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Abstract:
One aspect of post adolescent growth is the continued downward growth of the upper lip and the reduced incisor display upon smiling. The aim of this study was to determine the long-term change in upper lip position relative to the incisor edge. Fifty four post retention subjects who had lateral cephalometric radiographs (ceph) taken at end of treatment (T2), ten years post retention (T3), and twenty years post retention (T4) were taken from the University of Washington, Seattle post retention records. On each ceph the length of the upper lip, anterior and posterior facial height, and positions of the maxillary and mandibular incisors were registered. The results indicated that the upper lip growth was continuous throughout the time monitored. In males there was more growth between T2-T3 than there was in females in both lip length and facial skeleton growth. From T3-T4 skeletal growth showed relative stability in both sexes and there was a continued growth in upper lip length relative to the incisor edge in both sexes. In conclusion, there is continued growth seen in upper lip position relative to the incisor edge in throughout the time periods monitored in this study and males have a higher predilection to facial skeletal growth between times T2-T3 than do females.
Smiles are what orthodontists create and fix. One important aspect in smile aesthetics is the upper lip line at rest, during speech and on smiling. In girls there is approximately 3.5 mm of incisor display at rest, which is twice that of boys, and roughly 90%-100% incisor display upon smiling, with slightly more in girls.
Facial structure growth is not complete upon maturity. In the third decade the anterior facial height continues to grow about 1.5 mm, primarily in the lower facial third. Simultaneously the maxillary and mandibular teeth continue to erupt to remain in occlusion. There is little data regarding soft tissue changes throughout life. The nose continues to grow causing the nasolabial angle to decrease, the soft tissue of the chin becomes more prominent, and the upper lip loses its thickness but maintains its length through the thirties. Observation of elderly indicates that around the sixth to seventh decade the smile aesthetics decreases primarily due to the increase in upper lip length.
During orthodontic treatment it is relative easy to position the upper teeth to obtain an aesthetic smile, however it is difficult to predict what will result in a pleasing smile that will persist through the fifth decade of life. An aesthetic smile upon completion of treatment might soon become less aesthetic due the continued growth of the upper lip. The difficult question becomes, what should be the final position of the upper incisors in relation to the upper lip to achieve a result with optimal esthetics and stability? One reason for the difficulty in this question is the lack of data pertaining to this question. Therefore the reason for this study was to determine the changes in position of the upper lip relative to the incisal edge through three decades of life.
Through cephalometric analysis it was found that the males from T2-T3 experienced more facial skeletal growth when compared to the females with greater growth in the length of the upper lip than that of skeletal growth so the position of the upper lip to the incisal edge decreased by about 1.3 mm in males, but there was no change in the female group. Both groups had little skeletal growth from T3-T4, but the lip continued to grow causing a decrease in incisal display of about 1 mm in males and 1.5 mm in females.
In conclusion, from T2-T3 the postadolescent growth of the craniofacial skeleton balances the increase in upper lip length so there is little change in incisal display. From T3-T4 there is lack of craniofacial skeletal growth and the increase in upper lip length results in a decrease in incisal display in both sexes.
References
Fudalej P. Long-term changes of the upper lip position relative to the incisal edge. Am J Orthod Dentofacial Orthop. 2008;
