Influence of bionic microstructures on the bond strength of additively manufactured zirconia
Sun Manlin1, Tan Xin2, Zhang Na3
1Graduate student, State Key Laboratory of Oral Diseases, National Center for Stomatology, National Clinical Research Center for Oral Diseases, Department of Prosthodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, Sichuan, PR China.
Statement Of Problem:
Additively manufactured (AM) zirconia restorations have been increasingly adopted in clinical practice, enabling the fabrication of microstructures on the intaglio surfaces of restorations. However, the potential of microstructures to replace methylacryloyloxydecyl-dihydrogenphosphate (MDP) bonding remains uncertain, and the influence of microstructural morphology design on mechanical bonding strength requires further investigation.
Purpose:
The purpose of this in vitro study was to investigate the effects of microstructural diameter, depth, and spacing on the resin-bonded mechanical strength of AM zirconia, the ultimate forming capabilities of microstructures on stereolithography (SLA), and the impact of bionic microstructures on the bond strength of AM zirconia.
Material And Methods:
The influence of microstructure dimensions (diameter: 100 to 200 µm, depth: 25 to 100 µm, spacing: 100 to 200 µm) on mechanical bond strength was assessed with finite element analysis (FEA). The ultimate forming capabilities of microstructures on SLA zirconia were also explored. A total of 88 zirconia specimens were prepared, including 66 standard specimens and 22 with bionic microstructures (200 µm diameter, 100 µm depth, 200 µm spacing). Standard specimens underwent 3 abrasion treatments (n=22): non-alumina airborne-particle abrasion (NAB), 50 µm alumina airborne-particle abrasion (50AB), and 110 µm alumina airborne-particle abrasion (110AB). Surface roughness (Ra), contact angle (CA) and surface morphology were analyzed. Specimens were divided into non-MDP (NMDP) and MDP (MDP) subgroups (n=10). Shear bond strength (SBS) and failure type were analyzed 24 hours after bonding. Statistical analyses were performed using a nonparametric approach (Kruskal-Wallis test) for Ra and CA, 2-way ANOVA for SBS, and chi-squared test for failure types (α=.05).
Results:
FEA indicated that diameter, depth, and spacing influenced bond strength and that a Ø200-µm design achieved better bond strength when the spacing was 200 µm. Group MS exhibited the highest Ra (102.21 ±10.95 nm) and lowest CA (37.61 ±2.72 degrees). Without MDP, MS showed significantly higher SBS (P<.001). With MDP, group MS had statistically similar SBS as group 50AB (P >.999) and significantly higher than other groups (P<.001). Within MS, SBS was higher in the subgroup MDP than in NMDP (P<.001).
Conclusions:
Bionic microstructures enhanced bond strength, achieving or surpassing alumina airborne-particle abrasion effects. Combining microstructures with MDP further improved bonding performance.
