The Effect of Load Angulation on Fracture Resistance of Teeth Restored With Cast Post and Cores and Crowns

The purpose of this study was to determine if loading post-restored teeth at different angles would affect their resistance. Thirty maxillary central incisors were treated endodontically to within 5.0 mm of the apex. Standardized cast post and cores were fabricated using plastic #4 Parapost patterns. Post and cores were cemented using zinc phosphate cement followed by crowns of average dimensions. Ten teeth each were loaded at 110, 130, and 150 degrees to the long axis of the tooth. Mean failure loads were:110 degrees = 372.4 N± 140.8 (SD); 130 degrees = 597.6 N±138.5 (SD); 150 degrees = 1274.3 N±429.9 (SD). There were significant differences in fracture resistance between teeth tested at the following angles: 110 degrees versus 150 degrees (P.0001), and 130 degrees versus 150 degrees (P.0001), but not for 110 degrees versus 130 degrees (P=.2016). Mean failure loads increased as load angle approached parallelism to the long axis of the teeth. Significant differences in fracture resistance of post restored teeth can occur as a result of load angle.