic-2 (BMP2) in bone regeneration. Hollow HA microspheres (106-150 μm) with a high surface area (>100 m2 g(-1)) and a mesoporous shell wall (pore size 10-20 nm) were created using a glass conversion technique. The release of BMP2 from the microspheres into a medium composed of diluted fetal bovine serum in vitro was slow, but it occurred continuously for over 2 weeks. When implanted in rat calvarial defects for 3 or 6 weeks, the microspheres loaded with BMP2 (1 μg per defect) showed a significantly better capacity to regenerate bone than those without BMP2. The amount of new bone in the defects implanted with the BMP2-loaded microspheres was 40% and 43%, respectively, at 3 and 6 weeks, compared to 13% and 17%, respectively, for the microspheres without BMP2. Coating the BMP2-loaded microspheres with a biodegradable polymer, poly(lactic-co-glycolic acid), reduced the amount of BMP2 released in vitro and, above a certain coating thickness, significantly reduced bone regeneration in vivo. The results indicate that these hollow HA microspheres could provide a bioactive and osteoconductive carrier for growth factors in bone regeneration.

[Cationic liposome ceftazidime combined with nano-hydroxyapatite/beta-tricalcium phosphate for treatment of chronic osteomyelitis of rabbits]

OBJECTIVE

To observe the effect of cationic liposomal ceftazidime (CLC) combined with nano-hydroxyapatite/beta-tricalcium phosphate (n-HA/beta-TCP) in the treatment of chronic osteomyelitis of rabbits.

METHODS

Thirty healthy New Zealand white rabbits (4-6 months old; weighing, 2-3 kg) were selected to prepare the chronic osteomyelitis models. After 4 weeks, the gross observation, X-ray examination, and bacteriological and histopathological examinations were done; the models were made successfully in 27 rabbits. Of 27 rabbits, 24 were randomly divided into 4 groups (n = 6): only debridement was performed in group A; ceftazidime was given (90 mg/kg), twice a day for 8 weeks after debridement in group B; ceftazidime and n-HA/beta-TC were implanted after debridement in group C; and CLC and n-HA/beta-TCP were implanted after debridement in group D. Before and after treatments, X-ray examination was done, and Norden score was recorded. At 8 weeks after treatment, the specimens were harvested for gross observation and for gross bone pathological score (GBPS) using Rissing standard; half of the specimens was used for histological observation and Smeltzer scoring, the other half for bacteriological examination and calculation of the positive rate of bacteria culture.

RESULTS

At 8 weeks after treatment, Norden score of group D was significantly lower than that of groups A, B, and C (P < 0.05), but no significant difference was found among groups A, B, and C (P > 0.05). At 8 weeks after treatment, sinus healed in groups C and D, but sinus was observed in groups A and B; the GBPS scores of groups C and D were significantly lower than those of groups A and B (P < 0.05). The Smeltzer scores of groups C and D were significantly lower than those of groups A and B (P < 0.05). The positive rates of bacteria culture of groups C (0) and D (0) were significantly lower than those of group A (25.0%) and group B (16.7%) (P < 0.05).

CONCLUSION

CLC combined with n-HA/beta-TCP has good effect in treating chronic osteomyelitis of rabbits, and it has better effect in treating chronic osteomyelitis of rabbits than ceftazidime with n-HA/beta-TCP.

Clinical-radiological study on the role of biostimulating materials in iatrogenic furcation lesions

Root perforation is an unwanted incident which may occur at any stage of endodontic treatment and can adversely affect tooth prognosis.

AIM

To compare the recovery rate after treatment of root perforations in the interradicular area of the molars, using two different materials: MTA and ceramic nanoparticles mineral cement DiaRoot BioAggregate, by a clinical-radiological and statistical analysis over a period of up to 24 months.

MATERIAL AND METHODS

The study was conducted on 28 molars from patients of both sexes, mean age 33.29 +/- 6.2DS, with iatrogenic perforation of pulp chamber floor. The teeth were divided into 2 groups according to the applied material: group 1--gray MTA (ProRoot MTA, Dentsply, Tulsa Dental), and group 2--BioAggregate (Diadent Group International, Vancouver). Patients included in the study were monitored and assessed by radiological examinations at 6, 12 and 18 months.

RESULTS

Pulp chamber floor perforations are significantly associated with tooth location (chi2 = 35.60, r = 0.67, p = 0.00359, 95% CI). Both when the perforation was repaired with MTA and BioAggregate, the clinical improvement was significant (chi2 = 17.608, r = 0.58, p = 0.0035, 95% CI).

CONCLUSIONS

Based on the results of this study, both MTA and BioAggregate are excellent materials for root perforation repair.

The role of remineralizing agents in dentistry: a review

Minimal intervention is a key phrase in today's dental practice. Minimal intervention dentistry (MID) focuses on the least invasive treatment options possible in order to minimize tissue loss and patient discomfort. Concentrating mainly on prevention and early intervention of caries, MID's first basic principle is the remineralization of early carious lesions, advocating a biological or therapeutic approach rather than the traditional surgical approach for early surface lesions. One of the key elements of a biological approach is the usage and application of remineralizing agents to tooth structure (enamel and dentin lesions). These agents are part of a new era of dentistry aimed at controlling the demineralization/ remineralization cycle, depending upon the microenvironment around the tooth. This article details the various agents that enhance and/or promote remineralization and discusses their clinical implications.

Bone formation on apatite-coated titanium with incorporated BMP-2/heparin in vivo

OBJECTIVE

The objective of this study was to investigate whether the in vivo osteoinductive activity of an implant material is enhanced by covering the surface of apatite with incorporated bone morphogenetic protein 2 (BMP-2) and heparin which maintains the activity of BMP-2.

STUDY DESIGN

Titanium implants were alkaline treated, heat activated, and soaked in stimulated body fluid with or without BMP-2/heparin to coat the apatite around them. Treated implant bars were then implanted in rat tibiae. After 3 weeks, nondecalcified sections were prepared and the new bone formation around the implants was examined.

RESULTS

A greater amount of bone formed on the apatite-coated implants containing BMP-2/heparin than on apatite-coated implants containing BMP, with >or=3 microg/mL heparin. Apatite-coated titanium implants with BMP-2/heparin had significantly enhanced new endosteal bone formation, with increases vertically (134%) and horizontally (124%).

CONCLUSIONS

Bone formation was stimulated around the apatite-covered titanium coated with BMP-2/heparin, which may be useful in improving implant therapy.

Effectiveness of radiation synovectomy with samarium-153 particulate hydroxyapatite in rheumatoid arthritis patients with knee synovitis: a controlled randomized double-blind trial

OBJECTIVES

The aim of the present study was to investigate the effectiveness of Samarium(153)-particulate hydroxyapatite radiation synovectomy in rheumatoid arthritis patients with chronic knee synovitis.

METHODS

Fifty-eight rheumatoid arthritis patients (60 knees) with chronic knee synovitis participated in a controlled double-blinded trial. Patients were randomized to receive either an intra-articular injection with 40 mg triamcinolone hexacetonide alone (TH group) or 40 mg triamcinolone hexacetonide combined with 15 mCi Samarium(153)-particulate hydroxyapatite (Sm/TH group). Blinded examination at baseline (T0) and at 1 (T1), 4 (T4), 12 (T12), 32 (T32), and 48 (T48) weeks post-intervention were performed on all patients and included a visual analog scale for joint pain and swelling as well as data on morning stiffness, flexion, extension, knee circumference, Likert scale of improvement, percentage of improvement, SF-36 generic quality of life questionnaire, Stanford Health Assessment Questionnaire (HAQ), Lequesne index, use of non-steroidal anti-inflammatory drugs or oral corticosteroids, events and adverse effects, calls to the physician, and hospital visits.

RESULTS

The sample was homogeneous at baseline, and there were no withdrawals. Improvement was observed in both groups in relation to T0, but no statistically significant differences between groups were observed regarding all variables at the time points studied. The Sm/TH group exhibited more adverse effects at T1 (p<0.05), but these were mild and transitory. No severe adverse effects were reported during follow-up.

CONCLUSION

Intra-articular injection of Samarium(153)-particulate hydroxyapatite (15 mCi) with 40 mg of triamcinolone hexacetonide is not superior to triamcinolone hexacetonide alone for the treatment of knee synovitis in patients with rheumatoid arthritis at 1 y of follow-up.

Icing and multilayering technique of injectable hydroxyapatite cement paste for cranial base reconstruction after transsphenoidal surgery: technical note

OBJECTIVE

Injectable hydroxyapatite cement (HAC, Biopex; Mitsubishi Pharma Corp., Osaka, Japan) can reconstruct the accurate contour of bone defects intraoperatively, and it is slowly replaced with bone by a process of resorption and osteoconduction, making it a useful substrate for the repair of cranial defects. In the operative site with continuous oozing of the cerebrospinal fluid, however, the implanted HAC may be dissolved and washed out as a result of its water solubility during the setting time. For successful reconstruction of cranial defects in such wet situations, we describe a new technique to reinforce the implanted HAC with a multilayered application.

METHODS

As a preliminary experiment, we observed that the setting process of the HAC was severely restricted by the environmental temperature. At a temperature of 5 degrees C, the initial setting time of the HAC could be extended to 10 hours after the beginning of the mixing of the HAC. Bone defects of the sellar floor after transsphenoidal surgery for pituitary adenomas, craniopharyngiomas, meningiomas, or suprasellar arachnoid cysts were reconstructed using the HAC in 55 patients during a 5-year period. The results and complications were obtained through retrospective review.

RESULTS

Ninety-eight percent of bone defects were successfully repaired using the HAC, and the reconstruction remained stable over the course of this study. There was one case of postoperative cerebrospinal fluid leakage. Wound infection occurred in one patient, which required reoperation and removal of the biomaterial.

CONCLUSION

The icing and multilayering method for proper use of this biomaterial resulted in restoration of the integrity of the cranial base bone and a decrease of cerebrospinal fluid leakage as a postoperative complication of transsphenoidal surgery. HAC is a biomaterial that is recommended to be used as the primary method for reconstructing cranial base bone defects.

Correlative radiological, self-assessment and clinical analysis of evolution in instrumented dorsal and lateral fusion for degenerative lumbar spine disease. Autograft versus coralline hydroxyapatite

This prospective longitudinal randomized clinical and radiological study compared the evolution of instrumented posterolateral lumbar and lumbosacral fusion using either coralline hydroxyapatite (CH), or iliac bone graft (IBG) or both in three comparable groups, A, B and C, which included 19, 18 and 20 patients, respectively, who suffered from symptomatic degenerative lumbar spinal stenosis and underwent decompression and fusion. The patients were divided randomly according to the graft used and the side that it was applied. The spines of group A received autologous IBG bilaterally; group B, IBG on the left side and hydroxyapatite mixed with local bone and bone marrow on the right side; group C, hydroxyapatite mixed with local bone and bone marrow bilaterally. The age of the patients in the groups A, B and C was 61+/-11 years, 64+/-8 years and 58+/-8 years, respectively. The SF-36, Oswestry Disability Index (ODI), and Roland-Morris (R-M) surveys were used for subjective evaluation of the result of the surgery and the Visual Analogue Scale (VAS) for pain severity. Plain roentgenograms including anteroposterior, lateral and oblique views, and lateral plus frontal bending views of the instrumented spine and CT scan were used to evaluate the evolution of the posterolateral fusion in all groups and sides. Two independent senior orthopaedic radiologists were asked to evaluate first the evolution of the dorsolateral bony fusion 3-48 months postoperatively with the Christiansen's radiologic method, and secondly the hydroxyapatite resorption course in the spines of groups B and C. The diagnosis of solid spinal fusion was definitively confirmed with the addition of the bending views, CT scans and self-assessment scores. The intraobserver and interobserver agreement (r) for radiological fusion was 0.71 and 0.69, respectively, and 0.83 and 0.76 for evaluation of CH resorption. T(12)-S(1) lordosis and segmental angulation did not change postoperatively. There was no radiological evidence for non-union on the plain roentgenograms and CT scans. Radiological fusion was achieved 1 year postoperatively and was observed in all groups and vertebral segments. Six months postoperatively there was an obvious resorption of hydroxyapatite granules at the intertransverse intersegmental spaces in the right side of the spines of group B and both sides of group C. The resorption of hydroxyapatite was completed 1 year postoperatively. Bone bridging started in the third month postoperatively in all instrumented spines and all levels posteriorly as well as between the transverse processes in the spines of the group A and on the left side of the spines of group B where IBG was applied. SF-36, ODI, and R-M score improved postoperatively in a similar way in all groups. There was one pedicle screw breakage at the lowermost instrumented level in group A and two in group C without radiologically visible pseudarthrosis, which were considered as having non-union. Operative time and blood loss were less in the patients of group C, while donor site complaints were observed in the patients of the groups A and B only. This study showed that autologous IBG remains the "gold standard" for achieving solid posterior instrumented lumbar fusion, to which each new graft should be compared. The incorporation of coralline hydroxyapatite mixed with local bone and bone marrow needs adequate bleeding bone surface. Subsequently, hydroxyapatite was proven in this series to not be appropriate for intertransverse posterolateral fusion, because the host bone in this area is little. However, the use of hydroxyapatite over the decorticated laminae that represents a wide host area was followed by solid dorsal fusion within the expected time.

Backfill for iliac-crest donor sites: a prospective, randomized study of coralline hydroxyapatite

We report on a prospective randomized study of coralline hydroxyapatite (CH) used as backfill for iliac-crest donor sites. Autogenous iliac-crest bone graft is routinely harvested for spinal fusion. Donor-site morbidity is underappreciated; the presumption is that donor sites regenerate. In this study, we assessed the biological viability of the backfill CH (Pro OsteonTM Implant 500 Hydroxyapatite Bone Void Filler; Interpore, Irvine, Calif) and compared donor-site morbidity after harvest. Twelve patients (11 men, 1 woman) were enrolled: 5 in the backfill group and 7 in the no-backfill group. As part of routine evaluations done preoperatively and 6 weeks, 3 months, 6 months, and 1 year postoperatively, plain radiographs and computed tomography (CT) scans were used to assess bone ingrowth, and technetium bone scans were used to assess biological activity. Postoperative pain analysis was also done. Ten patients (9 men, 1 woman) completed the study. Of the 4 completers in the backfill group, 3 (75%) showed bony ingrowth on plain radiographs and CT scans at 1 year; the fourth patient showed bony ingrowth only on plain radiographs. All 4 patients showed biological activity on bone scans and reported mild pain to no pain. Of the 6 completers in the no-backfill group, 1 (17%) showed bony ingrowth on plain radiographs and CT scans. No patient showed biological activity on bone scans at 1 year. CH aids in iliac-crest healing after bone-graft harvesting by acting as a biological osteoconductive matrix. Postoperative pain at the bone-graft site is potentially reduced. More studies of larger numbers of patients are needed to assess the true long-term benefits of this material in a clinical setting.

Surface treatment of injectable strontium-containing bioactive bone cement for vertebroplasty

A novel injectable bioactive bone-bonding cement (SrHAC) composed of strontium-containing hydroxyapatite (Sr-HA) as the inorganic filler and bisphenol A diglycidylether dimethacrylate (Bis-GMA) as the organic matrix for vertebroplasty was developed previously. In this study, the Sr-HA powders were surface treated with methyl methacrylate (MMA) to improve the interface integration of the two phases. After surface treatment, the compression strength and Young's modulus, which were tested after immersion in distilled water at 37 degrees C for 24 h according to ISO 5833, were increased by 68.65 % (p <.001) and 31.02% (p <.001), respectively. The bending strength and bending stiffness of the bioactive bone cement were significantly improved by 54.44% (p <.001) and 83.90% (p <.001). In addition, the handling property of the cement was also enhanced. In vitro biomechanical testing showed that the stiffness of the fractured spine recovered to 82.5% (p <.01) of the intact condition after cementation with surface-treated SrHAC. The failure load of the spine cemented with original and MMA-treated SrHAC improved by 14.25% (p <.05) and 46.91% (p <.05) in comparison with the fractured spines. Results from this study revealed that the MMA-treated SrHAC has a better mechanical effect for orthopedic applications.

[Comparative evaluation of TNF-alpha induction in vitro and in local tissue reaction after implantation of HAP/TCP and HAP]

The aim of this work was the evaluation of biocompatibility and bioactivity of HAP/TCP as compared to HAP. This evaluation was carried out by the in vitro assessment of the induction of TNF-alpha in the rat blood after the contact with the tested HAP. The anther target was to investigate of local muscle tissue reaction of rats bones reaction of rabbits, after the implantation of tested materials. The level of TNF-alpha was estimated by biological method in the supernatants of rat blood cell cultures stimulated in vitro by tested materials. The implantation assessment was carried out on 25 rats and 15 rabbits. The muscle tissue reaction was evaluated after 2, 4, 8, 12, and 24 weeks, while the reaction of bones after 4, 12, and 26 weeks since the implantation. The level of TNF-alpha in the blood after stimulation in vitro with HAP/TCP was on the same level as control group. The implantation of HAP the level of TNF-alpha was twice as high as compared to HAP/TCP and control groups. These differences were of statically importance. The muscle tissue reaction after implantation of HAP/TCP was characterized by moderate inflammation during the early period which lead to the formation of two layer connective tissue capsule. In the capsule wall there were great cells of foreign body type and macrophages. In the cytoplasm of some the cells particles of HAP were noted, what could be regarded as the proof of its resorption. In the bone tissue surrounded HAP/TCP implants the stronger osteoconductive proprieties were observed as compared to the tissue around HAP.

Biological reactivity of zirconia-hydroxyapatite composites

Materials and devices intended for end-use applications as implants and medical devices must be evaluated to determine their biocompatibility potential in contact with physiological systems. The use of standard practices of biological testing provides a reasonable level of confidence concerning the response of a living organism to a given material or device, as well as guidance in selecting the proper procedures to be carried out for the screening of new or modified materials. This article presents results from cytotoxicity assays of cell culture, skin irritation, and acute toxicity by systemic and intracutaneous injections for powders, ceramic bodies, and extract liquids of hydroxyapatite (HA), calcia partially stabilized zirconia (ZO), and two types of zirconia-hydroxyapatite composites (Z4H6 and Z6H4) with potential for future use as orthopedic and dental implants. They indicate that these materials present potential for this type of application because they meet the requirements of the standard practices recommended for evaluating the biological reactivity of ATCC cell cultures (CCL1 NCTC clone 929 of mouse connective tissue and CCL 81 of monkey connective tissue) and animals (rabbit and mouse) with direct or indirect patient contact, or by the injection of specific extracts prepared from the material under test. In addition, studies involving short-term intramuscular and long-term implantation assays to estimate the reaction of living tissue to the composites studied, and investigations on long-term effects that these materials can cause on the cellular metabolism, are already in progress.

Supplementation of autogenous bone graft with coralline hydroxyapatite in posterior spine fusion for idiopathic adolescent scoliosis

Twenty-seven consecutive patients with adolescent idiopathic scoliosis underwent posterior spinal fusion with pediatric Texas Scottish Rite Hospital instrumentation. Coralline hydroxyapatite (Interpore, Irvine, Calif) was mixed with limited autograft from posterior iliac crest (an approximate 70/30 ratio of coralline hydroxyapatite to autograft). Patient evaluation was based on clinical and radiographic findings. On initial radiographic evaluation, a "snowstorm" appearance consistent with the exoskeleton of the coralline hydroxyapatite was observed. After two years, the fusion mass had a "marble-like" appearance with distinct decreased visibility of the disk spaces in the fusion mass. This latter stage of "marbilization correlated with solid fusion clinically. All patients achieved solid fusion at an average follow-up of 27 months. Coralline hydroxyapatite is safe, biocompatible, and effective in augmenting autogenous bone graft in the treatment of idiopathic adolescent scoliosis with posterior spinal fusion. In addition to decreased donor site morbidity, this may be invaluable in cases where there is insufficient autograft available.

[Influence of dosage on cell biocompatibility of hydroxyapatite/tricalcium phosphate]

OBJECTIVE

To investigate the influence of different dose levels of hydroxyapatite/tricalcium phosphate (HA/TCP) on the proliferation and alkaline phosphatase (ALP) activity of rabbit osteoblasts.

METHODS

Three different dose levels of HA/TCP (10%, 40%, 70%) were co-cultivated with rabbit osteoblasts respectively. The proliferation and ALP expression capacity of osteoblasts were examined with MTT method and enzyme histochemistry once every 24 hours until 5 days. Three control groups of other materials were treated and examined in the same way: rabbit osteoblasts as normal control; polyvinylchloride as positive control; titanium alloy as negative control.

RESULTS

There was remarkable time-effect relationship in the proliferation of osteoblasts. Ten percent HA/TCP did not affect osteoblasts growth while 40% HA/TCP could slow the cell growth rate down though time-effect relationship still existed. The proliferation of osteoblasts stagnated when co-cultivated with 70% HA/TCP. On the other hand, 10% HA/TCP could cause reversible damage on ALP activity of osteoblasts, whereas when the dose was 40%, and the cultivation lasted 6 days the damage was irreversible. Three different dose levels of titanium alloy (10%, 40%, 70%) had no effect on the proliferation or ALP activity of osteoblasts.

CONCLUSION

Dosage is an important factor affecting the biocompatibility evaluation of biomaterial. It suggests that dose choosing should be more specified upon each individual biomaterial. It also indicates that ALP may be a good supplementary index of the cell compatibility of material.

How does recombinant human bone morphogenetic protein-4 enhance posterior spinal fusion?

STUDY DESIGN

A rabbit posterolateral intertransverse process fusion model was used to evaluate the effect that different doses of recombinant human bone morphogenetic protein-4 delivered in a porous hydroxyapatite-tricalcium phosphate ceramic had on osteogenesis and spinal fusion.

OBJECTIVE

To study the biologic effect and threshold dose of recombinant human bone morphogenetic protein-4 in enhancing spinal fusion.

SUMMARY OF BACKGROUND DATA

Biologic manipulation for spinal fusion is an area undergoing active research. The enhancing effects of recombinant human bone morphogenetic proteins 2 and 7 on spinal fusion have been proved, and clinical trials of their application are in progress. Recombinant human bone morphogenetic protein-4 is another osteoinductive protein that has the ability to induce heterotopic bone formation, and its potential for enhancing spinal fusion has not yet been studied.

METHODS

For this study, 24 adult New Zealand white rabbits underwent single-level unilateral posterior intertransverse process spinal fusion at L5-L6. The animals were divided into four groups using different graft materials: allograft as well as hydroxyapatite-tricalcium phosphate augmented with 0, 1.25, and 5 microgram of recombinant human bone morphogenetic protein-4, respectively. The local changes were evaluated by sequential radiograph, manual palpation, histomorphology, and microradiography.

RESULTS

At week 7, ossification in the intertransverse process area ceased in groups without recombinant human bone morphogenetic protein-4, whereas active multicentric endochondral bone formation was demonstrated in groups with this growth factor. The success rate of contiguous bony bridging was found to correlate positively with the dose of recombinant human bone morphogenetic protein-4.

CONCLUSIONS

Recombinant human bone morphogenetic protein-4 effectively enhances new bone formation and accelerates fusion in the rabbit posterolateral posterior spinal fusion model. The effective dose of recombinant human bone morphogenetic protein-4 is 10 times lower than the reported dosage of recombinant human bone morphogenetic proteins 2 and 7.

Short-term evaluation of non-absorbable microgranular hydroxyapatite infiltration in the guinea pig subepidermal abdominal region

Non-absorbable microgranular hydroxyapatite was infiltrated into the subepidermal abdominal region of guinea pigs in order to assess the possibility of using this material to correct deficiencies in orbital volume. Microgranular hydroxyapatite (2.0 ml) was subepidermally infiltrated into the abdominal region of 20 guinea pigs. The animals were divided into four experimental groups of 5 animals each, which were killed 7 (G1), 15 (G2), 30 (G3) and 60 (G4) days after infiltration. The area and the largest and smallest diameters of the nodules formed by infiltration were evaluated at the site of infiltration and histological examination was performed. The mean granuloma area was similar in all groups. Histopathological examination showed that the material remained isolated from surrounding tissues by a pseudocapsule that became denser throughout the experiment. A host reaction started with young fibroblastic tissue that evolved to dense tissue until cartilaginous tissue was formed in G4, progressively advancing towards the center of the granuloma from G1 to G4. Non-absorbable microgranular hydroxyapatite is an inert material that was well tolerated by the animals studied, with maintenance of the infiltrated volume, and may perhaps be useful to fill anophthalmic cavities.

[Cytotoxicity of the strontium-substituted hydroxyapatite evaluated by MTT colorimetry]

This study was conducted to evaluate the cytotoxicity of strontium-substituted hydroxyapatite by methyl thiazolyl tetrazolium (MTT) colorimetry. We used the MTT method to assay the cytotoxicity of the strontium-substituted hydroxyapatite containing different strontium concentrations (1%, 5%, 10%, 100% Sr2+) and the pure hydroxyapatite. The results showed that the cytotoxicity scores of the different materials were grade 0 or grade 1. These led us to the conclusion that strontium-substituted hydroxyapatite has good biocompatibility.

Delayed surgery does not reduce the interface strength between the surface of a bone fracture and a self-curing injectable hydroxyapatite (Norian SRS)

The shear strength of the interface between bone and an injectable calcium phosphate bone substitute that cures to form a carbonated apatite (Norian SRS) was measured and related to the time that elapsed between injury and surgery. Eleven rabbits had a 3 mm drill hole made in the retropatellar aspect of the distal femur. After one week, the rabbits were reoperated on and the hole filled with Norian SRS after it had been cleaned gently with a sponge. During the same procedure a similar hole was burred in the opposite femur and filled with Norian SRS after a few minutes ("immediate injection"). Four other rabbits had only one side operated on with immediate injection of Norian SRS to compare with the opposite untreated side. The rabbits were killed four days after the injection of Norian SRS. The femurs were prepared and sawed perpendicularly to the burr channels to produce discs 3.5 mm thick. A push out test of the Norian SRS plug within the bone disc was done to measure the force at failure. In the immediately injected specimens the failure occurred at a mean of 28 N (range 5-57) compared with 42 N (range 25-65) in the specimens injected after a one week delay. There was no significant difference between delayed and immediate treatment (95% confidence interval -5 to 133). The histological examination showed that 9 of the 12 specimens had Norian SRS still adherent to half or more of the circumference of the hole. This indicates that the failure occurred in the Norian SRS rather than in the bone or at the interface.

[Intraperitoneal and intrathoracic administration of hydroxyapatite-carboplatin (HAp-CBDCA)]

We have investigated the efficacy of intraperitoneal or intrathoracic administration of hydroxyapatite particles (HAp) loaded carboplatin (CBDCA). HAp-CBDCA (HAp; 200 mg, CBDCA; 4 mg) was administered intraperitoneally to rats with peritoneal carcinomatosis. The area under the curve of the ascitic platinum (Pt) increased significantly with rats given HAp-CBDCA, and the omental Pt levels in the HAp-CBDCA group remained higher and longer. Additionally, the HAp-CBDCA group showed a trend toward longer survival when compared with the CBDCA alone group. In clinical use, HAp-CBDCA (HAp; 5 g, CBDCA; 150 mg) was administered intrathoracically to a patient who had undergone esophagectomy. The Pt in serum was detected until 7 days after administration of HAp-CBDCA.

Effect of in situ plaque mineral supplementation on the state of saturation of plaque fluid during sugar-induced acidogenesis

Dental plaque fluid is normally supersaturated with respect to enamel mineral but this may change to a state of undersaturation when plaque pH falls following sugar exposure, placing the adjacent enamel at risk of caries. We have determined the saturation status of the fluid in both resting and fermenting plaque following mineral supplementation. Eleven subjects abstained from oral hygiene and rinsed their mouth 3 times/d for 3 d with a placebo solution or with test solutions designed to enrich plaque with hydroxyapatite or fluorhydroxyapatite. On the morning of day 4, plaque samples were collected before and after exposure to 10% sucrose. Compared to the placebo, use of the test rinses resulted in significantly higher concentrations of Ca, P and F in plaque residue. In plaque fluid, higher post-sucrose Ca2+ free concentrations and saturation levels with respect to enamel mineral and fluorapatite were found after use of the hydroxyapatite rinse compared to the placebo, effects that probably resulted from the release of cell-bound Ca2+ as well as from the dissolution of apatite. Thus, some evidence was obtained that the test mouthrinses can counteract the fall in saturation level found when plaque is exposed briefly to sucrose. Potential long-term benefits of the test mouthrinses deserve further study.

Changes in articular synovial lining volume measured by magnetic resonance in a randomized, double-blind, controlled trial of intra-articular samarium-153 particulate hydroxyapatite for chronic knee synovitis

OBJECTIVE

Magnetic resonance techniques have recently been investigated as tools with which to monitor inflammatory joint disease. Our aim was to use a contrast-enhanced T1-weighted protocol to monitor the short-term changes in knee synovial lining volume in a double-blind, randomized, controlled trial of intra-articular samarium-153 particulate hydroxyapatite (Sm-153 PHYP).

METHODS

Twenty-four out-patients with chronic knee synovitis, from a cohort who had been recruited to a long-term clinical efficacy trial, were recruited for this study. Patients received either intra-articular Sm-153 PHYP combined with 40 mg triamcinolone hexacetonide or 40 mg intra-articular triamcinolone hexacetonide alone. Synovial lining volumes were calculated from three-dimensional T1-weighted contrast-enhanced images made before and after contrast enhancement with thresholding and pixel counting, immediately before and 3 months after treatment.

RESULTS

Paired pre- and post-treatment magnetic resonance data were obtained for 18/24 (75%) patients. There was no significant difference in mean pre-treatment synovial volume between the two treatment groups (139 vs 127 ml). A mean reduction in synovial lining volume was detected in the Sm-153 PHYP/steroid-treated group (139 to 110 ml, P = 0.07) and in the steroid-treated group (127 to 58 ml, P < 0.001). The reduction was significantly greater in the steroid-treated group (-61% vs -23%, P < 0.05).

CONCLUSIONS

Short-term changes in articular synovial lining in response to intra-articular treatment for chronic synovitis may be monitored by magnetic resonance imaging. After 3 months, a greater mean reduction in synovial lining volume had occurred in response to intra-articular steroid alone compared to combined Sm-153 PHYP/steroid injection.

The effect of locally implanted complexes of adriamycin-hydroxyapatite complexes on tumor--study of a new alternative treatment for hepatic cancer

A new targeting anticancer system was prepared by using hydroxyapatite particles (2 mm in diameter) as carrier material and adriamycin as anticancer agent. The adsorption and release properties of the complexes were assayed by fluorometry in vivo and in vitro and the curative effect on W-256 sarcoma of rat was observed. The results showed that one particle of hydroxyapatite could adsorb approximately 0.08 mg adriamycin and they can maintain a steady and slow release of adriamycin from hydroxyapatite for one month. When hydroxyapatite-adriamycin complexes were implanted into the liver of rat, liver adriamycin concentration at the implanted region was obviously higher than that achieved by injection of adriamycin solution. The locally implanted complexes obviously inhibited the growth of subcutaneous implanted tumor of rat, and increased the survival rate of rat with implanted liver tumor.

Ectopic bone formation by biphasic calcium phosphate (BCP) combined with recombinant human bone morphogenetic protein-2 (rhBMP-2)

We investigated ectopic bone formation by biphasic calcium phosphate (BCP) combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) in the rat dorsum. Under reduced pressure, rhBMP-2 was adsorbed onto BCP, which consisted of 80% beta-tricalcium phosphate and 20% hydroxyapatite uniformly distributed in granules. Twenty Wistar rats were separated into 4 groups consisting of 5 animals each dosed with 2, 10, and 50 micrograms/700 microliters of rhBMP-2 and a control group (BCP only). Pieces of the BCP-BMP complex or only BCP were implanted under the dorsal skin of the rats. Histological sections were examined three weeks later. New bone was formed in all rats given 50 micrograms doses, but not in the 2 micrograms and control groups. These results indicated that BCP combined with rhBMP-2 induced ectopic bone formation without additional carriers. Therefore, BCP granules alone can function as carriers for rhBMP-2 to induce bone formation.

Preliminary evaluation of a polyethyleneglycol-stabilized manganese-substituted hydroxylapatite as an intravascular contrast agent for MR angiography

A blood-persistent particulate paramagnetic contrast agent has been formulated via size stabilization of manganese-substituted hydroxylapatite by a polyethylene glycol (PEG) bearing a terminal diphosphonate. At high PEG surface densities (35-40 mol%), particles with mean diameter 8 +/- 2 nm were obtained. Relaxivities of autoclaved samples (at 20 MHz proton Lamor frequency) were R1 = 18.7 +/- .8 mM-1 sec-1 and R2 = 22.3 +/- .7 mM-1 sec-1. The formulation persisted in rabbit blood with a biphasic clearance profile. Half-lives (with amplitudes in parenthesis) were 4 +/- 1 minutes (55%), and 49 +/- 3 minutes (45%), respectively, for the two phases. A dose of 40 mumol Mn/kg body weight enhanced the signal from rabbit vasculature for more than 45 minutes on MR angiograms. Thus, PEG-modified MnHA particles may find use as T1 agents for MR angiography.

Clinical outcome after one year following samarium-153 particulate hydroxyapatite radiation synovectomy

The clinical outcome and tolerability following treatment with samarium-153 particulate hydroxyapatite was evaluated in patients with persistent rheumatoid knee synovitis. The clinical review of 18 patients treated with intra-articular samarium-153 particulate hydroxyapatite combined with triamcinolone hexacetonide who had failed to obtain more than 4 weeks symptom relief from a prior intra-articular glucocorticoid injection was undertaken. No unwanted effects from the treatment were observed. Symptom relief was maintained in 56% patients at 6 months and in 44% of patients at 12 months following treatment. Median duration of symptom relief was 9 months. There was a significantly higher mean baseline Ritchie Articular Index in patients relapsing within 3 months and a trend towards earlier relapse in patients with higher indices of disease activity at the time of treatment. There was a trend towards earlier relapse in patients with a poor range of knee flexion at baseline and with worse indices of intra-articular radiopharmaceutical distribution. Samarium-153 particulate hydroxyapatite knee synovectomy is well tolerated and may be an effective treatment for carefully selected patients with persistent rheumatoid knee synovitis.

[Filling up small bone defects with bone ceramics (hydroxylapatite)]

First clinical results using a bovine hydroxyapatite implant to fill up small bony defects after excision of enchondromas or cysts are reported in twelve patients. Incorporation without any problems was completed radiologically after six to eight weeks. Complications did not occur. Avoiding additional surgery harvesting cancellous bone chips at the iliac crest, the use of these bovine hydroxyapatite ceramic seems to be reasonable.

Revision, without cement, of aseptically loose, cemented total hip prostheses. Quantitative comparison of the effects of four types of medullary treatment on bone ingrowth in a canine model

A model that replicated the radiographic and histological features of aseptic loosening of the femoral component of a total hip replacement that had been done with cement was created in thirty-seven dogs. A deep wound infection developed in one dog, and that dog was excluded from the study. Revision was performed without cement in twenty-nine dogs, which were then followed for six months. The remaining seven dogs were used for histological study only. The components that were used for revision were made from Ti-6-Al-4-V, and a titanium fiber-metal porous surface had been applied to the anterior, posterior, and medial surfaces of the proximal part of the stem. The femora were revised either with no graft material applied to the osseous defect; with hydroxyapatite/beta-tricalcium phosphate placed in the defect; with application of an autologous cancellous bone graft as part of a one-stage revision; or with application of an autologous cancellous bone graft as the first part of a two-stage revision, with implantation of the component four months later. The use of an autologous bone graft led to greater and more consistent ingrowth of bone. The greatest amount of bone ingrowth was found in the group in which the procedure had been done in two stages (18 +/- 4.1 per cent), followed by the group in which the prosthesis and the graft had been inserted in a single stage (15 +/- 5.0 per cent), the group that had been treated with hydroxyapatite/beta-tricalcium phosphate (10 +/- 9.1 per cent), and the control group, in which no graft had been used (7 +/- 7.0 per cent). Notably, all of the components in the animals in which an autologous graft had been used were well fixed by bone ingrowth, while the component in two of the animals in the group in which no graft had been used in one animal in the hydroxyapatite/beta-tricalcium phosphate group had only fibrous-tissue ingrowth. In contrast to the findings with respect to bone ingrowth, there was more medullary bone adjacent to the lateral aspect of the implant in the groups in which hydroxyapatite/beta-tricalcium phosphate or no graft had been inserted than in the groups that had had an autologous graft.(ABSTRACT TRUNCATED AT 400 WORDS)

Implantation treatment method of slow release anticancer doxorubicin containing hydroxyapatite (DOX-HAP) complex. A basic study of a new treatment for hepatic cancer

We performed an experimental study on slow releasing anticancer drug implantation treatment as a new therapy for hepatocellular carcinoma. Hydroxyapatite (HAP) was chosen for the carrier material and doxorubicin hydrochloride (DOX) for anticancer agent. DOX-HAP was produced by adsorbing DOX to porous HAP particles of 1375 +/- 125 microns diameter using the freeze drying method. In vitro experiments showed slow release of the drug resulting in the steady release of DOX from HAP for 1 month duration. In healthy white rabbits with DOX-HAP implantation in the liver, serum DOX was not detectable, and DOX release rate was stable at the implanted region after 7, 14, and 21 days. When DOX-HAP (DOX; 100 mg kg-1) was administered to mice with sarcoma 180, an improved survival rate was observed without acute toxicity. We also found that VX2 liver tumour growth on white rabbit was inhibited by implantation of DOX-HAP, without acute toxicity. We hope that DOX-HAP implantation therapy will open up new avenues for the treatment of hepatoma.

[Experimental study on intratumoral injection with hydroxyapatite bioceramics and adriamycin in implanted hepatoma in mice]

Hydroxyapatite (HA) bioceramics is a biomaterial used in orthopedic area. We observed its anticancer effect in experimental hepatoma-22 (H22) in mice. BALB/c mice implanted with H22 were grouped into I, II, III and IV. Intratumoral injections were given as follows: (I) HA 0.1 g and ADM 0.1 mg n = 28; (II) HA 0.1 g n = 16; (III) ADM 0.1 mg n = 16; (IV) untreated n = 20. The tumor regression rates of the groups I, II and III were 65.9%, 41.9% and 51.1%, respectively. The mean survivals of groups I, II, III and IV were 32, 22, 26 and 18 days. Six mice of group I were alive more than 50 days before being killed, in which 4 tumor samples showed that no residual tumor cells could be seen under microscope. The possible mechanism of HA anti-cancer action is: (1) the dissolved matter of HA, glycoprotein and microfibril around the tumor cells may disturb the metabolism of cancer; (2) fibrocalcific process restricts the tumor growth; (3) immunoenhancement action (4) as a drug-release system HA is a hopeful agent of intratumoral injection for treatment of cancer.

Experimental implant-related osteomyelitis treated by antibiotic-calcium hydroxyapatite ceramic composites

The efficacy of locally implanted antibiotic-calcium hydroxyapatite ceramic composites was investigated for the treatment of experimentally produced, implant-related osteomyelitis in rats. High concentrations of antibiotics were detected at the site of infection and bacteria were eradicated without removal of the metal implants. Parenteral antibiotics and surgical debridement, alone or in combination with antibiotic-impregnated acrylic bone cement, all failed to eradicate the infections.

Hydroxylapatite-coated hip implants. Multicenter three-year clinical and roentgenographic results

The application of a thin coating of hydroxylapatite to total hip implants has provided the opportunity to realize stable fixation of a press-fit prosthesis without a porous coating or an intervening fibrous tissue layer. This series consists of 436 total hip arthroplasties, of which 320 cases have a minimum two-year follow-up period and 142 cases have a minimum three-year follow-up period. The femoral prosthesis used was a roughened titanium alloy with a 50-microns surface treatment of hydroxylapatite applied to the proximal one third. The acetabular components implanted included porous-coated implants (132), hydroxylapatite-coated acetabular shells of varying geometries (285), and bipolar implants (16). Analysis of the clinical results demonstrates a mean Harris Hip Score of 93 at six-months postarthroplasty, 95 at one and two years, and 96 at three years. At the three-year follow-up evaluation, 4.2% of patients complained of mild to moderate pain in the operative limb, whereas only 2.2% at two years and 1.4% at three years complained of activity-related thigh pain. The femoral mechanical loosening rate representing stems revised for aseptic loosening (two) plus roentgenographically unstable stems (zero) is 0.46%. Three hydroxylapatite-coated acetabular cups (1%) have shown measurable migration at two years, but none have been revised for aseptic loosening. The roentgenographic evaluation provides evidence for excellent proximal femoral fixation with distal stress transfer. Radiolucencies typically occur around the uncoated distal tip of the femoral stem (74%), but rarely in the proximal hydroxylapatite-coated anterior (3%) and lateral (2%) zones. Femoral cancellous condensation characteristically is seen at the transition zone of hydroxylapatite coated-to-uncoated stems (86%), whereas up to 32% of cases show cortical hypertrophy at the medial distal stem. These roentgenographic changes are progressive from one through three years postoperatively.

The effect of age on the inflammatory response to arthritis-associated crystals

The effect of age on the inflammatory response to urate and hydroxyapatite crystals was examined using both in vivo (intradermal skin testing) and in vitro (neutrophil death following incubation with urate crystals) methods. No significant difference in crystal-induced inflammation was found between young (< 25 years) and elderly (> 75 years) subjects and there was no correlation between the in vivo and in vitro tests. There was good correlation (0.63, p < 0.001) between the intradermal responses to urate and hydroxyapatite, suggesting that subjects, regardless of their age, are consistent in their response to these two types of arthritis-associated crystal. Advanced age does not lead to a major alteration in the inflammatory response to arthritis-associated crystals.

[Fundamental study on hyperthermic chemotherapy using adriamycin-loaded hydroxyapatite]

We developed a porous hydroxyapatite ceramic (HAP) incorporating adriamycin (ADM), that is, ADM-HAP as a new delivery system (DDS) to release ADM gradually. We also researched the possibility of hyperthermic chemotherapy using ADM-HAP by in vitro and in vivo experiments. As for in vitro experiments, we implanted HAPs into uniform Agar-Phantom, and observed thermal distribution generated by Thermotron-RF 8 using thermography. Then we found the hot spot that the edge temperature of HAPs always at the range of 0.5-0.7 degrees C than in the other regions. On the other hand, slow constant release (1%) of ADM from ADM-HAP in PBS was recognized for 24 hrs up to 30 days. When the incubating temperature was shifted up to 42.5 degrees C or 44 degrees C from 37 degrees C, the quantity released over 24 hrs increased about 1.1-fold or 1.3-1.4-fold of the cases at 37 degrees C, respectively. In the in vivo experiment, we inoculated Sarcoma 180 cells in the leg of ddY-mice, and measured the tumor growing times by the treatment of hyperthermia+ADM (whole body), hyperthermia+ADM (tumor region) or hyperthermia+ADM-HAP (tumor region). Then we found that the effect of hyperthermia with ADM-HAP inhibited synergistically the tumor growth as compared with hyperthermia with ADM. Consequently, we succeeded in tumor growth inhibition by increasing the temperature and by limiting ADM release to only a target region using hyperthermia with ADM-HAP.

Experimental hydroxyapatite cement cranioplasty

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.

[Risk of osteoporosis in long-term heparin therapy of thromboembolic diseases in pregnancy: attempted prevention with ossein-hydroxyapatite]

Generalized idiopathic osteoporosis and transient osteoporosis of the hip are both rare complications of pregnancy. More frequently, long-term heparin administration to treat deep thrombosis in the legs or pelvis may lead to substantial decreases in bone mass and consequently increased risk of osteoporosis. Therapeutic studies with the aim to counteract the osteoporosis inducing effect of heparins, have not been published to date. In the special situation of pregnancy, most medications used for osteoporosis are contraindicated. In our open randomised study, 9 women on heparin-treatment received daily 6.46 g of the bone preparation OHC (ossein-hydroxyapatite-compound) over a period of 6 months and were compared to 11 women without bone protective treatment. In the OHC-group, good compliance was observed with no side effects and reduced back pain. Bone mass did not change significantly, whilst it dropped significantly statistically in the controls.

Effect of a two-solution fluoride mouthrinse on remineralization of enamel lesions in vitro

A previous study showed that a two-solution fluoride (F) rinse deposited significantly more loosely-bound F on the tooth surface than did a sodium fluoride (NaF) rinse with the same F concentration (12 mmol/L). In the present study, this experimental rinse was evaluated for its ability to cause remineralization of enamel lesions in an in vitro pH-cycling model. Caries-like lesions were formed in the enamel of extracted human molars by means of a pH 4 demineralizing solution. Fifty-one approximately 120-microns-thick sections containing lesions were randomly divided into (1) control, (2) NaF rinse, and (3) two-solution F rinse groups. With the cut surfaces protected, the control samples were immersed in a pH 7 remineralizing solution for 12 days, and twice daily the sections were also exposed to a pH 4 demineralizing solution for 30 min. Samples in the NaF group received an additional one-minute rinse with a NaF (12 mmol/L) solution twice daily. Samples in the two-solution rinse group received the rinse treatment with a 12 mmol/L F solution prepared by combination of a Na2SiF6 and phosphate-containing solution with a calcium solution just before use. The mineral contents of the lesions were assessed by quantitative microradiography. The results showed that (1) no significant de- or remineralization was detected in the controls; (2) a 46% decrease in mineral loss (delta Z) of the lesion was produced by the NaF rinses; and (3) a 94% decrease in delta Z and a 20-microns-thick, mineral-dense surface-coating were produced by the two-solution F rinse treatment.

Hydroxyapatite cement based drug delivery systems: drug release in vitro

A novel approach using a self-setting hydroxyapatite (HAP) cement as a skeletal drug delivery system has been proposed to solve the problem of delivering drugs to skeletal tissue at high local concentrations for desirable therapeutic effects. Hydroxyapatite cements loaded with antibiotics can be formed in situ and can be used as bonding materials between bone and prostheses as well as for drug release devices. The cement also possesses sufficient mechanical strength to be a potential bone grafting material. Using cephalexin and norfloxacin as model drugs, the continuous in vitro release profiles of these compounds from 0.9-4.8% by weight loaded cement pellets were observed. These drug release patterns correlated well with the Higuchi model. This hydroxyapatite cement drug delivery system can be applied in the treatment of osteomyelitis and infected compound fractures.

Tissue reaction to collagen-coated porous hydroxyapatite

To give tenacity to high porosity (80%-90%) hydroxyapatite (HA) and to make a stronger bone substitute, a collagen-coated porous HA (C-HA) was prepared, and its compressive strength was examined. By implanting C-HA into the femoral condyle of adult rabbits, the capacity for new bone formation and foreign-body reactivity were quantitatively compared with those of HA alone. The compressive strength of C-HA was 4.3 times greater than HA. At four weeks after implantation, the mean areal ratio of the newly formed bone in the C-HA block in each rabbit was 9.9%, which was somewhat less than the 13.7% in the HA block; the mean number of multinucleated giant cells (MGC) per visual field at x25 in the C-HA-implanted specimens in each rabbit was 14.4, significantly larger than the 6.1 in the HA specimens. However, 12 weeks after C-HA implantation, the areal ratio of new bone increased to 32.7%, the number of MGC decreased to 9.4, and the differences compared to the values in HA cases, 31.5% and 6.8, disappeared. These results showed that C-HA is mechanically stronger than HA and that there is no difference between HA and C-HA in capacity for new bone formation or foreign-body reaction.

[Tympanoplasty with mastoid obliteration using hydroxyapatite granules for aural cholesteatoma--a clinical and experimental study]

Hydroxyapatite granules were employed for mastoid obliteration in cases of aural cholesteatoma. After eradicating a cholesteatoma by the canal-down technique, the canal wall was reconstructed with cortical bone chips, and the mastoid cavity was obliterated with hydroxyapatite granules. Tympanoplasty by this technique was performed on 48 ears with aural cholesteatoma. There was no recurrence of cholesteatoma during the follow-up period of two years after surgery. One case of residual cholesteatoma was found in the mesotympanum. There were two cases in which the hydroxyapatite granules became exposed through the posterior canal skin. An air-bone gap of less than 20 dB was achieved in 73% of all the patients. Experimental studies in guinea pigs have demonstrated that hydroxyapatite granules do not undergo morphological changes in and are tightly interdigitated with newly formed bone tissue growing from bulla bone one year after hydroxyapatite implantation in the temporal bullae. The newly-formed bone showed incomplete osteon structures. Excellent biocompatibility and bone adaptability of hydroxyapatite granules were demonstrated experimentally. It is concluded that tympanoplasty with mastoid obliteration using hydroxyapatite is safe and useful for avoiding mastoid cavity problems and for preventing the recurrence of cholesteatoma.

Autogeneic bone marrow and porous biphasic calcium phosphate ceramic for segmental bone defects in the canine ulna

The purpose of this study was to evaluate a porous biphasic hydroxyapatite-calcium phosphate ceramic as a modifier and extender of an autogeneic marrow graft for filling a 2.5-cm segmental bony defect. Twenty adult mongrel dogs were surgically treated to create diaphyseal defects in the left ulnae. The defects were (1) filled with autogeneic bone marrow mixed with granular hydroxyapatite-tricalcium phosphate ceramic (granular ceramic); (2) grafted with a solid block of ceramic soaked in autogeneic bone marrow (block ceramic); (3) received no graft (no implant); or (4) were grafted with autogeneic bone marrow alone (bone marrow). All animals were followed clinically and roentgenographically for 24 weeks and then killed. Repair of diaphyseal defects with the block ceramic led to three solid unions and three fibrous unions; with the granular ceramic implants and marrow, the defects of five dogs formed solid unions, and one progressed to a fibrous union. Defects in all five dogs grafted with autogeneic bone marrow united. The three dogs with no implant formed nonunions. Histology showed normal marrow and only a light immune reaction. Complete bridging of the defect in the dogs treated with the granular ceramic occurred significantly earlier than bridging in the dogs grafted with bone marrow alone. Histomorphometry, performed on the block ceramic implants indicated active resorption of ceramic. Clinically, addition of ceramic to a marrow graft improved the handling characteristics of the graft material and accelerated healing according to roentgenographic evaluation.

[Application of a slow release system of anti-cancer drug retained in calcium hydroxyapatite ceramic against experimental bone and soft tissue sarcoma]

Cis-platinum enclosed into porous calcium hydroxyapatite ceramics (CDDP-CHA) has already been reported to be an excellent slow releasing drug preparation in vivo and in vitro study. In this paper, CDDP-CHA tried to apply for experimental bone and soft tissue sarcoma. When CDDP-CHA were implanted into solid tumors (Dunn osteosarcoma cells) transplanted subcutaneously in mice, high concentration of CDDP was found and a prolonged retention of the drug in the tumor as same pattern as in normal muscle. In contrast, CDDP concentration in other organs such as liver, kidney were significantly lower than in the tumor. Tumor growth was markedly inhibited at 30 days after CDDP-CHA implantation into the tumor compared to that after intraperitoneal administration. CDDP-CHA showed a similar effect to experimental bone tumor (mammary carcinoma) as that of soft tissue tumor. These result suggests that this delivery system will be able to apply clinically for bone and soft tissue sarcoma.

Works in progress #6. Total hip arthroplasty using a hydroxyapatite-coated acetabular and femoral component

The development of alternative methods of implant fixation in primary and revision total hip arthroplasty is ongoing. Porous-coated implants abound; however, concerns surrounding their use still exist. Hydroxyapatite is a calcium phosphate ceramic, which has demonstrated properties in animal studies that make it an attractive alternative for implant fixation. We describe the early clinical and roentgenographic results of a prospective study that utilized a hydroxyapatite-coated stem and cup in 52 patients (58 hips). The average follow-up was 10.4 months (minimum, six months). At one year, 96.2% of the hips had no or slight pain, 95.1% could ambulate with no external support, 82.9% could ambulate unlimited distances, and 87.8% could walk without a limp. The roentgenographic analysis of the hydroxyapatite-coated stems (58) and cups (17) at one year revealed no radiolucencies or radiodense lines adjacent to the hydroxyapatite-coated portion of the prosthesis. None of these stems or cups migrated. We believe that these hydroxyapatite-coated components will provide rapid and enhanced prosthetic fixation and are optimistic that they will help to achieve an excellent clinical result.

A new osteoconductive resorbable hydroxylapatite graft material that restores bony defects with viable bone

The reconstruction and repair of a large mandibular bony defect following an extraction was accomplished using resorbable hydroxylapatite OsteoGen (HA RESORB). The complete repair of the defect and alveolar architecture with dense regenerated bone was achieved prior to the surgical insertion of an endosseous titanium implant. The implant was used for additional support for a long span fixed prosthesis. Histological studies of harvested bone core specimens of the resorbable hydroxylapatite grafts at four months and 14 months are compared and discussed in this report.

Use of a prefabricated splint for segmental augmentation of the mandibular alveolar ridge with hydroxyapatite

Hydroxyapatite is a biocompatible material for augmentation of edentulous ridges to improve patient comfort and denture stability. The problems associated with hydroxyapatite are generally related to the amount of material introduced and the site of implantation. This article describes the use of a prefabricated splint that permits localization of the implant material to selected sites of the mandible and restricts the amount of material used. Fabrication of this splint under the guidance of the prosthodontist and oral surgeon permits the most effective use of this technique.