Purpose: To investigate the changes of nasolabial soft tissues before and after full-arch implant supported fixed restoration in maxillary edentulous patients and the influencing factors of the changes.
Methods: Fifty patients who underwent full-arch implant fixed restoration in the Department of Second Dental Center of Shanghai Ninth People's Hospital from January 2016 to July 2023 were selected. Patient's medical history, CBCT, and three-dimensional facial scan data were collected before and after restoration. Paired t test or Wilcoxon signed-rank test were used to compare the changes in soft tissues before and after restoration. The correlation between changes and patient's basic information, implant protocol and residual bone parameters were analyzed using bivariate correlation analysis. Akaike information criterion was used to select the multivariate linear regression model of each soft tissue index change.
Results: After implant fixed restoration, the upper lip height (sn-sto), the upper vermillion height (ls-sto), and the upper vermilion area (UVA) significantly increased (P＜0.01), while the distance from ls to the E-line (ls-E) significantly decreased (P＜0.01), the nasolabial angle (∠cm-sn-ls) significantly decreased (P＜0.01), and the cutaneous upper lip height(sn-ls) did not change significantly(P＞0.05). Except for sn-sto and sn-ls, the remaining soft tissue changes were positively correlated with age (P＜0.01). Other residual bone parameters, implant protocol, and gender were not significantly related to each soft tissue change. Multivariate stepwise regression analysis showed that each soft tissue change was broadly related to age and preoperative soft tissue condition, and partially related to bone morphology.
Conclusions: The nasolabial soft tissues of maxillary edentulous patients change significantly after implant fixed restoration, mainly the expansion and protrusion of the red part of the lip. The changes in facial soft tissues are primarily related to the patient's age and pre-existing soft tissue condition, with older patients and those with more atrophic original soft tissue morphology observing more apparent improvements in fullness. The change in lip prominence is also related to the residual bone shape.