Predictions of cement microfracture under crowns using 3D-FEA.
OBJECTIVE
The objective of this research study was to test the effects of (1) crown margin type, (2) cement type, (3) cement thickness, (4) loading direction, and (5) loading magnitude on stress levels and distributions within luting cement that might lead to cement microfracture using three-dimensional Finite Element Analysis techniques.


METHODS
Thirty-two three-dimensional computer models, as well as models for standards, were generated for a mandibular first premolar. Crown preparations exhibited shoulder or chamfer margin configurations, and zinc phosphate, zinc polycarboxylate, glass ionomer, and resin cements were used in thicknesses of 25 or 100 microm. Modeled crowns were loaded axially or obliquely at 10 and 100 MPa. Areas and levels of stress concentrations within the cement were determined.


RESULTS
Stresses in the cement were low for all situations except 100 MPa oblique stressing. Stresses at the margins of crowns with chamfer marginal configuration were higher than those with shoulder margins. Stresses under oblique stressing were 10 to 150 times higher than under axial stressing. Except for Zn phosphate cement, cement thickness minimally affected stress levels and distributions. Greater stresses were found in cements with the greater Young's modulus.


CONCLUSIONS
Although the chamfer margin design could lead to greater stresses near the margins that places the cement at risk for microfracture and possible crown failure, glass-ionomer and composite resin cements have more favorable mechanical properties for resisting microfracture.
Kamposiora
P
P
School of Dentistry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA. geopho@hol.gr
Papavasiliou
G
G
Bayne
S C
SC
Felton
D A
DA
D001641:Bicuspid; D002516:Ceramics / Q000737:chemistry; D003198:Computer Simulation; D003442:Crowns; D003738:Dental Cements / Q000737:chemistry* / Q000145:classification; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D004548:Elasticity; D020342:Finite Element Analysis; D005544:Forecasting; D005899:Glass Ionomer Cements / Q000737:chemistry; D006047:Gold Alloys / Q000737:chemistry; D006801:Humans; D008334:Mandible; D008422:Materials Testing; D008956:Models, Chemical; D011076:Polycarboxylate Cement / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D012307:Risk Factors; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D015036:Zinc Phosphate Cement / Q000737:chemistry
D003738:Dental Cements; D005899:Glass Ionomer Cements; D006047:Gold Alloys; D011076:Polycarboxylate Cement; D019279:Resin Cements; D003776:Dental Porcelain; D015036:Zinc Phosphate Cement