Force distribution in splinted anterior teeth

Abstract

For splinting periodontally involved upper anterior teeth, a straight arch form usually does not afford as favorable a prognosis as a curved arch form. A curved arch splint places the center of rotation posterior to the central incisor area. Occlusal pressure here in a curved arch form causes the splint to revolve about the center of rotation. Since this center is distal to the application of force, the stress applied to the periodontal support in the central area is more apical in direction than in a straight line splint. In the latter case the center of rotation passes through all the teeth in the apical third and causes a tipping movement. Occlusal force at the end of a curved splint also affords a more equitable distribution of stress to the other abutments. In a straight line splint the teeth toward the midline receive less stress from the horizontal rotation. In a natural dentition there is usually more torque on the upper than on the lower anterior teeth. This is true whether there is a fairly deep or a shallow vertical overbite. In a lower anterior curved arch splint, occlusal pressure in the central incisor area causes the splint to rotate around the center of rotation, which passes near the apical third of the canines. The teeth in the central area have stress exerted on the periodontal support in a more apical direction than in a straight arch splint. When we have a fairly deep overbite case with a curved arch, there is less torque on the lower splint than when there is shallow overbite. This is due to the line of force passing closer to the center of rotation in the deep overbite case, producing less torque. The reverse is true for the upper curved arch splint with a fairly deep overbite, which produces more torque than a shallow overbite.