Fracture strength of monolithic and glass-soldered ceramic subcomponents of 5-unit fixed dental prosthesis

Purpose

Zirconium dioxide ceramic has been successfully introduced as a framework material for fixed dental prostheses. To reduce manufacturing constraints, joining of subcomponents could be a promising approach to increase the mechanical performance of long-span fixed dental prostheses. In this experimental study, the biomechanical behavior of monolithic and soldered framework specimens for fixed dental prostheses made of Y-TZP was investigated.

Materials and methods

Framework specimens (n = 80) of 5-unit fixed dental prostheses made of Y-TZP were prepared and divided into 10 equal groups. The specimens were monolithic or composed of subcomponents, which were joined using a silicate-based glass solder. Thereby, three joint geometries (diagonal, vertical with an occlusal cap, and dental attachment-based) were investigated. Moreover, the groups differed based on the mechanical test (static vs. dynamic) and further processing (veneered vs. unveneered). The framework specimens were cemented on alumina-based jaw models, where the canine and second molar were acting as abutments before a point-load was applied. In addition, µCT scans and microscopic fractography were used to evaluate the quality of soldered joints and to determine the causes of fracture.

Results

The determined fracture loads of the different unveneered framework specimens in static testing did not vary significantly (p = 1). Adding a veneering layer significantly increased the mechanical strength for monolithic framework specimens from 1196.29 ± 203.79 N to 1606.85 ± 128.49 N (p = 0.008). In case of soldered specimens with a dental attachment-based geometry, the mechanical strength increased from 1159.42 ± 85.65 N to 1249.53 ± 191.55 N (p = 1). Within the dynamic testing, no differences were observed between monolithic and soldered framework specimens. µCT scans and fractography proved that the dental attachment-based joining geometry offers the highest quality.

Conclusion

Using glass soldering technology, subcomponents of 5-unit framework specimens made of Y-TZP could be joined with mechanical properties comparable to those of monolithic frameworks.