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Biomedical subjects

Jan Hall

Publications and source records attributed to Jan Hall.

17 recordsLinked to original sources
PubMed2006

The critical-size supraalveolar peri-implant defect model: characteristics and use.

OBJECTIVE: Novel implant technologies and reconstructive therapies for alveolar augmentation require pre-clinical evaluation to estimate their biologic potential, efficacy, and safety before clinical application. The objective of this report is to present characteristics and use of the critical-size, supraalveolar, peri-implant defect model. METHODS: Bilateral extraction of the mandibular premolars was performed in 12 Hound Labrador mongrel dogs following horizontal surgical cut-down of the alveolar ridge approximating 6 mm. Each jaw quadrant received three custom-produced TiUnite, phi 4.0 x 10 mm threaded implants placed into osteotomies prepared into the extraction sites of the third and fourth premolars. The implants exhibited a reference notch 5 mm from the implant platform to facilitate surgical placement leaving 5 mm of the implant in a supraalveolar position, and to serve as a reference point in the radiographic, histologic and histometric analysis. The implants were submerged under the mucoperiosteal flaps for primary intention healing. Fluorescent bone markers were administered at weeks 3 and 4 post-surgery, and pre-euthanasia. The animals were euthanized following an 8-week healing interval when block biopsies were collected for analysis. RESULTS: Healing was generally uneventful. The radiographic and histometric evaluations demonstrate the limited osteogenic potential of this defect model. Whereas lingual peri-implant sites exhibited a mean (+/-SE) bone gain of 0.4+/-0.1 mm, resorption of the buccal crestal plate resulted in a mean bone loss of 0.4+/-0.2 mm for an overall osteogenic potential following sham-surgery averaging 0.0+/-0.1 mm. Overall bone density and bone-implant contact in the contiguous resident bone averaged 79.1+/-1.1% and 76.9+/-2.3%, respectively. CONCLUSION: The results suggest that the critical-size, supraalveolar, peri-implant defect model appears a rigorous tool in the evaluation of candidate technologies for alveolar reconstruction and osseointegration of endosseous oral implants. Limited innate osteogenic potential allows critical evaluation of osteogenic, osteoconductive, or osteoinductive technologies in a challenging clinical setting.

Alveolar Bone Loss↗
PubMed2006

A comparison of three different methods to determine arterial compliance in the elderly: the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study.

BACKGROUND: Several different techniques to evaluate arterial compliance have been described but have not been simultaneously tested in a large-scale, population-based setting. This study aimed to evaluate the feasibility and relation to cardiac risk of three of these techniques in the Prospective Study of the Vasculature in Uppsala Seniors (PIVUS) study. METHODS AND RESULTS: In the population-based PIVUS study (1016 participants aged 70), assessment of arterial distensibility by ultrasound in the carotid artery, by pulse wave analysis (augmentation index) and the stroke volume to pulse pressure ratio by echocardiography were successfully employed in 86, 92, 91 and 77% of the sample, respectively. All three indices of arterial compliance were inter-related (r = 0.19-0.34, P < 0.0001 for all). Although all three indices were significantly related to the Framingham risk score (r = 0.12-0.32, P = 0.0005-0.0001), only carotid artery distensibility and the stroke volume to pulse pressure ratio were independently associated with the Framingham score in multiple regression analysis (P < 0.0001 for both). CONCLUSIONS: All three indices to evaluate arterial compliance were feasible to obtain in a general elderly population and were inter-related. Although all of the techniques were correlated to Framingham risk score, only carotid artery distensibility and the stroke volume to pulse pressure ratio were independently related to coronary risk, suggesting complementary use of these two indices of arterial compliance in the future.

Aged↗
PubMed2006

Multifocal osteoma cutis in a golden retriever.

A 10-year-old, spayed female, obese golden retriever, presented for immune-mediated thrombocytopenia, was successfully managed with the administration of vincristine and prednisone. However, 6 mo after discontinuing corticosteroid therapy because of suspected iatrogenic hyperglucocorticoidism, the patient was presented with multiple, firm, bilaterally symmetric, dermal masses composed histologically of differentiated cortical bone.

Adrenal Cortex Hormones↗
PubMed2005

A comparison of three different methods to evaluate endothelium-dependent vasodilation in the elderly: the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study.

BACKGROUND: Three different techniques to evaluate endothelium-dependent vasodilation in the peripheral circulation have been described but not simultaneously tested in a large-scale population-based setting. This study aimed to evaluate the feasibility and usefulness of these techniques in the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study. METHODS AND RESULTS: In the population-based PIVUS study (1016 subjects aged 70 years), the invasive forearm technique with acetylcholine given in the brachial artery (EDV), the brachial artery ultrasound technique with measurement of flow-mediated dilatation (FMD), and the pulse wave analysis method with beta-2-agonist (terbutaline) provocation were successfully used in 87%, 97%, and 86% of the sample, respectively. The results of EDV and pulse wave analysis were interrelated (r=0.12, P=0.0013), but no relationships were found with FMD measurements. All 3 techniques were correlated to the Framingham risk score (r=0.10 to 0.12, P=0.0007 to 0.001). In multiple regression analysis, however, only EDV and FMD were independently associated with the Framingham score. CONCLUSIONS: All 3 evaluated techniques were feasible to perform in a general elderly population. Both the invasive forearm technique and FMD were independently associated with increased coronary risk, suggesting that information on conduit artery and resistance artery endothelial function carry different, but important, information in the elderly. If the invasive technique cannot be used, the pulse wave based technique is an alternative.

Acetylcholine↗
PubMed2005

Bone formation at titanium porous oxide (TiUnite) oral implants in type IV bone.

BACKGROUND: Several oral implant design advances have been suggested to overcome poor bone quality, an impediment for successful implant treatment. A novel titanium porous oxide (TPO) surface has been shown to offer favorable results in several settings. The objective of this study was to evaluate the local bone formation and osseointegration at TPO-modified implants in type IV bone. METHOD: Three TPO surface-modified implants (TiUnite) were installed into the edentulated posterior maxilla in each of 8 Cynomolgus monkeys. The animals were injected with fluorescent bone labels at 2, 3, 4 and 16 weeks post-surgery and were euthanized at week 16 when block biopsies were collected for histologic analysis. RESULTS: The predominant observation of the TPO implant surface was a thin layer of new bone covering most of the implant threads. Mean (+/-SE) bone-implant contact for the whole study group was 74.1 +/- 4.8%. There was a significant variability in bone-implant contact between animals (P = 0.0003) and between sites of the same animal (P < 0.0001). The variance in bone-implant contact was 30% larger among sites of the same animal than between different animals (187.5 vs. 144.8, respectively). There was a small but significant difference in bone density immediately outside, compared to within the threaded area of the implants (37.1 +/- 3.2% vs. 32.1 +/- 3.2%, P < 0.0001). Bone density outside the implant threads was significantly correlated (beta = 0.682, P < 0.0001) with the bone density within the threaded area. Bone density within the threaded area was significantly correlated (beta = 0.493, P = 0.0002) with bone-implant contact, whereas bone density outside the implant threads did not have a significant effect (beta = 0.232, P = 0.1). CONCLUSIONS: The results suggest that the TPO surface possesses a considerable osteoconductive potential promoting a high level of implant osseointegration in type IV bone in the posterior maxilla.

Analysis of Variance↗
PubMed2005

Bone-implant contact at calcium phosphate-coated and porous titanium oxide (TiUnite)-modified oral implants.

BACKGROUND: Calcium phosphate (CP)-coated implants are usually referred to as having osteoconductive properties, whereas titanium implants with a native oxide layer are considered less osteoconductive. Often smooth titanium oxides (TOs) are compared to relatively rough CP structures. The objective of this study was to evaluate osteoconduction by comparing bone-implant contact at a relatively smooth, highly crystalline CP coating with a structured, porous TO (TiUnite)-modified surface. MATERIAL AND METHODS: Ten adult Hound Labrador mongrel dogs were used. Four titanium implants (Nobel Biocare) with CP-coated (2) or TO-modified (2) surfaces were installed 12 weeks following mandibular premolar and molar teeth extraction. The implants were alternated within and between jaw quadrants in consecutive animals. Mucosal flaps were advanced and sutured leaving the implants in a submerged position. The animals were injected with fluorescent bone labels at 3 and 4 weeks postsurgery, and pre-euthanasia to monitor progress of bone formation. The animals were euthanized at 8 weeks postsurgery and block biopsies were prepared for histologic and histometric analysis. RESULTS: There were no remarkable differences in bone formation and apparent bone-implant contact comparing the TO-modified and CP-coated surfaces. However, the measured average bone-implant contact was 71% and 57% (P=0.027) for TO-modified and CP-coated implants, respectively. CONCLUSIONS: We conclude that the TO surface exhibits osteoconductive properties exceeding that of the CP surface. One or several of the chemical and physical properties of the TO surface may result in the remarkable bone formation along its surface. This study indicated that crystallinity and/or chemistry may be important.

Animals↗
PubMed2005

Stimulation of directed bone growth at oxidized titanium implants by macroscopic grooves: an in vivo study.

BACKGROUND: The influence of thread design at the millimeter level and surface topography at the micrometer level on bone integration and the stability of dental implants have been studied extensively. However, less is known about the influence of implant structures in the range of 50 to 200 microm. PURPOSE: The present in vivo investigation was undertaken to study if bone formation and implant stability were influenced by 110 (S1) and 200 (S3) microm-wide and 70 microm-deep grooves positioned at a thread flank of oxidized titanium implants. MATERIALS AND METHODS: Eighteen rabbits and oxidized titanium implants (3.75 mm in diameter and 7 mm long) were used in the study. Nine rabbits received three control implants and three test implants with a 110 microm-wide groove added to one thread flank. The remaining nine rabbits received three control implants and three test implants with a 200 microm-wide groove. The animals were followed for 6 weeks. Removal torque (RTQ) tests were applied to two of the implants in each leg. The remaining implant per leg was retrieved for histology. The degree of bone fill within the grooves and corresponding bone formation at the opposing surfaces, the bone area within the threads, and the degree of bone-implant contact were calculated for each implant. RESULTS: The histologic analyses revealed an affinity for bone formation within the grooves. The RTQ tests showed that the peak RTQ was approximately 30% higher for the S1 implants compared with control implants without a groove. The difference was statistically significant (p < .05) for tibial and pooled implants. A similar but smaller and not statistically significant effect, approximately 8%, was measured for the S3 implants. The histomorphometric measurements confirmed the observed affinity of bone for the grooves. For S1 implants, 78.7 +/- 15.8% of the grooves were filled with bone, whereas only 46.2 +/- 27% of the corresponding flank surface showed the presence of bone (p < .05). The corresponding figures for S3 and control implants were 72.7 +/- 25.1% and 48.5 +/- 13.6%, respectively (p < .05). The degrees of bone-implant contact and bone area within the threads were similar for test and control implants. CONCLUSION: It is concluded that 110 and 200 microm-wide and 70 microm-deep grooves at oxidized implant surfaces stimulated bone to preferentially form within and along the groove in the rabbit model. The 110 microm-wide groove was shown to increase the resistance to shear forces significantly. It is suggested that implants with such a groove may be one way to optimize implant stability in suboptimal clinical conditions.

Animals↗
PubMed2003

Short-term bone response to titanium implants coated with thin radiofrequent magnetron-sputtered hydroxyapatite in rabbits.

BACKGROUND: It has been suggested that calcium phosphate (CaP) coatings initiate faster bone growth around implants. A major concern about the viable use of these coatings has been their biologic performance related to the coating characteristics. PURPOSE: The purpose of this study was to investigate the early bone response to micron- and submicron-thick hydroxyapatite (HA) coatings in cortical and trabecular bone. MATERIALS AND METHODS: CaP coatings were manufactured by magnetron sputtering. Heat treatment was subsequently used to increase the crystallinity of the coatings. Coatings were characterized by x-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES), and stylus profilometry. Four types of CaP-coated implants were used (0.1 microm and 2.0 microm amorphous; 0.1 microm and 2.0 microm crystalline); uncoated machined commercially pure titanium implants served as controls. Four hundred eighty implants were randomly placed in 60 rabbits. Ten animals were followed up for 1 week, 10 for 3 weeks, and 40 for 6 weeks. The bone response was histomorphometrically evaluated. RESULTS: Coatings with a CaP ratio very close to that of HA were produced. Crystalline coatings significantly improved the early bone-implant contact whereas the amorphous-coated implants behaved similarly to uncoated titanium. CONCLUSIONS: Crystalline CaP coatings 100 nm thick on titanium implants elicited an improved early bone response compared with that of uncoated titanium implants. No further improvement in the bone response was observed with 2 microm coatings.

Animals↗
PubMed2002

The effects of mental stress and the cold pressure test on flow-mediated vasodilation.

As a stressful lifestyle has been associated with coronary heart disease, this study aim to evaluate how two stressful tests influence endothelial-dependent vasodilation evaluated by flow-mediated dilation (FMD) of the brachial artery. FMD following 5 min of occlusion of the forearm was evaluated in young healthy volunteers with measurements of brachial artery diameter and blood flow (BABF) using ultrasound before and during a mental arithmetic task (MAT), and during cold pressure test (COP). MAT and COP increased blood pressure to a similar degree (18-21 mmHg). The COP induced a significant reduction in FMD compared to the baseline levels (from 9.3 +/- 3.9 to 5.9 +/- 3.2%, p < 0.01), as well as to the MAT, which in itself did not influence FMD (10.1 +/- 5.0%). However, as MAT increased BABF during hyperaemia significantly, the FMD to BABF ratio was significantly reduced by both stress tests (p < 0.05). Time-control experiments showed FMD measurements to be reproducible and that MAT and COP by themselves only marginally affected brachial artery diameter. In conclusion, cold pressure stress induced an impairment in FMD, but no effect was induced by a MAT. However, when FMD was normalized for the degree of hyperaemic blood flow, the driver of the vasodilation in the brachial artery, a reduction in flow-mediated vasodilation was seen during both mental and cold pressure stress.

Adult↗
PubMed2002

Evaluation of four different methods to measure endothelium-dependent vasodilation in the human peripheral circulation.

At present, several techniques exist that claim to evaluate endothelium-dependent vasodilation (EDV) in the human peripheral circulation. The present study aims to evaluate the relationships between four of these techniques. A group of 24 young, healthy subjects underwent measurements of EDV and endothelium-independent vasodilation (EIDV) in predominately resistance vessels in the forearm using the invasive forearm technique with local infusion of methacholine and sodium nitroprusside, evaluation of flow-mediated vasodilation (FMD) in the conduit brachial artery measured by ultrasound, with or without the addition of ischaemic hand exercise, and evaluation of the reduction in the relative height of the inflection point of the radial pulse wave following beta(2)-adrenergic receptor stimulation. The reduction in the relative height of the inflection point following beta(2)-adrenergic receptor stimulation was significantly related to both EDV and EIDV in the forearm (r=-0.41 and r=-0.42 respectively; both P<0.05), but not to the EDV/EIDV ratio (r=-0.10). However, FMD, with or without the addition of ischaemic hand exercise, was not significantly related to the results obtained using the other two techniques (r=-0.18 to +0.13). In conclusion, the reduction in the relative height of the inflection point of the pulse wave following beta(2)-adrenergic receptor stimulation was related to both EDV and EIDV measured by the invasive forearm technique, indicating that the pulse wave technique does not measure EDV specifically. FMD in the brachial artery, with or without ischaemic hand exercise, was not significantly related to values obtained using the other two techniques, indicating that endothelial function differs between conduit and resistance arteries, and that both of these measurements should be evaluated in future studies.

Adult↗
PubMedDate not supplied

Radiographic assessment of pediatric proximal radius fractures: interrater and intrarater reliability.

Three methods of measuring pediatric proximal radius fracture radiographs were compared using injury films of 32 patients. Angulation and displacement were independently measured by four physicians. One physician measured the films by each method a second time 2 months later. Values for interrater and intrarater reliability were determined using inter- and intra-class coefficients (ICC). Interrater reliability was poor for methods using the axis of the proximal radial fragment or the proximal radial physis as a reference (ICC = 0.47 and 0.42, respectively). Measurement of the angle between a line parallel to the proximal radius articular surface and the radial shaft had the highest interrater reliability (0.76); measurement of displacement had the lowest interrater reliability (0.09). The intrarater reliability was excellent for all methods (0.93-0.99) and was also highest when the proximal articular surface reference was used. Of described methods, use of the proximal radius articular surface and the radial shaft as references had the highest interrater and intrarater reliability.

Adolescent↗
PubMedDate not supplied

Characteristics of congenital scoliosis in a mouse model.

Pregnant mice were exposed to 600 ppm of carbon monoxide on gestation day 9. The carbon monoxide exposure produced 38 spinal anomalies in 17 offspring with congenital scoliosis. Microcomputer tomography improved the identification of spinal anomalies and detected more affected animals, as compared when magnified radiographs were used. The curves were measured and ranged from mild to moderate at an age that corresponds to childhood and, on average, remained at the range of mild to moderate through near-maturity. The group of mice with congenital anomalies near maturity contained severe curves. The bone mineral density (BMD) determined by microcomputer tomography in the mice with congenital scoliosis was the same as that in the controls. The cervical spine BMD was higher than the thoracic BMD, which was higher than the lumbar region in the controls and affected animals. The BMD was highest in the apex of the congenital curves in the animals that were near maturity. This relationship was not seen in the younger mice with congenital curves. Histology revealed growth rates in the hemivertebrae, which, over the last half of the growth period measured, had one-third less growth than the adjacent vertebrae. The hemivertebrae were wedged, but the adjacent disks were not.

Animals↗
PubMedDate not supplied

Long-term bone response to titanium implants coated with thin radiofrequent magnetron-sputtered hydroxyapatite in rabbits.

PURPOSE: The present study was designed to investigate the long-term bone response around machined screw-type uncoated and calcium phosphate (CaP) -coated commercially pure titanium implants. MATERIALS AND METHODS: Using a magnetron sputtering technique, implants with a CaP coating similar in composition and CaP ratio to hydroxyapatite were produced. Heat treatment was subsequently used to increase the crystallinity of the coatings. Four types of coatings (0.1 and 2.0 microm amorphous and 0.1 and 2.0 microm crystalline) were manufactured; uncoated implants served as a control. Three hundred twenty implants (64 of each type) were randomly placed in the tibial cortical and trabecular femoral bones of 40 rabbits. The rabbits were sacrificed 9 months after implant placement. RESULTS: Histomorphometric evaluation carried out on ground sections revealed that the crystalline CaP coatings achieved the highest bone-implant contact in both tibiae and femora compared with amorphous CaP-coated and uncoated titanium. DISCUSSION: The present study suggests that submicron crystalline hydroxyapatite coating adds bioactive properties to titanium oral implants. CONCLUSION: An ultra-thin, 0.1-microm crystalline CaP coating can elicit and maintain an improved long-term bone response compared to amorphous coated or uncoated Ti implants, without any adverse tissue reactions.

Analysis of Variance↗