Introduction: Bleaching process can affect surface roughness of enamel, which is a vital factor in esthetic and resistance of tooth. The aim of this study was to compare surface roughness of enamel in teeth bleached using Diode and Neodymium-Doped Yttrium Aluminium Garnet (Nd: YAG) lasers with those bleached using conventional method. Methods: In this study, 75 anterior human teeth from upper and lower jaws (These teeth extracted because of periodontal disease) were randomly divided into 5 groups. Group 1: Laser white gel (Biolase, USA) with 45% hydrogen peroxide concentration and GaAlAs Diode laser (CHEESE TM , GIGAA, China), group 2: Heydent gel (JW, Germany) with 30% Hydrogen peroxide concentration and Diode laser, group 3: Laser white gel and Nd:YAG laser (FIDELIS TM , Fotona, Slovenia), group 4: Heydent gel and Nd:YAG laser and group 5: The Iranian gel Kimia (Iran) with 35% hydrogen peroxide concentration were used. Surface roughness of the samples was measured using the Surface Roughness Tester system (TR 200 Time Group, Germany) before and after bleaching. In each group, one sample was randomly selected for SEM analysis. Results:The results showed that the mean surface roughness of the teeth before and after bleaching had a significant difference in all the study groups. It was indicated that after bleaching, the mean surface roughness had increased in all the study groups. The highest surface roughness was seen in the conventional bleaching group and the lowest surface roughness was reported in group 3 (laser white gel + diode laser), in which the average surface roughness increased by only 0.1 µm. Conclusion: It was concluded that using the Laser white gel and the diode laser for bleaching resulted in the least surface roughness compared to conventional method.

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This study evaluated the micro-tensile bond strength of new and previous composite resin restorations after surface treatment with diamond bur and Er,Cr:YSGG laser at different power settings (2,3 and 4 W). Micro-hybride composite resin was inserted in metallic mold 5 ×5 ×15 mm and cured for 40 sec according to manufacturer's instruction.12 blocks were made. The bonded surfaces of the 12 blocks so obtained were subsequently ground using Silicon Carbide papers 1200 grit, for 15 seconds under running water. Then the samples randomly were divided into 4 groups: (G1) Bur-treated, (G2) Er,Cr:YSGG laser with power of 2 W and energy of 100 mJ, (G3) Er,Cr:YSGG laser with power of 3 W and energy of 150 mJ, (G4) Er,Cr:YSGG laser with power of 4 W and energy of 200 mJ. One sample of each group was analyzed by SEM while, after cutting the blocks to 1 mm of area samples, the others samples were mechanically tested by Universal testing machine with the speed of 0.5 mm per minute till fracture point. Data were analysed using One-Way ANOVA and Tukey Test. T-test showed no significantly differences between G2 and G4(P=0.064) while G3 demonstrated significant differences than G2 (P=0.001) and G4(P=0.000) and also between samples treated with bur (G1) and G2 (P=0.242) ,G3 (P=0.000) ,G4 (P=0.829); G1 didn't significantly differ to G2 and G4(P>0.05), while G1 and G3(P<0.05). On surface treatment of repaired composite, samples treated by laser at 3W power showed better condition of micro-tensile bond strength.

Background and Aim: Color match between prosthetic restorations and natural teeth is challenging in dentistry. The aim of the current study was to assess the effect of accelerated aging on color stability of two silica-based ceramics with leucite and lithium disilicate crystalline phases after glazing and polishing surface treatments. Materials and Methods: In this experimental study, 30 disc-shaped specimens (1.5x10mm) of IPS e.max Press and Ceramco III ceramics were fabricated according to the manufacturers' instructions. The specimens were randomly divided into two groups of surface treatments (glazing and polishing) and were then subjected to accelerated aging for 300 hours. Color parameters were measured before and after aging using a spectrophotometer. The L*, a* and b* parameters and the color change (∆E) of ceramics (based on the CIE L*a*b* system) before and after glazing were determined by spectrophotometry. Data were analyzed using two-way ANOVA and t-test. P<0.05 was considered statistically significant. Results: After 300 hours of aging, the color stability (∆E), ∆L and ∆b of polished group was less than that of glazed group. The two ceramic types were not significantly different in terms of ∆E (range: 1.31 to 2.53; P=0.055). Conclusion: Glazed silica-based ceramics had higher color stability than polished ceramics after aging in our study. Color stability of silica-based ceramic systems was influenced by the surface texture and not the type of crystalline phase.

The study aimed to evaluate the effect of different output powers of Er:YAG laser on microtensile bonding strength of indirect composite to resin cements.36 indirect composite blocks (GC Gradia DA2, Japan) size 15 × 10 × 10 mm(3) were constructed, and divided into 12 groups, as follows:G1: control group (no treatment); Groups G2 to G6: treated with Er:YAG laser (2,940 nm) in noncontact mode, frequency 20 Hz, pulse duration 470 µs, with output power ranging from 2W to 6W; Groups G7 sandblasting, Groups 8 to G12: as Groups G2 to G 6 with preparatory sandblasting. One specimen from each group was analyzed by SEM; each specimen was fixed to a specialized metal jig using cyanoacrylate (Mitreapel, Beta Kimya San. Ve TIC, Iran) and debonded under tension with a universal testing machine (Zwick, Germany) at a crosshead speed of 0.5 mm min(-1). Sandblasting and laser can improve bond strength above an energy level of 150 mJ. SEM evaluation of laser-treated specimens showed irregularities and deep undercuts. T test analysis showed no significant difference between sandblasted and non-sandblasted group, with laser output power of 0, 100, or 150 mJ (P = 0.666, P = 0.875, and P =  .069); in the specimens irradiated with energy output of 200, 250, or 300 mJ, sandblasted specimens showed higher bond strength than non-sandblasted ones. The results demonstrate that, in composite resin irradiated with laser at energy output of 200-300 mJ, sandblasting might be a suitable procedure to enhance bond strength of resin cement.