This study aimed to determine the optimum orthodontic force from a broader perspective. Interleukin (IL)-1β levels in human gingival crevicular fluid (GCF), pain intensity, and the amount of tooth movement were measured during canine retraction using different magnitudes of continuous orthodontic force. Sixteen subjects (two males and 14 females), aged 18-24 years, diagnosed with Class I bimaxillary protrusion and treated with first premolar extractions participated in this study. The upper canines were retracted with continuous forces of 50 or 150 g using nickel-titanium coil springs on segmented archwires. One of the lower canines was used as a control. GCF was collected from the distal site of each tooth at specific time points. IL-1β concentrations, pain intensity, using the visual analogue scale (VAS), and the amount of tooth movement were evaluated. One-way analysis of variance, Friedman, and paired t-tests were used for comparisons of IL-1β in GCF, the plaque and gingival indices, and the efficiency of tooth movement on pain perception, respectively. IL-1β concentration in the 150 g group showed the highest level at 24 hours and 2 months with significant differences compared with the control group (P < 0.05). The mean VAS score of pain intensity from the 150 g force was significantly greater than from the 50 g force at 24 hours (P < 0.01). However, no significant difference in the amount of tooth movement was found between these two different magnitudes of continuous force at 2 months. A 50 g force could effectively induce tooth movement similar to 150 g with less pain and less inflammation.