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Original Article

Korean J Orthod 2021; 51(6): 375-386

Published online November 25, 2021 https://doi.org/10.4041/kjod.2021.51.6.375

Copyright © The Korean Association of Orthodontists.

Three-dimensional evaluation of the transfer accuracy of a bracket jig fabricated using computer-aided design and manufacturing to the anterior dentition: An in vitro study

Jae-Hyun Parka , Jin-Young Choia, Seong-Hun Kima , Su-Jung Kima, Kee-Joon Leeb, Gerald Nelsona

aDepartment of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea
bDepartment of Orthodontics, Institute of Craniofacial Deformity, Yonsei University College of Dentistry, Seoul, Korea

Correspondence to:Seong-Hun Kim.
Professor, Department of Orthodontics, Graduate School of Dentistry, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 02447, Korea.
Tel +82-2-958-9392 e-mail bravortho@gmail.com

Received: December 24, 2020; Revised: June 5, 2021; Accepted: June 7, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: To evaluate the accuracy of a one-piece bracket jig system fabricated using computer-aided design and manufacturing (CAD/CAM) by employing three-dimensional (3D) digital superimposition. Methods: This in vitro study included 226 anterior teeth selected from 20 patients undergoing orthodontic treatment. Bracket position errors from each of the 40 arches were analyzed quantitatively via 3D digital superimposition (best-fit algorithm) of the virtual bracket and actual bracket after indirect bonding, after accounting for possible variables that may affect accuracy, such as crowding and presence of the resin base. Results: The device could transfer the bracket accurately to the desired position of the patient’s dentition within a clinically acceptable range of ± 0.05 mm and 2.0° for linear and angular measurements, respectively. The average linear measurements ranged from 0.029 to 0.101 mm. Among the angular measurements, rotation values showed the least deviation and ranged from 0.396° to 0.623°. Directional bias was pronounced in the vertical direction, and many brackets were bonded toward the occlusal surface. However, no statistical difference was found for the three angular measurement values (torque, angulation, and rotation) in any of the groups classified according to crowding. When the teeth were moderately crowded, the mesio-distal, bucco-lingual, and rotation measurement values were affected by the presence of the resin base. Conclusions: The characteristics of the CAD/CAM one-piece jig system were demonstrated according to the influencing factors, and the transfer accuracy was verified to be within a clinically acceptable level for the indirect bracket bonding of anterior teeth.

Keywords: 3D scanner, Bracket, Bonding, Digital model

Article

Original Article

Korean J Orthod 2021; 51(6): 375-386

Published online November 25, 2021 https://doi.org/10.4041/kjod.2021.51.6.375

Copyright © The Korean Association of Orthodontists.

Three-dimensional evaluation of the transfer accuracy of a bracket jig fabricated using computer-aided design and manufacturing to the anterior dentition: An in vitro study

Jae-Hyun Parka , Jin-Young Choia, Seong-Hun Kima , Su-Jung Kima, Kee-Joon Leeb, Gerald Nelsona

aDepartment of Orthodontics, Graduate School of Dentistry, Kyung Hee University, Seoul, Korea
bDepartment of Orthodontics, Institute of Craniofacial Deformity, Yonsei University College of Dentistry, Seoul, Korea

Correspondence to:Seong-Hun Kim.
Professor, Department of Orthodontics, Graduate School of Dentistry, Kyung Hee University, 26 Kyungheedae-ro, Dongdaemun-gu, Seoul 02447, Korea.
Tel +82-2-958-9392 e-mail bravortho@gmail.com

Received: December 24, 2020; Revised: June 5, 2021; Accepted: June 7, 2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective: To evaluate the accuracy of a one-piece bracket jig system fabricated using computer-aided design and manufacturing (CAD/CAM) by employing three-dimensional (3D) digital superimposition. Methods: This in vitro study included 226 anterior teeth selected from 20 patients undergoing orthodontic treatment. Bracket position errors from each of the 40 arches were analyzed quantitatively via 3D digital superimposition (best-fit algorithm) of the virtual bracket and actual bracket after indirect bonding, after accounting for possible variables that may affect accuracy, such as crowding and presence of the resin base. Results: The device could transfer the bracket accurately to the desired position of the patient’s dentition within a clinically acceptable range of ± 0.05 mm and 2.0° for linear and angular measurements, respectively. The average linear measurements ranged from 0.029 to 0.101 mm. Among the angular measurements, rotation values showed the least deviation and ranged from 0.396° to 0.623°. Directional bias was pronounced in the vertical direction, and many brackets were bonded toward the occlusal surface. However, no statistical difference was found for the three angular measurement values (torque, angulation, and rotation) in any of the groups classified according to crowding. When the teeth were moderately crowded, the mesio-distal, bucco-lingual, and rotation measurement values were affected by the presence of the resin base. Conclusions: The characteristics of the CAD/CAM one-piece jig system were demonstrated according to the influencing factors, and the transfer accuracy was verified to be within a clinically acceptable level for the indirect bracket bonding of anterior teeth.

Keywords: 3D scanner, Bracket, Bonding, Digital model

Fig 1.

Figure 1.One-piece transfer jig system fabricated using computer-aided design and manufacturing for indirect bonding. A, Virtual one-piece jig with bracket. B, Ceramic bracket adapted to the three-dimensional-printed one-piece jig.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 2.

Figure 2.Schematic illustrating the research design.
CAD/CAM, computer-aided design and manufacturing; RP, rapid prototyping; 3D, three-dimensional.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 3.

Figure 3.Progress of digital indirect bonding and transfer accuracy evaluation in cases of mild crowding (A–C) and moderate crowding (D–F). A, D, Virtual brackets are positioned precisely on each individual tooth surface through virtual setups with the software program (3Txer; Cenos Co., Anyang, Korea). B, E, The customized one-piece bracket transfer jigs are designed and fabricated using computer-aided design and manufacturing and bonded to the rapid prototyping model. C, F, Three-dimensional digital superimposition of the virtual model.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 4.

Figure 4.A, Three-dimensional (3D) digital superimposition (best-fit method) of the virtual model (yellow color) and post-transfer model (green color) by using RapidForm software 2006 (INUS Technology, Seoul, Korea). B, The 3D coordinate system of the superimposed bracket. The origin of the coordinate system is set to coincide with the center point of the bracket base.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 5.

Figure 5.Histogram of frequencies for the six measurements generated using the one-tailed equivalence test for brackets with a customized resin base (group A). (A–C) linear and (D–F) angular measurements. Numbers on the horizontal axis indicate the differences between the virtual and actual models, and the height of each bar indicates the frequency of each difference range. The vertical line of the graph (0.5 mm in A–C, and 2.0° in D–F) shows the American Board of Orthodontics Objective Grading System (ABO OGS) criterion. Almost all linear and angular measurements are within the ABO OGS criterion. The p-value is calculated using the one-tailed equivalence test.
M-D, mesio-distal; B-L, bucco-lingual; O-G, occluso-gingival; T, torque; A, angulation; R, rotation; SD, standard deviation.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 6.

Figure 6.Histogram of frequencies for the six measurements generated using the one-tailed equivalence test for brackets without a customized resin base (group B). (A–C) linear and (D–F) angular measurements. Numbers on the horizontal axis indicate the differences between the virtual and actual models, and the height of each bar indicates the frequency of each difference range. The vertical line of the graph (0.5 mm in A–C, and 2.0° in D–F) shows the American Board of Orthodontics Objective Grading System (ABO OGS) criterion. Almost all linear and angular measurements are within the ABO OGS criterion. The p-value is calculated using the one-tailed equivalence test.
M-D, mesio-distal; B-L, bucco-lingual; O-G, occluso-gingival; T, torque; A, angulation; R, rotation; SD, standard deviation.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Fig 7.

Figure 7.Percentages of frequencies of directional bias for the six measurements in group A (A) and group B (B).
BCT, buccal crown torque; LCT, lingual crown torque; MRT, mesial root tip; DRT, distal root tip; m-b, mesio-buccal; m-l, mesio-lingual; M-D, mesio-distal; B-L, bucco-lingual; O-G, occluso-gingival.
Korean Journal of Orthodontics 2021; 51: 375-386https://doi.org/10.4041/kjod.2021.51.6.375

Table 1 . Difference between the reference position and actual bracket placement after indirect bonding in each experimental group.

GroupArch (n)Mesio-distal (mm)Bucco-lingual (mm)Occluso-gingival (mm)Torque (°)Angulation (°)Rotation (°)
Mean ± SDp-valueMean ± SDp-valueMean ± SDp-valueMean ± SDp-valueMean ± SDp-valueMean ± SDp-value
AUpper (116)−0.004 ± 0.0480.3250.010 ± 0.0510.027*−0.071 ± 0.095< 0.001***0.151 ± 0.6800.019*−0.139 ± 0.6910.032*−0.029 ± 0.4580.487
Lower (109)0.005 ± 0.0480.250−0.009 ± 0.0520.084−0.097 ± 0.096< 0.001***0.168 ± 0.6510.008**−0.095 ± 0.6490.129−0.001 ± 0.5400.989
BUpper (116)0.012 ± 0.029< 0.001***0.008 ± 0.0520.079−0.075 ± 0.056< 0.001***−0.004 ± 0.6270.9330.014 ± 0.7540.840−0.007 ± 0.4670.869
Lower (109)0.012 ± 0.0380.001**0.002 ± 0.0640.722−0.119 ± 0.087< 0.001***0.195 ± 0.6770.003**−0.091 ± 0.7810.224−0.016 ± 0.5980.768

Group A, placement of brackets with a customized resin base; Group B, placement of brackets without a customized resin base; Mean, mean value of difference; SD, standard deviation; n, the number of brackets used for analysis..

The p-value is calculated using the one-sample t-test; *p < 0.05, **p < 0.01, ***p < 0.001..


Table 2 . Linear and angular differences according to Little’s irregularity index for each experimental group.

VariableGroup AGroup B
Linear measurement
Mesio-distal (mm)
Type 1−0.022 ± 0.0680.012 ± 0.020
Type 20.016 ± 0.0160.018 ± 0.044
Type 30.005 ± 0.0280.006 ± 0.031
p-value< 0.001***0.090
Bucco-lingual (mm)
Type 10.006 ± 0.0600.018 ± 0.049
Type 20.004 ± 0.050−0.018 ± 0.069
Type 3−0.006 ± 0.0480.020 ± 0.044
p-value0.316< 0.001***
Occluso-gingival (mm)
Type 1−0.117 ± 0.116−0.125 ± 0.070
Type 2−0.064 ± 0.073−0.082 ± 0.089
Type 3−0.074 ± 0.090−0.081 ± 0.052
p-value0.002**0.001**
Angular measurement
Torque (°)
Type 10.167 ± 0.7050.143 ± 0.585
Type 20.144 ± 0.643−0.018 ± 0.704
Type 30.170 ± 0.6580.166 ± 0.670
p-value0.9610.187
Angulation (°)
Type 1−0.164 ± 0.7680.034 ± 0.780
Type 2−0.095 ± 0.6110.003 ± 0.783
Type 3−0.105 ± 0.628−0.165 ± 0.728
p-value0.7320.254
Rotation (°)
Type 10.028 ± 0.543−0.049 ± 0.491
Type 2−0.008 ± 0.471−0.006 ± 0.637
Type 3−0.075 ± 0.4820.023 ± 0.441
p-value0.4280.706

Values are presented as mean ± standard deviation..

The one-way analysis of variance test is performed..

Group A, placement of brackets with a customized resin base; Group B, placement of brackets without a customized resin base; Type 1, mild crowding; Type 2, moderate crowding; Type 3, severe crowding..

The p-value is calculated using one-sample t-test; **p < 0.01, ***p < 0.001..


Table 3 . Mutual comparison between mild, moderate, and severe crowding according to Little’s irregularity index (group A and B).

VariableLittle’s index (n)
Type 1 (76)Type 2 (81)
Type 2 (81)Type 3 (68)Type 3 (68)
Group A
Mesio-distal (mm)
∆ ± SD−0.038 ± 0.007−0.024 ± 0.0070.011 ± 0.007
p-value< 0.001***0.002**0.389
Bucco-lingual (mm)
∆ ± SD0.002 ± 0.0080.012 ± 0.0080.010 ± 0.008
p-value> 0.9990.4380.758
Occluso-gingival (mm)
∆ ± SD−0.052 ± 0.015−0.040 ± 0.0150.009 ± 0.015
p-value0.002**0.021*> 0.999
Torque (°)
∆ ± SD0.022 ± 0.107−0.001 ± 0.111−0.025 ± 0.109
p-value> 0.999> 0.999> 0.999
Angulation (°)
∆ ± SD−0.068 ± 0.107−0.069 ± 0.1120.009 ± 0.110
p-value> 0.999> 0.999> 0.999
Rotation (°)
∆ ± SD0.036 ± 0.0800.108 ± 0.0830.066 ± 0.082
p-value> 0.9990.728> 0.999
Group B
Mesio-distal (mm)
∆ ± SD−0.006 ± 0.0050.005 ± 0.0050.012 ± 0.005
p-value0.728> 0.9990.093
Bucco-lingual (mm)
∆ ± SD0.037 ± 0.009−0.004 ± 0.009−0.039 ± 0.009
p-value0.001**> 0.999< 0.001***
Occluso-gingival (mm)
∆ ± SD−0.043 ± 0.011−0.040 ± 0.012−0.001 ± 0.012
p-value0.001**0.004**> 0.999
Torque (°)
∆ ± SD0.161 ± 0.104−0.037 ± 0.109−0.184 ± 0.107
p-value0.373> 0.9990.266
Angulation (°)
∆ ± SD0.030 ± 0.1220.197 ± 0.1270.168 ± 0.126
p-value> 0.9990.3700.545
Rotation (°)
∆ ± SD−0.043 ± 0.085−0.073 ± 0.089−0.029 ± 0.088
p-value> 0.999> 0.999> 0.999

Types 1, 2, and 3 represent mild, moderate, and severe crowding according to Little’s irregularity index, respectively. n is the number of brackets used for analysis..

Group A, placement of brackets with a customized resin base; Group B, placement of brackets without a customized resin base; ∆, mean difference; SD, standard deviation..

The p-value is calculated using Bonferroni’s post hoc test; *p < 0.05, **p < 0.01, ***p < 0.001..


Table 4 . Intergroup comparison according to the presence or absence of a resin base.

Little’s indexMesiodistal (mm)Buccolingual (mm)Occlusogingival (mm)Torque (°)Angulation (°)Rotation (°)
Group
A
Group
B
p-valueGroup
A
Group
B
p-valueGroup
A
Group
B
p-valueGroup
A
Group
B
p-valueGroup
A
Group
B
p-valueGroup
A
Group
B
p-value
Type 1 (76)0.018
± 0.014
0.043
± 0.056
< 0.001***0.047
± 0.038
0.043
± 0.028
0.5200.137
± 0.091
0.127
± 0.066
0.4290.636
± 0.340
0.542
± 0.255
0.0560.662
± 0.405
0.644
± 0.435
0.7880.437
± 0.318
0.433
± 0.230
0.925
Type 2 (81)0.023
± 0.024
0.041
± 0.025
< 0.001***0.038
± 0.032
0.052
± 0.049
0.043*0.077
± 0.059
0.090
± 0.080
0.2270.571
± 0.323
0.602
± 0.359
0.5650.502
± 0.357
0.628
± 0.462
0.0540.382
± 0.272
0.515
± 0.370
0.010*
Type 3 (68)0.019
± 0.018
0.023
± 0.018
0.2100.036
± 0.033
0.038
± 0.030
0.4800.094
± 0.062
0.097
± 0.042
0.3960.592
± 0.217
0.587
± 0.359
0.7670.549
± 0.337
0.555
± 0.439
0.2450.377
± 0.328
0.342
± 0.235
0.608

Values are presented as mean ± standard deviation..

Types 1, 2, and 3 represent mild, moderate, and severe crowding according to Little’s irregularity index, respectively. n is the number of brackets used for analysis..

Group A, placement of brackets with a customized resin base; Group B, placement of brackets without a customized resin base..

The p-value is calculated using the independent t-test; *p < 0.05, ***p < 0.001..