Sensitivity after replacing an old amalgam: what should be reassessed?

Why a tooth can be sensitive after an amalgam is replaced

Replacing an old silver filling is more than swapping one material for another. The old amalgam is drilled out, decay or stained dentin beneath it is removed, the cavity is dried, and a bonded, tooth-colored material is placed in layers and hardened with a light. Each of those steps happens in dentin, the porous layer that sits directly over the nerve, so the nerve is often mildly irritated afterward. The American Association of Endodontists describes temporary sensitivity to hot or cold after dental treatment as a known effect of that irritation, one that usually settles over a few weeks.

The new filling also behaves differently from the old one. Bonded composite has to be placed on a tooth kept dry and isolated from saliva, and it shrinks slightly as it sets, which is one of the reasons composite placement is described as technique-sensitive. If the seal at the floor or the edges is incomplete, the tooth can feel cold or sweet more sharply than before; a defective or poorly sealed filling is a recognized cause of tooth sensitivity. None of this means the filling has failed, but it explains why a reassessment looks at the filling as well as the tooth. For the appointment itself, see what an amalgam replacement appointment involves.

What changes how long sensitivity lasts

The same procedure can produce no sensitivity in one tooth and weeks of it in another. The main differences usually include:

• How deep the old filling was. The closer the floor of the cavity sits to the nerve, the more the nerve tends to react, and the longer it can take to calm down.
• Whether decay had reached near the nerve. Decay found under an old amalgam can leave a thin layer of dentin over the pulp, and a nerve that was already inflamed by decay may take longer to recover, or may not recover.
• The material and how it was placed. Composite is bonded and light-cured in increments; moisture control during bonding and the way the layers are built up influence how well the dentin is sealed. A systematic review of adult patients with posterior composite restorations found post-operative sensitivity to be a recognized complication, and the type of bonding strategy used did not significantly change how often it occurred.
• Whether the tooth already had a crack. Teeth that have carried a large amalgam for years sometimes have cracks that were hidden under the old filling. A crack can cause chewing pain and temperature sensitivity that the new filling did not create but also cannot cure.
• Grinding or clenching. Grinding or clenching puts heavy, repeated force on teeth, and a dentist may ask about it when a freshly restored tooth is slow to settle.
• Your general sensitivity history. Teeth that were already sensitive to cold because of recession or worn enamel often stay that way, and the new filling may be blamed for an older problem.

Patterns that usually settle, and patterns that deserve a call

The pattern matters more than the presence of sensitivity.

A short cold twinge that fades

A quick zing with cold water or ice cream that disappears within seconds once the cold is gone is a common pattern after a deep filling. The AAE notes that momentary sensitivity to hot or cold usually does not signal a serious problem when the discomfort lasts only moments. If it is the same or milder each week, it is usually settling. Note it, and mention it at your next visit.

Tenderness when you bite in one spot

A new filling that sits slightly high can change how the teeth meet, so the restored tooth may take extra force each time you close. A high spot often shows up as a bruised feeling when you chew in one spot, sometimes with new cold sensitivity. Pain on biting after a filling has several possible causes, including a high spot, a loose or poorly sealed filling, or a crack, which is why a bite check comes first. It is a common and usually straightforward reason for a reassessment, and it is worth calling the office about rather than waiting for it to settle.

Sharp pain when you release your bite

Pain that comes as you let go of something you have bitten, rather than as you press down, is a pattern the AAE associates with a crack. Chewing moves the cracked segments and irritates the pulp, and when the pressure is released the crack closes quickly and causes a sharp pain. Cracks are often hard to see on an X-ray, so the symptom itself is the clue. This deserves a prompt reassessment; see the cracked-tooth clue.

Sensitivity that lingers or starts on its own

Cold pain that stays for a long time after the cold is gone, an ache that starts without any trigger, or pain that wakes you at night point to a nerve that is significantly inflamed rather than merely irritated. Endodontic diagnosis separates a pulp that reacts and recovers quickly (reversible pulpitis) from one with lingering or spontaneous pain (irreversible pulpitis), and the second usually does not recover with time. This needs an appointment soon, not a wait-and-see approach. Read cold sensitivity that lingers before you call so you can describe it precisely.

Swelling, fever or a bad taste

Gum swelling next to the tooth or a bad taste can point to infection rather than ordinary postoperative sensitivity. Contact a dentist promptly. Fever with facial swelling is an emergency: call 911 or go to the nearest emergency department. If swelling is spreading or you have any difficulty breathing or swallowing, see the emergency section below first.

What a reassessment can involve

A reassessment is mostly testing rather than treatment, and the usual sequence is simple first, complex later.

• The bite check. The dentist marks the way your teeth meet and looks for a high spot on the new filling. If the filling is high, the dentist can adjust it; biting tenderness caused by a high spot often improves after the adjustment, and the tooth is then rechecked to see whether any cold sensitivity settles.
• The edges and the bond. The margins of the filling are examined for open edges, excess material or a gap. A filling with a defective edge or an incomplete seal may be repaired or replaced.
• Nerve and bite tests. A cold test on the restored tooth and on a neighbor for comparison shows whether the nerve responds normally, responds and lingers, or does not respond. Tapping the tooth and biting on an instrument help locate the source and separate pulp inflammation from a crack or a bite problem.
• An X-ray when indicated. An X-ray can show how close the filling sits to the nerve, whether decay remains, and whether there is any change at the root tip, although cracks and early pulp inflammation often do not show on an X-ray.
• A look for cracks. The dentist looks closely at the tooth, often under magnification, and repeats the bite test; because cracks are often invisible on X-rays, the symptom pattern and these tests are usually what identify them. If a crack is found, the tooth may need a restoration that holds the cusps together rather than a repeat filling.
• If the nerve is irreversibly inflamed. When tests show the pulp cannot recover, the dentist will discuss root canal treatment, in which the inflamed or infected pulp is removed, the inside of the tooth is cleaned and sealed, and the tooth is then restored. This is routine, evidence-based care intended to save the tooth, and it is sometimes the outcome for a tooth whose nerve was already compromised by deep decay before the old filling was touched. The practice does not promise that a replacement will avoid a root canal or a crown; the state of the nerve decides that.

Your symptom record shortens all of this: whether the pain follows cold or biting, how long it lasts and whether it is improving tells the dentist where to start. See also why one tooth hurts when you bite.

Safe measures meanwhile

• Chew on the other side. Avoid hard, sticky or very cold foods on the restored tooth until it is reassessed.
• Lukewarm rather than hot or icy. Temperature extremes are common triggers for an irritated nerve.
• A desensitizing toothpaste, as directed on the label. Toothpastes made for sensitive teeth can reduce the response to cold with regular use, although it usually takes several applications before any change is noticed; ask the dentist which to choose.
• Over-the-counter pain relief only as directed on the label. Pain relievers sold without a prescription can help short term, but some are unsuitable with certain medical conditions or medications, so check with your physician or pharmacist first. The label and your clinicians, not this page, set the dose.
• Do not wait out worsening pain. Pain that is escalating, lingering longer or waking you is a reason to call, not to add more pain reliever.

When to go to emergency care instead

Breathing or swallowing difficulty, rapidly spreading facial or neck swelling, fever with facial swelling, uncontrolled bleeding or severe trauma go to emergency care: call 911 or go to the nearest emergency department. Do not use the appointment request form for these, and do not drive to a dental office first. Medical care comes first in those situations because the airway and the spread of infection matter more than the tooth. For severe tooth pain without those warning signs, tooth pain tonight lists the details that help a dentist decide urgency.

The next step

Fill in the symptom record below for a few days, then call Loul Dental Studio during office hours, Monday to Thursday 8:00 am to 5:00 pm, at (805) 565-5111 with the date of the replacement, which tooth it is, what sets the pain off and how long it lasts. Ask the office how it prefers post-treatment concerns to be reported, since the online appointment request page is a request rather than a confirmed visit. If the filling was placed elsewhere, bring any X-rays or notes you have; a reassessment is easier when the dentist knows how deep the old filling was.