33798
document
Effect of a ferrule and increased clinical crown length on the in vitro fracture resistance of premolars restored using two dowel-and-core systems . This study investigated the effect of a crown-lengthening ferrule on the fracture resistance of endodontically-treated teeth restored with two dowel-core systems . Thirty-two extracted mandibular first premolars were sectioned perpendicular to the long axis at a point 1.0 mm occlusal to the buccal cementoenamel junction . Following endodontic treatment , the teeth were randomly assigned to four groups : cast Ni-Cr alloy dowel-core with no ferrule ( Group A1 ) , cast Ni-Cr alloy dowel-core with 2.0 mm ferrule ( Group A2 ) , prefabricated carbon fiber-reinforced dowel-resin core with no ferrule ( Group B1 ) and carbon fiber-reinforced dowel-resin core with 2.0 mm ferrule ( Group B2 ) . Each specimen was embedded in a self-cured acrylic resin block from 2.0 mm apical to the margins of a cast Ni-Cr alloy crown , then loaded at 150 degrees from the long axis in a universal testing machine at a crosshead speed of 1.0 mm/minute until fracture . The data were recorded and analyzed using ANOVA and Fisher 's exact tests , with alpha = 0.05 . Mean failure loads ( kN ) for the A1 , A2 , B1 and B2 Groups were : 1.46 ( S.D . 0.45 ) , 1.07 ( 0.21 ) , 1.13 ( 0.30 ) and 1.02 ( 0.27 ) . The teeth restored with cast Ni-Cr dowel-cores and 2.0 mm ferrules demonstrated significantly lower fracture strengths , p = 0.04 . There were significant differences in the root fracture patterns between the two dowel systems , with the carbon fiber-reinforced dowel-resin core system , being the less severe p < 0.05 . Crown lengthening with a 2.0 mm apical extended ferrule resulted in reduced fracture strengths for endodontically-treated teeth restored using two dowel-core systems and cast metal crowns . The carbon fiber-reinforced dowel-resin core system reduced the severity of the root fractures .
33799
Intervention_Pharmacological
ferrule
33800
Intervention_Pharmacological
crown-lengthening ferrule
33801
Intervention_Pharmacological
cast Ni-Cr alloy dowel-core with no ferrule ( Group A1 ) , cast Ni-Cr alloy dowel-core with 2.0 mm ferrule ( Group A2 ) , prefabricated carbon fiber-reinforced dowel-resin core with no ferrule ( Group B1 )
33802
Intervention_Pharmacological
carbon fiber-reinforced dowel-resin core with 2.0 mm ferrule
33803
Intervention_Pharmacological
cast Ni-Cr dowel-cores and 2.0 mm ferrules
33804
Intervention_Pharmacological
carbon fiber-reinforced dowel-resin core system
33805
Intervention_Pharmacological
2.0 mm apical extended ferrule
33806
Outcome_Physical
ANOVA and Fisher 's exact tests
33807
Outcome_Physical
Mean failure loads
33808
Outcome_Physical
fracture strengths
33809
Outcome_Physical
root fracture patterns
33810
Outcome_Physical
fracture strengths
33811
Participant_Sample-size
Thirty-two
33812
Participant_Condition
root fractures