Research On The Comparison Of Incisor Crown Root Length Between Patients With Open Bite And Deep Over Bite

Objective: The determination of tooth crown length,root length and crown-to-root ratio is of great significance to the treatment,risk prediction and prognosis of oral clinical disease and its' s an important reference index for oral anatomy,dental disease treatment,prosthodontic treatment,orthodontic treatment,periodontal disease and tooth implantation technology.Most of the previous studies on the crown root length were dependent on the panoramic radiograph,periapical film,the model,or the cephalometric analysis.However,these methods had serious drawbacks in the measurement of the tooth root crown length,and could not rule out the overlapping interference of vertical or sagittal dimension and limited the accuracy of the measurement.In recent years,CBCT has been increasingly popular because of its low radiation dose,high spatial resolution,good three-dimensional images of hard tissue structure and other advantages,which can clearly and accurately show the tooth root morphology.The study aims to use CBCT technique to measure the crown and root length of the maxillary and mandibular incisors of people with open bite and deep bite,and to calculate the crown-to-root ratio,providing reference for the clinical treatment and evaluation.Methods: 31 patients with open bite,30 patients with deep bite,30 patients with normal bite(control group)aged 15 to 35 were selected from Orthodontic Department,Hebei Medical University Stomatological Hospital from July,2012 to March,2017.They were shot CBCT before treatment.CBCT images of three groups patients were reconstructed,fixed and aligned with InVivo 5.0 software.The crown length,root length and crown-to-root ratio of maxillary central incisors,maxillary lateral incisors and mandibular incisors were measured.Statistical analysis was performed on the three groups of data.SPSS21.0 software was used to express the obtained measurementdata as mean ± standard deviation.The one-way analysis of variance was adopted to compare different groups.Bonferroni method was used to compare the data between the groups.P <0.05 was considered of statistical significance.Results:1 Crown length: The crown length of mandibular incisors of three groups was of statistical significance(P<0.05).The crown length of the open bite group was more than that of the control group and deep bite group.2 Root length: It increased in an order from the open bite group to the control group to the deep bite group.The root length of maxillary central incisors in the open bite group was less than that of the control group(P<0.05).The root length of the open bite group was less than that of the deep bite group(P<0.05).There was no significant difference between the root length of control group and the deep bite group(P>0.05).The root length of maxillary lateral incisors in the open bite group was less than that of the control group(P<0.05).The root length of the open bite group was less than that of the deep bite group(P<0.05).The root length of the control group was less than that of the deep bite group(P<0.05).The root length of mandibular incisors in the open bite group was less than that of the deep bite group(P<0.05).The root length of the control group was lower than that of the deep bite group(P<0.05).There was no significant difference between the root length of the open bite group and the control group(P>0.05).3 Crown-to-root ratio: It decreased in an order from the open bite group to the control group to the deep bite group.The crown-to-root ratio of maxillary central incisors in the open bite was higher than that of control group(P<0.05).The crown-to-root ratio of the open bite group was higher than that of the deep bite group(P<0.05).The crown-to-root ratio between the control group and the deep bite group was no statistical significance(P>0.05).The crown-to-root ratio of maxillary lateral incisors in the open bite was higher than that of control group(P<0.05).Thecrown-to-root ratio of the open bite group was higher than that of the deep bite group(P<0.05).The crown-to-root ratio between the control group and the deep bite group was no statistical significance(P>0.05).The mandibular incisors between three groups were of statistical significance(P<0.05).Conclusions: The study shows that the root length of patients with open bite is less than that of normal crowd,while the root length of the patients in the deep bite group is more than that that of normal crowd.The crown length of the mandibular incisors in the open bite is more than that that of normal crowd,while the crown length of the mandibular incisors in the deep overbite group is less than that of the normal crowd.It is of a certain reference for the oral clinical risk assessment and treatment.