title: Partial ceramic crowns: influence of ceramic thickness, preparation design and luting material on fracture resistance and marginal integrity in vitro.
abstract: This in vitro study tested the effects of two different ceramic thicknesses, two preparation designs and two different luting agents on the marginal integrity and fracture resistance of partial ceramic crowns (PCC). Eighty extracted human molars were prepared according to the following preparation designs: a) Coverage of functional cusps/butt joint (n=40), b) Horizontal reduction of functional cusps (n=40). PCC (Vita Mark II, Cerec3 System) were fabricated and the ceramic thickness of the functional cusps was adjusted to (1): 0.5-1.0 mm and (2): 1.5-2.0 mm. PCC were adhesively luted to the cavities with either Excite/VariolinkII (VL) or RelyX Unicem (RX). The specimens were exposed to thermocycling and central mechanical loading (5000 x 5 degrees C-55 degrees C; 30 second/cycle; 50,0000 x 72.5N, 1.6Hz). Marginal integrity was assessed by evaluating dye penetration (fuchsine) on multiple sections in the bucco-oral direction by relating the actual penetration distance to the maximal length of the corresponding cavity wall (100%). Restoration/luting agent (RL)--and tooth/luting agent (TL) interfaces were evaluated separately. The data were statistically analyzed with the Mann Whitney U-test and the Error Rates Method (ERM), and the fracture rates were analyzed with the chi2-test. Dye penetration data indicated that ceramic thickness and luting agent had a statistically significant influence upon marginal integrity in general, irrespective of all other parameters (ERM): RX showed significantly lower microleakage along the RL interface than VL. VL revealed significantly lower microleakage at the TL interface than RX. Fifteen PCC of group 1 (0.5-1.0 mm) and two PCC of group 2 (1.5-2.0 mm) were fractured after thermocycling and central mechanical loading, with the difference being statistically significant. PCC fabricated from industrially sintered feldspathic ceramic should have at least a thickness of 1.5-2.0 mm in stress-bearing areas.
authors.affiliation: University of Regensburg, Dental School, Department of Operative Dentistry and Periodontology, Regensburg, Germany.
authors.forename: Marianne
authors.initials: M
authors.lastname: Federlin
authors.forename: Stephanie
authors.initials: S
authors.lastname: Krifka
authors.forename: Maximilian
authors.initials: M
authors.lastname: Herpich
authors.forename: Karl-Anton
authors.initials: KA
authors.lastname: Hiller
authors.forename: Gottfried
authors.initials: G
authors.lastname: Schmalz
mesh_terms: D003442:Crowns; D003737:Dental Cavity Preparation; D003763:Dental Leakage / Q000517:prevention & control; D018772:Dental Marginal Adaptation; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D008963:Molar; D019279:Resin Cements; D018709:Statistics, Nonparametric
chemical_list: C483701:Rely X Unicem; D019279:Resin Cements; D003776:Dental Porcelain; C103502:Variolink