Microshear Bond Strength of OptiBond All-in-One Self-adhesive Agent to Er:YAG Laser Treated Enamel After Thermocycling and Water Storage

Effect of nonthermal atmospheric plasma on bond strength of composite resin using total-etch and self-etch adhesive systems

Aim

The aim of this study was to assess the impact of nonthermal atmospheric plasma (NTAP) on the bond strength of composite resin following plasma application at different steps of dentin bonding in total-etch and self-etch adhesive systems.

Materials and Methods

Ninety extracted third molars were taken, and the occlusal surfaces were removed until the exposure of the dentin. Samples were distributed into two main groups: Group T: total-etch adhesive system and Group S: self-etch adhesive system. Groups are further subdivided (n = 10) based on plasma application at different steps of dentin bonding. T1: surface etching with 37% phosphoric acid and bonding agent application. T2: plasma application and bonding agent application. T3: plasma application, etching, and bonding agent application. T4: etching, plasma application, and bonding agent application. T5: etching, plasma application, bonding agent application, and again plasma application. S1: self-etch bonding agent application. S2: plasma application and bonding agent application. S3: Bonding agent application and plasma application. S4: plasma application, bonding agent application, and again plasma application. For all the samples, composite resin buildup was done, and shear bond strength (SBS) was measured. The contact angle was measured at different steps of dental adhesive systems.

Statistical Analysis

Two-way analysis of variance and the post hoc Tukey's test were used for analysis, regarding P < 0.05 as statistically significant.

Results

Among all groups of total-etch and self-etch adhesives, Group T4 (48.81 Mpa) and Group S2 (36.59 Mpa), respectively, have demonstrated significantly greater bond strength values than the corresponding control groups.

Conclusion

NTAP enhanced the composite resin's SBS when plasma treatment was done before bonding agent application and significantly reduced the contact angles of the distilled water.

Comparison of Bond Strength of Orthodontic Brackets Onto the Tooth Enamel of 120 Freshly Extracted Adult Bovine Medial Lower Incisors Using 4 Adhesives: A Resin-Modified Glass Ionomer Adhesive, a Composite Adhesive, a Liquid Composite Adhesive, and a One-Step Light-Cured Adhesive

BACKGROUND This study aimed to compare the bond strength of orthodontic brackets onto the tooth enamel of 120 freshly extracted adult bovine medial lower incisors using 4 adhesives: a resin-modified glass ionomer adhesive, a composite adhesive, a liquid composite adhesive, and a one-step light-cured adhesive. MATERIAL AND METHODS The study group (120 freshly extracted bovine medial lower incisors) was divided into equal subgroups depending on the type of adhesive used to fix the brackets to the tooth enamel (n=30), and then according to the observation time (n=10). Orthodontic brackets were fixed onto the tooth enamel for 24 hours (T1), 3 months (T2), and 6 months (T3) using 4 types of adhesives: resin-modified glass ionomer adhesive Fuji Ortho LC, composite adhesive Transbond Plus Light Cure Band, flowable composite adhesive Transbond Supreme Low Viscosity, and a one-step light-cured adhesive GC Ortho Connect. Shear tests and fracture plane analyses were performed. RESULTS Statistically significant differences at time T1 were noted in the comparison of shear stress values when brackets were fixed with GC Ortho Connect adhesive compared to other adhesives (P<0.05), except for the Transbond Plus adhesive (P>0.05). At time T3, significant statistical differences occurred between GC Fuji Ortho LC and the other 3 adhesives (P<0.05). The fracture analysis showed that, regardless of the time function, adhesive-cohesive fractures without damage to the enamel were the most common for all the assessed materials. CONCLUSIONS Of the adhesives evaluated, GC Ortho Connect appears to be the most appropriate choice for bonding orthodontic brackets to the enamel surface.

Degradation and Stabilization of Resin-Dentine Interfaces in Polymeric Dental Adhesives: An Updated Review

Instability of the dentine-resin interface is owed to the partial/incomplete penetration of the resin adhesives in the collagen fibrils. However, interfacial hydrolysis of the resin-matrix hybrid layer complex activates the collagenolytic and esterase enzymes that cause the degradation of the hybrid layer. Adequate hybridization is often prevented due to the water trapped between the interfibrillar spaces of the collagen network. Cyclic fatigue rupture and denaturation of the exposed collagen fibrils have been observed on repeated application of masticatory forces. To prevent interfacial microstructure, various approaches have been explored. Techniques that stabilize the resin–dentine bond have utilized endogenous proteases inhibitors, cross linking agents’ incorporation in the exposed collagen fibrils, an adhesive system free of water, and methods to increase the monomer penetration into the adhesives interface. Therefore, it is important to discover and analyze the causes of interfacial degradation and discover methods to stabilize the hybrid layer to execute new technique and materials. To achieve a predictable and durable adhesive resin, restoration is a solution to the many clinical problems arising due to microleakage, loss of integrity of the restoration, secondary caries, and postoperative sensitivity. To enhance the longevity of the resin-dentine bond strength, several experimental strategies have been carried out to improve the resistance to enzymatic degradation by inhibiting intrinsic collagenolytic activity. In addition, biomimetic remineralization research has advanced considerably to contemporary approaches of both intrafibrillar and extrafibrillar remineralization of dental hard tissues. Thus, in the presence of biomimetic analog complete remineralization of collagen, fibers are identified.

Long-term color stability of light-polymerized resin luting agents in different beverages

PURPOSE

The purpose of this study was to evaluate the long-term color stability of light-polymerized resin luting agents stored in different beverages.

METHODS

Eleven shades of two light-polymerized resin luting agents, Choice2 (A1, A2, B1, TRANSLUCENT, MILKY OPAQUE, and MILKY BRIGHT) and BeautiCem Veneer (H-Value, M-Value, L-Value, Ivory-D, Ivory-L) were selected in this study. Disk-shaped specimens were fabricated with 1.3 mm thickness and 15.0 mm diameter. A total of 198 specimens, 18 for each shade, were prepared and randomly divided into six storage conditions (purified water, coffee, cola, tea, red wine, and air). All shades of specimens were three times measured at three random locations (n = 9) at 24 h storage in air after specimen preparation and then measured after immersion at 1, 3, 6, 9, and 12 mos. using a colorimeter. Then, the color difference (ΔE) between the specimens at 24 h after preparation and after storage in each liquid for 12 mos. was calculated. Statistical analysis was performed using Steele-Dwass multiple comparison test of the ΔE values or one-way ANOVA and Tukey's honest significant difference test.

RESULTS

For all immersion conditions, ΔE was significantly higher than air (control). The ΔE of the shades in the various storage conditions showed no significant difference between Purified Water-Cola and Coffee-Tea. Comparisons of the color components L*, a*, and b* for each shade showed different behaviors among the shades.

CONCLUSIONS

The results suggest that the color stability of light-polymerized resin luting agents may differ between different shades and beverages.

Bond Strength of Metallic or Ceramic Orthodontic Brackets to Enamel, Acrylic, or Porcelain Surfaces

Bonding strategies within different brackets and dental materials are still a challenge concerning adhesion and dental surface damage. This study compared the shear and tensile bond strength of orthodontic ceramic and metallic brackets to enamel, acrylic, and ceramic surfaces after thermal cycling. Dental surfaces were divided into three groups: enamel, ceramic, and acrylic. Each group received stainless-steel and ceramic brackets. After thermal cycling, specimens were randomly divided into two subgroups considering tensile (TBS) or shear bond strength (SBS) test. After the mechanical testing, scanning electron and optical microscopy were performed, and the adhesive remnant index (ARI) was determined. The two-way ANOVA full factorial design was used to compare TBS, SBS, and ARI on the surface and bracket type (α = 0.05). There were significant differences in TBS, SBS, and ARI values per surface (p < 0.001 and p = 0.009) and type of bracket (p = 0.025 and p = 0.001). The highest mean SBS values were recorded for a ceramic bracket bonded to an acrylic surface (8.4 ± 2.3 MPa). For TBS, a ceramic bracket bonded to acrylic showed the worst performance (5.2 ± 1.8 MPa) and the highest values were found on a metallic bracket bonded to enamel. The adhesion of metallic or ceramic brackets is enough for clinical practice although the damage of the enamel surface after debonding is irreversible and harmful for the aesthetic outcome of the teeth.

Microshear Bond Strength of a Self-adhesive Composite to Erbium Laser-Treated Primary Enamel

Introduction: Advances have been made in the composition of flowable composites in recent years and self-adhering composites, which do not require a bonding agent, have recently been introduced to the market. This study aimed to assess the microshear bond strength (µSBS) of a self-adhering flowable composite (Vertise) to primary enamel treated with a graphite disc with silicon carbide particles (SIC) and laser irradiation, the result of which was compared to that of a conventional flowable composite (Premise). Methods: In this in vitro, experimental study, 72 samples of sound primary enamel were evaluated. A smooth enamel surface was obtained using a graphite disc. Next, the erbium chromium yttrium scandium gallium garnet (Er,Cr:YSGG) laser was used for enamel surface treatment in half of the samples (n=36). All the samples were then randomly divided into 4 groups of (i) Premise flowable composite (PF) without laser (n=18), (ii) Vertise flowable composite (VF) without laser (n=18), (iii) PF with laser (n=18), and (iv) VF with laser (n=18). The teeth were then incubated at 37°C for 24 hours and were then subjected to thermocycling. The µSBS of samples was measured using a universal testing machine and reported in megapascal (MPa). Data were analyzed using SPSS via the two-way ANOVA and independent-samples t test at P<0.05. Results: The mean µSBS of VF was significantly higher to the laser-treated samples (13.60±5.47) compared with the non-treated samples (5.89±2.42) (P<0.001). However, no significant difference was noted in the µSBS of PF to the laser-treated (13.18±3.45) and non-treated samples (16.06±3.52) (P=0.058). Conclusion: The µSBS of the conventional flowable composite is higher than that of the self-adhering flowable composite to the enamel of primary teeth. Enamel surface treatment with laser irradiation increases the µSBS of self-adhering flowable composites.

Recent Advances in Adhesive Bonding - The Role of Biomolecules, Nanocompounds, and Bonding Strategies in Enhancing Resin Bonding to Dental Substrates

PURPOSE OF REVIEW

To present an overview on the main agents (i.e., biomolecules and nanocompounds) and/or strategies currently available to amplify or stabilize resin-dentin bonding.

RECENT FINDINGS

According to studies retrieved for full text reading (2014-2017), there are currently six major strategies available to overcome resin-dentin bond degradation: (i) use of collagen crosslinking agents, which may form stable covalent bonds with collagen fibrils, thus strengthening the hybrid layer; (ii) use of antioxidants, which may allow further polymerization reactions over time; (iii) use of protease inhibitors, which may inhibit or inactivate metalloproteinases; (iv) modification of the bonding procedure, which may be performed by using the ethanol wet-bonding technique or by applying an additional adhesive (hydrophobic) coating, thereby strengthening the hybrid layer; (v) laser treatment of the substrate prior to bonding, which may cause specific topographic changes in the surface of dental substrates, increasing bonding efficacy; and (vi) reinforcement of the resin matrix with inorganic fillers and/or remineralizing agents, which may positively enhance physico-mechanical properties of the hybrid layer.

SUMMARY

With the present review, we contributed to the better understanding of adhesion concepts and mechanisms of resin-dentin bond degradation, showing the current prospects available to solve that problematic. Also, adhesively-bonded restorations may be benefited by the use of some biomolecules, nanocompounds or alternative bonding strategies in order to minimize bond strength degradation.