PROSTHETIC TIPS FOR THE RESTORATIVE DENTIST

Custom Trays:

A custom tray is recommended for implant impressions to accommodate the extended length of the transfer components. A custom tray will also ensure room for adequate amounts of impression material, assuring a distortion-free impression.

Implant Model:

If uncertain about the type of abutment to for the restoration, record an impression of the implant(s) using the transfer technique. The impression can be poured with a soft tissue model material and the laboratory can assist with the selection of appropriate abutment design of the restoration. This model can also be used for fabrication of the restoration.

Abutment Seating:

After removing the healing abutment or healing cap, irrigate and inspect the implant interface for any bone or tissue fragments. Any small debris can preclude the required flush interface necessary for a secure seat. An abutment must be securely seated into the implant prior to any impression procedure. The abutment should be firmly seated with the appropriate tool. A radiograph can be helpful to confirm proper seating.

Radiographs:

A periapical radiograph may be taken prior to recording the impression to ascertain a flush interface between the abutment and implant or transfer assembly and implant. If these components are not fully seated, the impression will be inaccurate.

Removal of Broken Screws:

If an abutment screw fractures in the abutment or the abutment fractures in the implant, the remaining portion of the abutment can usually be removed with a suction tip or an explorer to work the broken segment out.

Materials:

All transfer impressions should be recorded with a firm impression material such as polyvinylsiloxane or polyether. Impression material should be expressed around transfer components as well as in the tray. Follow manufacturers’ recommendations regarding use of tray adhesives. Final impressions of modified Fixed Abutments can be recorded with conventional crown and bridge impression materials.

Inspection:

After removing the impression from the mouth, check the area in the impression around transfer component for impression material. If a flash of material is present, the transfer component was not properly seated. A new impression must be taken.

Abutment Modification:

Necessary modification of fixed abutments should be done on an analog model rather than intraorally. The heat generated by contouring the abutment is potentially detrimental to the health of the implant/bone interface. Small abutment adjustments with water irrigation may be made intraorally.

Framework Try In:

A try-in of the metal framework is advised prior to completion of the final restoration. Consideration should be given to casting large frameworks in sections, relating the sections intraorally with a light-cured resin and soldering the sections in the laboratory.

Fixed Cementation:

Provisional cement may be used for cementing crown and/or bridge restorations to Fixed Abutments. The provisional cement will maintain the ease of retrievability in the restoration and preclude moisture and bacteria from gathering between the restoration and abutment.

Combining Fixed Components

In multiple implant supported restorations, a situation may occur where it would be desirable to use multiple Fixed Abutments (cement-retained prosthetics).

Covering Abutment Screws:

Seat the restoration and tighten the abutment screw with the torque wrench. Place a thin covering of removable material over the head of the abutment screw (e.g., gutta percha, temporary filling material). Fill the remaining channel with a restorative composite material.

PROSTHETIC TIPS FOR THE LABORATORY TECHNICIAN

Abutment Modification:

When modifying fixed abutments, carborundum discs and carbide burs are most effective. It is not recommended to modify fixed abutments intraorally. All major modifications should be done on an implant analog or diagnostic model with implant analogs in place.

Waxing:

The waxing of the restoration should be done directly to the prosthetic abutment that is to be utilized as the final abutment in the patient’s implant.

Alloy Selection:

All implant restorations should be fabricated from a high noble alloy. Non-noble alloy materials should be avoided in implant prosthetics.

Die Material:

When pouring crown and/or bridge models of modified fixed abutments, a reinforced die stone, epoxy or resin material is suggested in the area of the abutments for additional strength.

Gold Alloy Abutments:

These components are machined from a high noble, non-oxidizing gold alloy. For ceramo-metal restorations, be certain that the wax covers the parent alloy in all areas that will receive porcelain. When casting to these components for a ceramo-metal restoration, an alloy with a similar thermal coefficient of expansion must be used. The wax is burned out and subsequently replaced with ceramic alloy. Care must be taken to ensure adequate thickness of the cast alloy to prevent cracking of the porcelain.

Plastic Components:

When placing the abutment screw into a plastic component, lightly tighten the screw just to stabilize the component. Excessive tightening can potentially distort the plastic component during the waxing phase.

Polishing:

When polishing the prostheses place some sort of protection over the soft tissue portion of the implant neck area to protect the surface during polishing procedures.