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Does the trimline extension and attachment size affect maxillary arch expansion in clear aligner therapy ? A finite element study

Nurver Karsli
Nurver Karsli
, 
Fazilet Yildirim
Fazilet Yildirim
, 
Arda Dingiloğlu
Arda Dingiloğlu
 and 
Ömür Polat Özsoy
Ömür Polat Özsoy
   | May 21, 2024
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Published Online: May 21, 2024
Page range: 121 - 133
Received: Feb 01, 2024
Accepted: Mar 01, 2024
DOI: https://doi.org/10.2478/aoj-2024-0014
© 2024 Nurver Karsli et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure. 1

Different components of the finite element model.
Different components of the finite element model.

Figure. 2

Mesh structure.
Mesh structure.

Figure. 3

Clear aligner deformation. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.
Clear aligner deformation. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.

Figure. 4

Total tooth displacement. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.
Total tooth displacement. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.

Figure. 5

Three-dimensional displacement tendency of the maxillary first and second molars in low and flat trimline aligner (LTLA) models. No attachment: (A) Displacement along the x-axis; (B) Displacement along the y-axis; (C) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (D) Displacement along the x-axis; (E) Displacement along the y-axis; (F) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (G) Displacement along the x-axis; (H) Displacement along the y-axis; (I) Displacement along the z-axis.
Three-dimensional displacement tendency of the maxillary first and second molars in low and flat trimline aligner (LTLA) models. No attachment: (A) Displacement along the x-axis; (B) Displacement along the y-axis; (C) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (D) Displacement along the x-axis; (E) Displacement along the y-axis; (F) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (G) Displacement along the x-axis; (H) Displacement along the y-axis; (I) Displacement along the z-axis.

Figure. 6

Three-dimensional displacement tendency of the maxillary first and second molars in high and flat trimline aligner (HTLA) models. No attachment: (A) Displacement along the x-axis; (B) Displacement along the y-axis; (C) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (D) Displacement along the x-axis; (E) Displacement along the y-axis; (F) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (G) Displacement along the x-axis; (H) Displacement along the y-axis; (I) Displacement along the z-axis.
Three-dimensional displacement tendency of the maxillary first and second molars in high and flat trimline aligner (HTLA) models. No attachment: (A) Displacement along the x-axis; (B) Displacement along the y-axis; (C) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (D) Displacement along the x-axis; (E) Displacement along the y-axis; (F) Displacement along the z-axis; 3 mm horizontal rectangular attachment: (G) Displacement along the x-axis; (H) Displacement along the y-axis; (I) Displacement along the z-axis.

Figure. 7

Stress distribution in periodontal ligament. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.
Stress distribution in periodontal ligament. (A) Low and flat trimline aligner, and no attachment; (B) Low and flat trimline aligner, and 3 mm horizontal rectangular attachment; (C) Low and flat trimline aligner, and 4 mm horizontal rectangular attachment; (D) High and flat trimline aligner, and no attachment; (E) High and flat trimline aligner, and 3 mm horizontal rectangular attachment; (F) High and flat trimline aligner, and 4 mm horizontal rectangular attachment.

Quantity of nodes and elements within each group

Models Model 1 Model 2 Model 3 Model 4 Model 5 Model 6
Nodes 477893 481455 482530 476430 477132 478566
Elements 1800007 1811720 1815508 1796580 1798170 1803712
 

Directional movements of maxillary first and second molar teeth in the X, Y, Z axes

Measurement points LTLA HTLA
X Y Z X Y Z
Maxillary First Molar
NA Crown DPC -0.42270 -0.02778 -0.05881 -0.41190 -0.02110 -0.05823
DBC -0.39710 -0.07859 0.09173 -0.38680 -0.07149 0.08710
MPC -0.38330 -0.01627 -0.07791 -0.37290 -0.00965 -0.07852
MBC -0.35940 -0.06824 0.07563 -0.34930 -0.06114 0.06965
Root PA 0.11290 0.04356 -0.09336 0.10840 0.04085 -0.09292
DBA 0.07082 -0.01224 0.07460 0.06668 -0.01277 0.06766
MBA 0.10520 -0.01138 0.08203 0.10130 -0.01266 0.07557
3HA Crown DPC -0.42020 -0.03068 -0.05902 -0.41120 -0.02404 -0.05926
DBC -0.39470 -0.08151 0.09027 -0,386 -0.07477 0.08579
MPC -0.38070 -0.01918 -0.07690 -0.37180 -0.01252 -0.07841
MBC -0.35670 -0.07121 0.07534 -0.34810 -0.06442 0.06950
Root PA 0.11060 0.04444 -0.09261 0.10740 0.04228 -0.09314
DBA 0.06857 -0.01199 0.07350 0.06574 -0.01223 0.06663
MBA 0.10310 -0.01116 0.08191 0.10070 -0.01216 0.07562
4HA Crown DPC -0.41860 -0.03122 -0.05910 -0.40600 -0.02346 -0.05866
DBC -0.39380 -0.07995 0.09021 -0.38100 -0.07342 0.08483
MPC -0.37950 -0.02004 -0.07719 -0.36710 -0.01211 -0.07775
MBC -0.35670 -0.06970 0.07430 -0.34380 -0.06302 0.06853
Root PA 0.11060 0.04270 -0.09291 0.10680 0.04144 -0.09225
DBA 0.06841 -0.01112 0.07192 0.06582 -0.01213 0.06583
MBA 0.10230 -0.01073 0.08162 0.10020 -0.01206 0.07456
Maxillary Second Molar
NA Crown DPC -0.37410 -0.03655 -0.01012 -0.36120 -0.03534 -0.01292
DBC -0.37080 -0.06763 0.15280 -0.35810 -0.06490 0.14410
MPC -0.36470 -0.02798 -0.04917 -0.35240 -0.02717 -0.05065
MBC -0.36800 -0.06248 0.12770 -0.35570 -0.06002 0.11970
Root PA 0.08220 0.03165 -0.10440 0.07848 0.02973 -0.10380
DBA 0.10000 0.01395 0.02268 0.09560 0.01288 0.01871
MBA 0.07726 0.00664 0.04126 0.07355 0.00592 0.03650
3HA Crown DPC -0.37260 -0.03812 -0.01106 -0.35920 -0.03518 -0.01297
DBC -0.36930 -0.06901 0.15120 -0.35620 -0.06395 0.14320
MPC -0.36330 -0.02969 -0.04928 -0.35080 -0.02728 -0.05048
MBC -0.36660 -0.06401 0.12690 -0.35430 -0.05927 0.11910
Root PA 0.08127 0.03206 -0.10460 0.07818 0.02935 -0.10340
DBA 0.09893 0.01454 0.02175 0.09526 0.01302 0.01853
MBA 0.07629 0.00712 0.04071 0.07300 0.00615 0.03625
4HA Crown DPC -0.36890 -0.03773 -0.01073 -0.35850 -0.03568 -0.01303
DBC -0.36570 -0.06783 0.15020 -0.35530 -0.06537 0.14280
MPC -0.36000 -0.02954 -0.04862 -0.34950 -0.02752 -0.05014
MBC -0.36340 -0.06301 0.12610 -0.35260 -0.06050 0.11900
Root PA 0.08102 0.03158 -0.10350 0.07767 0.03027 -0.10300
DBA 0.09858 0.01456 0.02183 0.09462 0.01331 0.01843
MBA 0.07587 0.00726 0.04061 0.07295 0.006310 0.03632

Material properties

Material Elastic modulus [MPa] Poisson ratio [v]
Trabecular bone28–30 1.37 × 103 0.30
Cortical bone28–30 1.37 × 104 0.26
Teeth28–30 1.96 × 104 0.30
PDL28–30 6.9 × 10-1 0.45
Attachments28–30 1.25 × 104 0.36
CA28,29 5.28 × 102 0.36

Maximum aligner deformation and location

Models Maximum deformation (mm) Maximum deformation location
LTLA-NA 0.4209 Occlusal surface of the second molar
LTLA-3HA 0.4207 Occlusal surface of the second molar
LTLA-4HA 0.4204 Occlusal surface of the second molar
HTLA-NA 0.4121 Occlusal surface of the second molar
HTLA-3HA 0.4119 Occlusal surface of the second molar
HTLA-4HA 0.4116 Occlusal surface of the second molar
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