In vitro evaluation of anti-inflammatory, anti-plaque efficacy, and biocompatibility of Norway spruce (Picea abies) resin extract for oral care applications

The periodontal disease is globally highly prevalent, and calls for novel, effective, and preferably bio-based raw materials. Accumulation of dental plaque causes gingivitis, which is reversible by treatments that control the bacterial biofilm. If left untreated, the gingivitis can lead to gingival inflammation and potentially progress to periodontitis. In this study, a natural antimicrobial and anti-inflammatory Norway spruce (Picea abies) resin extract was evaluated as a potential option in supportive periodontal care. Lipopolysaccharide-induced macrophage-like cells were used to study the anti-inflammatory properties in vitro. The spruce resin extract at 20 % concentration had the highest anti-inflammatory effect, comparable to a corticosteroid's effect on pro- inflammatory cytokines interleukin-1 beta (IL-1(3), tumor necrosis factor-alpha (TNF-alpha), and matrix metalloproteinase-3 (MMP-3). Consequently, the 20 % spruce resin extract was selected for toothpaste formulation. Its anti-plaque efficacy was evaluated by total aerobic colony counts and the proportions of streptococci grown on the surfaces of the treated glass rods using pooled human saliva. It was found that the toothpaste effectively reduced dental plaque biofilm, matching the anti-plaque efficacy of Corsodyl mouthwash, containing chlorhexidine digluconate. The toothpaste was also found to be non-damaging in biocompatibility studies on three-dimensional (3D) tissue models of human oral and gingival epithelium. These findings provide scientific validation of spruce resin's effectiveness in oral care, elucidating probable reasons why people have historically chewed resins for oral care purposes.