DIAGNOSTIC LINE

1. 1. There are many different facial types with harmonious soft-tissue profiles and lip balance. 2. 2. The common cephalometric denominator for a harmonious soft-tissue profile and lip balance is the position of the incisal edge of the lower incisor relative to the AP line. Positioning too far forward of the AP line makes a protrusive lower lip and too far back makes a retrusive lower lip. To create well-balanced lips, the optimum position is on or near the AP line. 3. 3. The influence of variations in the apical base difference on soft-tissue profile and lip balance is well compensated for by placing the incisal edge of the lower incisor on or near the AP line. 4. 4. Whether a case should be treated with or without the removal of teeth is determined by a series of five test questions. 5. 5. Differential arch-length adjustment provides the latitude needed in the treatment of various skeletal patterns to position the denture appropriately to the soft-tissue profile and thus create harmonious balance of upper and lower lips. 6. 6. The distribution of relative root surface areas of the teeth between the anterior and posterior segments of the dentition will determine the site of extraction that, for treatment purposes, will result in soft-tissue profile harmony and balanced lips. 7. 7. The influence of the lower incisor position on upper and lower lip balance is significant. The apical base may vary considerably from the normal range and the angulation of the lower incisor may fluctuate, but the incisal edge of the lower incisor must lie at or near the AP line to create upper and lower lip balance. The angulation of the lower incisor to a cranial landmark is immaterial to either facial esthetics or denture stability. The angulation of the lower incisor, therefore, is not a criterion of successful therapy, nor is it of diagnostic interest. © 1969.