RESUMEN
Background: This study aimed to evaluate the microleakage of lithium disilicate veneers with finish lines placed cervically in different substrates (enamel, dentin, and resin composite) and bonded with light-cure (LC) and amine-free dual-cure (DC) resin cements. Material and Methods: Forty-eight human maxillary central incisors were randomly assigned into three groups according to finish line substrate (n=16/group). Each group was subdivided randomly into two subgroups (n=8/subgroup) according to resin cement type: LC resin cement (Variolink Esthetic LC, Ivoclar Vivadent) and DC resin cement (Variolink Esthetic DC, Ivoclar Vivadent). All the specimens received lithium disilicate veneers (IPS e.max Press, Ivoclar Vivadent). After 5000 cycles of thermocycling, the microleakage was measured using the dye penetrating technique. Data were analyzed statistically using Scheirer Ray Hare test, Kruskal-Wallis H-test, and Mann-Whitney U-test. The level of significance was set at p ≤ .05. Results: There was a statistically significant difference between different substrates in microleakage (p=.001), but there was no statistically significant difference between resin cements (p=.907), and there was no interaction between substrates and resin cements (p=.983). Microleakage was lesser when the finish line was placed at enamel and resin composite than at dentin. Similar leakage scores were observed with LC and DC resin cements. Conclusions: The finish line of ceramic veneer is suggested to be placed in enamel or good-quality resin composite restoration. Regarding microleakage and durability, LC and amine-free DC resin cements are suggested for ceramic veneer cementation. Key words:Different substrates, Dual-cure resin cement, Light-cure resin cement, Lithium disilicate veneers, Microleakage.
RESUMEN
Objectives: This study aimed to investigate the elemental analysis and microhardness of a bioactive material (Activa) and marginal tooth structure after storage in different media. Materials and Methods: Fifteen teeth received cervical restorations with occlusal enamel and gingival dentin margins using the tested material bonded with a universal adhesive, 5 of them on the 4 axial surfaces and the other 10 on only the 2 proximal surfaces. The first 5 teeth were sectioned into 4 restorations each, then stored in 4 different media; deionized water, Dulbecco's phosphate buffered saline (DPBS), Tris buffer, and saliva. The storage period for deionized water was 24 hours while it was 3 months for the other media. Each part was analyzed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis for different substrates/distances and the wt% of calcium, phosphorus, silica, and fluoride were calculated. The other 10 teeth were sectioned across the restoration, stored in either Tris buffer or saliva for 24 hours or 3 months, and were evaluated for microhardness of different substrates/areas. Data were analyzed using analysis of variance and Tukey's post hoc test. Results: Enamel and dentin interfaces in the DPBS group exhibited a significant increase in calcium and phosphorus wt%. Both silica and fluoride significantly increased in tooth structure up to a distance of 75 µm in the 3-month-media groups than the immediate group. Storage media did not affect the microhardness values. Conclusions: SEM-EDS analysis suggests an ion movement between Activa and tooth structure through a universal adhesive while stored in DPBS.
RESUMEN
AIM: The present study aimed to evaluate the retention strength of nonretentive zirconia occlusal veneers bonded to different bonding surfaces (enamel, enamel and dentin, and enamel with composite filling) using two adhesive resin cement systems that use either organophosphate carboxylic acid or organophosphate monomers as a ceramic primer. MATERIALS AND METHODS: Sixty extracted mandibular molars were prepared to receive occlusal veneers as follows (n = 20): 1-mm reduction within enamel; 2-mm reduction within enamel and dentin; 1-mm reduction within enamel with composite filling. Each occlusal veneer was designed with an occlusal bar to aid in the retention test, then milled from a zirconia block, and sintered. Within each group, the zirconia occlusal veneers were bonded using either Duo-Link Universal or Panavia V5 (10 specimens each). All specimens were thermocycled for 5000 cycles. After the pull-off test, the retention strength was calculated for each specimen. Each specimen was examined under magnification to determine its mode of failure. Representative specimens were examined using a scanning electron microscope. Data were analyzed using the two-way analysis of variance (ANOVA) and Tukey HSD tests (P = 0.05). RESULTS: Both bonding substrate and cement type had a significant influence on retention strength values (P < 0.05). The two-way ANOVA showed a significant interaction between bonding substrate and cement type (P = 0.003). There were significant differences in the retention strength between the cements in both the enamel and enamel and dentin substrates (P < 0.05), but no significant difference between the cements in the enamel with composite filling substrate (P > 0.05). The predominant mode of failure was cement remaining principally in the restoration surface (adhesive failure), followed by cement adhesion to both the tooth and the restoration surface (mixed failure). CONCLUSIONS: Among the studied substrates, enamel was the optimal dental bonding surface. However, bonding to dentin was not a limiting factor for the retention of zirconia occlusal veneers. The resin cement using an organophosphate (Panavia V5) provided superior retention strength compared with the cement using organophosphate carboxylic acid monomer (Duo-Link Universal).
