## 1 Introduction  
Maxillary transverse deficiency (MTD) represents one of the most common skeletal deformities of the craniofacial region [1; 2]. Skeletal maxillary expansion, in the form of rapid and slow maxillary expansion protocols (SME) [3], is an efficient therapy for the treatment of MTD. Usually, the diagnosis of MTD is based on visual inspection of posterior-crossibite, despite the fact that transverse dento-alveolar compensation may cause underestimation of this condition [4]. In particular, dento-alveolar compensation may mitigate the negative effect of MTD on the occlusion as well as camouflage specific morphological characteristics of the maxilla such as the asymmetry of the palatal vault and/or of the dento-alveolar processes [5]. The analysis of morphological characteristics of the maxilla is fundamental for a correct diagnosis and treatment plan of MTD. In this respect, the awareness of the symmetry/asymmetry of the maxilla will guide the clinicians in choosing the design of the maxillary expander for each patient [5; 6].  
To date, progress in 3D imaging has opened new scenarios for the evaluation of anatomical characteristics and morphological changes in dentistry [7; 8]. In the orthodontic field, for example, digital scans of maxillary and mandibular jaws can be registered (superimposition) and deviation analysis can be used to detect shape and to obtain detailed dimensional information. Moreover, 3 Dmodels of the maxilla and/or mandible of the same subject can be mirrored and superimposed in order to detect anatomical asymmetry as well as asymmetrical changes between two sides [9; 10; 11]. This information can be provided by referring to \"surface-to-surface\" analysis, and can be visualized in colors in a 3D color-map [9; 10; 11].  
Once a correct diagnosis and treatment plan are established, clinicians are concerned about the total treatment time required for reaching clinical outcomes. This is particularly relevant in young patients, when orthodontic therapies should be as efficient as possible in order to maintain patients' compliance. In this respect, photobiomodulation (PBM) represents the new frontier for expediting orthodontic movement, as confirmed by previous clinical studies [12; 13; 14; 15]. In particular, photobiostimulation is a noninvasive irradiation procedure that uses a laser light within the red to near-infrared range (wavelengths from 632 to 1064 nm) to provoke a biological reaction. In-vitro studies reported that photobiostimulation accelerates cellular turnover by increasing the expression of osteoclast [16], stimulating angiogenesis [17], and the availability of mitochondrial ATP [18; 19].  
In this respect, the present study shows an updated approach to reach a comprehensive diagnosis and efficient orthodontic treatment. In particular, we showed the case of a seven-year-old female affected by transversal maxillary deficiency and anterior openbite. The diagnostic phase included a specific procedure involving mirroring, superimposition, and deviation analysis of 3D models of the maxilla, to detect morphological characteristics of the palatal vault. The therapeutic phase involved the use of photobiomodulation to expedite the correction of crossbite and anterior-openbite.