Biodistribution of titanium dioxide from biologic compartments.

The layer of titanium dioxide (TiO(2)) of the implant is chronically exposed to the internal electrolyte milieu in the peri-implant biological compartment. Corrosion results from electrochemical attack and ensuing gradual degradation of the metallic materials and is thus of biological interest when these biomaterials are employed in clinical implantology. Herein we evaluated and compared the chronic effect and the biodistribution of TiO(2) administered subcutaneously or intraperitoneally. We propose that the compartmentalization of titanium in the area of subcutaneous injection would reproduce the biological compartment of the implant and its microenvironment from which metal ions could be released and migrate systemically. Potential TiO(2) deposits were identified and characterized in skin, liver and lung by histological and EDX analyses. After both treatments, the skin, liver, and lungs exhibited histological evidence of TiO(2) deposits. In order to characterize in situ macrophage-like cells, tissue sections were immunohistochemically stained for CD68. Tissue specimens from all organs assayed showed positive staining for anti-macrophage monoclonal antibody CD68 (PGM1). Despite the compartmentalization of titanium within nodular areas in rats treated subcutaneously, systemic migration occurred. We concluded that systemic migration of TiO(2) occurred regardless of the administration route.

Electrical field effect on peri-implant osteogenesis: a histologic and histomorphometric study.

PURPOSE: Tissue response to injury, as occurs during wound healing, is a well-organized biologic event. Both clinical and experimental studies have shown external electrical stimulation to enhance tissue repair. The effect of in situ electrical stimulation has been studied in experimental models of fracture healing, ostectomy, osteogenic distraction, and implants. The aim of the present study was to evaluate the effect of an electrical field on peri-implant wound healing, using an experimental model that involved placing a metallic laminar implant in rat tibia. MATERIALS: Forty male Wistar rats weighing approximately 100 g were used. A titanium laminar implant (6 x 1 x 0.1 mm3) (Implant Vel, Buenos Aires, Argentina) was inserted through the hole and placed in the medullary compartment. The tissues were then repositioned and sutured carefully. An electric field generator (ECCEL, DAM, Argentina) was used to deliver the electric stimulus. The electric field plate was placed on the skin of both hind limbs. In sham group, the animals were subjected to the same procedure without connecting the plate to the electric field generator. All the animals were killed by ether overdose at 15 days of postimplantation. The tibiae were resected, fixed in 20% formalin, radiographed, and processed for embedding in methyl methacrylate. The ground sections were stained with 1% toluidine blue. The following parameters were evaluated: peri-implant bone volume and percentage of osseointegration. Statistical analysis of the results was performed using ANOVA (P < 0.05). RESULTS: Application of external positive or negative electrical fields using the experimental model (post-titanium implant bone healing in rat tibia), under the conditions stated herein, was found to enhance peri-implant lamellar bone volume compared with sham-treated animals. CONCLUSION: The use of a device generating a positive/negative electrical field resulted in the presence of woven bone.

Effect of platelet-rich plasma on the peri-implant bone response: an experimental study.

Platelet-rich plasma (PRP) is used as a source of growth factors to stimulate and accelerate bone formation and soft tissue healing. The use of PRP in bone regeneration, both around dental implants and in periodontic treatments, has become particularly appealing. The aim of this study was to evaluate the effect of PRP in an experimental model of osteogenesis around laminar implants. Fifteen male Wistar rats, weighing 90 +/- 10 g, were used in this study. One milliliter of blood was obtained from each animal by intracardiac puncture and transferred into Eppendorf tubes containing 10% sodium citrate. The tubes were centrifuged at 1500 rpm for 15 minutes and PRP was prepared. The laminar test was used to evaluate the bone peri-implant response. PRP and a titanium laminar implant were introduced into the right tibia (Ti/PRP group), whereas the left tibia (control) received only a laminar implant (Ti group). Thirty days postimplantation, the tibiae were resected, radiographed, and processed for embedding in acrylic resin. Ground sections (50 microm) were stained with toluidine blue. The peri-implant bone volume was evaluated histomorphometrically. Statistical analysis of the data was performed. The amount of newly formed bone in the Ti/PRP group (30 +/- 7 cm) was significantly greater than in the Ti group (16 +/- 3 cm). A greater volume of peri-implant bone was observed when PRP was used in the laminar implant test model.

Histomorphometric evaluation of the effect of bovine collagen granules on bone healing: an experimental study in rats

La biocompatibilidad del colágeno determinó la utilización del mismo como material de implante. El objetivo del presente estudio fue evaluar histomorfométricamente los efectos de gránulos de colágeno bovino en un modelo experimental de cicatrización ósea postextracción dentaria. Se utilizaron 20 ratas Wistar machos. Bajo anestesia, se procedió a la exodoncia de los primeros molares inferiores seguiendo la metodología descripta por Guglielmotti y Cabrini. En el alvéolo mesial derecho se implantaron gránulos de colágeno bovino de aproximadamente 80 +- 10 um (Membracel G., Lab. Celina, Buenos Aires) vehiculizados con solución fisiológica estéril. Los alvéolos contralaterales se utilizaron como control. No se realizó sutura ni se administró antibióticoterapia. A los 30 días postextracción se resecaron las mandíbulas, se fijaron en formol al 10 por ciento, radiografiaron, decalcificaron y procesaron para su posterior inclusión en parafina. Se realizaron cortes orientados en sentido vestíbulo-lingual a nivel del alvéolo mesial y se colorearon con hematoxilina-eosina. Se evaluó histomorfométricamente el volumen óseo total y la densidad ósea en el tercio apical del alvéolo. Los alvéolos donde se utilizó gránulos de colágeno como material de implante evidenciaron mayor volumen de tejido óseo neoformado y mayor densidad ósea con respecto a los alvéolos control (P<0,05). Los resultados obtenidos en este modelo experimental permitirían establecer que la utilización de gránulos de colágeno bovino no interfiere el proceso de cicatrización ósea postextracción dentaria.

Histomorphometric evaluation of the effect of bovine collagen granules on bone healing: an experimental study in rats

La biocompatibilidad del colágeno determinó la utilización del mismo como material de implante. El objetivo del presente estudio fue evaluar histomorfométricamente los efectos de gránulos de colágeno bovino en un modelo experimental de cicatrización ósea postextracción dentaria. Se utilizaron 20 ratas Wistar machos. Bajo anestesia, se procedió a la exodoncia de los primeros molares inferiores seguiendo la metodología descripta por Guglielmotti y Cabrini. En el alvéolo mesial derecho se implantaron gránulos de colágeno bovino de aproximadamente 80 +- 10 um (Membracel G., Lab. Celina, Buenos Aires) vehiculizados con solución fisiológica estéril. Los alvéolos contralaterales se utilizaron como control. No se realizó sutura ni se administró antibióticoterapia. A los 30 días postextracción se resecaron las mandíbulas, se fijaron en formol al 10 por ciento, radiografiaron, decalcificaron y procesaron para su posterior inclusión en parafina. Se realizaron cortes orientados en sentido vestíbulo-lingual a nivel del alvéolo mesial y se colorearon con hematoxilina-eosina. Se evaluó histomorfométricamente el volumen óseo total y la densidad ósea en el tercio apical del alvéolo. Los alvéolos donde se utilizó gránulos de colágeno como material de implante evidenciaron mayor volumen de tejido óseo neoformado y mayor densidad ósea con respecto a los alvéolos control (P<0,05). Los resultados obtenidos en este modelo experimental permitirían establecer que la utilización de gránulos de colágeno bovino no interfiere el proceso de cicatrización ósea postextracción dentaria. (AU)

A histologic study of bone response to bioactive glass particles used before implant placement: a clinical report.

This clinical report describes the microscopic analysis of the postextraction bone response to bioactive glass particles used prior to titanium implant placement, after a healing period of 6 months. The clinical and radiographic follow-up were performed over a 3-year period after implantation.

Periimplant bone healing under experimental hepatic osteodystrophy induced by a choline-deficient diet: a histomorphometric study in rats.

BACKGROUND: Osseointegration and success of an implant involve the interaction of local and systemic factors such as bone metabolic diseases. PURPOSE: The purpose of this study was to evaluate the effect of experimental hepatic osteodystrophy induced by a choline-deficient diet on periimplant bone healing. MATERIALS AND METHODS: Laminar titanium implants were placed in the tibias of five groups of Wistar rats: those with a (1). controlled diet for 15 days; (2). choline-deficient diet for 15 days; (3). controlled diet for 30 days; (4). choline-deficient diet for 30 days; (5). choline-deficient diet for 15 days and a controlled diet for 15 days (refeeding). Body weight and food intake, hematocrit, and hemoglobinemia were evaluated. The animals were killed at 15 or 30 days post implantation. The liver, kidneys, and tibias were resected and fixed in 20% formalin solution. The tibias were radiographed and processed for histomorphometric evaluation of the periimplant bone area. RESULTS: Histologic studies revealed steatosis in the liver but no alterations in the kidneys. Rats fed a choline-deficient diet showed periimplant bone healing with marked qualitative and quantitative alterations. The periimplant bone area was 28% and 75% lower in experimental animals than in controls at 15 and 30 days, respectively. CONCLUSIONS: Liver alterations caused by a choline-deficient diet alter periimplant osteogenesis qualitatively and quantitatively.

Macrophages related to dental implant failure.

PURPOSE: The aim of this study was to evaluate, histologically and quantitatively, the presence of macrophages loaded with metallic particles in the periimplant soft tissues of failed titanium (Ti) dental implants. MATERIALS AND METHODS: The study was performed on sections of metallic Ti implants embedded in methyl methacrylate resin that exhibited macrophages in the soft tissues contiguous with the implant. The volume of periimplant soft tissue was evaluated, and the number of macrophages was determined. The particles within macrophages were analyzed by energy-dispersive x-ray analysis. RESULTS: Macrophages were more abundant in the zone adjacent to the metallic implant as compared with the zone further away from the implant. Energy-dispersive x-ray analysis revealed the presence of Ti within macrophages. CONCLUSIONS: Macrophages loaded with Ti particles can be associated with a corrosion process. The method proposed would allow for the objective evaluation of the presence of macrophages associated with dental implants and other orthopedic materials that contain Ti or other metals.

3.1 Scholarship and the university.

Universities now exist in an environment of increasing accountability for their academic performance, both in teaching and research. Dental schools are expected to meet the academic expectations of their parent university and, in addition, to contribute to the health-care needs of the community. Individual staff members must achieve collectively the performance targets required of their school and individually must develop skills and expertise in their academic and clinical activities to merit tenure and promotion. This discussion examines the issues which impact on current problems of recruitment and retention of academic staff in dental schools internationally. The essential issue is career development in a manner which maintains the values that will ensure the credibility of dentistry as a scientifically based discipline and profession, while balancing the achievable academic needs with the added demands of achieving specialist clinical skills. Central to this balance is recognition that scholarship, which provides the bridge between research and teaching, can be broadly defined and that different individuals can be scholarly in a range of ways. Increasingly, schools are recognizing the importance of providing structured opportunities and guidance for career development of younger staff and of the need for flexibility in their criteria for tenure and promotion, recognizing that a diversity of individual strengths and teamworking are necessary both for the collective performance of the institution and the morale and development of the individual.

An experimental study of the dissemination of Titanium and Zirconium in the body.

Metallic implants can generate and release titanium oxide (TiO(2)) and zirconium oxide (ZrO(2)) to the tissues. These products can accumulate locally or disseminate systemically. The aim of the present study was to assess the distribution of TiO(2) and ZrO(2) administered intraperitoneally to rats. We used male Wistar rats of approximately 100 g body weight throughout the study. An intraperitoneal injection of a suspension of TiO(2) or ZrO(2) (16, 1600 and 16 x 10(3) mg/kg body weight) was administered. The animals were killed at 5-10 months post-administration by ether overdose. Samples of peritoneum, liver, kidney, lung and spleen were taken, fixed in formalin and routine processed for embedding in paraffin. One set of sections was stained with hematoxylin and eosin and another set was prepared unstained. The presence of titanium in the tissues was detected by X-ray diffraction crystallography. The histological analysis revealed the presence of abundant intracellular aggregates of metallic particles of Ti and Zr in peritoneum, liver, lung and spleen. The crystallographic study revealed the presence of anatasa. The dissemination of metallic particles from orthopedic or odontological implants would not be restricted to a local phenomenon. The particles also target vital organs. The distribution of these deposits over lengthy periods deserves meticulous attention given the clinical relevance of this phenomenon.