The deformation and strength of a dental ceramic following resin-cement coating.
OBJECTIVE
The hypothesis tested was that processing, pre-cementation and cementation techniques can modify the profilometrically measured deformation of a ceramic.


METHODS
Three-point flexural moduli of a resin-cement were characterised following light irradiation at 430 and 180 mW cm⁻². Thirty IPS e.max Ceram discs were prepared and a reference surface produced by polishing. Discs were annealed, alumina particle air abraded and resin-coated. Profilometric evaluation was performed following each pre-cementation or cementation operative technique using a contact diamond stylus profilometer. Bi-axial flexure strength of the resin-coated discs, light irradiated at 430 and 180 mW cm⁻² (Groups A and B), and the un-coated discs (Group C) was determined. Data were analysed by a one-way analysis of variance with post hoc Tukey tests (P<0.05), or repeat measure analyses when appropriate.


RESULTS
Annealing (at 510°C for 40 min) resulted in a significant reduction (P<0.001) in the characterised mean deflection, as did alumina particle air-abrasion (P<0.001). Resin-cement coating significantly increased the mean deflection for Groups A and B (P<0.001) specimens against the uncoated state. Furthermore no significant impact of increasing time or irradiation intensity on the mean deflection was identified. The mean bi-axial flexure strength was significantly increased (P<0.001) after resin-coating (Groups A and B) when compared with Group C specimens although no difference between Groups A and B specimens (P=0.291) was identified.


CONCLUSIONS
The results of the profilometric technique in combination with the strength supported a strengthening mechanism sensitive to shrinkage stress generation associated with the polymerisation of resin-cements.
Materials Science Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, Trinity College Dublin, Lincoln Place, Dublin 2, Ireland. g_isgro@tiscali.it
G
G
Isgró
O
O
Addison
G J P
GJ
Fleming
D000465:Algorithms; D000537:Aluminum Oxide / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods; D045662:Dental Etching / Q000379:methods; D003775:Dental Polishing; D003776:Dental Porcelain / Q000737:chemistry*; D055119:Elastic Modulus; D006358:Hot Temperature; D006801:Humans; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D018583:Pliability; D058105:Polymerization; D011829:Radiation Dosage; D019279:Resin Cements / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors
D000538:Aluminum Silicates; C075815:IPS-Empress ceramic; C528569:Rely-X; D019279:Resin Cements; D003776:Dental Porcelain; D000537:Aluminum Oxide