Influence of the adhesion of integral ceramic veneers, depending on the photopolymerization direction during the luting time

In the case of the adhesive fixations of the fully ceramic veneers, the light-curing diacrylic cement can be contracted towards the light source during its polymerizations. The scope of this work is to observe the differences in veneers adhesion, as well as the difference of all structures (i.e., dental surface, cement, and internal surface of the veneers) depending by the photopolymerization direction. The study is performed in vitro on five extracted teeth and held in formalin 10%. Each tooth is split in two, in the oral-vestibule direction. On each tooth section, a lithium disilicat veneer is fixed. Half of the tooth is photopolymerized during veneer fixing, perpendicular from the veneer direction, and the other half of the same tooth is photopolymerized from the direction of the tooth, by its structure. Using OCT, in both cases, the space between the tooth and the veneer is measured, and the difference of structure in the mass of the cement is followed. Due to the contraction towards the light source, there are significant differences in the structure of the cement mass, its particles being more concentrated in the direction of light-curing. The results are interpreted based on the perfomed OCT analysis. The adhesion of a veneer is better if the photopolymerization is made from the direction of the tooth, through its structure, practically pulling the cement particles, by its contraction towards the dental structure.