A rat model for microimplant-assisted rapid palatal expansion.

BACKGROUND

Microimplant-assisted rapid palatal expansion (MARPE) has been widely used to correct maxillary transverse deficiency. To gain valuable insights into the biological processes and mechanisms involved in palatal suture expansion and develop approaches to reduce relapse rates, researchers have turned to animal models. However, no small-animal models are currently available for MARPE. This study aimed to establish a MARPE rat model and investigate the bone-remodeling mechanisms underlying this biological process.

METHODS

Three group sets were analyzed: 1) fifteen Sprague-Dawley rats were divided into three groups to validate the successful establishment of the MARPE model; 2) twenty rats were divided into four groups to screen for the optimal expanding force; and 3) twenty-five rats were used to investigate the radiological and histological changes during MARPE at different time points. Two mini-screws and a spring were used to provide the expanding force. Micro-computed tomography (micro-CT), micromorphological staining, and immunohistochemistry of the midpalatal sutures were performed.

RESULTS

Micro-CT demonstrated successful suture separation. The widths of the suture and palatal bone were greater in the MARPE group compared to those in the conventional tooth-borne rapid maxillary expansion (RME) group; moreover, the molar inclination was smaller. Additionally, 100 g was selected as the optimal expanding force. Histological analyses revealed the separation of the cartilage, proliferation and differentiation of cells, cartilage replacement, and active bone formation. The expression of osteogenic markers was increased after expansion.

CONCLUSIONS

We developed and validated a standardized rat MARPE model that can serve as an experimental model to study maxillary skeletal expansion. The MARPE model showed higher orthopedic efficiency and fewer side effects compared to conventional tooth-borne RME. New bone formation was active during MARPE. This novel, validated model is likely to be helpful for future MARPE research.