Bilateral treatment: a strategy for enhancing the mechanical strength of machinable veneers.
OBJECTIVE
To investigate the potential application of bilateral treatment of glazing plus staining in machinable veneer mechanical strength improvement.


METHODS
Standard laminate specimens (n=105) were sliced from machinable ceramic blocks and divided into seven batches for further treatments: (1) batch C, standard specimens; (2) batch P, one specimen surface polished; (3) batch F, fired in glaze-firing-program without glaze; (4) batch G, fired with glaze on one surface; (5) batch S, fired with stain on one surface; (6) batch GA, fired with glaze on one surface, then re-fired in stain-firing-program without stain, and (7) batch GS, fired with glaze on one surface then fired with stain on the other side. The flexural strength of all specimens was tested with a three-point-bending test and the results statistically evaluated. Scanning electron microscopy (SEM) was used to analyze fractographs of bilateral treatment specimens. X-ray diffraction (XRD) analysis was performed to evaluate the influence of thermal annealing effect on strength improvement in bilateral treatment.


RESULTS
The flexural strength of bilateral treated GS (143.23+/-14.02 MPa) was significantly higher (P<0.05) than unilateral treated G (125.92+/-14.01 MPa) and P (114.48+/-8.45 MPa) and other batches, including C (100.11+/-6.65 MPa), F (99.48+/-8.61 MPa), S (119.28+/-19.34 MPa) and AG (126.65+/-9.83 MPa). SEM imaging showed that no underlying separation between the glaze-matrix or stain-matrix could be found in the fractured GS specimen. No evidence of Bragg diffraction peak broadening could be seen in XRD spectra compared with specimens from batches C and AG.


CONCLUSIONS
To improve machinable laminate strength, a bilateral treatment comprising staining and glazing gave higher strength than unilateral glazing or polishing alone. It was the surface layer effect achieved by glazing and staining, not the thermal annealing effect achieved during glaze and stain sintering, which contributed to the laminate strength improvement.
Chen
Su
S
Prosthetic Department, Beijing Stomatological Hospital, School of Stomatology, Capital Medical University, Tiantan Xili No. 4, Chongwen District, Beijing, China.
Wei
Yong-jie
YJ
Chen
Ming-ming
MM
Zhang
Zhen-ting
ZT
D017076:Computer-Aided Design; D018360:Crystallography, X-Ray; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D003801:Dental Veneers; D005898:Glass; D006358:Hot Temperature; D016014:Linear Models; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D018583:Pliability; D017797:Prosthesis Coloring; D018709:Statistics, Nonparametric; D013499:Surface Properties
D003776:Dental Porcelain