Retentive strength of two-piece CAD/CAM zirconia implant abutments

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

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.

Retention Forces between Titanium and Zirconia Components of Two-Part Implant Abutments with Different Techniques of Surface Modification

BACKGROUND

The adhesive connection between titanium base and zirconia coping of two-part abutments may be responsible for the failure rate. A high mechanical stability between both components is essential for the long-term success.

PURPOSE

The aim of the present in-vitro study was to evaluate the influence of different surface modification techniques and resin-based luting agents on the retention forces between titanium and zirconia components in two-part implant abutments.

MATERIALS AND METHODS

A total of 120 abutments with a titanium base bonded to a zirconia coping were investigated. Two different resin-based luting agents (Panavia F 2.0 and RelyX Unicem) and six different surface modifications were used to fix these components, resulting in 12 test groups (n = 10). The surface of the test specimens was mechanically pretreated with aluminium oxide blasting in combination with application of two surface activating primers (Alloy Primer, Clearfil Ceramic Primer) or a tribological conditioning (Rocatec), respectively. All specimens underwent 10,000 thermal cycles between 5°C and 55°C in a moist environment. A pull-off test was then conducted to determine retention forces between the titanium and zirconia components, and statistical analysis was performed (two-way anova). Finally, fracture surfaces were analyzed by light and scanning electron microscopy.

RESULTS

No significant differences were found between Panavia F 2.0 and RelyX Unicem. However, the retention forces were significantly influenced by the surface modification technique used (p < 0.001). For both luting agents, the highest retention forces were found when adhesion surfaces of both the titanium bases and the zirconia copings were pretreated with aluminium oxide blasting, and with the application of Clearfil Ceramic Primer.

CONCLUSION

Surface modification techniques crucially influence the retention forces between titanium and zirconia components in two-part implant abutments. All adhesion surfaces should be pretreated by sandblasting. Moreover, a phosphate-based primer serves to enhance long-term retention of the components.

Basic properties and types of zirconia: An overview

This paper describes types and characteristics of zirconia materials in relation to their applications in dentistry. The zirconia material typically used today by most manufacturers is a tetragonal polycrystalline zirconia, partially stabilized with yttrium oxide. The mechanical properties of zirconia have been extensively investigated in the scientific literature and zirconia clearly measures up to any other equivalent manufactured material. The biocompatibility of zirconia has also been extensively evaluated and no local or systemic adverse reactions or cytotoxic effects have been found in relation to it. However, ceramic bonding, ageing, light transmission and manufacturing processes are all factors that need to be further evaluated in order to guide the successful use of zirconia as a prosthetic restorative material. Milling zirconia to full-contour might be an alternative to traditionally veneered restorations. A potential adhesion mechanism appears to be the combination of air abrasion with aluminum oxide particles (silanated or not), followed by sintering with materials containing special reactive monomers. Changes in zirconia properties before and after the sintering process have also been investigated. It was found that after sintering, surface roughness was greater, and micro hardness was slightly reduced; however, accurate precision of fit was not affected by the sintering process. Currently, zirconia restorations are manufactured by either soft or hard-milling processes, with the manufacturer of each claiming advantages over the other. Chipping of the veneering porcelain is reported as a common problem and has been labeled as its main clinical setback. As zirconia has demonstrated good mechanical and biological performance, future technology is attempting to improve esthetics and minimize veneer fracture, aiming to create confidence in the dental community towards this all-ceramic system. Milling zirconia to full-contour might be an alternative to traditionally veneered restorations. Finally, implications are drawn for manufacturing, machining, and widespread use of these materials.