What are dental implants?
Dental implants are the most successful way nowadays to replace a missing tooth or group of teeth, with success rates reaching up to 97% over the course of 10 years. Dental implants have been used in the industry for almost 30 years, but with the recent advancements in technology and upgrades to the material and technique, they have become the gold standard when it comes to replacing lost teeth. Other methods to replace missing teeth include removable dentures and dental bridges.
What are dental crowns?
A dental crown (or cap) is an artificial cover that is placed on the tooth structure to protect it from harm. Patients who suffer from cracks, large breakages and restorations, as well as those who received root canal treatment to their teeth can all benefit from dental crowns’ protection.
Dental crowns can also be placed on artificial replacements such as dental implants. The procedure for getting a crown on a tooth and getting a crown for an implant are quite different as will be explained here.
What are implants made of?
Most implants used nowadays are made from Titanium, which is a light, strong and inert metal that improves bone healing and induces new bone formation. Recently, Zirconium implants have been introduced in the industry, but the area is still under a lot of research.
Implants are composed of 2 pieces (in some cases these 2 pieces are fused together, known as one piece implants):
- Fixture: This is a screw-like structure that is long and cylindrical, placed inside the bone after cutting into it in the same size and length as the fixture. This is the base of the implant and responsible for holding the entire restoration in place.
- Abutment: Which is the part attached to the fixture, but sticks out of the gums and can be seen inside the mouth. This structure is the foundation on which implant crowns are formulated.
How are implants placed inside the mouth?
The procedure for getting dental implants is divided into two phases:
- Surgical phase: Where the screw like fixture is placed inside the bone. The surgery is simple, done under local anesthesia and takes less than an hour. After this stage, the bone is left to heal for about 3 to 6 months according to the strength of the bone.
- Prosthetic phase: In this phase, the abutment is attached to the fixture and is used as a foundation to formulate the implant crown.
More about the prosthetic phase:
After the bone healing is done, the surgeon would call you back to the clinic for a few xrays to make sure that the implant is in its proper place, and no bone loss or infection has set in.
The area is numbed with local anesthesia, and a tiny opening is made in the gums to expose the fixture. Then a structure known as healing abutment is screwed on to the fixture, which aids in the healing of the gums and is very important in shaping the gums to receive the crown later on. This structure is left for about 2 weeks for complete healing.
2 weeks later, this structure is removed and the final abutment is placed on top of the fixture. Molds (or impressions) are taken and sent to the lab, which then formulates the crown and returns it to the dentist for delivery to the patient.
What are implant crowns made of?
Implant crowns can be made from the same materials as regular crowns. The choices are:
- Metal and porcelain crowns: Which are the most frequently used type as they possess sufficient strength to withstand the biting forces on the implants.
- Zirconium Crowns: Also of sufficient strength, but have a white color as opposed to the metallic color of regular crowns, so preferred in esthetic zones.
- All Porcelain Crowns: Which are far superior esthetically, but lack sufficient strength compared to metal and zirconium, so their use with implants is somewhat restricted to the front areas where looks are more important than strength.
How are implant crowns different from regular crowns?
While the material may be the same, the technique is quite different. There are two main techniques when fabricating implant crowns:
- Direct technique: This technique is very similar to the regular crowns technique, where the abutment is prepared and shaved inside the patients mouth, and the impression is take and sent to the lab which then returns the crown to be cemented on top of the prepared abutment.
- Indirect technique: Where a copy of the abutment (Known as impression coping) is used to transfer the exact location of the abutment to the impression. After the cast is poured from stone, this coping is replaced by the actual abutment, and all the preparation is done in the laboratory.
There are also 2 types of crowns to be made:
- Cement retained: Which is the same likeness and shape as regular crowns, and are cemented on top of the abutment, meaning the abutment and the crown are 2 separate units.
- Screw retained: Where the abutment and the crown are formulated as one unit, that is screwed on top of the prepared fixture.
Which technique is best?
Each has their merits and drawbacks. The direct technique is much easier and less time consuming, and gives more control to the dentist than the laboratory, but the heat generated from the preparation and the pressure and vibration could damage the oral structures and the implants. In addition, we are limited to make the cement retained type, which is irretrievable if a problem arises, and often the screw between the fixture and the abutment is loosened leading to loss of the entire structure.
The indirect technique is more tricky but more accurate, and no damage is done to the mouth or the implant, but it takes much more time, a few more visits and is often more expensive than the direct technique. With this technique, either cement retained or screw retained crowns can be made. Screw retained crowns have the advantage of being retrievable, which means they can be easily dismantled from the fixture for repairs and adjustments, unlike cement retaine crowns.