Implant-supported restorations are firmly anchored into the bone. That is why it is important for implants to be made with restoration materials that are able to absorb chewing forces, minimizing the risk of overstressing the antagonist, the restoration and the peri-implant bone. The natural hard tooth substance is a balanced hybrid made of resistant enamel and equally elastic dentin. Dentist Dr. Mauro Fazioni and Dental Technician Andrea Lombardo explain how this natural recipe for success can be transferred to implant-supported crown restorations. In the following case, the authors used two different CAD/CAM materials for the superstructures: the hybrid ceramic VITA ENAMIC IS and the feldspar ceramic VITABLOCS TriLuxe forte (both: VITA Zahnfabrik, Bad Säckingen, Germany), in order to intelligently combine elasticity and wear resistance.
1. Patient case and material selection
A 32-year-old patient presented at the practice with two persistent primary teeth that were no longer worth preserving, as they had failed to attach to tooth 35 and 45. After a thorough consultation, the patient decided to have the deciduous teeth extracted and undergo an implant restoration. In order to reproduce the elastic dentin, the abutments were scheduled to be fabricated individually from the hybrid ceramic VITA ENAMIC IS, due to its dentin-like elasticity. The pre-integrated interface allowed for efficient CAD/CAM-supported fabrication and guaranteed a precise fit to the titanium base. Reproducing the play of colors and light, as well as the functional properties of the mineral enamel was to be achieved using crowns made of the polychrome feldspar ceramic VITABLOCS TriLuxe forte.
2. Surgery and CAD design
The two deciduous teeth were extracted under local anesthesia. After a healing period of three months, two Ankylos implants were inserted at tooth 35 and 45. After healing and exposure of the implants, scanbodies were placed and the situation was digitalized using the Omnicam. Using the inLab software (all: Dentsply Sirona, Bensheim, Germany), abutments and crowns could now be designed in line with the natural tooth structure and then produced with the CAD/CAM materials VITA ENAMIC IS and VITABLOCS TriLuxe forte. The coronal margins were not created subgingivally, in order to ensure a simple and clean adhesive cementation of the crowns under the rubber dam. Additive manufacturing was used to produce a model with integrated implant analogs to check the fit (XFAB, DWS, Vicenza, Italy).
3. CAM production of implant-retained dentures
After CAM production, manual finishing and a check of the fitting, the hybrid ceramic abutments were adhesively bonded to the titanium base. For this purpose, the adhesive surfaces of the abutment were etched with hydrofluoric acid (5%) for 60 seconds and then silanized. The adhesive surfaces of the titanium bases were blasted with 50μm aluminum oxide at 1.5bar, and a metal primer was applied. The adhesive bonding was done using an opaque composite cement. After hardening and removal of the excess, the final hardening was completed under glycerine gel, in order to prevent an oxygen inhibition layer from forming. Finally, the fissures of the CAM-fabricated and manually prepared feldspar ceramic crowns were characterized with the ceramic stains VITA AKZENT PLUS EFFECT STAINS 06 (russet) and then glazed with glaze paste.
4. Try-in, final result and conclusion
The clinical try-in showed perfectly healthy soft tissue conditions and a smooth fit of the restorations after the removal of the gingiva former, and were ready to be prepared for final seating. To achieve this, the adhesive surfaces of the abutments and crowns were etched extraorally with hydrofluoric acid and silanized. After the abutments were screwed in, a rubber dam was placed. The crown was then adhesively bonded to the abutment intraorally. The fulladhesive bond between the hybrid ceramic abutment and the feldspar ceramic crown resulted in a biomimetic unit that reproduced the tooth structure very well, both esthetically and functionally. Thanks to the chewing-force absorbing properties of the hybrid ceramic, good long-term durability is expected for this restoration. The integrated color gradient in the feldspar ceramic crowns give this monolithic restoration an esthetically convincing look.
This article was initially published in the CAD/CAM International Magazine of Digital Dentistry, Italian edition no. 02/2019.