Dentin Bond Strength: Influence of Laser Irradiation, Acid Etching, and Hypermineralization

In-Vitro Evaluation of Dental Adhesive Bond Strength With Diode Laser Irradiation Before Photopolymerization

AIM

In-vitro evaluation of shear bond strength, mode of failure, and adaptation of fifth-generation (etch-and-rinse), seventh-generation,and eighth-generation self-etch dental adhesives to human dentin with or without diode-laser irradiation before photopolymerization.

MATERIALS AND METHODS

Seventy-two extracted human maxillary premolar teeth were collected. The buccal and lingual surfaces of teeth were grounded until dentin was exposed. Test areas of 4 mm diameter were created on both surfaces of teeth to standardize the area of treatment. The samples were then randomly allocated into three groups (n = 24): Group 1 Adper Single Bond 2 Etch-and-Rinse; Group 2 Tetric-N-Bond Universal Self-Etch; Group 3 Prime and Bond Universal Self-Etch dental adhesives were used. Buccal surfaces (sub-groups 'a') of all specimens were irradiated with diode laser before photopolymerization of the adhesive material, and palatal surfaces (sub-groups 'b') were directly photopolymerized without prior diode laser irradiation and restored with composite resin. All specimens were thermocycled. Four specimens from each group were then subjected to scanning electron microscopy (SEM) analysis to examine the adaptation of adhesive to dentin, and the remaining 60 specimens were evaluated for shear bond strength tests, modes of failure at the adhesive-dentin interface, and values were recorded, tabulated, and used for data analysis. A one-way ANOVA test and the Student's t-test were used for statistical analysis. A P value ≤ 0.05 was considered statistically significant.

RESULTS

The mean shear bond strength for the groups was: Group 1a (13.96 MPa), 1b (14.95 MPa); Group 2a (10.06 MPa), 2b (10.30 MPa); Group 3a (12.03 MPa), and 3b (10.44 MPa). No statistically significant difference was seen among sub-groups 1a and 3a, 2a and 3a, 2b and 3b as P > 0.05. A significant difference was seen among sub-groups 1b and 3b (P<0.05), 1a and 2a, and 1b and 2b (P<0.01).

CONCLUSION

Adper Single Bond 2 without diode-laser irradiation before photopolymerization showed the highest shear bond strength, followed by Adper Single Bond 2 irradiated with diode laser before photopolymerization, with the maximum adaptation of dental adhesive to dentin compared to other adhesives used either with or without diode-laser irradiation.

In vitro studies the influence of Nd: YAG laser on dental enamels

The present work aimed at assessing chemical, topographical, and morphological changes induced by Nd : YAG laser treatment of dental enamels by means of energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). Fifteen human enamel specimens were obtained, three of samples were kept untreated as a control while the others twelve samples were equally divided into four groups where each group have a three samples according to treating approach as: G1:(untreated);G2: (treated with Nd:YAG laser, 100 mJ/pulse,10 Hz/1064nm); G3(treated with Nd:YAG laser, 500 mJ/pulse, 10 Hz/1064nm); G4(treated with Nd:YAG laser 1000 mJ/pulse, 10 Hz/1064nm), and finally G5(treated with Nd:YAG laser, 1000 mJ/pulse, 10 Hz/532nm) respectively. Beside many craters and cracks, the AFM results showed fractures with depths of 19.23 nm, 174.7 nm, 216.9 nm, 207.4 nm and 156.5 nm and width of 559.2 nm, 833.4 nm, 1115 nm, 695.0 nm, and 5142 nm for all Groups respectively. The highest surface roughness was found in G5 with 111.4 nm while the lowest surface roughness was found in G1 to be 14.3 nm. The inside surface of the fissures was also rough. The SEM micrographs revealed modifications to the morphology. EDS was used to measure the phosphorous (P), calcium (Ca), oxygen (O), and carbon (C) percentages presented in crater areas and their surroundings, Ca, P, O, and C levels were observed to vary significantly at the crater and its rim, a lower percentage of C wt% were realized corresponding to laser treatment of 1000 mJ/Pulse laser energy. However, it was not feasible to recognize a specific chemical arrangement in the craters. It is also concluded that the higher depth and particular edge of ablated part when teeth were irradiated by laser with 1000 mJ/10Hz/1064nm.

Shear-bond strength of different Self-Etching adhesive systems to dentin with or without laser irradiation before photopolymerization (A comparative Study)

This study aimed at comparing shear-bond strength (SBS) of different self-etching adhesive systems (Clearfil S³ Bond Plus, G-Premio BOND and IBond) to dentin without or with diode-laser irradiation before photo-polymerization and to determine the effect of storage and thermo-cycling on SBS of adhesive systems.

METHODS

The buccal surface of 84 extracted maxillary premolars was grounded to create flat surface. The specimens were allocated into 3 groups (n = 28) depending upon the adhesive systems, then each group was divided into two sub-group (I, II) (n = 14). After the placement of respective adhesive systems on the flat surface, adhesive system in group I was photo-polymerized immediately, while in group II, the adhesive systems were exposed to diode-laser before photo-polymerization. Composite cylinder (4 mm in diameter and 2 mm height) was built on the flat surface of each specimen. Then group I and II were divided into two sub-groups (n = 7) according to the storage time and thermo-cycling (1 day without thermo-cycling or 72 days with thermo-cycling) then all the specimens were stored in distilled water. The SBS was measured at the end of storage period. ANOVA, Duncan's Multiple Range Test and independent t-test "P ≤ 0.05" were used for data analysis.

RESULTS

G-premio BOND showed the highest mean value of SBS followed by Clearfil S³ Bond plus without significant difference between them, while IBond revealed the least mean value. Laser irradiation had positive effect on the bond-strength of all tested adhesive systems. The results also showed that the storage with thermo-cycling had negative effect on the bond-strength in groups without laser irradiation for all tested adhesive systems, while for groups with laser irradiation, the reduction in the bond-strength of all tested adhesive systems was not significant.

CONCLUSION

Diode-laser application prior to photo-polymerization of self-etch adhesive systems significantly increased the bond-strength to dentin and can increase the durability of composite adhesion.

MDP-based universal adhesive system irradiated with Er,CR:YSGG: Analysis of its performance up to 6 months

This study aimed to analyze the interaction of a MDP-based universal dentin bonding system (DBS) with Er, Cr: YSGG laser irradiation, measuring the microtensile bond strength to dentin over a six-month period. The experimental design involved three factors: DBS (Adper Scotchbond Universal; Clearfil SE Bond, Adper Scotchbond Multipurpose and Adper Single Bond 2), laser (Control and Er, Cr: YSGG), and time (initial- 7 days and 6 months). Eighty dentin samples from molars were prepared (n=10) with laser irradiation after primer and DBS application. After 7 days, were subjected to micro tensile bond strength test. The data were analyzed by three-way ANOVA and Tukey tests (p<0.05). Both DBS and laser significantly affected the bonding performance and their interaction was statistically significant (p=0.0194). The self-etching mode of the MDP-based universal DBS maintained the bond strength on dentin irradiated with ER, Cr: YSGG after 6 months, while bonding with all other DBS deteriorated.

Effects of calcium-phosphate, laser and adhesive on dentin permeability and bond strength

Objectives

The present study examined a technique for reducing dentin permeability through the application of a calcium phosphate (CaP)-based desensitiser with a laser-assisted process and evaluated adhesive-dentin bond strength. Methods: Thirty dentin discs were divided into two groups according to whether the selected desensitiser (TeethMate; Kuraray Noritake) was used prior to dentin bonding. Each group was subdivided into three subgroups (n = 5): A- Adhesive (Single Bond Universal, 3M ESPE), AL- Adhesive + Laser (Nd:YAG 60 mJ) and LAL- Laser + Adhesive + Laser. Dentin permeability values (%) were recorded before and after desensitiser application. Resin composites were placed over the bonded specimens; the latter were aged prior to microtensile bond strength evaluation. Gelatinolytic activity within the hybrid layers was examined with in-situ zymography using confocal laser scanning microscopy. Data were analysed with ANOVA and Tukey test (α = 0.05).

Results

Significant differences in dentin permeability were identified for all groups (p = 0.00). Both laser treatment (p = 0.182) and desensitiser application (p = 0.687) did not significantly improve dentin bond strength. Ultrastructure of the resin-dentin interface identified presence of calcium phosphate within dentinal tubules. Laser treatment did not affect hybrid layer ultrastructure. Both treatment modalities (intratubular CaP occlusion and laser) had no influence on gelatinolytic activity within hybrid layers.

Conclusion

Although intratubular CaP occlusion and laser treatment were effective in reducing dentin permeability, they did not affect bond strength, interfacial ultrastructure and gelatinolytic activity within hybrid layers.

Clinical relevance

Treatment of etched dentin with Nd:YAG Laser at 60 mJ does not adversely affect collagen ultrastructure and gelatinolytic activity within the hybrid layer. The application of a calcium phosphate-based desensitiser to etch dentin does not affect dentin bond strength.

Effect of Diode Laser (810 nm) Irradiation on Marginal Microleakage of Multi-mode Adhesive Resins in Class V Composite Restorations

Introduction: Some studies have shown that laser irradiation on unpolymerized adhesives can improve composite-dentin adhesion. The aim of the present study was to evaluate the effect of the diode laser (810 nm) on the microleakage of multi-mode adhesive systems at enamel and dentin margins of composite restorations. Methods: Classic class V boxes were prepared on 48 sound premolar teeth and randomly divided into 6 groups (n=16). In the control groups, Scotchbond Universal (SBC), G-Premio (GBC), and Ambar U (AMC) were used by a self-etch mode. In the test groups (SBL, GBL, ABL), the 810 nm diode laser was irradiated (1 W) for 10 seconds before the polymerization of the adhesive. The boxes were restored by the resin composite. After finishing and polishing, the samples were thermocycled (5°C to 55°C) for 1000 cycles and then immersed in 0.1% methylene blue dye (48 hours). Dye penetration through the gingival and occlusal margins was measured by Stereomicroscope. The data were analyzed at the 5% significance level using Kruskal-Wallis and Mann-Whitney U tests. Results: Significant differences were found between the control and test groups (P < 0.05). The occlusal margins of the SBL and GBL groups and the cervical margin of the SBL group exhibited the lowest microleakage (P < 0.05). The AM control group showed maximum microleakage at cervical and occlusal margins. Conclusion: The irradiation of the 810 nm diode laser on the unpolymerized universal adhesive systems in a self-etch mode caused a significant reduction in enamel and dentin marginal microleakage of composite restorations.

Micro-shear bond strength of adhesives with different degrees of acidity: Effect on sound and artificially hypermineralized dentin

This study evaluates the bond strength of four self-etching adhesive systems with different acidity levels in normal and artificially hypermineralized dentin substrate. Healthy human molars were divided into groups: normal dentin-N (n = 36) and artificially hypermineralized dentin-H (n = 36). Self-etching adhesive systems Clearfil S³ Bond (n = 9), Optibond All in One (n = 9), Clearfil SE Bond (n = 9), and Adhese (n = 9) were used for both the N and H groups. Transparent cylindrical matrices were positioned on the treated dentin surfaces, filled with composite resin, and light-cured for 40 s. After the transparent cylindrical matrices were removed, the specimens were stored for 24 hr in a humid environment at 37°C and were subjected to a micro-shear bond strength test. For each group, a specimen was prepared and evaluated in scanning electron microscope for adhesive interface observation. Normality was confirmed and the two-way analysis of variance and Games-Howell post-tests were conducted (α = .05). The data demonstrated an interaction between the adhesive system and type of dentin substrate (p < .01). For normal dentin, all adhesive systems assessed were adequate; however, in the hypermineralized dentin, the Clearfil SE Bond two-step self-etching adhesive system with mild pH presented the highest immediate bond strength. There was a predominance of adhesive failures for all adhesive systems in the different dentin substrates evaluated. It was concluded that the self-etching adhesive systems evaluated were efficient for both substrates, and for the hypermineralized dentin, the Clearfil SE Bond presented a higher bond strength value.

Effect of Er: YAG Laser on Microtensile Bond Strength of Bleached Dentin to Composite

Introduction: In non-vital tooth bleaching, dentin is in direct contact with the bleaching agent, 1 to 3-week delay is needed to eliminate free radicals from tooth structure. The present study aimed to evaluate the effect of irradiation of Er: YAG laser on immediate microtensile bond strength of bleached dentin to composite. Methods: Sixty sounds human teeth were collected and randomly divided into 4 groups (n=15): no bleaching (NB), opalescence endo hydrogen peroxide (HP) gel bleaching, sodium perborate (SP) bleaching and laser bleaching with heydent gel (LB). The groups were divided into 3 subgroups (n=5): no surface treatment, Er: YAG laser irradiation and 10% sodium ascorbate (SA). All samples were restored and underwent microtensile bond strength testing. Statistical analysis was carried out using one-way and two-way ANOVA. Results: Bond strength in NB-SA group had a significant difference with the NB group (P<0.05) while no significant difference was noted between NB and NB-Er groups (P=0.55). Application of SA and Er: YAG laser after bleaching with SP did not enhance the bond strength (P=0.07). Conclusion: Application of SA and Er: YAG laser after HP gel bleaching significantly enhanced the bond strength. Application of Er: YAG laser after internal bleaching with HP gel could enhance the bond strength.

Effect of diode laser irradiation on the bond strength of polymerized non-simplified adhesive systems after 12 months of water storage

Objectives:

The aim of this in vitro study was to evaluate the bonding strength of non-simplified dentin bonding systems (DBS) to dentin irradiated with a diode laser (970 nm) immediately and after 12 months of water storage following either primer or bond application.

Material and methods:

The experimental design included three different factors: DBS type [Adper^TM Scotchbond Multipurpose (MP) and Clearfil™ SE Bond (CSE)], irradiation [without irradiation - control (C), irradiation after primer application (AP), and irradiation after bond application (AB)], and time [initial (I) and after 12 months of water storage (12 m)]. Sixty sound human third molars (n = 10) were obtained, and their flat occlusal dentin areas were prepared and standardized. Laser irradiation was performed in the contact mode perpendicular to the dental surface over an automatically selected scanning area at a pulse energy of 0.8 W, frequency of 10 Hz, and energy density of 66.67 J/cm². After 7 days of treatment, the specimens were cut, and half of them were subjected to microtensile testing (500 N/0.05 mm/min), whereas the remaining sticks were examined after 12 months of water storage. The obtained data were analyzed by three-way analysis of variance (ANOVA) followed by a Tukey test (p<0.05). The observed fracture modes were investigated using a portable digital microscope with a magnification of 40x.

Results:

Among the utilized DBS, MP generally exhibited higher bond strengths, but did not always differ from CSE under similar conditions. The irradiation factor was statistically significant only for the MP/AB groups. After 12 months of storage, all groups demonstrated a significant reduction in the bond strength, whereas the results of fracture analysis showed a predominance of the adhesive type.

Conclusions:

The laser treatment of non-simplified DBS was not able to stabilize their bonding characteristics after 12 months.

Does laser diode irradiation improve the degree of conversion of simplified dentin bonding systems?

Simplified dentin-bonding systems are clinically employed for most adhesive procedures, and they are prone to hydrolytic degradation.

Protective Effect of Adhesive Systems associated with Neodymium-doped Yttrium Aluminum Garnet Laser on Enamel Erosive/Abrasive Wear

AIM

This study evaluated the efficacy of self-etching adhesive systems associated or not associated with the neodymium-doped yttrium aluminum garnet (Nd:YAG) laser on the protection against enamel erosive/abrasive wear.

MATERIALS AND METHODS

Bovine enamel specimens were demineralized with 0.3% citric acid (5 minutes). The samples were randomly assigned to eight groups (n = 20): SB - Single Bond Universal (3M/ESPE); SB+L - Single Bond Universal + laser (80 mJ/10 Hz); FB - Futurabond U (Voco); FB+L -Futurabond U + laser; GEN - G-aenial bond (GC); GEN+L -G-aenial bond + laser; L - laser irradiation; and C - no treatment. The laser was applied before light curing. The samples were subjected to erosive/abrasive challenges (0.3% citric acid - 2 minutes and tooth brushing four times daily for 5 days). Enamel surface loss was recovered profilometrically by comparison of baseline and final profiles. The adhesive layer thickness, retention percentage of the protective layer, and microhardness of cured adhesive were measured. Data were analyzed using one-way analysis of variance and Tukey's test (5%).

RESULTS

There were significant differences for all parameters (p = 0.0001). Mean values ± SD and results of the Tukey's test were: Surface wear: GEN - 4.88 (±1.09)a, L - 5.04 ± 0.99)a, FB - 5.32 (±0.93)ab, GEN + L - 5.46 (±1.27)abc, SB + L - 5.78 (±1.12)abc, FB + L - 6.23 (±1.25)bc, SB - 6.35 (±1.11)c, and C - 6.46 (±0.61)c; layer thickness: GEN - 15.2 (±8.63)c, FB - 5.06 (±1.96)a, GEN + L - 13.96 (±7.07)bc, SB + L - 4.24 (±2.68)a, FB + L - 9.03 (±13.02)abc, and SB - 7.49 (±2.80)ab; retention: GEN - 68.89 (±20.62)c, FB - 54.53 (±24.80)abc, GEN + L - 59.90 (±19.79)abc, SB + L - 63.37 (±19.30)bc, FB + L - 42.23 (±17.68) a, and SB - 47.78 (±18.29)ab; microhardness: GEN - 9.27 (±1.75)c; FB - 6.99 (±0.89)b; GEN + L - 6.22 (±0.87)ab; SB + L - 15.48 (±2.51)d; FB + L - 10.67 (±1.58)c; SB - 5.00 (±1.60)a.

CONCLUSION

The application of Futurabond U and G-aenial bond on enamel surface, as well as the Nd:YAG laser irradiation alone, was able to reduce the enamel wear. The use of laser after the adhesive systems did not improve their efficacy.

CLINICAL SIGNIFICANCE

Erosive/abrasive wear is a prevalent condition in clinical practice affecting many patients. The association of adhesive systems and Nd:YAG laser is of considerable clinical interest because it assesses new treatments to reduce the erosive/abrasive wear that would help dentists in clinical treatment decisions to reduce enamel wear and achieve a successful treatment.

Comparative Evaluation of Effects of Laser Modalities on Shear Bond Strengths of Veneering Porcelains to Laser Sintered Substructures: An In Vitro Study

OBJECTIVE

Laser modalities and direct metal laser sintering (DMLS) have a potential to enhance micromechanical bonding between dental super- and infrastructures. However, the effect of different manufacturing methods on the metal-ceramic bond strength needs further evaluation. We investigated the effect of surface treatment with Er:YAG, Nd:YAG, and Ho:YAG lasers on the shear bond strength (SBS) of high-fusion dental porcelains (Vita and G-Ceram) to infrastructures prepared with DMLS in vitro settings.

MATERIALS AND METHODS

Study specimens (n = 128) were randomly divided into study subsets (n = 8), considering treatment types applied on the surface of infrastructures, including sandblasting and selected laser modalities; infrastructure types as direct laser sintered (DLS) and Ni-Cr based; and superstructure porcelains as Vita and G-Ceram. The SBS test was performed to assess the effectiveness of surface modifications that were also examined with a stereo microscope.

RESULTS

Considering laser procedure types, the highest SBS values were obtained by Er:YAG laser, followed by, with a decreasing efficiency, Ho:YAG laser and sandblasting procedures, and Nd:YAG laser procedure (p < 0.05). Nd:YAG laser decreases the bonding of Vita and G-Ceram in all the infrastructures compared with sandblasting. Considering porcelains, the highest SBS values were obtained by Vita (p < 0.05). Considering infrastructures, the highest SBS values were obtained by DMLS procedure (p < 0.05). The laser procedures caused surface irregularities as revealed by the stereo microscopic examination.

CONCLUSIONS

In current experimental settings, Er:YAG laser applied to DLS infrastructure veneered with Vita porcelain increases bonding strength more distinctly, and Nd:YAG laser applied to Ni-Cr-based infrastructure veneered with G-Ceram porcelain alters bonding strength unfavorably.

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.

Effect of CO2, Nd:YAG and Er:YAG Lasers on Microtensile Bond Strength of Composite to Bleached-Enamel

Background:

Tooth restoration immediately after bleaching is challenging due to the potential problems in achieving adequate bond strength.

Objective:

The aim of this study was to evaluate the effect of surface treatment with ER:YAG, ND:YAG, CO₂ lasers and 10% sodium ascorbate solution on immediate microtensile bond strength of composite resin to recently bleached enamel.

Materials & Methods:

Ninety sound molar teeth were randomly divided into three main groups (n:30) : NB (without bleaching), HB (bleached with 38% carbamide peroxide) and OB (bleached with Heydent bleaching gel assisted by diode laser). Each group was divided into five subgroups (n:6) : Si (without surface treatment), Er (Er:YAG laser), CO₂ (CO₂ laser), Nd (Nd:YAG laser) and As (Immersion in 10% sodium ascorbate solution). The bonding system was then applied and composite build-ups were constructed. The teeth were sectioned by low speed saw to obtain enamel- resin sticks and submitted to microtensile bond testing. Statistical analyses were done using two- way ANOVA, Tukey and Tamhane tests.

Results:

µTBS of bleached teeth irradiated with ND:YAG laser was not significantly different from NB-Nd group. Microtensile bond strength of OB-Er group was higher than NB-Er and HB-Er groups. The mean µTBS of HB-CO₂ group was higher than NB-CO₂ group; the average µTBS of HB-As and OB-As groups was also higher than NB-As group.

Conclusion:

Use of Nd:YAG, CO₂ lasers and 10% sodium ascorbate solution could improve the bond strength in home-bleached specimens. Application of ND:YAG laser on nonbleached specimens and Er:YAG laser on office-bleached specimens led to the highest µTBS in comparison to other surface treatments in each main group.

Longitudinal Evaluation of Bond Strength to Enamel of Dental Adhesive Systems Associated with Nd:YAG Laser

OBJECTIVES

This study evaluated the durability of bond strength to enamel using total-etch (Single Bond/SB) and self-etch (Clearfil SE Bond/CSEB) adhesives associated with neodymium:yttrium-aluminu-garnet (Nd:YAG) laser irradiation through the uncured adhesives.

METHODS

Bovine incisors were worn to expose an area of enamel and were divided into four groups: group 1 (control) SB + polymerization; group 2 (control) CSEB + polymerization; group 3 (laser) - SB + Nd:YAG laser (174.16 J/cm(2)) + polymerization; and group 4 (laser) CSEB + Nd:YAG (174.16 J/cm(2)) + polymerization. Blocks of composite were fabricated and stored for 24 hours or 12 months, sectioned into beams, and submitted to microtensile tests. Results were analyzed by three-way analysis of variance (ANOVA) (adhesive, technique, and storage time) and Tukey tests.

RESULTS

ANOVA revealed significant differences for adhesive × technique and technique × storage time (p<0.05). The mean values (MPa) for interaction adhesive × technique (standard deviation) were as follows: SB/control = 35.78 (6.04)a; SB/laser = 26.40 (7.25)b, CSEB/control = 26.32 (5.71)b, CSEB/laser = 23.90 (7.49)b. For interaction technique × storage time the mean values were as follows: control/24 hours = 32.58 (6.49)a; control/12 months = 29.52 (8.38)a; laser/24 hours = 29.37 (5.71)a; laser/12 months = 20.92 (6.5)b. Groups with the same letters showed no statistically significant differences.

CONCLUSION

Scanning electron microscope analysis showed evident areas of micromorphological alterations in lased samples after 12 months of water storage. Nd:YAG laser irradiation of enamel through unpolymerized total-etch adhesive significantly reduced bond strength compared with the control. Bond strength decreased when enamel samples irradiated with Nd:YAG laser through unpolymerized adhesives were stored in water for 12 months.

Diode laser irradiation increases microtensile bond strength of dentin

Laser irradiation after the immediate application of dentin bonding systems (DBSs) and prior to their polymerization has been proposed to increase bond strength. The objective of this study was to evaluate the effect of diode laser irradiation (λ = 970 nm) on simplified DBSs through microtensile bond strength tests. Forty healthy human molars were randomly distributed among four groups (n = 10) according to DBSs used [Adper™ SingleBond 2 (SB) and Adper™ EasyOne (EO)], and the respective groups were irradiated with a diode laser (SB-L and EO-L). After bonding procedures and composite resin build-ups, teeth were stored in deionized water for 7 days and then sectioned to obtain stick-shaped specimens (1.0 mm2). The microtensile test was performed at 0.5 mm/min, yielding bond strength values in MPa, which were evaluated by two-way ANOVA followed by Tukey's test (p < 0.05) for individual comparisons. For both adhesive systems, diode laser irradiation promoted significant increases in bond strength values (SB: 33.49 ± 6.77; SB-L: 43.69 ± 8.15; EO: 19.67 ± 5.86; EO-L: 29.87 ± 6.98). These results suggest that diode laser irradiation is a promising technique for achieving better performance of adhesive systems on dentin.

Comparison of different dentin pretreatment protocols on the bond strength of glass fiber post using self-etching adhesive

INTRODUCTION

This study compared the influence of different irrigants with and without ultrasound or laser irradiation on the bond strength of glass fiber posts using a self-etching adhesive in a supplementary dentin pretreatment.

METHODS

Ninety bovine incisor roots were divided into 3 groups according to the irrigant tested: 2% chlorhexidine (CHX) (n = 30); 2.5% sodium hypochlorite (NaOCl) (n = 30), and saline solution (control) (n = 30). Each group was randomly divided into 3 subgroups according to the supplementary dentin pretreatment: ultrasound, Nd:YAG laser, and nonsupplemented (control). A self-etching adhesive system (Futurabond DC; VOCO GmbH, Cuxhaven, Germany) was used, and the glass fiber posts were cemented with dual-cure epoxy-based luting agent (Bifix QM, VOCO GmbH). All roots were sectioned transversely, and the push-out test was performed. Failure mode analysis was also evaluated.

RESULTS

Bond strength decreased significantly after the use of 2.5% NaOCl in all root thirds (P < .05). CHX showed no difference in the mean bond strength value compared with saline solution (P > .05). The supplementary dentin pretreatment using the Nd:YAG laser or ultrasound did not improve the bond strength values for both NaOCl and CHX (P > .05). Moreover, the apical third exhibited the lowest mean bond strength values (P < .05). Analysis indicated that the predominant failure mode was the mixed type.

CONCLUSIONS

Regardless of the irrigant used, the supplementary dentin pretreatment with ultrasound or laser irradiation showed no improvement in bond strength. Also, the use of NaOCl decreased the bond strength of glass fiber posts using a self-etching adhesive system, whereas CHX preserved it.

Grander system: a new technology to reduce surface tension of adhesive systems in dentistry

BACKGROUND

Reduced surface tension of liquids results in higher surface wetting ability and diffusivity by the substrate.

OBJECTIVES

The objective of this study was to evaluate the influence of the Grander Technology in reducing the surface tension of adhesive systems.

METHODS

Two adhesive systems (self-etch and total-etch) were modified by physical contact with the Grander system Flexible unit to revitalize water, for 48 h. Surface tension of adhesive systems and water in normal and grander-modified conditions was measured with a goniometer.

RESULTS

The results showed a reduction of surface tension for all conditions grander-modified between 3-15%.

CONCLUSIONS

Grander Technology was effective in reducing the surface tension of the Single Bond and Clearfil SE Bond adhesive systems. Clinical significance. Grander technology was employed to restructure the molecular structure of water-based adhesive systems, which can increase their wetness capacity and therefore ensure a greater diffusibility.

Influence of Nd:YAG laser on the bond strength of self-etching and conventional adhesive systems to dental hard tissues

PURPOSE

The aim of this study was to investigate the influence of Nd:YAG laser on the shear bond strength to enamel and dentin of total and self-etch adhesives when the laser was applied over the adhesives, before they were photopolymerized, in an attempt to create a new bonding layer by dentin-adhesive melting.

MATERIAL AND METHODS

One-hundred twenty bovine incisors were ground to obtain flat surfaces. Specimens were divided into two substrate groups (n=60): substrate E (enamel) and substrate D (dentin). Each substrate group was subdivided into four groups (n=15), according to the surface treatment accomplished: X (Xeno III self-etching adhesive, control), XL (Xeno III + laser Nd:YAG irradiation at 140 mJ/10 Hz for 60 seconds + photopolymerization, experimental), S (acid etching + Single Bond conventional adhesive, Control), and SL (acid etching + Single Bond + laser Nd:YAG at 140 mJ/10 Hz for 60 seconds + photopolymerization, experimental). The bonding area was delimited with 3-mm-diameter adhesive tape for the bonding procedures. Cylinders of composite were fabricated on the bonding area using a Teflon matrix. The teeth were stored in water at 37°C/48 h and submitted to shear testing at a crosshead speed of 0.5 mm/min in a universal testing machine. Results were analyzed with three-way analysis of variance (ANOVA; substrate, adhesive, and treatment) and Tukey tests (α=0.05). ANOVA revealed significant differences for the substrate, adhesive system, and type of treatment: lased or unlased (p<0.05). The mean shear bond strength values (MPa) for the enamel groups were X=20.2 ± 5.61, XL=23.6 ± 4.92, S=20.8 ± 4.55, SL=22.1 ± 5.14 and for the dentin groups were X=14.1 ± 7.51, XL=22.2 ± 6.45, S=11.2 ± 5.77, SL=15.9 ± 3.61. For dentin, Xeno III self-etch adhesive showed significantly higher shear bond strength compared with Single Bond total-etch adhesive; Nd:YAG laser irradiation showed significantly higher shear bond strength compared with control (unlased).

CONCLUSION

Nd:YAG laser application prior to photopolymerization of adhesive systems significantly increased the bond strength to dentin.

Influence of femtosecond laser treatment on shear bond strength of composite resin bonding to human dentin under simulated pulpal pressure

This in vitro study evaluated the influence of femtosecond laser (fs-laser)-generated patterns on shear bond strength (SBS) of composite resin bonded to human dentin under simulated pulpal pressure. Laser treatment was used to produce two different patterns on dentin surfaces. Three test groups and a control group without laser treatment under pulpal pressure were investigated. Dentin discs of 800 nm thickness were cut from 60 extracted caries-free human molars. Using a perfusion machine, the discs were exposed to Ringer solution on their basal surfaces. Clearfil SE Bond/Herculite XRV system was used. The samples were stored in distilled water and thermocycled. Bonding failures caused by a test set-up to challenge SBS were analyzed by scanning electron microscope (SEM). An 80 μm-sized cube-shaped pattern caused more cohesive failures in dentin or resin compared with the 160 μm-sized cube-shaped pattern. Weibull statistics demonstrated a significant difference between the two laser patterns, but only the test group with small-sized laser pattern was significantly different from the control group. The Weibull moduli ranged from 4.3 to 9.6 (control group). The 160 μm-sized pattern enhanced the bonding quality and avoided dentin weakening. It was concluded that fs-laser treatment in a 160 μm-sized cube-shaped pattern enabled a simplified bonding procedure by dispensing the primer without affecting SBS, compared with the control group.

Effect of different disinfectant methods on the initial microtensile bond strength of a self-etch adhesive to dentin

The aim of this in vitro study was to evaluate the effect of different disinfection methods on the initial microtensile bond strength of a two-step, self-etch adhesive to dentin. Twenty mandibular molars were sectioned parallel to the occlusal plane to expose the mid-coronal dentin. All of the teeth were divided into four groups (n = 5 per group): (1) in group OZ, the dentin surfaces were exposed to ozone gas from the Ozonytron X delivery system (OzonyTron X-Bioozonix, Munich, Germany), (2) in group ND, the dentin surfaces were irradiated with an Nd:YAG laser (Pulsmaster 600 IQ, American Dental Technologies, U.S.), (3) in group CHX, the dentin surfaces were treated with a 2% chlorhexidine solution, and (4) in the control group, no treatment was applied. In all of the groups, the teeth were restored with Clearfil SE Bond (Kuraray, Tokyo, Japan) and Clearfil Majesty Posterior (Kuraray, Tokyo, Japan), according to the manufacturer's instructions. The teeth were sectioned perpendicular to the bonded surface (surface area of approximately 1 mm(2)). Thus, six to seven specimens were obtained from each tooth, and a total of 34 specimens were analyzed in each group. The specimens were attached to the microtensile test machine (Micro Tensile Tester, T-61010 K, Bisco, U.S.). The data was analyzed using the one-way analysis of variance (ANOVA) and Tukey test (p < 0.05). Fracture modes of each specimen were determined using a stereomicroscope (SZ-PT Olympus, Tokyo, Japan) and a scanning electron microscope (SEM). The lowest bond strength occurred in the OZ group. Significant differences were determined only between group OZ and the other groups (group ND, group CHX, and control group) (p < 0.05). In conclusion, although ozone decreased the microtensile bond strength of the self-etch adhesive system to dentin, the Nd:YAG laser and 2% chlorhexidine did not change the microtensile bond strength so in context of the present study it would appear that the Nd:YAG laser and 2% chlorhexidine may be used as pre-restorative sterilization procedures on the dentin prior to the application of a two-step, self-etch adhesive.

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.

Marginal Leakage in Class V Cavities Pretreated with Different Laser Energy Densities

The purpose of the present study was to evaluate in vitro the degree of marginal leakage in Class V cavities involving the cementoenamel junction. Cavities were 4 mm wide and 2 mm deep. The specimens received dentin pretreatment (37% phosphoric acid) followed by the Single Bond (3M) adhesive system application. The 40 specimens were then divided into four groups: Group 1 (control); Group 2 (Nd:YAG laser at 120 mJ/pulse, frequency of 10 Hz, power of 1.2 W); Group 3 (Nd:YAG laser at 140 mJ/pulse, frequency of 10 Hz, power of 1.4 W); Group 4 (Nd:YAG laser at 160 mJ/pulse, frequency of 10 Hz, power of 1.6 W). The cavities were restored with Z100 composite resin (3M) and light cured at 300-600 mW/cm2 light intensity. Specimens were thermocycled to 500 cycles from 2-50 degrees C. After that, they were dried and sealed with nail varnish, respecting 1 mm around the restorations, and immersed in 0.5% methylene blue solution for 4 h. After this period, the teeth were rinsed, dried, sectioned, and analyzed in a stereoscopic loupe. The highest leakage scores were considered for each specimen. The results were statistically analyzed by the analysis of variance (ANOVA) - Kruskal-Wallis test to the 5% level. For both the enamel and cementum, there was a decrease in marginal leakage with the application of laser energy; no significant differences were observed for Groups 2, 3, and 4. The results also showed a smaller tendency to marginal leakage on the cementum than on the enamel.

Resin bonding to cervical sclerotic dentin: a review

Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentine are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention.

Nd:YAG Laser Influence on Microleakage of Class V Composite Restoration

OBJECTIVE

The purpose of this research was to evaluate the influence of the Nd:YAG laser on microleakage of class V composite restorations.

BACKGROUND DATA

There has been very little research that concerns microleakage resulting from the use of lasers and restorative materials.

MATERIALS AND METHODS

Thirty-six cavities were prepared and divided into three groups (n = 12) as follows: Group 1, control; Group 2, Nd:YAG laser irradiation before adhesive technique; Group 3, Nd:YAG laser irradiation after adhesive technique. Nd:YAG laser parameters were 320 micro m of fiberoptics; energy/pulse of 40 mJ of energy/pulse; repetition rate of 15 Hz; power of 0.6 W; pulsed and non-contact, 1 mm from the surface; 30 sec in scanning mode; energy density was 49,76 J/cm(2). Cavities were restored with microhybrid composite. After polishing, thermocycling and impermeabilization procedures were performed and specimens were submitted to a microleakage test, with complete immersion in aqueous solution of 50% silver nitrate for 8 h, in the total absence of light. After washing and drying, teeth were embedded to facilitate buccal-lingual vertical sectioning. Microleakage was revealed by light.

RESULTS

We used the Kruskal-Wallis test at a 5% level of confidence and observed no statistically significant difference among the tested groups.

CONCLUSION

It was possible to conclude that Nd:YAG laser does not influence marginal microleakage on composite restorations, independent of the moment the laser had been used.

Microleakage and nanoleakage: influence of laser in cavity preparation and dentin pretreatment

OBJECTIVE

The purpose of this study was to verify if the application of the Nd:YAG laser following pretreatment of dentin with adhesive systems that were not light cured in class V cavities and were prepared with Er:YAG laser would promote better sealing of the gingival margins when compared to cavities prepared the conventional way.

BACKGROUND DATA

Previous studies had shown that the pretreatment of dentin with laser irradiation after the application of an adhesive system is efficient in achieving higher shear bond and tensile bond strength.

MATERIALS AND METHODS

Er:YAG laser (Kavo-Key, Germany) with 350 mJ, 4 Hz, and 116.7 J/cm2 was used for cavity preparation. The conventional preparation was made with diamond bur mounted in high-speed turbine. Dentin treatment was accomplished using an Nd:YAG laser (Pulse Master 1000, ADT. USA) at 60 mJ, 10 Hz, and 74.65/cm2 following application of the adhesive system. The cavities were stored with Single Bond/Z100 and Prime & Bond NT/TPH. Eighty bovine incisors were used, and class V preparations were done at buccal and lingual surfaces divided into eight groups: (1) Er:YAG preparation + Prime & Bond NT + TPH; (2) Er:YAG preparation + Single Bond + Z100; (3) Er:YAG preparation + Single Bond + Nd:YAG + Z100; (4) Er:YAG preparation + Prime & Bond NT + Nd:YAG + TPH; (5) conventional preparation + Prime & Bond NT + TPH; (6) conventional preparation + Single Bond + Z100; (7) conventional preparation + Single Bond + Nd:YAG + Z100; (8) conventional preparation + Prime & Bond NT + Nd:YAG + TPH. All specimens were thermocycled for 300 full cycles between 5 degrees C+/-2 degrees C and 55 degrees C+/-2 degrees C (dwell time of 30 sec), and stored in 50% silver nitrate solution for 24 h soaked in photodeveloping solution and exposed to fluorescent light for 6 h. After this procedure, the specimens were sectioned longitudinally in 3 portions and the extension of microleakage at the gingival wall was determined following a criteria ranging from 0 to 4 using scanning electron microscopy (SEM). The medium portion sectioned of each specimen was polished and prepared for nanoleakage avaliation by SEM.

RESULTS

Kruskall-Wallis and Miller statistical tests determined that group 3 presented less microleakage and nanoleakage.

CONCLUSION

Application of the Nd:YAG laser following pretreatment of dentin with adhesive Single Bond non-photocured Single Bond adhesive in cavities prepared with Er:YAG promote better sealing of the gingival margins.

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

Since bonding systems were introduced in the restorative procedures carried out with esthetic materials, the treatment of dentin surfaces has been widely studied in order to establish the ideal technique. The application of 37% phosphoric acid on dentin is still the best known method. However, alternative methods for treating the dentin surface have been discussed in the literature, including the utilization of some kinds of laser irradiation. The purpose of this research was to morphologically evaluate the bond between adhesive materials and the dentin treated with Er:YAG and Nd:YAG lasers, in a comparative study by means of scanning electron microscopy (SEM). Irradiation either substituted acid etching, or was associated to it. Recently extracted bovine incisors were utilized. They received class V cavity preparations and were restored with a bonding system and a light-cured composite resin. Meanwhile, some of the teeth underwent irradiation with Er:YAG laser or Nd:YAG laser before the application of the bonding agent and the composite resin. The samples were selected, prepared for SEM and submitted to morphological analysis. Data were registered in photomicrographs. Based on the microscopic observations, we concluded that only in the dentin surfaces submitted to irradiation with Er:YAG laser and to acid conditioning there was penetration of resin into the dentine. With the Nd:YAG laser treatment, there was only visual superposition of resin over the dentin surface, which suggests that there was only occlusion of the tubules, with characteristics of fusion in the superficial dentine.

Nd:YAG laser influence on tensile bond strength of self-etching adhesive systems

OBJECTIVE

We evaluated the tensile bond strength of composite resin on enamel and dentine, treated with Nd:YAG laser before and after bonding procedures.

BACKGROUND DATA

The use of laser radiation in dentistry is being developed day by day. One of the possible applications of dental lasers includes increasing the quality of self-etching bonding systems.

METHODS

Forty-eight human teeth were used and separated into six groups: Group 1 (enamel control), Clearfil Liner Bond 2V (CLB 2V); group 2 (enamel), Nd:YAG + CLB 2V; group 3 (enamel), CLB 2V + Nd:YAG; group 4 (dentine control), CLB 2V; group 5 (dentine), Nd:YAG + CLB 2V; group 6 (dentine), CLB 2V + Nd:YAG. Tensile bond strength was performed.

RESULTS

Enamel means (15,54) were lower than dentine means (20,38). Bond strength of laser before (15,73) was lower than laser after (20,65). Interaction results G1 x G3; G2 x G3; G4 x G1; G2 x G5 were statistically significant.

CONCLUSIONS

Tensile bond strength of composites reached with self-etching adhesive systems were greater in dentine than in enamel. The best moment for application of Nd:YAG laser is after the use of adhesive system. Self-etching adhesive systems tested in this study can be used together with Nd:YAG laser without compromising to adhesion to dentine.