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

The effect of 400 nm femtosecond laser and Zn(II)chlorin e6 methyl ester (Zn(II)e6Me) photosensitizer on disinfection of radicular dentin bonded to glass fiber post

AIM

To assess and compare push-out bond strength (PBS) when canal disinfected with 5.25% NaOCl, 400 nm femtosecond laser, and natural PS activated by PDT (CP and Zn (II) Ce6 methyl ester) on bond efficacy of radicular dentin bonded to glass fiber post.

MATERIAL AND METHODS

A sum of 40 non-traumatic, cautiously extracted with closed apex human mandibular premolars were collected and decoronated up to the cement-o-enamel junction. Canals of all specimens were cleaned and shaped using a Protaper universal NiTi system via a crown-down approach, then finally dried out and obturated with gutta-percha. Post alignment space was formed with peso reamers and sanitized. Then samples were randomly allocated into four groups as per the radicular dentin designated disinfection protocols. Group 1 disinfected with curcumin photosensitizer + EDTA, group 2: 5.25% NaOCl and EDTA, group 3: Zn (II) Ce6 methyl ester and EDTA and group 4 sanitized with 400 nm fs-laser + EDTA. GFP was cemented into the radicular canal space and specimens were placed in a thermocycler. Segmentation of the root was done at three levels (coronal, middle, and apical) and positioned in a universal testing machine for PBS analysis. Failure mode analysis was performed using a stereomicroscope and statistical analysis was executed by one-way ANOVA and Tukey multiple comparison tests at a statistically significant level of p < 0.05.

RESULTS

The highest PBS was revealed by group 2 canal disinfected with 5.25% NaOCl +17% EDTA (control) at coronal (9.49 ± 1.42 MPa) and middle (7.545 ± 0.15 MPa) root levels. Whereas, the lowest PBS was displayed by group 3: Zn (II) Ce6 methyl ester +17% EDTA at coronal (6.31 ± 0.54 MPa) middle (4.85 ± 0.11 MPa) root levels respectively. Intergroup comparison presented that radicular dentin disinfected with 400 nm femtosecond laser + 17% EDTA substantiated comparable PBS result to group 2 (control) at all three root levels (p > 0.05). Likewise, root surface disinfection with Curcumin activated by PDT+17% EDTA unveiled no statistically significant result for specimens disinfected with Zn(II) Ce6 methyl ester +17% EDTA(p > 0.05). Furthermore, apical root segments in all groups showed a substantial decrease in PBS value and were comparable (p > 0.05).

CONCLUSION

The bond efficacy of glass fiber post to radicular dentin disinfected with 400 nm femtosecond laser has the potential to be used as an alternative to conventional sodium hypochlorite.

Disinfection of caries affected dentin using Rose Bengal, Titanium Sapphire Laser; Ammonium Hexa-fluorosilicate, and ozonated water on resin dentin bond strength

AIM

The present study intended to evaluate the shear bond strength (SBS) of resin cement bonded to caries affected dentin (CAD) after disinfection with rose Bengal (RB), Ti-Sapphire Laser, Ammonium Hexafluorosilicate (NH₄)₂[SiF₆], and ozonated water (O₃) MATERIAL AND METHODS: A total of 100 extracted human mandibular molars were acquired using caries severity code, 6 of the ICDAS criteria. To achieve homogeneity and prevent size-biased distributions, the average cavity preparation of all specimens had a depth of 2 mm and a breadth of 3 mm. Specimens were divided into five groups (n = 20) at random according to type of disinfection. Group 1: control group, Group 2: RB, Group 3: O₃, Group 4: Ti-sapphire laser, and Group 5: (NH4)2[SiF₆]. All specimens were etch and rinsed, bonding agent was applied and restored with resin cement. Estimation of SBS was performed by placing samples (10/group) in universal testing machine. Stereomicroscope under 40 × magnification was employed for failure mode analysis (FMA). Statistical analysis was executed using the ANOVA and the Tukey multiple test (p<0.05).

RESULTS

The highest SBS was demonstrated in the control group when CAD bonded to resin cement without disinfection (18.22±1.14 MPa). Likewise, the lowest SBS values were unveiled by CAD disinfection with O₃ (12.44±1.36 MPa). Similarly, CAD when disinfected with RB (16.25±1.01 MPa) and Ti-sapphire laser (16.25±1.22 MPa) bonded to resin cement exhibited comparable bond results (p>0.05).

CONCLUSION

Caries affected dentin when treated with etch and rinse technique without the use of disinfectant displayed the highest SBS. However, it was seen that utilization of various disinfectants has altered the adhesion capacity or bonding efficacy of caries-affected dentin.

Effect of Cavity Disinfectants on Dentin Bond Strength and Clinical Success of Composite Restorations-A Systematic Review of In Vitro, In Situ and Clinical Studies

Cavity disinfection becomes an important step before a dental restorative procedure. The disinfection can be obtained cleaning the dental cavity with antimicrobial agents before the use of adhesive systems. The aim of this study was to conduct a systematic review on the effect of different cavity disinfectants on restorations’ adhesion and clinical success. A search was carried out through the Cochrane Library, PubMed, and Web of Science. In vitro and in situ studies reporting results on dentin bond strength tests, and clinical studies published until August 2020, in English, Spanish and Portuguese were included. The methodological quality assessment of the clinical studies was carried out using the Revised Cochrane risk-of-bias tool. Chlorhexidine could preserve adhesion to dentin. EDTA and ethanol had positive results that should be further confirmed. Given the significant lack of scientific evidence, the use of lasers, fluoridated agents, sodium hypochlorite, or other products as cavity disinfectants should be avoided. Chlorhexidine is a safe option for cavity disinfection with adequate preservation of adhesion to dentin. Moreover, future researches should be focused on the efficacy of these disinfectants against cariogenic bacteria and their best application methods.

Influence of Er:YAG and Ti:sapphire laser irradiation on the microtensile bond strength of several adhesives to dentin

The aim of the present study was to evaluate the influence of erbium:yttrium-aluminum-garnet (Er:YAG) and Ti:sapphire laser irradiation on the microtensile bond strength (MTBS) of three different adhesive systems to dentin. Flat dentin surfaces from 27 molars were divided into three groups according to laser irradiation: control, Er:YAG (2,940 nm, 100 μs, 2.7 W, 9 Hz) and Ti:sapphire laser (795 nm, 120 fs, 1 W, 1 kHz). Each group was divided into three subgroups according to the adhesive system used: two-step total-etching adhesive (Adper Scotchbond 1 XT, from now on XT), two-step self-etching adhesive (Clearfil SE Bond, from now on CSE), and all-in-one self-etching adhesive (Optibond All-in-One, from now on OAO). After 24 h of water storage, beams of section at 1 mm(2) were longitudinally cut from the samples. Each beam underwent traction test in an Instron machine. Fifteen polished dentin specimens were used for the surface morphology analysis by scanning electron microscopy (SEM). Failure modes of representative debonded microbars were SEM-assessed. Data were analyzed by ANOVA, chi-square test, and multiple linear regression (p < 0.05). In the control group, XT obtained higher MTBS than that of laser groups that performed equally. CSE showed higher MTBS without laser than that with laser groups, where Er:YAG attained higher MTBS than ultrashort laser. When OAO was used, MTBS values were equal in the three treatments. CSE obtained the highest MTBS regardless of the surface treatment applied. The Er:YAG and ultrashort laser irradiation reduce the bonding effectiveness when a two-step total-etching adhesive or a two-step self-etching adhesive are used and do not affect their effectiveness when an all-in-one self-etching adhesive is applied.