Biomechanical Effect of Teeth Restored With Fiber-glass Post With/Without Ferrule

Objectives: This study evaluated the integrity, strain and fracture resistance of endodontically treated incisors restored using a fiber-glass post with and without ferrule after thermal and mechanical aging.
Methods: Twenty bovine incisors were divided into two groups (n=10): ‘Fe’ with ferrule of 2 mm, ‘NFe’ without ferrule. After endodontic treatment, the teeth were restored using a fiber-glass post (Exacto 3, Angelus Science and Technology) and composite core (Tetric Ceram, Ivoclar-Vivadent); they received a CAD-CAM lithium disilicate ceramic crown (IPS e.max CAD, Ivoclar-Vivadent) luted using the self-adhesive composite cement (RelyX Unicem 2, 3M ESPE). All specimens were subjected to 20,000 thermo-cycles and 2,400,000 simulated chewing cycles. The micro-strain (‘µS’) was measured by using strain gauges placed on the buccal crown, buccal root and lingual root surfaces, before and after aging. Specimens were subsequently loaded to fracture (fracture resistance in N). Data were analyzed by two-way ANOVA, followed by Tukey HSD testing (α=0.05).
Results: The buccal crown µS was 13.8±5.4^Aa for ‘Fe’ and 12.8±5.2^Aa for NFe before aging, and 13.4±4.0^Aa for ‘Fe’ and 16.8±3.1^Aa for ‘NFe’ after aging. The buccal root µS was 437.8±178.1^Aa for ‘Fe’ and 611.1±282.8^Aa for ‘NFe’ before aging, and 554.0±233.8^Ab for ‘Fe’ and 1248.0±282.8^Bb for ‘NFe’ after aging. The lingual root µS was 221.4±81.7^Aa for ‘Fe’ and 236.7± 59.7^Aa for ‘NFe’ before aging, and 311.8±159.0^Ab for ‘Fe’ and 516.2±195.0^Bb for ‘NFe’ after aging. The fracture resistance was 1099.6±214.8^A N for ‘Fe’ and 675.3±113.8^B N for ‘NFe’. Different superscript uppercase and lowercase letters indicate significant difference for aging and ferrule, respectively.
Conclusions: While no difference in strain was recorded upon aging with a ferrule, significantly higher root strains were measured without a ferrule upon aging. Likewise, the fracture resistance of the restored teeth was significantly lower without a ferrule.