The goal of this observational study is to learn how the health and thickness of the gums and supporting bone around the teeth change over 6 months in adults having jaw surgery to correct the bite. The main questions it aims to answer are:

• Do gum and tooth-support measurements change from before surgery to 1, 3, and 6 months after surgery?
• Do CT scan-based measurements of the tooth-supporting bone change over the same time period?

Participants will:

• Have a gum check-up (periodontal examination) before surgery and at 1, 3, and 6 months after surgery.
• Have CT scan-based measurements (CBCT) taken at the same time points for study assessment.

This two-center prospective observational cohort study will enroll adult patients who are scheduled to undergo orthognathic surgery according to standard clinical indications. Orthognathic surgeries will be performed at Kocaeli Health and Technology University, while periodontal clinical examinations and CBCT-based assessments will be conducted at Trakya University. Participants will be evaluated at baseline (preoperatively) and at 1, 3, and 6 months after surgery. Clinical periodontal assessments will include predefined periodontal phenotype-related parameters recorded using a standardized protocol. CBCT datasets will be obtained and analyzed using a standardized measurement protocol to assess buccal alveolar bone-related parameters and the presence of dehiscence/fenestration where applicable. To minimize assessment bias, CBCT images will be coded and evaluated by an independent assessor blinded to surgical details and group classification, and clinical periodontal examinations will be performed by an examiner blinded to the surgical procedure details.

Inclusion Criteria:

• Adults aged ≥18 years.
• Presence of a Class III molar relationship of any severity at baseline.
• Presence of a Class II molar relationship of any severity at baseline.
• Presence of transverse arch discrepancies.
• Presence of vertical maxillary excess.
• Presence of maxillary and/or mandibular asymmetry.
• Presence of anterior open bite.
• Full permanent dentition up to the first molars, with no supernumerary teeth and no agenesis (congenital absence) of teeth up to the first molars.
• No previous orthodontic treatment.
• No history of tooth extraction other than second or third molars.
• Availability of complete baseline and end-of-follow-up periodontal parameters and phenotype records suitable for evaluation.
• Healthy periodontium with no signs of gingival hypertrophy.
• No systemic disease history or medication use that could affect gingival/periodontal conditions.

Exclusion Criteria:

• Patients planned for orthodontic camouflage treatment with fixed appliances for Class II/Class III correction instead of orthognathic surgery.
• History of interproximal enamel reduction (interproximal stripping).
• Presence of dental implants.
• Age < 18 years.
• Pregnant or breastfeeding individuals.
• Any systemic condition contraindicates orthognathic surgery.
• Psychiatric disorders.
• Syndromic conditions.
• History of previous orthognathic surgery.
• Refusal to sign the informed consent form.
• Individuals belonging to a vulnerable population.

Adult patients referred for orthognathic surgery to the Department of Oral and Maxillofacial Surgery at Kocaeli Health and Technology University and subsequently evaluated at the Department of Periodontology at Trakya University

Individual participant data containing personal health information will not be shared due to privacy and confidentiality requirements, as well as ethical restrictions and applicable standards