International Journal of Pediatric Otorhinolaryngology (2006) 70, 27—34
Acoustic rhinometric measurements in children undergoing rapid maxillary expansion Giacomo Ceroni Compadretti a,*, Ignazio Tasca a, Giulio Alessandri-Bonetti c, Stefano Peri b, Ada D’Addario b a
Department of Otorhinolaryngology, Imola Hospital, 40024 Viale Oriani 1, Castel San Pietro Terme (BO), Italy b Department of Orthodontics, Imola Hospital, Italy c Department of Orthodontics, University of Bologna, Italy Received 26 January 2005; accepted 4 May 2005
KEYWORDS Rapid maxillary expansion; Acoustic rhinometry; Cephalometry; Children
Summary Objective: To evaluate geometric changes of nasal cavities in children undergoing rapid maxillary expansion and to assess the effect of this procedure on nasal airway size by means of acoustic rhinometry. Method: We recruited 14 mouth-breather children (mean age 8.2 years) presenting constricted maxillary arches and scheduled for rapid maxillary expansion in the orthodontics department of our hospital. Clinical history did not reveal any allergic diseases and ENT examination was completely normal with a well-aligned nasal septum. Nasal measurements were obtained using acoustic rhinometry, which was performed before the expansion treatment and after 1-year follow-up. A posteroanterior radiograph of the skull was also performed in all patients for cephalometric analysis before and 3 months after the treatment. Results: We observed a satisfactory increment in the transverse dimension of the maxilla in all patients but one who manifested a relapse after 4 months from the treatment and required a second procedure. Similarly, acoustic rhinometric measurements and cephalometric tracings showed a statistically significant increase respectively in decongested total nasal volumes ( p = 0.047) and in binasal cavity width ( p = 0.001). However, only eightchildrenswitched theirrespirationfrom oral tonasalbreathing mode. Conclusions: Rapid maxillary expansion is an effective method for increasing the width of narrow maxillary vault and it is also associated with a significant increment in nasal volumes and in the transverse diameter of the maxilla. With regard to breathing posture, the role of this procedure still remains debatable. To date this is the first study aimed at analysing the effects of rapid maxillary expansion on nasal dimensions by means of acoustic rhinometry. # 2005 Elsevier Ireland Ltd. All rights reserved.
* Corresponding author. Tel.: +39 051 6955111; fax: +39 051 6955229. E-mail address: [email protected]
(G. Ceroni Compadretti). 0165-5876/$ — see front matter # 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ijporl.2005.05.004
1. Introduction Rapid maxillary expansion (RME) is an orthodontic technique, which is commonly used to widen the maxilla and consists of a distraction procedure after non-surgical midpalatal suture opening. Distraction osteogenesis techniques are based on a mechanical process that results in a gradual bone lengthening and it has become, currently, the standard of care for treatment of many types of congenital midfacial deformities . It is generally agreed that RME is a reliable method for correcting maxillary narrowing resulting in the orthodontic abnormality of cross-bite and for providing more space for alignment of crowded teeth. In contrast to these consistent dental findings, there has not been agreement on the effect of this procedure in nasal parameters. While some authors enthusiastically supported RME as a means of reducing or eliminating a mouth-breathing posture, others remain sceptical of the influence of RME on the nasal airway. In particular, Gray  reported that RME produces a change of over 80% from mouth to nose breathing and gives considerable improvement in colds and respiratory infections, nasal allergy and asthma. Hershey et al. , in his series of 17 patients treated by RME, found an average reduction in nasal resistance of 45% and concluded that RME is an effective method for increasing the width of narrow maxillary arches but also reduces nasal resistances from levels associated with mouth breathing to levels compatible with normal nasal respiration. Other authors have also evaluated some additional advantages associated with this procedure. Taspinar et al.  reported the effects of RME on conductive hearing loss, and found hearing improvements in 74% of patients. Contrarily, Hartgerink et al.  maintained that RME was not a predictable means of decreasing nasal resistance. Until now, the effects of RME on nasal airway has been investigated only recording the variation in nasal flows and pressures by means of rhinomanometry. The availability of a reliable and objective technique to assess the geometry of nasal cavities such as AR  and the renewed interest in the effect of breathing on skeleton facial growth [7,8] stimulated the present study. AR is based on the fact that changes in the cross-sectional area of the nose will alter the acoustic impedance. When an acoustic pulse is introduced into the nasal airway, the changes of intensity, phase, and time delay of the reflected sound energy are altered according to the location and degree of the nasal airway obstruction. Nasal cavity volumes can be estimated by combining the measures cross-sectional areas . AR is a non-invasive, accurate, and reproducible technique, which has demonstrated to be helpful in assessing changes in nasal cavity geometry following procedures such as
G. Ceroni Compadretti et al.
septoplasty, or adenotonsillectomy [10,11]. Besides these clinical applications, AR is also a valid tool for research purposes. With regards to open mouth posture in children, Gross et al. , in a sample of 348 children undergoing the rhinometric tests, recorded smaller cross-sectional areas in those children exhibiting open-mouth posture during 80% or more of the observation intervals. The aim of the present investigation is to examine objectively the effect of RME on mouth breathing posture and any changes in nasal dimensions by means of AR. Data were also compared with cephalometric measurements. To date, this rhinometric study is the first in the international literature.
2. Materials and methods Between February 2002 and September 2002, we recruited 14 mouth-breather children, eight males and six females with a mean age of 8.2 years (range: 7—10 years) presenting constricted maxillary arches and scheduled for rapid maxillary expansion in the Orthodontic Department of our Hospital.
2.1. ENT examinations ENT examinations consisted of anterior rhinoscopy, nasal endoscopy, otoscopy and acoustic rhinometry (AR) (wideband noise, continuously transmitted rhinometer, Rhin 2000, S.R. Electronics). Endoscopy was performed using a flexible fiberoptic nasopharyngoscope, which was passed along the floor of the decongested nasal passage into the nasopharynx under topical anaesthesia. According to the guidelines of the Standardisation Committee on Acoustic Rhinometry , rhinometric tests were always performed in standard conditions of temperature and humidity with background noise not-exceeding 60 dB, and always by the same operator after a period of acclimatization of 15 min. Each test was carried out in basic conditions and after decongestion. The rhinometer used a 58 cm wavetube, which was connected to the nostril by the pediatric contoured anatomical nose adapter with a cut-off angle of 608. Rhinometric measurements were obtained before the expansion treatment and at 1-year follow-up (Fig. 1). A photographic documentation of the palate, of the teeth and of the face was also performed in all cases before and 1 year after the orthodontic treatment.
2.2. Orthodontic treatment The palatal expansion was obtained using a Hyraxtype rapid expander, which was cemented to the
Acoustic rhinometric measurements in children
Fig. 1 Rhinometric tracing of: (A) a patient scheduled for rapid maxillary expansion, before and after decongestion test and (B) the same patient 1 year after the expansion treatment, clearly showing the increase in TMCA both in basal and decongested condition.
first molars and first premolars. The midline screw was activated by one quarter turn (0.25 mm) in the morning and one quarter turn in the evening per day until the upper molar palatal cusps were in contact with the lower molar buccal cusps. After the activation period (10—12 days), the appliance was used as a retainer for three months, then removed, and the necessary orthodontic treatment completed.
2.3. Radiologic evaluation Postero-anterior radiographs of the skull were also performed in all patients before and 3 months after the expansion treatment (Fig. 2). Cephalometric data were obtained through a computed analysis (Orteam-Orthocad 9, Software) according to Ricketts et al. . Nasal cavity width and intermax-
illary distance were the parameters taken into consideration.
2.4. Statistical analysis All data were presented in terms of mean and standard deviation. One-way ANOVA was used to investigate whether there was a difference between males and females in measurement means and their variations induced by treatment. The paired t-test was performed to check for differences in mean values before and after treatment. The Wilcoxon non-parametric test was performed to see if there was an appreciable increase (or decrease) between pre-treatment and post-treatment values. The regression test with Pearson’s correlation was used to assess connections between age and measure-
G. Ceroni Compadretti et al.
Fig. 2 (A and B) Posterior—anterior radiographs of the skull in a patient, before and 3 months after rapid maxillary expansion, respectively. (C and D) The corresponding computed tracings for cephalometric analysis, before and 3 months after the treatment.
ments or their variations induced by treatment and connections between the effect of treatment among the various measures. All analyses and graphs were realized using SPSS 11.0 for Windows.
3. Results All patients had a mouth-breathing posture. Fiberoptic nasopharyngoscopy showed a bilateral nasal permeability in all children. Only a small enlargement of adenoids, inferior turbinates, and a poster-
ior non-obstructive septum deviation were detected in four patients, two patients, and in one patient, respectively. Any ear diseases were present at the moment of observation. Clinical history did not reveal any allergic diseases or facial trauma. All the subjects were in mixed dentition, and from the occlusal point of view presented a dental cross-bite (eight unilateral, six bilateral) due to a narrow maxilla. During the follow-up, a satisfactory and stable increment in the transverse dimension of the maxilla was observed in all patients but one, who manifested a relapse after 4 months from the treatment and required a second procedure. Only 8 of the 14 treated children switched their respiration from oral to nasal breathing mode after the treatment. Sex, adenoid or turbinate hypertrophy, posterior septum deformity, unilateral or bilateral dental cross-bite did not influence measures or response to treatment (one-way ANOVA not significant). Measures and response to treatment did not depend on the sample age (regression test with Pearson’s correlation not significant). Table 1 shows the increase in MCA in basal conditions and decongestion measured on the right side, on the left side, and total value. The increase was extremely variable with rather modest mean values. The difference between pre-treatment and post-treatment values both with regards to mean values (paired t-test) and the presence/absence of increment (Wilcoxon test) was not statistically significant. Table 2 shows the increase in volumes in basal conditions and decongestion measured on the right,
Table 1 Acoustic rhinometric values of MCA in basal and decongested conditions measured on the right side, on the left side, and total Increment after the treatment (cm2)
Right MCA in basal condition Left MCA in basal condition TMCA in basal condition Right MCA in decongested condition Left MCA in decongested condition TMCA in decongested condition
0.04 0.04 0.08 0.05 0.07 0.12
0.16 0.27 0.38 0.19 0.27 0.39
ns ns ns ns ns ns
ns ns ns ns ns ns
Table 2 Acoustic rhinometric values of volume in basal and decongested conditions measured on the right side, on the left side, and total Increment after the treatment (cm3)
Right volume in basal condition Left volume in basal condition Total volume in basal condition Right volume in decongested condition Left volume in decongested condition Total volume in decongested condition
0.131 0.225 0.356 0.752 0.575 1.327
0.973 1.170 1.852 1.423 1.221 2.359
ns ns ns ns ns 0.047
ns ns ns 0.046 0.05 0.05
Acoustic rhinometric measurements in children
Table 3 Cephalometric measurements of binasal cavity width and intermaxillary distance according to Ricketts Increment after the treatment (mm)
Binasal cavity width Intermaxillary distance
on the left, and total. In basal conditions the increase was extremely variable with rather modest mean values. The difference between pre-treatment and post-treatment values both with regards to mean values (paired t-test) and the presence/ absence of increment (Wilcoxon test) was not statistically significant. In decongestion conditions, despite the persistence of a great variability in behaviour, the increase was appreciable. Statistical analysis on right and left values showed a significant increase in volume (Wilcoxon test p = 0.046 right side; p = 0.05 left side), albeit not significant in terms of mean value of this increase (paired t-test not significant). The difference between pre-treatment and post-treatment total volume, instead, was significant both for mean values (increase of 1.237 2.359 cm3; paired t-test p = 0.047) and for the presence/absence of the increase (Wilcoxon test p = 0.05). Table 3 shows the increase of binasal cavity width and intermaxillary distance. Intermaxillary distance had an extremely variable increase, and the difference between pre-treatment and post-treatment values both with regards to mean values (paired t-test) and the presence/absence of increment (Wilcoxon test) was not statistically significant. Binasal cavity width had an appreciable mean increase
(2.2 2.1) cm. The difference between pre-treatment and post-treatment was significant both for mean values (paired t-test p = 0.001) and for presence/absence of increase (Wilcoxon test p = 0.002).
4. Discussion There has been long-standing controversy over the efficacy of rapid maxillary expansion to relieve nasal obstruction and improve respiration. Numerous previous studies have attempted to investigate this topic by means of rhinomanometry. In particular, White et al.  found a statistically significant average reduction in nasal airway resistance of 48.7% and affirmed that such reduction was highly correlated to the nasal resistance level prior to RME. Contrarily, Timms , using a posterior rhinomanometric technique, recorded an average reduction of nasal resistances of 36.2% after palatal expansion, but he did not found significant correlation between resistance lowering and the delivered expansions. To date this is the first trial, in the international literature, aimed at analysing the effects of RME on nasal volumes by means of acoustic rhinometry.
Analysis of total volumes in decongested condition before and after the expansion treatment.
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Analysis of cephalometric values of binasal cavity width pre and post-treatment.
There is another rhinometric study by Wriedt et al. , who, using a surgically assisted rapid maxillary expansion in a sample of 10 adult patients, recorded a significant increment in nasal volumes. This is in agreement with the results obtained in our pediatric group of patients. In fact, Graph 1, concerning the total volume in decongestion conditions, shows that the post-treat-
ment values are globally higher. This supports the global efficacy of individual response to orthodontic treatment. Graph 2 concerning binasal cavity width shows that the post-treatment values, besides being globally higher, are also less variable, since half of the sample had values between 26 and 28.3 mm, whereas before treatment half of the sample ranged
Comparative analysis of binasal cavity width and decongested TMCA.
Acoustic rhinometric measurements in children
between 23 and 26.5 mm. That suggests a certain uniformity of response to treatment that also supports its efficacy. Finally, Graph 3 shows that with the increase in binasal cavity width TMCA measured in decongestion conditions also increases (regression test p = 0.01 with Pearson’s correlation coefficient R = 0.637). This is coherent with the aim of the treatment. The fact that MCA increase was not statistically significant might be due to the small size of the sample studied and the technical limitations of AR. In fact, precisely due to such limitations, Djupesland and Rotnes  demonstrated that AR is not able to detect correctly constrictions and expansions shorter than 3—4 mm. It follows that single crosssectional areas like MCA become more sensitive to error than volumes based on the integrations of several cross-sectional areas. The observation that only 8 children of the 14 mouth-breathers switched their respiration from oral to nasal respiration mode means that also other factors correlate with breathing posture. Warren et al.  states that nasal respiration is subject to developmental considerations, both physical and behavioural. Clearly, nasal dimensions influence the ability to breathe through the nose. However, the evidence that a percentage of children with adequate nasal airways are predominantly oral breathers also indicates that learning influences mode of respiration. Since RME has little effect on nasal airflow, even Wertz  could not advocate this treatment for purely respiratory reasons, while Hartgerink et al.  in a group of 38 patients treated by RME and compared with a control group not receiving the expansion concluded that RME is not a predictable means of decreasing nasal resistance due to the high individual response variability. Thus, these findings suggest that maxillary expansion for airway purpose alone is not justified. Finally, we believe that flexible nasopharyngoscopy should be performed routinely in all children with upper respiratory symptoms because it allows obstructive conditions of the nose, nasopharynx, and larynx to be identified and also provides a dynamic assessment of the palate and laryngeal function [21—23]. In our study, this examination has demonstrated to be a safe, well tolerated procedure and made it possible to assess nasal permeability in most children, revealing only minor abnormalities in a few, but without any significant influence on the results of the statistical analysis. This preliminary report has shown successfully that RME correlates with nasal dimensions of healthy children. Once demonstrated objectively that this procedure is really effective in widening
nasal cavities, future research applications would be the evaluation of the effects of RME on selected patients affected by nasal septum dislocations, ear diseases, OSA syndrome.
Acknowledgement I wish to acknowledge the precious contribution of Elettra Pignotti in the statistical analysis of the results.
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