| Background:the proportion of teeth is related to facial coordination.If the width length ratio is large,the shape of the teeth will look square,and if the ratio is close to 1,then the teeth will look close to the square,more suitable for round faces.Conversely,if the width ratio is too small,then the tooth shape is more slender,more suitable for longer face crowd type.The width of the crown of the front teeth can be extended to determine whether the proportion of teeth is appropriate and whether or not it needs improvement.Crown to root ratio is the most direct index to describe the anatomic morphology of teeth,and has a great reference value of guiding the work of oral clinicians and treating dental diseases.The morphology of teeth varies from individuals and races,so the ratio of crown to root is important not only in oral medicine research,but also in the development of anatomy and anthropology.At present,there are few reports on the ratio of anterior to crown.X-ray examination(including CT)has greatly promoted the development of medicine,but the ionizing radiation may cause damage to the subjects,while CT is a radiological examination of ionizing radiation is relatively high,according to the 2000 International Radiation Protection Committee statistics show that CT examination in the world accounted for 5%of the radiological examination however,dose radiological examination accounted for 34%,In the United States and even as high as 67%,with the increasing number of the check,check the radiation dose is a medical radiation source can not be ignored.In accordance with the requirements of radiation protection optimization(ALARA),the absorbed dose of the subject should be reduced to minimize the damage to the subject in the examination.Since its introduction to 2003 at the North American radiation Conference(RSNA),the 64 tier MSCT has been widely used in clinical applications due to its wide Z axis coverage and extremely fast frame rotation speed.However,as each machine use minimal pitch to ensure the integrity of data acquisition,the radiation dose problem has attracted more and more attention.Objective:to measure mandibular anterior teeth in the MSCT and CBCT images respectively(the central and lateral incisors)buccal lingual sectional images on the crown length,root length,crown width,cortical thickness,comparative analysis of anatomic characteristics of anterior teeth,used to guide the dental surgery related;discuss the method of measuring on the mandibular anterior teeth the crown length,root length,crown sagittal diameter,cortical bone thickness of the CBCT 3D image,the evaluation of MSCT in Stomatology;through the comparison of image quality between different parameters of spiral CT,method of tooth spiral CT low dose scanning the feasible.Methods:1.Randomly selected from January 2017 to May 2017,a total of 39 patients undergoing CTA examination at the Zhongshan hospital hospital of Xiamen were aged from 36 to 66 years,with an average age of 55 years.The 39 patients were randomly assigned to twelve groups.scan using Germany SIEMENS 64 slice dual source MSCT for twelve different control parameters of scanning and reconstruction parameters were selected,no obvious defect of a total of 305 teeth teeth(154 teeth on the lower teeth,151 teeth),which was a total of 150,a total of 155 lateral incisors.The data onto twelve groups of teeth were measured,and the image quality of different parameters was compared.2.Randomly selected patients from Xiamen Stomatological Hospital from January 2016 to April 2016,aged 13 to 33 years,a total of 26 patients.There were 302 teeth with no obvious tooth defect,including 50 middles and middle incisors,50 upper incisors,48 upper teeth,52 lower central incisors,52 lower incisors and 50 lower canines.The transfer of the patient CBCT image data onto image reconstruction using CBCT with NNT software,to determine the tooth,sharp teeth,tooth long axis,labial enamel junction,and then measure the crown length,root length,crown diameter,sagittal root surrounding alveolar bone cortical thickness.The average value of crown length,crown length and crown diameter ratio of each sample were calculated after 3 measurements of each tooth.The average value,standard deviation,maximum value and minimum value of the crown length,the length of the root and the diameter of the crown of the maxillary anterior teeth was statistically analyzed.The difference between the two groups was analyzed by t test.Results:1 in three-dimensional image of MSCT measured in 120kV,60mAs,and normal bone density reconstruction group(control group)parameters,the left central incisor,lateral incisor crown length was 9.77mm,9.40mm,on the right side of the central and lateral incisors average crown length is 10.59mm,8.53mm;left and right lateral incisor root the average length was 11.89mm and 11.62mm,the left and right incisor root length average values were 12.38mm and 11.98mm,the left central incisor roots width averaged 6.31mm,lateral incisor was 6.08mm,on the right side of the central and lateral incisors root mean pressure thickness were 6.16mm and 5.86mm;in 120kV,30mAs,normal bone density reconstruction parameters under the condition of the left central incisor and lateral incisor crown mean values for 10.01mm and 9.26mm,incisors lateral incisors were 9.98mm and 8.66mm in the right side,the average length of anterior tooth from left to right respectively 11.98mm,12.30mm,11.54mm,12.84mm;in 120kV,60mAs,secondary bone density reconstruction group parameters,anterior teeth from left to right crown length average values were 9.26mm,9.86mm,9.61mm,8.73mm,from left to right,the average root length value were 11.98mm,12.43mm,12.06mm,12.91mm;the average crown width from left to right respectively 6.33mm,6.03mm,6.46mm,5.21mm.2.On the MSCT three bit reconstructed image obtained by different parameters,the variances between/in the same measurement indexes between groups were tested by homogeneity of variance,and the P values corresponding to each F value were all greater than 0.05.3 in the incisor group(8.68mm),the crown width(7.98mm),the second group of canine lateral incisor group(7.03mm);the minimum width of crown length for incisor group(11.97mm),followed by the canine group(11.84mm),Incisor 11.48mm,crown width/length ratio of 0.73.Maximum lateral incisor a minimum of 0.67 incisors,canines were 0.71.4.There was no significant difference in the ratio of crown to root between the upper teeth.The ratio of crown to root of maxillary central incisors is 0.69mm,and the ratio of crown to root of lateral incisors is 0.65mm.5.The average thickness of cortical bone at the root of CEJ in the lower lip of the maxillary incisor were 0,45mm at the root of 4mm,and 0.82mm at the tip of the mandible.The mean thickness of cortical bone at the root of CEJ in the mandibular incisor were 0.71mm at 4mm and 1.03mm at the tip of the mandible.6.There is no obvious difference between the results of MSCT and CBCT on the same index.Conclusion:1 anterior crown width to length ratio of 0.68-0.81 incisors,lateral incisor was 0.67-0.77,the ratio of incisor crown root length was 0.50-0.87,0.59-0.80 lateral incisors,there was no significant difference between the two,MSCT measurement of anterior teeth up and down between the results showed little difference tooth size.Depending on different MSCT parameters set does not affect the accuracy of crown length,root length,crown width measurements,suggesting that MSCT can guarantee the image quality of the premise to reduce the effective tube current,which will greatly reduce the radiation of the dental imaging,can realize MSCT in oral medicine of low dose scanning.2.There is no significant difference between the results of MSCT and CBCT on the same measurement.It explains that low dose spiral CT scanning image can satisfy the measurement of clinical and imaging diagnosis requires physicians,high image quality,radiation hazards can not only reduce the patients themselves,can be widely used in the field of orthodontic tooth and dental implant.3 maxillary incisor labial CEJ root 4mm cortical thickness is 0.33 0.56mm,the apical part was 0.73-0.91mm;mandibular incisor labial CEJ root 4mm cortical thickness averaged 0.64-0.78mm,apical part was 0.94-1.12mm.There are significant differences in different parts of the alveolar bone thickness of cortical bone,incisor and canine 4mm were less than apical parts(namely the above 0.05 P);the same level of measurement,which is smaller than the area of canine incisors,maxillary incisors 4mm the thinnest part of the bone cortex,suggesting that dental implant surgery should be in does not affect other conditions as far as possible near the crest of the ridge root.4.By low dose spiral CT scanning with different parameters like photo comparison,comparison and measurement of the quality of the data obtained from 140kV,60mAs,image quality of medium density bone algorithm reconstruction group is best,but in different images between image data measured shows no significant difference between the high KV group of spiral CT image quality is good,but check the tooth,by lowering the tube voltage,tube current,reducing the effective regulation of reconstruction parameters,increasing pitch,shielding sensitive parts and reduce the amount of radiation and does not affect the inspection results of the judgment,suggesting that MSCT can be widely used in low dose scanning teeth. |
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