IADR Abstract Archives
Fracture Resistance of Compromised Teeth Restored Adhesively With Hybrid Ceramics
Objectives: The use of contemporary adhesive resin cements and hybrid-ceramics may offer conservative approaches to restoring teeth with a reduced number of walls. This study aimed to evaluate the fracture resistance of teeth restored with crowns fabricated using both additive and subtractive manufacturing processes and adhesively bonded.
Methods: Forty-five extracted human maxillary premolars were divided into three groups (n=15): 1) control group; 2) absence of proximal walls restored with CAD-CAM hybrid-ceramic (Shofu); 3) absence of proximal walls restored with 3D-printed hybrid-ceramic crowns (VarseoSmile). Crowns were bonded with resin-adhesive cement. All specimens were subjected to compression testing under thermocycling conditions using a chewing simulator; 600,000 cycles at a load of 110 N and at 5°C to 55°C. The compressive axial load was applied until the specimen fractured and was recorded as the maximum force value. All specimens were assessed for marginal integrity using micro-CT before and after chewing simulation. Data were analyzed with one-way ANOVA followed by Tukey's test (α=0.05).
Results: CAD-CAM crowns exhibited a significantly higher number of cycles-to-failure than 3D-printed crowns (63,644.5±4,870 vs. 52,486.4±4,921, P<0.001). The fracture load of CAD-CAM crowns was higher than that of 3D-printed crowns (877.3 N vs. 742.5 N). The mode of failure was predominantly Type I and Type II in the CAD-CAM group and Type III in the 3D-printed group. Around 25% of the 3D-printed crowns showed complete failure of restoration (Type IV). No fractures were observed in the tooth substrate. The marginal gap (MG) values differed significantly between the two groups. In the CAD-CAM group, MG ranged between 71.2±4.4 μm to 93.6±3.8 μm, while in the 3D-printed group, it ranged between 36.6±3.2 μm to 59.2±3.9 μm.
Conclusions: CAD-CAM hybrid crowns demonstrated higher fracture resistance and lower MG values than 3D-printed crowns. Both materials demonstrated favorable MG within a clinically acceptable range. The use of hybrid ceramics and adhesive cementation may be recommended for teeth with compromised structural integrity.
Methods: Forty-five extracted human maxillary premolars were divided into three groups (n=15): 1) control group; 2) absence of proximal walls restored with CAD-CAM hybrid-ceramic (Shofu); 3) absence of proximal walls restored with 3D-printed hybrid-ceramic crowns (VarseoSmile). Crowns were bonded with resin-adhesive cement. All specimens were subjected to compression testing under thermocycling conditions using a chewing simulator; 600,000 cycles at a load of 110 N and at 5°C to 55°C. The compressive axial load was applied until the specimen fractured and was recorded as the maximum force value. All specimens were assessed for marginal integrity using micro-CT before and after chewing simulation. Data were analyzed with one-way ANOVA followed by Tukey's test (α=0.05).
Results: CAD-CAM crowns exhibited a significantly higher number of cycles-to-failure than 3D-printed crowns (63,644.5±4,870 vs. 52,486.4±4,921, P<0.001). The fracture load of CAD-CAM crowns was higher than that of 3D-printed crowns (877.3 N vs. 742.5 N). The mode of failure was predominantly Type I and Type II in the CAD-CAM group and Type III in the 3D-printed group. Around 25% of the 3D-printed crowns showed complete failure of restoration (Type IV). No fractures were observed in the tooth substrate. The marginal gap (MG) values differed significantly between the two groups. In the CAD-CAM group, MG ranged between 71.2±4.4 μm to 93.6±3.8 μm, while in the 3D-printed group, it ranged between 36.6±3.2 μm to 59.2±3.9 μm.
Conclusions: CAD-CAM hybrid crowns demonstrated higher fracture resistance and lower MG values than 3D-printed crowns. Both materials demonstrated favorable MG within a clinically acceptable range. The use of hybrid ceramics and adhesive cementation may be recommended for teeth with compromised structural integrity.