Research on implants and osseointegration.

Osseointegration was originally defined as a direct structural and functional connection between ordered living bone and the surface of a load-carrying implant. It is now said that an implant is regarded as osseointegrated when there is no progressive relative movement between the implant and the bone with which it is in direct contact. Although the term osseointegration was initially used with reference to titanium metallic implants, the concept is currently applied to all biomaterials that have the ability to osseointegrate. Biomaterials are closely related to the mechanism of osseointegration; these materials are designed to be implanted or incorporated into the living system with the aims to substitute for, or regenerate, tissues and tissue functions. Objective evaluation of the properties of the different biomaterials and of the factors that influence bone repair in general, and at the bone tissue-implant interface, is essential to the clinical success of an implant. The Biomaterials Laboratory of the Oral Pathology Department of the School of Dentistry at the University of Buenos Aires is devoted to the study and research of the properties and biological effects of biomaterials for dental implants and bone substitutes. This paper summarizes the research work resulting from over 25 years' experience in this field. It includes studies conducted at our laboratory on the local and systemic factors affecting the peri-implant bone healing process, using experimental models developed by our research team. The results of our research on corrosion, focusing on dental implants, as well as our experience in the evaluation of failed dental implants and bone biopsies obtained following maxillary sinus floor augmentation with bone substitutes, are also reported. Research on biomaterials and their interaction with the biological system is a continuing challenge in biomedicine, which aims to achieve optimal biocompatibility and thus contribute to patient health.

Tissue response to porous high density polyethylene as a three-dimensional scaffold for bone tissue engineering: An experimental study.

High density polyethylene (HDPE) is a synthetic biomaterial used as a three-dimensional scaffold for bone defect reconstruction. Reports differ with regard to its biological response, particularly its osteoconductive capacity. The aim of the present work was to histologically and histomorphometrically evaluate tissue response to porous HDPE. An in vivo study was conducted in rat tibia to evaluate osteogenic capacity, angiogenesis, inflammatory response, and the presence of multinucleated giant cells 14 and 60 days post-biomaterial implantation. Histological examination 14 days post-implantation showed fibrovascular tissue inside pores and on the surface of porous HDPE, acute inflammatory response, scant multinucleated giant cells (MNGCs), and lamellar bone in contact with the biomaterial. An increase in the proportion of lamellar bone tissue, no inflammatory response, and a decrease in the number of MNGCs were observed at 60 days. The histomorphometric study showed a significant time-dependent increase both in the area of bone tissue formed in contact with the porous HDPE (14d: 24.450 ± 11.623 µm2 vs. 60d: 77.104 ± 26.217 µm2, p < 0.05) and in the percentage of bone tissue in contact with the porous HDPE (osseointegration). A significant decrease in the number of MNGCs was also observed at 60 days post-implantation. Porous HDPE showed adequate osteoconductive properties, and only caused an initial inflammatory response. Although this biomaterial has traditionally been used juxtaosseoulsy, its adequate osteoconductive properties broaden the scope of its application to include intraosseous placement.

Titanium Nanoparticle Size Influences Trace Concentration Levels in Skin Appendages.

As a result of biotribocorrosion, the surface of a titanium (Ti) biomedical device can be a potential source of systemic contamination with Ti nanoparticles (NPs). Although NPs can be chemically similar, differences in particle size may lead to different biological responses. The aim of this experimental study was to determine Ti trace levels in skin appendages and plasma and explore the influence of NP size on trace levels using a murine model. Results showed the presence of Ti traces in the nails, hair, and plasma. The concentration of the smallest NPs (5 Nm) was higher than that of 10 Nm NPs in all the studied samples. Irrespective of NP size, Ti levels were always lower in plasma than in skin appendages. Ti levels were higher in nails than in hair. Ti NPs size influenced trace concentration levels in hair/nails, suggesting that 5 Nm Ti particles are more easily eliminated through these skin appendages. Given that the nails showed the highest levels of Ti, and that these skin appendages are not exposed to agents that can leach out Ti, as occurs with hair, we propose the nails as the most suitable and reliable bioindicator for monitoring systemic contamination with Ti.

Biokinetics and tissue response to ultrananocrystalline diamond nanoparticles employed as coating for biomedical devices.

Although Ultrananocrystalline diamond (UNCD) has been proposed as a coating material for titanium biomedical implants, the biological effects and toxicity of UNCD particles that could eventually detach have not been studied to date. The biokinetics and biological effects of UNCD compared to titanium dioxide (TiO2 ) nanoparticles was evaluated in vivo using Wistar rats (n = 30) i.p. injected with TiO2 , UNCD or saline solution. After 6 months, blood, lung, liver, and kidney samples were histologically analyzed. Oxidative damage by membrane lipidperoxidation (thiobarbituric acid reactive substances-TBARS), generation of reactive oxygen species (superoxide anion- O2-), and antioxidant enzymes (superoxide dismutase-SOD, catalase-CAT) was evaluated in lung and liver. Histologic observation showed agglomerates of TiO2 or UNCD in the parenchyma of the studied organs, though there were fewer UNCD than TiO2 deposits. In addition, TiO2 caused areas compatibles with foci of necrosis in the liver and renal hyaline cylinders. Regarding UNCD, no membrane damage (TBARS) or mobilization of enzymatic antioxidants was observed either in lung or liver samples. No variations in O2- generation were observed in lung (Co: 35.1 ± 4.02 vs. UNCD: 48 ± 9.1, p > 0.05). Conversely, TiO2 exposure caused production of O2- in alveolar macrophages and consumption of catalase (p < 0.05). The studied parameters suggest that UNCD caused neither biochemical nor histological alterations, and therefore may prove useful as a surface coating for biomedical implants. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2408-2415, 2017.

Migration of titanium dioxide microparticles and nanoparticles through the body and deposition in the gingiva: an experimental study in rats.

The aim of this experimental work was to evaluate deposition of titanium dioxide (TiO2 ) microparticles and nanoparticles, which could originate from titanium bioimplants, in the gingiva. Wistar rats were injected intraperitoneally (i.p.) with a suspension of TiO2 particles of different sizes (150, 10, or 5 nm). The rats were killed 12 months post-injection, and the buccal and lingual gingivae were resected and evaluated using light and scanning electron microscopy. Energy-dispersive X-ray spectroscopy (EDS) was used to confirm the presence of titanium in deposits of microparticles and nanoparticles, and the concentration of titanium in tissues was measured using inductively coupled plasma-mass spectrometry (ICP-MS). Histological examination showed that all experimental groups exhibited agglomerates, in the gingiva, of titanium particles of micrometer size range, with no associated inflammatory response. Higher concentrations of titanium traces were shown, by ICP-MS, in both buccal and lingual tissues of all experimental groups compared with their matched controls. Titanium concentrations were significantly higher in the buccal gingiva than in the lingual gingiva, and after injection with 5-nm particles than with 10-nm particles in both localizations. Titanium microparticles and nanoparticles deposit in the gingiva, and mostly on the buccal side. Gingival deposition of titanium could be considered a tissue indicator of tribocorrosion processes of titanium bioimplants.

Effects of saliva on early post-tooth extraction tissue repair in rats.

The aim of the present study was to perform a biochemical, histological, and histomorphometrical evaluation of the mechanisms involved in tissue repair in rats subjected to submandibulectomy-induced hyposialia, 24, 48, and 72 hours of post-tooth extraction. We studied the correlation between the lack of submandibular saliva and the modulation of inflammatory mediators involved in tissue repair, such as prostaglandin E2 , nitric oxide (NO), and tumor necrosis factor alpha (TNF-α). Rats with hyposialia showed a delay in socket healing, slow replacement of the clot with granulation tissue, and fewer cells and collagen fibers, concomitant with a longer inflammatory process, as compared to controls. The lack of saliva induced by submandibulectomy modified the levels of prostaglandin E2 , NO, and TNF-α, and tissue response in the early stages of wound healing compared to controls, and could thus determine alterations in later osteogenic response. Our results allow concluding that hyposialia modulates the parameters of inflammation studied here, and that it is essential for optimal healing. Therefore, these findings provide evidence for the importance of submandibular saliva to final bone socket healing.

Use of Human Fascia Lata in Rat Calvarial Bone Defects.

Tooth loss leads to a decrease in alveolar bone volume, and consequently to the need for guided bone regeneration (GBR) techniques to restore bone anatomy, and the adequate choice of therapy. Fascia lata membrane (FLM) has been used in surgical procedures in neurology, orthopedics, otorhinolaryngology, cardiology, vascular surgery, gynecology, and dentistry for guided tissue regeneration. The aim of the present preliminary study was to evaluate bone tissue response in rat calvarial bone defects covered with human fascia lata membrane (FLM). Eight Wistar rats, 230g body weight, were subjected to bone surgery to create a 5x5mm long/ 1mm deep calvarial bone defect on either side of the median suture, using a piezoelectric scalpel and irrigation. The animals were treated according to the following protocol: Group I (GI): placement of a single layer of FLM (Biotar, Rosario, Prov. de Santa Fe, Argentina) to cover the defects; Group II (GII): double layer of FLM to cover the defects; Group III: no membrane; Group IV: control. All the animals were euthanized 60 days post-surgery; the heads were resected, radiographed, decalcified, and processed for embedding in paraffin and Hematoxylin-Eosin and Masson's trichrome staining. All bone defects covered with a single or double layer of FLM showed adequate osteogenesis, and none exhibited an inflammatory response. Groups III and IV Control showed scant osteogenesis and no alterations in soft tissues. The results obtained with this experimental model show biocompatibility of FML with the surrounding tissues at the studied time points. No alterations were observed in osteocytic lacunae or osteocytes in the bone after osteotomy using a piezoelectric scalpel. Further studies need to be conducted to assess bone tissue response to FLM in combination with bone substitutes.

La pérdida de piezas dentarias conlleva la disminución volumétrica del hueso alveolar y la necesidad de recurrir a técnicas de regeneración ósea guiada (ROG) para restablecer las condiciones anatómicas y aplicar las terapéuticas adecuadas. La membrana de fascia lata (MFL) ha sido utilizada en intervenciones quirúrgicas del área neurológica, ortopédica, otorrinolaringológica, cardiológica, vascular, ginecológica y odontológica para regeneración tisular guiada. El objetivo de este trabajo preliminar fue evaluar la respuesta tisular de defectos óseos en calota de rata recubiertos con MFL. Se utilizaron 8 ratas Wistar de 230 gr de peso, a las que se les realizó en la calota 2 defectos óseos de 5 x 5 mm de lado por 1 mm de profundidad, con bisturí piezoeléctrico e irrigación, a ambos lados de la línea media, según técnica estandarizada. Se realizó el siguiente protocolo: Grupo I (G I): colocación de una sola capa de MFL (Biotar, Rosario, Prov. de Santa Fe, Argentina) para cubrir el defecto; Grupo II (G II): colocación de MFL en doble capa para cubrir el defecto; Grupo III (G III): sin membrana; Grupo IV (G IV): control. Se les provocó la eutanasia a los 60 días. Las calotas fueron resecadas, radiografiadas y procesadas, previa descalcificación, para su inclusión en parafina y coloración con Hematoxilina-Eosina y Tricrómico de Masson. En todos los defectos óseos recubiertos con MFL simple o doble se evidenció una adecuada osteogénesis y ausencia de respuesta inflamatoria y macrófagos. El G III y el G Sham evidenciaron escasa osteogénesis y no mostraron alteraciones en el tejido blando. La MFL en el modelo experimental utilizado evidenció una respuesta compatible con el tejido circundante en los períodos estudiados. El tejido óseo remanente a la osteotomía con bisturí piezoeléctrico presentó las lagunas osteocíticas ocupadas con osteocitos y sin alteraciones. En estudios futuros se evaluará la respuesta tisular con MFL y utilizando un sustituto óseo.

In vitro age dependent response of macrophages to micro and nano titanium dioxide particles.

As a result of corrosion, microparticles (MP) and/or nanoparticles (NP) can be released from the metallic implants surface into the bioenvironment. The biological response to these particles depends not only on the physico-chemical properties of the particles but also on host factors, such as age. Macrophages have attracted wide concern in biomedicine. The aim of this investigation was to study the age related biological response of macrophages to TiO2 -MP and NP in vitro. Alveolar macrophages (AM) obtained from young and senescent rats were cultured and exposed to TiO2 -MP and NP. Cell metabolism, superoxide anion (O2 (-) ) and nitric oxide (NO) generation, and cytokine release (IL-6, TNFα, IL-10) were measured. Cell metabolism was not affected by particle exposure. O2 (-) and NO generation increased in a dose dependent manner. A marked increase on IL-6 release was found in the young-AM subpopulation exposed to TiO2 -MP. Conversely, both particle sizes induced a dose dependent release of TNFα in senescent-AM. Only the highest concentration of TiO2 -particles caused a significant increase in IL-10 release in AM-cultures. These observations lend strong support to the suggestion that cellular response of macrophages to TiO2 -particles is age dependent. The biological effect of the particles would seem to be more deleterious in the senescent age-group.

Use of human fascia lata in rat calvarial bone defects

Tooth loss leads to a decrease in alveolar bone volume, and consequently to the need for guided bone regeneration (GBR) techniques to restore bone anatomy, and the adequate choice of therapy. Fascia lata membrane (FLM) has been used in surgical procedures in neurology, orthopedics, otorhinolaryngology, cardiology, vascular surgery, gynecology, and dentistry for guided tissue regeneration. The aim of the present preliminary study was to evaluate bone tissue response in rat calvarial bone defects covered with human fascia lata membrane (FLM). Eight Wistar rats, 230g body weight, were subjected to bone surgery to create a 5x5mm long/ 1mm deep calvarial bone defect on either side of the median suture, using a piezoelectric scalpel and irrigation. The animals were treated according to the following protocol: Group I (GI): placement of a single layer of FLM (Biotar, Rosario, Prov. de Santa Fe, Argentina) to cover the defects; Group II (GII): double layer of FLM to cover the defects; Group III: no membrane; Group IV: control. All the animals were euthanized 60 days post-surgery; the heads were resected, radiographed, decalcified, and processed for embedding in paraffin and Hematoxylin-Eosin and Masson's trichrome staining. All bone defects covered with a single or double layer of FLM showed adequate osteogenesis, and none exhibited an inflammatory response. Groups III and IV Control showed scant osteogenesis and no alterations in soft tissues. The results obtained with this experimental model show biocompatibility of FML with the surrounding tissues at the studied time points. No alterations were observed in osteocytic lacunae or osteocytes in the bone after osteotomy using a piezoelectric scalpel. Further studies need to be conducted to assess bone tissue response to FLM in combination with bone substitutes.

La perdida de piezas dentarias conlleva la disminucion volumetrica del hueso alveolar y la necesidad de recurrir a tecnicas de regeneracion osea guiada (ROG) para restablecer las condiciones anatomicas y aplicar las terapeuticas adecuadas. La membrana de fascia lata (MFL) ha sido utilizada en intervenciones quirurgicas del area neurologica, ortopedica, otorrinolaringologica, cardiologica, vascular, ginecologica y odontologica para regeneracion tisular guiada. El objetivo de este trabajo preliminar fue evaluar la respuesta tisular de defectos oseos en calota de rata recubiertos con MFL. Se utilizaron 8 ratas Wistar de 230 gr de peso, a las que se les realizo en la calota 2 defectos oseos de 5 x 5 mm de lado por 1 mm de profundidad, con bisturi piezoelectrico e irrigacion, a ambos lados de la linea media, segun tecnica estandarizada. Se realizo el siguiente protocolo: Grupo I (G I): colocacion de una sola capa de MFL (Biotar, Rosario, Prov. de Santa Fe, Argentina) para cubrir el defecto; Grupo II (G II): colocacion de MFL en doble capa para cubrir el defecto; Grupo III (G III): sin membrana; Grupo IV (G IV): control. Se les provoco la eutanasia a los 60 dias. Las calotas fueron resecadas, radiografiadas y procesadas, previa descalcifica - cion, para su inclusion en parafina y coloracion con Hematoxilina-Eosina y Tricromico de Masson. En todos los defectos oseos recubiertos con MFL simple o doble se evidencio una adecuada osteogenesis y ausencia de respuesta inflamatoria y macrofagos. El G III y el G Sham evidenciaron escasa osteogenesis y no mostraron alteraciones en el tejido blando. La MFL en el modelo experimental utilizado evidencio una respuesta compatible con el tejido circundante en los periodos estudiados. El tejido oseo remanente a la osteotomia con bisturi piezoelectrico presento las lagunas osteociticas ocupadas con osteocitos y sin alteraciones. En estudios futuros se evaluara la respuesta tisular con MFL y utilizando un sustituto oseo.

Impact through time of different sized titanium dioxide particles on biochemical and histopathological parameters.

Due to corrosion, a titanium implant surface can be a potential source for the release of micro (MPs) and nano-sized particles (NPs) into the biological environment. This work sought to evaluate the biokinetics of different sized titanium dioxide particles (TiO2 ) and their potential to cause cell damage. Wistar rats were intraperitoneally injected with 150 nm, 10 nm, or 5nm TiO2 particles. The presence of TiO2 particles was evaluated in histologic sections of the liver, lung, and kidney and in blood cells at 3 and 12 months. Ultrastructural analysis of liver and lung tissue was performed by TEM, deposit concentration in tissues was determined spectroscopically, and oxidative metabolism was assessed by determining oxidative membrane damage, generation of superoxide anion (O2(-)), and enzymatic and non-enzymatic antioxidants. TiO2 particles were observed inside mononuclear blood cells and in organ parenchyma at 3 and 12 months. TiO2 deposits were consistently larger in liver than in lung tissue. Alveolar macrophage O2(-) generation and average particle size correlated negatively (p < 0.05). NPs were more reactive and biopersistent in lung tissue than MPs. Antioxidant activity, particularly in the case of 5 nm particles, failed to compensate for membrane damage in liver cells; the damage was consistent with histological evidence of necrosis.

Histologic and histomorphometric study of bone repair under acute Trypanosoma cruzi infection in rats.

Trypanosoma cruzi (T cruzi) is an intracellular protozoan pathogen that causes American trypanosomiasis (Chagas disease). The aim of this study was to evaluate the histopathological effects of acute infection by T. cruzi on bone repair, Wistar rats were used throughout. The animals were assigned to two groups: Control Group (CG n =20) and Experimental Group (EG n = 20). All the animals were anesthetized, at to the first lower right molar was extracted. The EG animals were inoculated subcutaneously at to with 0.1 mL of 10 trypomastigotes of the virulent strain Tulahuen of T. cruzi. The CG animals were administered an equivalent volume ofsaline solution subcutaneously. The animals in both groups were euthanized at 15 days post-infection and tooth extraction. The mandibles were resected, fixed informalin solution, radiographed, decalcified and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the mesial tooth socket of the first lower molar and stained with hematoxylin-eosin. Total alveolar volume (TV) and bone volume (TBV/TV) in the apical third of the tooth socket were evaluated histomorphometrically. The histological analysis revealed an alteration in post-extraction bone tissue repair in animals infected by T. cruzi. A reduction in osteogenic activity was observed concomitant with a rise in quiescent and eroded bone surfaces. Histomorphometric evaluation revealed a significant reduction (19%) in total alveolar volume (TV) and bone volume (TBV/TV) (24%) in the apical third of the tooth socket in animals infected with T. cruzi in comparison to non-infected animals (p<0.05). The results obtained using this experimental model showed decreased osteogenesis in bone tissue repair under acute Trypanosoma cruzi infection in rats.

Use of anorganic bovine bone matrix in an experimental model of bone healing.

The dimensions of the alveolar bone surrounding the tooth are not maintained post tooth-extraction probably as a consequence of the bone remodeling process and the biomechanical demands on bone. The use of biomaterials as bone substitutes in the post-tooth-extraction socket promotes bone repair, regardless of damage to bone structures during the surgical procedures. The aim of the present study was to evaluate the effectiveness of anorganic bovine bone matrix (ABBM) as a bone substitute, in an experimental model of post-tooth extraction bone healing in the rat. Radiographic follow-up was performed at 7, 14, and 30 days, and showed persistence of the biomaterial inside the experimental alveoli. At 14 and 30 days post-tooth extraction, particles surrounded by bone tissue were observed in the middle sector of the alveoli. The osteoconductive property of ABBM was demonstrated using the present experimental model of active osteogenesis, thus showing its usefulness as a bone substitute. Persistence of the particles at the studied experimental time points did not affect post-tooth extraction bone healing.

Oral mucosa tissue response to titanium cover screws.

BACKGROUND: Titanium is the most widely used metal in dental implantology. The release of particles from metal structures into the biologic milieu may be the result of electrochemical processes (corrosion) and/or mechanical disruption during insertion, abutment connection, or removal of failing implants. The aim of the present study is to evaluate tissue response of human oral mucosa adjacent to titanium cover screws. METHODS: One hundred fifty-three biopsies of the supra-implant oral mucosa adjacent to the cover screw of submerged dental implants were analyzed. Histologic studies were performed to analyze epithelial and connective tissue as well as the presence of metal particles, which were identified using microchemical analysis. Langerhans cells, macrophages, and T lymphocytes were studied using immunohistochemical techniques. The surface of the cover screws was evaluated by scanning electron microscopy (SEM). RESULTS: Forty-one percent of mucosa biopsies exhibited metal particles in different layers of the section thickness. Particle number and size varied greatly among specimens. Immunohistochemical study confirmed the presence of macrophages and T lymphocytes associated with the metal particles. Microchemical analysis revealed the presence of titanium in the particles. On SEM analysis, the surface of the screws exhibited depressions and irregularities. CONCLUSIONS: The biologic effects seen in the mucosa in contact with the cover screws might be associated with the presence of titanium or other elements, such as aluminum or vanadium. The potential long-term biologic effects of particles on soft tissues adjacent to metallic devices should be further investigated because these effects might affect the clinical outcome of the implant.

Histologic and histomorphometric study of bone repair under acute Trypanosoma cruzi infection in rats

Trypanosoma cruzi (T. cruzi) is an intracellular protozoan pathogen that causes American trypanosomiasis (Chagas disease). The aim of this study was to evaluate the histopathological effects of acute infection by T. cruzi on bone repair. Wistar rats were used throughout. The animals were assigned to two groups: Control Group (CG n =20) and Experimental Group (EG n =20). All the animals were anesthetized, at t0 the first lower right molar was extracted. The EG animals were inoculated subcutaneously at t0 with 0.1 mL of 105 trypomastigotes of the virulent strain Tulahuen of T. cruzi. The CG animals were administered an equivalent volume of saline solution subcutaneously. The animals in both groups were euthanized at 15 days post-infection and tooth extraction. The mandibles were resected, fixed in formalin solution, radiographed, decalcified and embedded in paraffin. Bucco-lingually oriented sections were obtained at the level of the mesial tooth socket of the first lower molar, and stained with hematoxylin-eosin. Total alveolar volume (TV) and bone volume (TBV/TV) in the apical third of the tooth socket were evaluated histomorphometrically. The histological analysis revealed an alteration in post-extraction bone tissue repair in animals infected by T. cruzi. A reduction in osteogenic activity was observed concomitant with a rise in quiescent and eroded bone surfaces. Histomorphometric evaluation revealed a significant reduction (19%) in total alveolar volume (TV) and bone volume (TBV/TV) (24%) in the apical third of the tooth socket in animals infected with T. cruzi in comparison to non-infected animals (p<0.05). The results obtained using this experimental model showed decreased osteogenesis in bone tissue repair under acute Trypanosoma cruzi infection in rats.

El Trypanosoma cruzi (T. cruzi) es un protozoario intracelular que causa Trypanosomoniasis Americana (Enfermedad de Chagas). El objetivo del presente trabajo fue el estudio histopatologico del efecto de la infeccion aguda por Trypanosoma cruzi sobre la reparacion del tejido oseo. Se utilizaron ratas Wistar macho que fueron asignadas a dos grupos: Grupo Control (GC n =20) y Grupo Experimental (GE n =20). Los animales de ambos grupos, bajo anestesia general intraperitoneal, fueron sometidos a t0, a exodoncia del primer molar inferior derecho, en el GE fueron inoculados,a t0 por via subcutanea en la region inguinal izquierda con 0.1 mL de 105 tripomastigotes de la cepa virulenta Tulahuen de Trypanosoma cruzi. A los animales del GC se les administro el volumen equivalente de solucion salina por via subcutanea. A los animales de ambos grupos se les practico la eutanasia a los 15 dias. Se resecaron las mandibulas, se fijaron en solucion de formol al 10%, se radiografiaron, se descalcificaron y se incluyeron en parafina. Se obtuvieron cortes orientados en sentido vestibulo-lingual a nivel del alveolo mesial del primer molar inferior derecho y se colorearon con hematoxilina-eosina para su posterior estudio histologico e histomorfometrico. Histologicamente se observo una menor actividad osteogenica a expensas de un incremento de las superficies quiescentes y de las superficies erosivas en el GE. En la evaluacion histomorfometrica se detecto disminucion estadiasticamente significativa del volumen oseo total (19%) y del volumen trabecular en el tercio apical del alveolo (24%) en el GE con respecto al GC (p<0.05). Los resultados obtenidos en este modelo experimental evidencian una disminucion de la osteogenesis en la reparacion osea en ratas con infeccion aguda por Trypanosoma cruzi.

Use of anorganic bovine bone matrix in an experimental model of bone healing

The dimensions of the alveolar bone surrounding the tooth are not maintained post tooth-extraction probably as a consequence of the bone remodeling process and the biomechanical demands on bone. The use of biomaterials as bone substitutes in the post-tooth-extraction socket promotes bone repair, regardless of damage to bone structures during the surgical procedures. The aim of the present study was to evaluate the effectiveness of anorganic bovine bone matrix (ABBM) as a bone substitute, in an experimental model of post-tooth extraction bone healing in the rat. Radiographic follow-up was performed at 7, 14, and 30 days, and showed persistence of the biomaterial inside the experimental alveoli. At 14 and 30 days post-tooth extraction, particles surrounded by bone tissue were observed in the middle sector of the alveoli. The osteoconductive property of ABBM was demonstrated using the present experimental model of active osteogenesis, thus showing its usefulness as a bone substitute. Persistence of the particles at the studied experimental time points did not affect post-tooth extraction bone healing.

Las dimensiones del hueso alveolar que rodea a la pieza dentaria, no se mantienen después de la exodoncia. Este hecho seria consecuencia del proceso de remodelado óseo y del requerimiento biomecánico. La utilización de biomateriales como sustitutos óseos en los alveolos, facilitan o promueven la reparación ósea, independientemente que se haya producido traumatismo de las estructuras óseas durante la maniobra quirúrgica. El objetivo del presente estudio fue evaluar la efectividad de una matriz ósea esponjosa anorgánica (MOEA) como sustituto óseo, en un modelo experimental de reparación ósea en el alveolo post-extracción en ratas. Se realizo el estudio radiográfico en los distintos tiempos experimentales: 7, 14 y 30 dias, evidenciando la persistencia del biomaterial. A los 14 y 30 días post-exodoncia se evidenciaron las partículas rodeadas de tejido óseo en el sector medio del alveolo. Es importante destacar que la utilización de (MOEA), como sustituto óseo en el alveolo post-exodoncia de rata, evidencio su capacidad osteoconductiva. La persistencia de las partículas del biomaterial en los tiempos estudiados no interfirió en la reparación ósea.

In vivo comparative biokinetics and biocompatibility of titanium and zirconium microparticles.

Titanium and zirconium are biomaterials that present a layer of titanium dioxide (TiO(2)) or zirconium dioxide (ZrO(2)). As a result of corrosion, microparticles can be released into the bioenvironment, and their effect on tissues is seemingly associated with differences in the physicochemical properties of these metals. The aim of this study was to perform a long-term evaluation of the distribution, destination, and potential risk of TiO(2) and ZrO(2) microparticles that might result from the corrosion process. Wistar rats were i.p. injected with an equal dose of either TiO(2) or ZrO(2) suspension. The following end-points were evaluated at 3, 6, and 18 months: (a) the presence of particles in blood cells and liver and lung tissue, (b) Ti and Zr deposit quantitation, (c) oxidant-antioxidant balance in tissues, and (d) O(2)(-) generation in alveolar macrophages. Ti and Zr particles were detected in blood mononuclear cells and in organ parenchyma. At equal doses and times postadministration, Ti content in organs was consistently higher than Zr content. Ti elicited a significant increase in O(2)(-) generation in the lung compared to Zr. The consumption of antioxidant enzymes was greater in the Ti than in the Zr group. The present study shows that the biokinetics of TiO(2) and ZrO(2) depends on particle size, shape, and/or crystal structure.

The issue of corrosion in dental implants: a review.

Pure titanium or titanium alloys, and to a lesser extent, zirconium, are metals that are often used in direct contact with host tissues. These metallic biomaterials are highly reactive, and on exposure to fluid media or air, quickly develop a layer of titanium dioxide (TiO2) or zirconium dioxide (ZrO2). This layer of dioxide forms a boundary at the interface between the biological medium and the metal structure, determining the degree of biocompatibility and the biological response of the implant. Corrosion is the deterioration a metal undergoes as a result of the surrounding medium (electrochemical attack), which causes the release of ions into the microenvironment. No metal or alloy is entirely inert in vivo. Corrosion phenomena at the interlace are particularly important in the evolution of both dental and orthopedic implants and one of the possible causes of implant failure after initial success. This paper comprises a review of literature and presents results of our laboratory experiments related to the study of corrosion, with special emphasis on dental implants. In situ degradation of a metallic implant is undesirable because it alters the structural integrity of the implant. The issue of corrosion is not limited to a local problem because the particles pmduced as a result could migrate to distant sites, whose evolution would require further studies.

Histomorphometric study of alveolar bone healing in rats fed a boron-deficient diet.

Bone healing after tooth extraction in rats is a suitable experimental model to study bone formation. Thus, we performed a study to determine the effects of boron (B) deficiency on bone healing by using this model. The first lower right molar of weanling Wistar rats was extracted under anesthesia. The animals were divided into two groups: +B (adequate; 3 mg B/kg diet), and -B (boron-deficient; 0.07 mg/kg diet). The animals in both groups were killed in groups of 10 at 7 and 14 days after surgery. The guidelines of the NIH for the care and use of laboratory animals were observed. The mandibles were resected, fixed, decalcified, and embedded in paraffin. Buccolingually oriented sections were obtained at the level of the mesial alveolus and used for histometric evaluations. Total alveolar volume (TAV) and trabecular bone volume per total volume (BV/TV) in the apical third of the alveolus were determined. Percentages of osteoblast surface (ObS), eroded surface (ES), and quiescent surface (QS) were determined. No statistical significant differences in food intake and body weight were observed. Histomorphometric evaluation found -B rats had 36% and 63% reductions in BV/TV at 7 and 14 days, respectively. When compared with +B rats, -B rats had significant reductions (57% and 87%) in ObS concomitantly with increases (120% and 126%) in QS at 7 and 14 days, respectively. The findings show that boron deficiency results in altered bone healing because of a marked reduction in osteogenesis.

A histomorphometric study of alveolar bone modelling and remodelling in mice fed a boron-deficient diet.

OBJECTIVE: Emerging evidence indicates that boron (B) plays a role in bone formation and maintenance. Thus, a study was performed to determine whether dietary B-deficiency affects periodontal alveolar bone modelling and remodelling. DESIGN: Weanling Swiss mice (n=30) were divided into three groups: control diet (GI, 3mg B/kg); B-deficient diet (GII, 0.07 mg B/kg); and pair-fed with GII (GIII). The animals were maintained on their respective diets for 9 weeks and then sacrificed. The guidelines of the NIH for the care and use of laboratory animals were observed. The mandibles were resected, fixed, decalcified in 10% EDTA and embedded in paraffin. Buccolingually oriented sections were obtained at the level of the mesial root of the first lower molar and stained with H-E. Histomorphometric studies were performed separately on the buccal and lingual sides of the periodontal alveolar bone. Percentages of osteoblast surfaces (ObSs), eroded surfaces (ESs), and quiescent surfaces (QSs) were determined. RESULTS: No statistically significant differences in food intake and body weight were observed between the groups. When compared with GI and GIII mice, GII mice (B-deficient) had 63% and 48% reductions in ObS and 58% and 73% increases in QS in buccal and lingual plates, respectively. ES were not affected by B nutriture. CONCLUSION: The results are evidence that dietary boron deprivation in mice alters periodontal alveolar bone modelling and remodelling by inhibiting bone formation.

Biological response of tissues with macrophagic activity to titanium dioxide.

The titanium dioxide layer is composed mainly of anatase and rutile. This layer is prone to break, releasing particles to the milieu. Therefore, corrosion may cause implant failure and body contamination. We have previously shown that commercial anatase-titanium dioxide (TiO(2)-anatase) is deposited in organs with macrophagic activity, transported in the blood by phagocytic-mononuclear cells, and induces an increase in the production of reactive oxygen species (ROS). In this study, we evaluated the effects of rutile-titanium dioxide (TiO(2)-rutile). Male Wistar rats were injected i.p. with a suspension of TiO(2)-rutile powder at a dose of 1.60 g/100 g b.w. Six months postinjection, the presence of Ti was assessed in serum, blood cells, liver, spleen, and lung. Titanium was found in phagocytic mononuclear cells, serum, and in the parenchyma of all the organs tested. TiO(2)-rutile generated a rise in the percentage of reactive cells, which was smaller than that observed when TiO(2)-anatase was employed in a previous study. Although TiO(2)-rutile provoked an augmentation of ROS, it failed to induce damage to membrane lipids, possibly due to an adaptive response. The present study reveals that TiO(2)-rutile is less bioreactive than TiO(2)-anatase.