Toothpaste—particularly those containing sodium lauryl sulfate (SLS) and certain fluoride compounds—can chemically interact with chlorhexidine and significantly reduce its substantivity. Substantivity refers to chlorhexidine’s ability to bind to oral tissues and remain antimicrobial for 8–12 hours. When chlorhexidine is used immediately after brushing, these interactions decrease its binding capacity, leading to reduced clinical effectiveness.
Therefore, a minimum 30-minute interval is recommended to preserve chlorhexidine’s full therapeutic action.

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