Analysis of the efficacy of conventional, skeletal and invisible orthodontic appliance for upper molar distalization in Class II Malocclusion patients: a systematic review and meta-analysis

Abstract

Background/objectives: To assess the efficacy of conventional, skeletal and invisible orthodontic appliance for maxillary first molar distalization.

Methods: On February 14, 2023, an electronic search was conducted to review molar distalization using conventional, skeletal and invisible appliance, and two updated searches were conducted on August 31, 2023 and November 31,2024. After study selection, data extraction and risk of bias assessment, meta-analyses were performed for molar distalization, molar tipping, incisor movement, incisor tipping and mandibular plane angle change using random-effects model.

Results: 55 studies fulfilled inclusion criteria, and 26 studies underwent meta-analysis. The clear aligner group demonstrated a significant reduction in upper molar distalization and tipping (2.33mm; 3.01°) compared to conventional appliance (3.29mm; 6.39°) and skeletal appliance (3.48mm; 5.84°) groups. Conventional appliance group experienced a significantly greater loss of anchorage (1.69mm; 3.99°) and a greater increase in mandibular plane angle (0.66°). Molar distalization after the eruption of the maxillary second molar may lead to greater loss of anchorage (1.76mm; 3.99°). 4-premolar-support group (4.09mm; 8.24°) appeared to produce more molar distalization and tipping than 2-premolar-support group (2.72mm; 4.90°). Buccal-miniscrew subgroup exhibited a smaller molar distalization(2.01mm) compared to palatal-miniscrew (3.81mm) and infrazygomatic-miniscrew subgroups(4.90mm).

Conclusions: The use of clear aligners resulted in a decrease in molar distal tipping but also led to a reduction in distalization, while the use of conventional appliances resulted in higher anchorage loss and a greater increase in mandibular plane angle. Distalization after the eruption of U7 may increase the risk of anchorage loss. 4-premolar-support anchorage improved the molar distalization, but also increased molar tipping in comparison to 2-premolar-support anchorage. Alternatively, palatal miniscrew support resulted in higher distal tipping but less incisor distal movement and tipping. However, additional RCTs or prospective studies are strongly recommended to provide further clinical evidence.

Keywords: Clear aligner; Conventional appliance; Molar distalization; Skeletal anchorage.

Fig. 1

PRISMA flow diagram

Fig. 2

Forest plots for molar distalization effect with conventional appliance, skeletal appliance and clear aligner. A incisor mesial movement; B incisor mesial tipping; C U6 distalization; D U6 tipping; E mandibular plane angle change (SN-MP). (+): incisor mesial movement, incisor mesial tipping, U6 distal movement, U6 distal tipping or increase in mandibular plane angle. (-): incisor distal movement, incisor distal tipping, U6 mesial movement, U6 mesial tipping or decrease in mandibular plane angle

Fig. 3

2-premolar support VS 4-premolar support anchorage in conventional appliance group

Fig. 4

U7-erupted VS U7-unerupted subgroups in conventional appliance group

Fig. 5

Buccal-miniscrew VS palatal-miniscrew VS infrazygomatic-miniscrew anchorage in skeletal appliance group

Fig. 6

Sensitivity analysis of the conventional group. A incisor mesial movement; B incisor mesial tipping; C U6 distaliation; D U6 tipping; E mandibular plane angle change (SN-MP)

Fig. 7

Sensitivity analysis of the skeletal group. A incisor mesial movement; B incisor mesial tipping; C U6 distaliation; D U6 tipping; E mandibular plane angle change (SN-MP)