Catch-up in mandibular growth after short-term dietary protein restriction in rats during the post-weaning period

Catch-up growth has been defined as growth with a velocity above the statistical limits of normality for age during a defined period of time which follows a period of impaired growth. Since no data are available on catch-up in mandibular growth, the present study was designed to estimate the dynamics of the mandibular size after short-term dietary protein restriction in rats during the post-weaning period. Weanling male rats, 22 d of age, were divided into two groups, control (C) and experimental (E). E rats were fed a protein-free diet during the first 10 d; from this time on, they were placed on a 20% protein diet, as were C rats during the entire experimental period, which lasted 70 d. Five rats from both groups were randomly selected every 10 d and sacrificed. Mandibular growth was estimated directly on the right mandible by measuring several dimensions (mandibular area, base length, mandibular height, mandibular length, alveolar length and incisor alveolar process length). Alveolar and incisor alveolar process lengths did not change with age or dietary protein. All other dimensions increased with age and were thus negatively affected by protein restriction. After growth restriction ceased, the rate of increase of all affected dimensions was above normal values and deficits were swiftly eliminated. Since age-independent dimensions compose roughly the anterior portion of the mandible, this portion of the bone was not affected by protein restriction. It was, thus, the posterior part of the mandible which stopped growth during the nutritional insult and showed catch-up during nutritional rehabilitation. In summary, the rat mandible has a high potential for catch-up during the post-weaning period, showing the ability to achieve complete catch-up in about 30 d.