Fracture resistance/fatigue and static loading Failure mode/observational
N
Mean fracture resistance: Group 1 (A): (927,6 ± 275,6) Group 2 (B): (616,5 ± 154,9) Group 3 (C): (967,9 ± 157,5) Group 1 and Group 3: () Group 2: (, Table 1). Group 1 (A): 6 cases of repairable fracture, 4 cases of irrepairable fracture Group 2 (B): 7 cases of irrepairable fracture Group 3 (C): 9 cases of irrepairable fracture
Integrated CAD/CAM restoration of glass fiber post and core for widened root canals can increase the fracture resistance of the root and reduce the occurrence of irrepairable root fractures.
Bond strength/push-out test Cement layer thickness/SEM Nanoleakage/interfacial nanoleakage in AgNO3
MPa μm
Bond strength: Group 1: (8,19 ± 3,62) Group 2: (26,41 ± 18,77) Group 3: (17,12 ± 7,73) Cement thickness: Group 1: (654 ± 22,5) Group 2: (106 ± 53) Group 3: (162 ± 24) Average nanoleakage values: Group 1: 4 (>75% with nanoleakage) Group 2: 1 (25% of the interface shows nanoleakage) Group 3: 3 (50% to <75% with nanoleakage)
CAD/CAM GFP could represent a valid alternative to posts traditionally used in the restoration of endodontically treated teeth with oval or wide root canals, offering the advantages of better esthetics, retention, and cement thickness values that are comparable to cast posts.
Fracture resistance: Group 1 (RXP): (426.08 ± 128.26) Group 2 (BLC): (367.06 ± 72.34) Group 3 (AMC): (620.02 ± 54.29) Group 1: mixed failure Groups 2 and 3: cohesive failures with no catastrophic failures reported in all groups.
The one-piece post and core can be successfully milled from FRR blocks and high-density polymer material discs using CAD/CAM technology. High-density polymer CAD/CAM GFP showed a better performance than prefabricated fiber posts.
Group 2 (PPn): Cervical: 220.5(76.7) Middle: 204.2(66.5) Apical: 180.1(64.7) Group 4 (CPn): Cervical: 121.0(45.1) Middle: 121.5(29.7) Apical: 112.3(35.6) Fracture resistance: Group 1 (PPc): 716.9 (260.8) Group 2 (PPn): 640.4 (171.9) Group 3 (CPc): 778.0 (232.5) Group 4 (CPn): 792.9 (265.3) Groups 1 and 3 did not show any visible damage (type 0). Type 4 (catastrophic) fractures occurred in Groups 4 and 1.
CAD/CAM GFP do not affect the fracture resistance of widened root canals or cause catastrophic root failure when the tooth is rehabilitated with zirconia crowns.
No statistically significant difference was found in fracture resistance under oblique loading in the case of hybrid CAD/CAM blocks and fiber posts were used, in both the ferrule and no-ferrule groups. The failure mode distribution of the group without ferrule effect did not present unfavorable failures, while the failures in the ferrule groups were distributed between the favorable and unfavorable groups.
Hybrid CAD/CAM blocks can be considered as an alternative restoration system for post and core restorations. More clinical and laboratory research needs to be done to support the improvement of this system.
Bond strength/push-out test Failure mode/stereo microscope
MPa
Bond strength was significantly lower in Group 3 (RXP) (8.54 ± 3.35 MPa) compared to Group 1 (CP) (12.10 ± 1.38 MPa), while no significant differences were found between the other groups. The failure was mainly adhesive for Groups 2 and 3 and adhesive and mixed for Group 1.
The use of CAD/CAM custom FRRP has a positive effect on bond strength to root canal walls compared to prefabricated GFP. Self-adhesive resin cements to radicular dentin did not significantly improve the bond strength of prefabricated posts, where friction appears to play a predominant role in post retention.
Bond strength/micro-CT Failure mode/stereo microscope
MPa
Bond strength: CAD/CAM GFPgroups Group 1 (BLC): (12.43 ± 2.15) Group 2 (AMC): (10,65 ± 1,77) Prefabricated GFPgroups Group 3 (BLP): (9,67 ± 2,98) Group 4 (RXP): (8,91 ± 3,09) The failures were adhesive between the cement and dentin for all groups except Group 2, where an adhesive failure was observed between the cement and the post.
CAD/CAM manufacturing technology improved post retention in the root canal and enabled a complete digital workflow compared to GFP. Fiber-reinforced composites performed better than high-density polymers in terms of resistance to adhesive failure between post and cement. Aging did not affect the bond strength of GFP and CAD/CAM GFP to radicular dentin.
