[Morphologic evaluation of the bonding between adhesive/composite resin and dentin irradiated with Er:YAG and Nd:YAG lasers: comparative study using scanning microscopy]

Comparative evaluation of bond strength of diode and neodymium-doped:Yttrium aluminum garnet-assisted bleached enamel with nanofilled composite: An in vitro study

Background

The world of esthetic dentistry is constantly making efforts toward the management of tooth staining. Laser-assisted bleaching is needed before adhesive restorations and has become common and advantageous as it accelerates bleaching action, reduces postoperative sensitivity, and promotes recrystallization of enamel.

Aim

The study aimed to evaluate and compare the bond strength of diode (Biolace: EpicX) and neodymium-doped:yttrium aluminum garnet (Nd:YAG) (LightWalker, Fotona, Slovenia) assisted bleached (Pola Office, SDI) enamel with nanofilled composite (GC Solare Sculpt).

Materials and Methods

The samples were divided into three groups (n = 11): Group A - Conventionally bleached enamel, Group B - Diode laser-assisted bleached enamel, Group C - Nd:YAG laser-assisted bleached enamel. After storing samples in Artificial Saliva for 2 weeks, bonding was performed, and nanofilled composite resin was applied through an incremental method. Samples were subjected to shear bond strength (SBS) analysis.

Conclusion

The use of Nd:YAG laser on bleached enamel significantly increases the bond strength with nanofilled composite resin.

The effects of Er:YAG, Nd:YAG, and Diode (940nm) Lasers irradiation on Microtensile bond strength of two steps self-etch adhesives

Background and aims

Nowadays, studies show the effective laser irradiation role on the adhesion of bonding agents to the dentin. Therefore, the present study was set to find an appropriate protocol for the use of Nd:YAG, Er:YAG, and Diode lasers during the application of two steps self-etch adhesives in direct dental restorations in order to achieve higher microtensile strength.

Materials and Methods

A total number of 100 extracted healthy teeth were selected. After removing occlusal enamel and exposing dentin, samples randomly divided into ten groups: Group Control (C), two steps self-etch adhesives was applied in accordance with the manufacturer instructions, without using laser systems; Groups Er-YAG, laser (2940 nm, 10 Hz, 0.4w, 40 mJ) irradiated Before applying Primer (Er-BP subgroup), After applying Primer (Er-AP subgroup), After applying Bonding (Er-AB subgroup); Groups Nd-YAG, laser (1064 nm, 10 Hz, 1.2w, 40 mJ) irradiated Before applying Primer (Nd-BP subgroup), After applying Primer (Nd-AP subgroup), After applying Bonding (Nd-AB subgroup); Groups Diode, laser (940 nm, 10 Hz, 0.7w, 70 mJ) irradiated Before applying Primer (D-BP subgroup), After applying Primer (D-AP subgroup), After applying Bonding (D-AB subgroup). After intervention and composite build up, the samples were stored 24 hours in 37°C distilled water. The microtensile strength was measured using the universal testing machine. The data were analyzed by one-way ANOVA test and post hoc Tukey test. (p < 0.05).

Results

The Means and standard deviations of the groups were as follow: C = 30.09 ± 4.21, Er-BP = 18.83 ± 4.21, Er-AP = 14.43 ± 3.12, Er-AB = 19.67 ± 4.96, Nd-BP = 20.35 ± 5.55, Nd-AP = 39.85 ± 4.13, Nd-AB = 18.16 ± 3.36, D-BP = 26.74 ± 5.05, D-AP = 28.11 ± 5.12, D-AB = 37.28 ± 5.61. The mean microtensile strength achieved in groups: Nd-AP and D-AB were significantly higher than control group (p < 0.05). Groups D-BP and D-AP had no significant difference in comparison with control group while the remaining groups had significantly lower values (P < 0.05).

Conclusions

Nd:YAG laser irradiation after applying the primer, and diode laser irradiation after applying the bonding agent, both can improve the microtensile bond strength in two steps self-etch adhesive systems significantly.

Influence of dentin thickness on intrapulpal temperature under simulated pulpal pressure during Nd:YAG laser irradiation

The aim of this study was to evaluate the effects of dentin thickness and pulpal pressure simulation (PPS) on the variation of intrapulpal temperature (∆T) when submitted to an adhesive technique using laser irradiation. Sixty sound human molars were sectioned and randomly divided into two groups (n = 30): group 1-1 mm of dentin thickness; group 2-2 mm of dentin thickness. Each group was divided into two subgroups (n = 15): subgroup A-absence of PPS; subgroup P-presence of PPS (15 cm H₂O), sequentially treated with the following: 37 % phosphoric acid, adhesive system (Adper Single Bond), irradiation with Nd:YAG laser (1064 nm, 10 Hz, 60 s) using 60, 80, and 100 mJ/pulse energy parameters and light-curing (10 s). The ∆T was evaluated during the laser irradiation with a digital thermometer. Data were analyzed by three-way ANOVA and Tukey tests (p < 0.05). Three-way ANOVA revealed no significant differences for dentin thickness (p = 0.6512) on ∆T. PPS significantly reduced ∆T (p = 0.0001). The laser energy parameters (p = 0.0027) indicated that 100 mJ presented with significantly greater ∆T when compared to the groups irradiated with 80 and 60 mJ. Dentin thickness did not affect ∆T. The presence of PPS reduced the mean temperature values. The Nd:YAG laser energy parameters had a negative influence on the variation of temperature in the absence of PPS. In the presence of PPS, there was no risk to the pulp, since this study obtained temperature increases below 5.5 °C for all energy parameters, showing the technical viability for in vivo conditions.

Combined FT-Raman and SEM Studies of the Effects of Er:YAG Laser Irradiation on Dentin

OBJECTIVE

This study evaluated the molecular and morphological changes on dentin elements after Er:YAG laser irradiation.

BACKGROUND DATA

Spectroscopy studies reporting the effects of Er:YAG laser irradiation as an alternative to acid etching are needed to better understand the laser's effects.

METHODS

The occlusal one-third of the crown of six human third molars was removed. The dentin surface was schematically divided into areas corresponding to four surface treatment groups: control (group C): 37% phosphoric acid etching; group I: Er:YAG laser 80 mJ; group II: Er:YAG laser 120 mJ; and group III: Er:YAG laser 180 mJ. The analysis was performed by scanning electron microscopy (SEM) and Fourier transform Raman spectroscopy (FT-Raman) before and after the treatments. Raman data were submitted to ANOVA and Bonferroni tests.

RESULTS

The SEM photomicrographs revealed open dentin tubules in the control group. The molars from groups I, II, and III showed partially open dentin tubules. SEM images showed that the laser-irradiated dentin surface was not favorable to the diffusion of monomers. A significant reduction of the spectra relative intensity was observed in group III specimens.

CONCLUSIONS

Er:YAG laser irradiation with 180 mJ could produce chemical changes in proteins, phosphate, and carbonate in dentin.

Nd:YAG laser influence on microtensile bond strength of different adhesive systems for human dentin

OBJECTIVE

The purpose of this study was to investigate the influence of Nd:YAG on microtensile bond strength (microTBS) of different adhesive systems for human dentin.

BACKGROUND DATA

Lasers have been widely used in dentistry. New adhesive systems with different chemical compositions are introduced every year, and it is important to investigate the bonding of new adhesive systems to dentin irradiated with laser.

METHODS

The occlusal surfaces of third molars were removed to obtain flat dentin surfaces. The teeth were randomly divided into six groups. Each adhesive system was applied, according to manufacturers' instructions, to surface dentine with and without Nd:YAG laser irradiation (0.9 W, 15 Hz, 60 mJ per pulse). A block of composite resin was built over the adhesive layer. The specimens were sectioned to obtain 0.70 x 0.70 mm of transversal section. Twenty test specimens were selected for each group, and were then submitted to microTBS on a universal testing machine.

RESULTS

According to Student's t-test, for Single Bond, there was no statistically significant difference without (49.32 MPa) and with (47.34 MPa) laser application (p = 0.60). For the Tyrian SPE/One Step Plus, microTBS value with laser (27.09 MPa) was statistically higher than without laser (19.13 MPa), as well as for Adper Prompt L-Pop (22.85 and 13.78 Mpa; p < or = 0.01).

CONCLUSION

The application of Nd:YAG laser to dentin provided an increase in the bond strength values for the Tyrian SPE/One Step Plus and Adper Prompt L-Pop adhesive systems, but did not influence the bond strength values of the Single Bond adhesive system.

Effects of Treatment for Manipulation of Teeth and Er:YAG Laser Irradiation on Dentin: A Raman Spectroscopy Analysis

OBJECTIVE

The main purpose of this study was to evaluate the utility of Raman spectroscopy analysis as a research tool to study the effects of Er:YAG laser etching on dentin mineral and organic components. A secondary aim was to study the effects of the decontamination process and the storage procedure on dentin components.

BACKGROUND DATA

There are no spectroscopy reports relating the effects of Er:YAG laser irradiation as an alternative to acid etching and the manipulation process on the dentin structure.

METHODS

Twelve non-carious human third molars were divided in two main groups: stored in thymol solution (group A, n = 6) or autoclaved (group B, n = 6). The specimens were either etched with 37% phosphoric acid (control subgroup) or irradiated with Er:YAG laser. Irradiated samples were divided into the following subgroups: I, II, and III (80 mJ, 3 Hz, 30 sec; 120 mJ, 3 Hz, 30 sec; and 180 mJ, 3 Hz, 30 sec, respectively). Samples were analyzed by Raman spectroscopy.

RESULTS

The mineral and organic dentin contents were more affected in autoclaved teeth than in the specimens stored in thymol. Peak area reduction in group A specimens treated with phosphoric acid and pulse energy of 80 mJ were the most conservative surface treatments regarding changes in the peak area of organic and inorganic dentin components.

CONCLUSION

The autoclaving process and pulse energies of 120 and 180 mJ produced greater reduction of organic and inorganic contents in dentin, associated with greater reduction in the areas of 968, 1077, 1460, and 1670 cm(1) Raman peaks.

Influence of Nd:YAG laser irradiation on an adhesive restorative procedure

Hard tissue modification by means of laser irradiation is becoming popular in dentistry, since it promotes assorted responses between the tooth and the restorative material. Some studies on the bond strength of adhesive systems to Nd:YAG irradiated teeth have shown distinctive behaviors when irradiation was applied before or after the adhesive agent. This study evaluated the microtensile bond strength of a commercial adhesive system to dentin irradiated with Nd:YAG laser after adhesive application but prior to polymerization. The experiment was conducted in vitro, using freshly extracted human teeth as samples. For the microtensile test, the teeth were separated into 4 different groups according to the energy density of laser irradiation: 0, 5, 10 and 50 J/cm2. The data was analyzed with analysis of variance (ANOVA) and LSD tests, and the results indicated that the group that was irradiated with 5 J/cm2 had significantly higher bond strength values. Adhesive penetration on the etched dentin was observed by scanning electron microscopy, where the images showed better adhesive penetration on dentinal tubules after dentin irradiation with 5 J/cm2. Based on the results of this study, it is possible to conclude that irradiation of dentin with the Nd:YAG laser at low energy densities after application of the adhesive but prior to polymerization might be positive for the adhesive restorative process.

Influence of Er:YAG laser surface treatment and primer application methods on microtensile bond strength self-etching systems

OBJECTIVE

The aim of this in vitro study was to evaluate how surface preparation and primer application technique can influence the microtensile bond strength of self-etching system.

BACKGROUND DATA

One of the possible applications of dental lasers includes increasing the quality of bond strength.

MATERIALS AND METHODS

12 extracted, sound human molars were ground flat to expose occlusal dentin and were then divided into six groups (G1-G6)(n = 30-36) according to surface preparation and primer application (active or passive): G1-diamond bur (DB) + active primer (AP); G2-DB + passive primer (PP); G3-Er:YAG laser (EL) + AP; G4-EL + PP; G5-#600-grit paper disc (PD) + AP; G6-PD + PP. After adhesive procedure, 5-mm high composite buildups were created with Z 250. After storage in water at 37 degrees C for 24 h, teeth were vertically sectioned into serial 1- mm2 sticks. Samples were tested for tension in an Instron machine at 0.5 mm/min. Nine additional molars were prepared to morphological analysis. Regular grit diamond bur, Er:YAG laser, or #600-grit SiC paper was used for SEM observations of dentin surfaces of each group before and after treatment with self-etching primers. Microtensile data were submitted to statistical analysis.

RESULTS

G1-43.85 +/- 9.60 MPa; G2-24.28 +/- 8.90 MPa; G3-24.11 +/- 4.05 MPa; G4-23.30 +/- 4.21 MPa; G5-55.64 +/- 8.50 MPa; G6-56.45 +/- 12.05 MPa.

CONCLUSIONS

(1) Er:YAG laser and diamond burs are able to create distinct smear layers; however the resistance of dentin/adhesive interface is similar. In this way, we can use both instruments clinically without diminishing bond strength; (2) the #600-grit sandpaper disc least affects resistance and is highly recommended for in vitro studies to achieve standard preparation of dentinal surface; (3) active primer application is the method most recommended, despite the type of dentin preparation instrument used.

Microtensile Bond Strength Analysis of Different Adhesive Systems and Dentin Prepared with High-Speed and Er:YAG Laser: A Comparative Study

OBJECTIVE

The aim of this study was to evaluate the bond strength of two adhesive systems (Single Bond and Clearfil SE Bond) subjected or not to a thermocycling procedure and applied to cavities prepared either with high-speed diamond bur or Er:YAG laser.

BACKGROUND DATA

One of the possible applications of dental lasers includes increasing the quality of bond strength.

METHODS

This in vitro study was carried out using a microtensile test on 16 bovine teeth, divided into eight groups. Cavities were prepared on superficial dentin of the medium portion of the buccal surface. After application of adhesive systems, composite restorations were performed at 5-mm height. After 24 h, four groups of teeth were immersed in water, and the other four were thermocycled. Bonded specimens were sectioned into serial 1x1-mm beams, which were subjected to a microtensile test. Final values of bond strength were measured, expressed in MPa, and statistically analyzed.

RESULTS

Results were as follows: G1 (26.281 +/- 5.454 MPa); G2 (10.965 +/- 3.714 MPa); G3 (18.549 +/- 6.113 MPa); G4 (14.295 +/- 3.806 MPa); G5 (18.225 +/- 5.701 MPa); G6 (5.588 +/- 2.211 MPa); G7 (18.256 +/- 3.819 MPa); and G8 (15.423 +/- 4.714 MPa).

CONCLUSIONS

Self-etching adhesive system (SE) produced more stable bond strength results than the system that indicates total etching (SB). For dentin prepared at high speed, the total etching adhesive system was more indicated, whereas Er:YAG laser-preparation dentin was not influenced by the adhesive system. The thermocycling procedure could negatively affect microtensile bond strength of both adhesive systems, being more deleterious to SB than to SE.