Influence of the Presence and Type of Post-and-core on the Fatigue Behavior of Crowned Central Incisors

Objectives: This study evaluates the influence of the type and presence of post-and-cores on the fatigue survival of 2 mm ferrule height crowned central incisors.
Methods: The crowns of 69 bovine incisors were cut and the roots were treated endodontically and assigned randomly into three groups (n=23): composite resin buildup (BUP), glass fiber post-retained composite resin buildup (GFP), and AgSn alloy cast post-and-core (CPC). They received full crown preparation with 2-mm ferrule, and a leucite-reinforced ceramic crown was cemented adhesively. Three specimens from each group were tested monotonically. The remaining samples were subjected to the stepwise stress fatigue test until fracture or suspension after 1.5 x 106 cycles in a chewing simulator. The load and step at which each specimen failed were analyzed by Kaplan-Meier and Mantel-Cox (log-rank test) statistics, followed by multiple pairwise comparisons, at 5% significance level.
Results: There was no statistical difference between the treatments regarding the load or the number of cycles (Mantel-Cox log-rank test for trend, X2=0.015, df=1, p=0.901, X2 =3.171, df=1, p=0.995) (Fig 1 and 2). Crown cracks were the predominant failure mode, and oblique root fractures were only observed in groups GFP and CPC.
Conclusions: In endodontically treated incisors containing 2-mm ferrule, the presence and type of post and core system had no significant effect on fatigue survival. Non-restorable fractures only occurred in teeth restored with posts. Although the clinical significance of in vitro studies has some limitations, this study suggests that composite buildups without posts may be an option for restoring endodontically treated incisors with 2 mm ferrule height.