Abstract

With CAD/CAM fabricated crown abutments it is possible to produce screw-retained single crowns without any use of cement. The dental ceramic is directly veneered to the abutment in the supragingival area. With this technique the zirconia surface is inside the soft tissue area and there is no contact of the dental ceramic to the gingiva. Within the five years period there was only one mechanical (fracture) and no biological complication.

Background and aim

Surplus of cement is discussed as an important etiological factor of early peri-implant diseases.^1,2,3 To eliminate this risk factor zirconia abutments are available. Individualized with dental ceramic they are fixed directly to the implant, using an occlusal access to the screw.

Material and methods

Since 2011 109 crown abutments with five different interfaces (Frialit 2/Xive, Zimmer, Camlog, Astra Tech and Astra Tech EV) were used for the replacement for molars and bicuspids in the maxilla and in the mandible. 74 impressions were made using a closed tray, 35 with an open tray. Stone casts with flexible gingiva masks were manufactured as usual. The crown abutments were designed using a wax-up for all crowns and using a cut-back software to create the space for an optimal thickness of the individual dental ceramic. In the dental laboratory there was a special focus on the proximal contact point. The contact point is created step by step regarding the different indices of the implant systems. A guide splint was made for every restoration to place them exactly to the implants in the final position. Before the fixation of the screws all proximal contact points were checked clinically for the first time. The crown abutments were now directly screwed to the implant, using the recommended torque. The proximal contact point was now checked for a second time. Intraoral X-rays were made to control the precise fit before closing the access hole with composites using the right shade. All restorations were clinically checked in three-month intervals in the first year then followed by an annual check.

Results

All crowns could be placed without corrections of the proximal contact point. After placement a light anemia disappeared after five to ten minutes. Although the dental hygiene was not perfect in some patients, the soft tissue around these crowns showed no clinical sign of inflammation. One abutment on a 3.5 mm Astra Tech implant fractured after a loading period of three months and was replaced by a GoldHue abutment with a full ceramic crown.