RESUMO
Since no data are available to characterize mandibular growth in nonorganic nutritional dwarfing (ND), the purpose of the present study was to describe the effects of a diet on mandible and femur growth in a nutritional dwarfish animal model. Male Wistar rats were divided into two groups of 10 animals each: Control (C) and Experimental (E80: diet-restricted group). C rats were fed a standard diet ad libitum. E80 rats received 80
of the amount of standard diet eaten by group C. Food intake and body weight (Wt) and length (Lt) were recorded periodically. Growth data (Wt and Lt) were expressed as a Z-score of weight-for-length (WLZ) ratio, an index of body size. Five animals of each group were selected at random at 4 and 8 weeks and sacrificed. Additionally at t = 0, 5 animals were sacrificed for baseline measurements. Mandibular growth was estimated directly on the right mandible by measuring ten dimensions. Femur growth was estimated from Wt and Lt measurements of the bone. Mandibular weight, area, length and height were negatively affected by dietary restriction during the first 4 weeks of the experimental period. Mandibular growth ceased after this point. Dimensions corresponding to the alveolar unit did not change with time. However, all other dimensions were negatively influenced but not to the same extent. Femur rather than mandibular weight was severely affected. Therefore, the negative effects of the nutritional stress that occurs after weaning would be stronger for the femur, than for the mandible. Femur length was also negatively affected by suboptimal nutrition. In summary, the results of the present study showed that mandible and femur growth respond differently to mild chronic food restriction. These observations could be explained in terms of the different critical bone growth periods and of the time at which nutritional stress was imposed.
RESUMO
Dietary protein restriction adversely affects mandibular growth in the weanling rat. Protein deficiency is usually accompanied by reduced food intake which, in turn, induces energy deficiency. The present study was thus designed to dissociate the effects of dietary protein and energy deficiencies on the growth of the mandible in rapidly growing rats. Four groups of Sprague-Dawley rats aged 30 days were fed a normal diet, a low-energy diet, a low protein diet, and a low-protein and low-energy diet for 20 days. Rats were sacrificed at the end of experimental period and body weight and mandibular dimensions were recorded to evaluate body growth and mandibular growth. The growth of the mandible was affected almost in the same order of magnitude by both protein and energy restrictions. When both were applied together, mandibular growth was even more severely affected. Two way analysis of variance revealed the absence of synergism between variables, indicating that the negative effects of dietary protein and energy restrictions on mandibular growth could be considered to be additive.