Fatigue properties of three-unit fixed dental prostheses using CAD/CAM glass-fiber-reinforced plastics

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Purpose : The clinical potential of machinable CAD/CAM glass-fiber-reinforced plastics (GFRP) was evaluated using three-point bending and three-unit fixed dental prosthesis (FDP) fatigue tests.

Materials and Methods : For the GFRP framework materials, KZR-CAD Fiber Block Frame (green ; FG, ivory ; FI), and TRINIA (TR) were used for subtractive manufacturing, whereas EXPERIA Fiber C & B (EF) was used as a conventional hand-fabricated material. For the resin veneering materials, KZR-CAD HR Block Long Hard (LH) and SHOFU DISK HC (HC) were used as subtractive manufacturing materials, whereas TWINY (TW), CERAMAGE DUO (CE), and EXPERIA (ER) were used as conventionally hand-fabricated materials. Flexural strength and modulus were measured after 7-day immersion in 37℃ water. FDPs were designated as TWB and LHB when using TW and LH resin veneer materials, respectively. Additionally, FDPs using KZR-CAD Fiber Block Bridge (FB) were designated FBB, and FDPs using the conventional framework EF were designated EFB. Fatigue testing (2×10⁶ cycles) applied vertical loads to the pontic in 37℃ water, and the maximum endurance load at which three specimens survived.

Results : Flexural strength and flexural modulus were highest for FG and LH in GFRP and veneering resins, respectively. Maximum endurance loads were 1210 N (LHB), 1080 N (FBB), 1022 N (TWB), and 726 N (EFB). All fatigue failures were confined to the veneering resin, without retainer detachment, catastrophic fracture, or framework fracture.

Conclusions : FDPs using CAD/CAM GFRP frameworks showed higher fatigue strength than FDPs using conventional GFRP. Furthermore, the destructive patterns of FDP indicated the possibility of intraoral repair, high clinical utility.