Dental Literature Watch · Trial · Cariology
SDF Beats Fluoride Varnish for Arresting Early Caries in Permanent Molars
TL;DR
- SDF is usually discussed in primary teeth. This trial is in first permanent molars.
- 88.1% of SDF-treated teeth reached ICDAS 0 at six months, versus 65.6% with 5% fluoride varnish (p < 0.001).
- Eruption stage did not matter (p = 0.99) — partially erupted molars responded as well as fully erupted ones.
- Both treatments significantly improved on baseline; SDF was simply better.
- One session, no drilling, no anaesthetic — which is the whole point in a 7-year-old with a partly erupted six.
The study
| Design | Randomised, controlled, blinded clinical trial; cluster randomisation at school level |
| Population | 165 children aged 6–12. 660 first permanent molars assessed; 139 teeth with ICDAS 1 or 2 analysed |
| Groups | G1: 38% SDF + potassium iodide | G2: 5% fluoride varnish |
| Follow-up | 6 months, caries arrest by ICDAS |
| Result | ICDAS 0 in 88.1% vs 65.6%, p < 0.001 |
| Eruption stage | No significant influence in either group (p = 0.99) |
💎 Insight — what this means chairside
The partially erupted six is the hardest tooth in paediatric dentistry
It cannot be isolated well, it cannot be sealed reliably, and it is erupting through the exact age band where caries risk peaks.
A single application that works regardless of eruption stage is a genuinely useful answer to that problem.
It cannot be isolated well, it cannot be sealed reliably, and it is erupting through the exact age band where caries risk peaks.
A single application that works regardless of eruption stage is a genuinely useful answer to that problem.
Potassium iodide was used, which matters for what parents see
KI is applied after SDF specifically to reduce the black staining.
If you have been avoiding SDF anteriorly or in cooperative children because of appearance, the SDF+KI protocol is the one this trial used.
KI is applied after SDF specifically to reduce the black staining.
If you have been avoiding SDF anteriorly or in cooperative children because of appearance, the SDF+KI protocol is the one this trial used.
Fluoride varnish was not a straw man
It arrested two-thirds of lesions, which is a respectable result and worth saying to a family who declines SDF.
The choice is between good and better, not between something and nothing.
It arrested two-thirds of lesions, which is a respectable result and worth saying to a family who declines SDF.
The choice is between good and better, not between something and nothing.
⚠️ The catch
Six months is short, and the outcome is a surrogate
ICDAS 0 at six months is arrest by visual criteria, not a restoration avoided over years.
The durable question — do these teeth still avoid the drill at three years — is unanswered.
ICDAS 0 at six months is arrest by visual criteria, not a restoration avoided over years.
The durable question — do these teeth still avoid the drill at three years — is unanswered.
Early lesions only
Only ICDAS 1 and 2 lesions were analysed, out of 660 molars screened down to 139.
This says nothing about cavitated dentinal lesions in permanent molars.
Only ICDAS 1 and 2 lesions were analysed, out of 660 molars screened down to 139.
This says nothing about cavitated dentinal lesions in permanent molars.
Cluster randomisation at school level
Randomising schools rather than children means group differences can ride along with the school.
It is a practical design for a public-health trial and a real limitation on the estimate.
Randomising schools rather than children means group differences can ride along with the school.
It is a practical design for a public-health trial and a real limitation on the estimate.
⚡ Bottom line
- Early non-cavitated lesion on a first permanent molar → SDF outperforms varnish at six months.
- Molar only partly erupted → not a reason to wait. Eruption stage made no difference.
- Parent worried about black staining → this trial used SDF with potassium iodide.
- Cavitated dentinal lesion → outside this trial. Restore.
- Family declines SDF → varnish still arrested about two-thirds. Offer it.
🧪 Questions
Tap an answer — instant grade, deciding line, and the trap.
An 8-year-old has an ICDAS 2 occlusal lesion on a partially erupted lower first permanent molar. She is anxious, isolation is difficult, and a sealant would be hard to place reliably. Her mother asks what can be done today. Based on the 2026 randomised trial, what is the best-supported option?
Deciding line: SDF arrested 88% of early lesions versus 66% for varnish, and eruption stage had no significant effect, which makes this the specific scenario the trial was designed to address. Trap: the varnish option is the engineered trap because it states a plausible equivalence the trial specifically disproved; waiting for full eruption leaves an active lesion untreated through the highest-risk window, which is exactly the delay SDF exists to avoid.