Load fatigue of five restoration modalities in structurally compromised premolars.

Twenty-five freshly extracted maxillary first premolars were divided equally among five modalities for rebuilding structurally compromised premolars. These modalities were: (A) buccal stainless steel Parapost/amalgam core, (B) palatal stainless steel parapost/amalgam core, (C) two stainless steel Paraposts/amalgam core, (D) two regular Link Plus TMS single-shear Minim pins/amalgam core, and (E) palatal cast gold post and core. Load fatigue was used as the testing protocol, using a 5.2-kg load applied at 72 cycles per minute. Each tooth was prepared with a 1.0-mm ferrule, and an upper limit of 250,000 load cycles was set for the testing. Two failures were exhibited, (1) preliminary failure which involved a crack in the luting cement layer, and (2) catastrophic failure wherein the core and crown separated from the root section. Statistical analysis using Kruskal-Wallis test showed three subsets (P < or = .05). The subset with the highest number of load cycles to failure contained the palatal stainless steel post/amalgam core, two stainless steel Paraposts/amalgam core, and palatal cast gold post and core.