Bone Substitutes
Notice bibliographique
Résumé
Implant Dentistry -The Most Promising Discipline of Dentistry 92 provides biologic signals capable to induce local cells to enter a pathway of differentiation leading to mature osteoblasts.An osteoconductive biomaterial provides a three-dimensional interconnected scaffold where local bone tissue may regenerate new living bone.However, osteoconductive biomaterials are unable to form bone or to induce its formation.Another property that is interesting to find especially in bone substitutes is biodegradability.This is defined as the capacity of degradation of a particle by two mechanisms principally; through a passive chemical degradation or dissolution, and through active cellular activity mediated by osteoclast and/or macrophages.Moreover, the biological properties of bone substitute biomaterials are also influenced by their porosity, surface geometry and surface chemistry.The events leading to bone healing and regeneration are influenced by all the variables mentioned above.These properties are related to the biomaterial itself, however, host factors such as bone quality, vascularity of the graft bed and tobacco addiction may also influence the final outcome of a bone regeneration procedure with a bone substitute. Biomaterials used for bone regeneration in implant dentistryBone graft materials can be divided in four large groups: Autografts, Allografts, Xenografts and Synthetic biomaterials. Autograft"Autograft" refers to bone tissue harvested from, and implanted in the same individual.Accordingly, autograft is a bone tissue that is separated from one site and implanted in other location in the same individual.The cellular component of trabecular bone graft includes few osteoblasts and a high number of precursor cells that survive the transplantation.These precursor cells explain the osteogenic potential of bone autograft.Autograft is considered the "gold standard" in bone regeneration due to its properties of osteoconduction, osteoinduction, osteogenicity and osteointegration.However there are major drawbacks to the use of this sort of ideal bone graft, namely the necessity of a second surgery to retrieve the bone graft at the donor site, with its associated morbidity; the increasing surgery time, the restrictions in quantity and shape of the bone graft, and the additional cost (Arrington, 1996;Giannoudis, 2005).Autografts are subdivided in two groups: cancellous autografts and cortical autografts.Cancellous autografts are retrieved mainly from calcellous bone, and upon transaplantation, the majority of cells presnet in the grafts die as result of ischemia.However, the mesenchymal stem cells present in the bone marrow are resistant to ischemia and may survive the grafting procedure.The stem cells capacity of survival and proliferation after exposure to changes in the oxygen tension, pH and cytochine environment are the main reason behind the reliability of of cancellous bone autograft interventions.The incorporation of such type of autogrfraft is speed, about 8 weeks (Virolainen, 1995).Cortical autografts are segments of cortical bone composed of necrotic bone that provides an osteoconductive support for bone formation, but does not supply significant amounts of living cells.For this reason, revascularization and integration of cortical autografts is slow.The main advantage of cortical autografts is the mechanical support that provides at the graft site (Bauer & Muchler, 2000), while its incorporation is slower than cancellous autografts.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,001 | 0,001 |
| Méta-épidémiologie (sens strict) | 0,001 | 0,000 |
| Méta-épidémiologie (sens large) | 0,001 | 0,001 |
| Bibliométrie | 0,002 | 0,002 |
| Études des sciences et des technologies | 0,001 | 0,001 |
| Communication savante | 0,002 | 0,001 |
| Science ouverte | 0,001 | 0,002 |
| Intégrité de la recherche | 0,002 | 0,001 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,105 | 0,065 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».