[Skull deformities following unilateral mandibular imbalance. V. Discussion of results]

The unilateral dysbalance induced artificially in the mandibles of Beagles yields information regarding the action of the masticatory musculature as a local factor affecting craniofacial growth. Time is an important factor, particularly the age and maturity of the animals at the time of the operation and the length of the post-surgical interval prior to the measurements being taken. The time factor and differences between chewing types provide some explanation for the lack of uniformity and, sometimes, the contradictory nature of the available information regarding the secondary changes to the skull following the elimination of masticatory muscles in experimental animals. The cranial scoliosis observed as a result of mandibular dysbalance suggests strongly that the viscerocranium responds plastically to functional influences. The neurocranium, in contrast, whose shape is governed largely by the brain, is to great extent immune to such postnatal manipulations. The fact that growth of the residual mandibular stump is retarded shows that the condylar cartilage is not a primary growth centre. Postnatal mandibular growth is mainly periosteal and governed by functional stimuli. Any attempt to apply these results obtained with animal models to man must naturally take the differences between the structures of the maxillo-mandibular apparatuses into account.