## 2 Materials and Methods  
### Study Design  
This retrospective cross-sectional study was conducted at the Department of Dentistry, Faculty of Medical Sciences, University of Kragujevac, Serbia, based on CBCT scans obtained between July 2022 and April 2025. This study was approved by the institutional ethics committee (Approval ID: 01-14697) and carried out in accordance with the latest revision of the Declaration of Helsinki. The CBCT scans were originally acquired for various diagnostic and therapeutic purposes, including the evaluation of dental anomalies, pre-surgical planning, and other dental treatments. Among the reviewed cases, certain patients had undergone imaging as part of the clinical preparation for orthodontic mini-implant placement. CBCT scans with motion artifacts, metal interference, or compromised visibility of the anterior maxilla were excluded during the initial screening process. Only those individuals who met the predefined inclusion criteria were selected for further morphometric analysis, ensuring both clinical relevance and methodological consistency.  
The inclusion criteria encompassed patients aged 15 to 50 years with fully erupted permanent dentition in the maxillary arch (excluding third molars), the availability of high-resolution CBCT scans, and a confirmed Serbian ethnicity, as recorded in medical documentation. The selected age groups (15-20, 21-30, 31-40, 31-40, and 40+ years) were defined to represent different growth and remodeling phases relevant to bone morphology and orthodontic treatment planning. This stratification allowed for the assessment of potential age-related anatomical variations that could influence the clinical recommendations for safe and effective TAD placement [36; 37]. Similar studies investigating alveolar bone morphology and TAD placement often employ comparable age group stratifications to reflect growth and remodeling phases relevant to orthodontic treatment planning [38].  
Given the broad clinical use of orthodontic mini-implants in both younger individuals during the early permanent dentition phase and older adults undergoing pre-prosthetic evaluation, this study was designed to reflect a wide age spectrum for a comprehensive population-based assessment [39; 40; 41; 42].  
Patients were excluded if they exhibited clinical or radiographic signs of periodontal disease or had any pathological conditions affecting maxillary hard or soft tissues. Additional exclusion criteria included the presence of anterior malocclusions--such as severe crowding, spacing, or abnormal axial inclinations; retained deciduous teeth; fixed orthodontic appliances; as well as crown-size anomalies like microdontia or macrodontia. To minimize anatomical variability, only individuals with average-sized maxillary incisors were included [43]. All participants (or legal guardians in the case of minors) provided written informed consent. Image evaluation and morphometric measurements were performed by a dentomaxillofacial CBCT expert (M.P. and M.V.).  
Two independent observers who made the measurement were blind to the protocol and showed high inter-rater reliability ([PERSON]'s r = 0.95). The mean value for each parameter was taken for further evaluation.  
Sample size estimation was conducted using G*Power software (version 3.1.9.6), applying a one-sample Wilcoxon signed-rank test from the \(t\)-test family. The calculation was based on a significance level of 0.05, a statistical power of 95%, and a medium effect size of 0.5, as recommended in the previous literature [30]. The resulting minimum sample size was determined to be 62. Ultimately, 65 patients were included in the study (23 males [35.4%] and 42 females [64.6%]), with a mean age of 29.83 \(\pm\) 11.14 years. To facilitate subgroup comparisons, participants were classified into four age categories: 15-20, 21-30, 31-40, and over 40 years.