Study On The Treatment Timing And Efficacy In The Vertically Impacted Maxillary Central Incisors

[Obejective]To investigate whether the treatment timing has influence on root development and periodontal attachment in the vertically impacted maxillary central incisors in the mixed dentition and analyse the treatment efficacy in the vertically impacted maxillary central incisors.[Methods]Twenty-four patients with vertically impacted maxillary central incisor who were admitted to the Department of Orthodontics,Stomatological Hospital affiliated to Nanjing Medical University from December 2012 to March 2018 were selected[13 males and 11 females,(9.3±0.6)years].Follow-up evaluation was performed on 17 cases after 1 year of treatment and 7 cases failed to continue.Based on the dental age,patients were classified as early treatment group(teeth ranging from a third to two thirds of root formation,n=13)and late treatment group(teeth with nearly or fully complete root formation,n=11).The contralateral maxillary central incisor was used as the control.Cone-beam CT reconstructed images of pre and post treatment and one year after treatment were obtained,and parameters of root and periodontal development of impacted and control teeth were also measured with Dolphin imaging 11.0 software.Mimics17.0 software was used to measure parameters of the root volume and root surface area at each evaluated juncture.The difference values(measurement values of impacted teeth were subtracted from control values)between the early and late treatment group of root and periodontal development parameters at the different time points(before,after,and one year after treatment)to explore the treatment timing in the vertically impacted maxillary central incisors in the mixed dentition.The difference values in root development before and after treatment for the impacted teeth and the control teeth,respectively,and those of the root and periodontal development parameters between the impacted teeth and the control teeth after treatment and one year after the treatment were compared to analyse the treatment efficacy in the vertically impacted maxillary central incisors.[Results]1.There were no significant differences in the difference values of root and periodontal development parameters at the three time points(P>0.05).Treatment timing had no effect on root development and alveolar bone height of vertically impacted maxillary central incisors in the mixed dentition.2.The difference values of root length between the impacted teeth and the control teeth in the early and late treatment group were(1.51±1.52)mm and(2.54±0.95)mm after the treatment and the values were significantly less than before treatment(3.45±1.34)and(3.27±0.80)mm(P<0.05).Orthodontic traction promoted the root development of impacted teeth.3.The root length of the impacted teeth were significantly shorter than those of the control teeth at these two time points(after treatment and one year after the treatment)(P<0.05).Regarding the root volume,there was no significant difference between these two groups(P>0.05).The root length of vertical impacted teeth could not reach the normal level after orthodontic treatment,while the volume could reach.In these two groups(early and late treatment group),the length of the clinical crown and the loss of labial alveolar bone height after the treatment and one year after the treatment of the impacted teeth were significantly larger than the corresponding indicators of the control teeth(P<0.05).The periodontal attachment of the impacted teeth after orthodontic treatment could not reach normal level.[Conclusions]The treatment timing had no effect on the root development and periodontal attachment of the vertical impacted maxillary central incisor in the mixed dentition.Orthodontic traction treatment could accelerate the root development of the impacted incisor.The root and periodontal attachment of the impacted teeth after treatment and one year after treatment still could not reach the normal level.