The study aimed to compare the volume enhancement and the lifting capacity of two different hyaluronic acid gels for lip injection. Thirty-six Korean female patients were randomized into two groups according to the cross-linking degree of the hyaluronic acid filler injected. Using a fixed injection protocol, patients were injected with 1 mL of hyaluronic acid filler in the lips and followed up at four and 12 weeks after injection. Lip volume, lip projection, and columella-labial angle were measured using a 3-dimensional imaging system at each time point. Follow-up values were compared with baseline. Compared with pre-treatment values, there was a statistically significant increase in mean lip volume and lip projection at four and 12 weeks after injection, with no significant differences between the two groups. Lips injected with hyaluronic acid filler of intermediate cross-link density resulted in more acute angles than lips injected with lightly cross-linked hyaluronic acid. The difference was statistically significant at each follow-up time point. No serious complications were observed throughout the study period. Our results imply that in patients who want a prominent upper lip lift, lip injections using hyaluronic acid fillers with intermediate cross-linking density can be a good option due to their lift capacity. The degree of cross-linking may not be a significant determinant of simple lip volume augmentation when other variables are constant.
Keywords: 3-D surface imaging; columella-labial angle; cross-linking; hyaluronic acid; injectable fillers; lifting capacity; lip augmentation; lip lift; lip projection; nasolabial angle.