Evaluation of the Sealing Ability of Direct versus Direct-Indirect Veneer Techniques: An In Vitro Study

Backgrounds. Marginal discoloration, microleakage, wear, and marginal fractures are all prevalent problems with composite veneers, and this scenario leads the esthetic outcome to deteriorate with time, resulting in patient discontent. Aim of the Study. The study’s goal was to determine the marginal sealing ability of composite laminate veneers when employing two types of veneer techniques: direct and direct-indirect veneers, as well as two types of composite resin: nanohybrid and microfilled composite resin restorations, using dye penetration method. Materials and Methods. In this study, forty extracted human teeth were utilized. Following a standardized veneer preparation on the labial surface of the teeth, they were separated into two groups of 20 teeth each, using the following composite application techniques: group A: direct veneers and group B: direct-indirect veneers. Following that, each major group was separated into two subgroups of ten teeth each, based on the type of composite employed: subgroup 1 used nanohybrid composite resin, while subgroup 2 used microfilled composite resin. All of the samples were kept in distilled water, thermocycled, and soaked in 2% basic fuchsine dye. These specimens were sectioned and examined under a stereomicroscope for dye penetration at the gingival margin. The data was analyzed using independent T -tests using SPSS 22. Result. Using direct-indirect veneer technique with nanohybrid composite resin material resulted in the most negligible dye penetration at the gingival margin, while using direct veneer technique with microfilled composite resin material resulted in the maximum dye penetration. For both composite materials, gingival microleakage was lower when using the direct-indirect veneer technique than when using the direct technique, and the difference was statistically significant ( P < 0.05 ). In both techniques, gingival microleakage was lower with nanohybrid composite than with microfilled composite, and the difference was statistically highly significant ( P = 0.001 ). Conclusion. The sealing ability of the gingival margin of tooth/composite interface is better when applying direct-indirect veneer technique with nanohybrid composite resin than that of direct veneer technique with microfilled composite resin material.

Depth-Related Curing Potential of Ormocer- and Dimethacrylate-Based Bulk-Fill Composites

The aim of this in vitro study was to investigate the degree of C=C double bond conversion of high-viscosity dimethacrylate- or ormocer-based bulk-fill composites as a function of measurement depth. Four bulk-fill composites (Tetric EvoCeram Bulk Fill, x-tra fil, SonicFill, and Bulk Ormocer) and the conventional nanohybrid composite Tetric EvoCeram were applied in standardized Class II cavities (n = 6 per group) and photoactivated for 20 s at 1350 mW/cm2. The degree of conversion of the composites was assessed using Fourier-transform infrared spectroscopy at seven measurement depths (0.15, 1, 2, 3, 4, 5, 6 mm). Data were analyzed using repeated measures ANOVA and one-way ANOVA with Bonferroni post-hoc tests (α = 0.05). The investigated bulk-fill composites showed at least 80% of their maximum degree of conversion (80% DCmax) up to a measuring depth of at least 4 mm. Tetric EvoCeram Bulk Fill and Bulk Ormocer achieved more than 80% DCmax up to a measuring depth of 5 mm, x-tra fil up to 6 mm. The conventional nanohybrid composite Tetric EvoCeram achieved more than 80% DCmax up to 3 mm. In contrast to the conventional composite, the investigated ormocer- and dimethacrylate-based bulk-fill composites can be photo-polymerized in thick layers of up to at least 4 mm with regard to their degree of C=C double bond conversion.

Effect of reinforcements on graphite/titania/aluminium nanohybrid composites

Aluminium alloys and their composites are often used in aerospace, automobile and biomedical applications. However, mechanical and surface properties of those alloys have not reached up to the expectation. This investigation focused to improve the wear resistance properties along with mechanical and surface properties of aluminium matrix composites. Here, novel aluminium matrix nanohybrid composites were developed using titanium oxide and graphite as reinforced via powder metallurgical route. The sintered samples were analysed by different tests such as, hardness, surface roughness, wear tests and other structural analyses. The obtained results showed that some new compounds formed during sintering were responsible for improved mechanical and surface properties for different applications. The wear test showed that there was rapid worn out of graphite from the composites having aluminium content more than 50 wt% due to the higher content of graphite (10 and 20 wt%, respectively). In addition, due to the increase of porosity in the different hybrid composites, there was an increase in coefficient of friction observed in some materials. The aluminium nanohybrid composite having 40 wt% titania and 10 wt% graphite showed best results compared with others. Therefore, the optimized hybrid composites with proper sintering condition would significantly help to get suitable structural, mechanical as well as tribological properties for many advanced applications.

Effect of brushing on colour stability of nanohybrid composite after immersion in brewed beverages – an in vitro study

Background and aims. In today’s world, everyone is mindful of one’s appearance and appreciates aesthetics. Of the various restorative materials available, composites are considered as the most aesthetic with good color stability. This study aims at finding the effect of brushing on the color stability of nanohybrid composite after being immersed in various beverages. Methods. Thirty disk specimens were prepared for each staining solution (N=30), with a total of 90 specimens. The disk specimens for each staining solution were then sub divided into 2 groups (N=15): brushing and non-brushing. After preparation, the specimens were soaked in distilled water for 24 hours in separate containers. Baseline color of the samples was evaluated using spectrophotometer. The samples were then immersed in tea, coffee or water. The groups of samples to be brushed were held in the mold and 20 strokes of brushing using an electronically powered toothbrush were done on each side of the disk sample. The color was re-evaluated after a period of 14 days. Results. When comparing among the three beverages, tea showed the highest ΔE*ab indicating greatest discoloration when compared to coffee and water. This can be graded as tea > coffee > water. However, statistically there was no significant difference between tea and coffee. When compared within tea, coffee, or water specimens the non - brushed specimens showed greater discoloration compared to the brushed specimens both clinically and statistically. Conclusion. When immersing the specimens in the solutions, tea showed more color change compared to coffee, making the specimens clinically unacceptable. However, brushing the specimens reduced the discoloration when compared to non–brushing, making the coffee specimens clinically acceptable.

Stain Susceptibility of 3D-Printed Nanohybrid Composite Restorative Material and the Efficacy of Different Stain Removal Techniques: An In Vitro Study

Recent burgeoning development in material science has introduced a 3D-printable, nanohybrid composite resin restorative material. However, its performance has not yet been investigated. This study evaluates the stain susceptibility and efficacy of different stain removal techniques. A total of 120 labial veneers were fabricated using milling (n = 60) and SLA 3D-printing (n = 60). Based on the immersion media: coffee, tea and artificial saliva, each group was divided into three sub-groups (n = 20). Stain susceptibility was evaluated by calculating color difference (∆E00) at 12 and 24 days using a spectrophotometer against black and white backgrounds. Collected data were analyzed with ANOVA and Tukey’s post hoc test (p < 0.05). A significant interaction effect was found between the staining mediums and fabrication methods in both black and white backgrounds (p < 0.001). 3D-printed restorations showed significantly higher stain susceptibility than milled restorations (p < 0.001). Prolonged immersion time increased the color difference in both groups. In-office bleaching was more effective in stain removal in both 3D-printed and milled restoration groups. The susceptibility of the presented novel 3D-printed restorative material to color changes in different immersion mediums was clinically not-acceptable. The clinicians might expect the need to replace the restoration after 1–2 years and thus, recommendation for the use of such a material as a permanent restoration cannot be made but rather as a long-term temporary restoration.

A Two-Year Comparative Evaluation of Clinical Performance of a Nanohybrid Composite Resin to a Flowable Composite Resin

Objective: This prospective in vivo study aimed to compare the clinical behavior of a flowable composite resin (Genial Universal Flo, GC) and a nanohybrid universal composite resin (Tetric Evo Ceram, Ivoclar Vivadent) used in Class I and II direct esthetic restorations in posterior teeth. Methods: A total of 108 Class I and II direct restorations were performed in patients aged between 20 and 60 years. The originality of this study lies in the fact that both materials were placed in pairs, in the same clinical environment (i.e., the same patient and the same type of tooth). The evaluations were performed now of restoration and after 2-weeks, 6-, 12-, and 24-months intervals using clinical examination, clinical photographs, and radiological examination, according to modified USPHS criteria. Statistical analysis was performed using the Fisher exact test and chi-square analysis. Results: At baseline, the universal composite resin showed better esthetic properties such as surface luster, surface staining marginal staining. Both materials regressed significantly over time with no significant difference between groups. Conclusions: Both flowable and nanohybrid composite resins exhibit acceptable clinical performance. The present 24 months of evaluation of different composites showed that the G-ænial Universal Flo could be an effective esthetic material for posterior restoration. No significant difference between both materials over time concerning surface luster, surface staining, and marginal staining.

Evaluating the masking ability of CAD/CAM hybrid ceramics with different thicknesses

Aim: A discoloration existing under the restoration can affect the final restoration color, and various techniques can be used to address this situation. The aim of this study was to investigate the masking ability of the substructure, color of different hybrid CAD/CAM ceramics in various thicknesses. Methodology: A total of 120 samples were produced from 4 different CAD/CAM hybrid ceramic blocks (Cerec blocs, GC Cerasmart, Vita Enamic, 3M Lava Ultimate) in 1, 1.5 and 2 mm thickness. The samples were sliced with 100 N pressure in a low-speed precision cutting device under water cooling. The specimens were placed over the neutral grey background for initial spectrophotometric measurements. A3 color posterior nanohybrid composite (14 X 7 X 1 mm) was preferred to mimic discoloration in the substructure. The cementation procedure of composite and the CAD/CAM hybrid ceramic complex was standardized under 10 N continuous pressure and was performed using a dual cured resin cement. All samples were incubated at 37 °C for 24 hours in incubator after cementation. And the second spectrophotometeric measurement was done via the L*, a*, and b* color attributes of the complex specimens. Additionally, ΔE* values were calculated to determine the color differences between each group. Kruskal Wallis test was used for statistical analysis and Dunn’s test was used for group comparison. Significance was evaluated at least p <0.05. Results: It was found that thickness of the ceramics increases, the substructure color is better masked and the thickness made a statistically significant difference on the masking ability (p<0.01). For 1 mm thick samples, the highest ΔE* value was found in Cerec blocs with 9.36, while the lowest value was found in GC Cerasmart as 4.27. Conclusion: Within the limitations of this study, it was concluded that the tested CAD/CAM hybrid ceramics showed better masking ability than Cerec blocs. How to cite this article: Ünalan Değirmenci B, Wahid WF. Evaluating the masking ability of CAD/CAM hybrid ceramics with different thicknesses. Int Dent Res 2021;11(2):114-20. https://doi.org/10.5577/intdentres.2021.vol11.no1.9 Linguistic Revision: The English language in this manuscript has been checked by at least two professional editors, both native speakers of English.

Influence of increment thickness on microhardness and bond strength in composite resins

The aim of this study was to evaluate the Knoop microhardness and the microtensile bond strength of a second-generation of bulk-fill (BF) and a nanohybrid composite resins (NH) in different thicknesses of increments. For this, ninety disks of composite resin were made for Knoop microhardness, being divided into six groups (n = 15). The Knoop microhardness obtained in each millimeter of the internal face. For microtensile bond strength, ninety restored in third molars were used, divided into six groups (n = 15). For Knoop microhardness, the Wilcoxon and Friedman test was used. For the microtensile bond strength were used the Two-way Anova test and Tukey's post-test (p <0.05). The NH resin showed higher Knoop micro hardness than BF and it was observed that hardness value decreases as increases the thickness of the resin. There was no significant difference in microtensile bond strength comparing NH and BF. However, there was a significant difference between G2 and G4 for the NH groups, with the highest and lowest bond strength values, respectively. Thus, the new generation of the bulk-fill composite resin provided lower microhardness values as the thickness of the increments increases in comparison with the nanohybrid composite resin. The microtensile bond strength does not appear to have been influenced by the type of resin, or the thickness of the increment.