Korean J Orthod.  2018 May;48(3):182-188. 10.4041/kjod.2018.48.3.182.

Use of autonomous maximal smile to evaluate dental and gingival exposure

• Wang S
• Lin H
• Yang Y
• Zhao X
• Mei L
• Zheng W
• Li Y
• Zhao Z

• KMID: 2418329
• DOI: http://doi.org/10.4041/kjod.2018.48.3.182

Abstract

OBJECTIVE
This study was performed to validate the autonomous maximal smile (AMS) as a new reference for evaluating dental and gingival exposure.
METHODS
Digital video clips of 100 volunteers showing posed smiles and AMS at different verbal directives were recorded for evaluation a total of three times at 1-week intervals. Lip-teeth relationship width (LTRW) and buccal corridor width (BCW) were measured. LTRW represented the vertical distance between the inferior border of the upper vermilion and the edge of the maxillary central incisors. Intraclass correlation coefficients (ICCs) for reproducibility, and the m-value (minimum number of repeated measurements required for an ICC level over 0.75), were calculated.
RESULTS
LTRW and BCW of the AMS were 1.41 and 2.04 mm, respectively, greater than those of the posed smile (p < 0.05), indicating significantly larger dental and gingival exposure in the AMS. The reproducibility of the AMS (0.74 to 0.77) was excellent, and higher than that of the posed smile (0.62 to 0.65), which had fair-to-good reproducibility. Moreover, the m-value of the AMS (0.88 to 1.05) was lower than that of the posed smile (1.59 to 1.85).
CONCLUSIONS
Compared to the posed smile, the AMS shows significantly larger LTRW and BCW, with significantly higher reproducibility. The AMS might serve as an adjunctive reference, in addition to the posed smile, in orthodontic and other dentomaxillofacial treatments.

Keyword

Posed smile; Gummy smile; Gingival exposure; Dental exposure

MeSH Terms

Incisor
Volunteers

Figure

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  Figure 1 Examples of digital videography frames of one subject included in the study. A, The posed smile; B, the autonomous maximal smile.

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  Figure 2 A periodontal probe is used to measure the width of the maxillary central incisor edge and serves as a standard ruler for further measurement using the Photoshop software.

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  Figure 3 A, Measurement of lip-teeth relationship width (LTRW). A and B represent the midpoints of the two maxillary central incisors, respectively. O indicates the midpoint of AB. LTRW is the perpendicular distance from O to the inferior border of the vermilion. B, Buccal corridor width (BCW) is the sum of the horizontal distance from the lateral margin of the most posterior visible tooth to the inner commissure on both the left (L) and right (R) sides.

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  Figure 4 A and B, A videography frame of the subject with the most increase (the mean of three repetitions was over 3 mm) in lip-teeth relationship width from the posed smile to the autonomous maximal smile (AMS). C and D, A videography frame of the subject with the most increase (the mean of three repetitions was over 5 mm) of buccal corridor width from the posed smile to the AMS.

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  Figure 5 Statistical comparisons of lip-teeth relationship width (LTRW) and buccal corridor width (BCW) between the posed smile and the autonomous maximal smile (AMS). Data are presented as mean ± standard deviation. The AMS has significantly larger values of LTRW and BCW than does the posed smile. ***p < 0.001.

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  Figure 6 Statistical comparisons of lip-teeth relationship width (LTRW) and buccal corridor width (BCW) between men and women. Data are presented as mean ± standard deviation. No significant difference is found. AMS, Autonomous maximal smile.

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