Effect of Different Powers of Er,Cr:YSGG Laser Treatment on Surface Morphology of Microhybride Composite Resin: Scanning Electron Microscope (SEM) Evaluation

Introduction: The aim of this study was to evaluate and compare microhybride composite treated by bur and different power of Erbium, Chromium doped Yttrium Scandium Gallium Garnet (Er,Cr:YSGG) laser by Scanning Electron Microscope (SEM).Methods: 21 microhybride composite blocks (DiaFil TM, DiaDent, Korea) with 2 × 4 × 4 mm dimensions were made. The bonding surface of these blocks were polished, The samples were put into 6 groups for laser irradiation as follows: Group 1 (power: 1W, Energy: 50 mJ); Group 2(power: 2 W, Energy: 100mJ); Group 3 (power: 3W, Energy: 150mJ); Group 4 (power: 4W, Energy: 200mJ); Group 5 (power: 5W, Energy: 250mJ) and Group 6(power:6 W, Energy :300mJ). One group prepared by bur- treated. All samples were prepared by repetition rate of 20 Hz. Then, the samples were prepared for SEM examination.Result: Some irregularities were seen in Er,Cr:YSGG laser samples in comparison to Bur group that produced favorable surface for adhesion of repair composite.Conclusion: Among different lasers, Er;Cr:YSGG laser can be chosen as a suitable technique for surface treatment of unsatisfactory composites.Key words: SEM evalution; laser; composite resi

Effect of Type of Surface Treatment and Adhesive System on Shear Bond Strength of Composite Resin to a Non-Precious Metal Alloy

Background and Aim: Fractured metal-ceramic restorations may be repaired with composite in some cases to postpone the fabrication of a new restoration. Knowledge about the bond strength can help predict the success rate of this treatment modality. The aim of this study was to assess the effect of two types of mechanical surface treatment of metal along with the use of different adhesive systems on bond strength of composite to a non-precious metal alloy. Materials and Methods: In this in vitro experimental study, 110 metal discs were fabricated of nickel chromium alloy and were randomly divided into two groups of surface preparation with sandblasting (S) and bur (B). In each group, the samples were divided into five subgroups based on the adhesive system and composite resin used: Group NC: Z350 composite without application of adhesive; group AC: Alloy primer/Clearfil AP-X; group ZA: Z-Prime Plus/Aelite; group MT: Monobond Plus/Tetric N Ceram; group AZ: Adper Single Bond Plus/Z250. In the positive control group (PC), metal discs were covered with feldspathic porcelain. All samples were then subjected to 1000 thermal cycles and shear bond strength was measured. Data were analyzed using one-way ANOVA, two-way ANOVA and Tukey’s HSD test (P<0.05). Results: The interaction effect of type of surface treatment and type of adhesive system on bond strength was significant (P<0.05). The highest bond strength (148.7 MPa) was noted in group PC and the lowest bond strength (2.78 MPa) was noted in group B+NC. The bond strength was 13.72 MPa in group S+AZ, 10.84 MPa in group B+AZ and 12.72 MPa in group S+ZA, which did not have a significant difference with the bond strength of group PC. Conclusion: Type of surface preparation and adhesive affect the bond strength. Surface preparation by sandblasting or bur combined with the use of Adper Single Bond Plus and also combination of Z-Prime Plus adhesive and sandblasting yielded the highest bond strength value

Efficacy of E-Learning via the Website of Tehran University of Medical Sciences for Diagnosing Tooth Discolorations and Treatment Planning by Senior Dental Students

The efficacy of methods like e-learning as a supplement to traditional face-to-face instruction needs to be evaluated in dental courses. This study aimed to assess the efficacy of posting case presentations on one of the educational websites of  the virtual school of Tehran University of Medical Sciences called “SARMAD” to enhance the ability of senior dental students to diagnose tooth discolorations and offer treatment plans. This experimental study had a pre-test/post-test control group design and was conducted on 63 senior dental students. After filling out the primary questionnaire and obtaining a written informed consent, students participated in a pre-test and were then randomly divided into two groups of intervention and control. Fifteen case presentations were posted on the university website (SARMAD) during 6 weeks and discussed. Then, students participated in a post-test. Students’ perspectives and their satisfaction with the website were assessed by a questionnaire. For ethical purposes, the same program was also offered to the controls. The post-test score was significantly higher than the pre-test score in the intervention group (P<0.001); but in the control group, the post-test score was only slightly higher than the pre-test score (P=0.128). In the intervention group, 70% stated that they would suggest this method as an efficient educational modality; 93.3% stated that this method would be beneficial as a supplement to conventional education; 16.7% ranked the SARMAD website excellent, 30% ranked it good, 33.3% acceptable, 16.7% moderate and 3.3 poor. It appears that this instructional modality may be efficiently used as a supplement to traditional instruction in undergraduate dental curricula

Comparison of Dentin Permeability After Tooth Cavity Preparation with Diamond Bur and Er:YAG Laser

Objectives: The aim of this study was to compare the permeability of dentin after using diamond bur and Er:YAG laser. Materials and Methods: Seventy-two recently extracted, intact, and restoration-free human permanent molars were used in this study. The samples were randomly divided into three groups of 24 each and class I cavities were prepared as follows. Group 1: High speed diamond bur with air and water spray. Group 2: Er:YAG laser. Group 3: Er:YAG laser followed by additional sub-ablative laser treatment. Each group consisted of two subgroups with different cavity depths of 2mm and 4mm.  The entire cavity floor was in dentin. Two samples from each subgroup were observed under scanning electron microscope (SEM). The external surfaces of other samples were covered with nail varnish (except the prepared cavity) and immersed in 0.5% methylene blue solution for 48 hours.  After irrigation of samples with water, they were sectioned in bucco-lingual direction. Then, the samples were evaluated under a stereomicroscope at ×160 magnification. The data were analyzed using two-way ANOVA and Tukey’s HSD test. Results: Two-way ANOVA showed significant difference in permeability between groups 2 and 3 (laser groups with and without further treatment) and group 1 (bur group). The highest permeability was seen in the group 1. There was no significant difference in dentin permeability between groups 2 and 3 and no significant difference was observed between different depths (2mm and 4mm). Conclusion: Cavities prepared by laser have less dentin permeability than cavities prepared by diamond bur