Evaluation of color stability of sectional laminate veneers after aging procedures

With the advances of dental technology and growing perception of dental esthetics; today it's possible to perform natural looking and minimally invasive restorations. Laminate veneer restorations which are developed for this purpose can eliminate the removal of additional sound enamel and dentine. However; full coverage laminate veneers can be considered invasive if there is a possibilty of applying sectional veneers in case of a small defect or diastema presence. But the long term clinical success of anterior sectional restorations have some question marks. The aim of this in vitro study was to evaluate the color stability of sectional laminate veneers fabricated with 4 different materials and cemented with 2 different adhesive resin cements. Lithium disilicate glass-ceramic (IPS e.max CAD Impulse Opal, Ivoclar Vivadent), resin nano ceramic (Lava™ Ultimate, 3M ESPE), feldspathic ceramic (CEREC Blocs, Sirona) and leucite containing feldspathic ceramic (IPS InLine Dentin, Ivoclar Vivadent) prepared on refractory investment were chosen for veneer materials. Light cure resin cement (Variolink Veneer, Ivoclar Vivadent) and dual cure resin cement (Variolink N, Ivoclar Vivadent) were chosen for cementation. Bovine teeth that are similar to human teeth were used for cementation surface. All restorations were prepared with the thickness of 0,2-0,4 mm and final polishing procedures were handled after cementation as to achieve perfect finishing line between teeth and the restorations. All speciments were subjected to 5000 cycles of thermal cycling in distilled water at 5°C and 55°C prior to immersion in coffee solution. Color differences were measured by a spectrophotometer after each process and ∆E values were calculated. Also visual observation and scorings were carried out to determine the marginal discoloration of the restorations. ∆E values and observer scores were statistically analysed to determine the discoloration degree and compare the groups. Statistical analyses were carried out with Oneway ANOVA , T-test and as post ANOVA test Dunnett T3 was used. Observer scores were evaluated using Mann-Whitney U test. Besides, scanning electron microscopy (SEM) was used for examination of the restorations' finishing lines. The results revealed that coffe immersion after thermal aging procedures led to colour changes that were statistically significant in all the evaluated material-cement combinations (p≤0,05). But feldspathic veneers cemented with light cure resin cement (2,67 ±1,475) can be considered clinically acceptable (∆E<3,3). Amongst all veneer materials, Lava™ Ultimate group showed the lowest color stability (13,77±0,719). Also observer scorings showed the same results that marginal discoloration was higher in Lava™ Ultimate group while no marginal discoloration was observed in IPS InLine group. Dual cure or light cure resin cements showed no statistically significant differences in color stability (p>0,05). According to the results of this in-vitro study, feldspathic ceramics prepared on refractory investment show clinically acceptable discoloration results compared to other groups. Considerable discoloration results were observed in resin nano ceramic veneer groups.