Jochen Könneker and Robert Kreyer, CDT, explore how to simplify the seating index for more predictable delivery of the final abutment



Transferring abutments for cementable restorations from the master model to the patient can be challenging due to limited intraoral access, an overwhelming number of possible seating positions (Zimmer®, Angled Abutment, 20°, for 24 positions), or lack of any repeatable seating position (Dentsply Ankylos® /C, Bicon®).

In addition, each abutment needs to be sterilized before delivery to the patient. The abutment has to be removed from the model for the sterilization process and should not be placed back onto the master model to avoid recontaminating the abutment. Removing the abutment from the master model for a lengthy time period makes it difficult to remember the proper orientation of the abutment in relation to surrounding anatomical landmarks.

A seating index can make the delivery of the final abutment in the correct orientation intraorally predictable and effortless. Abutment seating indexes may be fabricated with light-cure materials such as Visio™-Form (3M™ ESPE™), or cold-cure acrylic, such as Pattern Resin™ LS (GC America Inc.), for example.


 
Single-abutment seating indexes for abutments in a Kennedy Class III situation follow the same design from patient to patient, whereas the design of seating indexes can vary in cases with multiple abutments in a row. If the implants’ trajectories differ from each other significantly, the path of insertion dictated by the abutment indexing feature (hexagon, octagon, tri lobe, and others) will force a different seating index design compared to a seating index with parallel implants. A multi-unit seating index for parallel implants would simply require connecting the abutments with acrylic or light-cure material.

Multi-unit seating indexes for nonparallel implants may be manufactured in one of two design options. One option would be to fabricate a seating index for each abutment separately. A more efficient procedure would be to connect the abutments and to create “wings” onto the occlusal surfaces of adjacent teeth. This approach will require the delivery of the abutments one at a time, utilizing the same seating index twice.

The following will describe the manufacturing process for a multiple-abutment seating index, Kennedy Class II situation, and parallel implants with Visio™-Form (Figure 1). Block out any undercuts of the proximal surfaces of adjacent teeth and attach a number 8 gauge wax sprue to the abutment, following the screw access channel pathway, projecting 2 mm to 3 mm past the abutment (Figure 2). As a separating medium, Vaseline® is liberally applied to the abutments and surrounding dentition. Visio™-Form gel is then incrementally applied (Figure 3) and preliminary cured with a hand-held light-cure unit (Figure 4). A “bridge” is then built from one abutment to the next (Figure 5). Final curing is accomplished with a stationary, broadband light-curing unit (Metalight, Primotec®, Figure 6).



The index is removed from the model (Figure 7), and the number 8 gauge wax sprue is steamed out of the index. Any sharp corners are removed with a rubber wheel, and the index is reseated onto the abutments and model (Figure 8). Then, the the screw access channel should be inspected through the index material for adequate access to the abutment screws with a screw driver.

The finished seating index will need to be sterilized with a cold sterilizing product (CaviCide®, Metrex) prior to intraoral use.

Bios

Robert E. Kreyer, CDT, is a member of the American Prosthodontic Society and is the author of numerous published articles on removable prosthetics. Robert is a registered continuing education (CE) provider for the Dental Board of California and the National Board of Certification in Dental Technology. Robert is the Director of Removable Prosthodontics for MicroDental in Dublin, CA, and he teaches CE courses in removable prosthetics for Ivoclar Vivadent at the Implant Esthetics Center of Excellence (IECE) in Sarasota, FL. He can be reached at www.PersonalizedDenture.com.

Jochen Könneker is a certified dental technician (Dental Technician Guild, lower Saxony, Hannover 1986) from Germany, first introduced to the field of implant technology more than 20 years ago as an in-house, all-around technician for a prosthodontist in Beverly Hills, CA. Today, he leads the implant department at MicroDental in Dublin, CA. Jochen was granted a fellowship in the ICOI, graduated from Dr. Carl Misch’s International Implant Institute’s prosthetic courses I, II, and III, and founded genieoss.com in 2010.