Crowns are fixed prosthetic devices that replaces crown of your tooth, placed on the implants to improve a tooth’s appearance, shape, alignment and occlusion. They may be the ideal solution for your disfigured, stained, crooked, root cana treated , fractured or damaged teeth.
There has been so many advances in the field of dentistry, including crown fabrication. They may be of both temporary and permanent crowns.
There are different types of crown based on following provision :
- BASED ON RETENTION
- BASED ON AESTHETICS
Based On Retention
CEMENT-RETAINED IMPLANT CROWN
In this, Cement is used to fix the prosthesis to the post on implant.
PROS
- A fairly simple technique that can be repeated with ease.
- The crowns used for this purpose can be made from a variety of materials like ceramics, porcelain, E. Max, PFM gold, silver, and composites.
- Greater resistance to porcelain fracture
- Fabrication of cement retained crown is easier
- Comparatively easy access in patient with limited mouth opening
CONS
- If there is excess cement below the gums it can cause inflammation / soft tissue damage.
- Cemented crowns have attributed to cause bone loss in some patients.
- Their removal is challenging
- Excess cement placement can later lead to implant failure
Screw-retained Implant Crowns
This crown is fabricated so that there is a hole on the surface of the lingual and occlusal portion which enables restoration to be connected directly to the implant through a fixation screw.
PROS
- They do not require cement.
- Removable easily than cement retained crowns.
- Easy retrievability
CONS
- Screws may loosen up and rquire tightening or even need replacement.
- Esthetic and strength may get compromised.
- More expensive
Based On Esthetics
There are some really popular crowns available based on the material and esthetics like porcelain fused to metal (PFM), e.max, layered zirconia, full-contour zirconia, porcelain-filled composites, and full gold.
PFM crowns
porcelain is fused with metal to encase the tooth. PFM gives the crown a tough underneath structure with a tooth-colored anterior surface. Indicated mostly for implants. The latest generation of metal-ceramic crowns utilizes the pressed-over-metal (POM), or pressed-to-metal (PTM), fabrication method.
PROS
- More strength and durability.
- Esthetically it gives a natural look to tooth.
CONS
- Wearing of adjacent tooth
- PFM crown do tends to chip off / fracture- crown replacement is the only option.
- Sometimes the metal beneath the porcelain can be seen as a dark rim/ line at the level of gums.
- These may appear as dull and opaque
E.Max crowns
The latest and most expensive crown today. They are made up of lithium desilicated ceramic, a material known for its translucent color and strength. It has an extensive indication range like veneers, inlay, onlays, partial crowns, bridges, hybrid crowns.
PROS
- Remarkable light optical properties
- Less prone to fracture / crack / chipping.
- More tough and durable
- They may be adhesive, self adhesive or cemented depending on the indications.
- All ceramic prosthesis with no use of metal.
- Wide range of indications.
CONS
- The only cons of e.max crowns is that they are too expensive
- May not suit darker teeth
Layered Zirconia Crowns
These crowns are designed through CAD/CAM technique and consist of Zirconia underneath and are veneered with porcelain. They can be used for fabrication of copings, bridges, abutments, and its primary components.
PROS
- Excellent aesthetics achieved
- Metals are not included in fabrication
- Can be designed for any length or size of abutment
- Suitable for both anterior/ posterior crowns and cridges
- Great biocompatibility
CONS
- Require more occlusal clearance than full contoured zirconia
Full contour Zirconia crowns
PROS
- Higher resistance
- Indicated for patient having bruxism or grinding habits
- Recommended when patient lacks the preparation space
- Less abrasive
CONS
- Bond strength is weak
- Esthetic expectation less compared to e.max or layered zirconia
All Ceramic
All ceramic are made up of porcelain-based material known for their ability to blend with your natural tooth color, especially used for restoring front teeth.
PROS
- Aesthetically appealing
- Thickness can be increased
- Highly biocompatible
CONS
- Not much durable
- Decreased resistance to fracture and brittleness.
- Preparation may be complicated
Gold Crowns
This crown is a mixture of gold, copper and other metals and is one of the oldest material for crown fabrication.
PROS
- They rarely chip or break
- Excellent durability, may last upto years.
- Least wear, relieve stress on heavy bite
- Less tooth cutting required
- Biocompatible
CONS
- Least natural looking material
- May be costly
- Metal allergies
Types Of Dental Alloys
- High noble (precious).
It includes 60% precious metal (gold, platinum, and/or palladium), of which over 40% is gold. Considered as “gold standard” of dental alloys - Noble (semiprecious).
Alloys that contains over 25% precious metal (gold, platinum, and/or palladium). - Non-noble (base).
These alloys contain less than 25% precious metal. A large portion of which may be nickel, chromium or beryllium.
Whenever placing the crown, remember cements should be used cautiously, if the margin is more than 1 mm subgingivaly.
No “one” particular material can be documented as being the best for a particular patient. There has to be significant room for personal preferences amongst patients and clinician.
