## 1 Introduction  
Transverse discrepancy refers to a condition characterized by a disparity in the transverse dimensions between the upper and lower dental arches. This anomaly significantly impacts the alignment of the dental arches and is of particular concern in growing patients. Early interceptive treatment is essential to minimize the need for more invasive procedures in adulthood. Recent studies emphasize the importance of addressing this malocclusion during childhood, as it typically worsens with the development of permanent dentition [1]. A study conducted in 2017 at the Universidad Nacional Mayor de San Marcos [2] involved 155 children aged 6 to 12 years. Of these, 71% exhibited some form of malocclusion, including a transverse deficiency in the upper jaw. This condition is one of the most prevalent orthognathic anomalies and is often associated with unilateral or bilateral posterior crossbite, upper jaw crowding, or other malocclusions. Transverse deficiency of the upper jaw is prevalent during the early deciduous and mixed dentition stages, with an estimated prevalence of 8% to 20% in the pediatric population [2; 3; 4]. The causes of transverse discrepancies are multifactorial, involving a complex interaction of genetic, environmental, sexual, and acquired factors that influence the child's growth and development. Genetics plays a key role in intra-arch development, determining the final position of teeth in both the upper and lower arches. The curvature of the dental arch, the maxillary intercanine and interimolar widths, and the eruption path of teeth are influenced by genetic factors, but external factors can also affect them [5]. Males typically exhibit a wider posterior arch width, which is a result of differences in the growth rates of the skull and facial bones. Environmental influences, as proposed by [PERSON]'s theory, are equally significant. According to this theory, craniofacial growth is influenced not only by genetics, but also by functional factors such as muscle activity and nasopharyngeal functions. Consequently, oral habits like thumb sucking, atypical swallowing, and mouth breathing are major contributors to the development of dental arch abnormalities. Acquired factors, such as trauma (prenatal, perinatal) or premature loss of deciduous teeth, can also disrupt the eruption of permanent teeth and interfere with arch alignment [6]. Assessing the specific characteristics of the transverse discrepancy and any associated malocclusions is essential for therapeutic planning. Correcting transverse discrepancies is a primary goal in many orthodontic treatment protocols. These discrepancies are frequently linked with posterior crossbite, class II and III malocclusions, dental crowding, and open bite. If the condition involves the basal structure of the arches, it is referred to as a skeletal discrepancy [7]. If the basal structure is not involved, the discrepancy is classified as dentoalveolar. In this case, the arches misalign at the tooth level due to anomalies in the eruption sequence, which leads to palatal tilting of the alveolar processes and incorrect angulation of the upper teeth. These misalignments usually do not exceed 4 to 5 mm and can often be corrected with orthodontic treatment in children aged 6 to 12 years. In recent years, introducing innovative devices such as balancers and aligners has marked a significant advancement in treating transverse discrepancies. Balancers, removable silicone devices, are commonly used due to their elasticity and durability, providing both dental and orthopedic benefits. These devices help to align teeth and address various malocclusions. The primary goal of Eptamed is to restore stomatognathic functions, such as swallowing and breathing, while also addressing maladaptive oral habits [8]. Aligners, on the other hand, offer aesthetic benefits, reducing the typical emergencies associated with fixed appliances, such as soft tissue injuries. They also promote better oral hygiene by allowing removal during meals and cleaning.