You are sure that this tooth has already been “treated.” After all, you came to the clinic, went through the treatment, had a filling done a few years ago and completely forgot about it. But suddenly, out of nowhere, it starts signaling to you with sensitivity to cold or a dull, troubling pain.
As a practitioner who sees many patients at my clinic in Haifa, I encounter this scenario a lot. It is one of the most elusive situations in dentistry – a phenomenon called “secondary caries.” Let’s understand exactly what it means, and why a filling is not always a lifelong solution.
What Happens Under the Filling?
Fillings (restorations, in professional terms) are meant to seal the tooth after we have cleaned the bacteria out of it. But it is important to understand that filling materials – no matter how strong they are – are under enormous daily load from chewing, teeth grinding, the acidity of saliva and food, and temperature changes (hot coffee, cold ice cream).
Over the years, filling materials can wear down, shrink slightly, or crack. The moment that happens, a microscopic gap is created – a tiny crack – between the filling material and the natural tooth structure. The bacteria in our mouth recognize this opportunity, penetrate underneath the old filling, and start digging a “new cavity” there. We call this secondary caries.
Why Is Secondary Caries So Dangerous?
The greatest danger of secondary caries is that it develops in the dark. Unlike a regular cavity that can sometimes be seen or felt in the early stages, here the bacteria work under the radar (and under the filling).
By the time you start feeling pain, the new cavity may already be very deep and approaching the dental pulp (the nerve). In such cases, simply replacing the filling may not be enough, and we may have to move on to root canal treatment in order to save the tooth.
How Do We Catch It in Time?
I, Dr. Anton Gurevich, believe that good dentistry is first and foremost preventive medicine. The only way to catch secondary caries while it is still small is through routine check-ups and X-rays.
- Clinical examination: During a careful examination at the clinic, I check the margins of your old fillings to make sure they are still sealed and intact.
- X-ray: The X-ray allows me to see “through” the tooth and identify dark shadows under existing fillings – a clear sign that bacteria have penetrated inside.
What Is the Correct Treatment?
If we detect secondary caries at an early stage, the treatment is simple and straightforward: I carefully remove the old and damaged filling, thoroughly clean the bacteria and the new decay that formed underneath it, and reseal the tooth with a new, strong and durable filling.
The best tip I can give you? Don’t wait for pain to wake you up. Ongoing maintenance and regular visits to the clinic are your best protection against unpleasant (and expensive) surprises under old fillings.
Sources
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A systematic review and meta-analysis (Brouwer et al., 2016) examining methods for detecting secondary caries lesions around restorations and fillings, and highlighting early detection challenges.
Detecting secondary caries lesions: a systematic review – PubMed (Brouwer et al., 2016) -
A comprehensive review (Askar et al., Clinical Oral Investigations 2020) defining secondary caries as a lesion associated with restorations or sealants, highlighting detection challenges, key risk factors (gaps, patient caries risk, operator experience), and management options (repair of the defective part or complete replacement).
Secondary caries: what is it, and how it can be controlled, detected, and managed? – Clinical Oral Investigations
The information in this article is intended for educational purposes only and does not constitute a substitute for personal medical advice. It is recommended to consult a qualified physician before making any treatment decision.