Microleakage of Lithium Disilicate Veneers Bonded to Different Substrates with Light-cure and Dual-cure Resin Cements.

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.

Effect of light-, chemical-, and dual-cured universal adhesives on the internal adaptation of resin composites to pulpal and gingival internal walls.

PURPOSE: To compare the internal adaptation of restorative systems bonded to mid-coronal and gingival dentin using light-cured, chemical-cured, and dual-cured adhesives, both immediately and after aging. METHODS: 60 molars were selected and received occluso-mesial preparations with dentin gingival margins. Restorations were performed using different restorative systems with light-cured, chemical-cured, and dual-cured adhesives. Internal adaptation was assessed by examining the percentage of continuous margin (%CM) at the pulpal and gingival dentin under a scanning electron microscope at x200 magnification. Half of the teeth were stored in sterile water for 24 hours, while the other half underwent 10,000 thermal cycles. Micro-morphological analysis was conducted on representative samples at x1,000 magnification. RESULTS: The restorative system with light-cured adhesive exhibited significantly lower %CM values at the gingival dentin, particularly after aging. Aging had a negative impact on the %CM values of the pulpal and gingival dentin in restorative systems with light-cured and dual-cured adhesives. Regional dentin variations influenced the %CM values, especially after aging, regardless of the restorative system used. The tested restorative system with chemical-cured adhesive is preferable for achieving improved internal adaptation when bonding to both mid-coronal and gingival dentin, compared to the other tested systems. CLINICAL SIGNIFICANCE: The study highlights the variations in adhesive performance between different regional dentin areas using the tested restorative systems.

Two-year clinical performance of dual- and light-cure bulk-fill resin composites in Class ӀӀ restorations: a randomized clinical trial.

OBJECTIVE: This study aimed to compare the clinical performance of dual- and light-cure bulk-fill resin composites (BFRCs) in Class ӀӀ restorations after 2 years. MATERIALS AND METHODS: A double-blinded, prospective, randomized clinical trial (RCT) was conducted following the CONSORT (Consolidated Standard of Reporting Trials) guidelines. Forty patients were enrolled in the study. Each patient received three compound Class ӀӀ restorations. One dual-cure (Fill-Up; Coltene Waledent AG) and two light-cure (QuiXfil; Dentsply, and Tetric N-Ceram Bulk Fill; Ivoclar Vivadent) BFRCs were used for 120 Class ӀӀ restorations. A universal adhesive (ONE COAT 7 UNIVERSAL; Coltene Waledent AG) was used with all restorations. Restorations were clinically evaluated after 1 week (baseline), 6 months, 12 months, 18 months, and finally after 24 months using the FDI World Dental Federation (FDI) criteria. The Kruskal-Wallis test was used for comparison between BFRCs groups at baseline and at each recall period, and the Wilcoxon signed-rank test was used for comparing different follow-up times of each BFRC to baseline. The level of significance was set at p < 0.05. RESULTS: All BFRCs restorations showed only minor changes and revealed no statistically significant differences between their clinical performance for all evaluated parameters at all recall periods; also, there was no statistically significant difference between all recall periods and baseline for all evaluated parameters. CONCLUSION: The two-year clinical performance of dual-cure BFRC was comparable to light-cure BFRCs in Class ӀӀ restorations. CLINICAL RELEVANCE: Dual- and light-cure BFRCs showed excellent clinical performance in Class ӀӀ restorations after a 2-year clinical follow-up.

Polymerization efficiency of different bulk-fill resin composites cured by monowave and polywave light-curing units: a comparative study.

OBJECTIVES: The objective was to evaluate the polymerization efficiency of different bulk-fill resin-based composites cured by monowave and polywave light-curing units, by assessment of the degree of conversion and Vickers microhardness at different depths. METHOD AND MATERIALS: Two commercially available bulk-fill resin-based composites were used: Filtek One Bulk Fill Restorative (3M ESPE) and Tetric N-Ceram Bulk Fill (Ivoclar Vivadent). The light-curing units utilized were two LED light-curing units: a monowave LED light-curing unit (BlueLEX LD-105, Monitex) and a polywave LED light-curing unit (Twin Wave GT-2000, Monitex). For each test, 20 cylindrical specimens (4 mm diameter, 4 mm thickness) were prepared from each bulk-fill resin-based composite using a split Teflon mold. Ten specimens were light-cured by the monowave light-curing unit and the other ten were light-cured by the polywave light-curing unit according to the manufacturer's recommendations. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) was used to assess the degree of conversion, and a Vickers microhardness tester was used to assess Vickers microhardness. Statistical analysis was performed using three-way ANOVA and Tukey post-hoc tests (P < .05). RESULTS: The degree of conversion and Vickers microhardness in bulk-fill resin-based composites containing only camphorquinone as photoinitiator were similar when cured with either monowave or polywave light-curing units. However, bulk-fill resin-based composites containing a combination of photoinitiators exhibited significantly higher degree of conversion and Vickers microhardness when cured with a polywave light-curing unit. Although all groups showed statistically significant differences between the top and bottom surfaces regarding degree of conversion and Vickers microhardness, all of them showed bottom/top ratios > 80% regarding degree of conversion and Vickers microhardness. CONCLUSION: The polywave light-curing unit enhanced the polymerization efficiency of bulk-fill resin-based composites especially when the latter contained a combination of photoinitiators, but does not prevent the use of a monowave light-curing unit.

Depth of cure of dual- and light-cure bulk-fill resin composites.

PURPOSE: To evaluate the degree of conversion (DC), Vickers microhardness (VMH), and depth of cure of dual-cure and light-cure bulk-fill resin composites (BFRCs). METHODS: One dual-cure (Fill-Up) and two light-cure (QuiXfil and Tetric N-Ceram Bulk Fill) BFRCs were investigated. For each tested BFRC, 11 cylindrical specimens (5 mm diameter, 4 mm height) were prepared, and light cured for 10 seconds (n= 11). DC was obtained by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and VMH was obtained using a VMH tester. The specimens were measured for DC and VMH at top and bottom surfaces. Statistical analysis was performed using two-way ANOVA, Tukey's post-hoc, and Pearson correlation tests (P< 0.05). RESULTS: Fill-Up and Tetric N-Ceram Bulk Fill revealed significantly higher DC and VMH values on the top surfaces than that on the bottom surfaces, whereas QuiXfil revealed no significant difference between top and bottom surfaces for DC and VMH. All tested BFRCs showed bottom/top ratios >80% for both DC and VMH. Each tested BFRC showed a significant positive correlation between DC and VMH. All tested BFRCs had adequate depth of cure, but only QuiXfil had a uniform depth of cure. Both DC and VMH bottom/top ratios were effective for depth of cure evaluation. CLINICAL SIGNIFICANCE: QuiXfil, Tetric N-Ceram Bulk Fill, and Fill-Up BFRCs were well cured up to a 4 mm depth. Although Fill-Up (dual-cure) can be used with its chemical-curing mode, light curing improved DC and VMH values of the top layer. Distinct variance in DC and VMH among the three tested BFRCs may affect their clinical performance.

Influence of various antioxidants on micro-shear bond strength of resin composite to bleached enamel.

OBJECTIVE: Teeth bleaching causes an immediate decrease in resin composite bonding ability. This study aimed to investigate the influence of various antioxidants on resin composite bond strength to bleached enamel. MATERIALS AND METHODS: One hundred and ten human maxillary incisors were used. A negative control (group A) (n = 10) was assigned (no bleaching-no antioxidant). The remaining teeth were divided into two groups (n = 50) according to the bleaching agent used: group B (40% hydrogen peroxide) and group C (35% carbamide peroxide). Both groups were subdivided into five subgroups (n = 10). A positive control subgroup (no antioxidant) and other four subgroups according to the antioxidant solution used (10% sodium ascorbate, 10% grape seed extract, 10% green tea extract, and 5% alpha-lipoic acid). After resin composite building, the micro-shear bond strength test was performed. Fracture analysis was examined using a stereomicroscope. Statistical analysis was performed using a two-way analysis of variance and Tukey's HSD post hoc test. RESULTS: Bond strength significantly decreased after bleaching and there was no significant difference between bleaching agents (P < .0848). Except for alpha-lipoic acid subgroups, the other antioxidants subgroups revealed significantly higher bond strengths than bleached control subgroups (P < .0001). CONCLUSION: All antioxidants used except alpha-lipoic acid were effective in the reversal of compromised bonding after bleaching. CLINICAL SIGNIFICANCE: Immediate bonding procedures after bleaching are requisite when bleaching fails to treat teeth discoloration and the direct composite veneer is considered, also when shades of old composite restorations become mismatched after bleaching and should be replaced. Immediate reestablishment of resin bond strengths after bleaching can be achieved by using several antioxidants without the need for delay.