Background and Aim: Discoloration of composite restorations over time is among common factors causing their replacement, which weakens the tooth structure and causes pulpal injury. Since tea is a common drink among Iranians, the current study aimed to evaluate the discoloration effect of tea on Kalore and Gradia composite resins.Materials and Methods: This experimental study was performed on 20 disc-shaped specimens of two composites, Kalore and Gradia.  Ten specimens of each composite type with subgroups of 5 were stored in tea and distilled water for 72 Hours. Color measurements were obtained using Spectrophotometer (Minolta, Japan) before and after immersion in solutions. Final spectrophotometry was done after polishing. The results were analyzed using Kruskal-Wallis test.Results: The discoloration value of both composites increased significantly after being immersed in tea (P<0.001). Discoloration in Kalore was higher than Gradia (P<0.014); and amount of discoloration was clinically unacceptable for both composites. (DE>3.3) After final polishing of the samples kept in tea, amount of discoloration decreased for both composites (P<0.001) and (P=0.002) respectively; this reduction was more prominent in Kalore (P=0.008). Nonetheless, discoloration value was yet clinically unacceptable.Conclusion: Immersing the composites in tea caused clinically unacceptable amount of discoloration in both Gradia and Kalore and polishing had more corrective effect on Kalore.

Introduction: In addition to color, translucency is one of the primary factors influencing the esthetics of a dental prosthesis. The aim of this study was to determine the effect of water storage on translucency of reinforced composite resins.Materials and Methods: In this experimental study, six C1-shade dentin samples from Belleglass and Gradia reinforced composite resins were prepared and divided into two groups: The samples in one group were stored in 37oC distilled water and the samples in the other group were kept in a dry environment. The samples in both groups were stored at 37oC in an incubator for one month. Then, sample translucency was calculated using the contrast ratio. Statistical analysis was performed by two-way ANOVA and Mann-Whitney test (a=0.05).Results: No significant differences were observed in contrast ratios between the wet and dry storage conditions of Belleglass samples or Gradia samples (p value=0.827). However, significant differences were observed between contrast ratios of Belleglass and Gradia in wet and dry storage conditions (p value=0.05), revealing that in both dry and wet storage conditions Belleglass was more translucent than Gradia.Conclusion: Within the limitations of this study, both Belleglass and Gradia were stable in translucency after water storage. However, Belleglass was more translucent than Gradia in both dry and wet storage conditions.

Introduction: Considering the ever-increasing importance of dental materials’ esthetics, color, and translucency in cosmetic dentistry, the purpose of this study was to compare the translucency of two reinforced composite resins of BelleGlass and Gradia.Materials and Methods: In this in vitro study three disc specimens, 27 mm in diameter and 1.5 mm in thickness, were fabricated from each material under study. Translucent dentin C2 shades of BelleGlass and Gradia were used. The specimens were produced based on manufacturers’ instructions. Translucencies of BelleGlass and Gradia composite resins were compared using contrast ratio method. A spectrophotometer was used for sending reflected light rays. Data was analyzed by t-test using SPSS software (a=0.05).Results: Mean contrast ratios of BelleGlass and Gradia composite resins were 0.89±0.02 and 0.89±0.01, respectively (p value=0.009).Conclusion: The results of the present study showed that BelleGlass is more translucent than Gradia. Therefore, in patients with natural tooth translucency, BelleGlass is preferable. In patients who use composite resin restorations to camouflage their tooth discolorations Gradia is preferable.

Statement of problem: Surface changes of ceromers caused by tooth brushing are well established, meanwhile they have been improved and are now widely used for various kinds of prosthetics restorations. These materials have lower surface hardness than porcelain and may induce discoloration due to surface roughness. Since it is an important clinical problem, more investigations are needed to evaluate their surface roughness.Purpose: The aim of this study was to evaluate the effect of tooth brushing on abrasive wear and surface roughness of two current used ceromers.Material and method: Ten specimens of each type of the ceromer (Belleglass and Gradia) were prepared. All the specimens were examined and surface roughness (Ra) of each was recorded. Then tooth brushing abrasion test were performed with 500gr weight applied, using a dentifrice containing calcium carbonate as the abrasive material. The surface roughnesses of each specimen after 20000 strokes were determined with Talysurf 1'0. Data were analyzed with two sample T test and non parametric Wilcoxon test.Results: Mechanical toothbrushing decreased the surface roughness of Gradia (p<0.05), but did not have any effect on the surface roughness of Belleglass (p>0.05).Conclusion: The results of this study showed that Belleglass is more resistant to abrasive wear but Gradia is a more polishable ceromer.

Background and Aim: This study assessed cervical microleakage between a Ni-Cr alloy and 3 indirect polymeric veneering materials.Methods & Materials: In this experimental study, twenty one metalic frameworks (copings) were obtained by fabrication 0.5 mm calibrated wax patterns on a master cast abutment. The wax patterns were provided with 0.4 mm beaded retention on the veneering surfaces and cast in a Ni-Cr based alloy used for fixed partial dentures. The Ni-Cr copings were divided equally into 3 groups, 7 samples in each group, and veneered with 3 polymeric materials (Belleglass, Signum, Gradia). Three chemical conditioning systems (metal prep, retention flow, GC metal primer 11) were used with the respective veneering system recommended by the manufacturer; no control group was created.After, 2 weeks of storage in distilled water at 37oC, 2000 cycles at 5-55oC, and 24 hours of storage in 0.5% basic fuchsine, specimens were embedded in clear liquid casting resin and sectioned along a perpendicular cervico-incisal plane through the middle of cervical collar. The surfaces of the resulting sections were examined in the cervical area with a dimensional microscope to detect dye penetration. Scores were compared and analysed with the use of Kruskal-wallis test.Result: Signum was associated with the highest microleakage scores (1.4286 0.5345) and the least micro leakage at the interface was produced by Belleglass (0.4236 0.07868), followed by Gradia (0.8571 0.3779). Only the difference between Belleglass and Signum was significant (P=0.024).Conclusion: Within the limitation of this in vitro study, the extent of cervical microleakge between the coping and veneer depended on the particular polymeric material used for veneering. The extremes of the study were Belleglass and Signum (respectively lowest and highest leakage scores).

Background and Aim: This study aimed to evaluate the effects of bleaching on surface roughness and color of two types of composite resins namely Gradia (hybrid microfilled) and Omnichroma (super-nano filled), subjected to two polishing methods.    Materials and Methods: In this in vitro study, 100 composite specimens (50 Gradia and 50 Omnichroma) were fabricated and divided into two groups for polishing with disc and bur systems. The baseline surface roughness and color parameters (L*, a*, b*) were recorded. The specimens were immersed in a tea solution for 24 days to simulate staining, followed by in-office bleaching with 38% hydrogen peroxide. Surface roughness and color parameters were re-measured post-bleaching. Statistical analysis was performed using repeated-measures ANOVA to assess the effects of bleaching, polishing method, and composite type (alpha=0.05).    Results: The interaction effect of polishing method and composite type on surface roughness was not statistically significant (P>0.05). A significant change was observed in ΔL after polishing compared with the baseline (P = 0.018), indicating an increase in lightness for Omnichroma. For Δa, Gradia composite polished with disc exhibited significant redness after immersion in tea (P=0.022), while Δb results showed that Gradia had a significant shift to yellowness across all stages (P<0.05). Conclusion: The results showed that the surface roughness of both Gradia and Omnichroma composite resins increased after bleaching. Gradia exhibited more pronounced ΔE, particularly turning redder after immersion in tea, whereas Omnichroma displayed better color stability. These findings suggest that material selection and polishing methods are critical in maintaining esthetic outcomes in bleached composite restorations.

Background: One of the advantages of resin composites as a restorative material is their repairability. The purpose of the current study was to compare the repair bond strength of conventional and bulk-fill composites with different bonding systems. Methods: In this in vitro study, sixty cylindrical specimens of materials were prepared according to the six groups under study (two types of conventional Gradia Direct and N-Ceram Bulk-Fill Tetric composites and three bonding systems: Single Bond Universal and Clearfil SE Bond and Single Bond 2). The samples were divided into 6 groups of 10 Single Bond/Gradia Direct composite (G1), Single Bond/Tetric N-Ceram bulk-fill composite (G2), Clearfil SE bond/Gradia Direct (G3), Clearfil SE Bond/Tetric N-Ceram bulk-fill composite (G4), single bond universal/Gradia Direct composite (G5), and Single Bond Universal/Tetric N-Ceram bulk-fill composite (G6). Repair bond strength in each group was measured using the Universal Testing Machine (Hounsfield). All data were analyzed by SPSS 21 using ANOVA, Student’s t-test, and chi-square statistical tests (P<0.05). Results: The highest and lowest bond strength (15.81±2.44 and 14.02±1.57, respectively) belonged to the Clearfil SE Bond-Tetric N-Ceram and Single Bond (Etch & Rinse)-Gradia Direct groups, respectively. The ANOVA test results demonstrated no significant difference in the bonding strengths of the study groups (P=0.537). Conclusions: Bulk-fill composite Tetric N-Ceram, apart from the bonding system, had higher repair bond strength compared to the conventional Gradia Direct composite. It seems that self-etch bonding systems (Clearfil SE Bond and Single Bond Universal) have had more bond strength than etch and rinse bonding (Single Bond 2 bonds).

Statement of Problem: Postcuring techniques improve mechanical properties of indirect composites significantly. Eventhought this technique has been suggested for direct composites, but its effect for direct composites is still questionable.Purpose: This study was undertaken to evaluate the effect of various postcuring techniques on surface hardness of two different types of composites.Materials and Method: Eighty circular specimens of Nulite F (40 specimens) and Gradia (40 specimens) composites were made and light cured. Ten of each type was kept as control group and 10 of each type was postcured with oven for 5 minutes at 120°C. The other ten ones was postcured with microwave for 5 minutes and the last 10 ones were postcured with labolite for 5 minutes. The specimens were polished and were kept in 37°C water for one week. Then surface hardness testing was performed and data were analyzed using one-way ANOVA and Kruskal wallis tests.Results: The results revealed that the surface hardness (VHN) of Nulite F composite in control group was greater than Gradia composite in control group (p<0.05). All postcuring techniques increased the VHN of all groups significantly. The effects of postcuring on increasing surface hardness of Nulite F were more significant in all techniques, especially by the usage of labolite set in Nulite F composite in comparison with Gradia composite.There was no statistically significant difference between surface hardness of microwave and oven groups in Nulite F composite. No statistically significant difference was noticed between surface hardness of microwave and labolite groups in Gradia composite. The effect of postcuring with oven on surface hardness of Gradia composite was statistically significant compared to the two other techniques.Conclusion: By evaluation of various samples in this study it was concluded that all postcuring techniques (labolite, microwave and oven) increased the surface hardness (VHN) of both direct composites (Gradia and Neulife F) significantly.

Statement of Problem: After 30 years of intermittent reports in the literature, the use of fiber-reinforcement is just now experiencing rapid expansion in dentistry.However, there are some controversy reports in the amounts of flexural strength of fiber reinforced composites to use them as bridges.Purpose: The purpose of this study was to evaluate the flexural strength of three commercially available fiber-reinforced composites including Belle Glass, GC Gradia, and Signum.Materials and Method: Thirty uniform bars of 25×2×2 mm (10 for each group) were fabricated as their manufacturers recommended. Then all specimens were loaded to failure using a three-point bending test and flexural strength was determined.Results: The mean flexural strength of Belle Glass (386.65 MPa) was significantly (p<0.0001) higher than that of GC Gradia (219.25 MPa) and Signum (172.89 MPa). There was no significant difference between GC Gradia and Signum in flexural strength.Conclusion: On the basis of these findings, Belle Glass can be used in clinical practice with greater confidence compared to GC Gradia and Signum.