Deproteinization of caries-affected dentin with chemo-mechanical caries removal agents and its effect on dentin bonding with self-etch adhesives

Effect of enzymatic chemo-mechanical agents on adhesion of composite resin to dentin of permanent teeth: an in vitro study

PURPOSE

To evaluate and compare the effect of two enzymatic chemo-mechanical caries removal agents with conventional caries removal using rotatory instruments on the adhesion of composite resin to dentin of permanent teeth.

METHODS

The sample comprised 30 permanent molars with caries lesions extending to the dentin, randomly distributed into three groups (n = 10 each): 1-Caries removal with rotary instruments (control group); 2-Caries removal with Papacárie Duo® (F&A Laboratório Farmacêutico, São Paulo, Brazil); 3-Caries removal with Brix 3000™ (Brix S.R.L., Carcarañá, Argentina). After caries removal, the specimens were rinsed and dried. Scotchbond Universal™ adhesive (3 M, Saint Paul, Minnesota, USA) was actively applied in self-etch mode and light-cured. Resin composite increments were applied using a silicone mold (3 × 3 × 2 mm) and light-cured. Shear bond strength (MPa), work-to-debonding (J/m2), and shear modulus (kPa) were evaluated. For statistical analysis, the level of significance was set at 5%.

RESULTS

The control group presented significantly higher shear bond strength values (8.50 ± 2.69 MPa) compared to the Brix 3000™ group (5.72 ± 1.55 MPa, p = 0.008). There were no significant differences between Papacárie Duo® (6.66 ± 0.86 MPa) and the other groups (p > 0.05). Regarding work-to-debonding, the Papacárie Duo® group had a significantly higher result (2944.41 ± 450.21 J/m2) than the Brix 3000™ group (1189.41 ± 504.13 J/m2, p < 0.001) and the control group (967.10 ± 270.01 J/m2, p < 0.001). Concerning shear modulus, the control group showed a significantly higher result (558.67 ± 168.96 kPa) than the Brix 3000™ group (339.79 ± 143.78 kPa, p = 0.008) and the Papacárie Duo® group (223.04 ± 127.30 kPa, p < 0.001).

CONCLUSION

While the application of Papacárie Duo® did not negatively affect composite resin adhesion to dentin of permanent teeth, the application of Brix 3000™ reduced adhesive forces, potentially limiting its clinical use. Further investigations are warranted to elucidate the effects of these materials on dentin substrate, particularly through clinical studies.

Development of a novel papain gel formulation: Exploring different concentrations for smear-layer deproteinization and enhanced dentin bonding

Background

The self-etch adhesive system modifies but does not completely remove the smear layer, leading to the weakening of the bond strength due to the formation of a hybridized layer. Smear-layer deproteinization with papain enzyme partially removes the smear layer, and increases the bond strength with self-etch adhesive. The aim was to develop a deproteinizing agent with a high papain enzyme concentration to enhance dentin bonding with self-etch adhesives.

Methods

Papain enzyme gel formulations (15 and 30 IU/g) were prepared and tested for physical stability, viscosity, pH, homogeneity, and organoleptic properties. Moreover, 64 teeth were used to test the deproteinization efficiency of the formed gel. Fourier transform infrared was used to calculate the ratio of organic to inorganic components of smear-layer after deproteinization with 15 and 30 IU/g papain gel and a 6 IU/g commercial papain gel. Moreover, tensile bond strength was measured after deproteinization and dentin bonding with self-etching adhesive for the same groups. A molecular modeling simulation was also performed to evaluate the protein-protein binding interaction, predict the conformational/orientation patterns, and estimate the binding energies of papain with collagen target protein.

Results

Both 15 and 30 IU/g gels exhibited similar viscosity, pH, homogeneity, and organoleptic properties. However, after 60 s, the 15 IU/g gel was solid, while the 30 IU/g gel was half-solid. All tested groups decreased the amide:phosphate ratio and increased tensile bond strength. Binding complexes between papain and three deposited collagen-1 structures formed strong binding energies with high negative values and residue-wise binding patterns.

Conclusions

The production of the papain enzyme gel with a concentration of 15 IU/g was successful. In addition, it demonstrated promising results when used as a smear-layer deproteinization agent.

Clinical significance

Enzymatic smear-layer deproteinization may improve dentin adhesion, and high concertation papain enzyme gels may improve dentin adhesion with the use of self-etch adhesive.

Effects of Endodontic Irrigants on Shear Bond Strength of Mild Universal Adhesives to Dentin

PURPOSE

The objective of this in vitro study was to evaluate the shear bond strength (SBS) of several universal adhesives to dentin treated with sodium hypochlorite (NaOCl), and NaOCl followed by ethylenediaminetetraacetic acid (EDTA).

MATERIALS AND METHODS

Adhese Universal, Scotchbond Universal, Prime & Bond Elect, Prime & Bond Active, and Optibond XTR were included in the study. SBS values were determined in self-etch mode with no pretreatment of the dentin, after a 20-minute exposure of the dentin to 6% NaOCl, and after a 20-minute exposure to NaOCl followed by a one-minute exposure to 17% EDTA. Experimental groups were repeated using a total-etch technique (except Optibond XTR).

RESULTS

Adhesives in self-etch mode had significantly reduced SBS following dentin exposure to NaOCl (P < .05), while with a total-etch technique, only Prime & Bond Active was affected (P < .05). SBS in self-etch mode when NaOCl exposure was followed by EDTA were equal to or higher than negative control values (P < .05). For total-etch groups, Adhese Universal was negatively affected by NaOCl + EDTA exposure (P < .05). Prime & Bond Elect exhibited lower SBS following NaOCl + EDTA exposure when compared to just NaOCl exposure but was not different from the negative control (P < .05).

CONCLUSION

For the adhesives tested, the use of 17% EDTA following NaOCl exposure negated the negative effects of NaOCl on SBS in self-etch mode. When used in total-etch mode, results varied significantly, with some adhesives performing better or worse depending on the specific testing condition.

Effects of endodontic root canal irrigants on tooth dentin revealed by infrared spectroscopy: a systematic literature review

BACKGROUND

Root canal irrigation endodontic solutions have effects on the chemistry of dentin. Infrared spectroscopy is a non-destructive chemical characterization method where the strength of absorption often correlates with mineral or organic composition.

OBJECTIVES

To survey effects of commonly used irrigation solutions on the composition of root dentin as detected by widely-available Fourier transform infrared spectroscopy (FTIR) methods.

METHODS

Electronic databases were searched for articles published between 1983 to 2023. After risk of bias assessments (OHAT), studies were grouped according to effects per irrigation solution. Inclusion criteria comprised in vitro studies that used extracted human or bovine teeth, treated by irrigation solutions characterized using FTIR spectroscopy and presenting spectral data. Publications that did not present spectra were excluded.

RESULTS

A wide range of concentrations, durations, and treatment protocols have been tested but only 30 out of 3452 studies met our inclusion criteria. Different FTIR methods were used with Attenuated Total Reflection (ATR) variant being the most common (21 studies). Investigated solutions included sodium hypochlorite (NaOCl), ethylenediaminetetraacetic-acid (EDTA), 1-hydroxyethylidene-1-1-diphosphonic-acid (HEDP), peracetic-acid (PAA), glycolic-acid (GA), and citric-acid (CA) though most focused on NaOCl and EDTA. All solutions had detectable effects in the FTIR signature of dentin. NaOCl mainly affects the organics, revealing reduced amide/phosphate ratios with increasing concentrations. EDTA mainly effects the inorganic component, with the effects increasing with time and concentration, yet glycolic acid has stronger effects than EDTA on dentin. Beyond the type of irrigant and dentin exposure durations, concentration and protocol of application had strong effects. There is a lack of studies comparing similar irrigants under conditions that mimic clinical scenarios analyzing bulk sample because FTIR of powder dentin differs from FTIR of bulk dentin.

SIGNIFICANCE

The ideal root-canal irrigant should combine local disinfection properties with minimal compositional effects on healthy dentin. FTIR methods appear reliable to identify important changes in root dentin chemical composition. Such information can help understand when endodontic irrigation might lead to root degradation or possibly contribute to long term failures such as vertical fractures. Awareness of chemical damage from irrigation procedures may help clinicians select procedures that reduce deleterious effects on the root canal structures.

Reliability of an Innovative Slab Shear versus Microtensile Bond Strength Test: Mechanical and Finite Element Analysis

OBJECTIVE

 The aim of this study was to evaluate the efficiency of slab shear bond strength test (Slab_SBS) versus the microtensile in evaluation of the bond strength of different substrates.

MATERIALS AND METHODS

 Forty-eight extracted caries-free human third molars were utilized for teeth specimens' preparation. After flattening of all molars' occlusal table, the specimens were divided into two groups based on the type of utilized restorative material: nanohybrid resin composite and resin-modified glass ionomer (RMGI). Each group was further subdivided into three subgroups according to the subsequently applied bond strength test and specimen width; microtensile bond strength test (μTBS), Slab_SBS [2 mm] and Slab_SBS [3 mm]. Both testing methods were additionally applied on CAD/CAM specimens, nanohybrid resin composite blocks (composite-to-composite), and ceramic blocks (ceramic-to-ceramic). CAD/CAM specimens were prepared and cemented and then sectioned and subdivided as followed for teeth specimens' preparation. Pretest failures (PTF), bond strength, and failure mode of each specimen were recorded. Representative three-dimensional (3D) finite element analysis (FEA) models were developed to simulate μTBS and Slab_SBS specimens. Data were statistically analyzed using Shapiro-Wilk test and Weibull analysis.

RESULTS

 Pretest failures were only noted in the μTBS subgroups. Slab_SBS provided comparable bond strength to the μTBS of all substrates with adhesive mode of failure.

CONCLUSION

 Slab_SBS is easier to prepare with consistent and predictable outcome with no pretest failures during specimen preparation and better stress distribution.

Enhanced Bonding to Caries-Affected Dentin Using an Isocyanate-Based Primer

Dental caries is the most common oral disease and the most common cause of resin restorations. In minimally invasive dentistry, the principle behind cavity preparation is to remove external caries-infected dentin (CID) and preserve internal caries-affected dentin (CAD) and sound dentin (SD). The cavity floor is mainly composed of CAD, but the poor bonding performance of CAD has become a widespread concern. This study evaluated the performance of a new collagen-reactive monomer (ITCM) used as a primer to improve the bonding performance of CAD. The experimental specimens were grouped as follows: SD, CAD, and ITCM-pretreated CAD (CAD-ITCM). Dentin slices were obtained for attenuated total reflectance-Fourier transform infrared (ATR-FTIR) analysis. The bonded samples were subjected to microtensile bond strength analysis after 24 h of water storage or aging by thermocycling, and the bonding interface quality was evaluated by nanoleakage assessment, interfacial nanoindentation testing, and in situ zymography. Cytotoxicity experiments with ITCM were performed. ATR-FTIR showed that the isocyanate groups in ITCM can covalently bind and form hydrogen bonds with the collagen in CAD to mediate chemical bonding. ITCM pretreatment significantly improved the bond strength of CAD (P < 0.05), reduced interfacial nanoleakage, improved the sealing of the bonding interface, enhanced the homogeneity of the hybrid layer, and inhibited matrix metalloproteinase activity. In addition, ITCM presented acceptable biocompatibility for dental restorative application. Taken together, this study reported the application of ITCM to induce collagen-based chemical bonding in the CAD bonding system, which fills the gap in strategies to improve the bonding performance of CAD immediately and after aging and has important clinical application prospects.

Evaluation of different decontamination procedures on bond strength to sound and caries affected dentin using "no-wait" universal adhesive

BACKGROUND

Current study aimed to evaluate the effect of different decontamination procedures on micro-shear bond strength (μSBS) of sound (SoD) and caries-affected dentin (CAD) of two universal adhesives after blood-saliva contamination.

METHODS

One hundred and eighty bovine anterior teeth were prepared and allocated into the respective groups according to tested dentin substrates [SoD, CAD], universal adhesives [Clearfil Bond Universal Quick (UBQ), All-Bond-Universal (ABU)], adhesive contamination stage [none, contamination before and after adhesives light-curing], and according to decontamination procedures [no decontamination, water rinsing, adhesive rebond, Ethylenediaminetetraacetic acid (ETDA) and chlorhexidine (CHX) application]. Universal adhesives were applied according to manufacturer instructions in self-etch (SE) bonding mode. Four composite microrods were built for each tooth. Specimens were kept in distilled water for 24 hours at 37°C before testing μSBS. Four-way ANOVA and Tukey HSD tests were used for data analysis.

RESULTS

A statistically significant difference between contamination stages of both universal adhesives at different decontamination procedures for SoD and CAD. Highest μSBS was recorded for UBQ control group at SoD, while the least was recorded for light-cured ABU upon water rinsing decontamination procedure of CAD.

CONCLUSIONS

Proper cavity isolation is mandatory to avoid possible contamination which can dramatically affect μSBS. CHX is a potent cavity decontaminant that can restore different dentin substrates bond strength. EDTA presents a promising substitute. UBQ adhesive showed better bonding performance than ABU to both dentin substrates. Application of regular cavity decontamination approaches is highly advised in daily practice to avoid possible detrimental effect of accidental cavity contamination.

Comparison of Different Dentin Deproteinizing Agents on Bond Strength and Microleakage of Universal Adhesive to Dentin

Aim:

To evaluate the effects of papain (Brix 3000), bromelain, sodium hypochlorite (NaOCl), and chlorine dioxide (ClO2) application to the deep dentin surface on shear bond strength (SBS), microleakage, and dentin surface properties.

Materials and Methods:

Deep dentin surface ( n = 100) for evaluating SBS, class V preparation at the buccal surface for testing microleakage ( n = 100), and deep dentin slices ( n = 20) for evaluating surface properties were conducted on the 220 molar teeth. Four different deproteinizing agents (Brix 3000, 40% bromelain, 5.25% NaOCl (Chloraxid), and 0.12% ClO2) were applied to the dentin, and then the universal adhesive was used in self-etch (SE) and etch&rinse (E&R). Deproteinizing agents were not applied to the control group. All of the samples were subjected to 5000 cycles of thermal aging at 5ºC–55ºC. SBS (MPa) was tested by a universal testing machine. The microleakage of resin composite bonded with different adhesive modes was evaluated under a stereomicroscope. The changes in the surface morphology were examined with scanning electron microscopy (SEM) and attenuated total reflection – fourier transform infrared spectroscopy (ATR-FTIR).

Results:

ClO2 exhibited the highest bond strength among deproteinizing agents. Compared to the SE mode, E&R mode significantly showed higher bond strength ( p < .05). In gingival margin, bromelain SE exhibited the highest marginal leakage, while Brix 3000 SE had the lowest mean microleakage score.

Conclusion:

Deproteinizing with ClO2 was effective in improving the SBS of universal adhesive in the E&R mode to deep dentin. Deproteinization with bromelain before universal adhesive in SE mode showed more microleakage on both the occlusal and gingival surfaces.

Efficacy of combined chemical and electrochemical decontamination treatments on contaminated healing abutments and their effect on surface topography: An in vitro study

OBJECTIVE

To evaluate the efficacy of four decontamination protocols on contaminated healing abutments (HAs) and their effects on surface topography.

METHODS

Eighty contaminated single-use HA samples collected from human participants were stained with phloxine B and examined microscopically. The retrieved HAs were randomly divided into four test groups: (1) Autoclaving only (AU), (2) 5.25% sodium hypochlorite (NaOCl) + AU, (3) Electrochemical treatment (EC) + AU, (4) NaOCl + EC + AU, and positive control (contaminated without any treatment). Four new unused HAs served as negative controls (NC). The surface features were analyzed using stereo microscopy (SM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and optical profilometry.

RESULTS

The lowest decontamination efficacy was observed for the AU group. The NaOCl + AU and EC + AU groups effectively removed residual contamination, whereas EC + AU showed better decontamination results than NaOCl + AU. SM, SEM, and EDS analyses revealed the best decontamination efficacy in the combined NaOCl + EC + AU group compared to the other groups. Surface roughness (Sa), developed surface area ratio (Sdr), and texture-aspect ratio (Str) in AU, NaOCl + AU, EC + AU, and NaOCl + EC + AU groups were not statistically significant compared to the NC group.

CONCLUSIONS

The combination of NaOCl with subsequent EC can remove soft and hard deposits from the surface of HAs compared to NaOCl alone and EC alone, without altering the surface topography of HAs.

Addition of metal chlorides to a HOCl conditioner can enhance bond strength to smear layer deproteinized dentin

OBJECTIVES

To evaluate the effect of smear layer deproteinization using hypochlorous acid (HOCl) with/without metal chlorides (SrCl₂ and ZnCl₂) on the microtensile bond strength (µTBS) of two simplified adhesives to dentin.

METHODS

Human dentin surfaces with a standardized smear layer were pretreated using a 105 ppm HOCl solution with/without SrCl₂ (0.05 M, 0.1 M, 0.2 M, 0.4 M) or ZnCl₂ (0.05 M, 0.1 M, 0.2 M) for 5 s, 15 s, or 30 s. After the deproteinizing solution was washed out with water for 5 s, 15 s, or 30 s, pretreated surfaces were bonded with one-step self-etch adhesive Bond Force II or universal adhesive Clearfil Universal Bond Quick, and µTBS was measured after 24 h. Additionally, the deproteinizing effects of HOCl solutions with/without the metal chlorides were compared by measuring changes in the amide:phosphate ratio using attenuated total reflection Fourier transform infrared spectroscopy. Statistical analysis was performed using multifactor ANOVA, Tukey's post hoc tests and t-tests (p < 0.05).

RESULTS

Pretreatment with pure HOCl for 15 s and 30 s significantly decreased the amide:phosphate ratio (p < 0.05), indicating effective deproteinization, but the µTBS of both adhesives increased significantly only if HOCl was washed out for 30 s (p < 0.05). Increasing the concentrations of metal chlorides enabled shortening of the wash-out time down to 5 s while maintaining the improved µTBS (p < 0.05). The deproteinizing effect of HOCl was not significantly altered by the addition of metal chlorides (p > 0.05).

SIGNIFICANCE

The effectiveness of smear layer deproteinization using HOCl can be improved by the addition of metal chlorides, as their increasing concentration allowed to shorten the wash-out time from 30 s down to 5 s.