The questions above reorder this list around your situation. Here it is in full, because the questions worth asking do not really depend on which of them applies to you.
Swelling changes the order of things
Swelling in the gum or face means the priority is settling the infection, not deciding the long-term plan. That decision keeps. Arrange to be seen promptly, and if the swelling is spreading, affecting your eye or the floor of your mouth, or you cannot swallow or open normally, treat it as an emergency rather than an appointment.
Urgent dental carePain that arrives on its own is a different question
Sensitivity that follows something cold and then fades behaves differently from an ache that starts unprompted or wakes you at night. The second pattern usually means the nerve itself is involved rather than merely irritated, and that narrows the options in a way the first does not. It is also the pattern least worth waiting out, because discomfort settling on its own does not reliably mean the problem has.
When a root canal is the answerPain on biting, on a tooth already treated, is its own finding
A sharp pain on biting, especially as you release, behaves differently from decay pain. On a tooth that already carries a crown or a root filling, it usually means asking what is happening underneath the existing work rather than adding something further on top of it.
Sharp pain on bitingAsk whether a crack has been looked for specifically
Biting pain in a tooth with no crown and no root filling raises a crack as a possibility, and cracks are not reliably visible on a standard film. They are usually found by testing cusps individually and by looking under magnification, which is a deliberate step rather than something that turns up on its own.
Can a cracked tooth heal?Sensitivity that settles is not automatically decay
A brief reaction to cold or sweet that stops when the stimulus goes has several causes. Exposed root surface, a worn area at the gum line and a leaking margin all produce it, and they are managed differently from one another. The useful question is which of them is producing it here, rather than how soon it should be filled.
Why cold hurtsNo symptoms is information, not just the absence of a problem
A tooth that does not hurt can still need work, and plenty of serious findings are silent. But when something substantial is proposed for a tooth that is not complaining, it is fair to ask what specifically prompted it, and to be shown that finding rather than told about it. Silent problems are visible on an image, which is how they get found in the first place.
Ask how far below the gum the damage actually goes
Broken at or below the gum line is the point at which many teeth get written off, and the distance from that edge to the bone is what actually decides it. Some of those edges can be lifted back to a level that can be sealed and cleaned; others need a small amount of tissue moved instead. Both routes exist precisely so these teeth can be kept.
Broken below the gumAsk how much wall is left to hold the restoration
When very little tooth stands above the gum, what matters is not only how the restoration is made but what it will grip. A continuous band of remaining wall behaves better than none, and even a partial band behaves better than none at all. So the question is what is actually still there, rather than whether the plan sounds thorough.
Ask whether a partial covering would do
A crown covers the whole tooth, which means reducing all of it. An inlay or onlay covers only the part that is missing or unsupported. When a good amount of wall is still standing, that difference is the whole argument, and it is measurable rather than a matter of taste.
Inlays and onlaysAsk what makes this one unrestorable
Some teeth genuinely cannot be kept: a root split lengthways is the clearest example, and no technique changes that. But when a good part of the tooth is still standing, it is fair to ask which specific finding puts it in that category, and to have it shown to you.
When a tooth can be keptHow much is left is measurable, and worth knowing
Not knowing is completely reasonable, because an old filling can make a tooth look whole from above while very little sound wall remains underneath it. The honest version of this answer only appears once the old material and any decay are cleaned out, which is why a definite plan made before that point is really a provisional one.
A second root canal is retreatment, and that is a different decision
Being told a root-filled tooth needs a root canal means the first one is being revisited, not started. That is a genuinely different conversation, with its own success rates and its own reasons for failing, and the useful question is what is thought to have gone wrong the first time. Retreatment and extraction are also not the only two options on the table.
Root canal retreatmentAsk whether the nerve has been tested
A tooth that does not ache on its own, or that only reacts briefly to cold, may still have a nerve worth keeping. Vitality testing and the depth of the decay decide that, not the size of the shadow on the film. Where the nerve is still healthy, sealing it rather than removing it is sometimes possible.
What pulp capping can doA root canal that has not settled is not automatically an extraction
When a root-filled tooth keeps causing trouble, extraction is one answer among several. Retreating the original root filling, and a small surgical procedure at the root tip, both exist for exactly this situation. Which of them applies depends on why it is failing, so that is the thing worth establishing before agreeing to lose the tooth.
When a root canal has not settledReplacing is not the only option for a failing filling
Each time a restoration is replaced the cavity gets a little larger, because the old material and some sound tooth around it both come out. Where the problem is confined to one margin, repairing that margin rather than replacing the whole thing keeps the tooth bigger for longer.
Conservative fillingsGoing straight to full coverage on a tooth's first restoration
A tooth that has never been filled starting at a crown is worth a question, because it skips every smaller step in one move. Sometimes that is right, when a cusp has already gone or a crack runs across the tooth. Sometimes the same tooth would have been served by something that removes far less. The finding that rules out the smaller option is the thing to ask for.
The case for onlaysAsk why the existing crown is being replaced
A crown being replaced is usually a symptom of something underneath rather than a problem with the crown itself: decay at the margin, a fracture in the remaining tooth, or a root that has become involved. Replacing the covering without establishing which of those it is tends to produce the same conversation again a few years later.
Replacing existing workAsk where the edge of the filling will sit
For a filling the useful questions are narrow ones: how deep the decay goes, whether the edge will finish on enamel or below the gum, and whether the tooth can be kept dry while it is bonded. Those three decide how long it lasts far more than the choice of material does.
How fillings are done hereNothing has been proposed yet, which is the easiest place to be
Arriving before a plan exists means the assessment can be done without a decision already attached to it. What that should include is a look at the whole mouth rather than the one tooth, images that are shown to you and explained, and an answer that separates what needs attention now from what can reasonably be watched.
What an examination coversA plan made without an image is a plan made without the evidence
Most of what decides these questions sits where the eye cannot reach: between the teeth, under an existing filling, and around the root. Being told what a tooth needs when no image has been taken is worth pausing on, because the three questions below cannot be answered from the surface alone.
Ask to see the images, and ask for a copy
They are your medical records. Being shown the film and having the finding pointed out on it is a normal part of consent, not a favour. They also travel: a second look is far more useful when the images come with you rather than being taken all over again.
Three questions that change the answer
How much healthy tooth is actually left, once the decay is cleaned out? Where does the edge of the damage sit relative to the bone? And is there a smaller option than the one being proposed. Those three answers decide most cases, and all three are reasonable to ask before agreeing to anything.
Before anything irreversible
Cutting a tooth down and taking one out are both permanent. A second look costs you time and nothing else, and it is a normal thing to ask for rather than a discourtesy.
A second opinion