Abstract： Objective:To evaluate the influence of the sleeve lengths and implant lengths on accuracy of static computer-assisted implant surgery (sCAIS).Methods:Twenty-eight models of bilateral mandibular single tooth loss were included. Fifty-five implants were placed under the guidance of sCAIS (Straumann Bone Level 4.1 mm×10 mm). According to the height of metal sleeve of static guide plate, 55 implants were divided into 11 groups (free hand group, 1 mm group, 2 mm group, 3 mm group, 4 mm group, 5 mm group, 6 mm group, 7 mm group, 8 mm group, 9 mm group, 10 mm group), with 5 implants in each group. Eight research models were included. Group with 5 mm sleeve guides were used to place implants of different length, (Straumann Bone Level width 4.1 mm, height was 8 mm, 10 mm and 14 mm), 5 implants in each group. Eighteen patients with mandibular single tooth loss were included in the Department of Oral Implantology, Tianjin Stomatological Hospital from October 2018 to June 2019. There were 10 males and 8 females, 18-46(33.7±7.9) years old. A total of 18 implants were implanted and divided into 3 groups (free hand group, 3 mm group and 5 mm group) with 6 implants in each group. Digital software was used to compare the implant positions before and after implantation. Non-parametric Kruskal-Wallis test or one-way ANOVA were used to analyze the results.Results:There was no significant difference in implant vertical deviation between different sleeve height groups (1-10 mm) and free hand group, but the neck deviation in free hand group[(1.04±0.13) mm] was significantly higher than that in different sleeve height groups (1-10 mm) ( P<0.05). The tip deviations of free hand group, 1 mm group and 2 mm group [(1.32±0.43), (0.83±0.10) and (0.78±0.11) mm, respectively] was significantly higher than that of 10 mm group [(0.31±0.14) mm]( P<0.05). The angle deviation of free hand group and 1 mm group (3.99°±0.85° and 2.59°±0.69°), respectively] was significantly higher than that of 10 mm group (0.61°±0.03°) ( P<0.05). The tip deviations of implants in the 14 mm group [(0.83±0.22) mm] was significantly higher than that in the 8 mm and 10 mm groups [(0.44±0.07) and (0.49±0.06) mm, respectively]. Clinical studies showed that there was no significant difference in neck deviation, tip deviation and angle deviation between 3 mm group and 5 mm group ( P>0.05), but deviations were significantly lower than those in free hand group ( P<0.05). Conclusions:The length of the sleeves has significant influence on the accuracy of the surgical guide. There was no significant difference in accuracy of the implant guide with 3 mm or 5 mm metal sleeves. The vitro study has some limitations and needs further systematic research.