Correlation of Tongue Strength and Endurance with Overjet and Overbite in Angle Class I Malocclusion: A Study in Deutero Malay Race Ages 9–12 Years

Abstract

Aims and background

Tongue strength and endurance are important in assessing the ability of the tongue to perform its major functions, such as eating and phonetics, as well as its relationship to the functions of occlusion formation and malocclusion, which are still under study. Tongue strength and endurance can be assessed using the Tongueometer, which is a validated device with the Iowa Oral Performance Instrument (IOPI) tongue measuring device, USA. This research is an initial study to assess tongue strength and endurance in children of the Deutero Malay race.

Materials and methods

This is a cross-sectional clinical observational study. Tongue strength and endurance of a total of 44 participants aged 9–12 years were measured. Data were collected using the pressure transducer and Tongueometer. Overjet and overbite were measured using a metal ruler. Statistical analysis using Spearman correlation test. This study received approval from the Ethical Committee of the Faculty of Dentistry at Universitas Indonesia, with approval number 81/Ethical Approval/FKGUI/X/2024.

Results

Correlation between tongue strength to overjet, very weak positive (r = 0.09), not significant (p > 0.05); and correlation of tongue endurance to overjet, very weak positive (r = 0.08), statistically nonsignificant (p > 0.05); correlation of tongue strength to overbite very weak negative (r = −0.026) not significant (p > 0.05); and correlation of tongue endurance to overbite very weak positive (r = 0.063), unsignificant (p > 0.05).

Conclusion

Tongue strength and endurance in Angle Class I malocclusion are very weakly and not significantly correlated with overjet and overbite in 9–12-year-olds of the Deutero Malay race.

Clinical significance

Tongue strength and endurance in Angle Class I malocclusion are not influenced by overjet and overbite in 9–12-year-olds of the Deutero Malay race.

How to cite this article

Vynlia V, Budiardjo SB, Rizal MF. Correlation of Tongue Strength and Endurance with Overjet and Overbite in Angle Class I Malocclusion: A Study in Deutero Malay Race Ages 9–12 Years. Int J Clin Pediatr Dent 2026;19(8):968–971.

Introduction

The tongue is crucial for orofacial function and maintaining the balance in the stomatognathic system.¹ The equilibrium of stomatognathic along with tongue forming important functions of chewing, swallowing, and speech. All of these activities require the tongue to exert pressure on the palate.² The important role of the tongue in the swallowing process occurs in the oral phase. The oral phase ends when the extrinsic and intrinsic muscles of the tongue constrict to push the bolus into the pharynx.³ At this time, the tongue will exert pressure on the hard palate, pushing the bolus inside the oral cavity into the pharynx. Inadequate tongue pressure will affect these activities.

Tongue pressure during speech and eating is considered the standard for evaluating tongue muscle strength. It is believed that abnormal tongue position at rest and movements can cause malocclusion.² Constant pressure from involuntary and habitual behavior can change the bone structure, causing jaw deformity and malocclusion.^4,5 Malocclusion can be characterized by the malposition of teeth caused by a combination of genetic and environmental factors during development. The other etiology of malocclusion can be caused by abnormal functions, such as breathing through the mouth, abnormal swallowing, one-sided chewing, tongue thrust, tongue biting, and a lower resting position of the tongue. Several studies show that tongue pressure is related to tooth position and malocclusion.⁵ Children with anterior open bite and tongue thrusting while swallowing exhibit lower maximum tongue pressure than their peers without these conditions.^2,3

There are three criteria to evaluate tongue function: tongue strength, swallowing pressure, and tongue endurance.⁶ In this study, tongue strength and endurance were measured using a device named Tongueometer (Fig. 1). The measurement took place as the tongue pressed the bulb against the front of the hard palate, with data being recorded via a mobile application. This device was validated against the Iowa Oral Performance Instrument (IOPI), the recognized standard for assessing tongue strength and endurance. The Tongueometer can be an alternative to IOPI since it is easier to operate, simple, and affordable. An extra mobile device was needed to show the data using Tongueometer.⁷ Malays are members of the Austronesian family and predominantly inhabit the east coast of Sumatra and the coast of Borneo.⁸ Main subraces in Indonesia are Proto Malay and Deutero Malay. Deutero Malay came during the second migration and spread out to different parts of the Indonesian archipelago. They have the characteristics of black straight hair, brown and slanted eyes, yellow to brown skin, small jaw bones, and bodies compared to Proto Malay race.⁹ There were no data about tongue strength and endurance in Deutero Malay children. Thus, this study aims to assess the correlation of tongue strength and endurance with overjet–overbite in Deutero Malay children.

Fig. 1:

Tongueometer and the application's interface on the mobile device⁷

Materials and Methods

The study population of this cross-sectional, correlation, and descriptive research was made of 44 children aged 9–12 years of Deutero Malay race. All participants were in Angle classification class I and had no bad habits. Children with oral dysphagia, special needs, intellectual disability, anterior crossbite, tongue tie, ankyloglossia, and macroglossia were excluded. This study received approval from the Ethical Committee of the Dentistry Faculty at the Universitas Indonesia, with approval number 81/Ethical Approval/FKGUI/X/2024.

Initially, participants were requested to provide consent for this study. Subsequently, participants were informed about the methods used to assess tongue strength and endurance. Participants were chosen according to their occlusal relationship within Angle malocclusion class I by the researcher. Overjet and overbite were measured and recorded using a metal ruler. Then, the researcher measured participants' tongue strength and endurance using Tongueometer. While measuring, participants were asked to sit upright in a relaxed position (Fig. 2). For overjet and overbite, participants were also asked to occlude. For tongue strength measurement, the bulb was placed inside the participant's mouth, at the midpoint palatal side of their central incisors, and asked to press the bulb using the anterior part of the tongue as much as possible against the palate for approximately 5 seconds (Fig. 3). The measurement was repeated three times at intervals of 1 minute. The mean of the three measurements was considered the maximum tongue pressure. To measure the tongue endurance, the participants were instructed to adhere to the same guidelines for the bulb placement inside the mouth. Participants must maintain at least 50% of the maximum pressure against the palate for as long as they can. The time was recorded through the Tongueometer, and the measurement was repeated three times at 1-minute intervals. The mean of the three measurements was considered the maximum tongue endurance.

Fig. 2:

Positioning of the Tongueometer in the participant's oral cavity against the palate. The pressure value was recorded

Fig. 3:

The bulb is pressed against the palate by the tongue

The bulb of the Tongueometer was disinfected and inflated every usage. The reference data includes values for tongue pressure measured in kilopascals (kPa) and tongue endurance measured in seconds (s).

Results

Forty-four children met the inclusion criteria, of whom 29 were males (65.9%), and 15 were females (34.1%). The average maximum tongue strength was 43.1 ± 1.52 kPa, and the median maximum tongue endurance was 3.25 s. The median overjet and overbite were both 2 mm (Table 1). Normality testing using the Shapiro–Wilk test showed a p-value of > 0.05 on the variable tongue strength (normally distributed) but a p-value of < 0.05 on the variables tongue endurance, overjet and overbite.

Table 1:

Characteristics of tongue strength, tongue endurance, overjet, and overbite of the investigated 9–12-year-old Deutero Malay children

Variable	Minimum	Maximum	Median	Mean ± SD
Tongue strength	32.6	70.9	−	43.1 ± 15.22
Tongue endurance	1.6	14.5	3.25	−
Overjet	0.5	5	2	−
Overbite	0.5	5	2	−

A Spearman's correlation analysis was conducted to assess the relationship between tongue strength and endurance with overjet and overbite. It reveals the correlation between tongue strength and overjet is positive, insignificant (p > 0.05), and very weakly correlated (r = 0.09). The correlation between tongue endurance and overjet is positive, insignificant (p > 0.05), and very weakly correlated (r = 0.08). Hence, the correlation between tongue strength and overbite is negative, insignificant (p > 0.05), and very weakly correlated (r = −0.026). The correlation between tongue endurance and overbite is positive, insignificant (p > 0.05), and very weakly correlated (r = 0.063) (Table 2).

Table 2:

Correlation between tongue strength, endurance, overjet, and overbite of the investigated 9–12-year-old Deutero Malay children

Variable	r-value (coefficient correlation)	p-value
Tongue strength–overjet	0.09	0.560
Tongue strength–overbite	−0.026	0.869
Tongue endurance–overjet	0.989	0.02
Tongue endurance–overbite	0.063	0.684

Discussion

The equilibrium between tongue muscles and oromotor muscles can influence the teeth's position to form and maintain the dental arch shape. Lips can exert force toward the teeth and tongue, exerting opposite force toward the lips to achieve equilibrium. This force is called intrinsic force. The relationship among malocclusion, tongue, and perioral muscles is called the equilibrium theory.^10–12 This can change due to disrupting forces, e.g., tongue thrusting, lip sucking, finger sucking, and other tongue-associated habits.¹³ The tongue is a strong muscle that exerts pressure when functioning, such as mastication, swallowing, and speaking. Three objective measurements to evaluate tongue function are tongue strength, swallowing pressure, and tongue endurance. Many studies have explored the link between tongue strength and tooth arrangement but have not provided definitive results.⁶

In this study, Tongueometer is used as an alternative to the gold standard, IOPI. It is a medical device that has been validated against IOPI and can be used publicly at an affordable price.¹⁴ It uses a plastic bulb that is easy to clean and disinfect. The bulb will deflate when pressed against the palate. Based on previous studies, the strength and endurance values of the adult tongue recorded by the IOPI and Tongueometer have slight differences; the Tongueometer value is lower by about 4 kPa consistently for each use. Tongueometer uses a plastic bulb filled with air that collapses against the hard palate to evaluate tongue strength and endurance. Tongue strength is quantified in kilopascals (kPa), while tongue endurance is assessed in seconds. The advantages of using Tongueometer are that the bulb is easy to clean, textured to minimize slippage, easy to operate with an attractive interface, and easy to purchase.¹⁵

The reference range of tongue strength values is 40–80 kPa with an average value of 63 kPa, and the tongue endurance value is 10 seconds measured using IOPI in healthy adults.¹³ There is no reference value available in children with Tongueometer. This study shows the range of tongue strength values in children aged 9–12 years is 32.6–70.9 kPa with an average of 43.1 ± 1.522 and a median endurance value of 3.25 seconds. A previous study mentioned that tongue strength in children aged 4–6 years old in Japan showed that the average tongue strength in children aged 6 years old was 18 kPa.² This condition is associated with increased tongue strength and age due to increased tongue volume and nerve control. During preschool, the hard palate and tongue volume rapidly grow to 80% of adult size by age 6, then slow down and mature by 18. This mirrors how bone grows faster than muscles and nerve control during skeletal maturity.^6,16 Tongue endurance is a demanding exercise where participants must sustain pressure on a bulb against the hard palate as long as possible. Challenges in tongue endurance arise from the involvement of type 2 muscle fibers (fast twitch), which contract rapidly but fatigue more easily than type 1 fibers (slow twitch). A muscle is deemed less fatigable when an individual can sustain a consistent pressure on the bulb. Type 2 muscles are mostly located in the anterior area of the tongue.¹⁷

Conclusion

Tongue strength and endurance in Angle Class I malocclusion are very weakly and insignificantly correlated with overjet and overbite in 9–12-year-olds of the Deutero Malay race. This research was the first to measure tongue strength and endurance in the Deutero Malay race with malocclusion Angle Class I. Therefore, future studies should focus on exploring tongue strength and endurance in the Deutero Malay population.

Clinical Significance

Tongue strength and endurance in Angle Class I malocclusion are not significantly influenced by overjet and overbite in 9- to 12-year-olds of the Deutero Malay race. Future research with larger sample sizes, different malocclusion types, and races would broaden the knowledge about tongue strength and endurance in children. This would give more perspectives on interceptive treatment in children. Furthermore, tongue exercises using Tongueometer to enhance tongue strength and endurance should be explored more.

Ethics Approval and Consent to Participate

This study was approved by Dental Research Ethics Committee, Faculty of Dentistry, Universitas Indonesia (approval number: 81/Ethical Approval/FKGUI/X/2024) on 18th October 2024 and all participants and their parents/guardians provided written informed consent for participation in the study.

Acknowledgments

The authors are grateful to the volunteers who participated in this study.

Author Contributions

Nil.

Orcid

Vynlia Vynlia https://orcid.org/0009-0009-0017-9753

Sarworini Bagio Budiardjo https://orcid.org/0000-0002-2506-6191

Mochamad Fahlevi Rizal https://orcid.org/0000-0001-6654-7744

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.