Background: Filler injections are commonly used to soften deep nasolabial folds (NLF) by restoring volume in the depressed parts of fold. Recently, a combination technique using hyaluronic acid filler and polydioxanone (PDO) thread significantly improves deep NLF and induced changes in smile.
Objective: This study retrospectively confirmed the effects of this combination therapy, focusing on smile changes.
Methods: The NLF was divided into 3 parts: the lateral folded part (LFP), medial depressed part (MDP), and central creased part (CCP). Between November and December 2021, 14 patients underwent the combination treatment; of these, 11 were enrolled, excluding 3 who were not properly followed up. On average, 5.82±0.87 (right) and 5.73±0.47 (left) PDO mesh threads (6.0 cm length) were sequentially inserted into the LFP, MDP, and under the CCP of each NLF. Following this, an average of 1.82±0.71 ml (right) and 1.92±0.75 ml (left) of the filler was also sequentially injected into each NLF in a similar manner. They were mainly placed in the superficial and deep fat layers in the entire NLF and sub-malar areas. Smile index was measured during the fully expanded smile stage. The follow-up period was 3 months. The results were estimated using pre- and post-operative photographs.
Results: Three months after the combination treatment, patients were pleased with the softening of their NLF. As indicated by the increased smile index (inter-commissural width/inter-labial gap), the old and expanded smile changed to younger and less expanded smile. The original smile type (eight and three patients with the commissure and cuspid types, respectively) remained unchanged. The contour changes in each smile varied according to the smile type. This could be explained by combination treatment’s NLF correction, which restricts facial expression muscle movement.
Conclusion: These results demonstrate definite evidence of softening of the NLF, a youthful smile, and an increased smile index.

Keywords: hyaluronic acid filler, nasolabial fold, polydioxanone thread, smile change, smile index

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