Shear bond strength of a self-adhesive resin cement to dentin surface treated with Nd:YAG and femtosecond lasers

Effects of self-etch adhesive agitation with diode laser on dentin bond strength

The present study assessed the effect of active application of self-etch adhesives with diode laser irradiation on the shear dentin bond strength. Sixty bovine incisors, each embedded individually in hard plaster blocks, were divided into two groups based on the adhesive system used: Group 1 Adper Easy One and Group 2 Clearfil SE Protect. Based on the application technique of self-etch adhesives, each main group was further divided into three subgroups: passive application, active application with a micro-brush, and active application with a 976-nm diode laser tip (phototherapy active application). Shear bond strength tests were conducted using a universal testing machine and the data were analyzed by two-way ANOVA. Post hoc multiple comparisons were performed with the Tukey HSD test. Additionally, the statistical analysis of failure mode distribution was carried out using the chi-squared test (p < 0.05). While the adhesive system exhibited significant differences in shear dentin bond strengths, there were no significant differences in application techniques. Regardless of the application technique, Clearfil SE Protect demonstrated significantly higher dentin bond strength than Adper Easy One. In the present study, the utilization of phototherapy through a 976-nm diode laser for the active application of the tested self-etch adhesives demonstrated similar initial dentin bond strengths to conventional application methods.

Optical penetration models for practical prediction of femtosecond laser ablation of dental hard tissue

OBJECTIVES

To develop and practically test high-precision femtosecond laser ablation models for dental hard tissue that are useful for detailed planning of automated laser dental restorative treatment.

METHODS

Analytical models are proposed, derived, and demonstrated for practical calculation of ablation rates, ablation efficiency and ablated morphology of human dental enamel and dentin using femtosecond lasers. The models assume an effective optical attenuation coefficient for the irradiated material. To achieve ablation, it is necessary for the local energy density of the attenuated pulse in the hard tissue to surpass a predefined threshold that signifies the minimum energy density required for material ionization. A 1029 nm, 40 W carbide 275 fs laser was used to ablate sliced adult human teeth and generate the data necessary for testing the models. The volume of material removed, and the shape of the ablated channel were measured using optical profilometry.

RESULTS

The models fit with the measured ablation efficiency curve against laser fluence for both enamel and dentin, correctly capturing the fluence for optimum ablation and the volume of ablated material per pulse. The detailed shapes of a 400-micrometer wide channel and a single-pulse width channel are accurately predicted using the superposition of the analytical result for a single pulse.

CONCLUSIONS

The findings have value for planning automated dental restorative treatment using femtosecond lasers. The measurements and analysis give estimates of the optical properties of enamel and dentin irradiated with an infrared femtosecond laser at above-threshold fluence and the proposed models give insight into the physics of femtosecond laser processing of dental hard tissue.

Effects of Nd:YAG laser irradiation at different energy densities on dentin bond durability under simulated pulpal pressure

OBJECTIVES

To evaluate the effects of Nd:YAG laser irradiation on the microstructures of dentin surfaces and the long-term bond strength of dentin under simulated pulpal pressure.

MATERIALS AND METHODS

Under simulated pulp pressure, 30 freshly extracted caries-free third molars were cut into 2-mm-thick dentin samples and then divided into five groups: the control and laser groups (93.3 J/cm2; 124.4 J/cm2; 155.5 J/cm2; 186.6 J/cm2). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), and Vickers hardness were used to analyze the surface morphology, composition, and mechanical properties of the dentin before and after laser irradiation. Another 80 caries-free third molars were removed and treated as described above, and the resin was bonded to the dentin surface with Single Bond Universal (SBU) adhesive in self-etch mode to make stick specimens. Microtensile bond strength (µTBS), confocal laser scanning microscopy (CLSM), and interfacial silver nanoleakage tests before and after 10,000 times thermocycling were then performed to analyze the bonding properties and interfacial durability of each group.

RESULTS

SEM observations revealed that the surfaces of all laser group specimens were rough with open dentin tubules. Laser irradiation altered the surface composition of dentin while removing some collagen fibers but did not affect its surface hardness or crystallographic characteristics. Furthermore, laser irradiation with an energy density of 124.4 J/cm2 significantly promoted the immediate and aging bond strengths and reduced nanoleakage compared to those of the control group.

CONCLUSIONS

Under simulated pulp pressure, Nd:YAG laser pretreatment altered the chemical composition of dentin and improved the immediate and long-term bond strength.

CLINICAL RELEVANCE

This study investigated the optimal parameters for Nd:YAG laser pretreatment of dentin, which has potential as a clinical method to strengthen bonding.

Effect of Remineralization Pretreatments on Human Dentin Permeability and Bond Strength

This study aimed to evaluate Nd:YAG laser, calcium phosphate, and adhesive system effect as different pretreatments in different protocols on dentin permeability (DP) and bond strength (BS). Fifty human dentin discs were used (4 mm in diameter and 1,5 mm in height). Specimens were divided into five groups (n = 10): (A): adhesive system (control); (AL): adhesive system + Nd:YAG laser; (LAL): Nd:YAG laser + adhesive system + Nd:YAG laser; (PAL): calcium phosphate-based dentin desensitizer TeethMate + adhesive system + Nd:YAG laser; and group (PLAL): Nd:YAG laser + calcium phosphate-based dentin desensitizer + adhesive system + Nd:YAG laser. All materials were used according to the manufacturers' instructions. The specimens were submitted to artificial aging (5,000 thermal cycles and 12 × 10⁴ mechanical cycles) then a bond test was performed. DP was measured using the split chamber model. Data were submitted to one-way analysis of variance (ANOVA), paired t-test, RM ANOVA, and Tukey test (p < 0.05). All treatments were effective in DP reduction. For BS, the groups PAL and PLAL had improved BS with a statistically significant difference of the control group (A). Nd:Yag laser irradiation and calcium phosphate-based desensitizing agents significantly reduced DP, and the association between them could improve the BS on resin-human dentin interface.

Effects of Er: YAG, Er,Cr: YSGG, and Nd: YAG laser irradiation and adhesive systems on the immediate and long-term bond strength of dentin: a systematic review and meta-analysis

At present, lasers are increasingly used in the oral clinical field, and research and applications in dental hard tissue treatment are also increasing. The effect of laser etching dentin on the bonding strength of composite resin reported in the literature is still inconclusive. The purpose of this review was to evaluate whether laser etching can improve the immediate and long-term bonding strength of dentin and investigate the effect of different types of adhesives on the bonding strength of dentin. Two reviewers performed a literature search up from January 2012 to November 2021 in four databases: MEDLINE (PubMed), Web of Science, EMBASE, and the Cochrane Library. A total of 25 studies were included in the meta-analysis. The Cochrane Collaboration Bias Risk Assessment tool was used to evaluate the quality of the included literature, and an analysis was carried out using Review Manager Software version 5.3. The aging bond strength of dentin after erbium (Er): yttrium aluminum garnet (YAG) laser treatment was significantly lower than that of dentin in the bur group (P < 0.00001). At the same time, the bond strength of dentin immediately and aging after (Er), chromium-doped (Cr): yttrium scandium gallium garnet (YSGG) laser treatment was lower than that of dentin in the bur group (P < 0.05). There was no significant difference in the immediate and aging bonding strength among samples in the Er: YAG laser, Er, Cr: YSGG laser, and blank control groups (no laser or bur). The aging bond strength of samples after neodymium-doped (Nd): YAG laser treatment was higher than that of samples in the blank control group (P < 0.05); in addition, the performance of self-etching adhesive was slightly better than that of acid etching adhesive. Regardless of the applied surface treatment and the adhesive employed, dentin after aging showed significant bond degradation (P < 0.05). There was high heterogeneity of bond strength between different groups, and the small number of studies and the contradictory results may be the main reasons for this outcome.

Effect of Nd:YAG and Er:YAG laser tooth conditioning on the microleakage of self-adhesive resin cement

Statement of problem

Recently, the application of lasers in restorative dentistry has been considered for cavity preparation and surface conditioning of enamel and dentin. However, the beneficial effects of cavity surface conditioning by laser irradiation on microleakage are still controversial.

Purpose

This study aimed to compare the microleakage of self-etch adhesive resin cement with Nd:YAG and Er:YAG laser tooth surface conditioning to evaluate the capabilities of these lasers as a reliable replacement for etching cavities.

Materials and methods

Fifty-four class V cavities were prepared on the buccal and lingual surfaces of 27 sound human premolar teeth. The samples were randomly divided into three groups (n = 18): group 1: no conditioning; group 2: conditioned with Er:YAG laser (2940 nm, 10 Hz, 1.2 W); group 3: conditioned with Nd:YAG laser (1064 nm, 1.5 W, 10 Hz). All the cavities were filled with self-adhesive resin cement. After curing and polishing, the samples were immersed in 2% methylene blue solution for 24 h, and after being embedded in acrylic resin, they were sectioned longitudinally and examined under a stereomicroscope. The data were submitted to Kruskal–Wallis and Dunn tests (α = 0.05).

Results

The lowest microleakage mean rank was observed in the Er:YAG group (19.19), and the highest mean rank was noted in the Nd:YAG group (33.08), with significant differences between the three groups (P-value = .01). Pairwise comparisons demonstrated significant differences between the Er:YAG and Nd:YAG groups (P-value = .004) as well as Er:YAG and no conditioned groups (P-value =.022).

Conclusion

The irradiation of the Er:YAG laser (2940 nm, 10 Hz, 1.2 W) on cavity surface resulted in less marginal microleakage of self-etch adhesive resin cement restorations compared to Nd:YAG (1064 nm, 1.5 W, 10 Hz) and no conditioning groups.