Dr. Douglas A. Young on Silver Diamine Fluoride, SDF, SMART, and Minimally Invasive Dentistry
A patient sits in the chair with a cavitated lesion, and for generations the next step in dentistry was almost automatic. Remove the decay, prepare the tooth, restore what was lost. Douglas A. Young, DDS, EdD, MS, MBA, has spent much of his career challenging that reflex. His argument is not that dentists should stop restoring teeth. It is that caries is a disease process before it is a hole, and treatment should begin with lesion activity, depth, pulpal status, patient risk, cleansability, function, esthetics, and whether a less invasive intervention can predictably control the disease.
That idea once sounded disruptive. Today, much of it is mainstream. Young helped develop the American Dental Association Caries Classification System, which moves diagnosis beyond a simple yes or no determination of decay. Lesions are considered from sound to initial, moderate, and advanced disease, with attention to whether they are active or arrested. A matte, rough, active lesion is not biologically equivalent to a shiny, hard, arrested one, and a radiolucency does not automatically dictate how much tooth structure should be removed.
The ADA moved further in the same direction with its 2023 restorative caries guideline, which supports selective caries removal in many moderate and advanced lesions rather than routine complete excavation. Preserve sound structure, maintain pulpal vitality when possible, obtain a durable seal, and remove only as much tissue as the clinical situation requires.
Silver diamine fluoride fits naturally into that philosophy because it gives the dentist an option between watching a lesion and immediately restoring it. Young has been one of SDF’s most visible advocates in the United States, particularly for 38 percent SDF. The strongest evidence now supports much of that enthusiasm.
A major NIH funded phase III randomized clinical trial published in JAMA Pediatrics in 2026 enrolled 830 children with severe early childhood caries. At six months, 54.0 percent of lesions treated with 38 percent SDF were arrested, compared with 22.5 percent treated with placebo. After a second application at six months, the eight month figures were 50.2 percent versus 17.4 percent. Treatment related adverse events were similar between groups. That is a meaningful treatment effect, but it also reminds dentists that SDF is not magic.
The World Health Organization strengthened the case in 2026 by strongly recommending 38 percent SDF twice yearly for cavitated lesions without pulpal involvement in primary teeth and for cavitated root surface lesions in permanent teeth. WHO rated the recommendation strong, with moderate certainty of evidence. The therapy is well supported, but the evidence is not perfect.
This is where dentists should resist seductive headline numbers. Young’s 2021 clinical instructions cited earlier evidence suggesting arrest rates around 81 percent with semiannual application. Other studies have produced lower values. Effectiveness depends on tooth type, lesion location, access, plaque control, application frequency, population, follow up, and how arrest is defined. There is no single SDF success rate that belongs on every consent form.
Technique is also less settled than the philosophy. Young and colleagues recommended allowing SDF to absorb for at least one minute, a sensible protocol based on available evidence and expert consensus. A 2025 randomized trial estimated roughly 80 percent arrest at 16 seconds and 84 percent at 60 seconds. That does not establish a new universal protocol. It shows why a practical technique should not become dogma.
The distinction between arrest and prevention matters too. Evidence for arresting selected cavitated lesions is stronger than evidence for using SDF broadly on sound or noncavitated high risk surfaces. WHO reflects that difference, giving SDF a strong recommendation for selected cavitated lesions while the broader evidence for preventive applications remains less certain.
Patient communication may matter as much as chemistry. The strongest explanation is not, this liquid stops cavities. It is, this treatment may arrest an active cavity without drilling, but we still need to monitor the tooth and decide whether it requires restoration for anatomy, contact, cleansability, strength, function, or appearance. That also prepares the patient for SDF’s obvious tradeoff, carious tissue commonly turns black. For a posterior primary tooth, an elderly root lesion, or a frightened child facing sedation, that may be acceptable. On an anterior permanent tooth, it may determine the decision entirely.
Young also promotes SMART, silver modified atraumatic restorative treatment, which combines SDF with glass ionomer cement. The logic is attractive. SDF can alter the lesion, selective excavation preserves dentin, and glass ionomer can restore anatomy in situations where moisture control or cooperation is difficult.
But SMART demonstrates why biological plausibility should not be confused with proven superiority. A 2026 systematic review and meta analysis of six randomized clinical trials found no statistically significant difference in overall clinical success between SMART and conventional atraumatic restorative treatment in primary teeth. The certainty of evidence was low and the cumulative evidence remained inconclusive. SMART appears useful. It has not yet earned the stronger claim that it is better.
Glass ionomer deserves the same calibrated respect. Young values it because it releases fluoride, chemically interacts with tooth structure, and performs well in some moisture challenged situations. Those are legitimate advantages. They do not mean glass ionomer should replace resin composite across the board. Material choice still depends on tooth, surface, isolation, occlusal load, patient risk, esthetic expectations, and the dentist’s ability to create a durable restoration.
There is also a practice management implication. A 2023 JADA retrospective cohort study of 175,824 privately insured young children found that SDF use was associated with a 63 to 91 day longer interval before sedation or general anesthesia among children who ultimately received it. The study did not prove that SDF prevented anesthesia. It suggests that SDF can sometimes buy time.
For a three year old, time can matter. Cooperation can improve, families can consider options, and the practice can avoid forcing complex dentistry into one high stress visit. But delay has value only when disease remains controlled. Pain, infection, pulpal involvement, nonrestorable teeth, and progression still demand definitive care.
The practical conclusion is simple. Do not replace one reflex with another. The old reflex was, I see decay, therefore I drill. The new reflex should not become, I see decay, therefore I apply SDF. Diagnose the lesion, determine whether it is active, assess the pulp and the patient, decide what anatomy and function must be restored, and choose the least invasive treatment that can predictably accomplish those goals.
Young’s most durable contribution may not be SDF itself. It may be pushing dentistry to ask a better question before touching the handpiece. Not, can I restore this tooth, but what does this tooth actually need from me today?
Are we still treating caries as a hole to be filled, or as a disease to be managed?
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