# Effect of Rapid Maxillary Expansion on the Pterygoid Process and Spheno‐Occipital Synchondrosis in Skulls With Class II and Class III Skeletal Relationships: A Finite Element Analysis Study

## TL;DR

This study uses computer modeling to compare how rapid maxillary expansion affects skull structures in patients with two different jawbone conditions.

## Contribution

The study introduces a finite element analysis approach to compare stress distribution in Class II and Class III skeletal patterns during rapid maxillary expansion.

## Key findings

- Class III models showed higher stress at the skull base compared to Class II models during rapid maxillary expansion.
- Both Class II and Class III models experienced tensile and compressive loads in the pterygoid process and spheno-occipital synchondrosis during RME.
- Stress values varied between Class II and Class III models at specific anatomical points during simulated rapid maxillary expansion.

## Abstract

To evaluate the effect of the rapid maxillary expansion (RME) on the pterygoid process (PP), spheno‐occipital synchondrosis (SOS), and sella turcica (ST) in two patients’ skulls with Class II and Class III skeletal relationships and to identify differences in mechanical loading through finite element analysis (FEA).

Cone‐beam computed tomography (CBCT) scans of two patients’ skulls were used: (1) a 13‐year‐old female with a Class II skeletal relationship due to maxillary protrusion and (2) a 14‐year‐old male with a Class III skeletal relationship due to maxillary hypoplasia. The computer‐aided design (CAD) geometry of both skulls was imported into Ansys v14 software to construct the finite element mesh. A transverse force of 100 N was applied to the palatal surfaces of the first upper molar and first premolar to simulate RME. Von Mises stress (VMS) and maximum principal stress (MPS) were assessed at selected nodes representing the anatomical areas of interest.

In VMS, the Class II model showed the highest value at Point 3 (2.077 MPa), similar to the Class III model (1.707 MPa). In MPS, the highest tensile stress in the Class II model occurred at Point 2 (1.396 MPa), while in the Class III model it was at Point 3 (1.813 MPa).

The PP, SOS, and ST in Class II and Class III skeletal patterns are subjected to tensile and compressive loads during RME. The Class III model exhibited higher stress distribution at the skull base compared with the Class II model.

Understanding how delicate cranial structures respond to heavy orthopedic loads generated during RME may help refine treatment protocols for transverse maxillary deficiency across different malocclusions.