SDF and Potassium Iodide: Will Root Cavities Stay Tooth-Coloured?

Before agreeing to silver diamine fluoride (SDF) for a visible root cavity, ask what the treated spot could look like months later. The American Dental Association¹ lists permanent black staining of arrested cavities among SDF’s common adverse effects.¹

What happened after 30 months

A 2016 Hong Kong trial² included 83 older adults with 157 active root-caries lesions. Annual treatment was soda-water placebo, 38% SDF, or SDF immediately followed by KI.²

At 30 months, among arrested lesions, 69% were black and 25% dark brown with SDF alone. With SDF plus KI, 62% were black and 32% dark brown. The colour distributions were not significantly different. These are lesion percentages, not patient satisfaction scores.²

The researchers observed a bright yellow precipitate immediately after KI application, but found no lasting colour improvement.²

The limits matter when discussing a product

Only 100 of the original 157 lesions were reviewed at 30 months. More decay predicted poorer retention, risking bias.²

The trial used laboratory-prepared KI and annual applications in older adults. Sample size was calculated for new decay.² This particular result cannot settle every formulation, application schedule or tooth surface.

It does give you a specific question for a proposed treatment: “What evidence shows how this exact approach looks after months or years on adult root cavities?” Ask whether the supporting photographs are from patients followed over time, laboratory specimens, or the day of treatment.

Make the appearance discussion tooth-specific

The ADA calls for a patient-specific plan, discussion of available options and side effects, and follow-up monitoring when SDF is used for caries management.¹ Before consenting, ask your dentist to point out each proposed treatment site in a mirror.

Write down:

• Visibility: “Which spots will show when I talk or smile?”
• Colour expectations: “Could these still become black despite the KI?”
• Alternatives: “What other treatments suit these particular cavities, and what would they cost?”
• Later work: “Would a restoration be appropriate afterwards, and is that included in this plan?”
• Review: “When will you check whether the decay has stopped?”

The ADA notes that further restoration may be needed to restore a cavitated tooth’s form and function, and can also reduce discolouration.¹ Ask how that applies to your tooth before assuming an extra liquid step will preserve its appearance.

The “What to Say at the Appointment” section in Is It My Breath? offers wording for raising concerns at a dental visit. For this decision, bring a direct sentence: “I want to discuss the lasting colour change before we treat a tooth I can see.”