Influence of Post Length, Post Material, and Substance Loss on the Fracture Resistance of Endodontically Treated Teeth : A Laboratory Study

There is little scientific data available about the influence of the three factors post length, post material, and substance loss on the fracture resistance of endodontic treated teeths (ETTs). The purpose of this laboratory study was to evaluate the influence of post length, post material, and substance loss evaluated by comparing 1 with 2 residual dentinal walls on the fracture resistance of endodontically treated mandibular premolars.

 A total of 96 extracted human mandibular first premolars were endodontically treated and divided into 12 test groups (n=8 each) based on the number of residual walls (one/two), post material glass fiber (GF), titanium (TI), and post length (5 mm, 7.5 mm, and 10 mm). After luting the posts, specimens received a composite resin core and a crown preparation with a 1.5 mm ferrule. Cast cobalt-chromium crowns were cemented using glass-ionomer cement. After 1,200,000 loading cycles in a chewing simulator with a load of 49 N and simultaneous thermocycling (5 °C to 55 °C), specimens were quasi-statically loaded at 30 degrees to the longitudinal axis of the tooth until fracture. Fracture loads were analyzed using three-way, two-way, and one-way analysis of variance (α=.05). Fracture modes were examined under a stereomicroscope (×25) and recorded.

The fracture loads ranged from 642 ±190 N (one wall, GF, 5 mm) to 1,170 ±130 N (two walls, TI, 7.5 mm). The mean fracture load of TI posts was significantly higher than that of GF posts (P≤.001), and the 7.5 mm post length exhibited significantly higher fracture loads than groups with 5 mm and 10 mm post length (P=0.008). It can be concluded that the teeth restored with TI posts provide considerably higher fracture resistance than teeth restored with GF posts, especially if 7.5 mm-length posts are used.