Can a Wisdom Tooth Cause Decay in the Tooth Next to It?
Yes. A wisdom tooth can cause decay in the tooth next to it, usually the second molar directly in front of it. When a wisdom tooth comes through at an angle, or only partway, it traps food and plaque in a narrow gap that a toothbrush cannot clean. Decay then forms on that hidden surface of the neighbouring tooth. According to our Brisbane Dentists, in the early stages, there may be no pain at all, so it is commonly picked up on a routine dental X-ray before it is ever felt.
The Wisdom Tooth That Was Causing Decay in the Tooth Next to It
A patient came to us for a routine examination with no pain and no complaint about her wisdom teeth at all. The one at the lower left had sat there for years without a flicker of trouble. That was the trap. Tucked in behind it, out of reach of any toothbrush, it had been trapping food against the molar in front and slowly decaying it. On the scan, the damage had already reached deep. The wisdom tooth that never hurt had done real harm to the tooth it leaned on. The wisdom tooth felt fine. The tooth beside it was the one paying the price.
How Wisdom Teeth Cause Decay in Neighbouring Teeth
A wisdom tooth may cause decay in the tooth next to it by opening up a trap that food and plaque get pushed into, and a toothbrush simply cannot reach. The decay that follows lands not on the wisdom tooth, but on the healthy tooth in front of it.
Here is how it happens. A wisdom tooth is the last tooth at the very back of the jaw, and the last to arrive, usually in the late teens or twenties. When there is not enough room for it, it often comes through at an angle or only part of the way, leaning against the second molar in front instead of standing upright beside it. That lean leaves a narrow gap where the two teeth meet. Food and plaque pack into the gap and stay there, because the surface of the second molar facing the wisdom tooth sits at or below the gumline, behind the reach of a brush and floss. Plaque left sitting on a tooth makes acid, and over time, that acid eats through the enamel and starts a cavity on that one hidden surface.
The catch is where the damage shows up. When we examine a mouth like this, the wisdom tooth is often perfectly intact, while the good tooth it leans on is the one being slowly hollowed out on the side no one can see. That is exactly what we found in the case above. The wisdom tooth had never caused a symptom, yet the molar beside it had been quietly decaying against it for some time.
The Problems Wisdom Teeth Can Cause to the Rest of Your Mouth
Beyond decay in the tooth next to it, a wisdom tooth may cause several other problems: gum infection, bone loss, damage to a neighbouring root, a cyst, and everyday issues like food packing and bad breath. Decay in the tooth in front is where this story started, but it is not the only thing we look for. Not every wisdom tooth causes these, and many cause none at all, so the list below is what may happen.
- Decay in the tooth in front: This is the one we started with, and it is among the most common problems a wisdom tooth causes. The angled or partly through wisdom tooth traps plaque against the second molar, and a cavity forms on the hidden surface that cannot be cleaned. It is usually painless early on, which is why it often goes unnoticed until it shows up on an X-ray.
- Gum infection around the wisdom tooth (pericoronitis): When a wisdom tooth is only part of the way through, a flap of gum sits over it, and food and bacteria collect underneath. That gum can become swollen, sore and infected, often with a bad taste and trouble opening wide. It tends to settle and then flare up again, and the flare-ups usually keep returning until the cause is dealt with.
- Bone loss behind the second molar: The same trap that starts decay also lets gum disease take hold in a spot that is hard to clean. Over time, this can form a deep pocket and destroy some of the bone at the back of the second molar. Once that bone is lost, it does not grow back, so the tooth in front can be weakened even if it never decays.
- Damage to the neighbouring tooth’s root: A wisdom tooth pressing against the tooth in front may, in some cases, wear away or damage the root of that tooth. This is less common, but it is serious because a damaged root is hard to repair and can lead to a lost tooth. It often causes no symptoms and is picked up only on imaging.
- A cyst around a buried wisdom tooth: A wisdom tooth that stays fully buried in the jaw may occasionally develop a fluid-filled sac, called a cyst, around it. This is uncommon and usually painless, so it is generally found by chance on an X-ray rather than because it is felt. Left alone, a cyst can slowly enlarge and affect the surrounding bone and nearby teeth.
- A neighbour that ends up needing treatment of its own: These problems rarely stay small if they are left. Depending on how far the decay or damage has gone, the tooth in front may move from needing a simple filling to needing a root canal, and in the worst cases, it may have to be removed. Put simply, a wisdom tooth’s hidden effect can end up costing a second, otherwise healthy tooth.
- The everyday nuisances: Not every problem is dramatic. A wisdom tooth that packs food, or one that tilts into the cheek, may cause ongoing food trapping, bad breath, or repeated cheek biting. These are minor on their own, but they are worth mentioning to your dentist, since they can be the first sign that a wisdom tooth is not sitting well.
No Pain Does Not Mean No Problem
Please remember that pain is a late signal, so a tooth may be in real trouble long before it ever aches. Decay on that hidden surface starts in the hard outer layers of the tooth, well away from the nerve, and those layers cannot feel it. Discomfort usually only occurs once the decay has progressed deeper, closer to the nerve, or once the area becomes infected, and by that stage, the neighbouring tooth may already be badly affected. That was the pattern in our case. The wisdom tooth never hurt, yet the molar beside it had been decaying for some time before the scan showed how far it had gone.
Do Wisdom Teeth Need Checking If They Don’t Hurt?
Yes. Wisdom teeth are worth checking even when nothing hurts, because sometimes the damage they do to the tooth in front, decay on a hidden surface that cannot be cleaned, may be silent in its early stages and can be spotted on an examination long before it would ever be felt.
A check starts with a look at the back of the mouth: how far the wisdom tooth has come through, whether the gum is healthy, and whether food is packing against the tooth in front. Because decay tends to start on the surface between the two teeth where the eye cannot reach, we use X-rays to see it. A bitewing shows decay forming between the back teeth, and a panoramic X-ray, or OPG, shows the angle and position of the wisdom tooth and how it sits against its neighbour. A 3D scan, or CBCT, is only used when there is a clear reason, such as a wisdom tooth close to the nerve or a neighbour that already looks affected, since it involves more X-ray exposure. In our case, that scan was what showed how deep the decay had reached, not any pain.
What If Your Neighbouring Tooth Is Already Affected, What Is Our Next Step
What we do next depends on how far the decay in the neighbouring tooth has gone. Caught early, the tooth in front can often be saved with a filling. If the decay has reached deeper, closer to the nerve, it may need a root canal to keep it, and if it has gone too far to restore reliably, that tooth may have to come out as well. Sometimes, the wisdom tooth that caused the problem needs to be removed too, so it cannot start again, and when a lower wisdom tooth sits close to the nerve. A back molar that has decayed badly cannot always be saved, and sometimes the most sensible plan is to remove both teeth rather than try to rescue one that is unlikely to last. Which path is right is a decision we make with you, based on what the examination and the scan actually show.
Takeaway
The thread through all of this is simple. A wisdom tooth does not have to hurt to be doing harm, and the tooth that pays the price is often the healthy one right in front of it. So do not wait to feel something. Have the back of your mouth checked, with the right X-ray, at your regular visits, and especially in your late teens and twenties when wisdom teeth come through. Equally, if your wisdom teeth are fully through, upright and easy to clean, there may be nothing to do at all beyond keeping an eye on them.
Disclaimer
This article is general information only and is not a substitute for personalised dental advice. Every mouth is different, and the right approach for you can only be decided after an examination by your dentist. If you have any concerns about a wisdom tooth or the tooth next to it, please book a check-up.
Concerned About Your Wisdom Teeth? Let Us Take a Look
If a wisdom tooth is playing on your mind, the easiest next step is to come in and let us take a look, X-ray included if needed, so you know exactly where things stand. Our eligible patients can spread the cost over time with humm, or use SuperCare to access their superannuation early to help pay for it.
Clinic Location: 11/1932–1974 Logan Rd, Upper Mt Gravatt, QLD 4122
Phone Number: 07 3343 4869
