Titanium miniscrews under continuous loading in a Pig jaw: a histological study

There is increasing interest in using titanium miniscrews for orthodontic anchorage. This experimental study aimed to evaluate the histological aspect of mandibular bone around miniscrews subjected to continuous forces in a pig. Three miniscrews were inserted on both sides of a pig mandible. Four weeks after implantation, a coil spring was fixed between two of the right miniscrews, while the left miniscrews remained unloaded. The pig was sacrificed nine weeks after implantation. Two right screws were lost during this period: one loaded screw and the unloaded one. Microradiographic and histological analysis revealed bone apposition in contact of about 1/3 of the unloaded screw surface, whereas the other 2/3 were surrounded by mesenchymal tissue. At distance of the implant, bone underwent important remodeling. No direct screw-bone contact was found around the loaded screw. Bone apposition and resorption were visible at distance of the screw, respectively on its traction and compression sides. In this preliminary study, osseointegration of the unloaded screw appeared more successful than that of the loaded ones. Further studies should be conducted during a longer follow-up period in order to define the degree of minimal osseointegration associated with an efficient anchorage

Microradiographic and histological evaluation of the bone-screw and bone-plate interface of orthodontic miniplates in patients

SummaryObjectives: To describe the tissue reactions at the bone-titanium interface of orthodontic miniplates in humans. Materials and methods: Forty-two samples, consisting of tissue fragments attached or not to miniplates or their fixation screws, were collected from 24 orthodontic patients treated with miniplate anchorage, at the time of removal of their miniplates. The samples were embedded in methylmethacrylate and cut into undecalcified sections which were submitted to microradiographic analysis. The sections were also stained and examined under ordinary light. Results: Three types of reactions were observed both on the histological sections and on the microradiographs. 1. The majority of the stable miniplates were easy to remove (34/42). The tissue samples collected consisted mainly in mature lamellar bone with some medullary spaces containing blood vessels, 2. two screws were highly osseointegrated and required the surgeon to remove them by trephining (2/42). They were surrounded by bone tissue which extended to the miniplate. The histological features were similar to the previous group, though the bone-screw contact was higher, and 3. in six samples obtained after unstable miniplate removal during the treatment, we observed either some woven bone trabeculae or loose connective tissue, without any histological sign of inflammation. Limitations and Conclusion: For evident ethical reasons, our data were limited by the size of the tissue fragments and the limited number of patients and variety of clinical presentations. The healing reactions consisted mainly in mature lamellar bone tissue sparsely in contact with the screw or the miniplate, with signs of a moderate remodelling activit

Root repair after damage due to screw insertion for orthodontic miniplate placement

The aim of this investigation was to describe the healing reactions following root damage caused by placement of a miniplate anchorage system. In 4 beagle dogs, 4 titanium miniplates (2 self-tapping screws per miniplate) were placed in each maxilla, after drilling of pilot-holes. Six fixation screws were unintentionally inserted damaging the root of maxillary canines. Two weeks later, half of the miniplates were loaded with a coil spring. Two dogs were euthanized 7 weeks after placement of the miniplates, while the remaining two after 29 weeks. Histological sections were prepared, microradiographed, observed under U.V. light, then stained and analysed under ordinary light. Four screws caused direct root damage; one was damaged during the drilling process; one caused damage to the periodontal ligament only. Among these 6 screws, 2 were mobile and 4 were stable at sacrifice. Limited root damage showed some repair after 29 weeks, consisting in a thick layer of mineralized cementum including anchoring periodontal fibres. Tissue repair was not related to screw stability or loading status. Limited root damage has shown potential to heal, while extensive root damage has not. Precise position of insertion of the miniplates is thus of utmost importance

Economic hardship and sexually transmitted diseases in Haiti's rural Artibonite Valley.

A study was conducted to determine the prevalence rate and risk factors for sexually transmitted diseases (STDs) in Haiti's rural Artibonite Valley. Women attending antenatal services at Hospital Albert Schweitzer from October to December 1996 were tested for gonorrhea, chlamydia, trichomonas, syphilis, and human immunodeficiency virus (HIV). Of the 476 women tested, 121 (25.4%) had trichomonas, 11/475 (2.3%) had gonorrhea, 51/475 (10.7%) had chlamydia, 32/474 (6.8%) were seropositive for syphilis, 20/469 (4.3%) were seropositive for HIV, and 191 (40.1%) had at least one STD. Nearly 30% of the women reported having entered a sexual relationship out of economic necessity and had increased odds of HIV infection, Odds Ratio (OR) 6.3 (P < 0.001). We postulate that due to recent economic hardship in rural Haiti, women are entering into sexual relationships out of economic necessity and that this trend is contributing to the growing HIV epidemic. We recommend STD prevention and development programs that target young people and economically disadvantaged women

Decellularized vascularized bone grafts: A preliminary in vitro porcine model for bioengineered transplantable bone shafts

Introduction: Durable reconstruction of critical size bone defects is still a surgical challenge despite the availability of numerous autologous and substitute bone options. In this paper, we have investigated the possibility of creating a living bone allograft, using the perfusion/decellularization/recellularization (PDR) technique, which was applied to an original model of vascularized porcine bone graft.Materials and Methods: 11 porcine bone forelimbs, including radius and ulna, were harvested along with their vasculature including the interosseous artery and then decellularized using a sequential detergent perfusion protocol. Cellular clearance, vasculature, extracellular matrix (ECM), and preservation of biomechanical properties were evaluated. The cytocompatibility and in vitro osteoinductive potential of acellular extracellular matrix were studied by static seeding of NIH-3T3 cells and porcine adipose mesenchymal stem cells (pAMSC), respectively.Results: The vascularized bone grafts were successfully decellularized, with an excellent preservation of the 3D morphology and ECM microarchitecture. Measurements of DNA and ECM components revealed complete cellular clearance and preservation of ECM’s major proteins. Bone mineral density (BMD) acquisitions revealed a slight, yet non-significant, decrease after decellularization, while biomechanical testing was unmodified. Cone beam computed tomography (CBCT) acquisitions after vascular injection of barium sulphate confirmed the preservation of the vascular network throughout the whole graft. The non-toxicity of the scaffold was proven by the very low amount of residual sodium dodecyl sulfate (SDS) in the ECM and confirmed by the high live/dead ratio of fibroblasts seeded on periosteum and bone ECM-grafts after 3, 7, and 16 days of culture. Moreover, cell proliferation tests showed a significant multiplication of seeded cell populations at the same endpoints. Lastly, the differentiation study using pAMSC confirmed the ECM graft’s potential to promote osteogenic differentiation. An osteoid-like deposition occurred when pAMSC were cultured on bone ECM in both proliferative and osteogenic differentiation media.Conclusion: Fully decellularized bone grafts can be obtained by perfusion decellularization, thereby preserving ECM architecture and their vascular network, while promoting cell growth and differentiation. These vascularized decellularized bone shaft allografts thus present a true potential for future in vivo reimplantation. Therefore, they may offer new perspectives for repairing large bone defects and for bone tissue engineering

Tuberculosis in Pediatric Antiretroviral Therapy Programs in Low- and Middle-Income Countries: Diagnosis and Screening Practices

Background The global burden of childhood tuberculosis (TB) is estimated to be 0.5 million new cases per year. Human immunodeficiency virus (HIV)-infected children are at high risk for TB. Diagnosis of TB in HIV-infected children remains a major challenge. Methods We describe TB diagnosis and screening practices of pediatric antiretroviral treatment (ART) programs in Africa, Asia, the Caribbean, and Central and South America. We used web-based questionnaires to collect data on ART programs and patients seen from March to July 2012. Forty-three ART programs treating children in 23 countries participated in the study. Results Sputum microscopy and chest Radiograph were available at all programs, mycobacterial culture in 40 (93%) sites, gastric aspiration in 27 (63%), induced sputum in 23 (54%), and Xpert MTB/RIF in 16 (37%) sites. Screening practices to exclude active TB before starting ART included contact history in 41 sites (84%), symptom screening in 38 (88%), and chest Radiograph in 34 sites (79%). The use of diagnostic tools was examined among 146 children diagnosed with TB during the study period. Chest Radiograph was used in 125 (86%) children, sputum microscopy in 76 (52%), induced sputum microscopy in 38 (26%), gastric aspirate microscopy in 35 (24%), culture in 25 (17%), and Xpert MTB/RIF in 11 (8%) children. Conclusions Induced sputum and Xpert MTB/RIF were infrequently available to diagnose childhood TB, and screening was largely based on symptom identification. There is an urgent need to improve the capacity of ART programs in low- and middle-income countries to exclude and diagnose TB in HIV-infected childre

Altérations osseuses microstructurales dans le vieillissement du squelette

L’amélioration des conditions socio-économiques a considérablement accru l’espérance de vie tout en favorisant le développement de troubles dits dégénératifs. Le squelette est un des systèmes sur lesquels les années pèsent le plus lourdement. Ainsi, entre 20 et 80 ans, l’ostéopénie physiologique (Pommer, 1925 ; Amprino et Bairati, 1936) est estimée à 27% chez l’homme et à 40% chez la femme, la ménopause produisant une accélération de la raréfaction osseuse entre 55 et 65 ans (Courpon et coll., 1973 ; Meunier, 1986 ; Riggs et Melton, 1986). Quad l’ostéopénie s’aggrave au point d’entraîner un risque accru d fracture, même après un traumatisme mineur, elle est considérée comme une maladie, l’ostéoporose d’involution (Meuner, 1986 ; Riggs et Melton, 1986 ; Melton et coll., 1988). Ce syndrome se manifeste sous deux formes. Le type I, ou postménopausique (Riggs et coll., 1983 ; Riggs, 1987), est attribué au déficit en œstrogènes. Il est caractérisé par une destruction accélérée et disproportionnée de tissu osseux spongieux. Les tassements vertébraux en sont la conséquence clinique. Il en découle une réduction de la sécrétion d’hormone parathyroïdienne, de la production de dihydroxycholécalciférol et, de ce fiat, de l’absorption du calcium (Heaney et coll., 1982 ; Riggs et coll., 1983). L’ostéoporose de type II ou sénile, uniquement due à l’âge, mène à une déplétion équivalente de l’os spongieux et de l’os cortical et frappe particulièrement le col fémoral (Riggs, et coll., 1983 ; Riggs et Melton, 1986). Elle est attribuée non seulement à une réduction de l’activité ostéoblastique (Lips et coll., 1978) mais aussi une diminution de la disponibilité de la vitamine D (Gallagher et coll., 1979), ce qui contribue à une absorption moins efficace du calcium (Nordin, 1960 ; Bullamore et coll., 1970) et entraîne une riposte sécrétoire de parathormone (Wiske et coll., 1979 ; Gallagher et coll., 1980 ; Heaney et coll., 1982). La progression asymptomatique de l’ostéoporose d’involution et l’atteinte du nombre croissant d’individus lui ont valu le surnom d’épidémie silencieuse (Geusens, 1992). L’évolution clinique est émaillée d’épisodes de fractures, mais elle est aussi marquée, plus insidieusement, par une altération de la qualité de la vie dans ses dimensions physiques, psychologiques et sociales (Thévenon et coll., 1994 ; Riggs et Melton, 1995). la raréfaction osseuse est responsable d’un risque accru de fracture étant donné que la masse rend compte de la résistance mécanique dans une proportion de l’ordre de 75 à 85% (Smith et Smith, 1976 ; Mazess, 1982 ; Melton et coll., 1988 ; Moseklide, 1993). Cette association a été démontrée dans différents sites comme le col féroral (Dalén et coll., 1976 ; Delaere et coll., 1989 ; Houde et coll., 1995), les vertèbres lombales (Weaver et Chalmers, 1966 ; Bell et coll., 1967 ; Galante et coll., 1970 ; Hansson et coll., 1980 ; Moekilde et coll., 1987 ; Eriksson et coll., 1989 ; Vesterby et coll., 1991), el plateau tibial (Carter et Hayes, 1976) ou le calcanéus (Weaver et Chalmers, 1966). Le parallélisme entre l’importance de l’ostéopénie et la fragilité liée à la perte des propriétés mécaniques n’est pas absolu (Bell et coll., 19967 ; Wall et coll., 1979 ; Riggs et Melton, 1986 ; Geusens, 1992 ; Heaney, 1993). En effet, des fractures surviennent chez certains patients dont le capital osseux est normal pour l’âge (Wicks et coll., 1982 ; Cummings, 1985) tandis qu’elles en épargnent d’autres qui, sur base des mêmes critères seraient rangés parmi les personnes à haut risque (Hansson et coll., 1980 ; Mazess, 1990). D’autres facteurs, extra- et intra-osseux, interviennent donc dans la fragilisation du squelette. Les contingences extra-osseuses comprennent, notamment, une propension à tomber, une altération des réflexes posturaux lors d’une chute et une raréfaction des tissus mous au point d’impact (Cummings, 1985 ; Heaney, 1993). Des caractéristiques intra-osseuses, comme la qualité du remaniement, la structure tridimensionnelle de l’os et sa capacité d’adaptation à des charges spécifiques, sont également susceptibles d’influencer sa résistance mécanique (Bell et coll., 1967 ; Pugh et coll., 1973a ; Wagner et coll., 1991 ; Parfitt, 1984b ; Kleerekoper et coll., 1985 ; Delaere et coll., 1989 ; Vesterby et coll., 1991 ; Mosekilde, 1993 ; Compston, 1994). Avec l’âge, celle-ci peut être compromise par des perturbations de la qualité du tissu suite à une modification du réseau trabéculaire, à une réduction d’élasticité de la matrice collagénique, à des variations dans la géométrie de la phase minérale, à la fragilité accrue de l’os sénescent hyperminéralisé (Frost, 1985 ; Moseklide et coll., 1987) ou, enfin, à l’accumulation de microlésions, dont la réparation est moins efficace qu’au début de la vie adulte (Melton et coll., 1988). La définition actuelle de l’ostéoporose, qui intègre ce conet de perte de qualité, structurale ou mécanique (Frost, 1985 ; Geusens 1992 ; Johnston et Slemenda, 1995), témoigne d’une approche plus large que celle de la masse osseuse considérée isolément. L’intégrité squelettique est également essentielle dans la notion de longévité des systèmes de fixation, dont l’arthroplastie totale de la hanche (Stulberg et coll. 1989), d’autant plus que les prothèses sont, en majorité, placées chez des patients de plus de 50 ans. <BR La présence monographie vise à passer en revue les principales connaissance actuelles concernant la rôle des altérations microscopiques qualitatives dans la fragilisation du squelette liée à l’âge et à montrer comment nos données personnelles y ont contribué. Nous avons basé nos travaux sur l’os humain en lui appliquant les techniques d’étude morphologique appropriées, comme la microradiographie, l’histomorphométrie, la photodensitométrie et la microscopie électronique à balayage, dont les procédures sot résumées en annexesThèse d'agrégation de l'enseignement supérieur (Faculté de médecine) -- UCL, 199