When a tooth is lost from the back of the mouth, where nobody can see it, the temptation to leave the gap alone is entirely reasonable. Not replacing a missing tooth is sometimes a perfectly sensible decision, and I will say so when it is. But it helps to know what happens over the following years, because the changes are gradual and by the time they are obvious they are harder to put right.
On this page
- Neighbouring teeth drift
- The opposing tooth over-erupts
- Your bite changes
- Bone shrinks under the gap
- Chewing and the other side of your mouth
- When leaving the gap is genuinely fine
- If you do decide to replace it
- The bottom line
Neighbouring teeth drift
Teeth are not fixed in position. They sit in bone and are held in balance by the teeth around them, both the ones either side and the one they bite against.
Remove one from that arrangement and the balance goes. The teeth either side of the gap gradually tip and lean into the space, usually over years rather than months.
A tipped tooth is harder to clean around, since the angle creates new traps for plaque. So one missing tooth quietly increases the decay and gum disease risk for its neighbours.
The opposing tooth over-erupts
This is the change people find most surprising. The tooth in the opposite jaw, the one that used to bite against the missing tooth, no longer has anything to meet.
Teeth continue to erupt slowly throughout life until they meet resistance, so with nothing opposing it, that tooth gradually grows down or up into the space. Over years it can descend noticeably.
The consequence matters: if you later want to fill the original gap, the over-erupted tooth may now be occupying the space needed for a replacement. Sorting that out means either reducing the over-erupted tooth, which may then need a crown, or accepting a compromise. A straightforward replacement becomes a more involved plan.
Your bite changes
Drifting and over-eruption together alter how your teeth meet. Forces that were spread evenly across many teeth become concentrated on fewer, and those teeth wear faster, crack more readily, and put more strain on your jaw joints.
None of this is dramatic in year one. Over ten or fifteen years it can be substantial, and it is usually only noticed when something else goes wrong.
Bone shrinks under the gap
The bone that held the root is stimulated by that root. Once the tooth is gone, the bone in that area begins to shrink, fastest in the first year and more slowly thereafter.
For a single back gap this may never matter much. Where several teeth are lost, it changes the shape of the ridge, which affects how well a denture can be made to fit later. Our post on why dentures become loose explains that process.
Chewing and the other side of your mouth
Most people compensate for a gap without thinking about it, favouring the other side. That works well enough, but it means one side does more of the work, and over years that shows in wear.
Losing several teeth on one side also genuinely reduces chewing efficiency, which can quietly narrow what people eat.
When leaving the gap is genuinely fine
All of the above sounds alarming, so here is the balancing honesty: sometimes leaving a gap is a perfectly good decision.
It is often reasonable when:
- The missing tooth is the very last one in the arch, particularly a wisdom tooth or second molar, where there is no gap between teeth to drift into
- The opposing tooth has already been lost, so nothing can over-erupt
- You are chewing perfectly comfortably and the gap does not show
- Other treatment is a higher priority for your budget right now
What matters is that it is a decision rather than a default. Having it assessed lets you know which category your particular gap falls into.
If you do decide to replace it
The two options generally are a fixed bridge, which attaches to the neighbouring teeth, or a removable partial denture. Our post on choosing between a bridge and a denture compares them honestly, since neither is universally better.
Timing matters. Bone and gum change most in the months after an extraction, so permanent replacements are usually planned once healing has settled. Our post on what to eat after an extraction covers that early period, and our page on tooth extractions explains the treatment.
The important practical point is this: replacing a gap is simplest in the first year or two, before the neighbours have moved. Waiting a decade does not close the door, but it usually makes the plan bigger.
The NHS guidance on dentures has general background on replacing missing teeth.
The bottom line
Leaving a gap lets neighbouring teeth drift, the opposing tooth over-erupt, your bite redistribute and the bone shrink, all slowly. For an unseen back tooth with nothing opposing it, that may never matter. Elsewhere it usually does, and replacing sooner is simpler than replacing later.
If you have a gap and are unsure whether it needs filling, ring us on 01255 422506 for an honest opinion, including if the honest opinion is to leave it alone. Our post on what to do when a crown falls out covers another common way teeth get into trouble.
This article is general information rather than personal dental advice. Every mouth is different, so please speak to your dentist about your own teeth.
