DENTITION Dental arch form The teeth are positioned on the maxilla and mandible in such a way as to produce a curved arch when viewed from the occlusal surface (Figure 1-2) This arch form is in large part determined by the shape of the underlying basal bone. The basic pattern of tooth position is the arch.on the basis of qualitative anth opologists general shape of the palatal ara being paraboioid.Usolipsoid.rotund.and have des horseshoe-shaped.An arch has long been known architecturally (as the word architecture itself implies)as a strong,stable arrangement with forces being transmitted normal to the apex of a catenary curve.The shape of the arch form of the facial surfaces of the teeth was thought by Currier to be a segment of an In the past,interest in arch form was directed toward finding an"ideal"or basic mean arch form pattern that functionally interrelates alveolar bone and teeth and could have clinical application.However,any ideal arch pattem tends toignore variance.a linical reality which suggests that adaptation mechanisms are more imp tant for occ sal stability than any ideal emplate Changes in arch form,within anatomical limits,do not have any significant effect on occlusion unless the change is in only one of the two dental arches. Discrepancies in arch form between the maxillary and mandibular arches positioned,as in severe mandibular retrognathism or rogathism.nsuch cases,the arch form distortion in one arch allows a better occlusion on the posterior aspect than is otherwise possible. Figure 1-2 The curvature of the maxillary (A)and 5DENTITION - 5 - Dental arch form The teeth are positioned on the maxilla and mandible in such a way as to produce a curved arch when viewed from the occlusal surface (Figure 1-2). This arch form is in large part determined by the shape of the underlying basal bone. The basic pattern of tooth position is the arch. On the basis of qualitative observations, anthropologists have described the general shape of the palatal arch as being paraboloid, U-shaped, ellipsoid, rotund, and horseshoe-shaped. An arch has long been known architecturally (as the word architecture itself implies) as a strong, stable arrangement with forces being transmitted normal to the apex of a catenary curve. The shape of the arch form of the facial surfaces of the teeth was thought by Currier to be a segment of an ellipse. In the past, interest in arch form was directed toward finding an "ideal" or basic mean arch form pattern that functionally interrelates alveolar bone and teeth and could have clinical application. However, any ideal arch pattern tends to ignore variance, a clinical reality which suggests that adaptation mechanisms are more important for occlusal stability than any ideal template. Changes in arch form, within anatomical limits, do not have any significant effect on occlusion unless the change is in only one of the two dental arches. Discrepancies in arch form between the maxillary and mandibular arches generally result in poor occlusal relationships. Arch form distortion in only one arch can be advantageous when the basal bone structure is incorrectly positioned, as in severe mandibular retrognathism or prognathism. In such cases, the arch form distortion in one arch allows a better occlusion on the posterior aspect than is otherwise possible. Figure 1-2 The curvature of the maxillary (A) and