An Experimental Study On The Influence Of Different Tooth Extraction Modes On Bolton Index Based On Digital Model

Objective:Compare the accuracy of digital model and traditional plaster model,and to analyze the effects of four premolar extraction modes on Bolton index and occlusal relationship,so as to establish a more ideal occlusal relationship,so as to provide reference for clinical practice.Methods:1.Experimental grouping and acquisition of measurement data between groups 30 cases were included in this study,the digital model established by intraoral scanning was used as the experimental group,and the gypsum model perfused by traditional silicone rubber impression was used as the control group.In the experimental group and the control group,the relevant landmarks were selected to measure the Bolton index(anterior tooth ratio,whole tooth ratio),intermolar width(6-6),intercanine width(3-3),and the distance from the midpoint of the incisor margin to the highest point of the labial gingival margin(hll,h21,hl31,h41).The digital model uses 3shapeOrthoAnalyzerTM software to record and measure the landmarks,and the plaster model uses an electronic Vernier caliper with an accuracy of 0.01mm to manually record the marked points and measure related indexes.The paired sample t-test was carried out on the related measurement data of the two groups by using SPSS 18.0 statistical software,and the test level ?=0.05was set.2.To detect the changes of Bolton index and occlusal relationship after virtual tooth extraction.The measurement marks related to the lateral cephalogram of each patient were recorded by cephalometric analysis Winceph8.0 software,and the data of SNA,SNB,ANB,FMA,IMPA and FMIA were measured according to the requirements.The digital models of 30 patients were imported into 3shapeOrthoA-nalyzerTM software,and each patient simulated four tooth extraction modes,and the anterior tooth target was located by Tweed analysis,on the basis of which digital tooth arrangement was carried out,and a total of 120 sets of data were obtained.Group ?(virtual extraction of 14,24,34,44 teeth),group?(virtual extraction of 15,25,35,45 teeth),group ?(virtual extraction of 14,24,35,45 teeth)and group?(virtual extraction of 15,25,34,44 teeth).The Bolton index(whole tooth ratio),anterior overlay and coverage of the digital model after tooth arrangement were measured,and the average and standard deviation of these indexes were obtained.The crown width of the first premolar and the second premolar of the upper and lower mandible and its ratio to the crown width of the upper and lower dentition(6-6)were measured.The differences of Bolton index(total tooth ratio),overbite and overlay of anterior teeth in four extraction modes were analyzed.The single factor analysis of variance and multiple comparison of the measurement results were carried out by using SPSS 18.0 statistical software,and the test level ?=0.05was set.Results:1.There was no significant difference in Bolton index,intermolar width(6-6),intercanine width(3-3)and distance from the midpoint of incisor margin to the highest point of labial gingival margin(h11,h21,hl31,h41)between the experimental group and the control group(P>0.05).2.The Bolton index(total tooth ratio)of the four tooth extraction modes from large to small is as follows:group?(89.76%1.40%),group ?(89.69%±1.42%),group?(88.94%±1.49%),group?(88.79%±1.58%).There was no significant difference in Bolton index(total tooth ratio)among the four extraction modes.Compared with the Bolton index(whole tooth ratio)before tooth extraction,the difference was statistically significant(P<0.05).3.The measured values of the four tooth extraction modes from large to small are group ?(2.42mm±0.34mm mm,covered by 0.73mm±0.35mm),group?(2.37mm±0.33mm,0.65mm±0.34 mm),group ?(2.31mm±0.30 mm,0.60mm±0.32 mm),group?(2.24mm±0.32 mm,0.59mm±0.34 mm).There was no significant difference in the measured values of anterior tooth covering and covering among the four groups(P>0.05).4.The width of maxillary first premolars is 7.8mm±0.41 mm,accounting for 7.63%±0.25%;the width of maxillary second premolars is 7.37mm±0.36 mm,;the proportion is 7.20%±0.20%;the width of mandibular first premolars is 7.73mm±0.46mm;the proportion is 8.31%±0.31%;the width of mandibular second premolars is 7.mm±0.48mm.Mm,accounts for 8.30%±0.33%.Conclusion:1.he digital model obtained by direct scanning in the whole dentition has the same accuracy and accuracy as the traditional plaster model.2.Different premolar extraction modes will affect the whole tooth ratio of Bolton index after extraction.3.Bolton index could achieve satisfactory occlusal relationship by using four extraction modes.4.The influence of the extraction mode of premolar on Bolton index can be used as one of the reference bases for the formulation of clinical treatment plans.5.Digital virtual tooth arrangement can be used as a method to predict the effect of orthodontic treatment.