Effects of Volumetric Alterations of the Tongue Base on Craniofacial Growth in the Adult Minipig

ABSTRACT

Craniofacial growth determines the proper functional coordination of skeletal and soft tissue structures. Alterations related to size, volume, and other parameters may impair expected growth and function. Thus, this study aimed to analyze the effects of volume‐reduced and volume‐enlarged tongue base on craniofacial skeletal growth. Three groups of Yucatan minipigs included control, 7–8‐month‐old (n = 8), half each sex; experimental volume‐reduction group treated by coblation (n = 6), with concurrent left masseter volume‐reduction as well for later myoregeneration analysis; and experimental volume‐enlargement group (n = 6), via diet‐induced obesity. Both experimental groups were 7–9‐month‐old same‐sex sibling pairs, half each sex. After cardiac perfusion fixation, the tongue and masseter were dissected, followed by soft tissue removal from each skull. Over 90 anatomic landmarks yielded 51 linear distances, and weights/sizes/volumes of the tongues and masseters were measured. All measured variables in controls were normalized for age prior to statistical analysis. One‐way ANOVA with Bonferroni post hoc and Pearson's correlations were used. The reduction group showed significantly smaller craniofacial skeletal and dental arch than controls. For instance, the midfacial width (p = 0.042), maxillary inter‐canine width (p = 0.001), and mandibular ramus height (p = 0.035) were significantly reduced. The enlargement group also showed significantly decreased distances between sides compared to controls (i.e., inter‐canine width p = 0.001, inter‐premolar width p = 0.005, and inter‐molar width p = 0.007). Strongest associations were found between the whole tongue and structures in the base of the skull of the reduction group, and between the tongue base volume and mandibular structures such as the mandibular ramus height (r = −0.804, p = 0.016). In conclusion, volumetric alterations of the tongue base either enlargement or reduction significantly increase and decrease craniofacial growth. These findings may help clinicians to understand the potential mechanisms of disease in respiration and swallowing disorders induced by changes in soft tissue affecting the craniofacial skeleton.

Craniofacial growth is a continuous process that constantly adapts to environmental, physiological, and genetic factors. All of these factors induce alterations in soft tissues that directly impact the size and rate of growth of skeletal structures. In the present study, two conditions of volume alterations of the tongue base were induced in a Yucatán minipig model (a) with volume‐enlargement via obesity and volume‐reduction via surgical coblation (b). Linear measurements were taken in all regions of the skulls (c) and correlated with soft tissues harvested from each animal. As a result:

• Measurements were higher in controls compared to the volume‐reduction and volume‐enlargement experimental groups.

• Growth of orofacial skeletal structures was smaller in the volume‐reduction group compared to the control and volume‐enlargement groups.

• Growth of the mandible structures in the base of the skull was smaller in the volume‐enlargement group compared to controls.

1. Introduction

Craniofacial growth is defined by the continuous adaptations of soft tissues and bony structures from childhood to adulthood (Manlove et al. 2020). This process can be affected by environmental and genetic factors altering the rate of growth and skeletal maturity stages. For instance, alterations in postnatal growth and malocclusion usually cause misalignments and morphological changes that tend to impair proper functioning mainly in respiration, chewing, and swallowing (Knigge et al. 2022). Skeletal muscle and other soft tissues are major components of craniofacial growth as their function and dynamic proportions induce bone remodeling, adaptation, and compensatory mechanisms (Knigge et al. 2022; Manlove et al. 2020). According to the Functional Matrix Theory, external factors and soft tissues induce compensatory responses in the skeletal structures that modify growth over time (Moss 1997). Thus, craniofacial growth is a lifetime dynamic process susceptible to alterations of soft tissue and constant functional adaptations.

Postnatally, multiple clinical conditions such as temporomandibular joint (TMJ) dysfunction, trauma, and metabolic or hormonal disorders, may induce maladaptation and functional problems, that is, bruxism inducing malocclusion and axial misalignment (Joshi et al. 2014; Knigge et al. 2022). These conditions tend to deteriorate soft and bone tissues and therefore, the normal craniofacial growth.

Obesity is related to volumetric enlargements of the tongue base and other oropharyngeal structures whereas controlled ablation is one of the surgical techniques for tongue volumetric reduction (Bahgat et al. 2020; Baker et al. 2025). A recent publication on cephalometric analysis in obese patients with obstructive sleep apnea reported lengthening of the mandibular ramus and displacement of the hyoid bone associated with a large tongue volume (Xia et al. 2025). Our group previously reported decreased craniofacial parameters such as the anterior dental arch width in young Yucatan minipigs with surgical reduction of the tongue body (Liu et al. 2008). These results suggest that retarded craniofacial skeletal growth is potentially related to functional impairment, such as alterations in jaw movements.

Theoretically, using volumetric changes of the tongue base and masseter muscles as the primary comparison axis is justified by (1) Skeletal growth of the mandible and maxilla induced by the tongue volume and the volume of masticatory muscles. (2) Volumetric changes may impact surrounding skeletal structures. (3) Compensatory mechanisms to recover balance during mastication, swallowing, breathing, and other functions. Additionally, skeletal maturity in the Yucatan minipig, the model used in the present study, is reported to start at about 4.4 months given by histological analysis of their reproductive structures (Howroyd et al. 2016). Thus, the present study aimed to analyze craniofacial skeletal changes related to volumetric enlargement and reduction of the tongue base in young adult minipigs. These are clinically relevant models of disease due to their impacts on the airway to ensure patency and the relationship in the craniofacial morphology in young individuals (Kang et al. 2025).

We hypothesized that the volumetric alterations of the tongue base, either enlargement or reduction, may lead to the modifications of craniofacial skeletal growth, in particular in mandible, dental arches, and oropharyngeal region, in young animals. The outcomes of the present study would help clinicians better understand the potential impacts of congenital or acquired volumetric changes of the tongue based on craniofacial skeletal growth.

2. Materials and Methods

2.1. Animals

Upon arrival, all Yucatan minipigs of 7–9 month old were acclimated for 5–7 days, housed one per pen with pen enrichment provided by the Facility, received water ad libitum, and a 12‐h day/night cycle. Initially, eight minipigs, half each sex, were assigned to control (n = 8). Then, six same‐sex sibling pairs, half each sex, were assigned to each experimental group, one for tongue base volume reduction (n = 6), and one for tongue base volume enlargement (n = 6).

Minipigs in the control group were of normal weight (BMI < 37) with no intervention related to the tongue base volume, were fed with standard chow pellet twice a day, and they were euthanized 3 weeks after arrival. These minipigs did not receive any treatment or longitudinal interventions. In the tongue base reduction group, the minipigs were also normal weight, fed similarly to controls, and received partial surgical tongue base ablation with 4%–8% of the total tongue base volume reduction (1.20 ± 0.48 cm³) (Chen et al. 2026; Geradze et al. 2026). The tongue base volume enlargement group was fed ad libitum high‐calorie pellets for 10+ weeks to reach obesity (BMI > 51) prior to arrival and continued being overfed for the experimental period to maintain the obese condition. The minipigs in these experimental groups were euthanized 7 weeks after arrival as longitudinal recordings during respiration, chewing, and swallowing were taken at weeks 1, 3, and 5 after tongue base reduction.

Therefore, all experiments were done in two parts. First, control minipigs were analyzed for 3 weeks then euthanized. Second, experimental minipigs were studied for 7 weeks followed by euthanasia and fixation by perfusion. All procedures were approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Washington.

2.2. Ultrasound Crystal Implantation and Experimental Recordings

The tongue base dynamics and muscle activity during respiration and mastication of all minipigs were analyzed by implanted 2 mm round shape ultrasound SONO crystals (Sonometrics Co., Canada) arranged forming a cube, and implanted electromyography microelectrodes (California Fine Wires Co. CA) in the tongue, jaw, palatal, pharyngeal and hyoid muscles as previously described (Rosero Salazar et al. 2024; Rosero Salazar et al. 2025). Recordings for the control group were taken at baseline and then terminal session 1 week later. Recordings for experimental groups were taken at baseline and weeks 1, 3, and 5 after tongue base reduction surgery. These results will be reported elsewhere.

2.3. Tongue Base Reduction Surgery and Terminal Procedures

Six normal‐weighted minipigs underwent partial surgical volumetric reduction of the tongue base by controlled ablation (coblation) using radiofrequency within the cubic‐shaped area circumscribed by the implanted crystals (Figure 1). This surgery was performed 2 days after baseline recordings and it was used to remove 1.20 ± 0.48 cm³ (4%–8%) of the original tongue base volume (Chen et al. 2026; Geradze et al. 2026). Similarly, the left masseter was partially ablated excising 2%–4% of the muscle mass closer to the mandibular angle. This muscle was selected due to its large muscle mass and low amount of fat accumulation observed in our previous publication (Rosero Salazar et al. 2025). Also, its different embryological origin from the tongue base makes it useful for wound healing analysis and myoregeneration comparisons. The results of these comparisons will be reported elsewhere.

Figure 1.

Ultrasound crystal implantation and tongue base reduction surgery. (A) Tongue Base regions indicated by oblique dotted lines. Eight ultrasound SONO crystals were implanted dorsally (1–4) and ventrally (5–8) in a cubic arrangement. The ablated tongue base tissue was located within the area circumscribe by the crystals (diamond). Adapted from (Herring et al. 2025). (B) Example of one sibling pair female minipigs showing obesity (left) and normal‐weight (right). Scale: 10 cm. (C) Samples of tongue bases dissected from the same minipigs at week 5 after surgical reduction of the tongue base. The enlarged tongue base (left) shows intact circumvallate papilla (circle) whereas the reduced tongue base (right) shows scar tissue and absent papilla (circle). Scale: 1 cm.

On the terminal day 5 weeks after surgery, the body weight, length (from the tip of the snout to the base of the tail), and neck circumference at the location of the thyroid cartilage were measured. After the terminal procedures both experimental groups were euthanized using pentobarbital sodium 15 mL IV (Euthasol, Virbac, USA).

2.4. Postmortem Processing of Minipig Heads

A perfusion needle was inserted into the left ventricle, and the upper body was flushed sequentially with phosphate‐buffered saline (PBS 1X) and fixative concentrate (Prefer, Anatech, Durham, NC) mixed with ethanol 95% and distilled water at 1:1:3 concentrations. The head was then removed to continue immersion fixation for 10–15 days and transferred to 70% ethanol for preservation until dissections of the tongues and masseter muscles.

After removing all implanted ultrasound crystals, the tongue was dissected from the hyoid bone and the mandible. The entire tongue was measured for volume, length, thickness, width, and weight and then segmented into the base, body, and blade (Figure 1) and measured individually. The tongue base is the region between the posterior border of the tongue and the circumvallate papillae. The tongue body follows until the frenulum, and the tongue blade is the region between the frenulum and the tip of the tongue (Dotiwala and Samra 2025).

Additionally, bilateral masseter muscles were dissected and detached from the mandible and zygomatic bones, and the same parameters were measured. Volumes were determined by water displacement, and mass weights were recorded using a precision scale. All dissected components were stored in 70% ethanol for later histological processing which results will be reported elsewhere.

The soft tissues of the heads were cleaned by placing each head into a box for dermestid beetle colony for several months. Maceration followed by soaking the head in soap and detergent water at room temperature to soften residual flesh and periosteum. Last, the remaining attached tissues were manually removed using scalpels, forceps, and brushes. All skulls were rinsed in running tap water, immersed in ethanol 95% for 24 h, and let completely dry.

2.5. Biometric Measurements of Craniofacial Bones, Tongue, and Masseters

As shown in Figure 2 a total of 99 points were marked over the cranio‐maxillary and mandibular skeletal surfaces. Based on these marked points, 51 distances between the two given points were measured using compasses, digital caliper, and digital protractor for mandibular angles. All measurements were performed by adjusting a compass to the exact length between two points to measure it using a digital caliper for accuracy. These distances presented all aspects of the skull including anterior‐superior, posterior, lateral, and base of the skull. The mandible also presented superior, inferior, and lateral aspects.

Figure 2.

Anatomic landmarks of craniofacial base. A—Ventral view 1/1′: Styloid processes; 2/2′: Tympanic bullae; 3/3′: Medial pterygoid plates; 4: Posterior nasal spine; 5/5′: 2nd upper molars; 6/6′: 1st molars; 7/7′: 4th premolars; 8/8’: 3rd premolars; 9/9′: Canines; 10/10′: Incisive foramens. 11/11′: Hypoglossal foramens. 12: Pharyngeal condyle. 13: Suture Vomer/Sphenoidal bone. 14/14′: External Edge Sphenoid Bone. 15/15′: Incisive suture. B—Lateral view: 1: Tip of zygomatic process arch; 2: Lacrimal bone‐posterior; 3: Lacrimal bone‐anterior; 4: Posterior suture of the maxilla; 5: First upper molar′ 6: Anterior suture of the maxilla; junction with the pre‐maxilla; 7: Canine; 8: Nostril of premaxilla. C—Caudal view: 1: Tip of occipital bone; 2/2′: External acoustic meatus. D—Dorsal view: 1: Lambda; 2: Bregma; 3: Nasion; 4: Anterior border of the nasal bone. E: 1: Mandibular symphysis ‐ ante‐ventral; 2: Mandibular symphysis ‐ post‐ventral; 3‐3’: Width of mandibular body. F: C‐C’: Degree of crossbite. G: 1: 1st premolar; 2: Mandibular body; 3: Gonion; 4: Mandibular angle (D°); 5: top of condyle. H: 1/1’: Condyles; 2/2’: 2nd lower molars; 3: Mandibular symphysis ‐ post‐dorsal; 4: Mandibular symphysis ‐ ante‐dorsal; 5: Canines. Linear measurements between landmarks are classified in Table 2. Scale: 1.0 cm.

2.6. Statistical Analysis

To test inter‐reliability of the measurements 16 distances between different marked points were randomly selected and measured by one investigator (AL) and later by the second investigator (AS). The intraclass correlation coefficient was 0.989 (p = 0.000). For intra‐reliability test, randomly selected parameters were measured by the first investigator (AL) with a 10‐day interval. The error examined by Dahlberg's formula was 0.15 mm (Dahlberg 1940) and the intraclass correlation coefficient was 0.996 (p = 0.000).

Because of 5 weeks age difference between the control and the two experimental groups, data was normalized by the percentage age difference applied to control minipigs to the age of the experimental groups meaning 5 weeks older (1.3 ± 0.8 months) using the formula:

$$\text{Age}\text{Difference}(\%)=\left(\frac{\text{Experimental}\text{Minipig}\text{Age}‐\text{Control}\text{Minipig}\text{Age}}{\text{Control}\text{Minipig}\text{Age}}\right)\times 100$$

These adjustments were applied to all control craniofacial biometrics and soft tissue measurements at 0.186 increase. Therefore, all measurements from soft and hard tissues were obtained and recorded first, and the percentage difference of the age parameter was added to the measurements of the controls.

Minipigs show a rapid growth from birth to 5 months old reaching a plateau and a slower growth afterwards (Kim et al. 2015; Kohn et al. 2007). Specifically, the Yucatan minipig grows at a slower rate than other minipigs and reaches this plateau with a less non‐linear growth from 4 to 5 months on (Kim et al. 2015).

Normality tests showed p > 0.05 of the entire set of measurements indicating normal distribution of all data. Therefore, One‐way ANOVA followed by post‐hoc Bonferroni test were applied to detect significant differences between groups.

Additionally, Pearson's R correlations were determined between bone measurements and measurements of weights, volumes, and dimensions of the tongue and masseters. A significant level of p < 0.05 was set for all comparisons. All statistical analyses were performed using SPSS version 19.0 (IBM).

3. Results

BMI for controls was 31.8 ± 2.8 with 7.0 months old at terminal with no significant increase from baseline. For the volume‐reduction group BMI was 33.0 ± 3.1 at baseline and 38.0 ± 3.1 Kg at terminal with 8.3 months old at terminal. The BMI for the volume‐enlargement group was 56.0 ± 6.6 at baseline and 60.0 ± 3.7 at terminal.

The tongue and masseter muscle biometrics showed a larger tongue base thickness of the control group compared to reduction and enlargement groups. The whole tongue width was significantly higher in the reduction compared to control and enlargement (p < 0.05) groups. The weights and volumes of the tongues and bilateral masseters were consistently higher in the enlargement group whereas thickness was greater in controls and width in the reduction groups (Table 1).

Table 1.

Summary of body sizes for each experimental group and timepoint. Volume (mL), Weight (g), Length (mm), Width (mm), Thickness (mm). One‐way ANOVA (p‐value ≤ 0.05).

Structure	Measurement	Group
		Control	Reduction	Enlargement	F (p‐value)
	Volume	128.7 ± 16.0	111.7 ± 12.9	131.2 ± 15.2
Whole tongue	Length	15.9 ± 0.9	15.4 ± 0.9	15.9 ± 1.3
	Width	4.0 ± 0.3a	4.7 ± 0.3a	4.3 ± 0.4	4.9 (0.021)
	Thickness	4.0 ± 0.3a , b	3.1 ± 0.2a	3.4 ± 0.4b	14.5 (0.000)
	Weight	95.6 ± 2.7b	107.7 ± 10.7	122.7 ± 16.8b	10.5 (0.001)
Tongue base	Volume	33.9 ± 10.7	33.2 ± 4.0	44.0 ± 4.0
	Length	4.2 ± 0.4	4.1 ± 0.3	4.3 ± 0.5
	Width	3.5 ± 0.4	3.9 ± 0.3	3.7 ± 0.4
	Thickness	4.1 ± 0.3a , b	3.0 ± 0.2a , c	3.5 ± 0.3b , c	20.9 (0.000)
	Weight	34.2 ± 3.5	35.5 ± 4.3	38.8 ± 10.7
Tongue body	Volume	57.7 ± 5.1	54.5 ± 8.2	66.0 ± 9.9
	Length	7.1 ± 0.6	6.5 ± 0.7	6.3 ± 0.7
	Width	3.4 ± 0.7a , b	4.2 ± 0.6a , b	4.4 ± 0.3	6.9 (0.006)
	Thickness	4.1 ± 0.5a , b	3.3 ± 0.2a , b	3.5 ± 0.3	9.9 (0.001)
	Weight	54.7 ± 5.3	53.9 ± 7.4	60.4 ± 6.1
Tongue blade	Volume	12.2 ± 1.2b	15.5 ± 5.0	19.2 ± 6.1b	4.3 (0.030)
	Length	4.9 ± 0.6	5.2 ± 0.8	5.4 ± 0.6
	Width	4.6 ± 0.4	4.3 ± 0.5	4.4 ± 0.2
	Thickness	2.0 ± 0.3	2.0 ± 0.2	2.0 ± 0.6
	Weight	11.7 ± 1.3a , b	16.8 ± 4.3a	18.7 ± 2.9b	10.5 (0.001)
Right masseter	Volume	43.6 ± 8.6	41.3 ± 10.8	46.0 ± 5.7
	Length	6.2 ± 0.8	6.1 ± 0.8	6.4 ± 0.8
	Width	6.6 ± 0.6	6.6 ± 3.7	6.5 ± 0.9
	Thickness	1.7 ± 0.4	1.7 ± 0.5	1.7 ± 0.3
	Weight	36.0 ± 13.7	34.3 ± 12.6	37.8 ± 15.8
Left masseter	Volume	62.9 ± 23.2	49.0 ± 19.1	54.0 ± 10.7
	Length	7.7 ± 0.7	6.7 ± 0.8	7.5 ± 1.1
	Width	7.1 ± 0.4	7.1 ± 0.6	7.3 ± 0.6
	Thickness	1.5 ± 0.4	1.8 ± 0.3	1.7 ± 0.2
	Weight	45.5 ± 17.2	49.1 ± 6.1	56.4 ± 11.2

^a Significant differences between control and reduction groups.

^bSignificant differences between control and enlargement groups.

^c Significant differences between reduction and enlargement groups.

Linear measurements were mostly higher in controls compared with experimental groups. One of them is the midfacial width significantly higher in control compared to the reduction groups (p = 0.035). Similarly, significant changes were detected in the ventral view of the palatal length, and upper dental arch widths between canines, second premolar, and molars, all these values were significantly lower in the reduction compared to the control group (p < 0.05). These measurements in the enlargement group were also smaller compared to controls, significantly in mandibular dental arch (p < 0.05). Interestingly, the oropharyngeal length was not significantly different between groups but the inter‐hypoglossal canal width smaller in the reduction group compared to controls (p < 0.05) (Table 2).

Table 2.

Measurements (millimeters) between marked points and comparisons between groups. Mean ± SD. One‐way ANOVA (p‐value ≤ 0.05).

View	Landmark	Parameter	Control	Reduction	Enlargement	F (p‐value)
Skull dorsal view	Nasion—anterior nasal aperture	Length nasal bone	85.8 ± 8.9	84.6 ± 12.4	77.1 ± 10.5
	Bregma—nasion	Length frontal bone	73.5 ± 4.7	68.0 ± 5.5	66.9 ± 6.2
	Bregma—lambda	Length parietal bone	31.4 ± 2.1	28.6 ± 2.8	29.1 ± 2.0
	Nasal aperture—skull posterior edge	Skull length	197.0 ± 13.3	185.9 ± 14.1	181.6 ± 11.6
	Right—left zygomatic bones superior edge	Midfacial width	92.8 ± 5.5a	85.8 ± 4.2a	87.9 ± 4.0	4.1 (0.035)
	Right—left premaxillary suture	Premaxillary width	28.9 ± 2.2	24.9 ± 3.4	25.4 ± 2.6
	Right—left lateral edge of the anterior nasal aperture	Width pyriform aperture	32.5 ± 2.5	3.1 ± 1.8	30.7 ± 1.4
	Right—left posterior edge zygomatic bone	Posterior width	125.8 ± 4.3	113.8 ± 14.1	121.3 ± 5.0
	Right—left medial edge orbits	Inter—orbital width	66.9 ± 4.1	64.6 ± 3.0	67.2 ± 2.8
Skull caudal	Right—left external acoustic meatus	Inter—meatal width	94.7 ± 5.2	93.6 ± 7.8	97.0 ± 4.6
Skull lateral	Maxilla superior edge— alveolar ridge	Height maxilla	51.9 ± 2.4	48.9 ± 3.1	51.5 ± 3.4
	Skull posterior Edge – Gonion	Height of skull	172.6 ± 8.4	162.7 ± 7.6	167.8 ± 5.3
	Anterior–posterior lacrimal bone	Length lacrimal bone	13.4 ± 1.5	13.4 ± 2.6	13.8 ± 1.8
	Canine – First molar		48.2 ± 3.7a , b	42.1 ± 3.9a	38.5 ± 1.8b	14.9 (0.000)
	Incisors upper—lower jaw	Crossbite	13.42 ± 1.8	12.9 ± 5.9	14.1 ± 3.0
Skull ventral view	Incisive suture—incisors	Premaxillary palatal length	30.7 ± 3.5a	26.3 ± 2.4a	27.7 ± 1.7	4.57 (0.026)
	Incisive suture— transverse palatal suture	Maxillary palatal length	58.9 ± 5.8	59.3 ± 5.0	54.6 ± 3.5
	Transverse palatal suture—posterior nasal spine	Palatine bone length	28.2 ± 2.7	26.1 ± 2.9	26.0 ± 4.0
	Posterior nasal spine— suture vomer/sphenoid bones	Nasopharyngeal length	35.0 ± 3.1	33.0 ± 3.8	33.3 ± 2.2
	Pharyngeal condyle— suture vomer/sphenoid bones	Oropharyngeal length	30.4 ± 2.9	29.3 ± 2.9	30.1 ± 1.8
	Right—left canines	Inter—canine Width	40.1 ± 1.7a	34.1 ± 1.5a , c	38.8 ± 2.0c	21.7 (0.000)
	Right—left second premolar	Inter—premolar width	37.9 ± 1.9a	34.4 ± 1.5a	36.6 ± 1.6	7.1 (0.006)
	Right—left first molar	Inter—molar width (anterior)	58.6 ± 2.1a , b	51.6 ± 1.4a	54.4 ± 1.9b	25.5 (0.000)
	Right—left second molar	Inter—molar width (posterior)	45.5 ± 1.5a	42.1 1.4a	43.6 ± 2.3	6.5 (0.008)
	Right—left medial pterygoid plates	Choana width	27.0 ± 2.2	26.2 ± 2.7	25.6 ± 2.4
	Right—left styloid processes	Inter—styloid Width	54.5 ± 4.1	51.2 ± 2.9	52.5 ± 3.7
	Right—left tympanic bulla	Inter—bulla width	42.3 ± 2.4	39.2 ± 1.6	40.1 ± 2.8
	Right—left external edge sphenoid bone	Width sphenoid bone	55.0 ± 3.1	50.8 ± 2.9	51.7 ± 2.7
	Right—left hypoglossal canal	Inter—hypoglossal canal width	27.1 ± 1.0a	24.5 ± 1.4a	26.4 ± 2.2	4.8 (0.021)
	Medial pterygoid plates—suture vomer/sphenoid bones	Nasopharyngeal width	29.1 ± 1.9	28.9 ± 3.1	28.1 ± 1.9
	Right—left incisive foramina	Inter—incisive foramina width	13.2 ± 1.4	11.8 ± 1.1	14.4 ± 0.5
Mandible lateral	Condylar process—Gonion	Height ramus	92.4 ± 4.3a	86.1 ± 1.2a	91.6 ± 4.6	4.4 (0.028)
	First premolar—base edge	Height body	41.6 ± 3.4	38.2 ± 3.2	39.8 ± 4.0
	Condylar process— symphysis menti	Length mandibular body	181.4 ± 8.5a	167.4 ± 10.3a	171.2 ± 7.9	4.7 (0.024)
	Gonion—symphysis menti	Length base edge	117.2 ± 8.1	108.9 ± 7.4	108.0 ± 5.5
	Symphysis menti—first premolar		47.9 ± 4.5	45.9 ± 2.2	47.5 ± 4.4
	Left mandibular angle (degrees)		96.5 ± 2.8	93.8 ± 3.8	98.9 ± 4.6
	Right mandibular angle (degrees)		97.0 ± 3.3	93.0 ± 3.1	99.0 ± 5.4
Mandible dorsal view	Right—left condylar processes	Intercondylar distance	112.5 ± 6.5	105.5 ± 7.7	109.1 ± 3.5
	Right—left canines	Inter‐canine Width	37.6 ± 1.7a , b	33.4 ± 1.8a	34.5 ± 1.2b	13.2 (0.000)
	Right—left first premolars	Inter—first premolar width	43.2 ± 3.2a , b	37.0 ± 1.7a	39.6 ± 1.3b	7.5 (0.005)
	Right—left second molars	Inter—molar width (posterior)	46.2 ± 1.6a , b	42.7 ± 2.0a	42.7 ± 2.2b	8.4 (0.003)
Mandible ventral view	Superior—inferior symphysis menti	Height symphysis menti	46.5 ± 2.9	42.6 ± 5.0	47.8 ± 5.7
	Right – Left gonion	Bigonial width	108.0 ± 6.4	100.4 ± 5.5	99.9 ± 10.4

^a Significant differences between control and reduction groups.

^bSignificant differences between control and enlargement groups.

^c Significant differences between reduction and enlargement groups.

Other measurements in the mandible showed larger ramus and inter‐canine,‐premolar, and ‐molar widths in controls than those of both experimental groups (p < 0.05).

Last, Table 3 summarizes the significantly positive and negative correlations between craniofacial bone structures with the whole tongue, tongue base, and left masseter muscle. Most correlation coefficients above 0.8 and p ≤ 0.04 were detected in the reduction group. Overall, the control group showed a few significant correlations between the whole tongue with the midfacial width, and the mandibular body with the tongue base and left masseter widths. The reduction group showed significant correlations between the whole tongue length with the palatal length, and whole tongue width with dental arch measurements. The enlarged group showed a significant correlation between the whole tongue width and the length of the mandibular body.

Table 3.

Correlations of significant bone measurements with tongue and masseter above 0.7 (bold) for all groups. Pearson's coefficient (p‐value ≤ 0.05).

Measurement	Soft tissue	Control	Reduction	Enlargement
Premaxillary palatal length (Skull)	Whole tongue length	0.39 (0.33)	0.82 (0.040)	0.17 (0.74)
Midfacial width	Whole tongue width	−0.77 (0.023)	0.58 (0.21)	0.14 (0.78)
Inter‐canine width	Whole tongue width	−0.37 (0.35)	0.89 (0.016)	−0.42 (0.41)
Inter‐canine width	Tongue base width	−0.01 (0.98)	−0.91 (0.012)	0.05 (0.92)
Inter‐premolar width	Tongue base width	0.19 (0.63)	−0.70 (0.11)	0.26 (0.61)
Inter‐molar width anterior	Whole tongue width	−0.54 (0.17)	0.86 (0.030)	−0.24 (0.65)
Inter‐molar width posterior	Tongue base width	−0.16 (0.70)	−0.74 (0.089)	0.04 (0.94)
Canine‐first molar	Tongue base width	0.31 (0.45)	−0.91 (0.012)	0.43 (0.39)
Height ramus (mandible)	Left masseter length	−0.35 (0.39)	0.83 (0.039)	0.11 (0.84)
Height ramus	Tongue base thickness	−0.04 (0.92)	0.72 (0.10)	0.09 (0.86)
Height ramus	Left masseter width	0.56 (0.15)	−0.46 (0.35)	0.87 (0.25)
Length mandibular body	Tongue base weight	0.13 (0.76)	−0.84 (0.034)	−0.15 (0.78)
Length mandibular body	Left masseter width	−0.78 (0.021)	0.42 (0.41)	0.66 (0.15)
Length mandibular body	Whole tongue width	−0.010 (0.98)	0.38 (0.45)	−0.97 (0.001)
Inter‐canine width	Tongue base width	−0.74 (0.033)	−0.16 (0.75)	−0.40 (0.43)
Inter‐molar width	Whole tongue volume	0.19 (0.65)	0.72 (0.11)	−0.17 (0.74)

4. Discussion

The present study analyzed the effects of induced volume changes in the soft tissue, that is, tongue base, and their relations with the craniofacial remodeling in a young adult minipig model. These findings are aligned with a previous study in the same minipig model at a younger age (Liu et al. 2008). Those younger minipigs showed slower growth of skeletal craniofacial structures in the volume‐reduced tongue compared with the sham‐group. This is also consistent with the Functional Matrix Theory (Moss 1997) interestingly showing in this case adaptations that causes smaller and perhaps weaker skeletal structures with age due to less functional tissue present in the tongue base.

Consistently, the volume reduction of the tongue base strongly decreases the midfacial width even though the ablated volume was less than 10% of the total tongue base volume. This percentage is close to what is reduced in patients with obstructive sleep apnea (OSA) and related disorders (Lu et al. 2022).

The opposite occurred in volume enlargement with a strong increase of the posterior width including inter‐meatal, inter‐styloid, oropharyngeal, and inter‐bulla widths. Obesity also induces enlargement of surrounding oropharyngeal structures such as the soft palate and the pharyngeal wall. Therefore, a compensation mechanism must be a stronger and wider bone arrangement to support tissue adaptations and proper function.

In early stages of obesity there seem to be stimulation of myofiber formation to preserve the muscle mass in an anabolic response to weight‐bearing activities (Morgan et al. 2020). Thus, if the craniofacial muscle mass i.e. tongue base and soft palate adapt and increase, then similar responses must be generated from skeletal craniofacial structures to support this type of soft tissue remodeling. However, it is likely that at later or morbid stages of obesity musculoskeletal functions gradually exhaust and catabolic events take place inducing a condition called sarcopenic obesity previously reported (Chan et al. 2024; Morgan et al. 2020). These kind of events are observed in OSA patients showing low bone mineral density, decreased muscle strength, reduced muscle mass, and higher risks of breathing shortage and swallowing disorders (Chan et al. 2024; Liao et al. 2025). Some measurements in the obese minipigs of the present study showed decreasing compared to controls indicating potential early signs of catabolic effects of the craniofacial skeleton that may also negatively affect function. This is also one of the reasons for what data normalization was applied to the measurements of soft and hard tissues of the control minipigs. This method in the analysis led us to detect true statistical differences either increased or decreased growth in both groups in relation to the intact tongue base. Interestingly, the reduction of the left masseter less than 5% seems to have minor effects on the overall craniofacial growth than those effects caused by changes in the tongue base volume. A previous study showed large muscle mass with minimum fat deposition in the masseter muscle of normal‐weighted minipigs (Rosero Salazar et al. 2025). Studies in rodents showed fibrosis and lower electromyographic activity when a full‐thickness induced injury impaired about 20% of the soft palate (Rosero‐Salazar et al. 2021; Rosero Salazar et al. 2021).

In the current large animal model, the small amount of muscle mass ablated in the left masseter seems to be compensated morphologically and functionally in the volume‐reduced group showing minimum alteration of the craniofacial growth. Unpublished electromyography results in the same experimental models from our group showed burst amplitudes of the left masseter within similar ranges as the right masseter with earlier activation onsets during mastication (Rosero Salazar et al. 2026). Similarly, preliminary unpublished histological results showed a specific fibrotic area in both tongue base and masseter although the activity in the latter was not critically affected. Likely, these compensations are related to the vast number of muscle fibers and the small percentage of volumetric reduction in this muscle.

In OSA patients smaller maxillary and mandible lengths were significantly different from normal‐weight patients (Huang and Gao 2021). These type of deformational changes of the craniofacial skeletons in enlarged soft tissue structures seem to mainly affect lower face bones including the mandible, all this aligned with the findings in the present study in obese minipigs. OSA patients have enlarged airways seen in the minipigs with increased oropharyngeal bony structures strongly associated with enlarged tongue in the human and large animal model.

Therefore, volumetric alterations of the tongue base induced remodeling effects in the craniofacial osseous dimensions either declining in volume‐reduced tongues or widening and lengthening in enlargement. All these changes seem to induce skeletal compensatory mechanisms to preserve the oropharyngeal function over time in mastication and respiration.

5. Conclusion

Volumetric alterations of the tongue either enlargement or reduction induce decreasing craniofacial growth than that observed in the intact tongue base. Yet this growth is even smaller in the volumetric reduced tongue base than in the enlarged model mostly in dental arches and the mandible. Similarly, alterations of the masseter muscle may affect the bilateral growth of the mandible in both experimental groups at a lower scale than that induced by volumetric changes of the tongue base. All this may suggest potential mechanisms that induces functional issues after reduction surgery not only related to intramuscular scar tissue but actual alterations in bone structures and mechanical stability.

Author Contributions

Amylia Liu: data curation, formal analysis, visualization, writing – review and editing. Doris Haydee Rosero Salazar: data curation, formal analysis, visualization, investigation, supervision, methodology, writing – original draft, writing – review and editing. Alexander Veasna Simnhoung: investigation, validation, methodology, writing – review and editing. Zi‐Jun Liu: conceptualization, investigation, funding acquisition, writing – review and editing, project administration, resources, validation, methodology.

Supporting information

Supporting File 1: Summary of body sizes for each experimental group and timepoint.

Supporting File 2: Raw and standardized data.

Supporting File 3:

Liu, A. , Rosero Salazar D. H., Simnhoung A. V., and Liu Z.‐J.. 2026. “Effects of Volumetric Alterations of the Tongue Base on Craniofacial Growth in the Adult Minipig.” Journal of Morphology 287: e70144. 10.1002/jmor.70144.

Data Availability Statement

The data that support the findings of this study are available in the supporting information of this article.