Effect of composite basing on the resistance to bulk fracture of industrial porcelain inlays.
OBJECTIVE
Bases are used in restorative dentistry for several reasons (i.e. isolation, elimination of undercuts, etc). Glass ionomers are the standard materials used as bases for porcelain inlays, despite the disadvantages of their mechanical properties. An alternative basing material is composite: a generous layer of posterior composite is cured and shaped in the cavity before an impression is taken. The composite basing technique has several clinical advantages. The aim of this study was to investigate the effect of the thickness of a composite base on the bulk fracture resistance of industrial porcelain, and to describe the procedure.


METHODS
Fifteen porcelain (P) and 15 composite (C) bars, 1-, 2-, and 3-mm thick were joined to form 15 C/P bars, all 4-mm thick. Three groups were created: C 1 mm/P 3 mm (group 1), C 2 mm/P 2 mm (group 2), and C 3 mm/P 1 mm (group 3). The pairs were joined using Twinlook cement, subjected to a three-point bending test and loaded to fracture. The beam theory was used to support and explain the results.


RESULTS
The fracture load means were: group 1, 197.7 +/- 18.7 N; group 2, 234.3 +/- 63.3 N, group 3, 336.3 +/- 31.3 N. Group 3 was significantly stronger than group 1 (P = 0.01) and group 2 (P = 0.03). Groups 1 and 2 were not statistically different.


CONCLUSIONS
Composite basing is a tissue conserving method which may significantly increase the resistance to bulk fracture of adhesive porcelain inlays.
Moscovich
H
H
Department of Oral Function and Prosthetic Dentistry, University of Nijmegen Dental School, The Netherlands. H.moscovich@dent.KUN.NL
Roeters
F J
FJ
Verdonschot
N
N
de Kanter
R J
RJ
Creugers
N H
NH
D000134:Acid Etching, Dental; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003723:Dental Amalgam; D001840:Dental Bonding; D003736:Dental Cavity Lining; D003738:Dental Cements / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D005899:Glass Ionomer Cements / Q000737:chemistry; D006801:Humans; D006858:Hydrofluoric Acid; D007284:Inlays; D008422:Materials Testing; D018583:Pliability; D013314:Stress, Mechanical
C076805:Clearfil Porcelain Bond; D003188:Composite Resins; D003738:Dental Cements; D005899:Glass Ionomer Cements; C086630:TwinLook cement; D003776:Dental Porcelain; C084849:Clearfil Ray Posterior; D017438:Bisphenol A-Glycidyl Methacrylate; D003723:Dental Amalgam; D006858:Hydrofluoric Acid