Objective: This study investigated the effect of different sintering temperatures and times on the flexural strength and grain size of zirconia. Material and methods: Zirconia specimens (In-Coris ZI, In-Coris TZI, 120 samples) were prepared in a partially sintered state. Subsequently, the specimens were randomly divided into three groups and sintered at different final sintering temperatures and for various durations: 1510 °C for 120 min, 1540 °C for 25 min and 1580 °C for 10 min. Three-point flexural strength (for 120 samples, 20 samples per group) was measured according to the ISO 6872: 2008 standards. The grain sizes were imaged by scanning electron microscopy (SEM) and the phase transitions were determined by X-ray diffraction (XRD). The data were analyzed using one-way ANOVA and Duncan tests (p < 0.05). Results: The highest flexural strength was observed in ZI and TZI samples sintered at 1580 °C for 10 min. The differences between the ZI samples sintered at 1510 °C for 120 min and those sintered at 1540 °C for 25 min were statistically insignificant. Also, TZI samples sintered at 1510 °C for 120 min and those sintered at 1540 °C for 25 min also did not show any statistically significant differences. There were no visible differences in the grain sizes between the ZI and TZI specimens. The XRD patterns indicated similar crystalline structure for both materials subjected to the three different procedures. Conclusions: The results of this study showed that experimented high sintering temperature and short sintering time combination increases the flexural strength of zirconia.

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Aim: This study aimed to evaluate the oxide layer, surface roughness, and bond strength with porcelain of cobalt-chromium (Co-Cr) and titanium (Ti) substructures produced using casting, milling and selective laser sintering techniques. Methodology: A total of 180 disc-shaped metal samples with a diameter of 1 cm and a thickness of 3 mm were produced. The samples were divided into six groups (n=15) according to the technique used to produce the metal substructures—casting, milling, and SLS—and the chemical composition of the metal substructure—Co-Cr and Ti. Then roughness averages (Ra) of the sample surfaced were calculated with a contact-type profilometer. Nondestructive energy-dispersive X-ray was performed to ensure that the layer displayed in contrast was the oxide layer, and the average oxide layer thickness was calculated from scanning electron microscope images. Metal-porcelain complexes were subjected to shear bond strength test and failure types were noted. Two-way multivariate analysis of variance (MANOVA) was used to compare oxide layer thickness, surface roughness, and shear bond strength according to the metal and production technique, and Tukey’s honestly significant difference (HSD) test was used for multiple comparisons of the main effects. Results: Two-way MANOVA revealed that the metal and technique used in the substructure production had significant effects on surface roughness, oxide layer thickness and shear bond strength (p < 0.001). Ti groups exhibited thicker oxide layer formation than Co-Cr groups. Low surface roughness values were observed in the milling groups. The highest shear bond strength value (53.8 MPa) was observed in the Co-Cr group produced by casting, while the lowest value (32.2 MPa) was obtained in the Ti group produced by casting. Conclusion: It should be kept in mind that there is no ideal production technique and that the effects of the production technique differ depending on the metal used.   How to cite this article: Ünalan Değirmenci B, Ersoy NM. The effects of current production techniques on the surface roughness, oxide layer thickness and porcelain bond strength of cobalt-chromium and titanium substructures. Int Dent Res 2021;11(3):129-39. https://doi.org/10.5577/intdentres.2021.vol11.no3.1   Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Objective: Vital bleaching is popular treatment option for discolored teeth. But at post-treatment stage, loss of adhesion is highly reported. Literature focused on antioxidant application for the answer of this issue. The aim of this study is comparing effects of six different antioxidants on color stability of bleached teeth. Material and Methods: This study includes total of 84 extracted intact non-carious lower incisors. 35% hydrogen peroxide was applied on the labial surfaces of specimens in accordance with manufacturer's instructions. The bleached teeth were divided into 7 groups. No antioxidants were applied to the control group. For the experimental groups, the following antioxidants were applied for 10 minutes each: 5% proanthocyanidin, 5% sodium ascorbate, 5% lycopene, %5 green tea, %5 white tea and %5 ?-tocopherol. CIE L*, a* and b* values of the teeth were measured by a spectrophotometer. The data were analyzed using IBM SPSS version 23. Results: The differences between the groups were determined with one-way ANOVA. The one-way ANOVA test revealed a statistically significant difference between the groups (p<0.005). Highest color change was observed in lycopene group and the lowest was belongs to green tea group. Conclusions: Proanthocyanidin, white tea and green tea could be good post-bleaching antioxidant alternatives based on their herbal nature.