Opposing Tooth Wear.
A restoration is placed to protect a tooth. It should not be quietly destroying the one it bites against, and whether it does is largely within your control.
Hardness is not the whole story
Restorative materials vary in hardness, and ceramics are generally harder than enamel while gold alloys are broadly comparable to it. That ordering suggests a simple hierarchy of antagonist wear, and the reality is more interesting.
Surface roughness turns out to be at least as important as intrinsic hardness, and frequently more so. A rough surface presents asperities that abrade the opposing tooth mechanically, and a hard rough surface does so very effectively.
The practical consequence is that a well-polished hard ceramic can be kinder to opposing enamel than a poorly finished softer one. Finish is the variable with the largest effect and the one most under clinical control.
A working hierarchy
Cast gold sits closest to enamel and is the reference against which the others are judged. Well-polished monolithic zirconia performs considerably better than its hardness alone would suggest, and better than glazed zirconia over time. Feldspathic and leucite-reinforced porcelains, particularly when the surface has been ground, are among the more abrasive options.
Layered restorations are worth noting separately, because the surface in occlusal contact is the veneering porcelain rather than the core. A layered zirconia restoration presents porcelain to the antagonist, not zirconia, which changes both the wear behaviour and the fracture behaviour.
None of these are absolute rankings — they shift with formulation, with finish and with the individual patient's function.
Who is at risk
Patients with evident parafunction, because the number and force of contacts is far higher. Patients with existing generalized wear, because whatever caused it has not necessarily stopped. Patients where a single hard restoration opposes intact natural enamel, because the load is concentrated rather than distributed.
That last situation is the most common and the least considered: a single posterior crown opposing an unrestored tooth, where the restoration is the only hard surface in an otherwise natural arch.
Patients with reduced salivary flow are also more exposed, because saliva provides lubrication and buffering that reduce both abrasive and erosive wear.
Designing against it
Material selection is the first lever. Where a patient has heavy function and intact opposing enamel that you want to preserve, cast gold remains the kindest option and well-polished monolithic zirconia is a reasonable alternative.
Occlusal design is the second. Contacts that are broad and axially directed distribute load; point contacts on inclines concentrate it. Keeping the restoration free of excursive guidance where natural teeth can provide it removes the sliding contacts that cause the most wear.
Surface finish is the third and the most important. Whatever material is chosen, it should reach the patient polished, and it should be repolished properly if it is adjusted.
Monitoring
Wear is slow and cumulative, which means it is invisible between appointments and obvious across years. That makes a baseline record valuable: photographs at delivery, or study casts where the case warrants it.
At review, look specifically at the tooth opposing any hard restoration, not only at the restoration itself. Flattened cusps, exposed dentine and loss of occlusal anatomy on the antagonist are the signs.
Where wear is progressing, the questions are whether the restoration's finish has degraded, whether the occlusal scheme is loading it unfavourably, and whether the underlying parafunction is being managed.
When wear has already occurred
The options are to repolish the restoration if roughness is the cause, to adjust the occlusal scheme if unfavourable loading is, to protect the dentition with a splint if parafunction is, or to replace the restoration in a more compatible material if the material choice was wrong for the situation.
Frequently more than one applies. What is not useful is monitoring wear indefinitely without addressing the cause, because the opposing tooth does not recover.
If a restoration is being replaced for this reason, tell the laboratory why. It changes both the material recommendation and the finish.
Erosion changes the picture
Mechanical wear is only one mechanism. Acid erosion — dietary, gastric or occupational — softens enamel, and softened enamel abrades far more readily against any opposing surface.
A patient with reflux, frequent acidic intake or a history of eating disorders will show wear rates that no material choice fully compensates for, and restoring the wear without addressing the cause produces the same problem again around the restorations.
Where erosion is suspected, the medical and dietary history matters more than the restorative material selection, and the restorative plan should follow rather than precede it.
Restoring worn dentitions
A generalized worn dentition is one of the situations where reorganizing the occlusion and altering the vertical dimension is genuinely indicated, because the space needed for restorations no longer exists at the patient's current closure.
That is a substantial undertaking, and it needs a provisional phase, a defined jaw relationship, and agreement about the occlusal scheme before any definitive work is made. It also needs a decision about material that accounts for whatever caused the wear in the first place.
Restoring individual worn teeth as they present, without addressing the pattern, generally produces restorations that fracture or wear at the same rate the natural teeth did.
A note on splints
Where parafunction is the driver, an occlusal splint protects both the restorations and the natural dentition, and it is frequently the most cost-effective intervention available.
It only works if it is worn, which makes fit and comfort clinical priorities rather than laboratory niceties. A splint that is uncomfortable is a splint in a drawer.
In short
- Surface roughness drives antagonist wear at least as much as hardness
- Polished monolithic zirconia performs far better than its hardness suggests
- A single hard restoration opposing intact enamel is the common at-risk case
- Keep excursive guidance off hard ceramic where natural teeth can provide it
- Record a baseline and examine the antagonist at review, not just the restoration
More on clinical
Discuss a case
Where a case sits between options, a short conversation before preparation is usually quicker than resolving it afterwards.