QUANTIFICATION OF DENTAL MOVEMENTS IN ORTHODONTIC FOLLOW-UP : A NOVEL APPROACH BASED ON REGISTRATION OF 3D MODELS OF DENTAL CASTS
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Table 1 . Details of dental modifications between the two casts in the three analysed patients , and comparison of correspondent RMS values with the control group .
Patient 1
First cast Second cast RMS value
malposition of 3 teeth distal rotation of central incisors removal of two teeth adjustment of malposition realignment of central incisors
Average pointto-point distance
1.61 mm 1.07 mm
Patient 2 malposition of a tooth adjustment of malposition 1.13 mm 0.24 mm Patient 3
Control group distal rotation of central incisors right canine in eruption correction of central incisors right canine erupted
- -
0.98 mm 0.26 mm
0.26 mm ( SD : 0.06 mm )
0.02 mm
Figure 6 . Second patient : on the left , the 3D model from the first cast , showing a malposition of the left canine ; on the right , the 3D model from the second cast , after orthodontic therapy . Figure 7 . Second patient . Chromatic map of modifications of dental surfaces between the two casts : blue areas are more vestibularized in the second cast , vice versa for the red and yellow areas . Green areas remained unchanged .
t test ( p < 0.01 ). In addition the technical error of measurement ( TEM ) was evaluated .
3 . Results In the group of control subjects , on average the RMS value was 0.26 mm ( SD : 0.06 ). No statistically significant differences were observed between measurements taken by the same operator or different observers ( p > 0.01 ).
The technical error of measurement ( TEM ) was respectively 6.1 % for intra-observer error and 9.6 % for inter-observer error . The first analysed patient was a female aged 12 years . She had a malposition involving both the canines and the second premolar on the right side . The orthodontic treatment was based on the removal of the second premolar on the right side and the first on the left side and the application of an orthodontic device , as shown by the second cast performed after one year ( Fig . 4 ). The registration and calculation of point-to-point distances between the two models highlights the mesial rotation of the lateral incisors and realignment of the canine , whereas the molars did not show any appreciable modification ( Fig . 5 ). In addition the method was able to verify the novel orientation of the second premolar ; mean RMS value between the dental profiles from the two 3D scans amounted up to 1.61 mm . The second patient , a female aged 11 years , showed a malposition of the left canine : the application of an orthodontic device was able to produce an adjustment of the canine position , as shown by the second cast taken after four years ( Fig . 6 ). The procedures of registration were able to verify the vestibular translation of all dental elements ,
58 Stoma Edu J . 2017 ; 4 ( 1 ): 55-61 . http :// www . stomaeduj . com