Time-based assessment of local propolis delivery on mid-palatal suture bone formation after rapid maxillary expansion in albino rats.

This paper was carried out to determine the time-dependent impacts of locally applied propolis in stimulating bone regeneration after rapid maxillary expansion (RME) in rats. Sixty growing male albino rats were randomly put in three equal groups (n = 20): Group I (control), Group II (systemic propolis) and Group III (local propolis hydrogel). RME was done on all the rats during seven days after which the deactivation of the devices was done to maintain retention. Group I received no treatment at the retention stage; Group II was given to receive daily systemic propolis and Group III was given a local injection of propolis hydrogel into the expanded MPS just before device deactivation. The regeneration of the bone was evaluated at 2- and 6-weeks of post-deactivation using histological, immunohistochemical, and histomorphometric studies. The histological and histomorphometric analyses showed that local propolis had a significant positive effect on bone formation, which was first presented in the form of a central bony plate with lateral bony processes that spread across the suture after 2 weeks. These gradually enlarged and interdigitated to create large bony plates which were in close approximation at the completion of the experiment period. Quantitative analysis has shown that the surface area of newly formed bone was much higher in the local propolis group than in the systemic and control groups. Both systemic and local propolis induced osteogenesis. Local delivery was found to have a higher and faster regenerative potential and may be considered as superior in restoring MPS microarchitecture following RME. Clinical trial number: This study was approved by the Scientific Research Ethics Committee, Faculty of Dentistry, Tanta University (Approval Number. R-OB-11-25-3232, registration date: November 2025).