Journal of Dental Medicine

Background and Aims: Recently, the addition of nanoparticles into the restorative materials and tooth preparation by laser for improving the bond strength have been concidered by researchers. The aim of this study was to investigate the shear bond strength of the bioactive glass ionomer containing titanium particles and a conventional glass ionomer with two surface treatments by Er-YAG laser and conventional methods.
Materials and Methods: In this in-vitro study, 64 sound extracted premolars were collected. For conventional method, the specimens were prepared in such a way that dentin surfaces with a depth of 0.5 millimeter created at distance of 2 mm from the joint of CEJ at the root or crown.  In the laser group, after preparing the teeth, the surface area was prepared by Er-YAG laser. Then, in the middle part of the buccal surface, a cylindrical mold with dimensions of 3.5 mm in diameter and 4 mm in height was placed and for each group was filled with its own glass ionomers. The  specimens  were divided into 8 groups by simple random sampling (n=8): A (laser, conventional glass ionomer, coronal dentin)/ B (laser, glass ionomer containing titanium nanoparticle, coronal dentin)/C (conventional, conventional glass ionomer, coronal dentin)/ D (conventional, glass ionomer containing titanium nanoparticle, coronal dentin)/ E (laser, conventional glass ionomer, root dentin)/ F (laser, glass ionomer containing titanium nanoparticle, root dentin)/ G (conventional, conventional glass ionomer, root dentin)/ H (conventional, glass ionomer containing titanium nanoparticle, coronal dentin). Finally, the shear bong strength by a universal testing machine was measured at a cross-head speed of 1 mm/min. For data analysis, Two-way ANOVA test was used to evaluate the effect of each variable and their interaction on the shear bond strength and Tukey test was used to compare the two groups.
Results: There was significant difference only between groups B with C (P=0.002), E (P=0.007), G (P=0.001) and H (P=0.01). The highest bond strength was found for group B (laser, glass ionomer containing titanium nanoparticle, coronal dentin) and the lowest bond strength for group G (conventional, conventional glass ionomer, root dentin).
Conclusion: All three factors of Er-YAG laser, glass ionomer containing titanium nanoparticle and coronal dentin had a positive effect on the improvement of the bond strength.

Background and Aims: Insufficient adhesion between fiber post and root canal is the main reason for the failure of the restoration and the fiber post surface treatment can imprive the bond strength. Additionally, there is disagreement about the ideal method of preparation to achieve the desired bond. The aim of this study was to compare the effect of two surface treatment methods on push-out bond strength of fiber posts to root canals.
Materials and Methods: In this study, 45 healthy incisor teeth underwent root canal treatment. After preparing the post space, they were divided into 3 groups of 15, based on the surface treatment methods of the fiber post. In the first group as control group, no surface treatment was done on the fiber post. In the second and third groups, sandblasting with Cojet sand particles and 810 nm diode laser were used for surface treatment, respectively. Then, fiber posts were placed in all root channels by a self-adhesive resin cement. Then, the roots were cut in such a way that from each, 3 pieces with a thickness of 1.5 mm were obtained. Finally, the push-out bond strengths were measured using a universal testing machine. Data were analyzed by ANOVA using SPSS software. The level of significance was considered at P<0.05.
Results: The average bond strengths in three groups were as follows: control group, 2.877 ±1.430, sandblast group 6.318±3.444, and laser 4.224 ±1.890 MPa ± SD. The difference in the bond strength between the sandblast group and the control group was significant (P=0.001). However, the average of the bond strength of laser group was not significantly different from the control group. (P=0.03).
Conclusion: The findings of this study showed that unlike diode laser radiation, the use of Cojet sand particles for sandblasting the fiber post surfaces significanlty improved the bond strength.

Background and Aims: Finding an appropriate method for polishing that can be used in dental practices to improve the longevity and ease of dental restorations is of great importance. The aim of this study was to evaluate the effect of different polishing methods on the surface roughness of two types of nano-hybrid composites, an in vitro study.
Materials and Methods: In this study, 42 samples in the form of discs (6 mm in diameter and 3 mm in thickness) of two nano-hybrid composites (Charisma Kulzer and EvoCeram Tetric IPS) were prepared. Each group had 21 samples (polymerized in a mold made of polyfluorohalide material) and were all shaded (A2 color). To prevent mirror-like reflections, each sample was covered. A 2 kg load was applied for 30 seconds on each sample, after which the composites were removed. The samples were stored for 7 days in deionized water at room temperature and in the dark. After this period, the samples underwent finishing and polishing procedures. Seven random samples from each composite group were polished using different methods: System Gloss Composite LUCIDA, EVE polishing discs, and EVE polishing discs + Cosmedent polish. The surface roughness was measured using a profilometer, and observations were made under a microscope. Data were analyzed using SPSS 25 software with t-tests, ANOVA, and the Bonferroni post hoc test.
Results: The two-stage method using EVE polishing discs showed significantly the lowest surface roughness in both types of composites (P<0.0001). The type of composite did not have a significant effect on initial surface roughness (P=0.067), but the polishing method had a significant effect on the surface roughness (P<0.0001). The difference in the mean surface roughness was statistically significant among different polishing methods for either type of composites (P<0.0001). The t-test analysis showed no significant difference in the surface roughness between the two types of composites with different polishing methods (P>0.05), except in the LUCIDA polishing system where a significant difference was observed in both groups.
Conclusion: The results showed that the polishing method had a significant effect on the surface roughness and not the type of composte. The use of EVE polishing discs effectively reduced the surface roughness in both types of nano-hybrid composites used in the present study.