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The effect of third molars on maxillary molar distalisation using a miniscrew-supported 3D® maxillary bimetric distalising arch

Australasian Orthodontic Journal
Volume 38 (2022): Issue 2 (July 2022)
By:
Open Access
|Sep 2022

Figures & Tables

Figure 1.

(A) Miniscrew insertion between first and second premolars (note proximity of the miniscrew to the second premolar root). (B) 3D® Maxillary Bimetric Distalizing Arch, 5-mm open Elgiloy coil-springs placed distal to the omega-loops, and molar bands with gingivally-placed headgear tubes (0.045-inch). (C) Activation of the open coil-springs with elastomeric chains. (D) Intraoral positioning of the 3D® Maxillary Bimetric Distalizing Arch from occlusal view.
(A) Miniscrew insertion between first and second premolars (note proximity of the miniscrew to the second premolar root). (B) 3D® Maxillary Bimetric Distalizing Arch, 5-mm open Elgiloy coil-springs placed distal to the omega-loops, and molar bands with gingivally-placed headgear tubes (0.045-inch). (C) Activation of the open coil-springs with elastomeric chains. (D) Intraoral positioning of the 3D® Maxillary Bimetric Distalizing Arch from occlusal view.

Figure 2.

Reference planes and cephalometric variables used in the study. Reference planes: SN (Sella–Nasion) plane; Occlusal plane, passing through mesiobuccal cusp tip of maxillary first molar and incisal edge of maxillary central incisor; GoGn (Gonion-Gnathion) plane; Horizontal reference plane (HRP), horizontal plane angulated 7° clockwise to the SN plane at Sella; Vertical reference plane (VRP), perpendicular plane to the HRP passing through Sella. Cephalometric variables: 1, SNA; 2, SNB; 3, ANB; 4, GoGn.SN; 5, Occ plane.SN; 6, Overjet; 7, Overbite; 8, U6root-VRP (perpendicular distance between mesiobuccal root apex of maxillary first molar and VRP); 9, U6trifurc.-VRP (perpendicular distance between trifurcation point of maxillary first molar roots and VRP); 10, U6M-VRP (perpendicular distance between mesial contact point of maxillary first molar crown and VRP); 11, U6 MB-HRP (perpendicular distance between mesiobuccal cusp tip of maxillary first molar and HRP); 12, U5.HRP; 13, U6.HRP; 14, U7.HRP; 15, U1i-VRP; 16, U1.HRP; 17, L1.HRP.
Reference planes and cephalometric variables used in the study. Reference planes: SN (Sella–Nasion) plane; Occlusal plane, passing through mesiobuccal cusp tip of maxillary first molar and incisal edge of maxillary central incisor; GoGn (Gonion-Gnathion) plane; Horizontal reference plane (HRP), horizontal plane angulated 7° clockwise to the SN plane at Sella; Vertical reference plane (VRP), perpendicular plane to the HRP passing through Sella. Cephalometric variables: 1, SNA; 2, SNB; 3, ANB; 4, GoGn.SN; 5, Occ plane.SN; 6, Overjet; 7, Overbite; 8, U6root-VRP (perpendicular distance between mesiobuccal root apex of maxillary first molar and VRP); 9, U6trifurc.-VRP (perpendicular distance between trifurcation point of maxillary first molar roots and VRP); 10, U6M-VRP (perpendicular distance between mesial contact point of maxillary first molar crown and VRP); 11, U6 MB-HRP (perpendicular distance between mesiobuccal cusp tip of maxillary first molar and HRP); 12, U5.HRP; 13, U6.HRP; 14, U7.HRP; 15, U1i-VRP; 16, U1.HRP; 17, L1.HRP.

Figure 3.

Reference planes and variables used in model analysis. Reference planes: Midpalatal raphe, the depression of the midpalatal suture; Rugae line, a perpendicular line to the midpalatal raphe passing through the same rugal points identifiable on both (T0&T1) dental casts. Dental cast variables: 1, U5-rugae line (distance between the central fossa of the second premolar and rugae line); 2, U6-rugae line (distance between the central fossa of the first molar and rugae line); 3, U7-rugae line (distance between the central fossa of the second molar and rugae line); 4, U5-U5 (inter-second premolar width); 5, U6-U6 (inter-first molar width); 6, U7-U7 (inter-second molar width); 7, U5.U5 (angle formed between the mesiodistal axes of the second premolars); 8, U6.U6 (angle formed between the mesiodistal axes of the first molars); 9, U7.U7 (angle formed between the mesiodistal axes of the second molars).
Reference planes and variables used in model analysis. Reference planes: Midpalatal raphe, the depression of the midpalatal suture; Rugae line, a perpendicular line to the midpalatal raphe passing through the same rugal points identifiable on both (T0&T1) dental casts. Dental cast variables: 1, U5-rugae line (distance between the central fossa of the second premolar and rugae line); 2, U6-rugae line (distance between the central fossa of the first molar and rugae line); 3, U7-rugae line (distance between the central fossa of the second molar and rugae line); 4, U5-U5 (inter-second premolar width); 5, U6-U6 (inter-first molar width); 6, U7-U7 (inter-second molar width); 7, U5.U5 (angle formed between the mesiodistal axes of the second premolars); 8, U6.U6 (angle formed between the mesiodistal axes of the first molars); 9, U7.U7 (angle formed between the mesiodistal axes of the second molars).

Figure 4.

Comparison of first molar movements between groups. Colored arrows represent the following; red, U6.HRP (amount and direction of tipping); purple, U6root-VRP (amount of root distalization at apex level); turquoise, U6trifurc.-VRP (amount of root distalization at trifurcation level); orange, U6M-VRP (amount of crown distalization at mesial contact point); blue, U6MB-HRP (amount of intrusion at mesiobuccal cusp tip).
Comparison of first molar movements between groups. Colored arrows represent the following; red, U6.HRP (amount and direction of tipping); purple, U6root-VRP (amount of root distalization at apex level); turquoise, U6trifurc.-VRP (amount of root distalization at trifurcation level); orange, U6M-VRP (amount of crown distalization at mesial contact point); blue, U6MB-HRP (amount of intrusion at mesiobuccal cusp tip).

Demographic characteristics of patients in the treatment groups_

Group 1 (Third molars extracted) (n= 11)Group 2 (Third molars present) (n= 12)
Mean (min-max) or nSDMean (min-max) or nSDp
Age (years)15.72.815.71.70.567
(13.4-21.2) (13.7-18.9)
Sex
    Female9 10 0.876
    Male2 2
Anteroposterior discrepancy
    1 / 4-cusp0 0 0.789
    1 /2-cusp6 7
    3/4-cusp2 3
    full-cusp3 2

Comparison of cephalometric and model measurements at the beginning of distalization (T0) and changes achieved with distalization (T1-T0)_

Group 1 (Third molars extracted)Group 2 (Third molars present)
T0ChangesT0ChangesBetween groups
Mean ± SDMean ± SDpMean ± SDMean ± SDpComparison at T0 pComparison of changes p
Skeletal
    SNA (°)80.7 ± 2.6-1.1 ± 2.30.21481.8 ± 2.9-1.3 ± 2.80.2920.3910.066
    SNB (°)74.9 ± 2.61.1 ± 1.50.39675.8 ± 3.40.9 ± 1.50.7210.3690.437
    ANB (°)5.8 ± 1.9-0.5 ± 1.60.6786 ± 30.9 ± 1.50.3570.8060.413
    GoGn . SN (°)30.1 ± 4.1-1.2 ± 1.50.67833.3 ± 6.7-0.8 ± 1.20.5410.3070.967
Dental - Model
    U5 - rugae line (mm)6.1 ± 2.93.2 ± 2.10.008*8.2 ± 2.73.6 ± 1.90.005*0.1420.514
    U6 - rugae line (mm)15.3 ± 34.5 ± 1.80.008*17.3 ± 2.63.9 ± 1.70.005*0.1020.191
    U7 - rugae line (mm)25.7 ± 3.34.8 ± 1.90.008*28.3 ± 2.53.6 ± 2.30.005*0.041*0.027*
    U5 - U5 (mm)43.1 ± 3.61.8 ± 2.10.008*43.9 ± 4.32.1 ± 3.90.005*0.2880.514
    U6 - U6 (mm)41.8 ± 4.1-0.2 ± 1.60.85942.8 ± 2.70.6 ± 1.60.3330.3270.369
    U7 - U7 (mm)47.2 ± 3.11.9 ± 3.70.008*48.6 ± 3.67.2 ± 4.90.005*0.3690014*.
    U5 . U5 (°)137.9 ± 11.410.5 ± 60.008*135.8 ± 10.36.7 ± 6.90.032*0.9350.051
    U6 . U6 (°)119 ± 9.3-2.5 ± 7.50.314121.9 ± 10-2.7 ± 5.10.1690.4620.838
    U7 . U7 (°)120 ± 6.43.7 ± 4.70.028*119.6 ± 11.9-6.2 ± 8.70.2410.9350.027*
Dental - Cephalometric
    U6M - VRP (mm)41.2 ± 4.1-3.9 ± 2.30.008*39.3 ± 3-3.4 ± 2.40. 007*0.4140.178
    U6trifurc. - VRP (mm)37.6 ± 3.8-4.5 ± 5.60.008*36 ± 3.3-3.5 ± 3.20.005*0.5140.022*
    U6root - VRP (mm)40.3 ± 3.7-5.5 ± 4.30.008*38.7 ± 3.7-3.8 ± 5.40.005*0.6240. 003*
    U5 . HRP (°)96.2 ± 3.67.6 ± 3.70.008*96.8 ± 4.88.6 ± 3.10. 005*0.9020.683
    U6 . HRP (°)98 ± 3.5-7.7 ± 3.20.008*100.9 ± 3.6-3.9 ± 2.70.005*0.0.1020.001*
    U7 . HRP (°)108.4 ± 7.7-4.1 ± 4.60.011*113 ± 4.6-1.1 ± 2.20.1390.1420. 027*
    U6 MB - HRP (mm)64.2 ± 5.3-1.9 ± 1.10.008*59.9 ± 3.8-1.1 ± 0.90.008*0.0790.005*
    Occ Plane . SN (°)18.3 ± 54.9 ± 3.70.008*16.9 ± 4.22.2 ± 3.20.007*0.4620.001*
    U1i - VRP (mm)66.2 ± 7.8-1.2 ± 1.60.008*65.5 ± 4.6-0.5 ± 2.70.038*0.7750.066
    U1 . HRP (°)108.9 ± 11-2.1 ± 2.80.028*108.5 ± 8.2-3 ± 2.20.005*0.5680.221
    L1 . HRP (°)62.7 ± 5.80.9 ± 1.20.57964.1 ± 4.30.7 ± 0.90.6680.2290.765
    Overjet (mm)5.8 ± 2.8-1.4 ± 1.90.2615.2 ± 1.9-1.1 ± 1.90.5530.6240.178
    Overbite (mm)3.7 ± 1.7-0.9 ± 1.20.8593.2 ± 1.5-1.5 ± 1.90.0590.6240.102
DOI: https://doi.org/10.2478/aoj-2022-033 | Journal eISSN: 2207-7480 | Journal ISSN: 2207-7472
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Language: English
Page range: 319 - 328
Submitted on: May 1, 2022
Accepted on: Sep 1, 2022
Published on: Sep 29, 2022
Published by: Australian Society of Orthodontists Inc.
In partnership with: Paradigm Publishing Services
Publication frequency: 1 issue per year
Related subjects:
Medicine,
Basic medical science,
Basic medical science, other

© 2022 Nilüfer İrem Tunçer, Ayça Arman-Özçırpıcı, published by Australian Society of Orthodontists Inc.
This work is licensed under the Creative Commons Attribution 4.0 License.

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