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The lower incisor—Its influence on treatment and esthetics

1958; Elsevier BV; Volume: 44; Issue: 2 Linguagem: Inglês

10.1016/0002-9416(58)90165-9

1557-8488

John T. Lindquist,

Temporomandibular Joint Disorders

1. An attempt to evaluate various methods of relating the lower incisor to the skeletal and soft-tissue profile has been made. The methods studied were Tweed's Frankfort-mandibular incisor angle (FMIA), Downs's lower incisor to A-Po plane, Holdaway's lower incisor and chin point relationship to the NB plane, and Steiner's lower incisor to NB plane (angular and linear). 2. Cephalometric treatment records and photographs of eight of my cases were presented in an attempt to answer the following questions: Do all of these methods yield the same results? Do they contradict each other? Is there any relationship between the lower incisor and facial esthetics? Does the lower incisor position mean anything at all? 3. The methods studied for positioning lower incisors very rarely indicated the same result for any individual case. A wide divergence of results and direct contradiction were apparent. 4. For the group of cases as a whole, each method indicated fairly consistent but widely divergent results. Tweed's readings, for example, almost always placed the lower incisors in a much more upright or lingual position than Downs's. These two methods represented the extremes and were quite often directly opposite in their findings. 5. This consistency of results gives rise to the observation that a concept of treatment and facial esthetics must lie behind the origin of these formulas. The question was raised as to which came first, the concept or the formula. 6. The cephalometric results in the treated cases presented reveal marked changes in denture base relationships, recontouring, relocation of points A and B, and extensive bodily type of movement of the upper and lower incisors. It is my opinion that many of these changes would not have been possible without lingual movement of the lower incisors and anchorage preparation of the lower arch, where indicated. 7. It is my opinion that methods which employ angular readings and do not take the chin into consideration (such as Tweed's FMIA) have inherent weaknesses which reduce the consistency and usefulness of their results.