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.
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.
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).
Table I.
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 n | SD | Mean (min-max) or n | SD | p | |
| Age (years) | 15.7 | 2.8 | 15.7 | 1.7 | 0.567 |
| (13.4-21.2) | (13.7-18.9) | ||||
| Sex | |||||
| Female | 9 | 10 | 0.876 | ||
| Male | 2 | 2 | |||
| Anteroposterior discrepancy | |||||
| 1 / 4-cusp | 0 | 0 | 0.789 | ||
| 1 /2-cusp | 6 | 7 | |||
| 3/4-cusp | 2 | 3 | |||
| full-cusp | 3 | 2 | |||
Table II.
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) | |||||||
|---|---|---|---|---|---|---|---|---|
| T0 | Changes | T0 | Changes | Between groups | ||||
| Mean ± SD | Mean ± SD | p | Mean ± SD | Mean ± SD | p | Comparison at T0 p | Comparison of changes p | |
| Skeletal | ||||||||
| SNA (°) | 80.7 ± 2.6 | -1.1 ± 2.3 | 0.214 | 81.8 ± 2.9 | -1.3 ± 2.8 | 0.292 | 0.391 | 0.066 |
| SNB (°) | 74.9 ± 2.6 | 1.1 ± 1.5 | 0.396 | 75.8 ± 3.4 | 0.9 ± 1.5 | 0.721 | 0.369 | 0.437 |
| ANB (°) | 5.8 ± 1.9 | -0.5 ± 1.6 | 0.678 | 6 ± 3 | 0.9 ± 1.5 | 0.357 | 0.806 | 0.413 |
| GoGn . SN (°) | 30.1 ± 4.1 | -1.2 ± 1.5 | 0.678 | 33.3 ± 6.7 | -0.8 ± 1.2 | 0.541 | 0.307 | 0.967 |
| Dental - Model | ||||||||
| U5 - rugae line (mm) | 6.1 ± 2.9 | 3.2 ± 2.1 | 0.008* | 8.2 ± 2.7 | 3.6 ± 1.9 | 0.005* | 0.142 | 0.514 |
| U6 - rugae line (mm) | 15.3 ± 3 | 4.5 ± 1.8 | 0.008* | 17.3 ± 2.6 | 3.9 ± 1.7 | 0.005* | 0.102 | 0.191 |
| U7 - rugae line (mm) | 25.7 ± 3.3 | 4.8 ± 1.9 | 0.008* | 28.3 ± 2.5 | 3.6 ± 2.3 | 0.005* | 0.041* | 0.027* |
| U5 - U5 (mm) | 43.1 ± 3.6 | 1.8 ± 2.1 | 0.008* | 43.9 ± 4.3 | 2.1 ± 3.9 | 0.005* | 0.288 | 0.514 |
| U6 - U6 (mm) | 41.8 ± 4.1 | -0.2 ± 1.6 | 0.859 | 42.8 ± 2.7 | 0.6 ± 1.6 | 0.333 | 0.327 | 0.369 |
| U7 - U7 (mm) | 47.2 ± 3.1 | 1.9 ± 3.7 | 0.008* | 48.6 ± 3.6 | 7.2 ± 4.9 | 0.005* | 0.369 | 0014*. |
| U5 . U5 (°) | 137.9 ± 11.4 | 10.5 ± 6 | 0.008* | 135.8 ± 10.3 | 6.7 ± 6.9 | 0.032* | 0.935 | 0.051 |
| U6 . U6 (°) | 119 ± 9.3 | -2.5 ± 7.5 | 0.314 | 121.9 ± 10 | -2.7 ± 5.1 | 0.169 | 0.462 | 0.838 |
| U7 . U7 (°) | 120 ± 6.4 | 3.7 ± 4.7 | 0.028* | 119.6 ± 11.9 | -6.2 ± 8.7 | 0.241 | 0.935 | 0.027* |
| Dental - Cephalometric | ||||||||
| U6M - VRP (mm) | 41.2 ± 4.1 | -3.9 ± 2.3 | 0.008* | 39.3 ± 3 | -3.4 ± 2.4 | 0. 007* | 0.414 | 0.178 |
| U6trifurc. - VRP (mm) | 37.6 ± 3.8 | -4.5 ± 5.6 | 0.008* | 36 ± 3.3 | -3.5 ± 3.2 | 0.005* | 0.514 | 0.022* |
| U6root - VRP (mm) | 40.3 ± 3.7 | -5.5 ± 4.3 | 0.008* | 38.7 ± 3.7 | -3.8 ± 5.4 | 0.005* | 0.624 | 0. 003* |
| U5 . HRP (°) | 96.2 ± 3.6 | 7.6 ± 3.7 | 0.008* | 96.8 ± 4.8 | 8.6 ± 3.1 | 0. 005* | 0.902 | 0.683 |
| U6 . HRP (°) | 98 ± 3.5 | -7.7 ± 3.2 | 0.008* | 100.9 ± 3.6 | -3.9 ± 2.7 | 0.005*0. | 0.102 | 0.001* |
| U7 . HRP (°) | 108.4 ± 7.7 | -4.1 ± 4.6 | 0.011* | 113 ± 4.6 | -1.1 ± 2.2 | 0.139 | 0.142 | 0. 027* |
| U6 MB - HRP (mm) | 64.2 ± 5.3 | -1.9 ± 1.1 | 0.008* | 59.9 ± 3.8 | -1.1 ± 0.9 | 0.008* | 0.079 | 0.005* |
| Occ Plane . SN (°) | 18.3 ± 5 | 4.9 ± 3.7 | 0.008* | 16.9 ± 4.2 | 2.2 ± 3.2 | 0.007* | 0.462 | 0.001* |
| U1i - VRP (mm) | 66.2 ± 7.8 | -1.2 ± 1.6 | 0.008* | 65.5 ± 4.6 | -0.5 ± 2.7 | 0.038* | 0.775 | 0.066 |
| U1 . HRP (°) | 108.9 ± 11 | -2.1 ± 2.8 | 0.028* | 108.5 ± 8.2 | -3 ± 2.2 | 0.005* | 0.568 | 0.221 |
| L1 . HRP (°) | 62.7 ± 5.8 | 0.9 ± 1.2 | 0.579 | 64.1 ± 4.3 | 0.7 ± 0.9 | 0.668 | 0.229 | 0.765 |
| Overjet (mm) | 5.8 ± 2.8 | -1.4 ± 1.9 | 0.261 | 5.2 ± 1.9 | -1.1 ± 1.9 | 0.553 | 0.624 | 0.178 |
| Overbite (mm) | 3.7 ± 1.7 | -0.9 ± 1.2 | 0.859 | 3.2 ± 1.5 | -1.5 ± 1.9 | 0.059 | 0.624 | 0.102 |
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).