Integration of various forms of Salvadora Persica « Siwak » into dental composites: A pilot in vitro study

This study assessed the potential of Salvadora Persica (Siwak) as a natural bioactive agent for developing dental composites with antibacterial and antioxidant properties. The primary aim was to evaluate its efficacy and identify the optimal form whether powder, extract, or fibers, that achieves a balance between bioactivity, mechanical and physical characteristics.

Various forms of Algerian and Oriental Siwak (powder, extracts and fibers), were incorporated at 5 % w/w into experimental dental composites. Flexural strength (FS), flexural modulus (FM) and degree of conversion (DC) were assessed to identify the optimal form. Metabolic activity of Streptococcus mutans in contact with pure Siwak was quantified using the Alamar Blue assay. Antibacterial activity of Siwak-based composites against bacteria was evaluated using turbidity tests, while bacterial cell counts and biofilm formation were analyzed via Scepter™ automated bacteria counter and scanning electron microscopy (SEM), respectively. Antioxidant capacity was determined through the 2, 2-Diphenyl-1-picrylhydrazyl (DPPH) assay.

Siwak powder and hot extracts at 5 % incorporation achieved acceptable FS (>85 MPa) and did not affect FM and DC. Siwak-based composites exhibited antioxidant capacities ranging from 6.1 % to 23.4 %, and reduction in bacterial growth of 31.3 %-33.9 %. Hot Algerian Siwak extract was the most effective form. Microwave extracts and fibers negatively affected FS.

Siwak-based dental composites exhibited dual functionality by providing antioxidant properties and inhibiting S. mutans growth without compromising physical and mechanical properties. Siwak biological potential suggest possible application in other dental materials, offering a promising strategy for secondary caries prevention and enhancing restoration longevity.