[A clinical review with special focus on craniofacial duplication]

To review the clinical research progress of craniofacial duplication, improve clinicians' recognition of this disease, and provide theoretical basis and practical references for its precise diagnosis and individualized treatment.

Recent domestic and international literature on craniofacial duplication as well as the diagnosis and treatment experiences of clinical cases in our team were reviewed. A comprehensive elaboration was conducted from embryonic development, etiological hypotheses, clinical classification, imaging manifestations, multidisciplinary diagnosis and treatment strategies, and prognostic follow-up. Special focus was placed on summarizing clinical features of jaw duplication, characteristics of occlusal disorder, and sequential orthodontic-orthognathic combined therapy.

Craniofacial duplication is an extremely rare congenital craniofacial developmental malformation with highly heterogeneous phenotypes, involving multiple structures including lips, oral cavity, maxilla, and mandible. It is often complicated by cleft lip and palate, cervical vertebral fusion, hypertelorism, muscular dysfunction and other deformities, severely impairing patients' mastication, phonation, deglutition, and facial aesthetics. Due to its extremely low incidence, scattered reported cases, and unclear pathogenesis, unified diagnostic criteria and therapeutic specifications have not been established worldwide. Developmental disorders of pharyngeal arches and cranial neural crest cells at embryonic weeks 4-8 are the core pathogenic trigger. The five etiological hypotheses have limited evidence levels, and no single theory can explain all clinical subtypes. The PAX7 gene variant identified by our team only serves as a genetic clue without functional verification to confirm its pathogenicity. The modified Hamberis 3-type classification and Sun 4-type mandibular duplication classification can clearly define the lesion scope, with matched surgical procedures, orthodontic regimens and recurrence risks for each subtype. Cone-beam computed tomography (CBCT) combined with three-dimensional reconstruction acts as the gold standard for diagnosis, and multidisciplinary sequential therapy can ameliorate facial appearance and oral function. Nevertheless, long-term follow-up data are scarce, and clinical management mainly relies on individualized experiences of clinicians.

Craniofacial duplication features complicated pathogenesis characterized by duplicated jaws, lips, and dental arches, with dysregulated development of embryonic pharyngeal arches and cranial neural crest cells as the core inducement. CBCT three-dimensional reconstruction enables accurate diagnosis, and multidisciplinary sequential therapy represents the optimal intervention strategy. Shortcomings including scarce clinical cases, unidentified pathogenic genes, absent standardized therapeutic protocols and insufficient long-term follow-up evidence remain prominent. Future research directions include constructing a multi-center case registry, conducting functional research on pathogenic genes, popularizing digital diagnosis and treatment techniques, and formulating standardized diagnostic and therapeutic guidelines. For pediatric patients with suspected malformations, CBCT examination should be performed as early as possible, and the principle of early diagnosis, early planning and early intervention shall be followed to restore oral function and optimize maxillofacial appearance.