Abstract
BackgroundTo investigate the area and morphological changes around the soft tissue chin after orthodontic incisor retraction.MethodsFifty-nine female adults with bimaxillary protrusion requiring extraction of four premolars were included in the study. Cephalograms were taken before (T0) and after (T1) orthodontic treatment. The soft tissue changes, including the area, thickness and morphology were measured. Paired-t tests were performed for statistical comparisons. Pearson correlation analyses and backward multivariate regression analyses were used to identify the relationship between the soft tissue changes and incisor retraction.ResultsFollowing the incisor retractions (5.35 ± 1.79 mm and 4.42 ± 1.62 mm for the upper and lower, respectively), there was a significant increase in the soft tissue thickness of L1c-LL (0.64 ± 1.67 mm, P = 0.025) and Pog-Pog’ (0.44 ± 1.10 mm, P = 0.022), and a significant decrease in the soft tissue thickness of B-B′ (1.21 ± 1.34 mm, P < 0.01). Changes in the area of soft tissue chin and lower lip were not statistically significant (P > 0.05). Pearson coefficient between the thickness changes of B-B′ and the retraction of lower incisors was − 0.376. The multiple correlations between the soft tissue thickness changes and incisor retractions were Y = 1.02–0.42a + 0.42b for L1c-LL, and Y = 0.17–0.31b for B-B′.ConclusionsThe orthodontic incisor retraction could cause soft tissue thickness changes (i.e. an increase in L1c-LL and Pog-Pog’ and a decrease in B-B′) without area changes.
Highlights
To investigate the area and morphological changes around the soft tissue chin after orthodontic incisor retraction
It has been found that the public increasingly pays attention to the lips and soft tissue chin rather than to other orofacial structures when assessing facial esthetics [2]
Several studies and clinical trials have shown that these changes of soft tissue chin were mainly due to the redistribution or reshaping of the soft tissues around the chin area following the retraction of incisors [5]
Summary
To investigate the area and morphological changes around the soft tissue chin after orthodontic incisor retraction. The soft tissue chin in patients with dental protrusion, is strained resulting in undermined chin prominence [3]. The orthodontic treatment of bimaxillary protrusive patients usually involves the extraction of premolars and retraction of anterior teeth, which results in increased chin prominence and improved facial profiles [4]. Though it is possible to simulate soft tissue changes for patients with dental protrusion and extraction treatment by using some visual treatment objective (VTO) software, it is still difficult to accurately predict the soft tissue changes in the chin area following the orthodontic incisor retraction [8,9,10]
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