Comparison of Subjective Experiences Between Patients Receiving Clear Aligners or Fixed Appliances

Inclusion Criteria: * Must be 18 years of age or older; * Must be in good general health; * Upper and lower arches were both involved in two groups; * The fixed appliances group must be treated with wires and brackets only with the initial arch wire of 0.012 NiTi ; * Must be willing to sign and give written informed consent in accordance with institutional and federal guidelines. Exclusion Criteria: * Once been undergoing with orthodontic treatment; * Experienced tooth ache recently; * Been diagnosed with contagious and/or systematical diseases; * Have taken any kind of painkillers three days before the initial treatment; * When Trait Anxiety Inventory (T-AI) shows a score believed to define a psychological state of over anxiety (male over 53 points and female over 55 points).