Facial development disorders due to inhibition to endochondral ossification of mandibular condyle process caused by malnutrition.

OBJECTIVE: To analyze the effect of protein restriction on histomorphometric parameters of bone remodeling in mandibular condyle process and its possible influence in facial development in growing rats. MATERIALS AND METHODS: Wistar rats weaned at the age of 21 days were assigned to one of the following groups: control (fed a regular hard diet ad libitum) and protein restricted (PR) (fed a hard diet lacking in protein ad libitum). The animals were euthanized on day 35 after the onset of the experiment. Mandibles were resected, fixed in 10% formalin, hemisected at the symphysis, and then radiographed in order to perform cephalometric studies of the condylar process length and the height of the lower alveolar process. Mandibles were then processed for light microscopy, and histomorphometric determinations were performed on histologic sections of the condylar process subchondral bone. RESULTS: The PR group showed a significantly lower body weight than control group at the end of the experiment. The length of the condylar process was lower in the PR group; however, the diet used in this study did not affect the height of the lower alveolar process. The histomorphometric analysis showed that the PR group exhibited a statistically significant decrease in bone formation and bone volume in condylar process subchondral bone. CONCLUSION: Protein restriction inhibits bone formation and longitudinal growth in the mandibular condylar process. This result suggest that protein restriction can alter normal facial development.

Orthodontic implications of protein undernutrition in mandibular growth. A cephalometric study in growing rats.

The present experimental work analyzes the development of different mandibular units and its likely impact on the direction of mandibular displacement during facial development, and the relation between the mesiodistal dimension of the first, second, and third molars and the length of the mandibular corpus in a model of protein undernutrition with muscular atrophy in growing rats. Sixteen Wistar rats weaned at the age of 21 days were assigned to one of the following groups: control (fed a regular hard diet ad libitum) and experimental (fed a diet lacking in protein, corn flour, ad libitum). All the animals were euthanized five weeks after the onset of the experiment. Following resection of the mandibles, the mandibles were hemisected at the symphysis and fixed in 10% formalin. Remaining soft tissue was removed. Metallic landmarks were placed in the mental and mandibular foramens of one hemimandible of each rat. The hemimandibles were radiographed. The cephalometric study was performed on paper tracings of the projected image of the radiographs. Both groups exhibited a slight increase in body weight (b.w) throughout the first ten days of the experiment. After this point, the undernourished group showed no further increase in b.w., and exhibited significantly lower b.w. than controls at the end of the experiment. The cephalometric study showed that the length of the mandible as a whole, and of the condylar and angular processes was significantly lower in the undernourished group. In addition, significant differences in the vertical relation between the angular process to the mandibular corpus, the convexity of the angular process, and the ratio between total molar width (from the first to the third molar) and the length of the mandibular corpus were observed.

Orthodontic implications of protein undernutrition in mandibular growth: a cephalometric study in growing rats

Se presenta un trabajo experimental en el que se analiza el desarrollo de diferentes unidades mandibulares y su probable impacto en: la dirección del desplazamiento mandibular durante el desarrollo facial y en la relación entre las dimensiones mesiodistales de primero a tercer molar con la longituddel cuerpo mandibular en un modelo de desnutrición proteica y atrofia muscular de ratas en crecimiento. Se utilizaron ratas Wistar destetadas a los 21 días de edad y separadas en dos grupos denominados control (alimentado conuna dieta dura convencional ad libitum) y experimental (alimentado con una dieta deficiente en proteínas, harina de maíz, administrada ad libitum). A las cinco semanas de experiencia todos los animales fueron sacrificados, se disecaron las mandíbulas y se separaron a nivel de la línea media, se fijaronen formol al 10 por ciento y se removieron los tejidos blandos. A unahemimandíbula de cada animal se le realizaron marcas metálicas a nivel del agujero mentoniano y del agujero mandibular, posteriormente fueron radiografiadas. A partir de proyeccionesde las radiografías se obtuvieron trazados sobre los que se realizóel estudio cefalométrico. El peso corporal aumentó levemente en los primeros diez días de experiencia en ambos grupos. A partir de ese punto en el grupo desnutrido no se incrementó y fue significativamente menor que el grupo control al final del período experimental. El estudio cefalométrico mostró que las longitudes mandibular,del proceso condilar y del proceso angular fueron significativamente menores en el grupo desnutrido. Se encontraron además diferencias significativas en los valores quedefinen la relación vertical del proceso angular al cuerpo de la mandíbula, en la convexidad del proceso angular y en larelación entre la longitud mesiodistal total de primero a tercer molar con la longitud del cuerpo mandibular.

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis.

The present experimental study addresses the issue of the development and size of root resorption areas in molars of rats submitted to orthodontic forces of 51 or 75 g and the induction of periodontal disease by placing a cotton ligature around the cervix of the first upper molars for 48 hours. Immediately on removal of the ligature or 48 hs later we put an orthodontic device in place. The device comprised two steel bands. The arms of a helicoidal spring that exerted force towards palatine passed through the palatine tubes welded to the bands. The number of odontoclasts and the percentage of root resorption areas were determined histomorphometrically on bucco-palatine sections obtained at the level of the central roots. The data showed an increase in root resorption areas when the orthodontic forces were applied to molars of rats following the induction of periodontitis. The magnitude of the force was proportional to the size of the resorption areas and to the number of odontoclasts. Both these end-points exhibited smaller values when the forces were applied once the inflammatory reaction had subsided. The present study shows that the risk of development of root resorption areas in patients with periodontal disease submitted to orthodontic treatment would be lower if lighter forces were applied and treatment were delayed until the inflammatory signs have subsided.

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis

Se presenta un estudio experimental sobre la aparición y extensión de reabsorciones radiculares en molares de ratas sometidas a fuerzas ortodóncicas de 51 a 75 g y a las que se había inducido enfermedad periodontal por medio de la instalación de la instalación de una ligadura de algodón en el cuello de los primeros molares superiores que fue retirada a las 48 hs. A dicho tiempo o 48 horas después de retirada la ligadura se les instaló un aparato ortodóncico construido con dos bandas de acero por cuyos tubos palatinos pasan los brazos de un resorte helicoidal que ejerce fuerza hacia palatino. Sobre cortes histológicos bucopalatinos y a nivel de las raíces centrales se contó el númnero de odontoclastos y se determinó el porcentaje de áreas de reabsorción radicular por metodologías histomorfométricas. Los resultados obtenidos mostraron que esta última se incrementó cuando las fuerzas ortodóncicas se aplicaron a molares de ratas a las que se les había inducido periodontitis, que la magnitud de la fuerza empleada fue proporcional a la extensión de la reabsorción radicular y al número de odontoclastos y que ambos son menores cuando las fuerzas se aplican una vez reducidos los signos inflamatorios. Este estudio indica que el riesgo de aparición de reabsorciones radiculares en pacientes con enfermedad periodontal a los que se trata con ortodoncia sería menor si se aplicaran fuerzas de baja magnitud y si se esperara la remisión de los signos inflamatorios para la instalación de los aparatos.

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis

Se presenta un estudio experimental sobre la aparición y extensión de reabsorciones radiculares en molares de ratas sometidas a fuerzas ortodóncicas de 51 a 75 g y a las que se había inducido enfermedad periodontal por medio de la instalación de la instalación de una ligadura de algodón en el cuello de los primeros molares superiores que fue retirada a las 48 hs. A dicho tiempo o 48 horas después de retirada la ligadura se les instaló un aparato ortodóncico construido con dos bandas de acero por cuyos tubos palatinos pasan los brazos de un resorte helicoidal que ejerce fuerza hacia palatino. Sobre cortes histológicos bucopalatinos y a nivel de las raíces centrales se contó el númnero de odontoclastos y se determinó el porcentaje de áreas de reabsorción radicular por metodologías histomorfométricas. Los resultados obtenidos mostraron que esta última se incrementó cuando las fuerzas ortodóncicas se aplicaron a molares de ratas a las que se les había inducido periodontitis, que la magnitud de la fuerza empleada fue proporcional a la extensión de la reabsorción radicular y al número de odontoclastos y que ambos son menores cuando las fuerzas se aplican una vez reducidos los signos inflamatorios. Este estudio indica que el riesgo de aparición de reabsorciones radiculares en pacientes con enfermedad periodontal a los que se trata con ortodoncia sería menor si se aplicaran fuerzas de baja magnitud y si se esperara la remisión de los signos inflamatorios para la instalación de los aparatos. (AU)

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis.

The present experimental study addresses the issue of the development and size of root resorption areas in molars of rats submitted to orthodontic forces of 51 or 75 g and the induction of periodontal disease by placing a cotton ligature around the cervix of the first upper molars for 48 hours. Immediately on removal of the ligature or 48 hs later we put an orthodontic device in place. The device comprised two steel bands. The arms of a helicoidal spring that exerted force towards palatine passed through the palatine tubes welded to the bands. The number of odontoclasts and the percentage of root resorption areas were determined histomorphometrically on bucco-palatine sections obtained at the level of the central roots. The data showed an increase in root resorption areas when the orthodontic forces were applied to molars of rats following the induction of periodontitis. The magnitude of the force was proportional to the size of the resorption areas and to the number of odontoclasts. Both these end-points exhibited smaller values when the forces were applied once the inflammatory reaction had subsided. The present study shows that the risk of development of root resorption areas in patients with periodontal disease submitted to orthodontic treatment would be lower if lighter forces were applied and treatment were delayed until the inflammatory signs have subsided.