Microscopical and chemical surface characterization of CAD/CAM zircona abutments after different cleaning procedures. A qualitative analysis

Abstract

Purpose: To describe and characterize the surface topography and cleanliness of CAD/CAM manufactured zirconia abutments after steaming and ultrasonic cleaning.

Materials and methods: A total of 12 ceramic CAD/CAM implant abutments of various manufacturers were produced and randomly divided into two groups of six samples each (control and test group). Four two-piece hybrid abutments and two one-piece abutments made of zirconium-dioxide were assessed per each group. In the control group, cleaning by steam was performed. The test group underwent an ultrasonic cleaning procedure with acetone, ethyl alcohol and antibacterial solution. Groups were subjected to scanning electron microscope (SEM) analysis and Energy-dispersive X-ray spectroscopy (EDX) to verify and characterize contaminant chemical characterization non-quantitatively.

Results: All zirconia CAD/CAM abutments in the present study displayed production-induced wear particles, debris as well as organic and inorganic contaminants. The abutments of the test group showed reduction of surface contamination after undergoing an ultrasonic cleaning procedure. However, an absolute removal of pollutants could not be achieved.

Conclusion: The presence of debris on the transmucosal surface of CAD/CAM zirconia abutments of various manufacturers was confirmed. Within the limits of the study design, the results suggest that a defined ultrasonic cleaning process can be advantageously employed to reduce such debris, thus, supposedly enhancing soft tissue healing. Although the adverse long-term influence of abutment contamination on the biological stability of peri-implant tissues has been evidenced, a standardized and validated polishing and cleaning protocol still has to be implemented.

Keywords: Abutment surface; CAD/CAM zirconia abutments; Energy Dyspersive X-ray spectroscopy (EDX); Hybrid abutments; Peri-implant soft tissue response; Spectral-Electron-Microscopy (SEM); Surface contamination; Surface topography; Ultrasonic cleaning.

Fig. 1. The six one- and two-piece ceramic CAD/CAM abutments examined in the test and control group (left to right): Sample 1: Compartis (Dentsply Degudent, Hanau, Germany) CAD/CAM zirconia coping on titanium insert with implant-abutment connection for Ankylos C implant; Sample 2: Custom milled lithium-disilicate coping (IPS e.max, Ivoclar Vivadent GmbH, Liechtenstein) on titanium insert with implant-abutment connection for Ankylos C/X implant; Sample 3: Bego CADAbut (Bego Medical, Bremen, Germany): Zirconia coping on titanium insert with implant-abutment connection for Semados implant; Sample 4: MedentiCAD (Medentika Implant GmbH, Hügelsheim, Germany): Zirconia coping on titanium insert with implant-abutment connection for Straumann Bone Level implant; Sample 5: Atlantis (Dentsply Implants, Mannheim, Germany): Zirconia abutment including the implant-abutment connection for Astra OsseoSpeed implant; Sample 6: Procera (Nobel Biocare, Zürich, Switzerland): Zirconia abutment including the implant-abutment connection for Nobel Active implant.

Fig. 2. Occlusal view of abutment samples on the respective master cast reveals differently pronounced emergence profiles and variously shaped abutment shoulders, despite mandatory abutment design (standardised wax-up of the abutment from try-in acrylic).

Fig. 3. Example of spectra table of sample 1 (in atom percent): Among others contamination with titanium.

Fig. 4. Severely contaminated surface, distinctive and square-edge groove milling at steam-cleaned status (A-D) of sample 1; after ultra-soniccleaning (E-H) clear particle reduction, but residual machining traces.

Fig. 5. Pictures A-D of steam-cleaned sample 2 show clearly visible contamination and a rippled, rounded edge profile. After ultra-sonic cleaning (E-H) the surface is still rough, but almost free of particles.

Fig. 6. Substantial particle and milling traces on the steam-cleaned sample 3 (A-D); particle-free surface after ultra-sonic cleaning (E-H), but severe roughening and impact traces resulting from CAD/CAM machining.

Fig. 7. Sample 4 before steam-cleaning (A-D) with substantial debris on the cone and the contact surface as well as severely roughened surface and isolated defects. Particles could be removed after the ultra-sonic cleaning process; CAD/CAM milling roughnesses and defects remained (E-H).

Fig. 8. Pictures A-D show steam-cleaned surface status with clearly visible debris and milling grooves. Pictures E-H reveal the reduction of surface contamination after ultrasonic cleaning procedure, with remaining pollutants (Sample 5).

Fig. 9. Sample 6 in steam-cleaned status (A-D) with significant particle debris and distinctive groove milling; after ultra-sonic cleaning (E-H) relatively isotropic surface roughness (picture g: remains of glass after cleaning, probably from internal glass vial used for transport).