ABSTRACT
OBJECTIVES: Hexavalent chromium (CrVI)-exposure of suckling rats has been shown to delay tooth eruption. However, the effects of CrVI-exposure on bone formation at the base of the alveolus, which provides a motive force for tooth eruption in the early stages of the process, remain unknown. The present work sought to evaluate the effect of CrVI-exposure on bone formation at the base of the alveolus during the intraosseous stage of tooth eruption in suckling rats, using histomorphometric and immunohistochemical studies. METHODS: Experimental animals received 12.5 mg/kg-bw/day of potassium dichromate dissolved in saline solution by gavage starting on day 4 of the experiment; controls similarly received an equivalent volume of saline. All the animals were euthanized at the age of 9 days. The base of the developing alveolus at the level of the mesial root of the first lower molar was analyzed histomorphometrically and immunohistochemically. Data were statistically analyzed using student's t-test, with statistical significance set at p < 0.05. RESULTS: CrVI-exposed animals showed lower bone volume and height at the base of the alveolus, a significant preponderance of bone rest on the surface adjacent to the dental follicle, and a significantly lower percentage of positive Runt-related transcription factor-2 (RUNX2+) osteoblasts and a significantly higher number of mesenchymal-like RUNX2+ cells at the latter site. CONCLUSION: CrVI-exposure during lactation affects bone formation at the base of the developing alveolus, delaying tooth eruption. These findings underscore the importance of controlling drinking water levels of toxic substances since their effects can alter the growth and development of individuals exposed during early childhood.
Subject(s)
Osteogenesis , Tooth Eruption , Child, Preschool , Female , Rats , Humans , Animals , Core Binding Factor Alpha 1 Subunit , Chromium/toxicityABSTRACT
BACKGROUND: Heavy metals including Cr VI are present in inadequately treated effluents that contaminate drinking water. Hence, Cr VI exposure can affect children through intake of breast milk from an exposed mother or bottle-feeding formula prepared with contaminated water. To date, there are no reports on the effects of Cr VI exposure on tooth formation processes concomitant to tooth eruption. AIM: To study the effect of Cr VI exposure on tooth tissue formation in suckling Wistar rats by assessing dental tissues at different stages of tooth eruption. DESIGN: Experimental animals received 12.5 mg/kg body weight/day of a potassium dichromate solution by gavage; control animals were similarly administered an equivalent volume of saline solution. Each group was divided into three subsets according to age at euthanasia: 9, 15, and 23 days. Dental formation was analysed histologically and histomorphometrically. STATISTICAL ANALYSIS: Student's t test; P < .05. RESULTS: Cr VI-exposed animals showed a delay in mineralized crown and root tissue formation. These findings are directly associated with the observed delay in tooth eruption. CONCLUSION: Our findings show the importance of monitoring drinking water levels of toxic substances, since exposure during early childhood can alter tooth formation, growth, and development.
Subject(s)
Odontogenesis , Tooth Eruption , Animals , Animals, Suckling , Child , Chromium , Female , Humans , Rats , Rats, WistarABSTRACT
Increasing duration of type 1 diabetes mellitus alters bone metabolism. Clinical studies and experimental studies in long bones of rats with experimentally induced diabetes have reported a decrease in bone density. Few studies have explored this diabetes related alteration in the maxillae. Given that this finding could indicate the possible development of osteopenia in the maxilla in the long term, the present study sought to analyze alterations in alveolar bone in aged rats, 12, 18, and 24weeks after inducing diabetes, and compare alveolar bone response to that of tibial subchondral bone at the same experimental times. Thirty-six male Wistar rats, 130g body weight, were divided into 2 groups: an experimental group (E) receiving a single i.p. 60mg/kg dose of streptozotocin, and a control group (C). Both the control and experimental groups were divided into 3 sub-sets, according to the time of euthanasia: 12, 18 and 24weeks. The alveolar bone and tibiae were examined histologically and histomorphometrically. The results were analyzed using Student's t-test; a value of p<0.05 was considered statistically significant. RESULTS: Subchondral bone volume and bone activity/remodeling, mainly bone rest, were significantly lower in diabetic animals compared to controls, at both 12 and 18weeks. No differences in alveolar bone parameters were observed between diabetic and control animals at either of the experimental times. Animals surviving at 24weeks showed few trabeculae at rest and severe destruction of dental and periodontal tissues. The results of the present study show that diabetic osteopenia is evident in the tibia at 12 and at 18weeks, whereas its effects on the maxilla can be seen at 24weeks, with substantial destruction of alveolar bone and of the remaining periodontal and dental tissues. All the above observations highlight the need for preventive oral care in diabetic patients, before irreversible damage to dental and periodontal tissues occurs.
Subject(s)
Aging/metabolism , Alveolar Bone Loss/pathology , Bone Diseases, Metabolic/pathology , Diabetes Mellitus, Experimental/complications , Diabetes Mellitus, Type 1/complications , Tibia/pathology , Animals , Blood Glucose , Body Weight , Bone Density , Bone Diseases, Metabolic/etiology , Male , Rats , Rats, Wistar , Streptozocin/toxicityABSTRACT
UNLABELLED: Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin. STUDY PROTOCOL: latency: 6 days, distraction: » turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.
Subject(s)
Bone Regeneration/physiology , Mandible/surgery , Osteogenesis, Distraction/methods , Animals , Male , Mandible/anatomy & histology , Models, Animal , Mouth, Edentulous/diagnostic imaging , Osteogenesis, Distraction/instrumentation , Osteotomy , Radiography , Rats , Rats, Wistar , Wound HealingABSTRACT
Distraction osteogenesis (DO) is a surgical technique producing bone lengthening by distraction of the fracture callus. Although a large number of experimental studies on the events associated with DO of craniofacial skeleton have been reported, the few employing rat mandibular bone DO used complicated designs and produced a small volume of newly formed bone. Thus, this study aims to present an original experimental model of mandibular DO in edentulous rats that produces a sufficient quantity and quality of intramembranous bone. Eight male Wistar rats, weighing 75 g, underwent extraction of lower molars. With rats weighing 350 g, right mandibular osteotomy was performed and the distraction device was placed. The distraction device was custom made using micro-implants, expansion screws, and acrylic resin. Study protocol: latency: 6 days, distraction: » turn (0.175 mm) once a day during 6 d, consolidation: 28 d after distraction phase, sacrifice. DO-treated and contralateral hemimandibles were dissected and compared macroscopically and using radiographic studies. Histological sections were obtained and stained with H&E. A distraction gap filled with newly formed and mature bone tissue was obtained. This model of mandibular DO proved useful to obtain adequate quantity and quality of bone to study bone regeneration.
Subject(s)
Animals , Male , Rats , Bone Regeneration/physiology , Mandible/surgery , Osteogenesis, Distraction/methods , Models, Animal , Mandible/anatomy & histology , Mouth, Edentulous , Osteotomy , Osteogenesis, Distraction/instrumentation , Rats, Wistar , Wound HealingABSTRACT
INTRODUCTION: Patients with type 1 diabetes have shown decreased bone mineral density (BMD) values. The need for orthodontic treatment in diabetic patients is usually associated with occlusal problems and the occurrence of abnormalities in the development of the jaws. The aim of this study was to analyze bone response of insulin-treated and untreated diabetic rats after applying orthodontic forces. METHODS: Wistar rats were divided into 3 groups: experimental orthodontics, experimental diabetes and orthodontics, and experimental diabetes treated with insulin and experimental orthodontics. Orthodontic forces were applied the first day of the seventh week. Forty-eight hours after placement, all the animals were killed, and the maxillae were excised and processed using routine histologic techniques. RESULTS: Bone activity in the periodontal cortex of the dental alveolus showed a significant decrease in bone formation and erosive areas in diabetic animals as compared with controls. A recovery of these parameters could be observed in the group with experimental diabetes treated with insulin and experimental orthodontics. Bone volume in the interradicular bone showed no significant differences among groups. CONCLUSIONS: People with diabetes should not receive orthodontic treatment until their metabolic status normalizes. Bone response to orthodontic forces in insulin-treated diabetic subjects does not differ significantly from that observed in healthy subjects.
Subject(s)
Bone Remodeling , Dental Stress Analysis , Diabetes Mellitus, Experimental/physiopathology , Tooth Movement Techniques , Animals , Bone Density , Contraindications , Diabetes Mellitus, Experimental/drug therapy , Diabetes Mellitus, Experimental/metabolism , Hypoglycemic Agents/therapeutic use , Insulin/therapeutic use , Male , Osteoblasts , Osteoclasts , Rats , Rats, Wistar , StreptozocinABSTRACT
El objetivo de este trabajo fue analizar diferentes sustratos empleados en la determinación de la resistencia adhesiva composite-resina y comprende 3 partes. En la primera se comparan los resultados obtenidos al utilizar dentina humana y bovina. En la segunda se estudió la resistencia de la unión sobre diferentes ángulos de corte de dentina bovina. En la tercera, se analizó el efecto de diferentes medios de almacenaje sobre la adhesión composite-dentina. Se utilizaron dos métodos de estudio para determinar la capacidad de la dentina bovina para reproducir de la mejor manera posible las condiciones "in vivo": a) ensayos de adhesión. Se determinó la resistencia traccional de probetas de composite montadas sobre superficies planas de dentina tratadas con los agentes adhesivos y conservadas en saliva artificial a 37 grados C. b) Observación de las superficies de corte por microscopía electrónica de barrido. Los resultados obtenidos mostraron que los valores más confiables se obtuvieron al utilizar dentina bovina conservada en agua destilada a 4 grados C, seccionada con un ángulo de 125 grados con respecto a la cara vestibular incluyendo los últimos 7 mm. desde el borde incisal (AU)
Subject(s)
Humans , Animals , Cattle , Composite Resins/chemistry , Dental Bonding/methods , Dentin/ultrastructure , Tensile Strength , Microscopy, Electron, Scanning/methods , AdhesivesABSTRACT
El objetivo de este trabajo fue analizar diferentes sustratos empleados en la determinación de la resistencia adhesiva composite-resina y comprende 3 partes. En la primera se comparan los resultados obtenidos al utilizar dentina humana y bovina. En la segunda se estudió la resistencia de la unión sobre diferentes ángulos de corte de dentina bovina. En la tercera, se analizó el efecto de diferentes medios de almacenaje sobre la adhesión composite-dentina. Se utilizaron dos métodos de estudio para determinar la capacidad de la dentina bovina para reproducir de la mejor manera posible las condiciones "in vivo": a) ensayos de adhesión. Se determinó la resistencia traccional de probetas de composite montadas sobre superficies planas de dentina tratadas con los agentes adhesivos y conservadas en saliva artificial a 37 grados C. b) Observación de las superficies de corte por microscopía electrónica de barrido. Los resultados obtenidos mostraron que los valores más confiables se obtuvieron al utilizar dentina bovina conservada en agua destilada a 4 grados C, seccionada con un ángulo de 125 grados con respecto a la cara vestibular incluyendo los últimos 7 mm. desde el borde incisal
Subject(s)
Humans , Animals , Cattle , Composite Resins/chemistry , Dental Bonding , Dentin/ultrastructure , Adhesives , Microscopy, Electron, Scanning/methods , Tensile StrengthABSTRACT
Se presenta un estudio histomorfométrico del proceso de reabsorción ósea en los estadíos iniciales de la periodontitis. El estudio se realizó en un modelo experimental que logra la formación de la placa bacteriana sobre una ligadura de hilo de algodón colocada en el cuello del molar de ratas Wistar. Los animales así tratados fueron sacrificados después de 24, 48, 72 y 96 horas de comenzado el experimento. Un número equivalente de animales fue empleado como control. Luego del proceso histológico de los maxilares inferiores, fueron obtenidos cortes mesiodistales a nivel de los molares. El estudio histológico mostró la progresión del cuadro inflamatorio y de las áreas erosivas. Los estudios histomorfométricos mostraron que las áreas de reabsorción ósea aumentaban concomitantemente con el número de osteoclastos hasta las 72 horas. A partir de ese punto ambos parámetros disminuyen, siendo mayor el descenso en el número de osteoclastos. Los resultados se discuten con los obtenidos en otros modelos experimentales en los que la reabsorción ósea se obtiene por la acción de fuerzas compresivas. En este último caso el incremento de las áreas de reabsorción precede al incremento en el número de osteoclastos. Se postula la existencia de, al menos, dos mecanismos de reabsorción ósea, uno relacionado a un proceso inflamatorio y el otro vinculado a la acción de fuerzas mecánicas (AU)
Subject(s)
Animals , Rats , Periodontitis/physiopathology , Bone Resorption , Dental Plaque , Histological Techniques , Disease Models, Animal , Rats, Wistar , Molar/ultrastructure , Osteoclasts/physiologyABSTRACT
Se presenta un estudio histomorfométrico del proceso de reabsorción ósea en los estadíos iniciales de la periodontitis. El estudio se realizó en un modelo experimental que logra la formación de la placa bacteriana sobre una ligadura de hilo de algodón colocada en el cuello del molar de ratas Wistar. Los animales así tratados fueron sacrificados después de 24, 48, 72 y 96 horas de comenzado el experimento. Un número equivalente de animales fue empleado como control. Luego del proceso histológico de los maxilares inferiores, fueron obtenidos cortes mesiodistales a nivel de los molares. El estudio histológico mostró la progresión del cuadro inflamatorio y de las áreas erosivas. Los estudios histomorfométricos mostraron que las áreas de reabsorción ósea aumentaban concomitantemente con el número de osteoclastos hasta las 72 horas. A partir de ese punto ambos parámetros disminuyen, siendo mayor el descenso en el número de osteoclastos. Los resultados se discuten con los obtenidos en otros modelos experimentales en los que la reabsorción ósea se obtiene por la acción de fuerzas compresivas. En este último caso el incremento de las áreas de reabsorción precede al incremento en el número de osteoclastos. Se postula la existencia de, al menos, dos mecanismos de reabsorción ósea, uno relacionado a un proceso inflamatorio y el otro vinculado a la acción de fuerzas mecánicas