Abstract: Objective: In this paper, we will report a case of maxillary permanent central incisor dislocation with lower lip contusion and laceration. Combined with the latest guidelines issued by the International Society for Dental Trauma in 2020, we will carry out standardized treatment for young patients with permanent tooth dislocation. Diagnosis and treatment: After debridement of the lower lip mucosa, the contusion and laceration of the lower lip mucosa was sutured under local anesthesia. Manual reduction of $\begin{array}{l|l}1 & 1 \\ \hline \end{array}$ dislocated teeth was carried out, then the neck of the anterior teeth and tear the gums were sutured. $\begin{array}{l|l}2 & 2 \\ \hline \end{array}$ had not yet sprouted, so $\begin{array}{l|l} Ⅴ\ Ⅳ\ Ⅲ\ 1& 1 \ Ⅲ\ Ⅳ\ Ⅴ\\ \hline \end{array}$ quartz fiber band fixation was performed. The occlusal relationship was examined after operation and the children and their families were advised to pay attention to the maintenance of oral hygiene. Results: Two weeks after operation, $\begin{array}{l|l}1 & 1 \\ \hline \end{array}$ crowns were intact, $1\rfloor$ was found with percussion pain (±), second degree loosening, $\lfloor 1 $ was found with percussion pain (–), second degree loosening. 8 weeks later, $\begin{array}{l|l}1 & 1 \\ \hline \end{array}$ were found withⅠ degree loosening, no discoloration of dental crown and good recovery of lower lip mucosa. At 6 months, 1 year and 2 years after operation, $\begin{array}{l|l}1 & 1 \\ \hline \end{array}$ were found with no pain, no loosening, no obvious change in crown color, normal pulp vitality test and good prognosis. Conclusions: For the cases of young permanent tooth dislocation, the standardized diagnosis and treatment with reference to the latest guidelines issued by the International Society for Dental Trauma is beneficial to the continued development of young permanent teeth. The standardized diagnosis and treatment of young permanent tooth dislocation can be used in oral emergency and outpatient service.

Key words: dental trauma, prolapsed dislocation, contusions, young permanent teeth, oral and maxillofacial surgery