Calcifying odontogenic cyst associated with compound odontoma: A study on undemineralized material

In a minority of cases of calcifying odontogenic cyst (COC) it is possible to observe the formation of dental hard tissues in the cyst wall. The use of undemineralized sections has allowed an evaluation of the mineralized tissues normally lost with the use of demineralizing agents. All the dental hard tissues presented a high degree of morpho- and histodifferentiation. The histochemical staining for calcium salts (von Kossa) showed the presence of areas of low mineralization in the portion of the lesion, where the tissue maturation was not complete. In conclusion the appearance of the dental hard tissues in this case of compound odontoma arising in the cyst wall of a COC is similar to that already described in compound odontoma not associated with COC.Il est possible d’observer la formation de tissus dentaires durs dans la paroi d’une minorité de cas de kystes odontogènes calcifiants (KOC). L’utilisation de coupes de tissus non déminéralisés a permis une évaluation des tissus minéralisés qui sont habituellement perdus après décalcification. Tous les tissus dentaires durs présentent un degré important de morpho- en d’histodifférenciation. La coloration histochimique des sels calcaires (von Kossa) montre la présence de territoires de faible minéralisation dans les régions dans lesquelles la maturation tissulaire est incomplète.En conclusion, l’apparence des tissus dentaires durs dans ce cas d’odontome composé développé dans la paroi d’un kyste odontogène calcifié est semblable à celle déjà décrite dans les odontomes composés non associé à un KOC

SEM and fractography analysis of screw thread loosening in dental implants.

Biological and technical failures of implants have already been reported. Mechanical factors are certainly of importance in implant failures, even if their exact nature has not yet been established. The abutment screw fracture or loosening represents a rare, but quite unpleasant failure. The aim of the present research is an analysis and structural examination of screw thread or abutment loosening compared with screw threads or abutment without loosening. The loosening of screw threads was compared to screw thread without loosening of three different implant systems; Branemark (Nobel Biocare, Gothenburg, Sweden), T.B.R. implant systems (Benax, Ancona, Italy) and Restore (Lifecore Biomedical, Chaska, Minnesota, USA). In this study broken screws were excluded. A total of 16 screw thread loosenings were observed (Group I) (4 Branemark, 4 T.B.R and 5 Restore), 10 screw threads without loosening were removed (Group II), and 6 screw threads as received by the manufacturer (unused) (Group III) were used as control (2 Branemark, 2 T.B.R and 2 Restore). The loosened abutment screws were retrieved and analyzed under SEM. Many alterations and deformations were present in concavities and convexities of screw threads in group I. No macroscopic alterations or deformations were observed in groups II and III. A statistical difference of the presence of microcracks were observed between screw threads with an abutment loosening and screw threads without an abutment loosening

Ultrastructural analysis of periapical granulomas

A large portion of periapical granulomas is composed by cells of the mononuclear-phagocyte and lymphoid system. The ultrastructural features of the monocytes/macrophages differ in relationship to the state of activity of the cells (phagocytosis or secretion). A close correlation between cells of these two systems can be surmised by their tight contacts. An important role in the bone resorption is probably played by cytokines like IL-1 and TNF.Une grande partie des granulomes périapicaux est constituée de cellules du système mononucléaire phagocytaire et lymphoïde. Les caractéristiques ultrastructurales des monocytes/macrophages diffèrent selon le type d’activité des cellules (phagocytose ou sécrétion). Une corrélation intime entre les cellules de ces deux systèmes peut être supposée étant donné leurs contacts serrés. Un rôle important dans la résorption osseuse est exercé, probablement par l’intermédiaire de cytokines comme IL-1 beta et TNF

Ghost cells in compound odontoma: a study of undemineralized material

Calcifications and ghost cells at the enamel surface or in the ameloblastic epithelium were studied in twelve odontomas using undemineralized material.Calcified material formed focally in the intercellular portion of the enamel epithelium: this material showed a concentric layers arrangement.Ghost cells were present in most of the odontomas.These ghost cells were epithelial cells which enlarged, became eosiniphilic and underwent an aberrant type of keratinization with the formation of large masses of keratin, that didn’t stain as deeply as normal keratin. These cells often showed karyolysis of the nucleus as keratinization progressed. Frequent was the appearance of dystrophic calcifications in individual cells or clusters of cells, characterized by extremely fine basophilic granularity. The outlines of these keratinized cells could often still be discerned, even if with some difficulty.Les calcifications et les cellules fantômes à la surface de l’émail ou dans l’épithélium améloblastique ont été étudiées dans 12 odontomes en utilisant du matériel non décaldfié.Le matériel calcifié est formé focalement dans les portions intercellulaires de l'épithélium de l'émail: ce matériel montre un agencement en couches concentriques.Les cellules fantômes sont présentes dans la plupart des odontomes. Ces cellules fantômes sont des cellules épithéliales qui augmentent de taille, deviennent éosinophiles et subissent un type aberrant de kératinisation avec formation de larges masses de kératine qui ne se colorent pas aussi intensément que la kératine normale. Ces cellules montrent souvent une karyolyse du noyau au fur et à mesure de la progression de la kératinisation. Il était fréquent de rencontrer l’apparition de calcifications dystrophiques dans des cellules isolées ou en îlots, caractérisées par des granulations basophiles extrêmement fines. Les contours de ces cellules kératinisées peuvent être encore souvent discernés, quoique avec certaines difficultés

Underwater Laboratories for Astroparticle Physics and Deep Sea Science

The exploration of deep sea environments is presently at the dawn of a new era: underwater laboratories, permanently installed on the sea floor and offering power and on-line data transmission links to the shore, will allow to continuously monitor oceanographical properties. An important boost in this direction has been provided by the high energy physics scientific community, that aims at the realization of an underwater detector for cosmic high energy neutrinos. Neutrinos are considered a very promising probe for high energy astrophysics and many indications suggest that some of the most energetic sources known in the universe could also be high energy neutrino sources. The expected neutrino fluxes indicate that a km3-scale detector must be realised to achieve this ambitious aim. The quest for the realization of such a detector in the Mediterranean Sea has already started

Graphene-based nanomaterials for tissue engineering in the dental field

The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedure

The emerging role of cold atmospheric plasma in implantology: A review of the literature

In recent years, cold atmospheric plasma (CAP) technologies have received increasing attention in the field of biomedical applications. The aim of this article is to review the currently available literature to provide an overview of the scientific principles of CAP application, its features, functions, and its applications in systemic and oral diseases, with a specific focus on its potential in implantology. In this narrative review, PubMed, Medline, and Scopus databases were searched using key words like “cold atmospheric plasma”, “argon plasma”, “helium plasma”, “air plasma”, “dental implants”, “implantology”, “peri‐implantitis”, “decontamination”. In vitro studies demonstrated CAP’s potential to enhance surface colonization and osteoblast activity and to accelerate mineralization, as well as to determine a clean surface with cell growth comparable to the sterile control on both titanium and zirconia surfaces. The effect of CAP on biofilm removal was revealed in comparative studies to the currently available decontamination modalities (laser, air abrasion, and chlorhexidine). The combination of mechanical treatments and CAP resulted in synergistic antimicrobial effects and surface improvement, indicating that it may play a central role in surface “rejuvenation” and offer a novel approach for the treatment of peri‐implantitis. It is noteworthy that the CAP conditioning of implant surfaces leads to an improvement in osseointegration in in vivo animal studies. To the best of our knowledge, this is the first review of the literature providing a summary of the current state of the art of this emerging field in implantology and it could represent a point of reference for basic researchers and clinicians interested in approaching and testing new technologies

Light and Laser Scanning Microscopy analysis of hydroxyapatite used in periodontal osseous defects in man: evidence of a different resorption pattern in bone and soft tissues

Hydroxyapatite (HA) is a highly biocompatible material that recently has been shown to undergo biodegradation. The mechanisms of this phenomenon are unclear, and humoral and cellular events have been thought to be implicated. In the present study HA particles were put into infraosseous defects on teeth that were to be extracted for prosthetic reasons and then retrieved after a 1 year period. The specimens were processed with the cutting grinding system. Results show a very sharp difference of the biodegradation processes, related to the tissues that surround the HA particles. HA in tight contact with mineralized bone showed no evidence of degradation or resorption, while on the contrary, in the areas where bone loose connective tissue was present, it was possible to observe HA crystals detached and scattered in cells cytoplasm or extracellular fluids. This dissolution and resorption phenomenon were observed also by Laser Scanning Microscope (LSM) in fluorescent mode. These differences in degrees of degradation between bone and loose connective tissue could be due to the small amount of interstitial fluid present in mineralized bone and the greater flow of fluid through connective tissue.L’hydroxyapatite (HA) est un matériel hautement biocompatible qui s’est révélé récemment capable de subir une biodégradation. Le mécanisme de ce phénomène n’est pas clair, et semble impliquer une particination humorale et cellulaire. Notre recherche a porté sur la mise en place de particules d’HA dans des défects intraosseux en rapport avec des dents qui doivent être extraites pour des raisons prothésiques, et sur leur etude suite à leur ablation un an après. Les résultats ont démontré des différences marquées dans le processus de dégradation en rapport avec les tissus qui entourent l’HA. Les particules d’HA qui sont en contact avec l’os minéralisé ne présentent pas de signes de dégradation ou de résorption, tandis que dans les régions où du tissu conjonctif était présent, il est possible d’observer des cristaux d’HA détachés et dispersés dans le cytoplasme des cellules et dans le liquide extracellulaire. Ces phénomènes de dissolution et de résorption ont été également étudiés au Microscope Electronique à Balayage au Laser en fluorescence. Ces différences dans le degré de dégradation observés dans l’os et dans le tissu conjonctif lâche pourraient être dues à la faible quantité de liquide interstitiel dans l’os minéralisé et à la quantité plus grande de flux liquidien dans le tissu conjonctif

Three-dimensional architecture and mechanical properties of bovine bone mixed with autologous platelet liquid, blood, or physiological water: An in vitro study

In recent years, several techniques and material options have been investigated and developed for bone defect repair and regeneration. The progress in studies of composite graft materials and autologous platelet-derived growth factors for bone regeneration in dentistry and their biological and biomechanical properties has improved clinical strategies and results. The aim of this study was to evaluate the three-dimensional architecture and mechanical properties of three different combinations of composite bovine graft, adding autologous platelet liquid (APL), blood, or physiological water. One experimental group for each combination of biomaterials was created. In particular, in Group I, the bovine graft was mixed with APL; in Group II, it was mixed with blood, and in Group III, the biomaterial graft was combined with physiological water. Then, the composite biomaterials were evaluated by scanning electron microscopy (SEM), and a compression-loading test was conducted. The evaluation showed a statistical significance (p < 0.01) of the elastic regime of deformation resistance, in which the combination of APL with bone graft resulted in an 875% increase in the mechanical resistance. The protocol of APL mixed with bovine bone graft produced a composite sticky graft block that was capable of increasing the mechanical properties in order to improve its clinical use in the treatment of the maxillary bone defects