Effect of low masticatory function on condylar growth: A morphometric study in the rat

The aim of this study was to estimate the influence of functional alteratio ns on the size of the mandibular condyle and to elucidate in detail, by mea ns of histomorphometric analysis, the effect of changing the consistency of the diet on different portions of the condylar cartilage in growing rats. Forty growing rats were randomly divided into 2 groups. One group received the normal hard diet for rats; the other group received a standardized soft diet. The experimental period was 28 days. Ten animals from each group wer e used for gross morphometric analysis; the other 10 animals were used for histologic analysis of the condyle, The morphometric analysis of the condyl ar cartilage was based on the 25th, 50th, and 75th percentiles of the medio lateral sections of the condyles. The sections were divided into 3 parts: t he anterior, intermediate, and posterior part; 4 measurements were performe d in each. Significant differences were found in the condylar length and wi dth between the groups, the soft diet group having a smaller condyle, The h istomorphometric analysis of cartilage thickness showed significant differe nces between the 2 groups, being thinner in the anterior part and thicker i n the posterior part of the condyle in the soft diet group. These routine h istologic findings cannot explain the gross morphologic differences in the condylar size between the groups; this means that increased condylar cartil age thickness is not necessarily evidence of increased condylar growth. The results from this study indicate that a low masticatory function leads to decreased growth of the condyle and changes in the thickness of the cartila ge. This may be the effect of an alteration in the stress distribution in t he temporomandibular joint area, because of the absence of large masticator y forces.