Histone Compound Library Rapid maxillary expansion RME is a

Rapid maxillary expansion (RME) is a widely used practice in orthodontics. The purpose of RME is to correct transverse maxillary deficiency, a rather common skeletal anomaly of the maxillofacial area. It is often found in children with impaired respiratory function [1–5]. Scientific evidence shows that RME can be helpful in modifying the breathing pattern in these patients. This modification involves nasal cavities [6–11] and, indirectly, the jaw. The jaw is thus repositioned and this causes the root of the tongue to move forward [12] and it changes the pharyngeal structures [13]. Early studies related to the effect of RME on the nasal cavity and on breathing patterns date back to 1886 [14]. Several studies on the same topic were published later. Postero-anterior cephalometry [7,8,15,16], latero-lateral cephalometry [17,18] and tomography [11,19–22] have been used to estimate the changes in shape and size of the nose. Acoustic rhinometry [7,8,23–25] and rhinomanometry [7,8,26,27] have been used to adequately assess the airflow. The former provides anatomical information about the nasal airways (minimal cross-sectional area—MCA, minimal cross-section volume—MCV), while the latter measures the nasal resistance to airflow (nasal air resistance—NAR), an essential parameter for a functional assessment. In addition, in some studies, patients were asked to respond to special questionnaires in order to determine their perceptions on changing their breathing [28–30]. Hershey et al. [28] performed a comprehensive evaluation of the nose-breathing parameters mentioned above and it reported positive changes in the amplitude of the nasal cavities and a reduction in the values of NAR after RME to levels comparable to those of physiological nasal breathing. Those values would remain almost unchanged in the post-expansion contention months mentioned in the study. Additionally these Authors did not find any significant variations between the values of NAR in subjects who reported a subjective improvement in breathing and those reported no improvement. In later decades, other Authors analyzed changes in one or more of the parameters described above, which in most cases, caused dimensional and volumetric expansions of the nasal cavity, in particular of its lower part, and a decrease of the NAR. The stability effect achieved by RME and its role in actually changing breathing patterns remains a subject of debate. This debate is still ongoing despite evidence of anatomical and functional changes in the nasal complex after RME, as reported in the orthodontic literature, and notwithstanding the enthusiasm among some Authors who support the Histone Compound Library that it is a means to eliminate or reduce the problem of mouth breathing. Clinical practice presents many cases in which, in spite of orthodontic treatment recovery of all the dental and skeletal conditions for a restoration of physiological nasal breathing, oral breathing persists. Cases of children who underwent tonsillectomy or adenectomy, did not experience an adequate functional recovery despite a clear airway are also common. Hershey et al. [28] confirmed the thesis of Watson et al. (1968—cited in Hershey et al. [28]) pointing out that the reduction of the NAR does not necessarily coincide with a disappearing of mouth breathing in a child. He concluded that RME, although it could potentially result in the recovery of the respiratory function also in the case of nasal stenosis, does not guarantee a resolution of all cases of oral breathing. According to Warren et al. [31] the enlargement of the nasal cavity is not sufficient to modify breathing patterns, in particular in cases of nasal obstruction. An analysis of recent reviews of the literature [9,10,32] has shown that a change in breathing after RME does not represent a predictable result to the point that mouth breathing does not seem to be a primary reason for an expansion procedure. Compradetti et al. [8] also report that a certain percentage of children, in spite of having structurally adequate nasal airways, do not change their breathing pattern from oral to nasal, which would lead to the need to ‘learn’ how to breathe properly. In order to promote the restoration of physiological breathing, it might be helpful to associate the expansion of the palate to myofunctional rehabilitation practices. Several articles in orthodontic literature highlight the need to combine orthodontic treatment with myofunctional therapeutic procedures [33–36]. Several procedures are meant to correct the position and the abnormal function of the tongue [34,37], while less emphasis is put on specific breathing exercises included in an orthodontic treatment plan [1,2,3,38–42]. Cozza et al. [40] describe a myofunctional rehabilitation program supporting the traditional orthodontic therapy in patients affected by breathing problems. The program involves exercises for the proprioception of the primary breathing apparatus, a costo-diaphragmatic training and respiratory exercises. The Authors underline that this rehabilitation program is advised to patients diagnosed with chronic mouth breathing, i.e. without any mechanical obstruction of the upper respiratory tract. Villa et al. [39] treated a group of children with nasal chronic obstruction with a myofunctional therapy aimed to re-establish a physiological nasal breathing and lip seal as well as to modify an abnormal swallowing pattern. Their protocol includes nasal exercises for the mobility of alar cartilages, labial exercises to straighten orbicularis oris muscles, tongue exercises to improve swallowing and breathing body exercises. Nasal irrigations using a hypertonic saline solution was added to the myofunctional therapy. The results showed that both myofunctional rehabilitation and nasal irrigation improve significantly nasal obstruction, oral breathing and chronic snoring in 5–10 years old children. A physical therapy program for mouth breathing children was adopted by Correa and Bérzin [41]: muscular stretching and strengthening exercises using a Swiss ball were combined to naso-diaphragmatic re-education. However, the study focuses on the effectiveness of this therapeutic program on cervical muscle activity and body posture which would have seemed to be impaired in the patients in question. No evaluations were made with regards to changes that occur in the respiratory pattern. Guimarães et al. [42] use a myofunctional approach consisting of oro-pharyngeal exercises derived from the traditional speech therapy techniques; it involves the soft palate, the tongue and mandibular and facial muscles. These exercises, combined with insufflation ones, would eventually lead to an improvement in adult patients affected by obstructive sleep apnea (OSA) as an outcome of the upper airway remodeling and its subsequent increase of patency. In a randomized placebo-controlled study Diaféria [43] evaluates the effects of speech therapy on clinical and polysomnographic parameters in obstructive sleep apnea syndrome (OSAS) patients and concludes that speech therapy could reduce OSAS symptoms and increase the adherence to the treatment with continuous positive airway pressure (CPAP). The speech therapy consists of muscular endurance exercises aimed at toning the oropharynx muscle groups, optimizing muscle tension mobility and adjusting the position of the soft tissues and the suitability of the chewing, sucking, swallowing and breathing orofacial functions, according to previously standardized protocols [44–50]. In a later study Diaféria et al. [51] confirm that speech therapy, alone as well as in association with CPAP, leads to an improvement of quality of life in patients with OSAS. Dantas et al. [52] focuses on the genesis of the upper airway collapsibility in adult patients with OSAS. The Authors suggest that an increased collagen type I in the pharyngeal muscular wall in patients with OSAS could delay the contractile-relaxant responses of the pharyngeal muscles during the transition from inspiration to expiration, increasing pharyngeal collapsibility. Exercises that target the oropharynx region increase the strength of the oropharynx muscles, thus repositioning the tongue under anteroposterior stress, could help to reduce the collapse of the pharynx. The increased strength of the tongue and the soft palate related to the speech therapy could explain the improvement of the Modified Mallampati Index (MMI) and the other objective sleep parameters in patients affected by OSAS [43]. Scientific evidences for speech therapy in children affected by OSAS are rare. Schievano et al. [53] reported an enhanced respiratory function experienced by habitual mouth breathing population who underwent a therapeutic program based on facial massages and myofunctional exercises involving mental, labial and lingual area, feeding re-education included. The Authors argue that the muscular and functional alterations were not completely recovered due to the lack of morphological and structural correction during the therapeutic period; thus they underline the need for a multidisciplinary approach to solve the problem From these considerations, this study aims to present a literature review and a model of orofacial rehabilitation in children with obstructive sleep apnea undergoing treatment with rapid maxillary expansion. Once, speech therapy presents a promising future in the treatment of patients with obstructive sleep apnea and the lack of standardization of rehabilitation exercises of oronasal in different studies, were the main reasons that encouraged the making of this article.