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Onlay vs Crown

healthy crows1
Fig. 1

If a tooth has too much decay or is too broken to be fixed with just a filling, the traditional way to fix or repair the tooth is a crown. Interestingly, in order to “repair” the tooth, the technique requires the drilling of approximately 75% of the tooth (Fig. 1) away, into a little peg (Fig. 2). Often, the drilling goes below the gum line, leaving the gums very sore and traumatized. Finally, the tooth is covered with a porcelain or metal crown cap, usually cemented on, leaving foreign material below the gum (this causes a lot of permanent irritation (gum disease). (Fig. 2)

Healthy Cowns2
Fig. 2

Crowns have been used for over 100 years, and are considered very successful procedures to save a badly damaged tooth. Unfortunately, crowns have some disadvantages:

  • The removal of large amounts of healthy tooth structure: Does it sound reasonable in these modern times that if a tooth is badly damaged, the solution involves drilling away even more tooth than what is already missing? Natural, healthy tooth is the strongest material available; it should be preserved whenever possible!
  • Drilling below the gum line: When drilling tooth sub-gingival (or below the gum line), a dentist cannot help but disturb the gum health, causing bleeding, inflammation, and irritation that can lead to unnecessary and permanent gum damage.
  • Permanently placing the crown below the gum line: When the bottom edge of the crown has to be cemented below the gum line, it can cause permanent inflammation of the surrounding gum tissue. Additionally, it is more difficult for the dentist to see the margins of where crown ends and tooth begins, as the gum is hiding it. So, sometimes, the cementation is not seamless, and there are uneven ridges or leftover cement that can trap bacteria, again causing gum disease.
Healty3
Fig. 3
Healty4
Fig. 4

There are better alternatives now! With time comes scientific advances in materials and technique. Partial coverage onlays are also made of porcelain, and when performed using supra-gingival protocol, they can be a better substitute to a crown. They work very well when there is too much compromised tooth to just diagnose a filling. With bonded porcelain onlays, the dentist gets to utilize the modern advances of adhesion. With adhesion, you can take away as little tooth as needed, then use bonding material to adhere the porcelain to the tooth and reinforce weak areas. The margins of the onlay do not need to be hidden below the gum line, as the modern materials are beautiful and look natural. Also, the dentist knows with adhesion, the porcelain will stay and is very strong, so they need not feel that a crown is stronger or more durable (see Literature References). (Fig. 4: See a badly damaged tooth repaired with minimum tooth removal, which is more esthetic.)