Micromorphology and adhesive performance of Er:YAG laser-treated dentin of primary teeth

Effect of various Er:YAG laser conditioning energies on dentin surface: micromorphological investigation and dentin-resin shear bond strength test

The aim of this study is to assess the influence of various Er:YAG laser energies on dentin surface micromorphology and dentine-resin shear bond strength (SBS). Eighty dentin specimens were prepared and divided randomly into ten groups: control group (CG), phosphoric acid-etched group (AG), four laser-conditioned groups treated with various pulse energies of 40, 60, 80, and 100 mJ (L40, L60, L80, L100), and four laser-conditioned acid-etched groups (LA40, LA60, LA80, LA100). Two specimens from each group underwent scanning electron microscopy examination, while the remaining six were subjected to the dentin-resin SBS test. Statistical analyses included Welch's analysis of variance (ANOVA), followed by post hoc Tamhane's T2 multiple comparisons test, Pearson's correlation, and Fisher's exact test. Pulse energies of 60, 80, and 100 mJ fully exposed the dentin tubule orifices, although 100 mJ lead to microcracks. Laser-conditioned surfaces exhibited smaller tubule diameters compared to acid-etched surfaces, and tubule diameters positively correlated with dentin-resin SBS. Laser-conditioned groups showed lower SBS values, while laser-conditioned acid-etched groups demonstrated higher SBS values. No significant relationship was observed between dentin surface roughness and SBS. The range of laser energies used for dentin conditioning had limited effects on SBS or failure modes. Laser conditioning with energies ranging from 40 to 100 mJ effectively removes the smear layer from the dentin surface. However, to enhance dentin-resin bond strength, further acid etching of the laser-conditioned surface is necessary.

Cavity Preparation by Laser in Primary Teeth: Effect of 2 Levels of Energy Output on the Shear Bond Strength of Composite Restoration to Dentin

Introduction: One of the main applications of laser in dentistry is the removal of dental caries and preparation of restorative cavities. The morphology and wettability of laser prepared surfaces are different from that of those prepared with conventional method which may affect the quality of the adhesive potential of bonding agents in these surfaces. This study aimed to assess the shear bond strength of a total-etch and self-etch adhesive system to primary tooth dentin prepared by two different energy densities of Er:YAG laser in comparison with surfaces prepared by bur. Methods: A total of 60 human primary second molars extracted for orthodontic purposes were selected and randomly divided into 3 main groups of equal (n=20). Group A: Preparation of dentin surface by bur; group B: Preparation of dentin surface by laser with 300 mJ energy level; group C: Preparation of dentin surface by laser with 400 mJ energy level. In each of the main groups, the teeth were randomly assigned to 2 subgroups. Composite resin material was bonded with the total-etch adhesive system in subgroups A1, B1, and C1 and with the self-etch adhesive system in subgroups A2, B2, and C2. The samples were thermo-cycled, and composite restorations shear bond strength was measured in MPa. Data were analyzed using two-way analysis of variance (ANOVA), and P values less than 0.05 were considered statistically significant. Results: The highest and the lowest shear bond strength values were observed in group A2 (Preparation by bur- Composite resin material bonded by Clearfil SE Bond) and group C2 (Preparation by laser with 400 mJ energy level - Composite resin material bonded by Clearfil SE Bond), respectively. The results showed no statistically significant differences between the study subgroups (P > 0.05). Conclusion: It is concluded that in terms of shear bond strength to dentin, Single Bond and Clearfil SE Bond adhesive agents adequately perform in primary tooth dentin prepared by Er: YAG laser with energy levels of 300 and 400 mJ and frequency of 10 Hz.

The Effect of Er:YAG Laser Irradiation and Different Concentrations of Sodium Hypochlorite on Shear Bond Strength of Composite to Primary Teeth's Dentin

Introduction: The aim of this study was to evaluate the effect of various concentrations of NaOCl on shear bond strength of composite resin to dentin of primary teeth, prepared with laser and bur. Methods: In this in vitro study, 48 primary molars were sectioned at mesiodistal direction and were randomly divided into 6 groups; G1: bur, G2: bur + NaOCl 2.5%, G3: bur + NaOCl 5.25%, G4: laser, G5: laser + NaOCl 2.5%, G6: laser + NaOCl 5.25%. One-Step Plus adhesive was applied after phosphoric acid gel and NaOCl over the dentin surfaces for all groups, and composite resin cylinders were bonded to the samples. After thermocycling, shear bond strengths of composite resin to dentin were measured and statistical analyses were done by means of t test and analysis of variance (ANOVA). Results: The mean shear bond strength showed no significant difference between the groups prepared with bur (13.82 ± 3.49) and laser (14.18 ± 3.65) (P > 0.05). The mean difference of shear bond strength between three groups G1, G2 and G3 and between G4, G5 and G6 were not statistically significant (P > 0.05). Scanning electron microscopy (SEM) figures showed an irregular surface in laser groups and fairly complete removal of smear layer from the orifices of the dentinal tubules, in the group in which NaOCl was used. Conclusion: The application of different concentrations of NaOCl does not significantly improve the bond strength in dentin surfaces prepared with laser or bur.

Energy output reduction and surface alteration of quartz tips following Er:YAG laser contact irradiation on soft and hard tissues in vitro

Though the Er:YAG laser (ErL) has been used in periodontal therapy, the irradiated tip damage has not been studied in detail. In this study, the change in the energy output, surface morphology, and temperature of quartz tips was evaluated following contact irradiation. Soft tissue, calculus on extracted human teeth, and porcine bone were irradiated by ErL for 60 min at 14.2 or 28.3 J/cm(2)/pulse and 20 Hz with or without water spray. The energy output ratio declined the most in the calculus group, followed by the bone and soft tissue groups with and/or without water spray. Carbon contamination was detected in all groups, and contamination by P, Ca, and/or other inorganic elements was observed in the calculus and bone groups. The rate of energy output reduction and the degree of surface alteration/contamination is variously influenced by the targeting tissue, temperature elevation of the tip and water spray.

Effects of Er:YAG laser on mineral content of sound dentin in primary teeth

The aim of the present study was to evaluate the mineral content of sound dentin in primary teeth prepared using an Er:YAG laser at two different power settings. Thirty-six primary second molars were used in this study. Three dentin slabs were obtained from each tooth, and the slabs were randomly divided into three groups: Group A, control; Group B, Er:YAG laser at 3.5 W, 175 mJ, and 20 Hz, short pulse mode; and Group C, Er:YAG laser at 4 W, 200 mJ, and 20 Hz, medium-short pulse mode. One dentin slab per group was used to evaluate the dentinal morphology and surface roughness values using SEM and profilometer, respectively. Mineral content in the dentin slabs were calculated by inductively coupled plasma-atomic emission spectrometry (ICP-AES). The data were analyzed by one-way analysis of variance and Tukey's HSD tests. No significant differences in Ca, K, Mg, Na, and P levels or Ca/P ratio were found among the groups (P > 0.05). SEM micrographs showed that surface irregularities increased with a higher power setting. The surface roughness after laser treatment in Group B and Group C was found to be similar, unlike Group A.

Effects of Er:YAG laser on bond strength of self-etching adhesives to caries-affected dentin

The erbium:yttrium-aluminum-garnet (Er:YAG) laser may be effective the bond strength of adhesive systems on dentine surfaces, the chemical composition and aggressiveness of adhesive systems in clinical practice. The purpose of this study was to evaluate the effects of the Er:YAG laser system with the bonding ability of two different self-etching adhesives to caries-affected dentine in primary molars. Ninety mid-coronal flat dentine surfaces obtained from sound and caries-affected human primary dentine were treated with an Er:YAG laser or a bur. The prepared surfaces were restored with an adhesive system (Xeno V; Clearfil S³) and a compomer (Dyract Extra). The restored teeth were sectioned with a low-speed saw and 162 samples were obtained. The bond strength of the adhesive systems was tested using the micro-tensile test method. The data were statistically analyzed. A restored tooth in each group was processed for scanning electron microscopy evaluation. The values of the highest bond strength were obtained from the Clearfil S³-Er:YAG laser-sound dentine group in all groups. (24.57 ± 7.27 MPa) (P > 0.05). The values of the lowest bond strength were obtained from the Xeno V-Er:YAG laser-sound dentine group in all groups (11.01 ± 3.89 MPa). It was determined that the Clearfil S³ increased the bond strength on the surface applied with Er:YAG laser according to the Xeno V.