Ablative potential of four different pulses of Er:YAG lasers and low-speed hand piece

Effect of green tea-loaded chitosan nanoparticles on leathery dentin microhardness

The purpose of this study was to assess the effect of a chitosan-based nanoformulation containing green tea on leathery (remaining) dentin subsurface microhardness. Size distribution, polydispersity index (PDI) and zeta potential (mV) of nanoformulations were previously determined by dynamic light scattering (DLS). Human dentin specimens were exposed to Streptococcus mutans for 14 d. Soft dentin were selectively removed by Er:YAG laser (n = 30) or bur (n = 30). Remaining dentin was biomodified with chitosan nanoparticles (Nchi, n = 10) or green tea-loaded chitosan nanoparticles (Gt + Nchi, n = 10) for 1 min. Control group (n = 10) did not receive any treatment. Subsurface microhardness (Knoop) was evaluated in hard (sound) and soft dentin, and then, in leathery dentin and after its biomodification, at depths of 30, 60 and 90 μm from the surface. Nchi reached an average size of ≤ 300 nm, PDI varied between 0.311 and 0.422, and zeta potential around + 30 mV. Gt + Nchi reached an average size of ≤ 350 nm, PDI < 0.45, and zeta potential around + 40 mV. Soft dentin showed significantly reduced microhardness at all depths (p > 0.05). The subsurface microhardness was independent of choice of excavation method (p > 0.05). At 30 µm from the surface, Gt + Nchi increased the leathery dentin microhardness compared to untreated group (p < 0.05). Nchi promoted intermediate values (p > 0.05). Both nanoformulations showed an average size less than 350 nm with nanoparticles of different sizes and stability along the 90-day period evaluated. Subsurface microhardness of bur-treated and laser-irradiated dentin was similar. At 30 µm, the biomodification with Gt + Nchi improved the microhardness of leathery dentin, independently of caries excavation method used.

Selective Removal of Necrotic Dentin in Primary Teeth Using Laser Irradiation: One-Year Clinical Evaluation of Composite Restorations

Introduction: This study aimed to evaluate the child's salivary cortisol levels, clinical performance and marginal adaptation of restorations after selective removal of necrotic dentin in primary teeth using Er: YAG laser irradiation. Methods: A double-blind clinical study was performed in children at 7-10 years. Children who had at least 2 teeth with carious lesions involving the occlusal and proximal surfaces of primary molars counterparts were selected. Removal of necrotic dentin was performed by 2 methods: Er: YAG laser irradiation and bur-preparation. Cortisol levels (n =24) was evaluated by ELISA. Clinical analysis (n =20) was performed after the restorations polish, 6 and 12 months after restorative procedure using United States Public Health Service (USPHS) method and photographs. Scanning electron microscopy (SEM) was used to analyz the marginal gap formation (n =20). The analysis of the data was performed by 95% confidence interval, Shapiro-Wilk test, Friedman and Wilcoxon post hoc tests (α =5%). Results: Cortisol levels were higher during selective removal of necrotic dentin, regardless of the method used (P>0.05). After 12 months, there was no evidence of the difference in the restorations performed on cavities prepared by both methods. SEM analysis revealed that the laser-irradiated teeth showed 10% of gaps in the full extent of restoration. For bur-prepared teeth, 20% of gaps were found at the cavosurface margin. Conclusion: The salivary cortisol levels on children that received Er: YAG laser irradiation for removal the necrotic dentin was similar to the control group. Class II restorations evaluated after 1 year period did not suffer interference by the use of Er: YAG laser irradiation.

Shear Bond Strength of Orthodontic Brackets Luted with RMGIC After Er:YAG Laser Etching with Two Pulse Modes Using a Digitally Controlled "X-Runner" Handpiece

OBJECTIVE

To compare the shear bond strength (SBS) values of orthodontic brackets luted using a resin-modified glass ionomer cement (RMGIC) on enamel surfaces etched using either an Er:YAG laser in two different working modes, or a conventional etching protocol, including phosphoric acid.

MATERIALS AND METHODS

Sixty healthy human premolars were randomly allocated to three experimental groups (n = 20) and etched with: Group 1: Er:YAG laser in super-short pulse (SSP) mode (100 mJ, 20 Hz, 2 W); Group 2: Er:YAG laser in quantum square pulse mode (120 mJ, 10 Hz, 1.2 W) using a digitally controlled handpiece ("X-Runner"); Group 3 (control): 5.25% sodium hypochlorite pretreatment, then 37% phosphoric acid for 15 sec. Stainless steel brackets were bonded using light-curing RMGIC for orthodontic bonding. After term cycling (1800 cycles), SBS testing was performed using a universal testing machine. After debonding, both enamel and bracket surfaces were examined to determine the amount of RMGIC still present on the surfaces.

RESULTS

Group 3 surfaces gave the lowest mean SBS (10.6104 ± 2.66196 MPa), whereas Group 1 provided the highest 1 (13.1795 ± 3.37904 MPa), which was significantly different from the control (Group 3, p = 0.0226). Group 2 provided intermediate values (11.8486 ± 0.59832 MPa) nonsignificantly different from the control or from SSP (p = 0.4215 and p = 0.3082, respectively).

CONCLUSIONS

Er:YAG laser treatment in SSP mode of enamel surfaces for orthodontic bonding provided higher SBS and a shear behavior of the luting material similar to the conventional acid-etching procedures, making it a viable alternative to acid etching.

Short-pulse Er:YAG laser increases bond strength of composite resin to sound and eroded dentin

This study evaluated the influence of the irradiation with a short-pulse Er:YAG laser on the adhesion of composite resin to sound and eroded dentin (SD and ED). Forty-six samples of occlusal dentine, obtained from human molars, had half of their surface protected, while the other half was submitted to erosive cycles. Afterward, 23 samples were irradiated with Er:YAG laser, resulting in four experimental groups: SD, sound irradiated dentine (SID—Er:YAG, 50  μs 50  μs , 2 Hz, 80 mJ, and 12.6  J/cm 2 12.6  J/cm2 ), ED, and eroded irradiated dentin (EID—erosion + Er:YAG laser). A self-etching adhesive system was used, and then cylinders of composite resin were prepared. A microshear bond strength test was performed after 24 h storage (n=20 n=20 ). The morphology of SD and ED, with or without Er:YAG laser irradiation, was evaluated under scanning electron microscopy (n=3 n=3 ). Bond strength values (MPa) were subjected to analysis of variance followed by Tukey’s test. Statistically significant differences were found among the experimental groups: SD (9.76±3.39  B 9.76±3.39  B ), SID (12.77±5.09 A 12.77±5.09 A ), ED (5.12±1.72 D 5.12±1.72 D ), and EID (7.62±3.39 C 7.62±3.39 C ). Even though erosion reduces the adhesion to dentin, the surface irradiation with a short-pulse Er:YAG laser increases adhesion to both ED and SD.

Ablative Potential of Er:YAG Laser in Dentin: Quantum Versus Variable Square Pulse

OBJECTIVE

The primary objective of this study was to compare the dentin ablation volume and ablation rate of quantum square pulse (QSP), using two different pulse energy settings plus a new digitally controlled dental laser handpiece (X-Runner), with those of variable square pulse (VSP), using three different pulse durations. The secondary objective was to examine, by scanning electron microscopy (SEM), the surface effects of ablation with the different Er:YAG laser modes on the dentin surfaces.

BACKGROUND DATA

The available literature has limited data on the efficiency of different operating modes, pulse durations, and the new digitally controlled handpiece of the Er:YAG laser on human dentin.

MATERIALS AND METHODS

Freshly extracted human molars (n = 72) were divided into two experimental groups (n = 36 each): (1) QSP group, and (2) VSP group. Each group was randomly divided into three subgroups (n = 12 each). In the QSP group, preparations in dentin were performed using 250 and 500 mJ of pulse energy with the conventional handpiece, and with the X-Runner handpiece set at 250 mJ pulse energy. In the VSP group, cavity preparations were performed using three pulse variables: super short pulse (SSP), micro short pulse (MSP), and short pulse (SP). Cavity preparations were made in dentin at time intervals of 1, 2, and 5 sec. A laser triangulation profilometer was used to determine cavity volumes. Surface analysis of the ablated dentin specimens was performed by SEM.

RESULTS

For time intervals of 1 and 2 sec, ablated volume and ablation rate for QSP-500 mJ were significantly higher than for all other groups (p < 0.0001). For the 5-sec time interval, X-Runner and QSP-500 mJ were the most efficient in dentin ablation (p < 0.0001). Dentin surfaces were free of smear layer in all groups.

CONCLUSIONS

The most efficient modes of dentin ablation in the study were the QSP-500 mJ and X-Runner groups. Dentin surfaces were free of smear layer in all groups.

Caries removal in deciduous teeth using an Er:YAG laser: a randomized split-mouth clinical trial

OBJECTIVES

The aim of the present clinical randomized split-mouth study was to evaluate the effectiveness and efficiency of an Er:YAG laser for caries removal in primary molars, microbiological dentin analysis, and clinical restorations after 1 year in 29 children.

MATERIALS AND METHODS

The children's teeth were randomized into two groups: (I) an Er:YAG laser group and (II) a bur preparation group. The efficiency of the treatments (the time necessary for the removal of carious tissue) was evaluated based on the time spent on caries removal in the deciduous molars. The effectiveness (caries removal capacity) of the caries removal was determined by means of a blind test in which the examiner performed a tactile and visual examination of the dentin. Microbiological analysis was performed by counting the Streptococcus mutans and Lactobacillus sp in the remaining dentin. Clinical analysis of restorations was performed using the USPHS method in combination with photographs of restored teeth, 7 days after the restorative procedure and again after 1 year. All cavities were restored with the Adper Single Bond 2/Filtek Z350 system. The obtained data were analyzed with a significance level of 5 %.

RESULTS

The Er:YAG laser was less effective and had the same efficacy as bur preparation during caries removal at the pulpal wall of deciduous molars. In the surrounding walls, bur preparation was the more effective method. Regardless of the method employed, the affected dentin in the pulpal wall had similar amounts of S. mutans and Lactobacillus sp. The restorations were clinically accepted by the USPHS method over a 1-year period.

CONCLUSION

It can be concluded that caries removal with an Er:YAG laser has no influence on the clinical behavior of restorations.

CLINICAL RELEVANCE

Irradiation with an Er:YAG laser is appropriate for caries removal in primary teeth.

Effect of laser preparation on bond strength of a self-adhesive flowable resin

The aim of this in vitro study was to evaluate the effect of laser treatment on shear bond strength of a self-adhesive flowable resin composite to human dentin. Eighty extracted sound human molar teeth were used for the study. The teeth were sectioned mesiodistally and embedded in acrylic blocks. The dentin surfaces were ground wet with 600-grit silicon carbide (SiC) paper. They were randomly divided into two preparation groups: laser (Er:YAG laser, with 12 Hz, 350 mJ energy) and control (SiC). Each group was then divided into two subgroups according to the flowable resin composite type (n = 20). A self-adhesive flowable (Vertise Flow) and a conventional flowable resin (Premise Flow) were used. Flowable resin composites were applied according to the manufacturer's recommendations using the Ultradent shear bond Teflon mold system. The bonded specimens were stored in water at 37 °C for 24 h. Shear bond strength was tested at 1 mm/min. The data were logarithmically transformed and analyzed using two-way analysis of variance and Student-Newman-Keul's test at a significance level of 0.05. The self-adhesive flowable resin showed significantly higher bond strength values to laser-prepared surfaces than to SiC-prepared surfaces (p < 0.001). The conventional flowable resin did not show such differences (p = 0.224). While there was a significant difference between the two flowable resin composites in SiC-prepared surfaces (p < 0.001), no significant difference was detected in laser-prepared surfaces (p = 0.053). The bond strength of a self-adhesive flowable resin composite differs according to the type of dentin surface preparation. Laser treatment increased the dentin bonding values of the self-adhesive flowable resin.