Background: The decision regarding the selection of extraction or non-extraction orthodontic treatment is a common challenge in orthodontic treatment planning.
Objectives: The objective of this study was to compare the effects of extraction and non-extraction orthodontic treatment on the soft tissue profile of borderline class I patients.
Material and methods: In this retrospective study, 70 patients were selected from among those referred to the Department of Orthodontics of the Faculty of Dentistry at Hamadan University of Medical Sciences in Iran. The inclusion criteria were skeletal class I, 4-10 mm of space deficiency, and the possibility of applying both extraction and non-extraction orthodontic treatment. All patients underwent fixed orthodontic treatment with the use of 0.022-inch-slot edgewise brackets. The patients were divided into 2 groups (n = 35) according to the 4-premolar extraction or non-extraction treatment plan. The 2 groups were compared by means of the cephalometric analysis.
Results: There were 11 males and 24 females at a mean age of 17.46 years in the non-extraction group, and 9 males and 26 females at a mean age of 18.46 years in the extraction group. The upper and lower incisors as well as the lower lip moved forward in the non-extraction group (lower lip to E‑plane = 0.87 ±1.39 mm, U1-SN = 2.83 ±8.03°, IMPA = 4.64 ±5.47°). The incisors and the lips moved backward in the extraction group (upper lip to E‑plane = -1.42 ±2.08 mm, lower lip to E‑plane = -1.56 ±1.97 mm, U1-SN = -7.63 ±9.02°, IMPA = -7.05 ±6.79°). The differences were statistically significant (p < 0.05). Mentolabial sulcus became more pronounced in the non-extraction group (1.92 ±2.73 mm; p < 0.001) and shallower in the extraction group (-1.90 ±4.2 mm; p = 0.000).
Conclusions: Orthodontic treatment can change the soft tissue appearance of the lower third of the face. The lips and the incisors moved forward in the non-extraction group and backward in the extraction group.
Keywords: Angle class I malocclusion; cephalometry; orthodontics; tooth extraction.