IMPRESSION TAKING

Once the implant or implants are placed, the restorative phase is initiated after approval from the surgical office. Impressions may be carried out digitally with a intraoral scanner or through traditional impression taking methods.

Traditional impressions of implants may be accomplished in one of three different ways. Abutment level impressions are taken over already installed final abutments which have been preinstalled by the surgeon or are installed by the dentist. Fixture level or implant level impressions are sub divided in to two groups. Indirect implant level impressions are accomplished with unmodified impression trays while direct impressions require modification to the impression tray. The modification of the tray can be achieved with a slow speed drill by cutting a hole in to the tray in the area of the implant to be impressed.

Polyvinylsiloxane (PVS) impression material is the preferred impression material for traditional impressions. A medium body impression material in combination with a light body wash preloaded in to syringes or auto mix devices in addition to custom or stock trays are part of the operatory set up. The medium body putty and wash impression material should be from the same manufacturer and of the same impression material brand name. Do not combine different impression materials from different manufacturers or brand names to avoid possible incomplete curing of the impression material once combined in the impression tray.

Special tooling and impression components called impression copings or transfer copings are required to accomplish impressions of dental implants. Abutment level impressions are usually carried out with one or two component, snap on plastic copings while fixture level (direct or indirect) impressions are accomplished with screw on impression copings. Screw on impression copings are made up of two parts; a fixation screw and the impression coping body. Both parts need to be sent along with the impression, opposing and bite record to the laboratory. Implants are produced in different diameters and impression copings are machined to fit specific implant diameters. Most manufacturers color code impression copings for diameter identification purposes. Fixation screws packaged with impression copings are specific to the impression coping body they were packaged with and should not be interchanged with other impression copings.

Screw drivers are specific to each implant brand and may work in conjunction with a driver handle or torque driver. In most instances the driver is utilized to unfasten the healing abutment also called the transmucosal healing abutment from the implant and fasten the direct or indirect impression coping on to the implant. The screw drivers are rather small and to prevent swallowing or aspirating the screw driver by the patient a piece of dental floss may be tied to the screw driver.

It is advisable to prepare multiple small containers in advance with clearly written implant position (tooth #) numbers on the outside of the containers in case of multiple implants to be restored for a single patient. Fill each cup with a small amount of chlorhexidine (Peridex™) for antibacterial purposes. Once the healing abutment is removed from the patient it is placed in the appropriate numbered cup and the implant diameter specific impression coping and fixation screw are handed to the dentist along with the screw driver.

After all impression copings are installed, the seating of the copings needs to be verified with x-rays. Taking the x-ray requires the x-ray beam to be angled perpendicular to the long axis of the implant. This will ensure a clear view of the mating surface of the impression coping and the implant. Taking the x-ray at an angle to the long axis of the implant will obscure the mating surface between the implant and impression coping, making verification of proper seating of the components unpredictable. Snap on, plastic abutment level impression copings do not need to be x-rayed since they are radiolucent.

Once proper seating of the fixture level impression copings is verified the impression may be taken. Load the tray with impression material while the dentist extrudes impression material around the impression copings and place the impression tray in the patients mouth over the copings. In case of direct impressions the dentist will need to wipe some impression material from the fixation screw protruding through the impression tray to allow easy access to the screw head.

Direct impressions require the dentist to unfasten the fixation screw after the impression material has set and remove the screws completely from the impression before removing the impression tray from the patient. The direct impression coping body should be firmly embedded in the impression material and the screws need to be reattached to the corresponding impression coping in the impression after removal of the impression tray from the patient.

Indirect impressions are removed from the patient once the impression material has set without unfastening the indirect impression copings first. Once the indirect impression tray is removed from the patient, the impression copings are unfastened from the implants in the patients mouth. Place each indirect impression coping and the corresponding fixation screw in separately position number labeled sterilization pouches.

Abutment level impression copings are firmly embedded in the impression material once the impression tray is removed from the patient and do not require any further handling.

After all impressions and the bite record have been taken and the impression copings have been removed from the patient the healing abutments are reinstalled on to their corresponding implants and hand tightened with the screw driver.

Indicate on the lab slip the brand name of the implant and which impression coping (platform diameter in millimeter or color of the coping) belongs in which tooth position. Also denote the type of desired restoration and tooth shade. Include a copy of the x-ray taken (if any) with the impression coping installed on the implant and the surgical report from the surgeon who placed the implant to complete the documentation for the laboratory. Spray each impression with a cold sterilizing agent and place each impression in a separate, clear Ziplock® bag. Ensure all impression copings and fixation screws are shipped with the impressions to prevent any delay in the production of the restoration at the laboratory.

Sterilize (Autoclave) any tools utilized during the impression taking procedure in a conventional fashion. Torque wrenches may need to be disassembled prior to sterilization depending on the brand of torque wrench utilized. Each torque wrench is supplied with detailed disassembly, sterilization procedure and maintenance instructions (IFU).