Influence of fluoride varnish on shear bond strength of a universal adhesive on intact and demineralized enamel

Evaluation of the cytotoxicity of new formulations of cariostatic agents containing nano silver fluoride: an in vitro study

The objective of the study was to assess the indirect cytotoxicity of 600 ppm and 1500 ppm nano silver fluoride (NSF) compared to other commercial cariostatic agents. 56 dentin discs with 0.4 mm in thickness were obtained from intact human molars and adapted to artificial pulp chambers (APCs). The discs were divided into seven groups according to treatment (n = 8): no treatment (positive control-PC), 29% hydrogen peroxide (negative control-NC), 30% Cariestop (CS30), 38% Riva Star (RS38), 38% Advantage Arrest (AA38), 600 ppm NSF (NSF600), and 1500 ppm NSF (NSF1500). The cariostatic agents were applied on the occlusal surface of the dentin discs (facing upward), and the pulp surface (facing downward) remained in contact with the culture medium. Immediately after the treatments, the extracts (DMEM + cariostatic agent components diffused through the discs) were collected and applied to MDPC-23 cells, which were assessed for viability (CV-alamarBlue, live/dead), adhesion/spreading (F-actin), alkaline phosphatase (ALP) activity, and mineralization nodule (MN) formation. The data were statistically analyzed by ANOVA/Games-Howell (p = 0.05). CV and ALP activity in CS30, RS38, AA38, and NSF600 were similar to PC (p > 0.05). MN formation significantly decreased only in NC, CS30, RS38, and AA38 compared to PC (p < 0.001). Only NSF600 and NSF1500 did not differ from PC (p > 0.05) with mineralization nodules, and this specific cell activity significantly decreased in all other groups (p < 0.05). NSF solutions (600 ppm and 1500 ppm) did not cause transdentinal toxicity on MDPC-23 cells.

The effect of remineralization pretreatments on the enamel bond strength of demineralized and sound enamel: An in vitro study

Background

During tooth preparation, the clinician may face a hard remineralized enamel surrounding the cavity with unknown effects on the enamel bond strength. This study aims to assess the effect of remineralizing pretreatments with casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) or CPP-amorphous calcium fluoride phosphate (CPP-ACFP) on the bond strength of composite resin and sound or demineralized enamel.

Materials and Methods

This study employed an in vitro experimental factorial design. A total of 144 enamel surfaces were prepared and randomly divided into 12 groups (G1-G12). The surfaces of G7-12 were demineralized to create a lesion (L), while G1-6 were assigned to the sound (S) enamel group. The three pretreatment protocols were CPP-ACFP, CPP-ACP, or no pretreatment for a 10-day pH-cycling period. A composite rod was bonded to the surfaces using a self-etch or total-etch bonding system. Shear force was applied, and the bond strengths of the specimens were measured. The data were analyzed using the Kruskal-Wallis test, followed by pairwise comparisons using Dunn's test. The significance level for all tests was set at 0.05.

Results

The sound (S) groups (33.81 ± 8.48) showed a significantly higher bond strength than the lesion (L) groups (25.77 ± 6.69). Among the pretreatments, CPP-ACFP-pretreated groups had the highest bond strength (33.86 ± 8.87). Pairwise comparisons showed significant differences between CPP-ACFP-treated demineralized enamel and control demineralized enamel in both bonding systems (P = 0.019 and P = 0.025 for Clearfil SE and Optibond FL, respectively).

Conclusion

Pretreatment of demineralized enamel with CPP-ACFP before using total-etch and self-etch systems results in a bond strength comparable to that of sound enamel, making it clinically acceptable.

Evaluation of the Effect of Different Universal Adhesives on Remineralized Enamel by Shear Bond Strength and Fe-SEM/EDX Analysis

The aim of this study is to evaluate the shear bond strength of different universal adhesives applied to intact, demineralized, and remineralized enamel surfaces with total-etch and self-etch modes and to examine the effect of universal adhesives on the Ca/P mineral atomic and mass ratios of these enamel with FE-SEM/EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy) analysis. For this study, 264 bovine incisors were used. Samples in the demineralized and remineralized groups were kept in demineralization solution at 37 °C for 96 h to make an artificial initial carious lesion. After demineralization, half of the demineralized samples were remineralized with MI Paste Plus. For shear bond strength (n = 144) and FE-SEM/EDX analysis (n = 120), G-Premio Bond and Clearfil S3 Bond Universal were applied on enamel surfaces with total-etch and self-etch modes, and bond strength samples were restored with resin composite. All samples were tested. The results were evaluated statistically by a three-way ANOVA test. The shear bond strength of the remineralized enamel showed high bond strength values comparable to intact enamel for universal adhesive systems. The Ca/P mineral atomic and mass ratios in remineralized enamel showed higher values than demineralized enamel, similar to intact enamel for universal adhesive systems. Initial carious lesion surfaces are unsuitable enamel surfaces for restoration. The remineralization of this surface layer before adhesive procedures may positively affect bond strength.

Effect of re-mineralizing surface treatment on the shear bond strength of orthodontic bracket: A systematic review and meta-analysis of in-vitro studies

INTRODUCTION

Re-mineralizing surface pretreatment is essential for both controlling and preventing white spot lesion (WSL) throughout the time of fixed orthodontic treatment. It is also important that the re-mineralizing have no negative impact on the bonding between the bracket, adhesive, and enamel. Therefore, this review is aimed to investigate the orthodontic brackets' shear bond strength after re-mineralizing surface treatment of enamel.

MATERIAL AND METHODOLOGY

The review was conducted following the PRISMA 2020 guidelines. In-vitro experimental studies measuring shear bond strength (SBS) of orthodontic brackets on both demineralized and intact enamel following re-mineralizing surface treatment were included. Database search was done in PubMed, Scopus, and Science Direct during July 2023. Methodological quality of the studies was assessed according to the guidelines for the reporting of pre-clinical in-vitro studies. Both qualitative and quantitative analyses of the included studies were done.

RESULTS

Matching the inclusion criteria, 46 and 37 studies were selected for qualitative and quantitative analysis respectively. On intact enamel re-mineralizing agents had no negative impact on the brackets' SBS. On the contrary, they seemed to enhance the bond strength remarkably on the demineralized enamel.

DISCUSSION

Re-mineralizing surface pretreatment is crucial prior to fixed orthodontic treatment as it did not reduce the bond strength. Although, it cannot be judged depending solely on the in-vitro results with high heterogeneity. Clinical evidence is required to support the statement.

Effect of fluoride varnish in combination with simulated oral environment on enamel-bracket shear bond strength

To determine the effect of fluoride varnish application combined with a simulated oral environment prior to bracket bonding on the shear bond strength (SBS) between brackets and tooth enamel. Sixty de-identified, extracted teeth were grouped to either receive or not receive fluoride varnish and then stored for 7 days at 37 °C in phosphate-buffered saline (PBS) solution or PBS combined with three 15-min cycles/day in a demineralizing solution to simulate pH variation following meals. Subsequently, brackets were bonded and after 24-h dark cure at 37 °C, debonded using shear forces in a simulated oral environment. The maximum shear force was used to calculate SBS, and the adhesive remnant index (ARI) was determined by image analysis of photos of the bracket mesh pad after debonding. A statistically higher SBS (10.16 MPa) was observed when fluoride varnish was applied prior to storage in PBS + demineralizing solution compared to SBS (6.38 MPa) following storage in the same solution without varnish application. Based on 37% effect size, this difference is also clinically relevant. In contrast, no significant differences in SBS were observed with varnish application combined with PBS with no demineralizing solution or between storage solution alone. Moreover, there was no significant difference in ARI due to varnish combined with either storage method or storage solution only. Results suggest varnish application prior to bracket bonding in combination with simulated oral environment that included acid exposure is beneficial in maintaining higher SBS between bracket and enamel. Despite higher SBS, adhesive remaining on enamel did not increase.

Biodentine or Mineral Trioxide Aggregate as Direct Pulp Capping Material in Mature Permanent Teeth with Carious Exposure? A Systematic Review and Meta-analysis

OBJECTIVE

To evaluate the success rate of direct pulp capping (DPC) with Biodentine in mature permanent teeth with carious vital pulp exposure compared to that of DPC with mineral trioxide aggregate (MTA) by means of a systematic review and meta-analysis.

DATA SOURCES

The two authors searched independently the literature published through July 31, 2020, in five electronic databases (PubMed, the Cochrane Central Register of Controlled Trials, Web of Science Core Collection, the Wiley Online Library, and the SCOPUS database).

STUDY SELECTION

The research protocol was previously registered in the PROSPERO database (CRD42020192511). Clinical studies that met the inclusion criteria were chosen and independently screened by the authors.

DATA EXTRACTION

A custom-designed spreadsheet was used to extract the data. The quality of each study was evaluated by means of the revised Cochrane risk of bias (ROB) tool or the ROB of nonrandomized studies of interventions tool.

DATA SYNTHESIS

Three randomized controlled trials and one retrospective study met the inclusion criteria. Only one study had a high risk of bias. The included studies reported data on a total of 95 participants with an age range of 8-51 years. No significant difference was observed in the overall treatment outcome when comparing Biodentine with MTA (Risk ratio=1.00, 95% confidence interval [0.93-1.07], p=1.00).

CONCLUSIONS

Biodentine had comparable clinical and radiographic success to that of MTA when used as a DPC agent in mature permanent teeth with carious vital pulp exposure. Additional high-quality studies are needed.

Characterization of a novel enamel sealer for bioactive remineralization of white spot lesions

OBJECTIVES

45S5 Bioglass is a bioactive glass capable of releasing ions that can interact with dental hard tissues. The current study aimed at examining the effectiveness of 45S5 Bioglass in remineralizing enamel white spot lesion (WSL) as well as its effect on the bond strength of orthodontic brackets bonded to demineralized enamel.

MATERIALS AND METHODS

WSLs were induced in the buccal surfaces of 135 human extracted teeth by storage in acid solution pH 4.5 for four days. The specimens were then equally divided into three groups; Demineralized group, Bioglass group (BG), and control group (intact enamel). The groups were chemically analyzed using (FTIR/ATR) Fourier-transform infrared spectroscopy/attenuated total reflectance, (XRD) X-ray diffraction, and (SEM/EDS) scanning electron microscope equipped with electron-dispersive-spectroscopy. Moreover, 10 specimens from each group were tested using Transverse Micro Radiography (TMR) technique, and 15 specimens from each group were bonded with metal orthodontic brackets and tested for shear bond strength test (SBS). The data were analyzed statistically using One way ANOVA p < 0.05.

RESULTS

TMR study showed that bioglass group samples recorded lesion depth of 70.19 ± 29.21 μm and Δ Z (mineral loss) 732.15 ± 210.16 vol% μm which was significantly lower than the demineralized specimens having lesion depth of 115.75 ± 19.98 μm and Δ Z (mineral loss) 3472.69 ± 738.38 vol%μm, moreover, bioglass specimens recorded 14.15 ± 2.35 Mpa which was significantly higher than demineralized specimens 6.82+1.83 Mpa but less than the control specimens 20.5 + 6.1 MPa (p < 0.05). FTIR/ATR, XRD, and SEM/EDS tests showed that bioglass paste formed a layer of brushite crystals onto the treated enamel surface.

CONCLUSION

45S5 bioglass paste may serve as an effective remineralizing agent for demineralized enamel.

Shear bond strength of orthodontic brackets on intact and demineralized enamel after application of resin infiltrant, fluoride varnish and casein phosphopeptide-amorphous calcium phosphate remineralizing agents: in-vitro study

OBJECTIVE

To evaluate the effects of remineralizing agents on the shear bond strength (SBS) of orthodontic brackets bonded to intact and demineralized enamel.

MATERIAL AND METHODS

In this in-vitro study, 160 human premolars were divided into 8 groups, including group 1 with intact enamel as the positive control, group 2 with demineralized enamel as the negative control, groups 3-5 treated with fluoride varnish, Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) and resin infiltrant on intact enamel, and groups 6-8 treated with the same agents on demineralized enamel. Brackets were bonded using the conventional method, and the samples were thermocycled. SBS of the brackets was measured using a universal testing machine, and the adhesive remnant index (ARI) was assessed. Data were analysed with one-way ANOVA and post hoc statistical test at the significance level of 0.05.

RESULTS

SBS of the brackets in all groups with intact enamel was higher than that of their counterparts on demineralized enamel, which was only significantly different between groups 1 and 2 (P-value<0.001). SBS values of groups 7 and 8 were not significantly different from group 1 (P-value=1), yet the application of fluoride varnish on both intact (P-value=0.091) and demineralized enamel (P-value<0.001) created less SBS than in group 1.

CONCLUSIONS

All pre-treatment methods increased SBS of the brackets bonded to demineralized enamel, yet only the resin infiltrant and CPP-ACP produced SBS similar to that of intact enamel. Also, the use of fluoride varnish on intact enamel significantly reduced SBS.

Can silver diamine fluoride or silver nanoparticle-based anticaries agents to affect enamel bond strength?

Objectives

The aim of the current study is to investigate the effect of different anticaries agents, such as experimental agents based on silver nanoparticles (SNPs) and silver diamine fluoride (SDF), on the micro-shear bond strength (μ-SBS) of composite resin applied to intact enamel (IE) or demineralized enamel (DE).

Materials and Methods

Sixty dental enamel fragments were collected from human third molars and categorized into 6 groups (n = 10): positive control (IE), negative control (DE), IE + SDF, DE + SDF, IE + SNP and DE + SNP. Samples from DE, DE + SDF and DE + SNP groups were subjected to pH cycling; superficial microhardness test was performed to confirm demineralization. Resin composite build-ups were applied to the samples (0.75-mm diameter and 1-mm height) after the treatments (except for IE and DE groups); μ-SBS was also evaluated. Samples were analyzed under a stereomicroscope at 40× magnification to identify failure patterns. Data were subjected to one-way analysis of variance, followed by Tukey's and Dunnett's tests (p < 0.05).

Results

There was no significant difference among the IE, IE + SNP, DE + SDF, and DE + SNP groups. The IE + SDF and DE groups recorded the highest and the lowest μ-SBS values, respectively. Adhesive-type failures were the most frequent for all treatments.

Conclusions

Anticaries agents did not have a negative effect on the μ-SBS of composite resin when it was used on IE or DE.

Time-dependent effects after enamel fluoride application on an acid etching system in orthodontic bracket bonding

OBJECTIVES

This study investigated the effectiveness of acid etching and bond strength in an orthodontic bonding system in accordance with various time periods after 1.23% acidulated phosphate fluoride (APF) gel applications.

MATERIALS AND METHODS

APF gel was applied on the enamel surface of bovine teeth, which were assigned to group F0. The tooth specimens were then immersed in distilled water for 1 (F1), 7 (F7), 14 (F14), 21 (F21) and 28 (F28) days. A group without fluoride pretreatment was a control group. All groups were etched with 35% phosphoric acid and evaluated using a surface hardness tester and scanning electron microscope (SEM). A shear bond strength (SBS) test was performed using a universal testing machine, and the bond failure modes were also examined.

RESULTS

After the 1.23% APF gel treatment, the hardness of the acid-etched enamel surface decreased as the immersion period increased. SEM images of the test groups showed etched patterns similar to control group as the immersion period increased. The SBS increased with increasing immersion period, whereas group F21 was not significantly different from the control group. Relatively high adhesive remnant index scores were identified as the ageing period increased.

CONCLUSIONS

The present study indicated that in order to obtain suitable bond strength, it is recommended to use an acid etching-based bonding system for the fixation of orthodontic appliances on the enamel surface 21 days after the use of APF gel.

CLINICAL RELEVANCE

Fluoride pre-treatment interferes with the acid etching effects on enamel, causing a reduction in the bond strength with orthodontic brackets.