Tooth and Bone-borne Cutting/Repositioning Guide and Patient-specific Implant(PSI)

A Prospective, Randomized, Controlled, Single-blind Study on the Hybrid Tooth and Bone-supported Cutting and Repositioning Guides Versus Computer-aided Design/Computer-aided Manufactured Splints in "Surgery-first" Orthognathic Surgery

Dentofacial deformity refers to a group of disorders characterized by malocclusion and facial asymmetry resulting from developmental abnormalities of the maxilla and mandible, which cause morphological and positional anomalies of the jaws. Compared with the traditional orthodontics-orthognathic surgery-orthodontics treatment protocol, the surgery-first approach has witnessed a continuous expansion of its clinical application scope. Nevertheless, academic controversies persist regarding its indication boundaries, postoperative jaw stability, and adaptive changes of the temporomandibular joint.

In orthognathic surgery, computer-aided design/computer-aided manufacturing (CAD/CAM) surgical guides indirectly determine the three-dimensional spatial positions of the maxilla and mandible through occlusal relationships. The tooth-bone dual-supported osteotomy and positioning guide combined with pre-bent patient-specific implants (PSIs) forms a novel surgical guide system that enables independent and direct positioning of the maxilla. Theoretically, this system can eliminate errors derived from mandibular positional instability and thereby improve surgical accuracy. However, comparative studies investigating the clinical application of these two types of guides in surgery-first orthognathic surgery are still lacking.

This prospective, randomized, controlled, single-blind clinical study aimed to explore the clinical value of PSIs and conventional CAD/CAM guides in surgery-first orthognathic surgery, with primary outcomes focusing on surgical accuracy, postoperative jaw stability, and temporomandibular joint alterations. The findings will provide evidence-based medical support for the expanded application of this novel technique in precision orthognathic surgery.

Inclusion Criteria:

1. Age ranged from 18 to 40 years old.
2. Patients were diagnosed with dentofacial deformity and received treatment at the Plastic Surgery Hospital, Chinese Academy of Medical Sciences. The diagnosis was confirmed via comprehensive evaluation by two senior attending plastic surgeons.
3. Patients were scheduled for bimaxillary orthognathic surgery, with optional adjunctive procedures including maxillary and mandibular subapical osteotomy and genioplasty.
4. Patients were indicated for the surgery-first approach based on joint assessment by craniomaxillofacial surgeons and orthodontists. Orthodontists confirmed that satisfactory occlusal relationships could be achieved through postoperative orthodontic treatment. Preoperative dental conditions met the following requirements: no or mild anterior dental crowding, flat or shallow Spee's curve, slight incisor inclination, harmonious maxillary and mandibular dental arches, and at least three stable occlusal contacts under transitional occlusion.
5. Patients agreed to complete follow-up examinations and provided signed informed consent.

Exclusion Criteria:

1. Patients who refused to participate in the present study.
2. Presence of comorbidities that may increase surgical risks or impair surgical outcomes, as assessed by two senior plastic surgeons, including but not limited to hypertension, diabetes, immune thrombocytopenic purpura, and hemoglobin (Hb) level ≤ 100 g/L.
3. Presence of body dysmorphic disorder, a history of psychiatric disorders, or excessively demanding patients with unrealistic treatment expectations.
4. Presence of facial skeletal tumors.
5. Patients who required revision surgery after previous orthognathic procedures.
6. Cases judged unable to achieve stable occlusal relationships through postoperative orthodontic treatment following joint evaluation by craniomaxillofacial surgeons and orthodontists, including patients with severe dental crowding, maxillomandibular arch width discrepancy, temporomandibular joint disorders, or periodontal diseases.