Time-dependent Tooth Color Changes Following Conventional, Silver-based, and Photodynamic Root Canal Irrigants: An In Vitro Study

Discoloration of endodontically treated teeth is an aesthetic concern. The primary causes include persistent pulpal tissue breakdown and the use of various irrigants. This study compared the effects of different endodontic irrigants on tooth color stability over time.

Eighty single-rooted human central incisors were allocated into eight groups (G): G1, G2, G3, G6, and G7 used sodium hypochlorite and silver-based compounds; G4 received Photodynamic Therapy (PDT); G5 received combined PDT and NaOCl; and G8 was treated with 0.9% normal saline. Tooth shade was assessed at baseline (T0), after 1 (T1), 7 (T2), 14 (T3), and 28 days (T4) using a spectrophotometer.

At T1, G5 showed the least color change (ΔE), while G2 had the most (p <0.05). By T2, G1 had lower ΔE values than G3 and G7 (p <0.05). At T3, G5 showed the least ΔE changes compared to G2, G3, G6, and G7 (p <0.05). Conversely, G7 had the highest ΔE compared to G1 and G4 (p <0.05). At T4, G7, G6, G2, and G3 exhibited higher ΔE than G5, G4, G1, and G8 (p <0.05).

Silver-based irrigants caused significant darkening due to silver deposits in dentinal tubules and silver-protein precipitates. Sodium hypochlorite caused fewer changes due to its crystallization potential. Photodynamic therapy led to color changes above clinical thresholds, but its combination with NaOCl reduced discoloration to imperceptible levels. Silver-based irrigants should be used cautiously in anterior teeth due to their high staining potential.

Root canal irrigants induced varying degrees of tooth color changes. Among them, silver fluoride caused the most significant early darkening, while the combination of photodynamic therapy with sodium hypochlorite resulted in minimal darkening over time.