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PubMed1984

Otosclerosis and otospongiosis: clinical and histological comparisons.

The simultaneous occurrence of otosclerosis and otospongiosis in the same lesion is well documented. The logical sequence of events would seem to be softening and destruction of the bone by the otospongiotic lesion, which is subsequently converted to otosclerosis. Examination of 46 temporal bones has led us to further classify the lesion as: 1. an active lesion, both otospongiotic and otosclerotic, 2. an inactive lesion, also both otosclerotic and otospongiotic, or 3. a fibrous lesion. Hyalinization of the spiral ligament only occurs adjacent to active otospongiotic or very large otosclerotic lesions. If the lesion adjacent to the spiral ligament is inactive, there is no hyalinization. It seems illogical that a hyalinized spiral ligament will return to normal when the lesion changes from active otospongiosis to inactive otosclerosis. Otospongiotic and otosclerotic lesions are found side by side at the periphery of lesions, and both are adjacent to normal bone. These findings have implications concerning the mode of action of sodium fluoride and other medications that are under evaluation for the control of the sensorineural hearing loss due to otosclerosis.

Aged↗
PubMed2000

Alveolar bone response to submerged bisphosphonate-complexed hydroxyapatite implants.

BACKGROUND: In most studies using submerged hydroxyapatite implants, maintenance of alveolar bone after tooth extraction was attempted with plain hydroxyapatite materials. However, clinical results have shown that hydroxyapatite may require biological modification with a bone resorption-inhibiting agent which may be beneficial for maintenance of alveolar bone. We conducted experimental and clinical studies to evaluate the effect of highly bisphosphonate-complexed hydroxyapatite implants on osteoconduction and repair in alveolar bone. METHODS: Porous hydroxyapatite implants were pre-incubated in 10(-2)M bisphosphonate solutions at pH 3.49. The implants had a diameter of 2.1 mm and a height of 2 mm and adsorbed 115 microg bisphosphonate. Five goats were implanted with 4 plain hydroxyapatite implants on each side of the mandible in root extraction sockets for the precision analysis of dual x-ray absorptiometry (DEXA) measurements. Ten goats were implanted with 4 bisphosphonate/hydroxyapatite implants on one side of the mandible and 4 plain hydroxyapatite implants on the opposite mandible. In a clinical study, 23 bisphosphonate/hydroxyapatite implants were placed in periodontally destroyed tooth root sockets and followed up during one year. RESULTS: The range for the bone mineral density (BMD) measurement errors for goat histologic sections was 0.48% to 1.03%. There were large differences in peri-implant BMDs in the left and right mandible of the same goat, irrespective as to whether hydroxyapatite or bisphosphonate/hydroxyapatite implants were present. This was due to local anatomical differences typical of alveolar bone. These differences were not significant. Histologically, all bisphosphonate/hydroxyapatite as well as hydroxyapatite controls appeared to be fully integrated and effective as bone replacement material in goat alveolar bone. They exhibited vascularization and osteoconduction of alveolar bone growth along and inside their porous structure. In patients peri-implant healing was clinically and radiographically comparable to plain hydroxyapatite implants. All implants were retained and no dehiscences developed. Radiographically, peri-implant radiolucencies disappeared and alveolar bone was deposited in close proximity to the implants. CONCLUSIONS: This study contributes to the understanding of the biological properties of hydroxyapatite implants as carriers for the bone-modulating agent bisphosphonate. Our study suggests that normal osteoconduction and repair occurred in alveolar bone around the highly bisphosphonate-complexed hydroxyapatite implants.

Absorptiometry, Photon↗
PubMed1995

The history and development of the implantable hearing aid.

Implantable hearing aids have an interesting and colorful history. These devices have usually been investigational, but this has changed. Currently, several implantable devices are available for ongoing clinical trials in humans. They have promise in providing improved hearing in certain cases of conductive, mixed, and sensorineural hearing loss.

Bone Conduction↗
PubMed2005

Osteogenic potentials with joint-loading modality.

Osteogenic potentials with a novel joint-loading modality were examined, using mouse ulnae as a model system. Load-induced deformation of rigid bone is known to generate interstitial fluid flow and stimulate osteogenesis. However, in most of the previous studies, loads were applied to cortical bone. In the current study, we addressed the question of whether deformation of the epiphysis underneath the joint would enhance bone formation in the epiphysis and the diaphysis. In order to answer the question, we applied lateral loads to a mouse elbow and conducted a bone histomorphometric analysis, as well as measurements of strains and streaming potentials. Compared to the no-loading control, the histomorphometric results showed that 0.5-N loads, applied to the elbow at 2 Hz for 3 min/day for 3 consecutive days, increased the mineralizing surface (two- to threefold), the rate of mineral apposition (three- to fivefold), and the rate of bone formation (six- to eightfold) in the ulna. Strain measurements indicated that strains of around 30 microstrain, induced with the joint-loading modality, were under the minimum effective strain of around 1000 microstrain, which is considered necessary to achieve strain-driven bone formation. To evaluate the induction of fluid flow with the joint-loading modality, streaming potentials were measured in separate experiments, using mouse femurs ex vivo. We found that the streaming potentials correlated to the magnitude of the load applied to the epiphysis (r(2) = 0.92), as well as the flow speed in the medullary cavity (r(2) = 0.93). Taken together, the findings of the current study support the idea of joint-loading driven osteogenesis, through a mechanism that involves the induction of fluid flow in cortical bone.

Animals↗
PubMed2002

Tensile adhesion of type I collagen to titanium alloy and calcium phosphate coated surfaces with different roughness values.

The purpose of total joint arthroplasty is to reduce pain and restore function. Its success depends on the formation of a new bone that stabilizes the prosthesis. The proposed solution for this important problem is to have bio-coated implant surfaces which are more conductive to bone growth. Additionally, collagen has long been used as a matrix for medical applications, because of its biocompatibility and adaptability. In this study, a test method for measuring the tensile adhesion strength of collagen to titanium alloy and calcium phosphate coated surfaces with different roughness values was developed, in order to evaluate how well the collagen adheres to the metallic and bio-coated surfaces. A precision motion system was used to stretch gels that were adherent to the plate surfaces. The tests were done in DMEM solution. The adhesive strength between the collagen gel and plate was significantly higher for calcium phosphate coated surfaces. Adhesive strength was highest in the sample with the highest roughness value.

Adsorption↗
PubMed1976

Ossicular discontinuity.

Because of the numerous and varied surgical approaches to ear pathology devised and expanded in the past two decades, we are destined to be confronted with increasingly frequent cases of ossicular defects behind an intact eardrum. Using a technique which is the converse of the established "patch" test a simple office procedure is described which may help establish the diagnosis of ossicular discontinuity in the adult with an intact eardrum. An audiogram is obtained and then a myringotomy performed with insertion of a large ventilation tube. A second audiogram is then done. A rise in the air conduction level, in the absence of fluid, is suggestive of ossicular discontinuity.

Audiometry↗
PubMed2002

Alloying of hydroxyapatite onto Ti6Al-4V by high power laser irradiation.

In the biomedical field, the synthetic hydroxyapatite [Ca(10)(PO)(4)(OH)(2)], with similarity to the inorganic component of bone but brittle, has been considered as the appropriate coating on stronger implant materials, such as metallic implants, for presenting a surface which is conductive to bone formation. Many industrial and laboratory techniques were developed to apply hydroxyapatite onto metallic substrates, such as electrophoretic deposition, ion sputtering, hot isostatic pressing, pulsed laser deposition and the only widely used method commercially available: plasma spraying. This work presents a new approach on how to bind calcium phosphate (CaP) to the Ti alloy with a well-known technique in the metallurgical field: laser surface alloying, in order to overcome the drawbacks of plasma spraying. The analysis of the results obtained and the description of the phenomena that take place in the coating process will complete this explorative study.

Journal Article↗
PubMedDate not supplied

Dental implants placed in extraction sites implanted with bioactive glass: human histology and clinical outcome.

PURPOSE: To evaluate the clinical outcome of implants placed into sites grafted with bioactive glass. MATERIALS AND METHODS: Seventeen consecutively treated patients were referred to a private specialist surgical practice for the repair of dentoalveolar defects, and/or ridge maintenance at the site of extraction sockets, prior to implantation. Bioactive glass available in 1 of 2 forms was utilized as an alloplastic grafting material. Bone cores were trephined out at the time of implantation and processed and examined to evaluate the tissue response under the light microscope. Implant mobility, marginal bone levels, and soft tissue health were all evaluated over a 2- to 3-year follow-up period to determine treatment success. RESULTS: A total of 40 Astra Tech dental implants were placed. The overall success rate at the end of the study was 88.6% for implants that were in function for a mean period of 29.2 months (22 to 24 months). One patient with 5 successful implants died at 18 months after functional loading. At that time the cumulative success rate was 90%. Another patient who was diagnosed with cancer of the large bowel lost 3 implants. If this patient were excluded from the data, the cumulative success rate increases to 96.8%. Mean marginal bone loss measured 0.5 mm mesially and 0.4 mm distally over a maximum follow-up of 36 months. Human histology demonstrated that connective tissue was seen to exist without any inflammatory response, for up to 6 months. Increasing evidence of bone formation was seen in direct relation to the bioactive glass material beyond this time frame. DISCUSSION: The need to repair and augment dentoalveolar defects necessitates the use of autogenous bone or a substitute that may be seen to avoid the additional morbidity of a donor site procedure and without risk of cross infection. The use of bioactive glass has been proposed as a viable bone substitute. The current study draws attention to the long healing time required to achieve even a small amount of new bone incorporation into the graft, as seen histologically. However, the high rate of osseointegration and continued medium-term function of implants placed into these grafted sites would indicate that the use of bioactive glass does not prohibit osseointegration. However, it is likely that the initial integration will have derived from those areas in contact with native bone. CONCLUSION: Implants will survive for up to 3 years in sites grafted with bioactive glass, even when such grafts appear to only slowly conduct new bone growth.

Adult↗
PubMed1981

Mechano-electrical properties of bone.

Bone has been shown to exhibit ferro-electric properties. The relationship between applied electric field and polarization shows a hysteresis character typical of this type of material. This implies a domain structure for the permanent dipoles present in bone. Attempts to demonstrate semi-conductor properties were unsuccessful although a change of electrical resistance with applied tensile strain was demonstrated. No effect on conductivity of bone with change of pH of the fluid in which it was immersed was shown and hence no confirmation of streaming potential effects was obtained.

Biomechanical Phenomena↗
PubMedDate not supplied

Errors between two- and three-dimensional thermal model predictions of hyperthermia treatments.

A simulation program to study the three-dimensional temperature distributions produced by hyperthermia in anatomically realistic inhomogenous tissue models has been developed using the bioheat transfer equation. The anatomical data for the inhomogeneous tissues of the human body are entered on a digitizing tablet from serial computed tomography (CT) scans. Power deposition patterns from various heating modalities must be calculated independently. The program has been used to comparatively evaluate two- and three-dimensional simulations in a series of parametric calculations based on a simple inhomogeneous tissue model for uniform power deposition. The conclusions are that two-dimensional simulations always lead to significant errors at the ends of tumors (up to tens of degrees). However, they can give valid results for the central region of large tumors, but only with tumor blood perfusions greater than approximately 1 kg/m3/s. These conclusions from the geometrically simple model are substantiated by the results obtained using the full three-dimensional model for actual patient anatomical simulations. In summary, three-dimensional simulations will be necessary for accurate patient treatment planning. The effect of the thermal conductivity, used in the models, on the temperature field has also been studied. The results show that using any thermal conductivity value in the range of 0.4 to 0.6 W/m/degrees C sufficiently characterizes most soft tissues, especially in the presence of high blood perfusion. However, bone (thermal conductivity of 1.16 W/m/degrees C) and fat (thermal conductivity of 0.2 W/m/degrees C) do not fit this generalization and significant errors result if soft tissue values are used.

Blood Circulation↗
PubMedDate not supplied

Reconstructive procedures with endosseous implants in grafted bone: a review of the literature.

A review of the literature, provided by a MEDLINE search from 1976 through April 1994 and review of selected journals published from April 1994 to November 1994, relative to reconstructive procedures of the mandible and maxilla in which endosseous implants have been placed in grafted bone was conducted. This review revealed that 591 patients received 733 grafts in which 2,315 implants were placed. The types of grafts reported were block, autogenous bone (nonvascularized or vascularized), and particulate with a variety of materials. Results of these grafts are presented with the different implant systems utilized. Wound dehiscence seems to have the most deleterious effect on implant survival rate.

Bone Transplantation↗
PubMed2005

Reduced bone mineral density in male Severe Acute Respiratory Syndrome (SARS) patients in Hong Kong.

During the Severe Acute Respiratory Syndrome (SARS) outbreak in Hong Kong in 2003, patients were treated with very high doses of corticosteroid and ribavirin. The detrimental effects of such treatment on the bone mineral density (BMD) of SARS patients are unknown. To compare the BMD of SARS patients with normal range data, a cross-sectional survey was conducted. The bone mineral density of 224 patients with SARS, who were treated with an average of 2753 mg (SD = 2152 mg) prednisolone and 29,344 mg (SD = 15,849 mg) of ribavirin was compared to normal data. Six percent of men had a hip BMD Z score of < or =-2 (P = 0.057 for testing the hypothesis that >2.5% of subjects should have a Z score of < or =-2). Moreover, there was a negative association (r = -0.25, P = 0.023) between the duration of steroid therapy and BMD in men. We conclude that male SARS patients had lower BMD at the hip than normal controls, and this could be attributed to prolonged steroid therapy.

Adult↗
PubMed2004

Effects of ovulatory and egg laying cycle on bone mineral density and content of live White Leghorns as assessed by dual-energy X-ray absorptiometry.

Dual-energy X-ray absorptiometry has been validated in our laboratory as a noninvasive tool to assess skeletal integrity in live birds. The first objective of the current study was to determine if there were detectable changes in bone mineral density (BMD) and bone mineral content (BMC) while an egg was being formed in the oviduct. Implications from this experiment would define the time of day scans should be conducted for future experiments. Densitometric scans were conducted on the tibia and humerus of live hens undergoing active egg formation when hens were 0, 5, 15, and 20 h postoviposition at 24, 30, and 40 wk of age. No detectable changes in either the BMD or BMC of the tibia and humerus were observed as the egg was being formed in the reproductive tract at any age measured. These results suggest that densitometric scans may be conducted on bones in live birds at any time during the day, irrespective of the stage of egg formation. The second objective was to monitor the change and degree of variation in skeletal integrity of live birds during the first cycle of egg laying. The humerus and tibia of White Leghorns were scanned repeatedly at 10-wk intervals from 15 to 65 wk of age. The BMD of the humerus increased from 15 to 65 wk of age, whereas the BMD and BMC of the tibia increased from 15 to 55 wk of age, resulting in a bone-by-age interaction (P < 0.001). The BMC of the humerus did not change from 15 to 55 wk of age but increased at 65 wk of age. Age-related increases in BMD and BMC may be due to the inability of dual energy X-ray absorptiometry to distinguish medullary from structural bone. The CV for BMD and BMC of egg-type chickens was greater than 10% after 25 wk of age, which suggested that bone densitometry could be used as an indicator tool in genetic selection with a potential for improving skeletal integrity of birds.

Absorptiometry, Photon↗
PubMed2006

Laser interferometry measurements of middle ear fluid and pressure effects on sound transmission.

An otitis media with effusion model in human temporal bones with two laser vibrometers was created in this study. By measuring the displacement of the stapes from the medial side of the footplate, the transfer function of the middle ear, which is defined as the displacement transmission ratio (DTR) of the tympanic membrane to footplate, was derived under different middle ear pressure and fluid in the cavity with a correction factor for cochlear load. The results suggest that the DTR increases with increasing frequency up to 4k Hz when the middle ear pressure was changing from 0 to 20 or -20 cm H20 (e.g., +/-196 daPa) and fluid level was increasing from 0 to a full middle ear cavity. The positive and negative pressures show different effects on the DTR. The effect of fluid on DTR varies between three frequency ranges: f < 1k, between 1k and 4k, and f > 4k Hz. These findings show how the efficiency of the middle ear system for sound transmission changes during the presence of fluid in the cavity and variations of middle ear pressure.

Bone Conduction↗