Available online 22 March 2024

Author links open overlay panel, , , , , , ABSTRACTStatement of problem

The esthetic assessment of smile lines by laypersons is a subject of ongoing debate. However, smile lines often appear with different types of upper lip curvature, which further complicates the esthetic assessment process, and studies on this combination are lacking.

Purpose

The purpose of this clinical study was to investigate a layperson’s esthetic perception of smile lines and upper lip combined images.

Material and methods

Twenty-six smile images resulting from combinations of 3 upper lip types, 4 anterior smile line types, and 3 posterior smile line types were generated by an image editing software program. Eighty-three laypersons (39 men and 44 women; 18 to 35 years of age) completed rating images using a visual analog scale. Unattractive smiles were designated to be those with scores <50 and attractive ones with scores ≥50. Data were analyzed using 1-way analysis of variance and Bonferroni post hoc tests (α=.05).

Results

High anterior smile line with gingival display >4 mm obtained significantly lower scores of <50 when combined with all upper lip curvatures (upward: 28.29 ±22.79, straight: 38.74 ±23.00, downward: 30.67 ±22.25, P<.01). High anterior smile lines with gingival display ≤4 mm combined with upward and straight upper lip curvature images obtained significantly higher scores, and all were ≥50 (upward: 63.24 ±22.22, straight: 61.40 ±21.58, P<.01).

Conclusions

From a layperson’s perspective, high anterior smile lines with gingival display >4 mm combined with any lip type were determined to be unattractive. If gingival display was ≤4 mm combined with both upward and straight lip types, the smile was assessed as attractive.

Section snippetsMATERIAL AND METHODS

This cross-sectional observational study was approved by the institutional review board of the Peking University Medical Ethics Committee (PKUSSIRB-202387066) and conducted in accordance with the World Medical Association Declaration of Helsinki. Written informed consent was obtained from all participants according to the guidelines of the research committee. A total of 100 laypersons were recruited to score the smile images generated by an image editing software program (Adobe Photoshop CS6;

RESULTS

Seventeen raters submitted incomplete data. Scores from 83 raters with an average age of 25.53 ±0.45 years old (39 men and 44 women) were collected and calculated after data filtering (Fig. 1). No statistically significant difference in scores was found between men and women (48.70 ±26.96 versus 48.60 ±23.93, P=.924). The image with the combination of average-ASL, average-PSL, and upward-ULC was assessed with the highest score 65.81 ±23.95, while the lowest score of 26.61 ±21.96 was obtained

DISCUSSION

This study investigated the esthetic perception of smile lines and upper lip combined images of 83 laypersons. The result data indicated that excessively high ASL with a gingival display >4 mm obtained scores <50 when combined with all ULCs (P<.05). A high-ASL group with gingival display ≤4 mm combined with upward-ULC or straight-ULC images obtained scores ≥50 (P<.05). Statistically significant differences in VAS scores were found when assessing the esthetics of ASL and PSL combined with

CONCLUSIONS

Based on the findings of this clinical study, the following conclusions were drawn:

1.

The excessively high ASL with a gingival display >4 mm was unattractive in all ULC types, with the most unattractive observed in the upward type.

2.

The high-ASL with a gingival display ≤4 mm was considered as attractive in upward and straight upper lip curvatures.

3.

Three types of PSL were considered as attractive in upward- and straight-ULC but all unattractive in the downward type.

PATIENT CONSENT

This research was conducted in accordance with the World Medical Association Declaration of Helsinki and approved by the Institutional Review Boards of the Peking University Medical Ethics Committee (PKUSSIRB-202387066). Written informed consent was obtained from all participants by following the guidelines of the committee for the research process.

Acknowledgments

The authors thank all participants for their time and consideration.

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