Dental Literature Watch · Trial · Cariology
SDF Arrests Root Caries — 85% vs 21%, and Plaque Is the Modifier
TL;DR
- Lesion-level arrest 84.9% with SDF versus 20.7% with control (p < 0.001). At participant level, 81.2% versus 21.3%.
- Adjusted odds ratio for SDF application: 26.1. That is an unusually large effect for any dental intervention.
- Three factors predicted arrest: SDF application (AOR 26.1), lesion status at baseline (AOR 6.88), and absence of plaque on the lesion surface.
- Control arm was tonic water — an honest placebo rather than another active agent.
- Follow-up was only two months. That is the main limitation, and the reason this is a 4 and not a 5.
The study
| Design | Two-arm parallel randomised controlled trial |
| Population | 186 participants — 93 SDF (165 lesions), 93 control (158 lesions). 87% of lesions active, 53% posterior, 91% single-surface |
| Intervention | 38% SDF vs tonic water control |
| Follow-up | 2 months; 165 participants (88.7%) with 286 lesions completed |
| Result | Arrest 84.9% vs 20.7% at lesion level; 81.2% vs 21.3% at participant level |
| Predictors (GEE) | SDF (AOR 26.12), baseline lesion status (AOR 6.88), absence of plaque on the lesion |
💎 Insight — what this means chairside
Root caries is the problem that grows as your practice ages
More retained teeth, more recession, more xerostomia from medication.
Restoring root caries is technically miserable — subgingival margins, moisture control, poor access — which makes a non-operative option genuinely valuable rather than merely convenient.
More retained teeth, more recession, more xerostomia from medication.
Restoring root caries is technically miserable — subgingival margins, moisture control, poor access — which makes a non-operative option genuinely valuable rather than merely convenient.
The plaque finding is the actionable one
Absence of plaque on the lesion surface independently predicted arrest.
So SDF is not a substitute for cleaning the lesion and improving home care around it — it works better when you do both.
Absence of plaque on the lesion surface independently predicted arrest.
So SDF is not a substitute for cleaning the lesion and improving home care around it — it works better when you do both.
An odds ratio of 26 is not a subtle signal
Most dental interventions argue over a few percentage points.
When the control arm arrests one lesion in five and the treatment arm arrests four in five, you do not need a statistician to interpret it.
Most dental interventions argue over a few percentage points.
When the control arm arrests one lesion in five and the treatment arm arrests four in five, you do not need a statistician to interpret it.
⚠️ The catch
Two months is a very short follow-up
Arrest at two months is an early snapshot, and root caries is a chronic disease in patients whose risk factors do not change.
Reapplication interval, durability, and how often lesions reactivate are all unanswered here.
Arrest at two months is an early snapshot, and root caries is a chronic disease in patients whose risk factors do not change.
Reapplication interval, durability, and how often lesions reactivate are all unanswered here.
Staining is not addressed in this design
Unlike the permanent molar trial, potassium iodide is not part of this protocol as reported.
SDF blackens arrested lesions, and on an exposed root surface in an anterior sextant that is a conversation to have before you apply it.
Unlike the permanent molar trial, potassium iodide is not part of this protocol as reported.
SDF blackens arrested lesions, and on an exposed root surface in an anterior sextant that is a conversation to have before you apply it.
Tonic water as control tells you about SDF, not about alternatives
The comparison is against effectively nothing, so this trial does not tell you whether SDF beats a high-fluoride varnish or a prescription dentifrice on the same lesions.
The comparison is against effectively nothing, so this trial does not tell you whether SDF beats a high-fluoride varnish or a prescription dentifrice on the same lesions.
⚡ Bottom line
- Active root caries in an older adult → SDF arrests roughly four in five lesions at two months.
- Before applying → clean the lesion. Plaque-free surfaces arrested better.
- Anterior root surface → discuss blackening first; it is permanent on the arrested lesion.
- Subgingival margin, poor access, medically complex patient → this is the case where non-operative management earns its place.
- Planning recall → the trial cannot tell you the reapplication interval. Follow the fluoride position statements and reassess at six months.
🧪 Questions
Tap an answer — instant grade, deciding line, and the trap.
A 78-year-old woman on four xerostomic medications has three active root caries lesions on the buccal surfaces of lower premolars, all single-surface and non-cavitated. Access is reasonable but she tires quickly in the chair and has a tremor. Based on the 2026 randomised trial, which is best supported as the immediate intervention?
Deciding line: SDF arrested about 85% of root caries lesions versus 21% for control, and absence of plaque on the lesion surface was an independent predictor of arrest, so cleaning first and then applying is the protocol the evidence supports. Trap: the last option is the engineered trap because it takes the right agent and discards the one modifiable factor the study identified; restoring three subgingival-margin lesions in a frail patient with a tremor is the operative reflex that this evidence gives you a defensible alternative to.