bluuebunny/crossref_metadata_2025 huggingface dataset:
Lifetime fluoridation exposure and dental caries experience in a military population
Authors: Mahoney Gregory , Slade Gary D. , Kitchener Scott , Barnett Adrian
Published: April 2008

Abstract –  While there is good evidence of caries‐preventive benefits of fluoride in drinking water among children and adolescents, there is little information about effectiveness of water fluoridation among adults.

Objectives:  To determine whether exposure to fluoride in drinking water is associated with caries experience in Australian Defence Force (ADF) personnel.

Methods:  Cross‐sectional study of 876 deployable ADF personnel aged 17–56 years. At each person’s mandatory annual dental examination, military dentists recorded the number of decayed, missing and filled teeth (DMFT) using visual, tactile and radiographic criteria. Participants also completed a questionnaire, listing residential locations in each year from 1964 to 2003. People were classified into four categories according to the percentage of their lifetime living in places with fluoridated water: <10%, 10% to <50%, 50% to <90% and ≥90%. Mean DMFT was compared among those categories of fluoridation exposure and the association was evaluated statistically using analysis of variance to adjust for age, sex, years of service and rank.

Results:  Without adjustment for confounders, the mean DMFT (±95% confidence interval) was 6.3 ± 0.8 for <10% fluoridation exposure, 7.8 ± 0.8 for 10% to <50% exposure, 7.5 ± 0.7 for 50% to <90% exposure and 4.6 ± 0.6 for ≥90% exposure (P < 0.01). However, age was inversely associated with mean DMFT and in the <10% exposure group, 91% of people were aged <35 years. Service rank was also significantly associated with both fluoridation exposure and DMFT. After adjustment for all covariates, mean DMFT was 24% lower among people in the two groups with ≥50% exposure compared with the <10% exposure group.

Conclusions:  Degree of lifetime exposure to fluoridated drinking water was inversely associated with DMFT in a dose–response manner among this adult military population.
Prevalence of hyposalivation in relation to general health, body mass index and remaining teeth in different age groups of adults
Authors: Flink Håkan , Bergdahl Maud , Tegelberg Åke , Rosenblad Andreas , Lagerlöf Folke
Published: April 2008

Abstract –  Objectives:  Several studies have been conducted on the prevalence of hyposalivation in older adults but no population‐based studies in younger adults. Therefore, our aims were to determine the prevalence of very low and low unstimulated (UWSFR) and stimulated (SWSFR) whole salivary flow rates in different age groups between 20 and 69 years, and to analyse the relationship between hyposalivation, subjective oral dryness and predictors of reduced flow rate.

Methods:  A randomized and stratified cross‐sectional study including 1427 dental patients was conducted. UWSFR and SWSFR were measured, numbers of remaining teeth recorded and a questionnaire answered regarding subjective oral dryness, general diseases, use of drugs, body mass index (BMI) and use of tobacco.

Results:  The prevalence of very low (<0.1 ml/min) and low (0.10–0.19 ml/min) UWSFR was similar for different age groups up to 50 years, ranging between 10.9–17.8% and 17.3–22.7%, respectively. The prevalence of very low UWSFR was significantly higher for women aged 50–69 years than for younger women. For men, prevalence of very low UWSFR was higher at 60–69 years. The prevalence of very low (<0.7 ml/min) and low (0.70 – 0.99 ml/min) SWSFR was between 0–5.5% and 0.8–8.2%, respectively, for the different age groups 20–69 years. Multiple logistic regression revealed that age above 50 years, female gender, having fewer than 20 teeth, and taking xerogenic drugs significantly increased the risk of very low UWSFR. For very low SWSFR, only having fewer than 20 teeth and taking more than two drugs were significant. In the younger individuals (<50 years) only BMI > 25 for very low UWSFR and diagnosed disease for very low SWSFR were found significant. In this younger subset, female gender combined with having fewer than 27 teeth was significant for low UWSFR.

Conclusions:  Hyposalivation is prevalent in younger adults, among whom it is associated with diagnosed disease and high BMI, while after age 50 years it is associated with medication. It is also associated with gender and with fewer remaining teeth.
Refining exposure definitions for studies of periodontal disease and systemic disease associations
Authors: Demmer Ryan T. , Kocher Thomas , Schwahn Christian , Völzke Henry , Jacobs Jr David R. , Desvarieux Moïse
Published: April 2008

Abstract –  Background:  Substantial variation exists in reported associations between periodontal infections and cardiovascular disease. Imprecise periodontal exposure definitions are possible contributors to this variability. We studied appropriate exposure definitions for studying associations between clinical periodontal disease (PD) and systemic disease.

Methods:  Data originate from men and women aged 20–79 enrolled in the Study of Health in Pomerania (SHIP) from 1997–2001. Age and sex‐adjusted correlation analysis identified PD definitions with the highest cross‐sectional associations with three subclinical markers of systemic disease: plasma fibrinogen (n = 3481), serum hemoglobin A1c (HbA1c) (n = 3480), and common carotid artery intima‐media thickness (c‐IMT) (n = 1745, age  ≥ 45).

Results:  In men and women, percent of sites with attachment loss (AL) ≥6 mm and tooth loss both revealed the highest correlation with HbA1c (ρ = 0.11; several other definitions related similarly), while the strongest fibrinogen correlation was observed with percent of sites with pocket depth ≥3 mm (ρ = 0.19). Findings for c‐IMT among men were strongest for percent of sites with AL ≥6 mm (ρ = 0.14; several other definitions related similarly) while among women, percent of sites with pocket depth ≥5 or 6 mm had the highest observed correlation (ρ = 0.13).

Conclusions:  A range of near optimal definitions varied according to gender and whether the systemic disease marker reflected an acute or chronic situation. Pocket depth was more strongly correlated with the acute marker fibrinogen while attachment and tooth loss tended to be more strongly correlated with the chronic markers, HbA1c, and c‐IMT. These findings can be useful in designing future studies investigating the association between PD and systemic disease.
Occlusal caries detection in permanent molars according to WHO basic methods, ICDAS II and laser fluorescence measurements
Authors: Kühnisch Jan , Berger Susanne , Goddon Inka , Senkel Helga , Pitts Nigel , Heinrich‐Weltzien Roswitha
Published: April 2008

Abstract –  This epidemiological study aimed to compare the diagnostic outcome of the WHO criteria, ICDAS II criteria, laser fluorescence measurements, presence of plaque and roughness as activity scores on occlusal fissures and buccal/palatal pits of the first permanent molars. The study involved 311 children between 8 and 12 years of age from the Ennepe‐Ruhr District in North Rhine‐Westphalia, Germany. The surface‐related caries status was registered according to the WHO basic method criteria (1997). Additionally, pit and fissure sealants, the ICDAS II visual criteria, the DIAGNOdent reading, plaque retention and surface roughness were documented. Caries experience was 1.0 (±2.5) DMFS. About 70% of the examined students had no obvious dentin caries in the permanent dentition (DMFS = 0). Sealants were registered on 1.4 (±1.7) occlusal fissures and 0.4 (±0.9) palatal/buccal pits. Noncavitated caries lesions were recorded as ICDAS II score 1–4 on 1.8 (±1.6) fissures and 1.5 (±1.4) pits. The comparison of the diagnostic methods suggests a relationship between higher ICDAS II scores/DIAGNOdent values and a proportional increase in the occurrence of plaque as well as in the number of rough surfaces. In conclusion, this study showed the diagnostic potential of the ICDAS II criteria in comparison to the traditional WHO criteria by means of the noncavitated caries lesions additionally detected. The DIAGNOdent use in field studies that already apply detailed visual criteria seems to bring limited additional information. While the presence of plaque provides information for the caries activity assessment more work is required to provide information about the contribution of surface roughness.
Allergic contact dermatitis to DMDI in an office application
Authors: Kerre Stefan
Published: April 2008

Contact dermatitis to isocyanates is a problem and is usually described within industrial settings. A patient who developed an acute allergic contact dermatitis using a dicyclohexylmethane‐4,4′‐diisocyanate (DMDI)‐charged cartridge to create resin‐coated ‘3D labels’ within an office environment is described.
Cytokine gene polymorphisms and susceptibility to chronic irritant contact dermatitis
Authors: DeJongh Cindy M. , John Swen M. , Bruynzeel Derk P. , Calkoen Florentine , VanDijk Frank J. H. , Khrenova Liubov , Rustemeyer Thomas , Verberk Maarten M. , Kezic Sanja
Published: April 2008

Background:  Cytokines play an important role in skin inflammation.

Objectives:  We determined whether polymorphisms in cytokine genes contribute to the occurrence of occupational chronic irritant contact dermatitis (CICD).

Methods:  In a case–control study, 9 polymorphisms in the genes coding for interleukin (IL)‐1α, IL‐1β, IL‐8, IL‐10, and tumour necrosis factor (TNF)‐α were determined in 197 patients with CICD. 217 apprentices in vocational training for high‐risk occupations for CICD served as controls.

Results:  For all polymorphisms, no differences in genotype distributions were found between patients and controls. However, in patients with self‐reported low levels of wet work and irritant exposure, more TNFA −308 variant genotypes (G/A and A/A) were present compared with those exposed to higher levels or controls, which indicates a TNFA‐induced increase of susceptibility. In patients with TNFA −308 variant genotypes, the prevalence of flexural eczema was higher (48% and 57%) compared with that in patients presented with wild‐type genotype (30%). Regarding IL1A −889, prevalence of symptoms of dermatitis was lower in apprentices with T/T or C/T genotype (32% and 36%) compared with wild‐type genotype (54%, C/C). This indicates a protective effect of these variant alleles in acquiring hand dermatitis.

Conclusions:  This study provides evidence that some genetic variations alter susceptibility to (chronic) dermatitis. Knowledge of the impact of genetic differences on the risk of CICD is essential in predictive testing of individuals at risk.
Lipids and skin barrier function – a clinical perspective
Authors: Jungersted Jakob Mutanu , Hellgren Lars I. , Jemec Gregor B. E. , Agner Tove
Published: April 2008

The stratum corneum (SC) protects us from dehydration and external dangers. Much is known about the morphology of the SC and penetration of drugs through it, but the data are mainly derived from in vitro and animal experiments. In contrast, only a few studies have the human SC lipids as their focus and in particular, the role of barrier function in the pathogenesis of skin disease and its subsequent treatment protocols. The 3 major lipids in the SC of importance are ceramides, free fatty acids, and cholesterol. Human studies comparing levels of the major SC lipids in patients with atopic dermatitis and healthy controls have suggested a possible role for ceramide 1 and to some extent ceramide 3 in the pathogenesis of the disease. Therapies used in diseases involving barrier disruption have been sparely investigated from a lipid perspective. It has been suggested that ultraviolet light as a treatment increases the amount of all 3 major SC lipids, while topical glucocorticoids may lead to a decrease. Such effects may influence the clinical outcome of treatment in diseases with impaired barrier function. We have, therefore, conducted a review of the literature on SC lipids from a clinical perspective. It may be concluded that the number of human studies is very limited, and in the perspective of how important diseases of impaired barrier function are in dermatology, further research is needed.
Favorable effects of a prolonged treatment with melatonin on the level of oxidative damage and neurodegeneration in senescence‐accelerated mice
Authors: Caballero Beatriz , Vega‐Naredo Ignacio , Sierra Verónica , Huidobro‐Fernández Covadonga , Soria‐Valles Clara , Gonzalo‐Calvo David De , Tolivia Delio , Gutierrez‐Cuesta Javier , Pallas Merce , Camins Antonio , Rodríguez‐Colunga María Josefa , Coto‐Montes Ana
Published: April 2008

Abstract:  Senescence‐accelerated mice (SAMP8) and senescence‐accelerated resistant mice (SAMR1) were studied at 5 and 10 months of age, respectively. In the animals, neurodegenerative processes and how they were influenced by melatonin were examined. Melatonin (10 mg/kg) or vehicle (ethanol at 0.066%) treatments were administrated from the age of 1 to 9 months in the drinking water. Differences in the neurodegenerative markers examined were found between the two strains with a more damaged protein, phosphorylated Tau at Ser392, increased neurofibrillary tangles (NT) and higher α‐synuclein expression in SAMP8 versus SAMR1 mice overall, when the mice were 10 months of age. Changes in density of receptors and oxidative stress‐related signaling with age were found in the brains of SAM strains at 10 months as shown by a marked decrease in the level of MT‐1 melatonin receptor and retinoic acid receptor‐related orphan receptor (ROR)‐α1. This diminution was earlier and more pronounced in SAMP8 mice. Likewise, the levels of nuclear factor‐kappa B (NF‐kB) transcriptional factor were higher in SAMP8 mice compared with SAMR1 mice regardless of age confirming the direct role of oxidative stress in the aging process. Treatment with melatonin in SAMP8 and SAMR1 mice reduced the neurodegenerative changes with an increase of ROR‐α1 levels without an apparent influence in the levels of MT‐1 receptor. However, different melatonin effects on NF‐kB signaling were observed suggesting that NF‐kB could trigger inflammatory processes in a different way, being SAM strain‐dependent and associated with age‐related oxidative stress levels. The effectiveness of melatonin in improving age‐related neural impairments is corroborated.
Melatonin protects from hepatic reperfusion injury through inhibition of IKK and JNK pathways and modification of cell proliferation
Authors: Liang Rui , Nickkholgh Arash , Hoffmann Katrin , Kern Michael , Schneider Heinz , Sobirey Michael , Zorn Markus , Büchler Markus W. , Schemmer Peter
Published: April 2008

Abstract:  Reactive oxygen species (ROS) are involved in pathophysiology of ischemia/reperfusion injury. Melatonin is a potent scavenger of ROS. Thus, this study was designed to elucidate its effects in a combined hepatic warm ischemia and resection model. The right lateral and caudate lobes (32% of liver volume) of Sprague–Dawley rats underwent warm ischemia for 30 min followed by reperfusion and subsequent resection of the nonischemic liver tissue. Some rats were gavaged with 50 mg/kg melatonin 2 hr before the onset of experiments. Controls received the same volume of microcrystalline cellulose. Survival, transaminases, histology, flow cytometry, inducible nitric oxide synthase (iNOS) expression, and activation of signal transduction pathways [c‐Jun N‐terminal kinase (JNK), cJUN, IκB kinase α (IKKα), proliferating cell nuclear antigen (PCNA), and Ki67] were assessed for hepatic injury, oxidative stress, and cell proliferation. Melatonin significantly improved animal survival and decreased transaminase levels, the indices for necrosis, liver damage, leukocyte infiltration, and iNOS expression. In parallel, the expression of IKKα, JNK1, and cJUN decreased by 35–50% after melatonin (P < 0.05). At the same time, melatonin reduced the expression of both PCNA and Ki67 in liver (P < 0.05). Melatonin is hepatoprotective most likely via mechanisms including inhibition of IKK and JNK pathways and regulation of cell proliferation.
ORIGINAL ARTICLE: Presence of Antisperm Antibodies Reactive with Peptide Epitopes of FA‐1 and YLP12 in Sera of Immunoinfertile Women
Authors: Williams Jessica , Samuel Arthur , Naz Rajesh K.
Published: April 2008

Problem

Recent studies in several laboratories are focused on delineating sperm antigens that are relevant to fertility and examining involvement of antibodies to these antigens in human immunoinfertility. Our laboratory has characterized two such antigens, namely fertilization antigen (FA‐1) and YLP12 dodecamer sequence that are involved in sperm‐oocyte binding. The present study was conducted to examine the occurrence of isoantibodies to various peptide epitopes of human and murine FA‐1 antigen and YLP12 peptide in sera of immunoinfertile and fertile women.

Method of study

Sera from 67 immunoinfertile and 19 fertile women were collected. Various peptides based up on human and murine FA‐1 antigen and YLP12 were synthesized, and examined for immunoreactivity with these sera by using ELISA. Four immunodominant sequences, two each from human (hFA‐182‐97aa and hFA‐1200‐219aa) and mouse (mFA‐12‐19aa and mFA‐1117‐136aa) FA‐1 antigen, were selected for the present study. Another human FA‐1 sequence, hFA‐1220‐240aa, that was not in the immunodominant region was used as a control.

Results

For human FA‐1 peptides, 41.8% of the immunoinfertile sera reacted positively (≥2 SD units) with hFA‐182‐97aa, 24.6% (16/65) with hFA‐1200‐219aa, and 3% (2/66) with hFA‐1220‐240aa peptide. For two murine FA‐1 peptides, 41.7% (25/60) of the immunoinfertile sera reacted positively with mFA‐12‐19aa, and 41.5% (27/65) with mFA‐1117‐136aa peptide. For the YLP12 dodecamer peptide, 43.3% (29/67) of the immunoinfertile sera reacted positively. None of the sera from fertile women reacted positively with any of these peptides.

Conclusion

In conclusion, our data indicate that the immunoinfertile women have circulating isoantibodies against at least two immunodominant peptide epitopes of human and murine FA‐1 antigen and YLP12 peptide sequence. These peptides may find clinical application in the specific diagnosis and treatment of female infertility and contraceptive vaccine development.
ORIGINAL ARTICLE: Prevention of Spontaneous Abortion in the CBA × DBA/2 Mouse Model by Intravaginal TGF‐β and Local Recruitment of CD4+ 8+ FOXP3+ Cells
Authors: Clark David A. , Fernandez Jason , Banwatt Daljeet
Published: April 2008

Problem

Activation of latent transforming growth factor (TGF)‐β in seminal plasma has been suggested by Robertson et al. to promote maternal tolerance to paternal antigens. A possible consequence reported by Tremellen et al. is increased pregnancy rates in women undergoing IVF. A decreased spontaneous abortion rate has also been postulated. Seminal plasma contains many factors besides TGF‐β, and a critical test of the hypothesis was required. The purpose of the present study was to directly test the effect of pure TGF‐β.

Method of study

Pharmaceutical grade bioactive TGF‐β3 with a bovine serum albumin (BSA) carrier 0.1–1% in phosphate‐buffered saline (PBS) was given into the vaginal tract of CBA/J female mice at the time of mating with DBA/2 males. One microgram Salmonella enteritidis lipopolysaccharide was given intraperitoneally to augment occult losses and spontaneous resorptions assessed on day 13.5 of pregnancy. The effect of TGF‐β3 on recruitment of lymphomyeloid cells to the vaginal wall and vaginal lumen of unmated mice in estrus was assessed using immunohistochemistry and flow cytometry.

Results

Two nanogram of intravaginal TGF‐β3 in 0.1% BSA–PBS or 20 ng in 1% BSA–PBS reduced abortion rates. Protection was comparable to that achieved by immunization with BALB/c spleen cells. Fraction V BSA, a binder of TGF‐βs, had some activity, and could reduce availability of added TGF‐β3. CD11c dendritic cells, CD3+ T cells, and CD25+ cells were recruited to the vaginal wall by 48 hr after TGF‐β3 treatment, and cellularity of vaginal exudates increased. Foxp3+ cells were present in increased numbers, and appeared to be CD8+ and CD4+ 8+. Semen, but not TGF‐β3, stimulated a physiological polymorphonuclear leukocyte exudate.

Conclusion

Intravaginal bioactive TGF‐β3 can enhance success of pregnancy in vivo in an established model of abortion. The result could be explained by the independent ability of TGF‐β to promote a regulatory T‐cell response.
Anal intraepithelial neoplasia in HIV infection
Authors: Kreuter Alexander , Brockmeyer Norbert H. , Altmeyer Peter , Wieland Ulrike ,   for the German Competence Network HIV/AIDS
Published: April 2008

Human papillomavirus (HPV) infections belong to the most common sexually transmitted infections worldwide. While the immune system eliminates most HPV infections over time in immunocompetent individuals, HPV infections tend to persist in immunodeficient individuals. In HIV‐infected men who have sex with men (MSM), anal HPV prevalence is more than 90% and infections with multiple HPV types are common. Consequently, HPV‐associated anogenital malignancies occur with high frequency in patients with HIV infection. Anal intraepithelial neoplasia (AIN) is a potential precursor lesion of squamous cell carcinoma of the anus. Like its cervical counterpart, cervical intraepithelial neoplasia (CIN), AIN is causally linked to persistent infections with high‐risk HPV types such as HPV16 or HPV18. As AIN and CIN share distinct biological similar‐ities, AIN screenings analogous to Pap smear programs for CIN have been recommended in high‐risk populations to reduce the incidence of anal carcinoma. These screenings include cytological analysis followed by high resolution anoscopy in case of anal dysplasia.

Treatment guidelines for AIN are not yet available. Therapeutic strategies can be divided into topical (e.g. trichloroacetic acid, podophyllotoxin, imiquimod, photodynamic therapy) and ablative (e. g. surgical excision, laser ablation, infrared coagulation, electrocautery) measures. However, controlled studies on AIN treatment have not been performed. The impact of HPV vaccination on AIN development will also need to be assessed. Long‐term follow‐up of these patients is essential to gain more insight into the natural history of anogenital HPV infection in HIV‐positive MSM.
Biomechanical Properties of Abdominal Organs In Vivo and Postmortem Under Compression Loads
Authors: Rosen Jacob , Brown Jeffrey D. , De Smita , Sinanan Mika , Hannaford Blake
Published: April 2008

Accurate knowledge of biomechanical characteristics of tissues is essential for developing realistic computer-based surgical simulators incorporating haptic feedback, as well as for the design of surgical robots and tools. As simulation technologies continue to be capable of modeling more complex behavior, an in vivo tissue property database is needed. Most past and current biomechanical research is focused on soft and hard anatomical structures that are subject to physiological loading, testing the organs in situ. Internal organs are different in that respect since they are not subject to extensive loads as part of their regular physiological function. However, during surgery, a different set of loading conditions are imposed on these organs as a result of the interaction with the surgical tools. Following previous research studying the kinematics and dynamics of tool/tissue interaction in real surgical procedures, the focus of the current study was to obtain the structural biomechanical properties (engineering stress-strain and stress relaxation) of seven abdominal organs, including bladder, gallbladder, large and small intestines, liver, spleen, and stomach, using a porcine animal model. The organs were tested in vivo, in situ, and ex corpus (the latter two conditions being postmortem) under cyclical and step strain compressions using a motorized endoscopic grasper and a universal-testing machine. The tissues were tested with the same loading conditions commonly applied by surgeons during minimally invasive surgical procedures. Phenomenological models were developed for the various organs, testing conditions, and experimental devices. A property database—unique to the literature—has been created that contains the average elastic and relaxation model parameters measured for these tissues in vivo and postmortem. The results quantitatively indicate the significant differences between tissue properties measured in vivo and postmortem. A quantitative understanding of how the unconditioned tissue properties and model parameters are influenced by time postmortem and loading condition has been obtained. The results provide the material property foundations for developing science-based haptic surgical simulators, as well as surgical tools for manual and robotic systems.
The Effects of Femoral Fixed Body Coordinate System Definition on Knee Kinematic Description
Authors: Lenz Nathaniel M. , Mane Amitkumar , Maletsky Lorin P. , Morton Nicholas A.
Published: April 2008

Understanding the differences in knee kinematic descriptions is important for comparing data from different laboratories and observing small but important changes within a set of knees. The purpose of this study was to identify how differences in fixed body femoral coordinate systems affect the described tibiofemoral and patellofemoral kinematics for cadaveric knee studies with no hip present. Different methods for describing kinematics were evaluated on a set of seven cadaveric knees during walking in a dynamic knee simulator. Three anatomical landmark coordinate systems, a partial helical axis, and an experimental setup-based system were examined. The results showed that flexion-extension was insensitive to differences in the kinematic systems tested, internal-external rotation was similar for most femoral coordinate systems although there were changes in absolute position, varus-valgus was the most sensitive to variations in flexion axis direction, and anterior-posterior motion was most sensitive to femoral origin location. Femoral coordinate systems that define the sagittal plane using anatomical landmarks and locate the flexion axis perpendicular to the femur’s mechanical axis in the frontal plane were typically similar and described kinematics most consistently.
Study of Micromotion in Modular Acetabular Components During Gait and Subluxation: A Finite Element Investigation
Authors: Amirouche F. , Romero F. , Gonzalez M. , Aram L.
Published: April 2008

Polyethylene wear after total hip arthroplasty may occur as a result of normal gait and as a result of subluxation and relocation with impact. Relocation of a subluxed hip may impart a moment to the cup creating sliding as well as compression at the cup liner interface. The purpose of the current study is to quantify, by a validated finite element model, the forces generated in a hip arthroplasty as a result of subluxation relocation and compare them to the forces generated during normal gait. The micromotion between the liner and acetabular shell was quantified by computing the sliding track and the deformation at several points of the interface. A finite element analysis of polyethylene liner stress and liner/cup micromotion in total hip arthroplasty was performed under two dynamic profiles. The first profile was a gait loading profile simulating the force vectors developed in the hip arthroplasty during normal gait. The second profile is generated during subluxation and subsequent relocation of the femoral head. The forces generated by subluxation relocation of a total hip arthroplasty can exceed those forces generated during normal gait. The induced micromotion at the cup polyethylene interface as a result of subluxation can exceed micromotion as a result of the normal gait cycle. This may play a significant role in the generation of backsided wear. Minimizing joint subluxation by restoring balance to the hip joint after arthroplasty should be explored as a strategy to minimize backsided wear.
Continuum Mechanics Analysis of Fracture Progression in the Vitrified Cryoprotective Agent DP6
Authors: Steif Paul S. , Palastro Matthew C. , Rabin Yoed
Published: April 2008

As part of an ongoing effort to study the continuum mechanics effects associated with cryopreservation, the current report focuses on the prediction of fracture formation in cryoprotective agents. Fractures had been previously observed in 1ml samples of the cryoprotective agent cocktail DP6, contained in a standard 15ml glass vial, and subjected to various cooling rates. These experimental observations were obtained by means of a cryomacroscope, which has been recently presented by the current research team. High and low cooling rates were found to produce very distinct patterns of cracking. The current study seeks to explain the observed patterns on the basis of stresses predicted from finite element analysis, which relies on a simple viscoelastic constitutive model and on estimates of the critical stress for cracking. The current study demonstrates that the stress, which results in instantaneous fracture at low cooling rates, is consistent with the stress to initiate fracture at high cooling rate. This consistency supports the credibility of the proposed constitutive model and analysis, and the unified criterion for fracturing, that is, a critical stress threshold.
Heat Transfer to Blood Flow in a Small Tube
Authors: Wang C. Y.
Published: April 2008

Blood flow in a small tube (30–1000μm) can be successfully modeled by the two-fluid model. The fully developed, constant heat flux convective heat transfer problem is studied. The velocity and temperature profiles are determined in closed form. Formulas for friction-factor-Reynolds number product, axial temperature gradient, and Nusselt number are found.
Development and Validation of Subject-Specific Finite Element Models for Blunt Trauma Study
Authors: Shen Weixin , Niu Yuqing , Mattrey Robert F. , Fournier Adam , Corbeil Jackie , Kono Yuko , Stuhmiller James H.
Published: April 2008

This study developed and validated finite element (FE) models of swine and human thoraxes and abdomens that had subject-specific anatomies and could accurately and efficiently predict body responses to blunt impacts. Anatomies of the rib cage, torso walls, thoracic, and abdominal organs were reconstructed from X-ray computed tomography (CT) images and extracted into geometries to build FE meshes. The rib cage was modeled as an inhomogeneous beam structure with geometry and bone material parameters determined directly from CT images. Meshes of soft components were generated by mapping structured mesh templates representative of organ topologies onto the geometries. The swine models were developed from and validated by 30 animal tests in which blunt insults were applied to swine subjects and CT images, chest wall motions, lung pressures, and pathological data were acquired. A comparison of the FE calculations of animal responses and experimental measurements showed a good agreement. The errors in calculated response time traces were within 10% for most tests. Calculated peak responses showed strong correlations with the experimental values. The stress concentration inside the ribs, lungs, and livers produced by FE simulations also compared favorably to the injury locations. A human FE model was developed from CT images from the Visible Human project and was scaled to simulate historical frontal and side post mortem human subject (PMHS) impact tests. The calculated chest deformation also showed a good agreement with the measurements. The models developed in this study can be of great value for studying blunt thoracic and abdominal trauma and for designing injury prevention techniques, equipments, and devices.
Importance of Collagen Orientation and Depth-Dependent Fixed Charge Densities of Cartilage on Mechanical Behavior of Chondrocytes
Authors: Korhonen Rami K. , Julkunen Petro , Wilson Wouter , Herzog Walter
Published: April 2008

The collagen network and proteoglycan matrix of articular cartilage are thought to play an important role in controlling the stresses and strains in and around chondrocytes, in regulating the biosynthesis of the solid matrix, and consequently in maintaining the health of diarthrodial joints. Understanding the detailed effects of the mechanical environment of chondrocytes on cell behavior is therefore essential for the study of the development, adaptation, and degeneration of articular cartilage. Recent progress in macroscopic models has improved our understanding of depth-dependent properties of cartilage. However, none of the previous works considered the effect of realistic collagen orientation or depth-dependent negative charges in microscopic models of chondrocyte mechanics. The aim of this study was to investigate the effects of the collagen network and fixed charge densities of cartilage on the mechanical environment of the chondrocytes in a depth-dependent manner. We developed an anisotropic, inhomogeneous, microstructural fibril-reinforced finite element model of articular cartilage for application in unconfined compression. The model consisted of the extracellular matrix and chondrocytes located in the superficial, middle, and deep zones. Chondrocytes were surrounded by a pericellular matrix and were assumed spherical prior to tissue swelling and load application. Material properties of the chondrocytes, pericellular matrix, and extracellular matrix were obtained from the literature. The loading protocol included a free swelling step followed by a stress-relaxation step. Results from traditional isotropic and transversely isotropic biphasic models were used for comparison with predictions from the current model. In the superficial zone, cell shapes changed from rounded to elliptic after free swelling. The stresses and strains as well as fluid flow in cells were greatly affected by the modulus of the collagen network. The fixed charge density of the chondrocytes, pericellular matrix, and extracellular matrix primarily affected the aspect ratios (height/width) and the solid matrix stresses of cells. The mechanical responses of the cells were strongly location and time dependent. The current model highlights that the collagen orientation and the depth-dependent negative fixed charge densities of articular cartilage have a great effect in modulating the mechanical environment in the vicinity of chondrocytes, and it provides an important improvement over earlier models in describing the possible pathways from loading of articular cartilage to the mechanical and biological responses of chondrocytes.
Ageing Changes in the Tensile Properties of Tendons: Influence of Collagen Fibril Volume Fraction
Authors: Goh K. L. , Holmes D. F. , Lu H.-Y. , Richardson S. , Kadler K. E. , Purslow P. P. , Wess T. J.
Published: April 2008

Connective tissues are biological composites comprising of collagen fibrils embedded in (and reinforcing) the hydrated proteoglycan-rich (PG) gel within the extracellular matrices (ECMs). Age-related changes to the mechanical properties of tissues are often associated with changes to the structure of the ECM, namely, fibril diameter. However, quantitative attempts to correlate fibril diameter to mechanical properties have yielded inconclusive evidence. Here, we described a novel approach that was based on the rule of mixtures for fiber composites to evaluate the dependence of age-related changes in tendon tensile strength (σ) and stiffness (E) on the collagen fibril cross-sectional area fraction (ρ), which is related to the fibril volume fraction. Tail tendons from C57BL6 mice from age groups 1.6–35.3months old were stretched to failure to determine σ and E. Parallel measurements of ρ as a function of age were made using transmission electron microscopy. Mathematical models (rule of mixtures) of fibrils reinforcing a PG gel in tendons were used to investigate the influence of ρ on ageing changes in σ and E. The magnitudes of σ, E, and ρ increased rapidly from 1.6monthsto4.0months (P-values <0.05) before reaching a constant (age independent) from 4.0monthsto29.0months (P-values >0.05); this trend continued for E and ρ (P-values >0.05) from 29.0monthsto35.3months, but not for σ, which decreased gradually (P-values <0.05). Linear regression analysis revealed that age-related changes in σ and E correlated positively to ρ (P-values <0.05). Collagen fibril cross-sectional area fraction ρ is a significant predictor of ageing changes in σ and E in the tail tendons of C57BL6 mice.
Primary Stability of Cementless Stem in THA Improved With Reduced Interfacial Gaps
Authors: Park Youngbae , Shin HoChul , Choi DonOk , Albert Carolyne , Yoon Yong-San
Published: April 2008

Large interfacial gaps between the stem and the bone in cementless total hip arthroplasty may prevent successful bone ingrowth at the sites, and can also be a passage for wear particles. Furthermore, interfacial gaps between the stem and the bone are believed to compromise the primary stability of the implant. Thus, a broaching method that serves to reduce gaps is expected to give clinically preferable results. A modified broach system with a canal guide is introduced to enhance the accuracy of femoral canal shaping in comparison with the conventional broach system for a Versys™ fibermetal taper stem. The primary stability of the hip systems and the ratios of the stem surface in contact with the femur were measured in a composite femur model. With the conventional method, an average of 67% of the stem surface was shown to be in contact with the bone, and an average stem micromotion/migration of 35μm∕290μm was observed under 1000cycles of stair climbing loads. With the modified method, the stem-bone contact ratio significantly increased to 82% (p<0.05), and the average micromotion/migration reduced to 29μm∕49μm, respectively (p<0.05 for migration). Our finite element models of the hip systems supported that the difference in micromotion could be attributed to the difference in interfacial contact. Interfacial gaps occurring with the conventional broach system were effectively reduced by the proposed method, resulting in improved primary stability.
Measurement of the Dynamic Shear Modulus of Mouse Brain Tissue In Vivo by Magnetic Resonance Elastography
Authors: Atay Stefan M. , Kroenke Christopher D. , Sabet Arash , Bayly Philip V.
Published: April 2008

In this study, the magnetic resonance (MR) elastography technique was used to estimate the dynamic shear modulus of mouse brain tissue in vivo. The technique allows visualization and measurement of mechanical shear waves excited by lateral vibration of the skull. Quantitative measurements of displacement in three dimensions during vibration at 1200Hz were obtained by applying oscillatory magnetic field gradients at the same frequency during a MR imaging sequence. Contrast in the resulting phase images of the mouse brain is proportional to displacement. To obtain estimates of shear modulus, measured displacement fields were fitted to the shear wave equation. Validation of the procedure was performed on gel characterized by independent rheometry tests and on data from finite element simulations. Brain tissue is, in reality, viscoelastic and nonlinear. The current estimates of dynamic shear modulus are strictly relevant only to small oscillations at a specific frequency, but these estimates may be obtained at high frequencies (and thus high deformation rates), noninvasively throughout the brain. These data complement measurements of nonlinear viscoelastic properties obtained by others at slower rates, either ex vivo or invasively.
PIV-Measured Versus CFD-Predicted Flow Dynamics in Anatomically Realistic Cerebral Aneurysm Models
Authors: Ford Matthew D. , Nikolov Hristo N. , Milner Jaques S. , Lownie Stephen P. , DeMont Edwin M. , Kalata Wojciech , Loth Francis , Holdsworth David W. , Steinman David A.
Published: April 2008

Computational fluid dynamics (CFD) modeling of nominally patient-specific cerebral aneurysms is increasingly being used as a research tool to further understand the development, prognosis, and treatment of brain aneurysms. We have previously developed virtual angiography to indirectly validate CFD-predicted gross flow dynamics against the routinely acquired digital subtraction angiograms. Toward a more direct validation, here we compare detailed, CFD-predicted velocity fields against those measured using particle imaging velocimetry (PIV). Two anatomically realistic flow-through phantoms, one a giant internal carotid artery (ICA) aneurysm and the other a basilar artery (BA) tip aneurysm, were constructed of a clear silicone elastomer. The phantoms were placed within a computer-controlled flow loop, programed with representative flow rate waveforms. PIV images were collected on several anterior-posterior (AP) and lateral (LAT) planes. CFD simulations were then carried out using a well-validated, in-house solver, based on micro-CT reconstructions of the geometries of the flow-through phantoms and inlet/outlet boundary conditions derived from flow rates measured during the PIV experiments. PIV and CFD results from the central AP plane of the ICA aneurysm showed a large stable vortex throughout the cardiac cycle. Complex vortex dynamics, captured by PIV and CFD, persisted throughout the cardiac cycle on the central LAT plane. Velocity vector fields showed good overall agreement. For the BA, aneurysm agreement was more compelling, with both PIV and CFD similarly resolving the dynamics of counter-rotating vortices on both AP and LAT planes. Despite the imposition of periodic flow boundary conditions for the CFD simulations, cycle-to-cycle fluctuations were evident in the BA aneurysm simulations, which agreed well, in terms of both amplitudes and spatial distributions, with cycle-to-cycle fluctuations measured by PIV in the same geometry. The overall good agreement between PIV and CFD suggests that CFD can reliably predict the details of the intra-aneurysmal flow dynamics observed in anatomically realistic in vitro models. Nevertheless, given the various modeling assumptions, this does not prove that they are mimicking the actual in vivo hemodynamics, and so validations against in vivo data are encouraged whenever possible.
Contributions of the Individual Muscles of the Shoulder to Glenohumeral Joint Stability During Abduction
Authors: Yanagawa Takashi , Goodwin Cheryl J. , Shelburne Kevin B. , Giphart J. Erik , Torry Michael R. , Pandy Marcus G.
Published: April 2008

The aim of this study was to determine the relative contributions of the deltoid and rotator cuff muscles to glenohumeral joint stability during arm abduction. A three-dimensional model of the upper limb was used to calculate the muscle and joint-contact forces at the shoulder for abduction in the scapular plane. The joints of the shoulder girdle—sternoclavicular joint, acromioclavicular joint, and glenohumeral joint—were each represented as an ideal three degree-of-freedom ball-and-socket joint. The articulation between the scapula and thorax was modeled using two kinematic constraints. Eighteen muscle bundles were used to represent the lines of action of 11 muscle groups spanning the glenohumeral joint. The three-dimensional positions of the clavicle, scapula, and humerus during abduction were measured using intracortical bone pins implanted into one subject. The measured bone positions were inputted into the model, and an optimization problem was solved to calculate the forces developed by the shoulder muscles for abduction in the scapular plane. The model calculations showed that the rotator cuff muscles (specifically, supraspinatus, subscapularis, and infraspinatus) by virtue of their lines of action are perfectly positioned to apply compressive load across the glenohumeral joint, and that these muscles contribute most significantly to shoulder joint stability during abduction. The middle deltoid provides most of the compressive force acting between the humeral head and the glenoid, but this muscle also creates most of the shear, and so its contribution to joint stability is less than that of any of the rotator cuff muscles.
Wavelet Analysis of Head Acceleration Response Under Dirac Excitation for Early Oedema Detection
Authors: Kostopoulos V. , Loutas T. H. , Derdas C. , Douzinas E.
Published: April 2008

The present work deals with the application of an innovative in-house developed wavelet-based methodology for the analysis of the acceleration responses of a human head complex model as a simulated diffused oedema progresses. The human head complex has been modeled as a structure consisting of three confocal prolate spheroids, whereas the three defined regions by the system of spheroids, from the outside to the inside, represent the scull, the region of cerebrospinal fluid, and the brain tissue. A Dirac-like pulse has been used to excite the human head complex model and the acceleration response of the system has been calculated and analyzed via the wavelet-based methodology. For the purpose of the present analysis, a wave propagation commercial finite element code, LS-DYNA 3D, has been used. The progressive diffused oedema was modeled via consecutive increases in brain volume accompanied by a decrease in brain density. It was shown that even a small increase in brain volume (at the level of 0.5%) can be identified by the effect it has on the vibration characteristics of the human head complex. More precisely, it was found that for some of the wavelet decomposition levels, the energy content changes monotonically as the brain volume increases, thus providing a useful index of monitoring an oncoming brain oedema before any brain damage appears due to uncontrolled intracranial hypertension. For the purpose of the present work and for the levels of brain volume increase considered in the present analysis, no pressure increase was assumed into the cranial vault and, associatively, no brain compliance variation.
Modeling of Dynamic Fracture and Damage in Two-Dimensional Trabecular Bone Microstructures Using the Cohesive Finite Element Method
Authors: Tomar Vikas
Published: April 2008

Trabecular bone fracture is closely related to the trabecular architecture, microdamage accumulation, and bone tissue properties. Micro-finite-element models have been used to investigate the elastic and yield properties of trabecular bone but have only seen limited application in modeling the microstructure dependent fracture of trabecular bone. In this research, dynamic fracture in two-dimensional (2D) micrographs of ovine (sheep) trabecular bone is modeled using the cohesive finite element method. For this purpose, the bone tissue is modeled as an orthotropic material with the cohesive parameters calculated from the experimental fracture properties of the human cortical bone. Crack propagation analyses are carried out in two different 2D orthogonal sections cut from a three-dimensional 8mm diameter cylindrical trabecular bone sample. The two sections differ in microstructural features such as area fraction (ratio of the 2D space occupied by bone tissue to the total 2D space), mean trabecula thickness, and connectivity. Analyses focus on understanding the effect of the rate of loading as well as on how the rate variation interacts with the microstructural features to cause anisotropy in microdamage accumulation and in the fracture resistance. Results are analyzed in terms of the dependence of fracture energy dissipation on the microstructural features as well as in terms of the changes in damage and stresses associated with the bone architecture variation. Besides the obvious dependence of the fracture behavior on the rate of loading, it is found that the microstructure strongly influences the fracture properties. The orthogonal section with lesser area fraction, low connectivity, and higher mean trabecula thickness is more resistant to fracture than the section with high area fraction, high connectivity, and lower mean trabecula thickness. In addition, it is found that the trabecular architecture leads to inhomogeneous distribution of damage, irrespective of the symmetry in the applied loading with the fracture of the entire bone section rapidly progressing to bone fragmentation once the accumulated damage in any trabeculae reaches a critical limit.