Impression techniques in implants

dental implant

1. Impression Techniques in Implants Mohammad Ibrahim AL- graisi BDS- Msc PROSTHODONTIC DEPARTMENT

2. Introduction: The main goal of an impression implant restoration is to accurately relate an analogue/abutment of the implant to the other structures in the dental arch. This review focuses on the components, impression materials and the various impression techniques that can be used in implant restorations with note on recent advances in implant impressions The success of implants depends on its osseointegration and the passive fit of the prosthesis. The discrepancies in the passive fit of the prosthesis may lead to complications such as screw loosening, screw facture, occlusal discrepancies, increased plaque accumulation, resulting in loss of osseointegration and implant fracture.

3. Impression Materials:

4. A primary concern when dealing with the impression restorations is accurate transfer of the relationship of the implant and /or any remaining dentition to the master cast If the transfer of the analog is not accurate it will affect the passive fit of the prosthesis, for this the impression material used should be resilient enough to spring out of the undercuts and stiff enough to allow for accurate seating of the components in to impression It should also prevent dislodging of the components during the pouring of the impression and avoid the fracture of the stone when the prepared abutments are small. Thus the impression material should be sufficiently flexible and rigid. The most commonly used impression materials in implant dentistry are vinyl polysiloxanes and polyether rubber base impression materials . Vinyl polysiloxane impression materials are often used as they have excellent dimensional stability, superior deformation recovery and accurate reproduction of details. The mechanical properties of the siloxane impression material are adequate to withstand various stresses upon removal and maintain dimensional stability.

5. The most important property of an impression material is its wettability which helps provide detail reproduction in wet oral surfaces and also reproduces the details accurately with gypsum slurry. A newer impression material Vinyl polyether silicon (VPES) which is a combination of vinylpolysiloxane (VPS) and polyether(PE) has been introduced which according to the manufacturer has intrinsic hydrophilicity and high dimensional stability.

6. Components

7. Implant Analogue or Replica are metal replicas that duplicate the implant head or abutment connected to the implant which are used in laboratory to construct working model.

8. Impression copings have been designed for making final impression after the soft tissue has matured. These copings have the same flare as the healing abutments and should fully support the soft tissue around the head of the implant. They are various types of copings available which are selected based on the impression techniques. In transfer type the coping is retained in the mouth when set impression is removed. In pick up type the coping gets incorporated in the impression and it is removed from the mouth with the set impression

9. Impression Techniques:

10. IMPLANT LEVEL IMPRESSION TECH Direct Impression techniques (Open tray, Pick Up): A custom or stock open tray with access to the impression coping screws is required, which exposes the coronal ends of the impression coping.(fig:2) Impression material is syringed around the impression coping and filled tray is then inserted into the mouth, ensuring that guidepin of the impression coping is visible and protrudes through the hole in the tray. Impression copings are unscrewed and they are removed from the mouth together with the set impression.(fig:3)The implant analogues are connected to the copings using the same screw.(fig:4). Some precautions to be taken are: radiographically confirmed seating of impression coping to the implant and use vinyl gloves when elastomeric impression material is used.This technique can be used for single tooth restorations, multi-unit restorations and implant over dentures for either cement retained or screw retained prosthesis. FIGURE 2 FIGURE 3 FIGURE 4

11. An advantage of OPEN TRAY technique is the dentist can confirm the laboratory preparation and contour of the provisional prosthesis to achieve the desired healing and soft tissue contour before final crown fabrication.26 The direct technique can be further subdivided into splinted and non-splinted techniques. The splinting procedure is recommended in case of multiple implants to decrease the amount of distortion and to improve impression accuracy and implant stability. Splinting of the transfer copings prevents rotational movement of impression copings in the impression material during analog fastening, which provides better results than not splinting. Reduces the effect of the implant angulation Reduces the deformation of the impression material. removes the concern for replacing the coping back into its respective space in the impression. Disadvantage of Open Tray The movement of impression copings inside the impression material during clinical and laboratory phases may cause inaccuracy in transferring the spatial position of implants from the oral cavity to the master cast. some rotational movement of the impression coping when securing the implant analog may occur. Blind attachment of the implant analog to the impression coping may result in a misfit of components.

12. Indirect technique(closed tray): An indirect technique is also known as closed tray impression technique.The copings are connected to the implant (fig:5)and after the removal of impressions they are retained on the implants. These copings are then removed from the implant, attached to the implant analogues and reinserted in the impression. (fig 6&7).Clinical situations which indicate the use of the closed tray technique, such as when the patient has limited interarch space, a tendency to gag, or if it is too difficult to access an implant in the posterior region of the mouth. FIGURE5 FIGURE 6 FIGURE 7

13. Advantages of Closed Tray Easier Suitable for short inter arch distance. Visual fastening of the analog to the coping is more accurate Disadvantages of Closed Tray Inaccuracies with recovery and subsequent deformation of impression material may be encountered with nonparallel implants. Not Suitable for deeply placed implants.

14. ABUTMENT LEVEL IMPRESSION TECHNIQUES Direct techniques By intra oral preparation of the abutment Indirect techniques Open tray techniques Closed tray techniques Press-fit techniques