The influence of cement lute, thermocycling and surface preparation on the strength of a porcelain laminate veneering material.
OBJECTIVE
The purpose of the current study was to examine the impact of thermocycling on the development of surface flaws on the cemented surfaces of PLV restorations prepared by acid-etching or alumina (Al2O3) abrasion.


METHODS
Sets of 30 Vitadur-alpha dentin porcelain discs (15 mm diameter, 0.9 mm thickness) were prepared by either abrading with 50 microm Al2O3 or hydrofluoric (HF) acid-etching. Further specimen series were coated with a resin luting cement prior to thermocycling to simulate the conditions encountered 'in service'. Mean fracture strengths, standard deviations and associated Weibull moduli (m) were determined using bi-axial fracture (ball-on-ring).


RESULTS
The two-way ANOVA revealed significant differences between the mean strength values of the porcelain specimens abraded with 50 microm Al2O3 compared with the higher strength HF acid-etched specimens. Significant differences were also identified in the mean fracture strength data for the abraded cemented and acid-etched cemented groups with the abraded groups recording the highest strength levels.


CONCLUSIONS
Composite resin polymerisation shrinkage may help to strengthen porcelain surfaces by imposing a compressive stress on the porcelain surface. However, the strength of the HF etched cemented groups when bonded to composite resin were weaker than abraded specimens. Etching the porcelain does not only provide the necessary surface roughness conducive to mechanical interlocking but would appear to have a weakening effect on the porcelain surfaces.
Addison
Owen
O
Biomaterials Unit, School of Dentistry, University of Birmingham, St Chads Queensway, Birmingham B4 6NN, UK.
Fleming
Garry J P
GJ
D000537:Aluminum Oxide; D000704:Analysis of Variance; D001840:Dental Bonding; D045662:Dental Etching / Q000379:methods; D003776:Dental Porcelain; D003799:Dental Stress Analysis; D003801:Dental Veneers; D004548:Elasticity; D006358:Hot Temperature; D006858:Hydrofluoric Acid; D008422:Materials Testing; D044367:Phase Transition; D018583:Pliability; D019279:Resin Cements / Q000528:radiation effects; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength
C418025:Compolute; D019279:Resin Cements; D003776:Dental Porcelain; D000537:Aluminum Oxide; D006858:Hydrofluoric Acid