INTRODUCTION

Rapid maxillary expansion (RME) is used in subjects with transverse maxillary deficiencies.1–3 Angell first introduced the RME method in 1860 and a great deal of research has been carried out since then. In these studies, it has been noted that RME caused not only dentofacial changes, but also craniofacial structural changes.2–4

One of the most important factors affecting the success of RME is the age of the patient. The most suitable age for applying this method is the pubertal or prepubertal period.5,6 Only limited effects occur in adult patients during RME and post-RME therapy; therefore, in adults, RME should be surgically assisted. With surgery, the circummaxillary rigidity is reduced, periodontal health is preserved, the risk of root resorption diminishes, and satisfactory results with long-term stability can be achieved.7–9

Eysel studied the effect of RME on nasal cavity function in 1886.3,10 He found that, in the post-RME period, various changes occurred in the maxilla and adjacent bones and RME caused an opening of the nasal cavity and reduction in nasal airway resistance. In addition, following expansion an increase was found in the nasal cavity width and in the nasal base adjacent to the midpalatal suture. The maxillary sutures separate the external walls of the nasal cavity laterally resulting in an increase in the intranasal capacity.2,3,5,11,12

The shape and the size of nasal cavity and conchae affect the nasal resistance as does septal deviation, polyps, adenoid tissue, the structure of the mucosa, and the shape of the nostrils.13 To examine the nasal airway and related dentofacial structures, tomography, lateral cephalograms, postero-anterior radiographs, and anterior rhinomanometry methods are used.14–19

The aim of this study was to assess the effects of the normal RME and SARME treatments on the nasopharyngeal area.

MATERIAL AND METHODS

This research was conducted on 15 male patients and 15 female patients. The criteria for selection of both groups for rapid expansion treatment were as follows: a posterior cross bite with evidence of significant skeletal involvement as judged clinically by an experienced orthodontist; no evidence of adenoidal blockage of the nasopharynx; and no previous tonsillar, nasal or adenoidal surgery.

The patients were divided into two groups. The first group (RME group) included 15 patients, eight girls and seven boys, whose mean age was 12.1 ± 1.1 years. The second group (SARME group) included 15 individuals, eight boys and seven girls, with an mean age of 18.4 ± 1.4 years. Table 1 shows the distribution, average ages, and average expansion periods of the subjects. In both groups, a modified bonded acrylic rapid maxillary expansion appliance was used in the expansion process (Figure 1).20

TABLE 1. The Distribution, Average Ages, Expansion Periods and Retention Periods of the Subjects^a

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The RME appliance was cemented in all patients by the same clinician using a glass ionomer cement (Ketac-Cem, Espe Dental AG, Seefeld, Germany). In the RME group, the appliance was activated one-quarter turn twice a day during the expansion period. In the SARME group, a nonsurgical RME was attempted but, if after the fist week the maxillary median suture was not separated, surgical assistance was instituted. The same surgeon carried out all surgery. A Le Fort I osteotomy without a down fracture was used as described by Epker and Fish.21 A bilateral buccal corticotomy was undertaken from the apertura piriformis towards the pterygoid fissures in an attempt to break the resistance of the maxillary tuberosity and the ties between the maxilla and zygomatic bones. No surgical operation in the median palatal suture was done. Beginning on the seventh postoperative day, the appliance was activated one-quarter turn twice a day during the expansion period.21 All cross bites were overcorrected so that the palatal cusps of the upper molars were riding up on the buccal cusps of the lowers. When the required expansion was achieved, the RME appliance was removed and the screw locked in position with cold cure acrylic and used as a retainer for three months. All baseline records were repeated after three months. Fixed appliance treatment was started soon after the retention period.

In postero-anterior cephalometric radiographs, two planes were used and the nasal cavity width and maxillary width were taken (Figure 2). Nasopharyngeal area was established by using four planes on the lateral cephalometric radiographs. The nasopharyngeal area has been limited with the palatal, sphenoid, pterygomaxillary, and anterior axis planes (Figure 3).22

• Palatal Plane (PaL): the plane from the ANS to PNS points.

• Sphenoid Plane (SpL): the tangent drawn at the greater wing of the sphenoid bone.

• Pterygomaxillary plane (PtL): the plane formed by drawing a perpendicular line to the Palatal Plane from PNS point.

• Anterior Axis Plane (aaL): the plane formed by drawing a perpendicular line to the palatal plane from aa point (anterior tubercule of the atlas).

• Q angle: the angle between the sphenoid and palatal planes.

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The nasopharyngeal and respiratory areas on were measured separately on lateral cephalograms with a “Placom” type digital planimeter in mm². The respiratory area (RA)/nasopharyngeal area(NA) ratio of Linder-Aronson was also calculated for each patient (Figures 4 and 5).23

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RESULTS

The measurement error of Dahlberg, using the formula √Σd²/2n, was established for each measurement and the findings were observed to vary between 0.074 and 0.542. These findings are not significant enough to affect the credibility of the research. The findings of the research are presented in Tables 2, 3, and 4.

TABLE 2. Comparisons of Pre- and Post-Treatment Values Between and Within the Groups^a

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The findings related to the nasopharyngeal area revealed that the RA/NA ratio decreased at the level of P < .001 in both groups (nonsurgical RME and SARME) (Tables 2 and 3).

The differences between pretreatment and post-treatment measurements in these groups were not statistically significant (P > .05) (Table 4). The Q angle in all assessments was not statistically significant (P > .05) (Tables 2, 3, and 4). When the frontal cephalometric films in both groups were evaluated, a significant increase in the width of the nasal cavity and the maxilla was seen P < .001.

DISCUSSION

When an RME is used in the separation of the midpalatal suture, some expansion occurs between the maxillary bones and in the lower part of the nostrils. Therefore, individuals having some problems in the frontal and lower parts of their nasal structure have had much more relaxed respiration following RME.3,12,26–29

Through the use of RME, there was an increase in nasal cavity dimensions, a decrease in nasal obstruction, and a relief in the respiration canals. However, in the treatment of asthma (allergic rhinitis patients), an RME is said to be not efficient enough and, therefore, is only a supplementary treatment in solving the problem.3,26,28

Lateral cephalometric radiographs have been used for examining dentofacial structures, nasal airway, and related areas.17–19 Although there is no clear connection between the oropharyngeal and hypopharyngeal areas, it is claimed that there is a direct relation between the two-dimensional cephalometric film measurement of tongue, palate, and nasopharyngeal areas and their three-dimensional computed tomography measurements. However, orthodontists do not advise three-dimensional computerized tomography as the patient is exposed to high doses of radiation and it causes a waste of time and money.30 The measurement of the nasopharyngeal area was made with a planimeter similar to that of many other studies.22,31–33 In this study, the dentofacial structure of the patients treated with RME and SARME have been examined. In both groups, Placom-type digital planimeter lateral and postero-anterior cephalometric films were used.

Handelman and Osborne22 maintained that the Q angle between the sphenoid plane and the palatal plane that they used in determining the nasopharyngeal area did not change from the age of one year until the age of 18 years. Our study also shows the stability of the Q angle in both groups (P > .05), indicating the credibility of the planes in determining the nasopharyngeal area.

Planimetric measurements taken on lateral cephalograms showed that respiration areas in both groups enlarged and the RA/NA ratio increased (P < .001). These results suggest that nasal respiration passages are opened and the respiration process relieved. In both groups, RA/NA ratio increased 12%. In addition, when normal RME was compared to SARME, no statistically significant difference was observed between these groups (P > .05).

Warren et al28 found that nasal area increased 45% after the RME and 55% following the SARME. The expansion became particularly effective in increasing nasal valve size and the area width. Researchers suggested that an RME would not be useful by itself in cases with turbine hypertrophy, nasal polyps, enormous adenoids, or septal deviations.

In our study, the nasal cavity width and maxillary width, measured from postero-anterior cephalograms, increased statistically in both groups (P < .001). Moreover, the nasal cavity width increased at the level of 3.47 mm in the normal RME group and 2.93 mm in the SARME group. These findings are greater than Krebs34 (1.4 mm), Wertz12 (1.9 mm) and the average nasal cavity width (2.087 mm) found by Da Silva Filho, et al.35

Haas36, however, claimed that this measure varied between 2 to 4.5 mm. The reasons for the difference is in the age variation of the subjects, differences in how the appliance was used in the expansion and the variance of expansion amounts applied on the patients. Our findings agree with previous research showing an increase in maxillary width and nasal cavity width with the use of RME.23,26,27

Linder-Aronson and Aschan37 claimed that measurements taken after one year showed no change in the nasal resistance, which came to normal levels after the RME. Hershey et al27 came to the conclusion that no changes occurred in the new capacity of nasal resistance after a three-year period.

In our study, RME with or without surgical aid was effective in patients with nasal respiration problems and maxillary transversal deficiency. However, while planning the treatment, the localization of etiologic factors should be considered.