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Dental implants. Prosthetic phase

author icon By Dr. George Ghidrai

The prosthetic phase begins once the implant is well integrated or has a reasonable assurance that it will integrate. Even in the event of early loading (less than 3 months), many practitioners will place temporary teeth until osseointegration is confirmed.

The prosthetic phase of restoring an implant requires an equal amount of technical expertise as the surgical because of the biomechanical considerations, especially when multiple teeth are to be restored.

The dentist will work to restore a functional bite (or occlusion), the aesthetics of the smile, and the structural integrity of the teeth to evenly distribute the forces of the implants.

Several steps are involved :


1. Removing the temporary restorations

The temporary restorations are removed from the mouth. There are situations when they can be reused during the execution of the definitive prosthesis.


2. Testing the degree of osseointegration

The first criteria to be considered are : the absence of pain, clinical mobility, infection and gingival bleeding.

The Periotest is a specific device that measures the degree of implant mobility inside the bone. It has the advantage of measuring the levels of subclinical mobility using an ultrasonically vibrating probe.

The Periotest is successful in assessing the stability status of an implant, but it can detect the quantity of bony osseointegration only in terminal cases (that means 3 to 6 months after the implant placement).

Therefore, it is advisable to combine this test with a dental radiography ; radiography proved to be a more sensitive method of determining the degree of bone formation (or loss) around a dental implant.

periotest

Periotest

periapical radiography dental implant

periapical radiography:
a well integrated dental implant

In conclusion, periapical radiographs in addition to the Periotest device were found to offer the most reliable assessment of an implant osseointegration status.


3. Removing the healing devices

After the placement of implants, a healing device was attached to each implant.

  • If a healing abutment was used, simply unscrewing it with a small key makes the removal.
  • If a cover screw was positioned, a second procedure is needed to uncover the implant. The incision is very simple and painless.

4. Attaching the implant abutments

Implant abutments are artificial devices that are connected to the dental implants after the healing process and are then used to attach the prosthetics to the implant fixtures.

Abutments come in a wide range of sizes and shapes, from which the ones that best fit the clinical case are selected. Generally, the selection is done when the treatment plan is devised, before the surgical placement (but this is not a general rule).

implant abutment

how is the abutment attached

implant abutments various types

implant abutments of various types


After the selection, the abutments are attached to the implant fixtures with a lag-screw. There are some variations on this, such as when the abutment and implant body are one piece or when a custom made abutment is used.

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.

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 (image bellow).

implants abutments angulation implants abutments angulation implants abutments angulation


5. The dental impression

Impression of the dental arches

The impression is made after the abutments are attached to the implants. Regardless of the size of the restoration, a complete impression (that captures all teeth and surrounding structures) of both dental arches is taken.

complete impression for an implant supported denture

complete impression for
an implant supported denture

It is advisable to use the custom tray technique or, if the prosthesis is not very extended, the two step technique. When removable dentures are designed, a functional impression is needed.

In some variations, after the impression, the abutment is unscrewed from the implant and sent to the dental lab along with the impressions.

Bite registration

The bite registration captures the relationship between the upper and the lower teeth. The long-term success of implants is determined, in part, by the forces they have to support. Therefore, restoring a proper occlusion (or bite) is one of the most important goals.

It is essential not to overload the implants with additional pressures and to evenly distribute the chewing forces of the implants. Otherwise, there is a high risk of failure.

Many times the usual techniques do not provide enough data for the dental technician. In complex situations, it is advisable to use advanced jaw tracking devices that provide additional details.

jaw tracking device

jaw tracking device

The jaw tracking devices provide details about the precise position of the maxilla and mandible against different anatomical structures of the head. This information is extremely useful when manufacturing large restorations that need to be extremely accurate.


6. Dental laboratory stages

All the impressions, along with the bite registration and other important details are sent to the dental laboratory. The dental technician will fabricate the designed prosthesis according to the specifications received from the dental office.

Laboratory stages were detailed in a separate chapter. The steps are largely the same :

  • first, the dental cast is obtained from the impression
  • the metal framework (or zirconia) is constructed and sent to the dental office for fitting
  • the next operation is the ceramics build up and the attachment of artificial teeth (if a removable denture was designed)
  • when all porcelain or zirconia restorations are designed, these are constructed with the CAD/CAM technology.

7. Fitting

Before the restoration is definitively attached to the dental implants, one or more fitting appointments may be needed. During these appointments, the practitioner checks how well the prosthesis fits and makes the necessary adjustments if the fitting is not perfect.

The dentist will first check the fitting of the framework, then, after porcelain build up, the shape, size and general appearance of the prosthesis are tested.

framework fitting for an implant supported denture phase 1
framework fitting for an implant supported denture phase 2

framework fitting for an implant supported denture

The framework fitting and the fitting of the definitive restoration were detailed in separate chapters. Many of the steps described there are relevant for implant supported prostheses as well.

Of a particular importance is the bite adjustment. This is a vital element, as a dysfunctional environment created by an inaccurately adjusted implant supported restoration can lead to the implants failure.


8. Attaching the prosthesis

Depending on the type of prosthesis, this particular step can differ

a. Fixed prosthesis

A fixed prosthesis is when a person cannot remove the denture or teeth from their mouth. Where the prosthetic is fixed, the crown, bridge or denture is fixed to the abutment with either lag-screws or cement.

  • Prosthesis is attached with lag-screws

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

    artificial abutment with a threaded hole

    artificial abutment with a threaded hole

    implant crown secured with a lag-screw

    the crown is secured with a lag-screw

    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.

  • Prosthesis is secured with dental cement

    In this case, the restoration is secured with dental cement, just like crowns and bridges are attached to natural teeth.


b. Removable dentures

Removable dentures are held in place by special adapters (or retainers). Generally, a male-adapter is attached to the implant and a female-adapter is housed in the denture.

special retainer abutments : male-adapters attached to the implants

the male-adapters
are attached to the implants

special retainer abutments : female-adapters are housed in the denture

the female-adapters
are housed in the denture

The retainers allow movement of the denture (that should be daily removed, to clean the denture and gum area), but enough retention to improve the quality of life for denture wearers, compared to conventional dentures.


Immediate care :

  • protect the part with the restoration in the early days
  • thorough oral hygiene
  • report any discomfort
  • first periodic checkup at no more than 6 months

Last review and update: May 2018



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