Do enlarged tonsils really influence dentofacial development?

Adenotonsillar hypertrophy can obstruct the upper airway, which may result in children breathing through their mouths. It is a common belief that this may influence their craniofacial growth and dental occlusion. 

This concept tends to be based on various interpretations of the classic papers by Linder-Aronson and Harvold.  However, these two papers are not the only sources of information on the relationship between enlarged tonsils and craniofacial morphology. We should consider other studies. This new systematic review, which incorporates data from many studies, is of both clinical and scientific importance.

A team from Wuhan, Guangzhou, China; West Virginia, USA; and Manchester, North of England, conducted this study. The AJO-DDO published the paper.

What did they ask?

They did the study to ask

“What is the evidence regarding the association between adenotonsillar hypertrophy and dentofacial characteristics in children”?

What did they do?

The team did an extensive systematic review of the current literature. The details of the review were:

Types of study

This included cross-sectional studies comparing the dental/craniofacial characteristics between children with and without adenoid or tonsillar hypertrophy.

Participants

Children aged less than 18 years with Adenoid and or tonsillar hypertrophy. These were the hypertrophy group (HG). Children without hypertrophy were in the control group (CG).

The authors of the included paper diagnosed hypertrophy using cephalometric assessments, oral examination, or nasopharyngeal endoscopy. Importantly, there was no universally applied measure for this variable.

They derived the outcomes of craniofacial pattern or dental features from cephalometric measurements, photographs and dental casts. Again, there was a large amount of variation in these measures.

Outcomes

The primary outcomes for the review were SN-MP and overjet for dental occlusion. They included several other cephalometric and dental measurements as secondary outcomes.

The team followed standard systematic review methods for their study. This was an experienced and well-regarded research team.

Importantly, they used the Newcastle-Ottawa scale of cross-sectional studies to evaluate any bias and the GRADE assessment to evaluate the certainty of evidence.

What did they find?

Following the initial filter of papers, they identified a final sample of 31 studies. These included data on 8,132 children; 3,845 were in the hypertrophy group, and 4,287 were in the control group.

Upon examining the quality of the studies, nine were unsatisfactory, 14 were satisfactory, 11 were good, and two were classified as of very good quality.

When they looked at the primary outcome measures. The following measurements were statistically significant. The SN-MP angle mean difference between the HG and CG was 2.2 degrees (95% CI=1.47-2.92). There were no differences in ANB between the groups. They reported minor differences for SNA and SNB angles.

Evaluation of dental features revealed a higher relative risk for Angle Class II and III malocclusion (1.29) and open bite (1.65) among children in the HG. Finally, the intermaxillary molar width was smaller in the HG group by 1.3 mm (95% CI=2.12-0.56).

The GRADE assessment revealed that for 16 of the outcome measures, the certainty of evidence was graded as very low.

Their conclusion was

“Based on evidence of very low or low certainty, children with ATH hypertrophy had different craniofacial characteristics than children without ATH”.

However, another important conclusion was

“The statistically significant differences identified are relatively small, raising questions about their clinical significance”

What did I think?

This was a thorough review conducted to a high standard by an experienced team. They followed standardised protocols and reported on a large amount of data. I have only highlighted the data I considered most important.

I found it interesting that they identified differences between the groups in their analyses. Importantly, these differences were statistically significant. However, we need to consider whether the effect sizes were clinically significant. To do this, we need to examine both the effect sizes and the 95% confidence intervals of the differences. This indicates that these findings are not clinically significant.

The authors of the review wrote a balanced and clear discussion. I particularly thought that their discussion of the shortcomings was very clear. They pointed out that it was difficult to analyse the data because of the marked differences in measurement of both hypertrophy and dentofacial form. They felt that this reflected the real-world diversity in study populations and methods. I would also like to add that some potential biases would be influenced by the large sample size of both publications and children included in the review.

Final comments

We now need to consider how this review enhances our understanding of this issue. This is for you as a practising clinician to decide. My impression is that this research suggests adenotonsillar hypertrophy is associated with statistically significant effects on morphology but these were not clinically significant. This is an important distinction.

So, can we be more sensible about expounding incorrect theories on the role of breathing and facial growth? Or at least have a rational discussion?

Key points

• Common Belief about Tonsils and Facial Growth: It is widely believed that enlarged tonsils and adenoids can negatively influence facial development, a notion often supported by classic studies cited by orthodontists and dentists.
• Limitations of Classic Studies: The foundational papers by Linder-Aronson and Harvold are not the only sources on this topic, and relying solely on them overlooks newer, comprehensive research.
• Purpose of the New Systematic Review: A recent systematic review aimed to investigate the evidence linking adenotonsillar hypertrophy with craniofacial characteristics in children.
• Methodology of the Review:** The study analyzed cross-sectional studies comparing children with and without hypertrophy, using rigorous tools like the Newcastle-Ottawa scale and GRADE for bias and evidence quality.
• Key Findings and Clinical Significance:** The review included data from 31 studies with over 8,000 children; it found statistically significant but clinically small differences in facial measurements, with very low certainty of evidence.