Bending moments of zirconia and titanium implant abutments supporting all‐ceramic crowns after aging

Abstract

Objectives To test the fracture load and fracture patterns of zirconia abutments restored with all‐ceramic crowns after fatigue loading, exhibiting internal and external implant–abutment connections as compared to restored and internally fixed titanium abutments. Materials and methods A master abutment was used for the customization of 5 groups of zirconia abutments to a similar shape (test). The groups differed according to their implant–abutment connections: one‐piece internal connection (BL; Straumann Bonelevel), two‐piece internal connection (RS; Nobel Biocare ReplaceSelect), external connection (B; Branemark MkIII), two‐piece internal connection (SP, Straumann StandardPlus) and one‐piece internal connection (A; Astra Tech AB OsseoSpeed). Titanium abutments with internal implant–abutment connection (T; Straumann Bonelevel) served as control group. In each group, 12 abutments were fabricated, mounted to the respective implants and restored with glass–ceramic crowns. All samples were embedded in acrylic holders (ISO‐Norm 14801). After aging by means of thermocycling in a chewing simulator, static load was applied until failure (ISO‐Norm 14801). Fracture load was analyzed by calculating the bending moments. Values of all groups were compared with one‐way ANOVA followed by Scheffé post hoc test (P‐value<0.05). Failure mode was analyzed descriptively. Results The mean bending moments were 464.9 ± 106.6 N cm (BL), 581.8 ± 172.8 N cm (RS), 556.7 ± 128.4 N cm (B), 605.4 ± 54.7 N cm (SP), 216.4 ± 90.0 N cm (A) and 1042.0 ± 86.8 N cm (T). No difference of mean bending moments was found between groups BL, RS, B and SP. Test group A exhibited significantly lower mean bending moment than the other test groups. Control group T had significantly higher bending moments than all test groups. Failure due to fracture of the abutment and/or crown occurred in the test groups. In groups BL and A, fractures were located in the internal part of the connection, whereas in groups RS and SP, a partial deformation of the implant components occurred and cracks and fractures of the zirconia abutment were detected. Conclusion The differently connected zirconia abutments exhibited similar bending moments with the exception of one group. Hence, the type of connection only had a minor effect on the stability of restored zirconia abutments. In general, restored titanium abutments exhibited the highest bending moments.

Lithium Disilicate Restorations Fatigue Testing Parameters: A Systematic Review

“…Two papers did not detail the loading parameters, in terms of magnitude of force and number of cycles applied Five studies tested materials other than LD Three studies used flat layer specimens …”

Cemented vs screw‐retained zirconia‐based single implant reconstructions: A 3‐year prospective randomized controlled clinical trial

“…[23][24][25][26] In contrast, clinical information from a systematic review showed no statistically significant difference in the fracture rate between ceramic abutments with internal and external connection designs (5-year complication summary estimate: 1.9% for internal and 2.0% for external connections). Based on in vitro studies, a less predictable behavior and lower bending moments of internally compared to externally connected zirconia abutments were observed.…”

Reliability and Failure Modes of a Hybrid Ceramic Abutment Prototype

“…Ceramic abutments, particularly zirconia (Y‐TZP), were developed to allow improved esthetics . However, concerns related to strength and fatigue resistance when compared to metal abutments have been raised with a recent laboratory study, indicating the superiority of the titanium systems compared to the range of zirconia abutment to metal approaches . Muhleman et al evaluated the strength (bending moment) to failure of four zirconia abutment to metal fixture systems with an IPS Empress CAD crown following low load (49 N), high cycle fatigue (1,200,000 cycles).…”