| ObjectiveTo compare the anchorage requirements of straight wire appliance and Invisalign appliance in the treatment of tooth extraction patients at the stage of alignment using three-dimensional laser scanner technology.The purpose of research is to provide reference basis for clinical treatment.MethodsForty-four subjects(male 18,female 26,average age 22.58±2.42 years)with maxillary anterior protrusion who had four first premolars removed and met inclusion criteria were selected and randomly divided into two groups which were straight wire appliance and Invisalign appliance.Each group included 22 cases.Group 1 was straight wire(male 8,female 14,mean age 22.04±2.12)and group 2 was Invisalign(male 10,female 12,mean age 23.12±2.69).The straight wire technique and Invisalign technique were used to correct the qualified adult patients.Plaster cast models were taken before and after patients who were aligned.ITero scanner was applied to scan the plaster model and reconstruct the three-dimensional digital model.The three-dimensional digital models were created from a 3 Shape laser scanner(Copenhagen,Denmark).The three-dimensional model was overlapped to measure the changes in three-dimensional direction of maxillary central incisors,canine,second premolars,first molars,crown inclination,buccal and lingual torque and to compare and analyze the demand of anchorage for two kinds of correction techniques in the stage of leveling.The paired test was used to compare and analyze the changes of each measurement item before and after the internal alignment of each group,and the test of two independent samples was used to analyze the changes and differences between the two-groups.SPSS22.0 statistical analysis software was used for statistical analysis.Results1.For group 1,the measurement results of 3d model showed that the maxillary central incisors before and after aligned moved distally 1.75±1.32mm,the labial tipping 0.96±0.77mm,and crown lingual tipping 8.53±3.56°.The data above was statistically significant.The amount of elongation was 0.36±0.56mm.The maxillary cusp moved 1.94±1.87mm distally with buccally 0.98±1.32mm and distal tipping 4.57±0.22°.The data above was statistically significant.It was slight elongation of 0.33±0.72mm and labial tipping 2.33±1.46°.The mesial movement distance of the maxillary second premolars was 1.93±1.53mm with slight elongation,and the crown moved 0.80±0.44mm to the tongue with the crown mesial tipping 3.18±2.08° and lingual tipping 6.58±4.25°.The data was not statistically significant.The maxillary first molars moved mesially 1.68±1.33mm with crown lingual tipping 7.15±2.76°.The data above was statistically significant.It was slight elongation of 0.24±0.68mm,and the tongue moved 1.02±0.48mm with the crown mesial tipping 3.50±2.89°.2.Results of 3d model measurement showed that the distal movement of the maxillary central incisor was 1.24±1.68mm with a slight elongation of 0.22±0.69mm,a buccal movement of 0.14±0.07mm and lingual torque of 3.88±3.23°.The distal displacement of the maxillary cusp was 2.64±1.85mm and the tongue displacement was 1.29±0.40mm.The data above was statistically significant.The amount of elongation was 0.68±0.57mm,and the distal inclination of the crown was 0.07±0.12°with the crown tongue tipping 2.09±1.51°.The proximal midrange movement of the maxillary second premolars was 0.85±0.48mm,and the intrusive movement was 1.08±0.51mm with the crown labial tipping 6.27±3.81°.The data above was statistically significant.The buccal movement was 0.23±0.43mm with mesial tipping 1.70±2.51°.The maxillary first molars moved 0.70±0.45mm toward the mesial with intrusion of 1.07±0.62mm,and the data above was statistically significant.The buccal movement was 0.19±0.36mm with the crown mesial tipping 9.42±3.12° and crown labial tipping 3.47±2.89°.3.The measurement and analysis results of the three-dimensional model showed that the maxillary central incisors of the straight wire bow group and the Invisalign group inclined to the distal and lingual,while the crown tongue torque and distal movement of the Invisalign group were smaller than the straight wire bow group,and the difference between the two groups was statistically significant.The maxillary cusps in the two groups all moved distally with slight elongation and distal tipping,and the straight wire arch group was larger than the Invisalign group about the buccal tipping.The straight wire arch group was less than the Invisalign group about the distal movement and the elongation.The difference between the two groups was statistically significant.The maxillary cusps in the Invisalign group were lingual tipping,while the straight wire arch group moved labial tipping.Both groups of the maxillary second premolars moved toward mesial,but the mesial distance of the straight wire was greater than the invisalign group.However,the straight wire group was slightly elongated and inclined to the lingual,while the Invisalign group was slightly intrusion and inclined to the labial.The difference between group 1 and group 2 was statistically significant.The first maxillary molars in the two groups all had a mesial tipping movement,and the degree in the straight wire group was less than the Invisalign group.The mesial movement was greater than the Invisalign group.The first molars in the straight wire group were slightly elongated and inclined to lingual,while the Invisalign group was slightly intrusion with buccal tipping.The differences between the above two groups were statistically significant.Conclusion1.There are still some shortcomings in the control of anchorage in the two groups.The molars are mesial movement,while the maxillary central incisor and cusp are distal movement with slight elongation.2.In the stage of alignment and leveling,the straight wire appliance combining with the backward ligation of the fangs and the end bending reduce the labial inclination of the front teeth and improve the crowding and protrusion of the front teeth.However,there is still a partial loss of anterior teeth torque and anchorage in horizontal,vertical and transverse directions.3.In the Invisalign group,the torque of the anterior teeth is slightly stronger than the straight wire,but anchorage is still lost At the same time,the posterior teeth are slightly intruted and buccal movement.So Invisalign has an advantage in correcting patients with high Angle and mild arch narrowing. |
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