Cone-beam computed tomography evaluation of palatal bone and soft tissue dimensions for orthodontic miniscrew placement

Objectives: Palatal mini-implants have become essential tools in orthodontic anchorage; however, their success depends on adequate palatal hard tissue thickness and acceptable soft tissue morphology. The objective of this study is to evaluate the thickness and distribution of suitable sites for palatal orthodontic mini-implant placement using cone-beam computed tomography (CBCT). Material and Methods: This retrospective analysis of CBCT images from forty-nine subjects (24 males, 25 females; age range 14–30 years) was conducted. Subjects were categorized into adolescents ( n = 24) and adults ( n = 25). Palatal hard tissue, soft tissue, and combined thickness were measured at four coronal planes corresponding to the first premolar (PM1), second premolar (PM2), first molar (M1), and second molar (M2) regions. Measurements were obtained bilaterally at 1-mm intervals from the midpalatal suture up to 10 mm laterally. Intra-examiner reliability was assessed using the intraclass correlation coefficient (ICC). A post hoc power analysis was performed to evaluate the adequacy of the sample size for detecting sex-related differences. Statistical analysis included two-way analysis of variance (ANOVA) to evaluate the effects of coronal plane and distance from the midline, along with one-way ANOVA and Mann–Whitney U tests to assess age and sex-related differences. Statistical significance was set at p < 0.05. Results: Intra-examiner reliability demonstrated good reproducibility (ICC = 0.766; 95% confidence interval: 0.537–0.890; p < 0.001). Palatal hard tissue thickness showed a consistent V-shaped distribution across all coronal planes, with maximum thickness at the midpalatal suture, minimum at 2–3 mm lateral to the midline, and gradual increase toward 10 mm. Mean hard tissue thickness differed significantly among planes ( p < 0.001), being greatest in the PM1 region (5.2 ± 1.4 mm), followed by the PM2 (4.8 ± 1.3 mm), M1 (4.1 ± 1.2 mm), and M2 regions (3.7 ± 1.1 mm). Combined hard and soft tissue thickness ≥7 mm was consistently observed in the PM1 and PM2 regions at 1–5 mm from the midpalatal suture in both adolescents and adults. Two-way ANOVA showed significant effects of coronal plane and distance from the midline ( p < 0.05). No statistically significant effects of age and sex were observed ( p > 0.05); however, post hoc power analysis revealed low statistical power (7.4%) to detect small differences between sexes, with observed effect sizes ranging from r = 0.022 to 0.305, indicating that the study was underpowered for detecting subtle sex-related variations. Conclusion: Palatal hard tissue thickness follows a consistent V-pattern with the PM1 and PM2 regions, particularly at positions 1–5 mm lateral to the midpalatal suture, which provide the most favorable anatomical conditions for safe and predictable palatal miniscrew placement.