Effect of different cements on the biomechanical behavior of teeth restored with cast dowel-and-cores-in vitro and FEA analysis.
OBJECTIVE
To test the hypothesis that the type of cement used for fixation of cast dowel-and-cores might influence fracture resistance, fracture mode, and stress distribution of single-rooted teeth restored with this class of metallic dowels.


METHODS
The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu-Al cast dowel-and-cores cemented with one of four options: conventional glass ionomer cement (GI); resin-modified glass ionomer cement (GR); dual-cure resin cement (RC); or zinc-phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135 degrees angle with a 0.5 mm/min crosshead speed. Data were analyzed using one-way analysis of variance (ANOVA) and the Fisher test. Two-dimensional finite element analysis (2D-FEA) was then performed with representative models of each group simulating a 100 microm cement layer. Results were analyzed based on von Mises stress distribution criteria.


RESULTS
The mean fracture resistance values were (in N): RC, 838.2 +/- 135.9; GI, 772.4 +/- 169.8; GR, 613.4 +/- 157.5; ZP, 643.6 +/- 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values.


CONCLUSIONS
The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel-and-cores.
Soares
Carlos José
CJ
Biomechanics Group, Department of Operative Dentistry and Biomaterials, School of Dentistry-Federal University of Uberlandia, Uberlândia, Minas Gerais 38400-902, Brazil. carlosjsoares@umuarama.ufu.br
Raposo
Luís Henrique Araújo
LH
Soares
Paulo Vinícius
PV
Santos-Filho
Paulo César Freitas
PC
Menezes
Murilo Sousa
MS
Soares
Priscilla Barbosa Ferreira
PB
Magalhães
Denildo
D
D000535:Aluminum; D000818:Animals; D002417:Cattle; D002484:Cementation / Q000379:methods*; D003300:Copper; D003722:Dental Alloys; D003735:Dental Casting Technique; D003799:Dental Stress Analysis / Q000379:methods; D055119:Elastic Modulus; D020342:Finite Element Analysis; D005899:Glass Ionomer Cements; D011176:Post and Core Technique; D011897:Random Allocation; D019279:Resin Cements; D014082:Tooth Fractures / Q000517:prevention & control; D015036:Zinc Phosphate Cement
D003722:Dental Alloys; D005899:Glass Ionomer Cements; D019279:Resin Cements; D015036:Zinc Phosphate Cement; D003300:Copper; D000535:Aluminum