The importance of the tongue in the development of normal occlusion

Abstract

1. 1. Deficient mandibular arch form with irregularity of the incisors is a very common phase of malocclusion. Many instances of this cannot be accounted for by present theories of etiology. 2. 2. The basal bone of the mandible tends to approximate hereditary form and size, if given proper function. It initiates arch form prior to eruption of the teeth. In contrast, the teeth, as exoskeletal parts, have distinctly different laws of development and growth. After the crowns of the teeth migrate away from the basal bone into the oral cavity, the environmental forces there become potent factors in positioning the crowns of the teeth. 3. 3. Normal arch form requires sufficient dimension to accommodate the teeth. The most important natural forces which can increase mandibular arch dimension are those of the tongue. 4. 4. The normal expansive forces of the tongue are exerted to their maximum only when it can be accommodated within the mandibular arch. When the tongue, during deglutition, operates from a higher position, its expansive forces on the mandibular teeth are diminished. 5. 5. Certain mandibular arches are too narrow to accommodate the tongue between the buccal teeth during deglutition. Following sufficient orthodontic expansion of the posterior portion of the arch, the tongue assumes its normal position and can exert its normal expansive forces. 6. 6. If resumption of normal tongue action occurs early in the formation of the permanent denture, it results in marked growth in the mandibular arch. Arch dimension gained through the influences of normal tongue function tends to remain stable. The coordinating forces of the tongue, lips, and cheeks, when allowed to develop a proper equilibrium during the early stages of facial growth, usually maintain their balance. 7. 7. The highly abnormal form and the diminutive size of the mandibular arch found associated with congenital aglossia provide proof of the vital importance of normal tongue form and function to normal occlusion. © 1950.