Authors
Anna Thereza Peroba Rezende Ramos, Austin Heath, Daler Elisa Tarrazzi, Mateus Garcia Rocha, Rafael Rocha Pacheco
Published in
The Journal of prosthetic dentistry. Oct 09, 2026. Epub Oct 09, 2026.
Abstract
High-translucency 4-mol% yttria-stabilized tetragonal zirconia polycrystal (4Y-TZP) has been increasingly used for implant-supported prostheses because of its superior esthetics, yet connector size recommendations have been derived from studies of stronger conventional 3-mol% Y-TZP. Whether these guidelines remain valid for materials with 30 to 40% lower flexural strength is unknown.
The purpose of this in vitro and finite element study was to evaluate the effect of connector cross-sectional dimensions and span length on the fracture resistance of high-translucency monolithic 4Y-TZP and to characterize stress distribution and concentration at the connector.
Bar-shaped specimens incorporating 4 connector regions were milled from presintered high-translucency 4Y-TZP (KATANA Zirconia HTML PLUS A2). Four connector configurations were tested: 3×3 mm, 4×3 mm, 4×4 mm (elliptical cross-sections), and 5×4 mm (full cross-section control), with cross-sectional areas of 7.1, 9.4, 12.6, and 20.0 mm². The specimens were tested at 2 span lengths (22 and 42 mm) by 3-point bend testing (n=6 per group). Fracture load (N) was recorded, and flexural stress at the connector (MPa) was calculated from the local bending moment and the section modulus appropriate to each cross-sectional geometry. Three-dimensional finite element models determined maximum principal stress (σ₁) and stress concentration factors. Data were analyzed with 2-way analysis of variance (ANOVA), the Tukey honestly significant difference (HSD) test, and the Pearson correlation (α=.05).
Connector configuration (P<.001), span length (P<.001), and their interaction (P<.001) significantly affected fracture load. Mean ±standard deviation fracture load ranged from 208 ±14 N (3×3 mm, 42-mm span) to 1806 ±142 N (5×4 mm, 22-mm span) and correlated strongly with connector area (r≥.979, P<.001). Load gain per mm² of connector area was approximately twice as large for the 22-mm span (98.3 N per mm²) as for the 42-mm span (52.3 N per mm²). When load was converted to flexural stress at the connector, only connector configuration remained significant (P<.001); span length (P=.816) and the interaction (P=.162) were not significant. Connector stress converged into a narrow range (533 to 745 MPa) within published 4Y-TZP flexural strength values. Finite element analysis confirmed stress concentration at the connector base, with σ₁ spanning a factor of only 1.5 (613 to 939 MPa) despite an 8.7-fold range in fracture loads. Under equal applied load, stress concentration factors ranged from 1.67 to 3.92 at the 22-mm span and from 2.62 to 6.42 at the 42-mm span.
Reducing connector area disproportionately decreased fracture load, with greater reduction at longer spans. Connector stress values fell within a narrower range than fracture loads, suggesting that load differences are driven predominantly by geometry.
PMID:
42855390
Bibliographic data and abstract were imported from PubMed on 10 Oct 2026.
Read full publication at:
Please sign in
to see all details.
Advertisement
Stats
- Recommendations n/a n/a positive of 0 vote(s)
- Views 7
- Comments 0