# Effect of twin block on intracranial pressure

## TL;DR

This study found that Twin Block appliances temporarily increase intracranial pressure in adolescents, as measured by optic nerve sheath diameter.

## Contribution

The study is the first to report a significant temporary increase in intracranial pressure due to Twin Block appliance use in adolescents.

## Key findings

- ONSD increased significantly 1 and 10 minutes after appliance placement.
- The increase in ONSD was temporary and not observed after one month of treatment.
- Mean arterial pressure decreased significantly 10 minutes after appliance placement.

## Abstract

This study aimed to investigate the impact of Twin Block appliances on intracranial pressure (ICP) in adolescents by measuring the optic nerve sheath diameter (ONSD) using ultrasonography.

We conducted a prospective study involving 20 adolescents (8 girls and 12 boys) with skeletal mandibular retrognathia undergoing treatment with Twin Block appliances. ONSD measurements were taken at six different time points: before appliance placement (T0), 1 min after placement (T1), 10 min after placement (T2), one month after the start of treatment with twin block (T3), immediately after appliance removal (T4), and 10 min after removal (T5). Mean arterial pressure (MAP), heart rate, and peripheral oxygen saturation (SpO2) were also monitored. Statistical analyses were performed using Friedman and Wilcoxon Signed-Rank tests with Bonferroni correction, considering p < 0.05 as statistically significant.

Significant increases in ONSD were observed at T1 and T2 compared to T0 (p < 0.05), with the highest ONSD recorded at T1. No significant changes in ONSD were noted at T3 or T5, indicating that the initial increase in ONSD was temporary. MAP showed a significant decrease at T2, but no significant changes were observed in SpO2 or heart rate across the time points.

This study is the first to report a significant increase in ICP, as indicated by ONSD, in adolescents using Twin Block appliances. The observed rise in ONSD shortly after appliance placement suggests a temporary increase in ICP. These findings highlight the importance of monitoring intracranial pressure during orthodontic treatment, particularly in adolescents.

The online version contains supplementary material available at 10.1007/s00784-025-06214-7.