The goal of this observational study is to learn the accuracy of tooth-bone dual-support osteotomy/location guide plate compared with conventional CAD/CAM interocclusal splints in "surgery-first" orthognathic surgeries.

The main question it aims to answer is:

Does the tooth-bone dual-support osteotomy/location guide plate performed better in accuracy? Does the tooth-bone dual-support osteotomy/location guide plate saved operation time? Participants already underwent orthognathic surgeries.

Inclusion Criteria:

1. Age: 18 to 40 years old.
2. Diagnosis: Patients treated at Plastic Surgery Hospital, Chinese Academy of Medical Sciences. Diagnosed with dentofacial deformity upon comprehensive evaluation by two senior attending plastic surgeons.
3. Surgical plan: Scheduled for bimaxillary orthognathic surgery, which may be combined with subapical osteotomy of the maxilla and mandible or genioplasty.
4. Treatment protocol: Cases eligible for the surgery-first approach after joint assessment by craniomaxillofacial surgeons and orthodontists. Orthodontists confirm that satisfactory occlusal relationships can be achieved via postoperative orthodontic treatment. Preoperative requirements are as follows: no or mild anterior crowding, flat or shallow Spee's curve, slight incisor inclination, harmonious maxillary and mandibular dental arches, and at least three stable occlusal contacts in the transitional occlusion.
5. Agreement to follow-up and signed informed consent form.

Exclusion Criteria:

1. Presence of comorbid diseases or symptoms that may increase surgical risks or compromise surgical outcomes, as determined by two senior plastic surgeons, including but not limited to hypertension, diabetes, immune thrombocytopenic purpura, and hemoglobin (Hb) ≤ 100 g/L.
2. Body dysmorphic disorder, history of psychiatric disorders, or excessively demanding patients with unrealistic expectations.
3. Facial skeletal tumors.
4. Revision surgery after prior orthognathic procedures.

Patients primarily diagnosed as "dentofacial deformities" who are scheduled for "surgery-first" bimaxillary orthognathic surgery.

They are cases eligible for the surgery-first approach after joint assessment by craniomaxillofacial surgeons and orthodontists. Orthodontists confirm that satisfactory occlusal relationships can be achieved via postoperative orthodontic treatment. Preoperative requirements are as follows: no or mild anterior crowding, flat or shallow Spee's curve, slight incisor inclination, harmonious maxillary and mandibular dental arches, and at least three stable occlusal contacts in the transitional occlusion.