Zhengxian Zhu ¹ Lin Zhong ² Yicheng Zhao ³ Xiaoting Wang ¹ Wenhao Qian ^1* Niansong Ye ^4*

• ¹ Shanghai Xuhui District Dental Center, shanghai, China
• ² Shanghai Jing'an District Central Hospital, Jingan Qu, Shanghai, China
• ³ Department of Oral Prothodontics, Stomatological Hospital of Tianjin Medical University, Tianjin, China
• ⁴ shanghai hua guang private practice, Shangahai, China

Objective: To measure the palatal thickness of soft tissues and the density of cortical bones To measure the palatal soft-tissue thickness and cortical bone density to determine safe regions for the placement of orthodontic mini-implants and to examine the influence of sex and age on soft-tissue thickness and cortical bone density. Materials and Methods: Cone-beam computed tomography images of 42 patients (22 males, 20 females), including 21 adults and 21 adolescents, were examined for this study. The palatal soft-tissue thickness and cortical bone density were measured at the coronal planes between the premolars (P4-5), between the second premolars and first molars (P5-6), and between the first molars and second molars (P6-7). Results: Cortical bone density was greatest at P4-5, followed by and P5-6, P6-7 while The thickness of soft tissue was similar among the three planes. Cortical bone density decreased from anterior to posterior plane and from lateral to median. And Soft tissue thickness increased from the median to the lateral , and was similar anterior to the posterior. palatal thickness and cortical bone density are influenced by sex, age, and their interactions. The recommended and optimal sites for palatal orthodontic mini-implants were then mapped. The thickness of soft tissue revealed similar coronal planes, but the bone density varied. And 0°-60 °showed a mean thickness of 3.8mm,whereas at 60°-90°, it was 1.5mm. P4-5 had the highest bone density (>600HU), decreasing towards P6-7 (<600HU). Bone density decreased from 90 °to 0 °coronally whereas soft tissue thickness increased. Age, sex, and their interaction affected bone and soft tissues. Conclusions: Depending on soft tissue thickness and bone density, the preferred implant site tends to be more anterior and closer to the midpalatal suture region. Due to the diversity of palatal morphology among individuals, preferably with cone-beam CT.Generally, areas with high bone density tended to have thin soft tissue coronally, thus the preferred implant site tends to be more anterior to P4-5 plane and closer to 60 °-90 °.Considering individual variances, mapping recommended regions for palatal mini-implants was suggested.