Aims: To (1) quantitatively investigate the possible long-term surgical impact of orthognathic surgery on the patients' trigeminal somatosensory functions and (2) investigate the influence of ongoing pain on the trigeminal somatosensory functions of the patients. Methods: A group of patients before orthognathic surgery (Pre-op), a group of patients 1 year after orthognathic surgery (Post-op), and a group of control participants (Control) were recruited (n = 28 in each group). A standardized quantitative sensory testing protocol was followed to record a battery of 13 parameters, which reflect both sensory loss and gain. The data were analyzed using three-way repeated measure analysis of variance with group and pain as between-subject factors and testing site as within-subject factor. Results: In the Post-op group, of the 21.4% patients who reported ongoing pain after surgery, 7.1% were diagnosed with neuropathic pain and 14.3% had musculoskeletal pain. Facial cold detection threshold (CDT) of the Post-op group was significantly lower (less sensitive) than that of the Pre-op group (P .039). Facial pressure pain threshold (PPT) of the Post-op group was significantly lower (more sensitive) than that of the Pre-op and Control groups (P .006). Masseter PPT of the Postop group was significantly lower than that of the Control group (P = .02). The facial vibration detection threshold (VDT) of the Post-op group was significantly higher (less sensitive) than that of the Pre-op and Control groups (P .014). Pain patients in the Post-op group showed significantly elevated VDT compared to patients without pain (P .001). Conclusion: The pattern of sensory alteration in orthognathic surgical patients with or without pain was characterized by sensory loss in thermal parameters and non-nociceptive mechanosensory parameters and sensory gain in nociceptive mechanosensory parameters. The elevated VDT might be a potential indicator of the impact of postoperative pain on trigeminal somatosensory functions. Keywords: musculoskeletal pain, neuropathic pain, orofacial pain, orthognathic surgery, quantitative sensory testing, somatosensory function