Fracture resistance and stress distribution in endodontically treated maxillary premolars restored with composite resin.
OBJECTIVE
The aim of this study was to evaluate the effect of endodontic and restorative treatment on the fracture resistance of posterior teeth.


METHODS
Fifty intact premolars were selected and randomly placed into five groups (n = 10): G1, intact teeth (control); G2, mesial-occlusal-distal (MOD) preparation; G3, MOD preparation restored with composite resin (Z-250, 3M ESPE); G4, MOD preparation and endodontic treatment; and G5, MOD preparation, endodontic treatment, and composite resin restoration. The specimens were submitted to an axial compression load in a mechanical test machine (EMIC), at a speed of 0.5 mm/min. Fracture patterns were analyzed at four levels. Five 2D numerical models were created by Ansys 10.0 for finite element analysis (FEA).


RESULTS
Mean values of compressive strength for all groups were (Kgf): G1 (83.6 +/- 25.4); G2 (52.7 +/- 20.2); G3 (82.1 +/- 24.9); G4 (40.2 +/- 14.2); G5 (64.5 +/- 18.1). Statistical analysis (ANOVA and Tukey's test) showed that fracture resistance of G1 was significantly higher than that of G5, G2, and G4. Resistance of G3 was also higher than that of G2 and G4. Results showed that the tooth resistance is completely maintained when MOD preparation is restored with composite resin and partially recovered when MOD preparation associated with an endodontic access is restored in the same way. The endodontic treatment and composite resin restoration influenced stress distribution in the dental structure.


CONCLUSIONS
Composite resin restoration plays an important role in recovering tooth strength. With regard to fracture mode, restoration and endodontic treatment increased the incidence of periodontal involvement, which was demonstrated by association with the finite element mechanical test method.
Soares
Paulo Vinícius
PV
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Santos-Filho
Paulo César Freitas
PCF
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Queiroz
Ellyne Cavalcanti
EC
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Araújo
Thiago Caixeta
TC
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Campos
Roberto Elias
RE
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Araújo
Cleudmar Amaral
CA
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
Soares
Carlos José
CJ
Biomechanical Group, Department of Operative Dentistry and Dental Materials, Dental School of Federal University of Uberlandia, Minas Gerais, BrazilLaboratory of Mechanical Projects, Mechanical Engineering School of Federal University of Uberlandia, Minas Gerais, Brazil.
D001641:Bicuspid / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D003188:Composite Resins / Q000737:chemistry*; D019245:Compressive Strength; D003198:Computer Simulation; D003737:Dental Cavity Preparation / Q000379:methods; D003793:Dental Restoration, Permanent / Q000379:methods; D020342:Finite Element Analysis; D006171:Gutta-Percha / Q000627:therapeutic use; D006801:Humans; D008422:Materials Testing; D008437:Maxilla; D008954:Models, Biological; D012387:Root Canal Filling Materials / Q000627:therapeutic use; D012389:Root Canal Obturation / Q000379:methods; D018915:Root Canal Preparation / Q000379:methods; D013314:Stress, Mechanical; D014082:Tooth Fractures / Q000503:physiopathology*; D019553:Tooth, Nonvital / Q000503:physiopathology* / Q000628:therapy
D003188:Composite Resins; C444701:Filtek Z250; D012387:Root Canal Filling Materials; D006171:Gutta-Percha