Porcelain inlays are essentially custom shaped porcelain fillings, which look natural and are super strong. Porcelain onlays cover the biting surfaces of teeth to protect weak/damaged teeth, similarly they look amazing and are very strong.
Onlays/inlays can provide extra strength to the tooth and protect the remaining weakened parts of the tooth. This is the case when over half of the tooth structure has been lost from decay or fractured. Fillings are mainly used to restore teeth that have enough tooth structure remaining to act as a strong framework to surround the filling.
When a tooth is heavily broken down or decayed it's best to try and save as much as possible of what's left. Crowns often require healthy tooth to be removed whilst porcelain inlays / onlays are much more conservative - this is a huge benefit and recent advances in material science make it a highly predictable long-term solution.
Like any restoration in dentistry, maintenance is the most important factor to ensure your inlay/onlay lasts as long as possible. Studies show the survival rates for all porcelain inlay/onlay restorations can vary from 5-10 years depending on a number of factors. It is very important you avoid very crunchy foods, see your dentist and hygienist for regular appointments every year and brush well!
"I broke a really big silver filling over the weekend, Dr. Patel placed a new all porcelain onlay over the broken tooth to repair it and it looks fab!"