Evaluation of cortical bone thickness of the hard palate for mini-implant placement by cone-beam computed tomography

Introduction: Orthodontic mini-implants are widely placed in the palate. Cortical bone and soft tissue thickness of the palate are important factors for determining the location of mini-implants. The present study investigated the palatal cortical bone thickness using cone-beam computed tomography (CBCT). Materials and methods: In this descriptive-analytical trial, 150 eligible CBCTs were selected from males and females in two 19‒40 and 8‒18 age groups. Cortical bone thickness was measured on 8 coronal slices (with 3-mm distances from the incisive foramen) at 0 (midline), and 3- and 6-mm distances from the palatal midline using On Demand 3D software. Data were analyzed with Student’s t-test between two age groups and genders while repeated measures ANOVA was used to analyze data on anterior, middle and posterior areas of the palate (α=0.05). Results: Cortical bone thickness means were 1.38±0.28, 1.1±0.33 and 1.16±0.43 mm in the anterior, middle and posterior regions, respectively (p value < 0.001). Cortical bone was thicker in males at 3-mm distance from the midline compared to females (p value < 0.001) and in the 19‒40 age group compared to the 8‒18 age group (p value < 0.03). There were no significant differences between the two age groups and genders in cortical bone thickness at midline and at 6-mm distance from the midline. Conclusion: Under the limitations of the present study, the anterior region of the palate exhibited the thickest cortical bone; however, mini-implants can be placed in the posterior areas due to the adequate bone thickness.  Key words: Hard palate, Cone-beam computed tomography, Orthodontic appliances.