Expert consensus on the clinical strategies for orthodontic treatment with clear aligners

Abstract

Clear aligner treatment is a novel technique in current orthodontic practice. Distinct from traditional fixed orthodontic appliances, clear aligners have different material features and biomechanical characteristics and treatment efficiencies, presenting new clinical challenges. Therefore, a comprehensive and systematic description of the key clinical aspects of clear aligner treatment is essential to enhance treatment efficacy and facilitate the advancement and wide adoption of this new technique. This expert consensus discusses case selection and grading of treatment difficulty, principle of clear aligner therapy, clinical procedures and potential complications, which are crucial to the clinical success of clear aligner treatment.

Fig. 1

Predictability of different tooth movements achieved through clear aligner therapy

Fig. 2

A schematic illustration of the principles of clear aligner therapy for incisor retraction in a premolar-extraction case. A final set-up is designed based on the initial set-up and a final aligner is fabricated based on the final tooth set-up. The final aligner is topologically distinct from the pre-treatment dentition and should be elastically stretched for being fitted onto the dentition. The stretched aligner on the pre-treatment dentition is activated and generate retraction force on the anterior teeth and protraction force on the posterior teeth, resulting in premolar-extraction space closure

Fig. 3

The overview procedures of clear aligner treatment

Fig. 4

Aligner treatment planning for arch expansion. a A narrow upper arch is to be expanded. b From the buccal view, the palatal cusps of the molars can be observed (yellow arrows). c From the posterior view, the palatal cusp (yellow arrow) is more occlusal than the buccal cusps. d Buccolingual angulation of the molar is modified and a buccal root-torque is added. e The palatal cusps cannot be observed from the buccal view

Fig. 5

Different modes of elastic tractions. a Class II elastic traction is applied on the precision cut on the upper aligner. b A cut-out is designed on the upper canine and class II elastic traction is engaged ono the button on the canine

Fig. 6

Different aligner design patterns for molar distalization. a Strict V-pattern. Molars, premolars and anterior teeth move sequentially. b Modified V-pattern. Incisors move alongside molar distalization. c The first and second molars move simultaneously

Fig. 7

Different elastic tractions and biomechanical features. a A class II elastic traction is applied between the precision cut on the upper canine and the button on the lower first molar. Since the traction force (blue dashed line) passes occlusally to the center of resistance (red dot) of the upper anterior teeth, a clockwise moment (blue curved arrow) is generated. b An elastic traction is engaged between the precision cut on the upper canine and a buccal mini-implant. Likewise, a smaller clockwise moment (blue curved arrow) is generated. c One elastic traction is applied between the precision cut on the canine and a buccal mini-implant and the other one is engaged between the aligners on the incisors and a labial mini-implant. The retraction force (blue dashed line) generates a clockwise moment (blue curved arrow) while the intrusion force (yellow dashed line) offers a counterclockwise moment (yellow curved arrow). The two moments are offset by each other and the anterior teeth are retraction in a bodily movement mode

Fig. 8

Staging design for the intrusion of anterior teeth in the lower arch. a Incisors and canines are intruded in an alternate mode. Incisors are intruded first (referred to stage 1), followed by the intrusion of canines (referred to stage 2). Then, incisors are further intruded (referred to stage 3). b Lower arch models showing intrusion of canines and incisors corresponding to the aforementioned three stages. c Anterior and side views showing the successful intrusion of the anterior teeth

Fig. 9

Aligner off-tracking. a Off-tracking of upper incisors (yellow arrows). b Off-tracking of a lower incisor (yellow arrow). c Off-tracking of a lower canine and first premolar (yellow arrows). d Off-tracking of an upper premolar (yellow arrow). e Off-tracking of an upper premolar and molar (yellow arrows). f Off-tracking of a lower molar (yellow arrow)

Fig. 10

Strategies for resolution of tooth off-tracking. a A “boot-strapping” technique was used to address the off-tracking of a lateral incisor by applying labial-lingual elastic traction. b A power chain was used to correct under-derotation of a second premolar. c A vertical elastic traction from the upper premolar to the lower molar was implemented to correct mesial tipping and intrusion of the lower first molar. d A segmental archwire technique was applied to correct mesial tipping of a lower second molar