Dentists fix tooth decay differently depending on how far it has progressed, ranging from non-invasive treatments that can reverse early damage all the way to root canals for deeply infected teeth. The approach your dentist recommends depends on whether the decay is still in the outer enamel layer, has reached the softer inner layer called dentin, or has spread to the nerve and blood supply deep inside the tooth.
How Dentists Assess the Damage
Before any treatment begins, your dentist needs to determine how deep the decay goes. They use a standardized scoring system that runs from 0 (healthy tooth) to 6 (extensive cavity covering more than half the tooth surface with visible dentin). At the lower end, codes 1 and 2 represent changes visible only as white or brown spots on the enamel, often detectable only after the tooth is dried with air. Code 3 means localized enamel breakdown without signs that the decay has reached dentin. By codes 4 through 6, the decay has penetrated deeper, with visible cavities and compromised tooth structure.
Your dentist spots these signs through a combination of visual examination, poking with a small explorer instrument, and dental X-rays that reveal decay hidden between teeth or beneath the surface. Where the decay falls on this scale determines everything about what happens next.
Reversing Early Decay Without Drilling
When decay is caught early, while it’s still limited to the enamel and hasn’t formed an actual cavity, it can sometimes be reversed rather than filled. At this stage, the damage shows up as chalky white spots or slight discoloration on the tooth surface. The mineral structure of the enamel is weakened but not yet broken through.
Professional fluoride treatments are the most common first step. Your dentist applies a concentrated fluoride varnish or gel that helps the enamel absorb minerals back into its structure, a process called remineralization. This essentially repairs the weakened enamel before a cavity forms. At home, you support this with fluoride toothpaste and possibly a prescription fluoride rinse.
Silver diamine fluoride (SDF) is a newer option that the American Dental Association first recommended in 2018. It’s a liquid painted directly onto the affected area, requires no drilling, no numbing, and takes seconds to apply. SDF is effective at arresting decay at multiple stages, from initial enamel changes through actual cavities. It’s painless and inexpensive, making it particularly useful for young children or anyone anxious about dental procedures. The main drawback: it permanently stains the treated area black, so it’s used more often on baby teeth or less visible surfaces.
Fillings for Moderate Cavities
Once decay breaks through the enamel and creates an actual hole in the tooth, the damaged material needs to be physically removed and replaced. This is where the classic “filling” comes in, and it’s the most common fix for tooth decay.
Your dentist starts by numbing the area with a local anesthetic, typically lidocaine, which takes effect within 2 to 4 minutes. You’ll feel pressure but no pain. Using a high-speed drill (or sometimes a laser), they remove all the decayed tooth material until only healthy structure remains. The cavity is then cleaned, shaped, and filled with a restorative material.
You have two main filling options for back teeth. Composite resin is tooth-colored and blends in visually. Amalgam is the traditional silver-colored material. Each has trade-offs worth understanding.
- Amalgam fillings last longer on average, with median survival times exceeding 16 years. They tend to fail from fracture, often in people who grind their teeth. They’re durable and less sensitive to the quality of your home care, but they’re conspicuous and some patients prefer to avoid them for cosmetic reasons.
- Composite resin fillings match your tooth color and have a median survival of about 11 years. Their most common cause of failure is new decay forming around the edges of the filling, a risk that’s about 3.5 times higher than with amalgam. Poor oral hygiene makes composite fillings fail faster, while amalgam is more forgiving.
At the five-year mark, both materials perform similarly. The gap in durability becomes more apparent over a decade or longer. For front teeth, composite is the standard choice since appearance matters more there. For back teeth, the decision often comes down to whether you prioritize longevity or aesthetics.
Crowns and Onlays for Larger Damage
When decay destroys a significant portion of a tooth, a standard filling may not provide enough structural support. Dentists generally recommend a full crown when more than 50% of the tooth structure is lost. For damage that falls between a filling and a crown, an onlay (sometimes called a partial crown) covers one or more of the tooth’s cusps, the raised points on the biting surface, without capping the entire tooth.
An onlay is typically recommended when the cavity is wide enough that it spans more than half the distance between the outer and inner cusp tips, or when one or more cusps are weakened. Think of it as a custom-fitted cap for the damaged portion. A full crown wraps around the entire visible part of the tooth, providing maximum protection for severely compromised teeth.
Both options require two visits in most cases. At the first appointment, your dentist removes the decay, shapes the remaining tooth, takes impressions or digital scans, and places a temporary restoration. The permanent crown or onlay is fabricated in a dental lab and cemented into place at the second visit, usually one to three weeks later. Some offices have same-day milling technology that can produce a crown in a single appointment.
Root Canals for Deep Infections
When decay reaches the pulp, the soft tissue inside the tooth containing nerves and blood vessels, the tooth often becomes intensely painful. At this point, the infection needs to be cleared from inside the tooth to save it. That’s what a root canal does.
The procedure is more involved than a filling but follows a logical sequence. After numbing the area, your dentist or a root canal specialist (endodontist) places a small rubber sheet around the tooth to keep it dry and clean. They create a small opening in the top of the tooth to access the pulp chamber, then use tiny instruments to remove the infected tissue from the pulp and the root canals that extend down into your jawbone. The inside of the tooth is thoroughly cleaned and disinfected, then filled with a rubber-like material that seals the empty space. A temporary filling closes the opening.
You’ll return for a permanent crown at a later visit, since a tooth that’s had a root canal loses its internal blood supply and becomes more brittle over time. The crown protects it from fracturing. Most people report that a root canal feels similar to getting a filling, just longer. The procedure typically takes 60 to 90 minutes.
Laser Treatment as an Alternative to Drilling
Some dental offices now offer laser-assisted cavity preparation as an alternative to the traditional drill. A meta-analysis covering more than 2,200 treated teeth found that lasers significantly reduce pain during the procedure. Patients treated with lasers were about 70% less likely to need anesthesia and roughly 65% less likely to report pain compared to those treated with conventional drills.
The finished results are comparable. Restoration survival rates and the health of the tooth’s nerve were not significantly different between laser and drill-prepared cavities. The main downside is time: laser preparation takes meaningfully longer per tooth, averaging a couple of extra minutes. Not every cavity is suitable for laser treatment, and the technology isn’t available in all practices, but it’s a legitimate option if you’re particularly anxious about the drill or want to avoid numbing injections.
What to Expect After Treatment
After a filling, some sensitivity to hot, cold, or pressure is normal and typically fades within a few days to a week. The numbness from anesthesia wears off in 3 to 5 hours for standard lidocaine, though your dentist may use a longer-acting option for more extensive work that can last up to 9 hours. Be careful not to bite your cheek or tongue while you’re still numb.
During the first week, stick to lukewarm foods and drinks, brush gently around the treated area with a soft-bristled toothbrush, and consider a desensitizing toothpaste if sensitivity lingers. If your bite feels uneven when you close your jaw, call your dentist. The filling may be slightly too high and need a quick adjustment, which takes just a minute or two and usually requires no anesthesia. Sensitivity that worsens rather than improves, or lasts beyond two weeks, may indicate that the decay was close to the nerve and further treatment is needed.