Dental implant abutment

By Dr. George Ghidrai

Implant abutments are artificial devices that are connected to the dental implants after the healing process is over. The abutments are used to attach a crown, bridge, or removable denture to the implant fixtures.

There are two classes of abutments : prefabricated and custom made.

a. Prefabricated abutments

Prefabricated or stock abutments are manufactured in a range of sizes and shapes and are usually delivered by manufacturing companies along with the implants. From the various range of abutments, the ones that best fit the clinical case are selected.

Material

Prefabricated abutments can be made from a variety of materials, such as titanium, surgical stainless steel, gold and, more recently, zirconium.

• Titanium abutments

  Titanium abutments are widely used due to the excellent properties of the titanium alloys. They have a very good strength and biocompatibility and can be used for any type of prosthetic restoration.

  

  titanium abutments

  Most clinicians feel more comfortable using a metal prosthetic abutment in the posterior molar areas, due to the increased masticatory forces present in these areas.

• Zirconium abutments

  Zirconium abutments are more modern abutments, which are used to better complement the aesthetics of a dental implant restoration.

  When all ceramics or zirconium restorations are planned, zirconium implant abutments provide a highly desirable option. When a zirconium abutment is used, the problem of matching the shade of adjacent teeth while hiding the dark color of the metal abutment is avoided.

  Moreover, in 2011, a one-piece zirconia implant (fixture and abutment) was introduced into the market.

• Other materials

  Besides titanium and zirconium, artificial abutments can be made of other materials: gold alloy, stainless steel etc. Although indications are narrower, there are situations in which these may be successfully utilized.

Features

When the practitioner selects the abutments, several factors are involved :

• The type of prosthesis that is executed : crown, fixed bridge or removable denture

• How the restoration is attached to the abutments : with dental cement, with lag-screws or with special retainers

• The position of the implant inside the mouth cavity : generally, larger artificial abutments are positioned in the back of the mouth due to the increased chewing forces

1. The prosthesis is secured to the abutments with dental cement

In this case, the surface of the artificial abutment is smooth. The restoration is secured to the abutments with dental cement just like crowns and bridges are fixed on natural teeth.

The main advantage is they offer a higher aesthetic performance.

2. The prosthesis is fixed with a lag-screw

These types of restorations require artificial abutments with a threaded hole in the middle.

The restoration is secured with screws that traverse the dental crowns and attach to the threaded holes. After the screws are positioned, the holes that penetrate the crowns are sealed with a composite material.

The advantage is they are easier to maintain and change when the prosthetic fractures.

3. Removable dentures secured with special retainers

Special retainer type abutments are used to retain dentures using a male-adapter attached to the implant and a female-adapter in the denture.

These types of stock abutments allow movement of the denture, but enough retention to improve the quality of life for denture wearers, compared to conventional dentures.

Regardless of the type of adapter, the female portion of the adapter that is housed in the denture will require periodic replacement.

Angulation

An abutment is not necessarily parallel to the long axis of the implant. Angulated abutments are utilized when the implant is at a different inclination in relation to the proposed prosthesis. The main purpose in this case is to make all artificial abutments parallel to each other.

b. Custom made abutments

Custom made abutments are fabricated at the dental laboratory after an impression of the top of the implant is made with the adjacent teeth and gingiva. The size, shape and material depend on the clinical application.

Normally, any type of abutment can be manufactured at the dental lab : with a smooth surface, with threaded holes and all kinds of special anchoring systems for removable dentures.

Another variation is when the crown and abutment are one piece and the lag-screw traverses both to secure the one-piece structure to the internal thread on the implant.

Regardless of the type of abutment, after the abutment is attached to the implant, an impression is made and the designed restoration is constructed at the dental laboratory (see prosthetic phase).

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