Korean J Orthod.  2024 Mar;54(2):117-127. 10.4041/kjod23.150.

Evaluating anchorage loss in upper incisors during distalization of maxillary posterior teeth using clear aligners in adult patients: A prospective randomized study

• Yurdakul Z
• Karsli N

• KMID: 2554368
• DOI: http://doi.org/10.4041/kjod23.150

Abstract

Objective
To evaluate the effect of clear aligner treatment and differential sequence distalization of maxillary posterior teeth on anchorage loss in the upper incisors (U1s).
Methods
This study used lateral cephalometries and digital models of 12 patients treated with 33% sequential distalization (group 1, mean age: 22.9 ± 0.7 years, five males, seven females) and 12 treated with 50% sequential distalization (group 2, mean age: 25.83 ± 0.5 years, three males, nine females) acquired before and after distalization of upper second premolars (U5) and upper first molars (U6) and upper second molars (U7). The amount of distalization was determined as 2.5 mm in both the groups. Independent Samples t test was used to compare normally distributed parameters. Mann– Whitney U and Wilcoxon tests were used to compare parameters that were not normally distributed.
Results
In both groups, the posterior teeth significantly moved by tipping distally and the U1s were displaced anteriorly. Increase in maxillary posterior transverse width (P < 0.001) and distopalatal rotation were observed in U5, U6, and U7 after distalization. It was also observed that U1 was significantly more proclined (1.82°; P < 0.001) and protruded (0.62 mm; P < 0.001), and the overjet (0.45 mm; P < 0.001) increased more in group 1 than in group 2.
Conclusions
After sequential distalization of maxillary posterior teeth, more anchorage loss was observed in the anterior region in group 1 than in group 2.

Keyword

Clear aligner; Distalization; Anchorage

Figure

• 

  Figure 1 Dental angular measurements on cephalometric radiography. (1) U7/HR, (2) U6/HR, (3) U5/HR, (4) U1/HR. Determination of the long-axis of the teeth: crown tip of U1 and root apex point were marked, crown centroid point of U5 and root apex point were marked, crown centroid point of U6 and U7 and trifurcation point were marked. Centroid point of crown: the midpoint of the mesial and distal convexity of the crown of the molar tooth was accepted as the centroid point of crown. U7, upper second molars; U6, upper first molars; U5, upper second premolars; U1, upper incisor; HR, horizontal plane; VER, vertical plane; HOR, horizontal plane.

• 

  Figure 2 Dental linear measurements on cephalometric radiography. (5) The distance from crown centroid point of U7 to the horizontal plane (U7-HR), (6) the distance from crown centroid point of U6-HR, (7) the distance from crown centroid point of U5-HR, (8) the distance from crown tip point of U1-HR, (9) the distance from crown centroid point of U7 to the vertical plane (U7-VR), (10) the distance from crown centroid point of U6-VR, (11) the distance from crown centroid point of U5-VR, (12) the distance from crown tip point of U1-VR, (13) overjet, (14) overbite, (15) Ls-E, (16) Li-E. U7, upper second molars; U6, upper first molars; U5, upper second premolars; U1, upper incisor; Ls, labrale superius; Li, labrale inferius; E, the line between the soft tissue pogonion and tip of the nose; VER, vertical plane; SN, sella-nasion plane; HOR, horizontal plane.

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  Figure 3 Sagittal linear measurements on the digital model. Line G: line tangent to inferior border of palatal rugae and perpendicular to midpalatal raphe. (1) The distance from incisor tip of 11 to G line, (2) the distance from incisor tip of 21 to G line, (3) the distance from incisor tip of 13 to G line, (4) the distance from crown tip of 23 to G line, (5) the distance from buccal cusp tip of 15 to G line, (6) the distance from buccal cusp tip of 25 to G line, (7) the distance from mesiobuccal cusp tip of 16 to G line, (8) the distance from mesiobuccal cusp tip of 26 to G line, (9) the distance from mesiobuccal cusp tip of 17 to G line, (10) the distance from mesiobuccal cusp tip of 27 to G line.

• 

  Figure 4 Transverse measurements and arc length (mm) on the digital model. (11) Transverse width between 15–25, (12) transverse width between 16–26, (13) transverse width between 17–27, (14) arch length: the distance between the contact point of the upper incisors and the mesial contact points of the upper first molars.

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  Figure 5 Rotation measurements on the digital model. Upper right second premolar: the angle between the mid-palatal raphe and the line passing through the mesial and distal convex ridges of right maxillary second premolar. Upper left second premolar: the angle between the mid-palatal raphe and the line passing through the mesial and distal convex ridges of left maxillary second premolar. Upper right first molar: the angle between the mid-palatal raphe and the line passing through the mesiobuccal and distobuccal cusps of the right maxillary first molar. Upper left first molar: the angle between the mid-palatal raphe and the line passing through the mesiobuccal and distobuccal cusps of the left maxillary first molar. Rotation measurement of upper right second molar: the angle between the mid-palatal raphe and the line passing through the mesiobuccal and distobuccal cusps of the right maxillary second molar. Upper left second molar: the angle between the mid-palatal raphe and the line passing through the mesiobuccal and distobuccal cusps of the left maxillary second molar.

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