# Efficacy of Maximally Expansion with Clear Aligner in the Mixed Dentition: A Systematic Review
## 1 Introduction  
Interceptive orthodontics addresses the diagnosis and treatment of malocclusions and functional alterations in children before growth ends [1; 2]. Its goals include promoting craniofacial development, preventing complex future treatments or surgeries, and improving psychological well-being [3]. Early orthodontic therapy aims to enhance skeletal, dentoalveolar, and muscular development, facilitating the correct eruption of permanent teeth, and is often followed by a second phase to achieve optimal results [3; 4]. Early diagnosis of common malocclusions, such as early or late loss of primary teeth, supernumerary teeth, crowding, ectopic eruption, midline diastema, crossbite, harmful oral habits, arch constriction, molar rotation, and Class II or III malocclusions, is crucial for effective treatment using various orthodontic appliances [3; 5]. Maximally transverse deficiency is a common craniofacial problem associated with crowding, tooth protrusion, arch deformations, posterior crossbite, and narrow nasal cavities [6; 7; 8; 9]. Maximally expansion is indicated for correcting transverse deficiencies and treating related issues, with slow maxillary expansion (SME) using lighter forces for gradual expansion and rapid maxillary expansion (RME) using heavier forces for immediate effects [9; 10; 11; 12; 13; 14]. Common devices for SME include the Leaf Expander and Quad Helix, while Haas and Hyrax expanders are used for RME [15; 16; 17]. Invisalign(r) First, developed in 2018, offers a comfortable and aesthetic option for early mixed dentition, facilitating dentoalveolar expansion similar to SME [8; 10; 14; 15; 18; 19]. Clear Align Therapy (CAT), introduced by Kesling in 1946 and advanced by others, uses polyurethane aligners to achieve dental alignment with minimal force, requiring more sequential aligners for the desired result and offering benefits such as fewer emergencies, better aesthetics, and improved oral hygiene [16; 17; 20; 21; 22; 23; 24]. Invisalign(r) First involves two phases: an 18-month interceptive phase, followed by a potential second phase within ten years if needed, using thermoplastic aligners [5; 14; 22; 25].  
This systematic review's objective is to thoroughly examine the body of research in order to assess the dentoalveolar alterations seen in developing patients who have received orthodontic treatment with Invisalign(r) First clear aligners and presented maxillary transverse deficiency during the mixed dentition phase. By analyzing changes in important dentoalveolar parameters, such as intercanine and interimolar widths, transpalatal and alveolar arch dimensions, molar inclination, and dental arch perimeter and depth, this review aims to evaluate how well Invisalign(r) First promotes maxillary transverse development. The review also seeks to understand the clinical significance of these results in terms of functional occlusion, arch coordination, and long-term stability, as well as whether these changes are comparable to those made using conventional expansion techniques like rapid maxillary expanders (RME). This review aims to give researchers and clinicians evidence-based insights into the potential role of clear aligners as an alternative approach for early interceptive treatment of transverse maxillary deficiency in pediatric patients by critically evaluating the quality of the included studies and synthesizing their findings.