Effect of different treatment on Surface Morphology of laser bleached teeth: SEM Evaluation

Objective: The aim of this study was to evaluate and compare the effect of dental surface treatment with Er:YAG , Nd:YAG ,CO2 lasers and sodium ascorbate to recently laser bleached enamel by scanning electron microscope (SEM).Methods: 15caries-free extracted human third molars were selected for this study. The samples were bleached by Heydent JW power activated by diode laser 810 nm. After 7 day, the bleaching procedure was repeated as same as first time. Then, the samples were divided to five groups randomly as follow: Group 1: treated using Nd:YAG laser with output power of 1 W, Group 2: treated using Er:YAG laser with output power of 0.5 W, Group 3: treated using CO2 laser with output power of 0.5 W, Group 4: sodium ascorbate 10%, Group 5: no surface treatment. After treatments, the surfaces were evaluated using Scanning Electron Microscope (SEM) analysis.Results: The surfaces treated by Nd:YAG laser showed some melting area but the surface treated by Er:YAG laser showed irregular and micro porous surface. CO2 laser treatment of surfaces resulted in melting of superficial layer of dental substrate and micro cracks. Sodium ascorbate did not change the surface except changes raised from bleaching.Conclusion: Laser conditioning of laser-bleached teeth can be beneficial for enhancing bond  strength of resin material to recently bleached enamel

The Effect of Incorporation of 0.5 %wt. Silica Nanoparticles on the Micro Shear Bond Strength of a Resin Modified Glass Ionomer Cement

Statement of the Problem: The clinical success of glass ionomer restorations depends on the strength of resin-modified glass ionomer (RMGI) cement bonding to dentin and there is limited information available regarding the bond strength of resin modified glass ionomers containing silica nanoparticles to dental structures. Purpose: The aim of this study was to compare the microshear bond strength (µSBS) of RMGI with and without silica (SiO2) nanoparticles to dentin of permanent teeth. Materials and Method: in this experimental study, the occlusal surfaces of 30 freshly extracted intact third molars were ground to expose the flat dentin and after conditioning with 20% poly acrylic acid, were randomly assigned to two main groups (n=15). The first group was filled with RMGI (Fuji II LC, GC) and the second group was filled with RMGI plus 0.5%wt. silica nanoparticles. Then, each main group was divided into three subgroups, and then stored in an incubator at 37 oC with 100% humidity for 1, 7, and 30 days. The µSBS test was performed using a universal testing machine (1 mm/min). The data were analyzed by t-test, repeated measures ANOVA and Tukey test (p< 0.05). Results: There were no statistically significant differences between the mean µSBS of the groups with and without nanoparticles along the different storage periods (p> 0.05). There was significant difference in µSBS values among the three different storage periods in all the tested materials (p< 0.05). Conclusion: Incorporation of 0.5 %wt. silica nanoparticles did not compromise the µSBS of Fuji II LC RMGI to dentin

Bonding Durability of Four Adhesive Systems

Objectives: This study aimed to compare the durability of four adhesive systems by assessing their microtensile bond strength (MTBS) and microleakage during six months of water storage. Materials and Methods: A total of 128 human third molars were used. The adhesives tested were Scotch Bond Multipurpose (SBMP), Single Bond (SB), Clearfil-SE bond (CSEB), and All-Bond SE (ABSE). After sample preparation for MTBS testing, the microspecimens were subjected to microtensile tester after one day and six months of water storage. For microleakage evaluation, facial and lingual class V cavities were prepared and restored with composite. After thermocycling, microleakage was evaluated. Bond strength values were subjected to one-way ANOVA and Tamhane’s test, and the microleakage data were analyzed by the Kruskal-Wallis, Dunn, Mann Whitney and Wilcoxon tests (P<0.05). Results: Single Bond yielded the highest and ABSE yielded the lowest bond strength at one day and six months. Short-term bond strength of SBMP and CSEB was similar. After six months, a significant decrease in bond strength was observed in ABSE and SBMP groups. At one day, ABSE showed the highest microleakage at the occlusal margin; however, at the gingival margin, there was no significant difference among groups. Long-term microleakage of all groups at the occlusal margins was similar, whilst gingival margins of SBMP and SB showed significantly higher microleakage. Conclusion: The highest MTBS and favorable sealability were obtained by Clearfil SE bond. Water storage had no effect on microleakage of self-etch adhesives at the gingival margin or MTBS of CSEB and SB.

Effect of Proanthocyanidine Pre-treatment on Bonding Durability of Three Resin Cements with Fiber Post: Effect of proanthocyanidin on bonding durability

Background and objectives: Establishing a strong and durable bond between cements and root canal dentin has been widely studied. Since the effectiveness of proanthocyanidin (PA) as a collagen cross-linker has been proven, the strength and durability of the bond between fiber posts and root canal dentin are expected to increase following the application of PA. Therefore, the present study aimed to assess the effect of PA pre-treatment on the bonding durability of fiber posts with three resin cements. Materials and methods: Ninety human single-rooted teeth with similar anatomical root shape and length were collected. After decoronation and root canal therapy, the teeth were divided into nine groups: etch and rinse (ER), self-etch (SE), self-adhesive (SA), PA pre-treatment and etch and rinse (PAER), PA pre-treatment and self-etch (PASE), PA pre-treatment and self-adhesive (PASA), chlorhexidine (CHX) pre-treatment and etch and rinse (CHXER), CHX pre-treatment and self-etch (CHXSE), and  [ CHX pre-treatment and self-adhesive (CHXSA). After microslicing the roots, push-out tests were performed immediately for half the specimens and after three months of water storage and thermocycling for the other half. Data were analyzed using two-way ANOVA and Tukey’s test with α=0.05. Results: Resin cement type (P=0.001), dentin pre-treatment method (P=0.001), water storage and thermocycling (P=0.001), and the root region (P=0.001) had significant effects on bond strength. Conclusion: SA resin cement had the lowest immediate and long-term bond strength in comparison with the other two cements. For ER and SE resin cements, no pre-treatment led to higher immediate and long-term bond strength. For SE and SA resin cements, PA pre-treatment inhibited the loss of bond strength in the long-term. The bond strength in the coronal region was higher than that in other regions

Comparison of the Effects of Microfilled and Hybrid Composite Resin Restorations on the Fracture Resistance of Extensively Weakened Teeth

Background and Aim : Composite resins can play an important role in dentin support and enamel strength via bonding to tooth structure. The purpose of this study was to compare the effects of hybrid and microfilled composite restorations on the fracture resistance of extensively weakened teeth .   Materials and Methods : In this case control study 40 intact maxillary premolars were mounted in transparent acrylic resin blocks. The samples were divided into 4 groups (n=10 each). Group PC comprised of intact teeth, without preparation and restoration. In other three groups MOD preparations with constant depths and converged walls toward occlusal surfaces were prepared. Group NC composed of teeth with preparations but without any restoration. Group HR included prepared and restored teeth using a hybrid composite and Group MR contained prepared and restored samples with a microfilled composite. Samples were thermocycled (500 cycles in 5-55° C), then were placed under compressive loads in a universal testing machine, and the curves were drawn with a software called Test Xpert .   Results : Mean fracture resistance in HR, MR, PC, and NC groups were 48.1010, 59.1773, 83.1420, and 21.9220, respectively. There was a statistically significant difference among the groups(P<0.05).   Conclusion : The increasing effect of microfilled group on the fracture resistance of restored teeth is significantly more than that of hybrid group

Effect of Different Surface Treatments on Microtensile Bond Strength of Composite Resin to Normal and Fluorotic Enamel after Microabrasion

Objectives: This study aimed to determine the effect of surface treatments such as tooth reduction and extending the etching time on microtensile bond strength (µTBS) of composite resin to normal and fluorotic enamel after microabrasion. Materials and Methods: Fifty non-carious anterior teeth were classified into two groups of normal and fluorotic (n=25) using Thylstrup and Fejerskov index (TFI=4-6). Teeth in each group were treated with five modalities as follows and restored with OptiBond FL and Z350 composite resin: 1-Etching (30 seconds), bonding, filling (B); 2-Tooth reduction (0.3mm), etching, bonding, filling (R-B); 3-Microabrasion (120 seconds), etching, bonding, filling (M-B); 4- Microabrasion, tooth reduction, etching, bonding, filling (M-R-B); and 5- Microabrasion, etching (60 seconds), bonding, filling (M-2E-B). Ten experimental groups (n=5) were designed; 150 rectangular samples (10 in each group) with a cross-sectional area of 1×1mm2 were prepared for µTBS test. Failure mode was determined under a stereomicroscope and one specimen was selected from each group for scanning electron microscopy (SEM) analysis. Data were analyzed using two-way ANOVA and Tukey’s test. Results: The µTBS to normal enamel was higher than to fluorotic enamel in all groups except for group (R-B). The Maximum and minimum µTBS were noted in the group (normal, reduction, bonding) and (fluorosed, microabrasion, bonding), respectively.  Tooth reduction increased µTBS more effectively than extended etching time after microabrasion. Conclusions: Fluorosis may reduce µTBS of composite resin to enamel. Microabrasion reduced the bond strength. Tooth reduction and extended etching time increased µTBS of composite resin to both normal and fluorotic enamel.

Evaluating and comparing the effect of two liquid polishes on the polish retention of two nanocomposites

Background and Aims: Finishing and polishing of composites is a critical step influencing the clinical service of restorations. The aim of this article was to evaluate and compare the effect of two liquid polishes on the polish retention of two nanocomposites. Materials and Methods: Eighty standardized disk-shaped specimens (4×2 mm) were prepared from two nanocomposites (n=40), including one nano-filled composite (Filtek Z350 XT-3M ESPE, USA) and one nano-hybrid composite (Aelite Aesthetic Enamel-Bisco, Inc. Schaumburg, USA). The specimens were randomly divided into 4 subgroups (n=10) based on the method of finishing (F) and polishing (P) procedures: M: as control, polymerized under Mylar strip; S: finish and polish with a sequence of Sof-Lex discs (3M ESPE, USA); SP: finish and polish with Sof-Lex discs and use of Permaseal liquid polish (Ultradent products, Inc. USA); SB: finish and polish with Sof-Lex discs and use of Biscover liquid polish (Bisco, Inc. Schaumburg, USA). The specimens were undergone pH cycling and brushing machine and then, the average surface roughness (Ra) and average profile changes along the desired area (Rz) of the specimens were determined with profilometer instrument. Two-way and one-way analysis of variance (ANOVA) was used to compare the mean of surface roughness. Then, Tukey test was used to identify the groups responsible for the difference and t-test was used to compare the mean of surface roughness. Results: The type of composite and the method of polishing procedure had no effect on the mean Ra (P=0.733) but it had significant effect on Rz1 factor (P=0.025). Conclusion: Using liquid polish after polishing discs had no effect on the polish retention of nanocomposites