Effects of pulsed Nd:YAG laser on tensile bond strength and caries resistance of human enamel

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.

Influence of Laser and Ozone Pretreatment on the Shear Bond Strength of Fissure Sealants: An In Vitro Comparative Study

Aim:

To evaluate the shear bond strength (SBS) of 3 fissure sealants used alone and with ozone and laser pretreatment.

Materials and Methods:

For the SBS test, the flattened enamel surfaces of 90 healthy third molars were randomly divided into nine groups ( n  =  10 for each groups), based on different sealants (BeautiSealant, Fuji Triage, and Grandio Seal) and pretreatment conditions (no pretreatment, pretreatment with ozone, and pretreatment with neodymium-doped yttrium aluminum garnet [Nd:YAG laser]). Ozone was applied for 30 s in caries superficial mode, and Nd:YAG laser was applied for 60 s. After the pretreatment procedures, sealants were placed inside a mold on the enamel surface. SBS was measured with a universal testing machine. Data were analyzed using analysis of variance. Tukey’s multiple comparison tests were applied to determine the difference between the groups (α  = 0.05).

Results:

The lowest SBS was observed in the Fuji triage group. Nd:YAG laser and ozone did not affect the SBS of BeautiSealant. However, significant differences were determined in the Fuji triage and Grandio Seal groups after pretreatment procedures ( P  < .05).

Conclusion:

Ozone and laser can be employed to disinfect fissures before BeautiSealant application.

Morphological and Chemical Alterations of Root Surface after Er:YAG laser, Nd:YAG Laser Irradiation: A Scanning Electron Microscopic and Infrared Spectroscopy Study

Aims and Objectives

This study aimed to evaluate the efficacy of Nd:YAG and Er:YAG lasers in removing the smear layer and to study the morphological and chemical alterations of the root surface using scanning electron microscopy (SEM) and infrared (IR) spectroscopy.

Material and Methods

Fifty-five extracted upper incisor teeth were collected and 110 specimens of size 3 mm × 4 mm × 1 mm were prepared. For SEM evaluation, these samples were divided into six groups: A, B, and C. Group A comprised five samples that served as control. Groups B and C were further divided into five subgroups and each subgroup comprised five samples. All the specimens within the subgroups of B and C irradiated with 100, 200, 300, 400, and 500 mJ of Er:YAG laser and 211.66, 423.33, 635, 846.66, and 1058.33 J/cm² of Nd:YAG laser, respectively. The morphological changes of the laser-treated sites were observed qualitatively using an arbitrary scale under SEM. The data obtained were statistically analyzed by one-way analysis of variance (ANOVA) multiple range test by Turkey's honestly significant difference and Mann-Whitney U test. In chemical structural changes, Group D comprised five samples that served as nonirradiated control and Groups E and F were irradiated with the same aforementioned parameter and evaluated using Fourier-transform infrared spectroscopy.

Results

Er:YAG laser at 100 mJ effectively removed smear layer without any crater formation. The Nd:YAG laser removed the smear layer at the energy density of 211.66 J/cm² and 423.33J/cm². The energy density of 1058.33 J/cm² showed visible charring and deep crater with increased area of melted and resolidified minerals in SEM. In the chemical changes, IR spectroscopy graph showed the reduction in peak intensity beyond 846.66 J/cm² of and new absorption band was noticed (2010cm^-1 and 2017cm^-1) at samples treated with 846.66 and 1058.33 J/cm² of Nd:YAG laser.

Conclusion

Er:YAG laser at lower energy density effectively removed smear layer without production of toxic substance as compared with Nd:YAG laser. Thus, Er:YAG laser can be used as an effective root biomodification agent.

The lingual enamel morphology and bracket shear bond strength influenced by Nd:YAG laser and aluminum oxide sandblasting preconditioning

OBJECTIVES

This study aimed to investigate the influence of Nd:YAG laser and aluminum oxide sandblasting on the shear bond strength (SBS) of lingual brackets and to optically analyze the behavior of the enamel morphology.

MATERIALS AND METHODS

Thirty-five bovines' incisors teeth were divided into 5 groups (n = 7), according to the surface preconditioning: G1, control group; G2, Nd:YAG laser; G3, laser + aluminum oxide sandblasting (Al₂O₃); G4, Al₂O₃; and G5, Al₂O₃ + laser. All groups had lingual brackets bonded and shear debonded after 72 h. SBS values were analyzed, and the enamel morphology was evaluated by optical coherence tomography (OCT) and scanning electron microscope (SEM), before and after preconditioning surface. The optical attenuation coefficient (α) analysis was obtained from OCT images. Data analysis used the ANOVA test, followed by post hoc Tukey, Kruskal Wallis, and post hoc Dunn tests (significance of 5%).

RESULTS

The SBS values presented similarly among groups, but the value of α showed statistical difference (p-value = 0.0124) between G3 and G5 with the others. Optical analyses indicated a melting on the enamel that suffered laser irradiation for G2 and G5 and crystal surface disorganization for G4. Sandblasting partially removes the melting of the laser effect (G3).

CONCLUSION

The sandblasting is a dispensable step for bonding lingual brackets, and the melting of the enamel after laser irradiation does not compromise the bracket adhesive resistance.

CLINICAL RELEVANCE

The Nd:YAG laser became an interesting tool to prevent caries and decrease prevalence of white spot lesions in orthodontic treatments, without systemic effects in patients with genetic high risks of caries.

Laser-assisted prevention of enamel caries: a 10-year review of the literature

Since the invention of lasers in dentistry, investigations in caries prevention by the use of laser radiation have been proposed. There are several mechanisms stated for this purpose such as photothermal and/or photochemical interaction processes with the enamel. Alone or in conjugation with topical fluoride application, this treatment modality may improve enamel acid resistance in high-caries-risk populations. Data collection was done by searching the keywords caries, prevention, and laser in PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar. Lasing protocols of the collected literature and their effectiveness as well as examination methods used to verify treatment outcomes have been evaluated. One hundred eighteen publications were found for the last 10 years. The wavelengths investigated for caries prevention are mainly located in the near and the mid-infrared spectral range. In the evaluated period of time, investigations using CO₂; Er:YAG; Er,Cr:YSGG; Er:YLF; fundamental, second, and third harmonic generations of Nd:YAG; diodes; and argon ion lasers were found in the databases. Accounting for 39% of the literature, CO₂ laser was the most examined system for this purpose. Reviewing the literature in this narrative review showed that all laser systems presented a positive effect in varying degrees. Laser irradiation could be an alternative or synergistic to topical fluoridation for enamel caries prevention with longer lasting effect. Further research should be focused on selecting proper laser settings to avoid damage to enamel and developing effective evidence-based clinical protocols.

Effect of Erbium Laser on Microtensile Bond Strength of Fissure Sealant in Primary Teeth: An in vitro Study

Background:

Laser etching has several advantages as compared with conventional acid etching. However, results of earlier studies on conditioning surfaces with erbium, chromium:yttrium–scandium–gallium–garnet (Er, Cr:YSGG) before application of the fissure sealant have been inconclusive.

Aim:

The study aimed to evaluate the microtensile strength of resin-based fissure sealant bonded to primary enamel conditioned by Er, Cr:YSGG laser with varying power outputs.

Materials and Methods:

Fifty sound primary first molars were randomized into the following five groups based on pretreatment choice: Group 1: 3.5 W laser etching + acid etching; Group 2: 2.5 W laser etching + acid etching; Group 3: 3.5 W laser etching with no acid; Group 4: 2.5 W laser etching with no acid and Group 5: acid etching with no laser. Acid etch was performed with 35% orthophosphoric acid for 30 s. Laser etching was performed with Er, Cr:YSGG (2780 nm) laser using G6 tips and 600 μm diameter, 2.5 W or 3.5 W power outputs, pulse duration of 140 μs and a repetition rate of 20 Hz. Sealant was applied on the buccal surface followed by an incremental buildup with composite resin. Microtensile bond strength was assessed and compared among the five groups using one- and two-way ANOVA.

Results:

There was no statistical difference in the mean bond strength between groups except in Group 4 (9.66 MPa) (Group 1: 15.57 MPa; Group 2: 14.18 MPa; Group 3: 14.78 MPa; Group 5: 14.63 MPa).

Conclusion:

Pretreatment with 3.5 W Er, Cr:YSGG laser alone results in microtensile bond strengths similar to that produced by acid etching, indicating that enamel etching using 3.5 W Er, Cr:YSGG laser would result in the long-term success of pit and fissure sealants in primary teeth.

Variation on Molecular Structure, Crystallinity, and Optical Properties of Dentin Due to Nd:YAG Laser and Fluoride Aimed at Tooth Erosion Prevention

This in vitro study evaluated the compositional, crystalline, and morphological effects promoted by Nd:YAG laser on root dentin, and verified the effects of laser and topical acidulated phosphate fluoride application (APF-gel) on dentin erosion. 180 bovine dentin slabs were randomized into 4 groups (n = 45): G1–untreated, G2–APF-gel (1.23% F⁻, 4 min), G3–Nd:YAG (1064 nm, 84.9 J/cm², 10 Hz), and G4–APF-gel application followed by Nd:YAG laser irradiation. The compositional, crystalline, and morphological effects promoted by treatments were investigated on five samples of each experimental group. The other samples were submitted to a 5-day, 10-day, or 15-day erosive and abrasive demineralization and remineralization cycling in order to create erosion lesions. The area and depth of lesions, as well as the optical attenuation coefficient, were assessed, and all data were statistically analysed (p < 0.05). Nd:YAG laser promoted the reduction of carbonate, the formation of tetracalcium phosphate, as well as the melting and recrystallization of the dentin surface. Laser significantly decreased the area and depth of erosion lesions and altered the optical attenuation coefficient when compared to untreated and APF-gel groups, but the association of APF-gel and laser did not promote an additional effect. Nd:YAG laser irradiation can be a promissory treatment to prevent dentin erosion and the abrasion process.

Comparison of microtensile bond strength of a resin composite to enamel conditioned by acid etching and Er,Cr:YSGG laser in human primary teeth

AIM

This study was designed to compare the bond strength of composite resin restorations on the buccal surface of primary human canine after conditioning by conventional acid etching and Er,Cr:YSGG laser.

METHODS

Twenty sound primary canines were cut buccolingually into two halves and each half was randomly placed in Er,Cr:YSGG laser or acid etch group. The samples in the acid etch group were etched with 37% phosphoric acid for 30 s. The samples in the laser group were prepared by Er,Cr:YSGG laser. The G6-Tips and 600 µm diameter were used with a 1.5 W of power output, pulse duration of 140 µs and repetition rate of 20 Hz. The bonding agent was applied on the buccal surface of each sample and layers of resin composite were placed. The samples' bond strengths were evaluated by a microtensile test instrument.

RESULTS

The mean of microtensile bond strength was 18.55±6.41 in the laser group and 24.62±5.56 in acid etch group. Microtensile bond strength achieved by laser conditioning was significantly lower than microtensile bond strength achieved by the conventional acid etching. Statistics To compare the results between the acid etch and laser group, the paired t test was performed (p value<0.001).

CONCLUSION

Conditioning enamel in primary teeth by Er,Cr:YSGG laser, cannot be used as an alternative method for acid etching and cannot substitute this conventional method.