Methods: Forty-four male rats received soft diet for a prolonged period so that they developed masticatory hypofunction. After 21 weeks, when their growth was over, they were divided into two groups: one group continued for six more weeks with soft diet (hypofunction group), while the other changed to ordinary diet with the aim to retrain their masticatory muscles (rehabilitation group). A third group of sixteen male rats (normal group) received ordinary (hard) diet during the whole experimental period and served as control. Bone micro-architecture parameters of the mandibular alveolar bone were calculated at the end of the experiment (27 weeks) using microtomographic histomorphometry (micro-CT). The height and width of the alveolar process were also measured.
Results: The alveolar process trabecular bone volume fraction (BV/TV) was found to be lower for the animals of the hypofunctional group in comparison to the normal (p<0.01) and rehabilitation (p<0.05) groups. Despite the significant improvement observed in the rehabilitation group, BV/TV was still lower than in the normal group (p<0.05) at the end of this experiment. All the other microtomographic parameters followed the same pattern of change; values for the rehabilitation group were between the two other groups, differing significantly from both of them. The alveolar process was significantly shorter in the normal group in comparison to both other groups (p<0.05). Both the normal and rehabilitation groups had a wider alveolar process than the hypofunctional group (p<0.05). Both alveolar height and width were significantly correlated with all histomorphometric parameters under study.
Conclusions: Masticatory function rehabilitation led to an improvement of alveolar bone quantitative and qualitative characteristics in adult rats, although the negative effects of hypofunction were not totally reversed during the period under study.