Bone Modifications Induced by Rapid Maximillary Expander: A Three-Dimensional Cephalometric Pilot Study Comparing Two Different Cephalometric Software Programs  
[PERSON]  
Centre-beam computed tomography (CBCT) represents important technological progress in the fields of tomographic acquisition and volumetric reconstruction [1]. The approach involves a significantly reduced radiant dose compared with traditional computed tomography (CT) and provides all of the radiological information required for a complete study of an orthodontic case [2, 3]. CBCT has been increasingly performed in orthodontics to study 3D craniofacial anatomy in order to improve diagnosis and treatment planning, and to assess treatment outcomes [4]. This imaging technique can be useful to examine many pathological conditions, such as impacted and supernumerary teeth, cleft lip and palate, asymmetries, root resorption, obstructive sleep apnea (OSA), TMJ disorders and maxillary transverse deficiency [5]. A rapid maxillary expander (RME) is indicated in growing patients with maxillary width deficiency [6], as it applies orthopedic forces resulting in the widening and gradual opening of the midpalatal suture, compression of the periodontal ligament, bending of the alveolar processes and dental tipping [7]. As a result, the maxillary bones widen on the transverse plane, with the frontonasal suture as the approximate center of rotation [8]. Although the midpalatal suture is subjected to the majority of the effects of the RME, the surrounding frontomaxillary, zygomaticomaxillary, zygomaticotemporal and pterygopalatine sutures also experience some changes [9]. Sometimes, the RME can improve nasal breathing by widening the nasal cavities [10]. Different studies in the literature evaluated the craniofacial outcomes of RME therapy [11; 12]. In the past, these effects were evaluated using lateral and posteroanterior cephalosporgrams; however, CBCT now provides the opportunity to conduct a 3D analysis [11]. Radiography guidelines in the USA and Europe promote the \"As Low As Reasonably Achievable\" (ALARA) principle, especially when dealing with orthodontic patients who are mostly children, because of their attributable lifetime radiation risk [13; 14]. If it is necessary to perform a CBCT, it must be executed using the smallest possible field of view [4]. According to systematic reviews [15; 16], CBCT, and even 2D radiographs, which are generally taken routinely, should only be performed when they could offer more information useful for diagnosis or treatment planning or for evaluating progress or complications during the therapy. Two-dimensional cephalometric measurements are often inaccurate due to mistakes concerning landmark identification and projections [17], whereas 3D techniques allow these issues to be overcome thanks to the ability of dedicated programs to three-dimensionally rotate the image [18]. The rapid development of CBCT technology led to the introduction of various programs for orthodontists, with subsequent comparisons being made among them, as far as reliability and accuracy are concerned [19; 20]. According to [PERSON] et al. [21], the 3D analysis provided by dedicated programs helps to avoid human error, reduces inter- and intra-individual variation and increases the reliability and repeatability of diagnoses. [PERSON] and his colleagues [22] also reported the significant reliability of 3D cephalometric analysis performed by dedicated programs compared with the traditional manual technique. Many studies in the literature demonstrate how 3D software can provide a more reliable cephalometric analysis compared to the manual approach, obtaining more precise information that can improve diagnosis and treatment planning [23]. The programs available on the market are able to perform cephalometric analysis such as growth forecasts and treatment simulations. Some of these are capable of superimposing multiple cephalometric traces with pictures of the patient, also allowing the simulation of the effects of treatment on the soft tissues [24; 25].