Dental Crowns: Zirconia vs E.max vs Porcelain-Fused-to-Metal

When do I need a crown instead of a filling or veneer?

A filling is enough when a large, healthy part of the tooth remains. A veneer is a thin shell covering only the front surface, mostly used to improve the look of healthy front teeth. A crown is usually preferred in cases such as:

• Large decay or a fracture that leaves too little tooth wall to hold a filling.
• A back tooth after root canal treatment, as it becomes more prone to cracking.
• A cracked tooth that hurts when you bite.
• Teeth severely worn by grinding or acid.
• Covering an implant, or supporting a bridge that replaces a missing tooth.
• A tooth whose colour or shape is too altered for a veneer to correct.

How do zirconia, E.max and porcelain-fused-to-metal differ?

All three are well-established, safe options; they differ in strength, appearance and how much tooth must be reduced:

• Zirconia: a very strong ceramic that withstands chewing forces, so it suits molars, bridges and people who clench. Solid (monolithic) zirconia is slightly less translucent than E.max; newer, more translucent types look better but are relatively less strong.
• E.max (lithium disilicate): lets light through much like natural enamel, giving the most lifelike look for front teeth and premolars. It is bonded firmly to the tooth, which sometimes allows less reduction, but it usually does not suit long bridges or heavy grinders.
• Porcelain-fused-to-metal (PFM): a metal base covered with porcelain, with a long track record and good strength. Its drawbacks are a less natural look in light, a possible dark line at the gum edge if the gum recedes, and occasional chipping of the porcelain layer.

What are the steps, and how many visits will I need?

A crown usually takes two visits about one to two weeks apart, though this varies with the case and how the crown is made:

• Examination and X-rays, with root canal treatment or a core build-up first if needed.
• Shade selection. If you want whiter teeth, whiten before this step, because a crown does not change colour with whitening.
• Shaping the tooth under local anaesthetic to make room for the crown.
• Taking an impression or a digital scan, then fitting a temporary crown.
• At the second visit: trying in the final crown, cementing it and adjusting the bite.

How long does a crown last, and how do I care for it?

Crowns are commonly said to last around 10 to 15 years on average, and they may last longer or shorter depending on care, bite force, grinding and the material. What most often ends a crown's life is not breakage but decay at its edge under the gum, or gum inflammation around it.

So brush twice a day with fluoride toothpaste, clean between your teeth with floss or small interdental brushes, and have regular check-ups. If you clench at night, ask about a night guard, and avoid crunching ice, date stones or nut shells with your teeth.

Common myths that are not true

Many ideas about crowns circulate, and some lead to poor decisions:

• "A crowned tooth cannot decay": not true; the tooth under a crown can decay at the edge if cleaning is neglected.
• "Zirconia is always best": the best choice depends on the tooth's position, your bite and the look you want.
• "Every tooth that needs a crown needs a root canal": no; many crowns are placed on living teeth, and your dentist decides after examination and X-rays.
• "A black line at the gum is unavoidable": it is mainly linked to metal-based crowns and is less likely with all-ceramic crowns.