Mandibular condylar process and tibial bone responses to bone loss stimuli. A histomorphometric study in growing rats

Abstract

This study analyze the effect of protein restriction on bone remodeling in mandibular condylar process and its impact on longitudinal bone growth, and compare this responses to that on the proximal tibia in growing rats. Wistar rats of 21 days were assigned to one of the following groups: control (fed a regular hard diet ad libitum) and experimental (fed a hard diet lacking protein ad libitum). Animals were euthanized five weeks after. Both bones were obtained and fixed in 10% formalin; the mandibles were hemisected at the symphysis. Remaining soft tissue was removed. Metallic landmarks were placed in the mandibular foramen of each hemimandible. The hemimandibles were radiographed in order to perform cephalometric studies. Tibial and condylar process length was recorded. Sections of the tibial metaphysis and mandibular condyle were obtained and stained with hematoxylin-eosin and toluidine blue. Histomorphometric determinations were performed on histologic sections of tibia and condylar process subchondral bone of both groups: protein restricted and control animals. The length of the tibia and the condylar processes was significantly lower in the experimental group. The histomorphometric analysis showed that the experimental group exhibit a significant decrease in bone formation surfaces associated with an increase in bone surfaces covered with lining cells in the tibia, and concomitant with an increase in bone resorption surfaces, in the condylar process. Tibia and condylar process bone volume was significantly lower in the experimental group.