This retrospective observational study aims to evaluate the association between buccal prosthetic profile angles at different supraplatform zones and peri-implant tissue changes around bone-level dental implants restored with customized abutments and crowns. The main questions it aims to answer are:

Whether prosthetic profile angles within different vertical zones above the implant platform (0-2 mm and 2-4 mm) demonstrate different associations with marginal bone level changes around dental implants.

Whether buccal prosthetic contour angles at different supraplatform depths are associated with peri-implant soft tissue conditions, including keratinized tissue width and mucosal changes.

Whether peri-implant phenotype-related factors, including mucosal tunnel depth, soft tissue thickness, and buccal bone thickness, are associated with peri-implant tissue remodeling.

Researchers will retrospectively analyze clinical records, intraoral photographs, radiographic images, and cone-beam computed tomography (CBCT) scans collected during routine implant treatment and follow-up care up to 1 year after prosthetic loading. Buccal prosthetic contour angles will be measured at different vertical zones above the implant platform to evaluate the biologic influence of contour configuration at different peri-implant tissue levels.

This retrospective observational cohort study aims to evaluate the association between buccal prosthetic profile angles at different supraplatform vertical zones and peri-implant tissue remodeling around bone-level dental implants restored with customized abutments and crowns. Although prosthetic emergence profile and contour configuration have been associated with peri-implant biologic complications, limited evidence is available regarding the biologic influence of different buccal contour zones above the implant platform, particularly within the esthetic region. Existing studies have mainly focused on interproximal restorative contours, while the influence of buccal contour configuration at different vertical levels on peri-implant hard and soft tissue conditions remains unclear.

This study will retrospectively analyze patients restored with screw-retained or screwmentable implant-supported prostheses with customized abutments and at least 1 year of follow-up after prosthetic loading. Clinical records, intraoral photographs, radiographic images, and cone-beam computed tomography (CBCT) scans obtained during routine implant treatment and maintenance will be reviewed.

The primary objective is to evaluate whether buccal prosthetic profile angles measured at different vertical supraplatform zones demonstrate different associations with peri-implant marginal bone level changes. Buccal contour-related angles will include the overall buccal emergence angle, the buccal profile angle measured within 0-2 mm above the implant platform, and the buccal profile angle measured within 2-4 mm above the implant platform. These measurements are intended to investigate whether different peri-implant tissue levels demonstrate different biologic responses to prosthetic contour configuration.

Secondary objectives include evaluation of the association between prosthetic contour variables and peri-implant soft tissue conditions, including keratinized mucosa width (KMW), mucosal margin changes, probing depth, bleeding on probing, mucosal tunnel depth, and peri-implant soft tissue thickness. Additional peri-implant phenotype-related variables, including buccal bone thickness, implant placement depth, and soft tissue augmentation procedures, will also be analyzed for their potential association with peri-implant tissue remodeling.

Marginal bone level changes and peri-implant tissue conditions will be evaluated using clinical measurements, standardized intraoral photographs, vertical bitewing radiographs, and CBCT images obtained during routine follow-up care. CBCT analysis will be performed at 1 year after prosthetic loading to evaluate three-dimensional peri-implant bone morphology and prosthetic contour configuration.

Statistical analyses will include descriptive statistics and normality assessment. Depending on data distribution, Mann-Whitney U tests or Kruskal-Wallis tests may be used for supportive group comparisons when appropriate. Associations between peri-implant tissue changes and prosthetic contour variables will primarily be evaluated using univariable and multivariable linear regression analyses. Interaction analyses will also be performed to evaluate whether peri-implant phenotype-related variables modify the association between prosthetic contour angles and marginal bone level changes. Segmented regression analysis will additionally be performed to explore potential threshold effects associated with peri-implant tissue remodeling. All statistical tests will be two-sided with a significance level of α = 0.05.

The planned sample size is approximately 100 implant sites with complete clinical and radiographic follow-up records. Only cases with complete imaging quality and adequate follow-up documentation will be included in the final analysis. Missing or incomplete records, radiographic artifacts, severe image distortion, or inadequate maintenance follow-up will lead to exclusion from analysis.

Inclusion Criteria:

• Adults aged 20 years or older.
• Patients receiving at least one bone-level dental implant restored with a customized abutment and screw-retained or screwmentable prosthesis.
• Presence of at least one adjacent natural tooth and an opposing dentition.
• Implant sites that received second-stage surgery and prosthetic restoration.
• Presence of at least 2 mm of peri-implant keratinized mucosa after second-stage surgery.
• No buccal or peri-implant bone dehiscence following implant placement.
• Availability of complete clinical records, intraoral photographs, radiographic images, and cone-beam computed tomography (CBCT) scans with at least 1 year of follow-up after prosthetic loading.

Availability of adequate radiographic quality for peri-implant hard and soft tissue measurements.

Exclusion Criteria:

• Uncontrolled systemic diseases or medical conditions that may affect healing, including uncontrolled diabetes mellitus, metabolic bone diseases, autoimmune diseases, or history of head and neck radiotherapy.
• Current use of medications known to affect bone metabolism.
• Pregnancy, planned pregnancy, or breastfeeding.
• Poor-quality CBCT images or radiographic artifacts that interfere with measurement accuracy.
• Incomplete clinical or radiographic follow-up records.
• Poor oral hygiene or irregular supportive maintenance follow-up.
• Implant sites with prosthetic or imaging conditions preventing reliable evaluation of prosthetic contour configuration or peri-implant tissue measurements.

Adult patients receiving bone-level dental implant treatment with customized abutments and screw-retained or screwmentable prosthetic restorations at Chang Gung Memorial Hospital will be retrospectively included. Eligible participants will have completed two-stage implant surgery, prosthetic rehabilitation, and routine maintenance follow-up with available clinical records, intraoral photographs, radiographic examinations, and cone-beam computed tomography (CBCT) scans for at least 1 year after prosthetic loading. Implant placement, peri-implant soft tissue management, and follow-up procedures were performed under standardized clinical protocols by the same experienced clinician to minimize procedural variability. Patients with inadequate imaging quality, incomplete follow-up records, peri-implant bone dehiscence after implant placement, or systemic conditions affecting healing will be excluded.

Individual participant data will not be publicly available because of privacy and institutional data protection restrictions.