IADR Abstract Archives
Fatigue Loading Crowns with Different Core Buildup Techniques without Ferrule
Objectives: This study evaluated the performance of full coverage restorations on structurally compromised teeth with different core buildups cycled under incrementally increasing loads using a dynamic chewing simulator. Internal stress patterns contributing to failure were analyzed with optical coherence tomography (OCT; Yoshida Dental MFG).
Methods: 16 extracted human premolars were root canal treated and randomly divided into 4 groups to receive core buildups. G1: 2mm ferrule, 2mm composite core (Clearfil PhotoCore, Kuraray Noritake Dental). G2: no ferrule, 4mm composite core with peripheral reinforcement by continuous fiber (Ribbond Ultra, Ribbond). G3: no ferrule, 4mm composite core. G4: no ferrule, fiber post (ParaPost Fiber, Coltene) with composite core. Specimens were prepared with 1mm margins and received full coverage lithium disilicate crowns (IPS e.max CAD, Ivoclar Vivadent). Specimens mounted in a dynamic chewing simulator (CS-4.4, SD Mechatronik) were initially loaded with 10kg with 5kg of additional weight added every 250,000 cycles until continuous loading with 25kg produced catastrophic failure. OCT imaging was conducted at the conclusion of each set of 250,000 cycles from proximal, buccal, lingual, and occlusal views.
Results: There was significant difference among groups. Specimens without ferrule receiving either composite core or composite core with fiber post performed similarly, with some specimens failing during the incremental loading stage. Continuous fiber-reinforcement within core buildups provides significantly increased performance compared to fiber posts or composite alone. The ferrule group showed highest survival. Catastrophic failures were primarily initiated in the lithium disilicate crown itself or the lingual restorative margin.
Conclusions: Ferrule remains an important factor in the structural integrity of full coverage crowns. Continuous fiber reinforcement of core composite distributes stresses peripherally and may provide an alternative restorative option for structurally compromised teeth and no ferrule. Failures observed were caused by microcracks within the crown that led to complete fracture or cement debonding due to lingual tensile forces.
Methods: 16 extracted human premolars were root canal treated and randomly divided into 4 groups to receive core buildups. G1: 2mm ferrule, 2mm composite core (Clearfil PhotoCore, Kuraray Noritake Dental). G2: no ferrule, 4mm composite core with peripheral reinforcement by continuous fiber (Ribbond Ultra, Ribbond). G3: no ferrule, 4mm composite core. G4: no ferrule, fiber post (ParaPost Fiber, Coltene) with composite core. Specimens were prepared with 1mm margins and received full coverage lithium disilicate crowns (IPS e.max CAD, Ivoclar Vivadent). Specimens mounted in a dynamic chewing simulator (CS-4.4, SD Mechatronik) were initially loaded with 10kg with 5kg of additional weight added every 250,000 cycles until continuous loading with 25kg produced catastrophic failure. OCT imaging was conducted at the conclusion of each set of 250,000 cycles from proximal, buccal, lingual, and occlusal views.
Results: There was significant difference among groups. Specimens without ferrule receiving either composite core or composite core with fiber post performed similarly, with some specimens failing during the incremental loading stage. Continuous fiber-reinforcement within core buildups provides significantly increased performance compared to fiber posts or composite alone. The ferrule group showed highest survival. Catastrophic failures were primarily initiated in the lithium disilicate crown itself or the lingual restorative margin.
Conclusions: Ferrule remains an important factor in the structural integrity of full coverage crowns. Continuous fiber reinforcement of core composite distributes stresses peripherally and may provide an alternative restorative option for structurally compromised teeth and no ferrule. Failures observed were caused by microcracks within the crown that led to complete fracture or cement debonding due to lingual tensile forces.