Histological evaluation of subepithelial connective tissue grafts harvested by two different techniques: preliminary study in humans

Subepithelial connective tissue graft (SCTG) is an essential therapeutic tool in periodontal plastic surgery and implantology. The aim of this preliminary study was to observe and make a histological and histomorphometric comparison of the composition of subepithelial connective tissue grafts (SCTGs) harvested from the palatal mucosa by two different harvesting techniques: mucoperiosteal (lamina propria and complete submucosa including periosteum) and mucosal (lamina propria and a portion of the submucosa). The main hypothesis proposes that SCTG harvested with the mucosal technique contains a greater proportion of connective tissue proper (CTP) and a lower proportion of adipose tissue (AT) than the mucoperiosteal technique. Twenty healthy patients who required SCTG for different purposes were selected and assigned to one of the two following groups: group A (n=10; mucoperiosteal harvesting technique) and group B (n=10, mucosal harvesting technique). The histological sample was obtained by removing a 2 mm thick slice from the most distal portion of the graft. The proportions of adipose tissue (AT), connective tissue proper (CTP) and vascular tissue (VT) were evaluated. In group A, histomorphometric analysis showed that CTP accounted for 58.2% of the graft while AT accounted for 32.64%. In group B, the proportions of CTP and AT were 79.86% and 11.93%, respectively. The differences between groups were statistically significant for both tissues (p< .05). In contrast, no statistically significant difference was observed in the proportion of VT. Within the limitations of this study, the results show that the SCTGs harvested by the mucosal technique contain a greater proportion of CTP and a lower proportion of AT than those obtained by the mucoperiosteal technique, whereas the proportion of VT does not differ. Further longterm clinical and histological studies with more samples are needed to evaluate the clinical implications of SCTG composition (AU)

El injerto de tejido conectivo subepitelial (ITCSE) es una herramienta indispensable en la cirugía plástica periodontal y la implantología. El objetivo del presente estudio preliminar fue observar y comparar histológica e histomorfometricamente la composición de los injertos de tejido conectivo subepitelial (ITCSE) obtenidos de la mucosa palatina mediante dos técnicas diferentes: mucoperióstica (lamina propia y submucosa incluyendo el periostio) y mucosa (lámina propia y parte de la submucosa). La principal hipótesis postula que el ITCSE obtenido mediante la técnica mucosa contiene mayor proporción de tejido conectivo propiamente dicho (TCP) y menor proporción de tejido adiposo (TA) que el obtenido mediante la técnica mucoperióstica. El presente estudio incluyó veinte pacientes sanos que requerían ITCSE por diferentes motivos, los cuales fueron distribuidos de forma equitativa en dos grupos: grupo A (n=10; técnica de obtención mucoperióstica) y grupo B (n=10; técnica de obten ción mucosa). La muestra histológica se obtuvo removiendo una porción de 2 mm de ancho de la parte más distal del injerto. Se evaluó la proporción (%) de tejido adiposo (TA), tejido conectivo propiamente dicho (TCP) y tejido vascular (TV). En el grupo A, el análisis histomorfométrico mostró que el TCP constituía el 58.2% del tejido mientras que el tejido adiposo constituía el 32.64%. En el grupo B, la proporción de TCP y AT fue 79.86% y 11.93%, respectivamente. Las diferencias obser vadas entre los grupos fueron estadísticamente significativas para ambos tejidos (p< .05). En cambio, no se observaron dife rencias estadísticamente significativas en la proporción de TV. Dentro de las limitaciones del presente estudio, los resultados mostraron que los ITCSE obtenidos mediante la técnica mu cosa contienen mayor proporción de TCP y menor proporción de TA que los obtenidos con la técnica mucoperióstica, mientras que el TV permanece estable. Se requieren estudios longitudinales clínicos e histológicos a largo plazo con mayor cantidad de muestras para evaluar las implicancias clínicas de la composición del ITCSE (AU)

Alteraciones de la dentina con el envejecimiento / Dentin alterations with aging

Diferentes estudios han demostrado que después de la tercera década de vida hay una transición en la microestructura de la dentina. Dada la importancia de ésta como sustrato para la adhesión de materiales de restauración utilizados en operatoria y rehabilitación oral, ha sido objetivo de este trabajo realizar una búsqueda bibliográfica de las publicaciones existentes en inglés y español de los últimos 15 años, haciendo uso de buscadores científicos como Pubmed, Google Schoolar y LILACS que permitieran actualizar la información existente ayudando a entender los efectos biológicos del envejecimiento de la dentina, identificando los cambios de mayor relevancia a nivel histológico. De la búsqueda realizada se concluye que el envejecimiento de la dentina está asociado con aumento de dentina secundaria, formación de dentina esclerótica opaca, variaciones en la composición química de la matriz y disminución del número y actividad de los odontoblastos. Los conocimientos sobre el envejecimiento de la dentina deben tenerse en cuenta frente a estudios relacionados con materiales de restauración dental, ya que los cambios en la microestructura y capacidad funcional de la dentina con el envejecimiento requieren que éstos se adapten a dichas variaciones (AU)

Different studies have shown that aafter the third term of life there is a transition in the microstructure of dentin. Given the importance of dentin as a substrate for the adhesion of restorative materials used in operative and oral rehabilitation, the aim of the present work was to conduct a search of the scientific literature in English and Spanish, published in the last 15 years, using search engines such as Pubmed, Google Schoolar and LILACS, for an update on the biological effects of dentin aging, to identify the most relevant age-related histological changes in dentina. The data obtained from the literature review allow concluding that dentin aging is associated with an increase in secondary dentina, opaque sclerotic dentin formation, variations in the chemical composition of the matrix and a decrease in odontoblast number and activity. Updated information on dentin aging should be taken into account in studies on dental restoration materials, since the latter must adapt to aging-related changes in the microstructure and functional capacity of dentin (AU)

A Review of Metal Exposure and Its Effects on Bone Health.

The presence of metals in the environment is a matter of concern, since human activities are the major cause of pollution and metals can enter the food chain and bioaccumulate in hard and soft tissues/organs, which results in a long half-life of the metal in the body. Metal intoxication has a negative impact on human health and can alter different systems depending on metal type and concentration and duration of metal exposure. The present review focuses on the most common metals found in contaminated areas (cadmium, zinc, copper, nickel, mercury, chromium, lead, aluminum, titanium, and iron, as well as metalloid arsenic) and their effects on bone tissue. Both the lack and excess of these metals in the body can alter bone dynamics. Long term exposure and short exposure to high concentrations induce an imbalance in the bone remodeling process, altering both formation and resorption and leading to the development of different bone pathologies.

Study of epithelial rests of Malassez in an experimenal periodontitis model

The aim of this study was to evaluate the morphological alterations of epithelial cell rests of Malassez (ERMs) and their rela tionship with root resorption, in an experimental periodon titis (EP) model at 4 and 11 days. EP was induced in 14 male Wistar rats by placing a cotton thread ligature around the neck of the first lower right molar, for 4 (n=7) and 11 (n=7) days. The contralateral molar (left) was used as control. Following euthanasia, jaws were extracted and processed histologically to provide mesiodistal sections which were subject to H&E stain and histochemical detection technique with tartrateresistant acid phosphatase (TRAP). The following histomorphometric parameters were evaluated on micrographs: bone area (BAr./TAr)(%), number of ERMs/mm2, number of cells/ ERM, ERMs area (µm2), and percentage of root resorption surfaces (%RR). The results were analyzed statistically by ANOVA and Bonferroni post hoc (p£ 0.05). Significant bone loss was observed in molars with EP compared to their controls. In the EP 4Day group, no change was observed in the parameters with relation to the ERMs; however, in the EP 11Day group, there was significant root resorption (%RR) (C: 3.21±3.07, EP4D: 3.91±3.17, EP11D: 23.67± 11.40; p£ 0,05) and increase in ERMs area (µm2) (C: 455.87±145.42, EP4D: 577.6±156.1, EP11D: 1046.3± 582.9; p£ 0,05). No TRAP+ ERM was found in either group. ERM hypertrophy may be related to ERM partici pation in mechanisms tending to establish periodontal homeostasis inhibiting resorption and contributing to periodon tal regeneration (AU)

El objetivo de este trabajo ha sido evaluar las alteraciones morfológicas de epithelial cell rests of Malassez (ERMs) y su relación con la reabsorción radicular, en un modelo de experimental periodontitis (EP) a 4 y 11 días. La EP fue inducida en 14 ratas Wistar macho mediante la colocación de una ligadura de hilo de algodón alrededor del cuello del primer molar inferior derecho, a 4 (n=7) y 11 (n=7) días. El molar contralateral (izquierdo) fue usado como control. Tras la eutanasia, se extrajeron los maxilares y se procesaron histológicamente para la obtención de cortes en sentido mesiodistal que se colorearon con H&E y técnica histoquímica de detección de tartrateresistant acid phosphatase (TRAP). Se tomaron microfotografías y se evaluaron los siguientes parámetros histomorfométricos: Bone area (BAr./TAr)(%), Nº de ERMs/mm2, Nº de células/ERM, área de ERMs (µm2), y porcentaje de superficies de reabsorción radicular (%RR). Los resultados se analizaron estadísticamente mediante Anova y Bonferroni post hoc (p£ 0.05). En los molares con PE se observó una pérdida ósea significativa en relación a sus controles. En el grupo EP 4 días no se observaron cambios en los parámetros en relación a los ERMs, sin embargo, en el grupo PE de 11 días se registró reabsorción radicular (%RR) significativa (C: 3.21±3.07, EP4D: 3.91±3.17, EP11D: 23.67±11.40; p£ 0,05) junto con un aumento del área de ERMs (µm2) (C: 455.87±145.42, EP4D: 577.6±156.1, EP11D: 1046.3±582.9; p£ 0,05). No se observaron ERMs TRAP + en ninguno de los dos grupos. La hipertrofia de los ERMs, podría estar relacionada a la participación de los mismos en mecanismos tendientes a la homeostasis periodontal, inhibiendo dicha reabsorción y contribuyendo a la regeneración periodontal (AU)

Effect of cadmium on bone tissue in growing animals.

Accumulation of cadmium (Cd), an extremely toxic metal, can cause renal failure, decreased vitamin D synthesis, and consequently osteoporosis. The aim of this work was to evaluate the effect of Cd on two types of bone in growing Wistar rats. Sixteen 21-day-old male Wistar rats were assigned to one of two groups. The Cd group subcutaneously received 0.5mg/kg of CdCl2 5 times weekly for 3 months. The control group similarly received bidistilled water. Following euthanasia, the mandibles and tibiae were resected, fixed, decalcified and processed histologically to obtain sections for H&E and tartrate-resistant acid phosphatase (TRAP) staining. Photomicrographs were used to determine bone volume (BV/TV%), total growth cartilage width (GPC.Wi) hypertrophic cartilage width (HpZ.Wi), percentage of yellow bone marrow (%YBM), megakaryocyte number (N.Mks/mm(2)), and TRAP+osteoclast number (N.TRAP+Ocl/mm(2)). Results were statistically analyzed using Student's t test. Cd exposed animals showed a significant decrease in subchondral bone volume and a significant increase in TRAP+ osteoclast number and percentage of yellow bone marrow in the tibia, and an increase in megakaryocyte number in mandibular interradicular bone. No significant differences were observed in the remaining parameters. The results obtained with this experimental design show that Cd would seemingly have a different effect on subchondral and interradicular bone. The decrease in bone volume and increase in tibial yellow bone marrow suggest that cadmium inhibits differentiation of mesenchymal cells to osteoblasts, favoring differentiation into adipocytes. The different effects of Cd on interradicular bone might be due to the protective effect of the mastication forces.

Reseña actualizada de ingeniería tisular en disciplinas odontológicas / An updated review of tissue engineering in dental disciplines

La ingeniería tisular (IT) ha sido considerada un campo interdisciplinario, aplicando los principios de ciencias de ingeniería y biología para el desarrollo de sustitutos biológicos que restauran, mantienen o mejoran la función tisular. Se basa en el entendimiento de losprincipios del crecimiento tisular, y su aplicación, para producir reemplazo de tejidos para uso clínico. Se consideran determinantes para el éxito de la IT las Stem Cells (células madre), morfógenos y las “scaffolds” (constructos). Poner en práctica dicha disciplina requiere elempleo de estrategias terapéuticas biológicas que apuntan a reemplazar, reparar, mantener y/o mejorar la función tisular. El objetivo de este trabajo, ha sido realizar una actualización sobre nuevos conocimientos emergentes de las últimas publicaciones científicas realizadas en el ámbito de esta nueva disciplina. Para ello se realizó una exhaustiva búsqueda de información en la base de datos de Pubmed. Actualmente, la IT concentra sus esfuerzos en lograr la regeneración de tejidos dentarios y para dentarios, así como en lograr la obtención de una pieza dental completa. Su avance clínico ha sido notable. Se han reportado artículos publicados que ya evidencian su aplicación en periodoncia, cirugía, implantología, rehabilitación oral y endodoncia. Si bien, estrategias de la IT ya se utilizan clínicamente en odontología, su rápido desarrollo se convierte entonces en un gran desafío e incógnita tanto para quienes ejercen la profesión en la actualidad, como para aquellos que se encuentran en plena formación académica. Tomar conocimiento de logros y avances resulta entonces fundamental, ya que podría convertirse en un futuro próximo, en una herramienta de uso habitual.

Tissue engineering (TE) is considered an interdisciplinary field, and applies principles of engineering and biology to develop biologicalsubstitutes that restore, maintain, or improve tissue function. It is based on the application of the principles of tissue growth to producetissue replacement for clinical use. Stem cells, morphogens, and scaffolds are determinant to the success of TE. Implementation of TErequires the use of biological therapeutic strategies aiming to replace, repair, maintain, and/or improve tissue function. The objective ofthe present work was to perform an update of new knowledge presented in recent scientific publications in this field. For this purpose, weconducted an extensive search for information on Pubmed. At present, TE focuses on achieving regeneration of dental and para-dentaltissues, as well as on obtaining a whole tooth. There have been outstanding clinical advances in this field. There are reports showingsuccessful application of TE in periodontics, surgery, implantology, oral rehabilitation and endodontics. Although TE strategies arealready used in dentistry, their rapid development poses a great challenge both to current practitioners and to those who are in the midst oftheir academic training. Gaining an awareness of the achievements and advances in TE is therefore essential, since it could become widelyapplied in the near future.

Actualización en ortodoncia y bifosfonatos: consideraciones clínicas y experimentales / An update on biphosphonates: clinical and experimental considerations

Los bisfosfonatos son fármacos utilizados para el tratamiento de enfermedades que afectan al metabolismo óseo, principalmente para el tratamiento de la osteoporosis, siendo ésta la principal causa de prescripción médica de los mismos. Actualmente, no se encuentran esclarecidas las posibles complicaciones o riesgos implícitos del tratamiento ortodóntico aplicado a pacientes que reciben o han recibidobisfosfonatos. Dada la demanda actual, con un elevado número de pacientes que se encuentran en la búsqueda de un tratamiento ortodóntico muchos de los cuales son y/o han sido tratados con bisfosfonatos para la osteoporosis, es de relevancia conocer el efecto de laaplicación de fuerzas ortodónticas en un tejido óseo que ha sido tratado con dichas drogas. Por lo antedicho, el objetivo de este trabajo, ha sido realizar una actualización sobre los nuevos conocimientos emergentes de las últimas publicaciones científicas provenientes de trabajos clínicos como así también experimentales que asocien la ortodoncia y los bisfosfonatos. Para ello se realizó una exhaustiva búsqueda de información en la base de datos de Pubmed. La búsqueda obtenida reveló que en los pacientes que reciben y/o han recibido bisfosfonatos y son tratados ortodónticamente se observa una disminución del movimiento dentario, escasa obtención de paralelismo radicular y, en los casos con exodoncias previas aparición de áreas de esclerosis ósea. No fueron descriptos casos en los que se viera asociada la aparición de osteonecrosis de los maxilares. Por su parte, los estudios experimentales, obtuvieron resultados orientados en el mismo sentido, avalando los resultados clínicos...

Influence of bisphosphonate treatment on medullary macrophages and osteoclasts: an experimental study.

Nitrogen-containing bisphosphonates are widely used for treating diverse bone pathologies. They are anticatabolic drugs that act on osteoclasts inhibiting bone resorption. It remains unknown whether the mechanism of action is by decreasing osteoclast number, impairing osteoclast function, or whether they continue to effectively inhibit bone resorption despite the increase in osteoclast number. There is increasing evidence that bisphosphonates also act on bone marrow cells like macrophages and monocytes. The present work sought to evaluate the dynamics of preosteoclast fusion and possible changes in medullary macrophage number in bisphosphonate-treated animals. Healthy female Wistar rats received olpadronate, alendronate, or vehicle during 5 weeks, and 5-bromo-2-deoxyuridine (BrdU) on day 7, 28, or 34 of the experiment. Histomorphometric studies were performed to study femurs and evaluate: number of nuclei per osteoclast (N.Nu/Oc); number of BrdU-positive nuclei (N.Nu BrdU+/Oc); percentage of BrdU-positive nuclei per osteoclast (%Nu.BrdU+/Oc); medullary macrophage number (mac/mm(2)) and correlation between N.Nu/Oc and mac/mm(2). Results showed bisphosphonate-treated animals exhibited increased N.Nu/Oc, caused by an increase in preosteoclast fusion rate and evidenced by higher N.Nu BrdU+/Oc, and significantly decreased mac/mm(2). Considering the common origin of osteoclasts and macrophages, the increased demand for precursors of the osteoclast lineage may occur at the expense of macrophage lineage precursors.

Ethanol consumption enhances periodontal inflammatory markers in rats.

OBJECTIVE: The aim of this study was to assess the short term effect of ethanol administration on periodontal disease in rats. DESIGN: Rats received either ethanol 2g/kg or water by gastric gavage twice a day. On the fifth day ligatures were tied around the molars of half of the rats to induce periodontitis. After 7days gingival tissue was removed and assayed for inflammatory markers. Finally, hemi-mandibles were extracted to evaluate bone loss by histomorphometrical techniques. RESULTS: The experimental periodontitis increased significantly the mRNA expression (p<0.001) and activity (p<0.001) of inducible nitric oxide synthase (iNOS) in the gingival tissue, whilst short time ethanol administration increased iNOS activity (p<0.05) and produced an additive effect on iNOS mRNA expression augmented by periodontitis (p<0.01). The short time ethanol administration also potentiated the periodontitis stimulatory effect on the mRNA expression of interleukin (IL)-1ß (p<0.01 and p<0.001, in semi-quantitative and real time PCR, respectively) and on the height of periodontal ligament (p<0.05). However, the ligature-induced periodontitis, but not ethanol administration, increased the prostaglandin E(2) content (p<0.05) and, diminished the alveolar bone volume (p<0.05), as compared to sham rats. CONCLUSION: The present results suggest that ethanol consumption could represent a risk indicator for periodontal disease since augments the expression of inflammatory markers, in healthy rats, and increases them, at short term, during the illness. However, scale longitudinal investigation and more case-control studies are needed to confirm this statement.

Experimental model of distraction osteogenesis in edentulous rats.

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.

Experimental model of distraction osteogenesis in edentulous rats

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.

Effect of arsenic in endochondral ossification of experimental animals.

Arsenic (As) toxicity is a global health problem affecting millions of people, the most toxic forms being Arsenites [As(III)] and Arsenates [As(V)]. Arsenic intoxication can occur through different exposure routes. The aim of the present work was to determine the effect of As on endochondral ossification and bone remodeling in experimental animals, by means of biochemical, histologic, and histomorphometric determinations. Sixteen male Wistar rats, 100g body weight (b.w.), were divided into two groups: experimental group (n=8), treated with 10mg/l of NaAsO(2) in their drinking water, receiving 0.21mg/kgb.w./day during 45 days; and control group (n=8) remained untreated. On day 45, blood samples were obtained by cardiac puncture to perform hematologic blood counts and biochemical determination. The animals were killed, the tibiae, femurs, kidneys and livers were resected, fixed in formalin and processed histologically. Tibia and femur sections were obtained and stained with H&E. The following histomorphometric parameters were determined on tibia and femur sections: bone volume (BV/TV), thickness of growth plate cartilage (GPC.Th) and thickness of hypertrophic zone (HpZ.Th). Biochemical determinations showed that experimental animals exhibited neutrophilia and a decrease in lymphocytes and monocytes. As levels were below 1 microg/dl in both groups. The femur sections of the experimental group showed (1) a statistically significant increase in total growth cartilage plate thickness (p<0.05) at the expense of the hypertrophic zone (p<0.05); (2) subchondral trabecular bone sealed to the growth plate with a non-significant increase in primary spongiosa bone volume. These results suggest that As alters endochondral ossification.