Material and methods

This prospective study was carried out after institutional approval from the Ethics Committee of Gulhane Military Medical Academy in Ankara, Turkey.

Eighty-eight patients (45 male, 43 female; mean age, 17.54 ± 4.66 years) participated in this study, and all signed informed consent forms. The participants were divided into 4 groups according to their skeletal structures ( Table I ). The skeletal classifications were made by the evaluation of the sagittal components of the jaws, based on the SNA, SNB, and ANB angles, and N vertical-A and N vertical-Pg linear measurements (distance between A point and nasion perpendicular [the line beginning from nasion point and perpendicular to Frankfurt horizontal line [the line between porion and orbita points]] and distance between pogonion point and nasion perpendicular) of the lateral cephalograms. Twenty-three Class III patients (13 male, 10 female; mean age, 17.09 ± 5.77 years) with mandibular prognathism were included in the first group. In the second group, there were 21 Class III patients (9 male, 12 female; mean age, 15.58 ± 3.45 years) with maxillary retrognathism. The third group comprised 22 Class III patients (9 male, 12 female; mean age, 19.21 ± 3.87 years) with both maxillary retrognathism and mandibular prognathism. Finally, 22 subjects (10 male, 12 female; mean age, 18.26 ± 5.22 years) with skeletal Class I malocclusion composed the control group.

All patients were examined with a 1.5-T super conducting magnetic resonance scanner with a quad H coil and version 9 software (New Intera Nova, Philips Medical Systems, Best, The Netherlands). Real-time balanced turbo field echo images (shortest TR/TE:2.1/1.09 ms) were taken with a 50° flip angle in the midsagittal plane, 10 mm thickness, 350 × 350 mm field of view dimensions, and 96 × 96 matrix width during the patient’s water swallowing. A hundred dynamic scans were captured in 11 seconds.

The images were obtained while the subjects were swallowing 10 mL of water that was taken with a syringe just before imaging. For each patient, images matching the following 3 stages were determined by 3 specialists and printed out on a radiograph: stage 1: loss of contact of the dorsal tongue with the soft palate ( Fig 1 ); stage 2: passage of the bolus head across the posterior or inferior margin of the ramus of the mandible ( Fig 2 ); and stage 3: passage of the bolus head through the opening of the esophagus ( Fig 3 ).

Stage 1: loss of contact between the tongue’s dorsum and the soft palate.

Stage 2: passage of the bolus head across the posterior or inferior margin of the ramus of the mandible.

Stage 3: passage of the bolus head through the opening of the esophagus.

Linear measurements defined by Fujiki et al were made on these radiographs for each stage by 1 author (E.A.) to prevent interobserver variability. The reference points and planes are shown in Table II . Since AM-E and AM-PM are distances on tje palatal mucosa, they were curved lines. A ligature wire was used for the measurement of these parameters. MM-MT, MM-MS, PM-PT, PM-PS, C1-D, C1-Me, and PS-I are straight distances. P’-Ti is the shortest distance from a line crossing at a right angle to the NF plane through PNS to Ti ( Fig 4 ).

Linear measurements by MRI: ( a ), AM-E/AM-PM, the anterior portion of the tongue’s dorsum, contact of tongue and palate; ( b ), MM-MT/MM-MS, the midportion of the tongue’s dorsum; ( c ), PM-PT/PM-PS, the posterior portion of the tongue’s dorsum; ( d ), C1-D/C1-Me, root of the tongue; ( e ), P’-Ti/PS-I, the tongue’s tip, and AM-E AM-PM are distances on the palatal mucosa. MM-MT, MM-MS, PM-PT, PM-PS, C1-D, C1-Me, and PS-I are straight distances. P’-Ti is shortest distance from a line crossing at a right angle to the NF plane through PNS to Ti

(from Fujiki et al ).

The points and measurements of 24 patients were reevaluated 1 month later, and the method error was determined by Dahlberg’s formula, ME = √∑d2/2n
∑ d 2 / 2 n
, where n is the number of subjects and d is the difference between the 2 measurements of a pair. The method error did not exceed 0.153 mm. All statistical analyses of the groups were performed with the Statistical Package for Social Sciences for Windows software (version 13, SPSS, Chicago, Ill). The variables were examined visually and with the Shapiro-Wilks analysis for normal distribution. Table I shows the mean ages and various cephalometric values used to define the groups.

All descriptive statistics are given as means and standard deviations ( Table III ). Analysis of variance (ANOVA) for repeated measurements was used to evaluate the measurements obtained from the 3 stages, the 4 groups, and interactions of the 3 stages with the 4 groups. In case of differences, the Bonferroni post-hoc test was used to determine the causes of the differences between the stages or the groups. P ≤0.05 was accepted as the level of significant difference.

Results

In the within-group comparison of the stages ( Table IV ), the degree of contact between the anterior portion of the tongue and palate (AM-E/AM-PM) ( Fig 5 ) was significantly greater at stage 2 than at stage 1 ( P <0.05) in the mandibular protrusion group (group 1). The increase between stages 2 and 3 or 1 and 3 was not statistically significant ( P >0.05). This parameter also increased in the other groups, but it was not significant.

Table IV

Comparison of intragroup differences between stages

	Group	Stages		Mean difference	SE	P	Significance
Anterior portion of tongue	Mandibular prognathism	1	2	−0.058	0.020	0.026	*
			3	−0.063	0.026	0.063	NS
		2	3	−0.006	0.029	1.000	NS
	Maxillary retrognathism	1	2	−0.051	0.023	0.109	NS
			3	−0.049	0.026	0.224	NS
		2	3	0.002	0.029	1.000	NS
	Bimaxillary	1	2	−0.039	0.033	0.731	NS
			3	−0.046	0.026	0.253	NS
		2	3	−0.007	0.028	1.000	NS
	Control	1	2	−0.031	0.019	0.359	NS
			3	−0.005	0.018	1.000	NS
		2	3	0.026	0.018	0.532	NS
Middle portion of tongue	Mandibular prognathism	1	2	0.106	0.071	0.439	NS
			3	0.184	0.050	0.004	†
		2	3	0.078	0.060	0.615	NS
	Maxillary retrognathism	1	2	0.140	0.061	0.095	NS
			3	0.184	0.047	0.003	†
		2	3	0.044	0.052	1.000	NS
	Bimaxillary	1	2	0.151	0.040	0.003	†
			3	0.184	0.057	0.012	*
		2	3	0.033	0.040	1.000	NS
	Control	1	2	−0.056	0.052	0.882	NS
			3	0.204	0.046	0.001	‡
		2	3	0.260	0.058	0.001	‡
Posterior portion of tongue	Mandibular prognathism	1	2	0.017	0.055	1.000	NS
			3	0.106	0.053	0.183	NS
		2	3	0.089	0.049	0.255	NS
	Maxillary retrognathism	1	2	0.034	0.056	1.000	NS
			3	0.067	0.069	1.000	NS
		2	3	0.033	0.047	1.000	NS
	Bimaxillary	1	2	0.043	0.058	1.000	NS
			3	0.125	0.057	0.124	NS
		2	3	0.081	0.047	0.295	NS
	Control	1	2	0.069	0.024	0.031	*
			3	−0.074	0.037	0.170	NS
		2	3	−0.142	0.034	0.001	‡
Root of tongue	Mandibular prognathism	1	2	−0.028	0.015	0.230	NS
			3	−0.032	0.017	0.233	NS
		2	3	−0.003	0.017	1.000	NS
	Maxillary retrognathism	1	2	−0.028	0.014	0.212	NS
			3	−0.045	0.013	0.007	†
		2	3	−0.017	0.014	0.641	NS
	Bimaxillary	1	2	−0.025	0.013	0.217	NS
			3	−0.030	0.016	0.210	NS
		2	3	−0.005	0.019	1.000	NS
	Control	1	2	0.029	0.018	0.348	NS
			3	−0.008	0.020	1.000	NS
		2	3	−0.037	0.018	0.153	NS
Tip of tongue	Mandibular prognathism	1	2	0.062	0.016	0.002	†
			3	0.015	0.014	0.843	NS
		2	3	−0.047	0.016	0.023	*
	Maxillary retrognathism	1	2	0.078	0.035	0.108	NS
			3	0.004	0.013	1.000	NS
		2	3	−0.074	0.036	0.165	NS
	Bimaxillary	1	2	0.082	0.036	0.096	NS
			3	0.026	0.033	1.000	NS
		2	3	−0.056	0.037	0.429	NS
	Control	1	2	0.095	0.035	0.038	*
			3	0.041	0.045	1.000	NS
		2	3	−0.054	0.045	0.728	NS

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