The Germination Trajectory Of The Maxillary Permanent Canines And The Correlation Study Between It And Dental Crowding

(Part 1)Objective:To study the eruption process of the maxillary canines on panoramic radiograph,and describe the germination trajectory of the maxillary canines.Materials and Methods:measurements of 300 panoramic radiograph(comes from Stomatology Department,the Children’s Hospital,Zhejiang University School of Medicine,in 2015-2019,3-13 years old.),divide these panoramic radiograph into five groups,include early stage of milk teeth period,eruption stage of the first molar,the complete eruption of the first molar stage,eruption stage of lateral teeth,and the complete eruption of the maxillary canine,each stage include 60 panoramic radiograph.Each stage measure three items,include the angle of the maxillary permanent canines and midline(θ),relative position of the maxillary permanent canines cusp and adjacent teeth and the growth tage of the maxillary permanent canines.And discribing the maxillary permanent canines eruption trajectory in two dimention,explaining the eruption process of the maxillary permanent canines.Results:At the early stage of milk teeth period,the maxillary permanent canines turn to distal direction,the cusp locates distal to the deciduous canines and close to it,the dental germ grow between third and forth stage.At eruption stage of the first molar,the maxillary permanent canines turn to vertical direction,the cusp locates mesio to the deciduous canines and close to it,the dental germ grow between fifth and sixth stageAt the complete eruption of the first molar stage,the maxillary permanent canines turn to mesio direction,the cusp locates between the deciduous canines and deciduous lateral incisor(permanent lateral incisor),the dental germ grow between seventh and eighth stage.At eruption stage of lateral teeth,the maxillary permanent canines turn to distal direction,the cusp locates between the deciduous canines and permanent lateral incisor,the dental germ grow at eighth stage.At the complete eruption of the maxillary canine,the maxillary permanent canines turn to distal direction,erupt between the permanent lateral incisor and first premolars,the dental germ grow at ninth to tenth stage.Conclusions:This study accord with the present eruption theory of the permanent maxillary canines.The permanent maxillary canines turn the direction to mesio and move to the root of maxillary lateral incisor,then turn to the vertical direction,erupt into the dentition.But this study can’t get the panoramic radiograph of initial stage of the eruption of permanent maxillary canines,so further study should be take to know the eruption process of permanent maxillary canines(Part 2)Objective:The correlation study between the permanent maxillary canines location,including distance,angle and relative location),and dental crowding,size of the dental arch(the width and length),to provide reference for early predict the dental crowding on panoramic radiographs.Materials and Methods:Panoramic radiographs and plaster mold measurements of 36 children(male 20,mean age:8.6 years;female 16,mean age:7.8 years).The measurements include the distance between the midline and the cusp of canines,the distance between the occlusion plane and the cusp of canines,the growth stage of canines,the angle between the canines and midline,and the dental crowding,the length and width of the dental arch.The correlation test were performed between the items on panoramic radiographs and plaster mold with SPSS20.0.Results:Significant correlation were seen between the angle of the canines and midline and all the items on the plaster mold.And other items show no correlation between each other.Conclusions:Significant correlation were seen between the angle of the canines and midline and all the items on the plaster mold.We need to study further to explore whether the angle of permanent maxillary canines and midline on panoramic radiograph can predict the dental crowding,and the treatment.