ABSTRACT
AIM: To investigate ex vivo the influence of the post system on fracture resistance and failure mode of root filled incisor, canine, premolar and molar teeth. METHODOLOGY: Eighty human teeth were divided into eight groups (n = 10) resulting from the interaction between the two study factors: post system (glass fibre post; cast Ni-Cr alloy post and core) and type of tooth (maxillary incisors, maxillary canines, maxillary premolars and mandibular molars). All roots were prepared with a 2-mm ferrule and restored with metal crown. Fracture resistance (N) was assessed in a mechanical testing device, and the data were analysed by two-way anova (4 × 2) followed by Tukey's test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. Failure mode data were analysed by two-factor anova and Student-Newman-Keuls (SNK) tests (α = 0.05). Correlation between fracture resistance and failure mode was analysed by linear regression. RESULTS: Glass fibre and cast posts and cores had similar fracture resistance, regardless of the type of tooth. Canines and molars had significantly higher fracture resistance (P < 0.001) than premolars. Incisors teeth had significantly lower fracture resistance (P < 0.001) than premolars. The fracture mode for incisors, premolars and molars was more amenable to restoration when the teeth were restored with glass fibre posts. Fracture resistance had no correlation with fracture mode, regardless of the post system and type of tooth analysed. CONCLUSIONS: Post system had no significant effect on fracture resistance, regardless of the type of tooth. The mode of fracture was more restorable with glass fibre posts.
Subject(s)
Post and Core Technique , Tooth Fractures/physiopathology , Tooth, Nonvital/physiopathology , Acid Etching, Dental/methods , Bicuspid/physiopathology , Biomechanical Phenomena , Chromium Alloys/chemistry , Composite Resins/chemistry , Crowns , Cuspid/physiopathology , Dental Cements/chemistry , Dental Materials/chemistry , Dental Stress Analysis/instrumentation , Glass/chemistry , Humans , Incisor/physiopathology , Mandible , Materials Testing , Maxilla , Molar/physiopathology , Phosphoric Acids/chemistry , Root Canal Preparation/methods , Stress, MechanicalABSTRACT
AIM: To investigate ex vivo the influence of gamma irradiation therapy and restorative material on fracture resistance, fracture mode and strain of root filled human premolars. METHODOLOGY: Sixty extracted human maxillary premolar teeth were randomly divided into six groups (n = 10) determined by two study factors: (i) restorative materials: sound teeth, root filled teeth restored with composite resin, root filled teeth restored with amalgam; (ii) gamma irradiation: irradiated (subjected to 60 Gy of gamma irradiation in daily increments of 2 Gy) and nonirradiated. For the strain gauge test, two strain gauges per sample were attached on the buccal and palatal cusp surfaces (n = 5). Strain values were recorded during loading of 0-150 N. Fracture resistance (N) was assessed in a mechanical testing machine (n = 10). Strain gauge for each cusp and fracture resistance data were analysed by two-way anova (3 × 2) followed by the Tukey's honestly significant difference test (α = 0.05). The failure mode was evaluated using an optical stereomicroscope and classified according to the location of the failure. RESULTS: Gamma radiation therapy significantly reduced the fracture resistance of intact teeth. The strain was higher for teeth restored with amalgam than for those restored with composite resin. The teeth restored with composite resin had similar strain values to sound teeth. Nonirradiated teeth had more restorable failures than irradiated teeth. CONCLUSIONS: Gamma irradiation significantly reduced fracture resistance and increased cusp strain. The use of composite resin resulted in better biomechanical behaviour than amalgam for restoring root filled teeth whether or not they were submitted to radiotherapy.
