Shear bond strength of acid and laser conditioned enamel and dentine to composite resin restorations: An in vitro study

Shear bond strength of a composite resin restoration in primary teeth following cavity preparation using laser- an in-vitro study

To evaluate and compare the shear bond strength of composite resin restorations in primary teeth, following cavity preparation with both traditional dental burs and laser irradiation. One hundred primary molars extracted from the children visiting our department were collected and randomly divided into five groups (A-E) with 20 teeth in each group. In groups A, B, C, D, and E the teeth samples were etched with phosphoric acid, Er; YAG laser followed by acid etching, Er, Cr: YSGG laser followed by acid etching, Er; YAG laser etching only and Er, Cr: YSGG laser etching only, respectively. Following, all the samples were restored with composite resin and subjected to 500 cycles of thermocycling. The shear bond strength of the resin composite was analyzed. The type of fractures was also noted. Data obtained were subjected to statistical analysis. The mean value of shear bond strength of Group A, B, C, D, and E was 17.562 ± 0.810, 15.928 ± 0.415, 14.964 ± 0.566, 11.833 ± 0.533 and 11.187 ± 0.517, respectively. Adhesive failure was most commonly seen in all the groups. The phosphoric acid etching remains a highly effective technique for pre-treating dentin in composite resin restorations. The shear strength of composite resin to the dentin of laser-prepared cavity in primary teeth can be improved by the addition of acid etching.

Effect of chitosan and CMCS on dentin after Er:YAG laser irradiation: shear bond strength and surface morphology analysis

OBJECTIVES

The aim of the present study was to evaluate the effect of chitosan and carboxymethyl chitosan (CMCS) on dentin surface morphology and bonding strength after irradiation of Er:YAG laser.

METHODS

Eighty-four laser-irradiated dentin samples were randomly distributed into three groups (n = 28/group) according to different surface conditioning process: deionized water for 60s; 1wt% chitosan for 60s; or 1wt% CMCS for 60s. Two specimens from each group were subjected to TEM analysis to confirm the presence of extrafibrillar demineralization on dentin fibrils. Two specimens from each group were subjected to morphological analysis by SEM. Seventy-two specimens (n = 24/group) were prepared, with a composite resin cone adhered to the dentin surface, and were then randomly assigned to one of two aging processes: storage in deionized water for 24 h or a thermocycling stimulation. The shear bond strength of laser-irradiated dentin to the resin composite was determined by a universal testing machine. Data acquired in the shear bond strength test was analyzed by one-way ANOVA with the Tukey honestly significant difference post hoc test and Independent Samples t-test (α = 0.05).

RESULTS

CMCS group presented demineralized zone and a relatively smooth dentin surface morphology. CMCS group had significantly higher SBS value (6.08 ± 2.12) without aging (p < 0.05). After thermal cycling, both chitosan (5.26 ± 2.30) and CMCS group (5.82 ± 1.90) presented higher bonding strength compared to control group (3.19 ± 1.32) (p < 0.05). Chitosan and CMCS group preserved the bonding strength after aging process (p > 0.05).

CONCLUSIONS

CMCS has the potential to be applied in conjunction with Er:YAG laser in cavity preparation and resin restoration.

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.

Effectiveness of Diode Laser in Intraoral Soft Tissue Surgeries - An Evaluative Study

Introduction

The clinical application of the diode laser seems to have beneficial effects in surgery. The laser provides precise and rapid tissue dissection, excellent haemostasis and lessens post-operative inflammation. This study was done to assess the clinical effectiveness of diode laser in the management of different varieties of intraoral soft-tissue lesions.

Materials and Methods

After applying exclusion criteria, a total of 50 samples were selected with benign intraoral soft-tissue lesions treated with a diode laser under local anaesthesia between September 2017 and September 2020. Each patient was followed up on the 3rd, 7th and 15th post-operative days for healing, pain, infection and swelling.

Results

From all patients, a total of 50 were evaluated in the study; out of all, 60% of patients had no pain on the 2nd follow-up. As per the Landry Index of Healing, 54% of patients had excellent healing. None of the cases had post-operative bleeding, infection was present in 4% at the 1st-2nd follow-up, and in 2% of cases, post-operative swelling was present. The efficacy of diode lasers was tested using the Chi-square test and P < 0.01, which was statistically significant.

Discussion

Diode laser seems to be superior over conventional treatment modalities as it provides a bloodless dry field and increases patient comfort during surgery. It also lessens the post-operative pain and swelling. Diode laser can safely and effectively be used as a treatment modality for benign soft-tissue lesions, without any complication and without compromising the health and function of patients.

Exploration and preliminary clinical investigation of an adhesive approach for primary tooth restoration

The current study aims to investigate a suitable adhesive for primary tooth enamel. Shear bond strength (SBS) of primary teeth and the length of resin protrusion were analyzed using one-way ANOVA with Bonferroni multiple comparison tests after etching with 35% H ₃PO ₄. SBS and marginal microleakage tests were conducted with Single Bond Universal (SBU)/Single Bond 2 (SB2) adhesives with or without pre-etching using a nonparametric Kruskal-Wallis test. Clinical investigations were performed to validate the adhesive for primary teeth restoration using Chi-square tests. Results showed that the SBS and length of resin protrusion increased significantly with the etching time. Teeth in the SBU with 35% H ₃PO ₄ pre-etching groups had higher bond strength and lower marginal microleakage than those in the SB2 groups. Mixed fractures were more common in the 35% H ₃PO ₄ etched 30 s + SB2/SBU groups. Clinical investigations showed significant differences between the two groups in cumulative retention rates at the 6-, 12- and 18-month follow-up evaluations, as well as in marginal adaptation, discoloration, and secondary caries at the 12- and 18-month follow-up assessments. Together, pre-etching primary teeth enamel for 30 s before SBU treatment improved clinical composite resin restoration, which can provide a suitable approach for restoration of primary teeth.

The Use of Laser Energy for Etching Enamel Surfaces in Dentistry-A Scoping Review

BACKGROUND

In dental practice, different situations require etching the enamel layer. Acid etching, the present golden standard, may be replaced by other methods, such as laser etching. The main focus of our scoping review is to assess the existent literature regarding the effectiveness of different types of lasers, to identify the main aspects studied so far, and to understand where new search strategies are needed.

METHODS

The search was conducted in several databases focusing on the laser etching of human definitive enamel. We included English language articles published between January 2000 and December 2021.

RESULTS

The 34 articles reviewed showed that hard lasers, Er:YAG, Er,Cr:YAG, may represent an alternative etching method on enamel surfaces. They create a fractured, irregular surface and open dentin tubules, highly suitable for adhesion but with a lower risk of cavity formation. Nd:YAG, CO2, and Diode lasers do not help in creating sufficient shear bond strength. There is, however, evidence suggesting that microcracks in the enamel layer may appear after thermomechanical ablation using laser energy.

CONCLUSIONS

While the use of acid etching is still successfully used for enamel conditioning, some researchers have emphasized the role played by saliva in the enamel-remineralization process a few days after the procedure. In this context, laser energy can be used, especially for bonding ceramic brackets in the case of orthodontic treatments. However, as thermomechanical ablation can generate microcracks, further research is required in order to establish clear findings concerning the use of laser energy on enamel etching.

Shear bond strength of acid and laser conditioned enamel and dentine to composite resin restorations: An in vitro study

Objective

To compare the shear bond strength of enamel or dentin conditioned with either Er,Cr:YSGG (erbium, chromium: yttrium–scandium–gallium–garnet) laser or phosphoric acid to composite resin restoration.

Material and methods

Forty posterior human extracted teeth were used. After mesiodistal sectioning of the teeth crowns, the samples were randomly divided into two groups—in the first group (E), bonding was performed on the enamel after roughening and in the second group (D), the enamel was removed and bonding was performed on the dentin. These groups were further randomly divided into two subgroups according to the type of etching (n = 20 each). In the acid‐etched groups (EA and DA), the surfaces were etched with 37% phosphoric acid. In the laser‐conditioned groups (EL and DL), the surfaces were conditioned with Er,Cr:YSGG laser. Total‐etch adhesive system was used to bond all the 80 specimens resin composite. The composite was vertically light‐cured, and the specimens were subjected to a shear bond strength test. Modes of bond failure were determined with a stereomicroscope.

Results

The highest shear bond strength was observed for the DA group (16.25 ± 1.10 MPa, p < 0.0001), whereas the lowest was observed for the DL group (8.56 ± 0.67 MPa). The adhesive failure mode was the most frequently observed in all groups.

Conclusions

The shear bond strength of composite resin bonded to enamel and dentin etched with phosphoric acid was higher than when conditioned with Er,Cr:YSGG laser. Thus, laser conditioning is not recommended.