Efficacy of the Encode Impression System vs. the Implant Level ImpressionErick Lachner, DDS. Elias Kontogiorgos, DDS, PhD. Ronald Woody, DDS. William Nagy, DDS. Graduate Prosthodontics Department & Center for Maxillofacial Prosthodontics

OBJECTIVETo quantitatively compare the analog placement accuracy of the Encode Impression System (EIS) and the conventional implant level impression, and to qualitatively assess the clinical relevance.

Magnitude (mm)

BACKGROUNDAn implant is often an extension of a clinical crown. Replicating its location and orientation in a model can be challenging. Obtaining an implant level model usually involves replacing a healing abutment with a pick-up or transfer coping and making an impression. Implant analogs are attached to the copings resulting in an implant level cast. Using the Encode Impression System (Biomet 3i) the clinician obtains an implant-level model simply by making an impression of an Encode Healing Abutment (EHA).The resulting cast is scanned and the EHAs provide a CAD software with information on the implant depth, connection type, orientation, and platform size. With this input Encode abutment sites on the model are converted into implant analog sites using a robot.

Impressions (n=5) were made using EHAs and conventional impression copings (BIOMET 3i) on the right and left sides of the arch. Impression techniques were switched to the opposite arch sides (n=5) and the process was repeated (Figure 2). Impressions (10) were poured using vacuum mixed type IV dental stone (Resin Rock, Whip Mix Corp).

EHAs were placed on the patient model and the (10) implant-level models (Figure 3). Analog center point (x,y,z) coordinate data was obtained using the laser scanner. Vector magnitudes (n=66) between the analogs on each side of the arch were calculated for the patient and test models. The average error for the (6) vector magnitudes (Figure 4) was determined by comparing the test and patient model data. Verification jigs were fabricated on the patient model by splinting all (3) implant sites on each side.

Chart 1:Mean Vector Magnitude Error per Group (mm)0.06 0.05 0.04 0.03 0.02 0.01 0.00

Conventional

Encode

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18 19 20

Chart 2: Mean Magnitude Error per Vector Site (mm)0.06 0.05 0.04 0.03 0.02

Figure 2: Samples with EHAs on right and EHAs left sides Each model contained (3) implant analogs (BIOMET 3i) and (3) stone EHA replicates at this point (Figure 2). The Encode sites within each model were laser scanned (3Shape), and this data was used to derive the associated fixture-level position and orientation data. Implant analogs were placed at the Encode sites in the models using Robocast technology (BIOMET 3i).Models postrobotic analog placement

30 29

Conventional Encode

Figure 4: Patient Model Vectors

0.01 0 18-19 18-20 19-20 30-29 31-29 31-30

RESULTSNeither of the two processes resulted in implant master casts without inaccuracies when compared to the simulated patient model. The average vector magnitude error was 20 for the Conventional group and 38 for the Encode group. The range of magnitude variation was 14 to 27 in the Conventional group, and 23 to 55 in the Encode group. When comparing the absolute magnitude variation between the Encode and Conventional groups a statistically significant difference (p=0.009) was found (Chart 1). The magnitude variation data was not significantly different (p>0.05) when only specific vectors were compared between the Encode and Conventional groups (Chart 2). Verification jig tests for both techniques were capable of rendering clinically acceptable fit. However, the Conventional group had a higher passivity rating.

MATERIALS AND METHODSA patient model was fabricated with (3) implants of (3) different platforms (BIOMET 3i) with angulations between 1030 degrees on each side. Custom trays were used to make (10) impressions using a VPS material (Aquasil Ultra, Dentsply) following a non-splinted, open tray, implant level impression technique. (Figure 1)

CONCLUSIONSThe quantitative assessment indicates that the conventional process yields more accurate results than the EIS method. The qualitative assessment, however, suggests that clinically acceptable fixture-level models can also be fabricated using the EIS. The Encode Impression System can simplify the process of creating accurate implant level models for single or multiple implant supported crowns and short-span 2implant supported fixed dental prosthesis.

Figure 3: Process Flow to final scan

ACKNOWLEDGEMENTSStudy partially supported by:For Information contact: Dr. Erick Lachner Elachner@bcd.tamhsc.edu

EHA

Figure 1: Patient model and impression protocol.