The numbers are both surprising and thought-provoking: among children with Down syndrome aged 6 to 8 years, the average oral cavity volume is only approximately 15.34 cm³. In comparison, children aged 16 to 18 years reach an average volume of 25.13 cm³. The volume does increase with age, but the pattern of growth tells a much more complex story than the numbers alone suggest.
This was the main finding of a study conducted by dr. Faisal Rizki together with Dr. drg. Indra Bramanti, M.Sc., Sp.KGA(K), and drg. Indah Titien Soeprihati from the Department of Paediatric Dentistry, Faculty of Dentistry, Universitas Gadjah Mada. Published in Jurnal Kesehatan Gigi, Volume 12, Issue 1, 2025, the study represents an important effort to map oral cavity characteristics among children with special needs in Yogyakarta.
Trisomy 21 and Abnormal Jaw Development
Down syndrome occurs due to the presence of an extra chromosome 21, a genetic condition affecting approximately one in every 691 live births. Its effects extend beyond the characteristic physical appearance commonly associated with the condition. In the middle region of the face, known as the midface region, hypoplasia occurs, referring to underdevelopment in three dimensions: vertical, lateral, and anteroposterior dimensions. The upper jaw develops smaller, narrower, and shorter than expected.
The palate of children with Down syndrome tends to be high-arched and narrow. This condition is not caused solely by genetic factors. Tongue hypotonia, weakness of perioral and masticatory muscles, and tongue-thrusting habits also contribute as secondary factors that worsen palatal narrowing. When the tongue fails to provide adequate balancing pressure from inside the oral cavity, external cheek pressure becomes dominant, resulting in a narrower upper jaw structure.
Overexpression of the DSCR4 gene on chromosome 21, which plays a role in neural crest cell migration, is believed to be one of the key factors explaining why children with Down syndrome develop distinct facial morphology rather than simply experiencing general growth delays.
Digital Scanners Enter Special Schools
The study involved 28 children with Down syndrome from three state special schools in Yogyakarta: SLBN 1 Yogyakarta, SLBN 2 Yogyakarta, and SLBN 1 Pembina Yogyakarta. Data collection was conducted from August to November 2024.
One of the most interesting aspects of the study was its methodology. Instead of using conventional dental impressions, which can often be challenging for children with special needs, the research team used a Shining 3D Dental intraoral scanner to digitally capture the oral cavity. Scanning covered the upper jaw, lower jaw, and occlusal areas. The oral cavity volume was then calculated using 3Shape 3D Viewer and Inventor Professional 2020 software by measuring arch length, interpremolar and intermolar width, and palatal height extending to the floor of the mouth.
The choice of this technology was not accidental. Intraoral scanners have been shown to be more effective and efficient for children with special needs, who often have limited tolerance for conventional clinical procedures.
Strong Correlation, but No Significant Difference
The statistical results of this study revealed an interesting paradox.
The correlation between age and oral cavity volume was very strong, with an R value of 0.942. This indicates that as age increases, oral cavity volume tends to increase, with an average increase of approximately 3.208 cm³ between age groups. Furthermore, 88.73% of the variation in oral cavity volume could be explained by age alone.
However, the t-test showed a p-value of 0.058, which is above the conventional significance threshold of 0.05. Statistically, the differences among age groups were therefore not considered significant.
“The relationship between age and oral cavity volume in children with Down syndrome was not statistically significant (p = 0.058), despite a very strong positive correlation (R = 0.942), indicating that oral cavity volume increases with age.”
The most noticeable increase occurred between the 6–8-year-old and 9–12-year-old groups. After this period, volume growth tended to slow down. The 13–15-year-old group recorded an average volume of 24.12 cm³, while the 16–18-year-old group showed only a slightly higher value of 25.13 cm³. The increasing standard deviation, however, reflected considerable individual variation.
This wide variation is not an anomaly. Instead, it reflects the complexity of Down syndrome itself. Differences in tongue size, tooth eruption patterns, oral habits, muscle hypotonia, and individual development mean that no two children with Down syndrome present exactly the same physical characteristics.
Beyond Oral Cavity Measurements
This study contributes to a broader discussion beyond numerical measurements of oral volume. The oral cavity is not only involved in chewing but also serves as a space for voice production. Its dimensions influence speech frequency and quality. Children with Down syndrome frequently experience speech difficulties, and accurately understanding their oral cavity volume may provide a stronger foundation for collaboration between paediatric dentists and speech therapists.
For paediatric dentists, these findings provide valuable insight into complex craniofacial growth patterns that cannot simply be compared with children without developmental conditions. Appropriate treatment planning—including decisions regarding the timing of orthodontic interventions—requires an understanding of how the oral cavity develops in children with Down syndrome and what limitations may exist.
The children from the three state special schools in Yogyakarta may not realise that the data collected from their oral cavities could one day help other children born with similar conditions receive better care. Yet this is how science progresses: slowly, carefully, and step by step.
Authors: Nanda Ayu; drg. Achmad Zam Zam Aghasy, M.Kes.
Photo: Pexels