Tongue pressure production and orofacial muscle activities during swallowing are related to palatal morphology in individuals with normal occlusion

Figures & data

Table 1. Details of the participants.

	Mean ± S.D
Overjet [mm]	2.53 ± 0.55
Overbite [mm]	2.30 ± 0.68
Dental arch width [mm]
Maxillary	44.05 ± 3.55
Mandibular	35.73 ± 2.03
Dental arch length [mm]
Maxillary	38.33 ± 1.85
Mandibular	34.25 ± 1.82
Arch length discrepancy [mm]
Maxillary	−0.18 ± 0.61
Mandibular	−0.48 ± 0.64

Figure 1. (A) occlusal view of the sensor sheet attached to the palate, (B) positioning of surface electrodes over the orofacial muscles.

Ch, channel; Ch1, anterior-median part; Ch2, mid-median part; Ch3, posterior-median part; Ch4, left posterior-lateral part; Ch5, right posterior-lateral part; a, masseter muscle; b, orbicularis oris muscle; c, mentalis muscle; d, suprahyoid muscles; e, infrahyoid muscles.

Figure 2. A typical example of tongue pressure waveforms, raw and rectified waveforms of orofacial muscle activities during swallowing.

▲, the peak time of suprahyoid muscle activity was set as time 0 s (black arrowhead); ●, onset; ○, offset; the line from onset to offset shows duration; ▽, maximum magnitude of tongue pressure.

Figure 3. Assessment of palatal morphology on the plaster model of the maxilla.

M and M’: the deepest point of the palatal margin of the right and left first molars; Measurement plane: a coronal section perpendicular to the reference plane (incisive papilla and M and M’ planes) and containing the line M–M’; palatal width: the line M–M’; palatal depth at points 1–9, the distance between the palate and the line perpendicular to the palatal width drawn from each of the 10 equally divided points along the palatal width, in ascending order from the right side, as point 1, point 2 … point 9. Palatal depth ratio was defined as the ratio of palatal depth at each point to the palatal depth at point 5. The palate was then divided into three areas: right lateral area, from M to palatal depth at point 3; central area, from palatal depth at point 3 to point 7; and left lateral area, from palatal depth at point 7 to M.

Figure 4. (A) time sequences for tongue pressure and orofacial muscle activities, (B) duration of tongue pressure and orofacial muscle activities, (C) maximum magnitude of tongue pressure.

Ch, channel; Ch1–5, see in Figure 1(A). *p < 0.05; n.s., Not significant.

Figure 5. Palatal depth.

M, M’, Points 1–9, Right and left lateral areas and Central area, see in Figure 3.

Table 2. Analysis of palatal morphology.

Palatal width [mm]		Palatal depth [mm]	Palatal depth ratio [%]
Median (IQR)		Median (IQR)
35.75 (34.10–38.23)	Point 1	4.67 (4.02–5.27)	38 (30–42)
	Point 2	9.02 (8.75–9.71)	72 (66–79)
	Point 3	12.20 (11.32–13.15)	97 (91–102)
	Point 4	12.62 (11.62–13.83)	100 (98–104)
	Point 5	12.60 (11.39–13.57)	100
	Point 6	12.52 (11.19–13.62)	99 (97–100)
	Point 7	12.01 (10.65–12.89)	94 (88–96)
	Point 8	9.18 (7.67–10.30)	72 (62–75)
	Point 9	4.74 (3.72–5.71)	37 (31–43)

Table 3. Relationships between the maximum magnitude of tongue pressure and palatal morphology.

Maximum magnitude of tongue pressure	Palatal width		Palatal depth
			Point 1		Point 2		Point 3		Point 4		Point 5		Point 6		Point 7		Point 8		Point 9
Ch1	0.45	*	0.23		0.25		0.36		0.31		0.22		0.14		0.16		0.15		0.15
Ch2	0.39		−0.06		−0.04		0.20		0.18		0.03		0.01		0.00		−0.03		−0.11
Ch3	0.40		0.16		0.00		−0.29		−0.33		−0.36		−0.37		−0.27		−0.13		−0.02
Ch4	0.37		0.25		0.19		−0.05		−0.13		−0.19		−0.20		−0.15		−0.12		−0.03
Ch5	0.51	*	0.09		0.10		−0.02		−0.07		−0.14		−0.14		−0.15		−0.14		−0.12

Values show correlation coefficients. *p < 0.05, **p < 0.01.

Table 4. Relationships of the onset of tongue pressure production and orofacial muscle activities with palatal morphology.

Onset	Palatal width		Palatal depth
			Point 1		Point 2		Point 3		Point 4		Point 5		Point 6		Point 7		Point 8		Point 9
Ch1	−0.16		−0.15		−0.18		−0.36		−0.29		−0.18		−0.17		−0.26		−0.18		−0.13
Ch2	−0.39		−0.14		−0.29		−0.57	**	−0.37		−0.20		−0.18		−0.27		−0.20		−0.10
Ch3	−0.38		−0.08		−0.25		−0.56	*	−0.34		−0.16		−0.13		−0.23		−0.17		−0.07
Ch4	−0.24		0.01		0.06		−0.03		0.06		0.19		0.21		0.11		0.09		0.03
Ch5	−0.24		−0.03		0.03		−0.11		−0.03		0.12		0.17		0.11		0.12		0.07
Masseter muscle	0.14		0.03		−0.14		−0.30		−0.34		−0.33		−0.35		−0.31		−0.18		0.05
Orbicularis oris muscle	0.13		−0.03		−0.15		−0.35		−0.44		−0.52	*	−0.51	*	−0.47	*	−0.40		−0.19
Mentalis muscle	−0.20		−0.11		−0.15		−0.45	*	−0.40		−0.45		−0.48	*	−0.51	*	−0.44		−0.28
Suprahyoid muscles	0.05		0.02		0.04		0.00		−0.10		−0.14		−0.15		−0.14		−0.14		−0.07
Infrahyoid muscles	−0.43		−0.05		−0.23		−0.37		−0.27		−0.17		−0.17		−0.12		−0.03		0.11

Values show correlation coefficients. *p < 0.05, **p < 0.01.

Table 5. Relationships of the offset of tongue pressure production and orofacial muscle activities with palatal morphology.

Offset	Palatal width		Palatal depth
			Point 1		Point 2		Point 3		Point 4		Point 5		Point 6		Point 7		Point 8		Point 9
Ch1	−0.16		0.11		−0.11		−0.40		−0.31		−0.20		−0.20		−0.26		−0.25		−0.15
Ch2	−0.26		−0.02		−0.22		−0.34		−0.23		−0.15		−0.14		−0.17		−0.20		−0.17
Ch3	−0.14		−0.24		−0.41		−0.65	**	−0.61	**	−0.51	*	−0.46	*	−0.39		−0.27		−0.19
Ch4	−0.20		−0.04		−0.04		−0.35		−0.33		−0.27		−0.21		−0.29		−0.35		−0.43
Ch5	−0.19		0.05		0.00		−0.34		−0.28		−0.21		−0.14		−0.21		−0.25		−0.29
Masseter muscle	−0.30		0.15		0.04		−0.02		0.02		0.13		0.06		0.12		0.20		0.32
Orbicularis oris muscle	0.01		0.04		−0.03		0.10		0.28		0.33		0.27		0.13		0.12		0.20
Mentalis muscle	0.05		0.09		0.13		0.14		0.25		0.29		0.28		0.23		0.19		0.10
Suprahyoid muscles	−0.12		0.13		0.11		−0.16		−0.25		−0.18		−0.14		−0.22		−0.27		−0.26
Infrahyoid muscles	−0.17		0.08		0.06		−0.22		−0.27		−0.18		−0.14		−0.24		−0.30		−0.31

Values show correlation coefficients. *p < 0.05, **p < 0.01.

Table 6. Relationships of the duration of tongue pressure production and orofacial muscle activities with palatal morphology.

Duration	Palatal width		Palatal depth
			Point 1		Point 2		Point 3		Point 4		Point 5		Point 6		Point 7		Point 8		Point 9
Ch1	0.00		0.25		0.18		−0.01		0.04		0.00		0.03		0.03		−0.08		−0.08
Ch2	0.11		0.10		0.06		0.18		0.12		0.04		0.04		0.08		0.00		−0.05
Ch3	0.13		−0.17		−0.22		−0.23		−0.34		−0.37		−0.34		−0.21		−0.14		−0.13
Ch4	0.05		−0.04		−0.08		−0.25		−0.31		−0.37		−0.35		−0.32		−0.35		−0.36
Ch5	0.06		0.06		−0.03		−0.19		−0.21		−0.28		−0.28		−0.29		−0.33		−0.31
Masseter muscle	−0.07		0.11		0.12		0.28		0.35		0.39		0.37		0.31		0.30		0.26
Orbicularis oris muscle	−0.07		0.05		0.07		0.30		0.50	*	0.58	**	0.54	*	0.40		0.35		0.28
Mentalis muscle	0.11		0.11		0.17		0.40		0.46	*	0.52	*	0.54	*	0.52	*	0.43		0.25
Suprahyoid muscles	−0.14		0.08		0.05		−0.12		−0.08		0.00		0.04		−0.03		−0.07		−0.12
Infrahyoid muscles	0.27		0.11		0.26		0.18		0.05		0.03		0.05		−0.07		−0.19		−0.33

Values show correlation coefficients. *p < 0.05, **p < 0.01.