Correlation of Tongue Position and Needs Ratio Across Various Skeletal Malocclusions: A Cone Beam Computed Tomography Study

ABSTRACT

Objective:  To evaluate the correlation between tongue posture and the Needs Ratio in untreated adults aged 18-25 years with varying sagittal (Class I, II, III) and vertical (hyperdivergent, normodivergent, hypodivergent) skeletal malocclusions, using cone-beam computed tomography (CBCT).

Material and Methods:  A total of 98 untreated adults aged 18-25 years were classified into skeletal Class I, II, or III malocclusions and further categorized into hyperdivergent, normodivergent, or hypodivergent growth patterns. Tongue posture was assessed at seven angular sectors using CBCT. The Needs Ratio was calculated as the ratio of pharyngeal depth to velar length. Mean values were compared across different skeletal classifications, and correlations between tongue-to-palate distance and the Needs Ratio were analyzed.

Results:  Class III hyperdivergent individuals demonstrated the highest Needs Ratio (mean: 0.87) and the greatest tongue-to-palate distance in all sectors, especially in posterior regions. In contrast, Class I normodivergent individuals showed the lowest Needs Ratio (mean: 0.71) and the most elevated tongue posture. A moderate positive correlation was identified between increased tongue-to-palate distance and elevated Needs Ratio.

Conclusion:  Tongue posture is significantly influenced by both sagittal and vertical skeletal morphology. Lower tongue posture increases pharyngeal depth relative to velar length, potentially compromising velopharyngeal closure. Elevated tongue-palate separation may serve as an anatomical indicator of velopharyngeal insufficiency risk, particularly in Class III hyperdivergent individuals.

Keywords:
Pharynx; Tongue; Palate; Malocclusion.

Introduction

Velopharyngeal function is critical for speech and deglutition and is anatomically governed by the relationship between the soft palate and the posterior pharyngeal wall. The Need’s Ratio, defined as the ratio of pharyngeal depth to velar length, is a commonly used cephalometric parameter to evaluate this relationship. Ratios exceeding the normative threshold of 0.8 are often associated with velopharyngeal insufficiency (VPI) [¹,²].

Parallel to this, tongue posture has emerged as a key anatomical determinant of oral and pharyngeal space. Studies have shown that low or posterior tongue posture can influence maxillofacial growth, airway patency, and orthodontic stability [³,⁴]. However, most existing literature has examined tongue posture [⁵] or velopharyngeal dimensions in isolation, with limited attempts to explore their interdependence. While CBCT now enables precise three-dimensional assessment of soft tissue structures, integrated evaluations of tongue position and Need's Ratio remain sparse.

Importantly, no prior study has systematically analyzed the correlation between tongue posture and Need’s Ratio across both sagittal malocclusion types and vertical growth patterns. This constitutes a critical gap in understanding the structural contributors to velopharyngeal dysfunction.

This study addresses this gap by examining CBCT-derived tongue-to-palate distances and Need's Ratios in Class I, II, and III skeletal patterns with varying vertical growth types. It aims to determine whether tongue posture serves as an anatomical indicator of velopharyngeal competence and a risk stratifier for its insufficiency.

Material and Methods

Study Design, Ethical Clearance and Source of Data

This study was designed as a retrospective, comparative cross-sectional investigation that had obtained ethical approval from the Institutional Ethics Committee (Ref. No. ETHICS/468/2024), and adhered to the ethical standards outlined in the Declaration of Helsinki. All reporting followed the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for cross-sectional studies [⁶].

CBCT images of 99 individuals aged 18-25 years were retrieved from the department's patient archive. These images were captured using the Planmeca 3D CBCT unit (Planmeca Oy, Helsinki, Finland), with patients seated in an upright position and maintaining a natural head posture. Uniform exposure parameters were maintained across all scans: 90 kV, 8 mA, and a field of view of 20.1 cm × 17.6 cm. All image analysis and measurements were performed using Planmeca Romexis software version 4.6.2.R.

Sample Size Calculation

The sample size was determined using a statistical model based on a between-group variance of 1.68, within-group variance of 0.5, and an effect size of 0.7. With three repeated measurements, a power of 95%, and an alpha error of 5%, the required sample size was calculated to be 98. To ensure even distribution and minimize bias, 33 samples were selected from each of the three skeletal malocclusion groups, yielding a total of 99 subjects.

Inclusion and Exclusion Criteria

Subjects included in the study were aged 18 to 25 years, had not undergone prior orthodontic treatment, exhibited no craniofacial anomalies, syndromes, or cleft conditions, and showed no signs of masticatory system dysfunction or respiratory disorders. Individuals with oral habits such as mouth breathing or tongue thrusting were also excluded.

Skeletal Classification and Grouping

Lateral cephalograms reconstructed from CBCT scans were used to classify subjects into skeletal malocclusion groups. Classification was based on ANB and Beta angles, where Class I subjects had ANB between 0° and 4° and Beta angle between 27° and 35°, Class II subjects had ANB greater than 4° and Beta angle less than 27°, and Class III subjects had ANB less than 0° and Beta angle greater than 35°. Vertical facial growth patterns were determined using Frankfort Mandibular Plane Angle (FMA) and the Y-axis. Normodivergent subjects had an FMA of 25° ± 5° and a Y-axis of 59°, hyperdivergent subjects had an FMA above 30° and a Y-axis above 59°, and hypodivergent subjects had an FMA below 20° and a Y-axis below 59° [⁷].

Velopharyngeal Measurements

Velar length was defined as the linear distance from the posterior nasal spine (PNS) to the tip of the uvula, as measured on the mid-sagittal CBCT slice with the palate at rest (Figure 1). Pharyngeal depth was measured as the perpendicular distance from the PNS to the posterior pharyngeal wall along the palatal plane. The Need’s Ratio was calculated by dividing the pharyngeal depth by the velar length. A Need’s Ratio exceeding 0.8 was considered indicative of increased risk for velopharyngeal insufficiency, in line with prior literature [²,⁸,⁹].

Figure 1
Measurement of pharyngeal depth and velar length.

Tongue Posture Assessment

Tongue posture was analyzed based on a modified version of the technique described by Graber et al. [⁵] (Figure 2). An angular template with a millimeter scale was applied on the sagittal CBCT slice to evaluate vertical tongue position relative to the palate after adjusting the contrast. The reference plane was established from the midpoint of a line joining the tongue tip and the deepest point of the epiglottis, and angular sectors were drawn at 30°, 50°, 70°, 90°, 110°, 130°, and 150°. At each sector, the vertical distance from the palate to the tongue surface was measured, yielding 7 measurements labeled T1-T7.

Figure 2
Tongue posture assessment using sector analysis.

Measurement Reliability

A single trained examiner performed all CBCT measurements to maintain consistency. To assess intra-examiner reliability, 15 randomly selected scans were re-measured after a two-week interval. The intraclass correlation coefficients (ICCs) for all variables were greater than 0.90, indicating excellent reliability and consistency in the measurement protocol.

Statistical Analysis

All statistical analyses were conducted using IBM SPSS Statistics version 23.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were computed and expressed as means and standard deviations. Data normality was evaluated using the Shapiro-Wilk test. One-way analysis of variance (ANOVA) followed by Tukey's post hoc test was applied to assess intergroup differences in velopharyngeal parameters and tongue posture. Pearson's correlation coefficient was used to examine the association between tongue-to-palate distance and the Need's Ratio. A p-value of less than 0.05 was considered statistically significant.

Results

Comparison of Velar Length and Pharyngeal Depth

Among hyperdivergent individuals, the mean velar length was highest in Class I subjects (mean: 32.5 mm, 95% CI: 30.6-34.3 mm) and lowest in Class III subjects (mean: 29.6 mm, 95% CI: 27.8-31.4 mm) (Figure 3). The mean pharyngeal depth did not differ significantly across skeletal classes within the same vertical pattern (Figure 4). However, when calculating the Need’s Ratio, Class III hyperdivergent individuals exhibited the highest mean value (mean: 0.87, 95% CI: 0.83-0.91), exceeding the generally accepted upper limit of 0.8. Class I and Class II hyperdivergent groups showed mean Need’s Ratios of 0.72 (95% CI: 0.69-0.76) and 0.74 (95% CI: 0.71-0.77), respectively (Figure 5).

Figure 3
Velar length among different skeletal malocclusions.

Figure 4
Pharyngeal depth among different skeletal malocclusions.

Figure 5
Needs Ratio among different skeletal malocclusions.

Tongue-to-Palate Distance Across Groups

Tongue position was analyzed across seven sectors (T1-T7). In Class I subjects, statistically meaningful differences were noted among vertical subgroups in sectors T4, T5, and T7. The mean tongue-to-palate distance in T5 was 9.4 mm (95% CI: 8.9-10.0 mm) in hyperdivergent individuals compared to 7.1 mm (95% CI: 6.7-7.6 mm) in normodivergent subjects.

In Class II individuals, hyperdivergent participants showed consistently greater distances in sectors T3-T7. Sector T6 had the highest observed mean in this group (11.2 mm, 95% CI: 10.6-11.9 mm), in contrast to 8.3 mm (95% CI: 7.8-8.8 mm) in normodivergents.

Among Class III participants, all seven sectors exhibited higher tongue-to-palate distances in hyperdivergent individuals. The greatest difference was observed at T7, where the hyperdivergent subgroup had a mean of 13.6 mm (95% CI: 12.9-14.4 mm), compared with 10.2 mm (95% CI: 9.6-10.8 mm) in the normodivergent group (Figure 6).

Figure 6
Mean Tongue-to-Palate Distances (T1-T7) across Hyperdivergent facial pattern.

Combined Skeletal and Vertical Pattern Effects

When combining both sagittal and vertical classifications, Class III hyperdivergent individuals demonstrated the most pronounced inferior and posterior tongue posture across all sectors, along with the highest Need’s Ratio. In normodivergent individuals, sector-wise tongue posture varied less sharply between skeletal classes, although Class III still consistently exhibited greater distances than Class I, particularly in sectors T3 and T6.

Correlation Between Tongue Position and Need’s Ratio

A moderate positive correlation was observed between posterior tongue-to-palate distance (particularly at sectors T6 and T7) and the Need’s Ratio. The Pearson correlation coefficient was r = 0.52 (95% CI: 0.39-0.64), indicating that increased tongue-palate separation in posterior sectors was associated with higher Need’s Ratio values (Figure 7).

Figure 7
Correlation Between Posterior Tongue Distance and Needs Ratio.

Discussion

This study explored the relationship between tongue posture and Need’s Ratio across different sagittal skeletal malocclusions and vertical facial growth patterns using CBCT-derived measurements. The findings revealed distinct anatomical variations, particularly in Class III hyperdivergent individuals, who demonstrated the highest Need's Ratio values and the greatest posterior-inferior tongue-to-palate distances, notably in the posterior sectors (T6-T7). This correlation between tongue posture and velopharyngeal configuration has both anatomical and clinical significance.

The elevated Need’s Ratio observed in Class III hyperdivergent subjects appears to result from a combination of maxillary retrusion and mandibular prognathism that extends the pharyngeal depth while simultaneously limiting the effective length of the soft palate. This skeletal arrangement increases the distance required for velopharyngeal contact, reflected in a higher PD/VL ratio. Vertical growth exacerbates this imbalance, as hyperdivergence induces clockwise mandibular rotation and elongation of the lower facial height, deepening the oropharyngeal space. These findings are consistent with prior reports suggesting that vertical dysplasia amplifies airway lengthening and may compromise velopharyngeal competence [¹⁰,¹¹].

Our data also showed that Class III individuals - irrespective of vertical pattern - consistently displayed more posterior tongue posture than Class I or II subjects, with hyperdivergent Class III participants exhibiting the most pronounced deviation. This is in agreement with previous CBCT studies indicating that mandibular prognathism leads to posterior hyoid displacement and tongue base repositioning, resulting in an inferior resting tongue posture [⁴,¹²].

The posterior displacement of the tongue may further restrict velopharyngeal closure, particularly in the absence of compensatory palatal length. The moderate positive correlation between posterior tongue-to-palate distances and the Need's Ratio reinforces this structural interdependence. Sector T6 and T7 distances showed the strongest associations, highlighting the influence of posterior tongue positioning on pharyngeal dimensioning. Similar findings have been reported in studies linking tongue posture to airway constriction and speech impairment, suggesting that a posteriorly located tongue increases the demand for velar elevation during functional activities such as speech and swallowing [¹³,¹⁴].

From a clinical standpoint, these insights have meaningful implications. Patients with Class III hyperdivergent profiles may be at a higher risk for velopharyngeal insufficiency, which could manifest as speech-related symptoms or compromised airway function. This risk becomes more relevant in orthognathic surgery planning, particularly when maxillary advancement or mandibular setback is involved. Studies have indicated that patients with a pre-existing structural predisposition (i.e., high Need’s Ratio and low tongue posture) are more vulnerable to velopharyngeal collapse postoperatively [¹⁵].

Furthermore, this study underscores the importance of including tongue posture analysis in comprehensive orthodontic assessment, especially for individuals with skeletal discrepancies. While conventional diagnostics emphasize hard-tissue relationships, our findings confirm that soft-tissue posture - particularly the tongue - can significantly influence the functional adequacy of the velopharyngeal complex. These conclusions support growing recommendations to integrate CBCT-based airway and soft tissue assessment into standard orthodontic protocols [¹⁶].

While this study offers important structural correlations, its limitations must be acknowledged. CBCT imaging, while accurate for anatomical measurement, is static and cannot capture dynamic functions such as velar movement during speech or swallowing. Future studies could incorporate nasoendoscopy or MRI to complement static measurements with functional assessments. Additionally, evaluating the role of orofacial myofunctional therapy in modifying tongue posture in high-risk skeletal groups may offer promising clinical pathways.

Conclusion

The study provides quantitative evidence that sagittal skeletal malocclusion and vertical facial growth patterns have a combined, measurable influence on tongue posture and the Need's Ratio. The posterior-inferior tongue posture, especially in Class III hyperdivergent individuals, appears to contribute directly to elevated Need’s Ratios, raising concerns about potential velopharyngeal insufficiency and post-treatment relapse. These findings emphasize the need for a multidimensional diagnostic approach that includes tongue posture, skeletal architecture, and soft tissue balance to guide comprehensive treatment planning.

• Financial Support
  None.

Data Availability

The data used to support the findings of this study can be made available upon request to the corresponding author.

References

• ^[1] Chhabra S, Khanna P, Munjal P, Mittal S, Arora N. Evaluation of tongue posture & dimensions in relation to skeletal Class I and Class II patterns-A cephalometric study. Int J Oral Health Dent 2021; 7(4):276-281. https://doi.org/10.18231/j.ijohd.2021.054
  » https://doi.org/10.18231/j.ijohd.2021.054
• ^[2] Khoja A. Soft palate dimensions and nasopharyngeal depth (Need’s Ratio) in different sagittal and vertical skeletal patterns: A lateral cephalometric study. Adv Dent Oral Health 2018; 8(1):555726. https://doi.org/10.19080/ADOH.2018.08.555726
  » https://doi.org/10.19080/ADOH.2018.08.555726
• ^[3] Bhambri E, Ahuja V, Ahuja S, Bhambri G, Choudhary A, Sukhija S. The association between soft palate shape and need's ratio in various sagittal skeletal malocclusions: A digital lateral cephalometric study. Int J Orthod Rehabil 2018; 9:8-13.
• ^[4] Yassaei S, Bahrololoomi Z, Sorush M. Changes of tongue position and oropharynx following treatment with functional appliance. J Clin Pediatr Dent 2007; 31(4):287-290. https://doi.org/10.17796/jcpd.31.4.lp479v346345460g
  » https://doi.org/10.17796/jcpd.31.4.lp479v346345460g
• ^[5] Graber TM, Rakosi T, Petrovic AG. Dentofacial Orthopedics with Functional Appliances. St. Louis: Mosby; 1997.
• ^[6] von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP, et al. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement: Guidelines for reporting observational studies. Lancet 2007; 370(9596):1453-1457.
• ^[7] Tweed CH. Frankfort-mandibular plane angle in orthodontic diagnosis, classification, treatment planning and prognosis. Am J Orthod Oral Surg 1946; 32(4):175-230. https://doi.org/10.1016/0096-6347(46)90001-4
  » https://doi.org/10.1016/0096-6347(46)90001-4
• ^[8] Madhu Preetha VS, Harsha Vardhan BG, Gopal KS, Lankupalli AS. Assessing the prevalence of velopharyngeal dysfunction and obstructive sleep apnea by correlating cone beam computed tomography parameters of soft palate with the STOP-BANG questionnaire. J Indian Acad Oral Med Radiol 2021; 33(3):294-300. https://doi.org/10.4103/jiaomr.jiaomr_81_21
  » https://doi.org/10.4103/jiaomr.jiaomr_81_21
• ^[9] Haidar ZS. Orthodontic considerations for orthognathic surgery: Velopharyngeal Need’s Ratio in lateral cephalometry. Ann Otolaryngol Rhinol 2024; 11(4):1344. https://doi.org/10.47739/2379-948X/1344
  » https://doi.org/10.47739/2379-948X/1344
• ^[10] Kim YJ, Hong JS, Hwang YI, Park YH. Three-dimensional analysis of pharyngeal airway space in children with different skeletal patterns. Orthod Craniofac Res 2010; 137(3):306.e1-11; discussion 306-307. https://doi.org/10.1016/j.ajodo.2009.10.025
  » https://doi.org/10.1016/j.ajodo.2009.10.025
• ^[11] Alves M Jr, Franzotti ES, Baratieri C, Nojima LI, Ruellas AC. Evaluation of pharyngeal airway space amongst different skeletal patterns. Int J Oral Maxillofac Surg 2012; 41(7):814-819. https://doi.org/10.1016/j.ijom.2012.01.015
  » https://doi.org/10.1016/j.ijom.2012.01.015
• ^[12] Kim SH, Choi SK. Changes in the hyoid bone, tongue, and oropharyngeal airway space after mandibular setback surgery evaluated by cone-beam computed tomography. Maxillofac Plast Reconstr Surg 2020; 42(1):27. https://doi.org/10.1186/s40902-020-00271-6
  » https://doi.org/10.1186/s40902-020-00271-6
• ^[13] Green JR, Wang YT. Tongue-surface movement patterns during speech and swallowing. J Acoust Soc Am 2003; 113(5):2820-2833. https://doi.org/10.1121/1.1562646
  » https://doi.org/10.1121/1.1562646
• ^[14] Graber LW. The “three M’s”: muscles, malformation, and malocclusion. Am J Orthod Dentofacial Orthop 1997; 111(3):300-306.
• ^[15] Jain I, Pradhan T, Sethia A. Evaluation of the effect of bimaxillary, mandibular setback, and advancement surgeries on the pharyngeal airway space and positions of the hyoid bone, soft palate, and tongue. J Orofac Sci 2024; 15(2):127-136. https://doi.org/10.4103/jofs.jofs_291_23
  » https://doi.org/10.4103/jofs.jofs_291_23
• ^[16] Proffit WR, Fields HW, Larson BE, Sarver DM. Contemporary Orthodontics. 6th ed. St. Louis: Elsevier; 2018.

Edited by

• Academic Editor:
  Alessandro Leite Cavalcanti

Publication Dates

• Publication in this collection
  06 July 2026
• Date of issue
  2026

History

• Received
  14 May 2025
• Accepted
  19 Nov 2025