21 January 2023

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Comparison between clear aligners, 2 × 4 mechanics in mixed dentition

Davide Elsido

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Prevalence of malocclusion in the mixed dentition can range from 39% to 93%, depending on sex, ethnic group, age and type of malocclusion. Dental crowding, interdental spacing and increased overjet are commonly associated with appearance dissatisfaction and negatively affect a child's oral health–related quality of life.

Simplified “two by four” (2 × 4) orthodontic mechanics with brackets bonded to the four permanent incisors and tubes or bands placed on the two first permanent molars is indicated to resolve maxillary and mandibular incisor crowding in the mixed dentition.

Currently, clear aligners are an option for resolving incisor crowding during the mixed dentition. There is agreement from recent studies that the evidence reporting on clear aligners in children remains scarce, indicating that more clinical trials are needed.

Applicability for treating anterior crowding in children is still questionable because of the high dependence of clear aligner success on compliance. No previous studies have compared the treatment outcomes between clear aligners and 2 × 4 mechanics in the mixed dentition. 

The purpose of a RCT published in the January 2023 issue of the Angle Orthodontist was to evaluate and compare the efficacy and efficiency between fixed appliances and clear aligners for resolving maxillary incisor irregularity in the mixed dentition. The null hypothesis was that both orthodontic appliances would have similar outcomes.

The sample included 32 patients from seven to 11 years of age randomly allocated into two parallel treatment groups. 

Treatment time was approximately eight months in both groups. No intergroup differences were observed for changes in any of the variables. Similar posttreatment arch shapes were observed in both groups.

Previous studies showed that adolescents demonstrated greater compliance rates with oral hygiene when treated with clear aligners.  Despite hygiene guidance and adequate follow-up, white spot lesions were observed in both groups after treatment. 

According to the study, clear aligners and 2 × 4 mechanics displayed similar efficacy and efficiency for maxillary incisor position corrections in the mixed dentition. The choice of appliance should be guided by clinician and family preference.

Vinicius Merino da Silva, Priscila Vaz Ayub, Camila Massaro, Guilherme Janson and Daniela Garib. “Comparison between clear aligners and 2 × 4 mechanics in the mixed dentition: a randomized clinical trial.” Angle Orthod (2023) 93 (1): 3–10.