INTRODUCTION

Rapid maxillary expansion (RME) is routinely used in the management of maxillary transverse deficiency, which can be manifested by a high-arched palate and posterior crossbite. Maxillary constriction can be accompanied by several functional problems, such as increased nasal resistance, narrowing of the pharyngeal airways, lower tongue posture, and incorrect swallowing pattern. It has been asserted that utilization of RME can result in improvements in those sequelae.^1–5

Swallowing is a complex function including the oral, pharyngeal, and esophageal stages. Dysphagia is a swallowing dysfunction occurring in any or all of these stages; however, affected patients can be unaware of their disorder. The pressure of the tongue against the palate and the propulsion of the bolus to the pharynx are the crucial stages of the oral phase. The inability to ensure pressure of the tongue against the palate to propel a food bolus effectively and safely can result from anatomic or pathologic problems or dysfunctional activity.^6–8

An electropalatographic study reported better tongue adaptation to the widened palate and increased duration of tongue-palate contact after slow expansion.⁹ Additionally, according to a cephalometric study, low tongue posture improved after RME in children without a respiratory disorder.² It has been shown in a study using cone-beam computed tomography that RME raised the tongue posture in the group that demonstrated improvement in nasal ventilation.³ It is possible that individuals with maxillary constriction may be predisposed to dysphagia, and RME might improve swallowing by providing the space needed to generate the tongue pressure necessary for food bolus propulsion. However, RME therapy from a dysphagia perspective has not been evaluated previously.

The aim of the present study was to evaluate objectively the evidence of probable oropharyngeal dysphagia (OD) in adolescents with transverse maxillary deficiency with posterior crossbite and high-arched palate, before and after RME.

MATERIALS AND METHODS

The study protocol was approved by the Ethics Committee of the School of Medicine, Ege University (18-3.1/73). The RME group (RMEG) included 20 patients (five males and 15 females from 11 to 15 years with a mean age of 13.0 ± 3.1) who required RME prior to comprehensive orthodontic treatment. Criteria for selection of RME subjects included: (1) bilateral posterior crossbite with a high-arched palate and 0–4 mm of overbite and overjet, (2) no adenotonsillar hypertrophy, (3) no atypical swallowing pattern, (4) no craniofacial abnormalities or temporomandibular disorders, (5) no neurological disorders or medical diseases that would cause dysphagia.

The control group (CG) consisted of 20 volunteers (four males and 16 females from 12 to 15 years with a mean age of 13.4 ± 2.6) with Class I crowding, who did not receive orthodontic treatment and were similar in age and sex to the RMEG. Criteria for selection of control subjects included: (1) Class I malocclusion with 0–4 mm of overbite and overjet without posterior crossbite or high-arched palate, (2) no mouth breathing, (3) no atypic swallowing pattern, (4) no craniofacial abnormalities, (5) no neurological disorders or medical diseases that would cause dysphagia.

A Hyrax-type maxillary expander was used for the correction of posterior crossbite. When the palatal cusp of the maxillary first molars contacted the buccal cusp of the mandibular first molars, the device was maintained in situ as a passive retainer for 6 months. The swallowing in RMEG was evaluated before (T1) and one month after the removal of the RME appliance (T2). In CG, the evaluation of swallowing was performed only once, corresponding to T1 of RMEG.

Initially, patients were screened for OD using EAT-10 (Table 1).¹⁰ EAT-10 is a 10-item questionnaire designed to assess “symptom severity, quality of life, and treatment efficacy.” Each item is scored from 0 to 4 (0 = no problem, 4 = severe problem).

Table 1. Eating Assessment Tool-10 Questionnaire¹⁰

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A case report form (CRF) was designed for the current study based on the physical examination of swallowing function (dysphagia with water, semisolid, and solid food, and multiple swallowing) and patient complaints (sensation of choking, the need to clear the throat and sensation of having a lump in the throat and need to clean the throat). Also, it included information on whether the patient had difficulty in nasal breathing or previous adenotonsillectomy.

Fiberoptic endoscopic evaluation of swallowing (FEES) was performed using a flexible fiberoptic endoscope (3.6 mm in diameter; Olympus, Melville, NY, USA), a digital camera, and a video recording system (KayPentax Ltd, Montvale, NJ, USA). A flexible fiberoptic endoscope was inserted by the otolaryngologist into each subject’s nose to the level of the soft palate, and video recordings were obtained for each patient. The test protocol included administration of 3, 5, and 10 mL of water two times, 1 teaspoon (5 mL) of yogurt, and one fish-shaped cracker (2 g), all colored with food dye. When residue was detected during the test, dyed food was cleared by having the individual drink water. In this study, semisolid food (yogurt) was always given first, followed by liquid and solid food.

The presence of the following FEES parameters was noted: (1) pharyngeal residue, (2) laryngeal penetration (food residue encroaching on the airway, above the vocal folds with or without coughing), and (3) laryngotracheal aspiration (presence of material below the vocal folds).

The Yale Pharyngeal Residue Severity Rating Scale was used to indicate the amount of residue found in the vallecula and piriform sinus,¹¹ whereas residue on the pharyngeal wall and retrocricoid region was scored in a binary fashion (ie, present or absent).

An otolaryngologist and a physical therapy and rehabilitation specialist were present during each FEES procedure; all procedures were recorded by video. CRF and the assessment of the test results were carried out by the same otolaryngologist and physician experienced in dysphagia.

RESULTS

Of 20 individuals in RMEG, 12 had difficulty with nasal respiration. It was detected that nine patients experienced enhanced nasal respiration while there was no improvement in respiratory pattern in three patients after the expansion as identified by clinical examination and family consultations. The mean amount of intermolar expansion at the coronal level was 6.83 ± 1.40 mm. The SN-GoGn angles in the study and control groups were 39.20 ± 3.43 and 34.45 ± 3.68, respectively.

In RMEG, the number of patients who experienced a sensation of having a lump in the throat, choking, and a need to clean the throat at T1 was 2 (10%), 1 (5%), and 3 (15%), respectively. At T2, the number of patients who experienced choking or a need to clean the throat was 1 (5%). No patients in either group exhibited dysphagia with water, solid, and semisolid items at T1 or T2. Regarding any of the aforementioned symptoms and findings, as well as EAT-10 scores, no statistically significant differences were found between CG and RMEG at T1 and in the comparison of pre- and post-RME assessments (P > .05) (Table 2).

Table 2. Symptoms and Findings in the Groups and Comparisons Between Groups Based on Patient Complaints and Physical Examination of Swallowing Function^a

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Considering FEES findings, in RMEG, residue with 10 mL water at T2 was detected in a greater fraction compared to T1; however, the difference between T1 and T2 was not significant. The number of patients displaying residue with yogurt was 4 (20%) in CG and 12 (60%) in RMEG at T1, and the difference between the two groups was significant (P < .05). There was no significant difference in total residue with crackers between pre-and postexpansion assessments (P > .05). The severity of residue detected in the vallecula or pyriform sinus was a trace in CG, whereas it varied from trace to moderate in RMEG at T1. At T2, there was a decrease in the severity manifested as trace or mild. Both groups did not demonstrate penetration or aspiration during the FEES examination (Table 3). Images of one patient acquired with a fiberoptic endoscope during swallowing with yogurt at preexpansion and postexpansion evaluations are presented in Figure 1.

Table 3. FEES Findings in Groups and Comparisons Between Groups^a

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DISCUSSION

Transverse maxillary deficiency can have a negative impact on patient quality of life.^13–15 Although providing treatment using RME leads to a better quality of life related to breathing, oral symptoms, functional limitations, and emotional and social well-being,^14,15 the present study did not detect any significant impact of transverse maxillary deficiency concerning patient complaints related to swallowing and EAT-10 questionnaire. In the present study, OD symptoms before RME, including having a sensation of a lump in the throat, choking, and the need to clear the throat, ranged between 5%–15%, which decreased to a 5% prevalence after crossbite correction. Prevalence of signs and symptoms related to OD based on patient complaints and physical examination of swallowing function was considered very low before and after RME.

Videofluoroscopy and FEES are the most widely used methods for the diagnosis of OD. Compared to videofluoroscopy, the advantages of FEES are no radiation exposure and regular food use without the need for barium sulfate concentrate. Thus, it allows for repeated swallows per examination. Identification of pharyngeal residue, penetration, and aspiration are the primary goals of FEES. Consequently, FEES has been considered the gold standard for evaluating the pharyngeal phase of swallowing over the past three decades.^16,17

Pharyngeal residue, ie, the material remaining in the pharynx post-swallow, is a sign of swallowing impairment.¹⁸ Although pharyngeal bolus residue poses a risk in laryngeal penetration and aspiration,¹⁸ the entry of a bolus into the airway was not observed in any of the subjects. Residue in the vallecula indicates impaired tongue driving force, insufficient movement of the tongue base against the posterior pharyngeal wall, decreased hyoid and laryngeal elevation, and weak pharyngeal contraction, whereas residue in the pyriform sinus is associated with less pharyngeal constriction, decreased laryngeal elevation, and failure of upper esophageal sphincter relaxation during swallowing.^19,20 The findings of the current study were consistent with a previous study that revealed that vallecula or pyriform sinus residue was influenced by bolus consistency; the severity and frequency of residue were greater with a more viscous bolus.¹⁹ In addition, it was reported that tongue pressure was higher when swallowing a bolus with thicker consistency than when swallowing water.^21,22 Thus, significant residue with yogurt in the present study might also be a function of the high viscosity of yogurt and possibly insufficient tongue pressure.

Swallowing, respiration, mastication, posture, and function of the tongue are interrelated. These interactions should be considered in interpreting the findings of the current study. In agreement with authors who emphasized the main reason for abnormal posture and function of the tongue as deficient nasal respiration,³ mouth breathing or difficulty in breathing through the nose in conjunction with a possible low tongue posture might be responsible for residue before RME as was observed in the present study. However, the residue remained present in the few individuals whose respiratory patterns improved after RME. The residue before and after RME might be multifaceted, and the mechanism behind the residue could not be clearly identified in the present study. Considering that tongue adaptation takes a relatively long time,²³ exercises aimed at increasing tongue pressure against the hard palate can be prescribed to patients after expander removal. This approach may provide decreases in residue findings in the long term. In the present research, records were obtained 1 month after the removal of the RME appliance and prior to bonding the brackets to isolate the effects of RME on OD signs and symptoms more effectively. The current study was preliminary research guiding toward more thorough investigations comprising long-term evaluation, including the pre-RME and post-orthodontic phases.

Suprahyoid-submental muscles contribute to the elevation of the tongue, upward pull of the larynx, and opening of the upper esophageal sphincter.²⁴ Thus, residue in the present study may be related to decreased hyoid elevation and suprahyoid muscle activity since hyoid bone position might be affected by transverse maxillary deficiency and airway obstruction.^25,26 From another perspective, occlusal interferences can arise after expansion. A significant decrease in the activity of anterior temporal and masseter muscles was reported because of occlusal interferences.²⁷ Masticatory muscles, specifically the masseter muscle, are activated at the beginning of the oral phase and aid in hypopharyngeal elevation in the pharyngeal phase.²⁸ A decrease in anterior temporal muscle activity was reported when the tongue was positioned on the floor of the mouth.²⁹ Thus, it is possible that pharyngeal residue may be related to reduced performance of the anterior temporalis and masseter muscles being affected by the occlusal interferences and low tongue posture, causing insufficient tongue pressure or weak bolus propulsion. This, in turn, can result in the continuum of the residue as well as the development of new transient residue after RME.

As a limitation of the current study, measurements of the tongue pressure against the palate and objective evaluation of nasal respiration and tongue posture were not taken into consideration. Additionally, long-term follow-up of subjects treated with RME remains a promising challenge to be addressed in future studies covering the period before RME and after completion of orthodontic treatment to be able to identify possible improvements of the residue.

CONCLUSIONS

• Pharyngeal residue prevalence was greater in patients who had transverse maxillary deficiency with posterior crossbite compared with subjects without discrepancy in the transverse dimension of the maxilla.

• Pharyngeal residue did not appear to cause significant patient complaints.

• In the short-term follow-up, RME had no therapeutic effect on the residue findings.

• It is recommended to inquire about patient complaints particularly if the transverse maxillary deficiency is accompanied by mouth breathing and atypical swallowing due to the possibility of increased severity of dysphagia.