To test the null hypothesis of no significant difference between intraoral pressure characteristics in infants with cleft lip and palate (CLP) with or without presurgical orthopedic (PSO) plates (groups CLP and CLP-PSO), compared with noncleft infants.
Intraoral atmospheric pressure assessments were performed on 17 subjects with preoperative CLP (m/f, 11/6; mean/SD, 4.76/0.92 months) and a matched control group (n = 24; m/f, 15/9; mean/SD, 4.88/0.9 months), for 200 seconds, simultaneously at the vestibulum (vestibular space [VS]) and at the palate (subpalatal space [SPS]), using a prepared pacifier connected to a digital manometer. Areas under the pressure curves (AUC), frequencies, durations, and magnitudes of swallowing peaks and pressure resting plateaus were compared between trial groups and locations (VS, SPS) using a two-factor analysis of variance for repeated measures, Kruskal-Wallis test, and Mann-Whitney U-test (α = .05).
The null hypothesis was rejected: Globally, there were statistically significant differences in intraoral pressure characteristics between groups CLP, CLP-PSO, and control (all P < .01), with significantly higher negative pressures (AUC) in the control subjects compared with those of CLP or CLP-PSO. There were significant effects by the location of pressure recordings (VS, SPS) and their interaction with all treatment groups. Differences between noncleft and CLP subjects were more pronounced in the VS than in the SPS. There was no significant effect by PSO.
PSO does not improve deviated swallowing characteristics during suction in CLP infants.
Intraoral soft tissue factors such as tongue dynamics, swallowing characteristics, and habitual oral posture are known to have an impact on the development of normal occlusion.1,2 They may manifest as various malocclusions such as open bites, crossbites, and narrow maxillae that are known to be triggered or aggravated by deviations from normal nose-breathing patterns, tongue-thrust swallowing, or sucking habits in infants.3,4
Cleft lip and palate (CLP) is one of the most frequent combinations of embryonic developmental disorders with craniofacial expression,5 and its prevalence varies between different populations.6 CLP etiology is multifactorial and is based on both exogenous and endogenous factors.7 Treatment of CLP usually starts at birth with presurgical orthopedics (PSO) such as the use of drink plates or feeding plates. The purpose of PSO is to separate the oral from the nasal cavity, thereby facilitating nose breathing and preventing abnormal tongue positions, such as placing the tongue between the separated palatal segments. Thus, PSO has been indicated as being helpful in controlling the growth direction of the separated maxillary segments, also in narrowing the cleft region presurgery.8 But, while the effect of PSO on language development, nutrition, growth increments, and improving the shape of the nose have been investigated frequently, long-term benefits of PSO therapy are a still a subject of controversy.9–12 Thus, preferences for PSO therapy seem to be based on clinical experience rather than being supported by hard evidence.
Generation of negative intraoral pressures at rest and during suction is considered to be a normal feature in healthy, noncleft newborns, with mean values between 8.4 mbar (SD, 5.8) during interburst periods and 58 mbar (SD, 14.6) during sucking.13 In contrast, CLP children mostly fail to generate a comparable vacuum in the oral cavity, due to lack of separation of the oral and nasal cavities.14 As a consequence of insufficient suction, CLP babies are often underweight compared with noncleft newborns.15
Furthermore, the generation of negative intraoral pressure during swallowing and at rest has been established as a prerequisite for initiating deglutition, and is also seen as the basis of normal dentofacial development with neutral occlusion.1,2,14,16,17 As a normal feature in subjects with neutral permanent dentition, swallowing dynamics include the formation of two separate intraoral spaces, or compartments: The subpalatal space (SPS), the functional space that forms between the back of the tongue and the palatal vault during deglutition and the vestibular space (VS), the functional compartment bordered on the lingual side by the tongue and by the lips and cheeks as the outer limit).17,18 This biofunctional model of the act of physiological deglutition may serve as a basis for screening and analysis of intraoral compartment formation by manometry.17 It may also be helpful in shedding light on whether PSO basically contributes to an improvement in deglutition and normalization of tongue position in CLP newborns, thereby providing for a deeper understanding of the function and benefit of PSO in dentofacial development.
The aim of this study was to clarify the effect of PSO (represented by a drink plate that was adjusted on a regular basis) on the normalization of deglutition in CLP newborns, as parameterized by the formation of intraoral compartments (VS and SPS), compared with noncleft control infants. We tested the null hypothesis of no significant differences between intraoral pressure characteristics assessed in CLP infants, with and without PSO plates (groups CLP and CLP-PSO), and a matched sound, non-CLP control group.
MATERIALS AND METHODS
After obtaining permission from the ethics committee of the University of Göttingen, Germany (3/8/09), and informed consent from the study children’s parents and guardians, we recruited 17 subjects with preoperative CLP (m/f, 11/6; mean age/SD, 4.76/0.92 months; min, 4 months; max, 6 months; bilateral CLP, n = 6; left-/right-sided CLP, n = 10/1) and a matched control group (n = 24; m/f, 15/9; mean age/SD, 4.88/0.9 months; min, 4 months; max, 6 months) between September 1, 2009, and July 31, 2014, from the three CLP centers of the universities of Göttingen, Bonn, and Giessen, Germany. The control subjects were recruited from the Children’s Hospital of Göttingen University. The CLP subjects had been accustomed to PSO therapy by drink plates for at least 3 months. The PSO appliances used here have a double function: Primarily, they serve as drink plates; second, these acrylic plates are either adapted to growth increments on a regular basis by molding or are replaced by new drink plates in an attempt to improve the arch form. The appliances cover the palate and cleft area as widely as possible. The posterior margins are trimmed as much as needed to avoid a pharyngeal reflex.
Inclusion criteria for CLP subjects were unilateral (left- or right-sided) or bilateral, full or partial presurgical CLP. They were excluded for isolated cleft lip or palate, common colds, or general diseases that would restrict nose or mouth breathing. Therefore, of 23 eligible CLP subjects, 6 were excluded for the following reasons: 2 had isolated cleft lip, 3 had isolated cleft palate, and 1 was in a poor general state of health, along with having dyspnea. Inclusion criteria for noncleft control subjects were absence of CLP, common colds, and general diseases.
MATERIALS AND METHODS
Intraoral atmospheric pressure characteristics were recorded simultaneously in the VS and SPS using a prepared pacifier (Nuk, size 1, Mapa GmbH, Zeven, Germany) connected to a digital manometer (GMH3156, with sensor GMSD350MR, resolution of 0.1 mbar rel.; software GSOFT3050; Greisinger, Regenstauf, Germany) via two cannulas (Vasofix-Safety 1.3G18, Braun, Melsungen, Germany) (Figure 1).
The duration of each measurement interval was 200 seconds. The first and last 10 of each recording were discarded in order to analyze deglutition characteristics at rest, following familiarization only. There were singular assessments in the control subjects, while the CLP subjects were measured at first with their PSO plate and subsequently after a break of 2 minutes, without the PSO. All measurements were made by the same operator.
Intraoral pressure characteristics were parameterized by the following features of the pressure curves: The areas under the pressure curves (AUC), frequencies, and median magnitudes of swallowing peaks (mbar) and duration (seconds), frequencies, and median magnitudes (mbar) of pressure resting plateaus >5 seconds. Signal extraction was carried out according to the methods described by Jung et al.19 For each feature, differences between study groups (CLP, CLP-PSO, control), locations (VS, SPS) as well as their interaction, were analyzed by nonparametric, two-factor analysis of variance (ANOVA) for repeated measures.20 Global group comparisons of each location were performed using the Kruskal-Wallis test, followed by pairwise comparisons with the Mann-Whitney U-test. All tests were performed at a significance level of α = 5%, according to the closed testing procedure. Statistical analyses were done with the software R (version 3.0, www.r-project.org) and the R-package MALDIquant for peak detection.
Repeated intraoral pressure measurements have been reported to be subject to variation.17,21–23 In order to characterize the robustness of the distinctive parameters, the variation of measurements was analyzed on the basis of a series of three-time repeated pressure monitoring of three subjects of the control group (Table 1).
For all parameters, two-way ANOVA yielded significant differences between the groups as well as significant interactions between group and location of pressure recording (Table 2). Furthermore, location effects were also significant for all parameters. Because of the significant interactions, analyses were further split by location, yielding statistically significant differences in intraoral pressure characteristics between the three groups, with significantly higher negative pressures by AUC in the control subjects compared with CLP and CLP-PSO (P < .01; Tables 2 and 3).
Areas Under the Pressure Curves
In the SPS, there were significant differences in AUC dimensions between noncleft controls and CLPs, also between controls and CLP-PSO (Table 4), while there was no significant difference between CLP-PSO and CLP (P = .15; Table 4). There was a similar pattern at the VS compared with the SPS (Table 5), although there were much greater differences between noncleft control subjects and CLP or CLP-PSO (Table 3). Accordingly, there was a significant interaction between group and intraoral location of recording (P < .05; Table 2).
Frequencies of Peaks
Median Peak Height
Median peak height was highest in the noncleft control group (Table 3), and the difference in peak height compared with the CLP and CLP-PSO groups was even more pronounced in the VS than in the SPS: There was a significant interaction between group and intraoral location of recording (P < .05; Table 2). There were no significant differences between CLP and CLP-PSO when comparing recordings taken at the SPS or VS (Tables 4 and 5).
Frequencies of Plateaus
In terms of plateau frequencies recorded at the VS, there were significant group-specific differences between CLP-PSO or CLP and noncleft control subjects, but not between SPS recordings (Table 3). Also at the VS, there was no significant difference when comparing CLP-PSO and CLP directly (Table 5).
Median Plateau Height
Likewise, there were significant differences between control subjects and CLP or CLP-PSO that were more pronounced at the VS than at the SPS (Table 3).
Median Plateau Duration
While negative intraoral pressure levels have been described earlier as being a normal feature in newborns,13 the new and striking result of this study goes beyond this knowledge in that there is a formation of two separate compartments (SPS, VS) created by intraoral soft tissue activity during swallowing and suction, especially in healthy, noncleft newborns, but also, to a minor degree, in CLP infants (Table 2). However, in contrast to the pattern of intraoral compartment formation seen in subjects with normal occlusion permanent dentition,17 with higher negative pressures at the SPS than at the vestibulum (VS), this study found an infantile pattern of compartment formation that was inverted (Table 3). Positive pressures were detected only on rare occasions and on a small scale (Table 3; Figure 3; wherein data below 0 indicate positive pressures). This is likely due to the fact that subjects were given a pacifier, which triggers a suction reflex, ie, a generation of negative pressures.
The null hypothesis of no significant differences between intraoral pressure characteristics assessed at the VS and at the SPS between groups CLP, CLP-PSO, and non-CLP control infants was rejected: Noncleft infants were able to generate significantly higher negative pressures in both compartments VS and SPS compared with the matched CLP group, and there was no significant effect of PSO by drink plates on the normalization of deglutition in those subjects (Tables 2–5). Inability to generate negative pressures is believed to be caused by an extraoral/intraoral airway shunt, and the fact that there was no significant difference following incorporation of a drink plate may be simply that those plates do not sufficiently close this irregular airway gap, thereby preventing the generation of negative pressure in the SPS.
However, generation of negative pressures at the palatal vault has been demonstrated to be a prerequisite both for stabilizing the tongue in a physiologic position at rest and for initiating a physiologic sequence of deglutition in adolescents and adults.17,18 However, although we detected patterns of compartment formation in healthy, non-CLP infants—although at lower pressure levels (Tables 2 and 3; Figures 2 and 3)—negative pressures were higher in the vestibulum than in the palatal vault, hinting at a potential development and inversion of patterns of compartment formation following infancy, during childhood.
All CLP subjects included in the study had at least a cleft lip and a cleft palate. That is, also during deglutition and in contrast to noncleft peers (where there is a posterior closure of the oral cavity by the back of the tongue and the soft palate during deglutition), there have been abnormal extra-/intraoral shunts between the oral cavity and the nose in all the CLP subjects.
The first surgical intervention in CLP infants is usually at 6 months. Therefore, study subjects were between 4 and 6months of age, and at the time of recording, they had become accustomed to PSO-therapy by plates for about 3–4 months. Taking into consideration that the subjects did not yet have teeth, differences in deglutition patterns compared with subjects with a developed dentition would have been conceivable.17,18 Nonetheless, a functional compartment formation as parameterized by significantly different pressure recordings (SPS, VS) was observed (Table 2).
Potential Benefits of PSO
The benefits of PSO in CLP therapy are subject to controversy.12 Based on findings by retrospective studies, some authors see advantages of PSO therapy in terms of narrowing the cleft width, thereby facilitating subsequent surgery.8 In contrast, other authors found no alteration of maxillary alveolar ridge shape in CLP subjects treated with PSO compared with a nontreated control group, while surgical correction of cleft lips seemed to have a greater impact on arch dimensions than did PSO.12
PSO is often reasoned by the postulate that the tongue of CLP newborns needs to be trained to maintain a posture considered to be physiological in order to support normal language development: Based on sonography analyses of tongue movements and postoperative articulatory function in CLP children aged about 5 years, Suzuki et al. concluded that those subjects could not create negative pressure in the oral cavity, regardless of previous presence or absence of an orthopedic plate.25 This finding is confirmed by the results of our study (Table 3). However, they also reported an improvement in tongue dynamics during sucking and articulation in subjects treated by PSO, which was not substantiated by our results (Table 2–5). Likewise, other authors found that ingestion is not facilitated or improved by PSO.26 However, the ability to ingest food may vary as a function of cleft palate extension and location.14
CLP morphologies are subject to broad variation. Therefore, generalizability of single studies and comparisons of study findings are impeded, eg, infants with smaller cleft palates were able to generate higher pressures during suction and food intake compared with newborns with larger clefts.14 Hence, CLP variations and locations may constitute sources of deviation in pressure levels. In the present study, morphological differences between malformations were not considered separately during analysis due to scarceness of the subjects. Although a trial sample of 17 subjects with differently expressed CLPs could be collected within a recruitment period of almost 5 years, this factor needs to be considered as potentially affecting pressure levels.
Although great care was taken to ensure that the children were sucking normally, repeated intraoral pressure recordings showed that single pressure curve characteristics were subject to variation (Table 1), as also reported previously by others.17,21–23 Although statistical analyses yielded significant differences between pressure characteristics of the groups, the robustness of pressure parameters needs to be considered in interpreting the data.
There is a limitation in that the CLP subjects were accustomed to PSO therapy, and the pattern of deglutition without the drink plate they were used to might be different from the swallowing pattern that would have developed in the absence of PSO therapy. However, as PSO therapy in CLP subjects is standard in developed countries, further studies using a CLP sample without PSO pretreatment are needed to corroborate the findings of this study.
Both noncleft and CLP infants generated negative intraoral pressures during suction, but pressure levels in the latter were significantly lower.
Two separate functional compartments (SPS and VS) were formed by intraoral soft tissues during swallowing and suction, especially in noncleft newborns, but also, to a minor degree, in CLP infants.
Differences in pressure levels between noncleft and CLP infants were even more pronounced in the vestibulum than in the SPS.
There was no significant effect of PSO by drink plates on the normalization of deglutition in CLP subjects.
In contrast to the pattern of intraoral compartment formation seen in subjects having normally occluded permanent dentition with higher subpalatal than vestibular negative pressures, we found an inverted infantile pattern of compartment formation.
In terms of improving swallowing characteristics and achieving physiological deglutition in CLP infants, the use of drink plates seems questionable.
We thank Dr Nikolaos Daratsianos, Dentistry Center, University of Bonn, Bonn, Germany, for providing us with the opportunity of carrying out measurements during his CLP consultation hour.