ABSTRACT
The effects of protein malnutrition, both in utero and prior to weaning, on formation of the first mandibular molars were evaluated by phase-contrast and electron microscopy in rats. The nourished group (GI) received a diet that included 20% casein, while the malnourished group (GII) received 5% casein. The first mandibular molars from GII exhibited low density of cells and odontoblasts, which lacked regular organization compared with molars from GI. In addition, a difference in collagen type was observed between the groups, with a prevalence of Type III collagen fibers detected in the dentin, periodontal ligament, and alveolar bone of GII, and a prevalence of Type I collagen fibers in GI. Finally, examination of surface area in molar sagittal sections indicated 30% less dentin in GII, compared with GI. Our results suggest that structural and ultra-structural features of the dentin-pulp complex and periodontal components of rat molars are affected by protein deficiency.
ABSTRACT
Meniscectomy of the temporomandibular joint (TMJ) was frequently performed until a few years ago but now is seldom employed. This procedure induces important articular modifications but the complete extent of ultrastructural changes is still unknown. Twenty-one Wistar rats were submitted to unilateral meniscectomy. Animals were randomly divided into three groups and followed for 15, 35 or 60 days. After killing both meniscectomized and contralateral TMJ specimens were sectioned sagittally and prepared for light and scanning electron microscopy studies. Normal TMJs are characterized by glenoid fossa and condylar process with distinct conjunctive layers in which regularly arranged type 1 collagen fibres predominate. Meniscectomized animals initially exhibit a different tissue covering the eroded articular surface of the condyle with the prevalence of type 3 collagen fibres but type 1 fibres predominate in the late postoperative period. Subchondral cysts are clearly visible. A complex remodelling process of the TMJ after meniscectomy is evident with important ultrastructural modifications that may correlate to unsatisfactory clinical results. The dynamic nature of this process is also observed when specimens from different postoperative periods are compared. Surgeons should always bear in mind these alterations when indicating this procedure.
