Analyzing the effects of tooth extraction on the lip in orthodontic treatment

Introduction: The aim of this study was to analyze changes occurring in the lip and facial soft-tissue profile after fixed orthodontic treatment, with or without tooth extraction, in patients with dental class II malocclusion.

Materials and methods: Measurements were made on cephalometric films of 75 individuals with dental class II malocclusion before and after fixed orthodontic treatment. The patients were divided into three groups: no extraction, extraction of upper two premolars, or extraction of four premolars. The parameters measured were: basic upper lip thickness (BULT), vermilion upper lip thickness (VULT), upper lip inclination (ULI), basic lower lip thickness (BLLT), vermilion lower lip thickness (VLLT), lower lip inclination (LLI), face axis angle (Ba-N/PtmGn), labiomental angle, facial convexity angle, and total face convexity angle. The results were analyzed statistically using the Wilcoxon, Kruskal-Wallis, and Mann-Whitney U tests.

Results: It was found that the VULT value in the group with no extraction was lower than the four-extraction group (P = 0.001; P < 0.05). The VULT value in the upper-two extraction group was significantly lower than that in the four-extraction group, and the Ba-N/PtmGn in the no-extraction group was lower than that in the four-extraction group (P = 0.001; P < 0.05).

Conclusions: These findings suggest that tooth extraction in orthodontic treatment may affect the vermilion upper lip thickness and facial axis, but that this does not have any negative effects on the soft-tissue facial profile. Premolar tooth extraction can be performed by establishing an accurate diagnosis and treatment plan to avoid undesirable and negative effects on the facial soft-tissue profile.