Marginal seal and biocompatibility of a fourth-generation bonding agent

Interaction effect of Nd:YAG laser and universal adhesive system for dentin sealing

Background

To evaluate the influence of the association of the universal adhesive system to different energy densities of the Nd:YAG laser on the hydraulic conductance of dentin.

Material and Methods

Fifty bovine dentin discs were made. The samples were stratified into four groups (n = 10) according to the treatment performed; SBU- Adper Single Bond Universal (3M ESPE), SBU_60 - SBU associated with the Nd:YAG laser (60mJ, 10Hz, 0.6W - 47.77 J / cm²), SBU_80 - SBU associated with the Nd:YAG laser (80mJ, 10Hz, 0.8 W - 63.69 J / cm2) and C – dentin without treatment (smear layer). Hydraulic conductance measurements were taken 24 hours after the treatments (HC1) and after erosive challenge (HC2). Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDX) helped to visualize the dentin after the different treatments. Scheffe and Games-Howell statistical tests were used to analyze hydraulic conductance (α = 0.05).

Results

The treated dentin (SBU, SBU_60, and SBU_80) reduced HC1 when compared to dentin with smear layer (C) (p< 0.001). The erosive challenge has increased HC2 in SBU_60 and C (p< 0.001), and did not promote a significant difference in SBU_80 and SBU. The SEM / EDX analyzes showed an irregular and semi-permeable barrier on the surfaces of the treated dentin.

Conclusions

The association of universal adhesive with Nd:YAG can be an effective alternative for the occlusion of dentinal tubules, whereas higher energy per pulse Nd:YAG (SBU_80) can increase the resistance to permeability when exposed to the erosive challenge.

Key words:Dentin, permeability of dentin, Nd:YAG Laser, adhesives.

The effect of cavity disinfectants on the sealing ability of dentin bonding system: An in vitro study

Aim:

This study was conducted to determine the effect of three cavity disinfectants (chlorhexidine gluconate based-Consepsis; benzalkonium chloride-based Tubulicid Red, iodine-potassium iodide/copper-sulphate based Ora-5) on the microleakage of a dentin bonding system, Clearfil SE Bond.

Materials and Methods:

Class V cavities were prepared on 45 extracted molars. The respective experimentalgroups were treated with cavity disinfectants and Clearfil SE Bond. Preparations without cavity disinfectants served as negative control and those with neither disinfectant nor dentin bonding resin application served as positive controls. After the cavity preparations were restored with resin composite (Clearfil APX), the specimens were subjected to dye penetration. Statistical analysis was performed using ANOVA (Kruskal-Wallis) test.

Results:

Unlike Conspesis and Tubulicid Red, Ora-5 exhibited significantly higher microleakage and adversely affected the sealing ability of Clearfil SE bond. Only Consepsis and Tubulicid Red could be used as cavity disinfectants with Clearfil SE bond, without its sealing abilities being adversely affected.

Conclusions:

1) Consepsis and Tubulicid Red can be used as cavity disinfectants with Clearfil SE Bond, without the sealing ability of Clearfil SE bond being affected. 2) Ora-5 is not an appropriate disinfectant to be used with this dentin bonding system, because it alters its sealing ability.

Polyethyleneimine nanoparticles incorporated into resin composite cause cell death and trigger biofilm stress in vivo

Incorporation of cross-linked quaternary ammonium polyethylenimine (QPEI) nanoparticles in dental resin composite has a long-lasting and wide antimicrobial effect with no measured impact on biocompatibility in vitro. We hypothesized that QPEI nanoparticles incorporated into a resin composite have a potent antibacterial effect in vivo and that this stress condition triggers a suicide module in the bacterial biofilm. Ten volunteers wore a removable acrylic appliance, in which two control resin composite specimens and two resin composite specimens incorporating 1% wt/wt QPEI nanoparticles were inserted to allow the buildup of intraoral biofilms. After 4 h, the specimens were removed and tested for bacterial vitality and biofilm thickness, using confocal laser scanning microscopy. The vitality rate in specimens incorporating QPEI was reduced by > 50% (p < 0.00001), whereas biofilm thickness was increased (p < 0.05). The ability of the biofilm supernatant to restore bacterial death was tested in vitro. The in vitro tests showed a 70% decrease in viable bacteria (p < 0.05). Biofilm morphological differences were also observed in the scanning electron microscope micrographs of the resin composite versus the resin composite incorporating QPEI. These results strongly suggest that QPEI nanoparticles incorporated at a low concentration in resin composite exert a significant in vivo antibiofilm activity and exhibit a potent broad spectrum antibacterial activity against salivary bacteria.

Evaluation of internal adaptation of Class V resin composite restorations using three techniques of polymerization

OBJECTIVE

The purpose of this in vitro study was to evaluate the internal adaptation of Class V composite restorations to the cavity walls using three different techniques of polymerization.

METHODS

Standard cavities were prepared on the buccal and lingual surfaces of 24 extracted human third molars with margins located above and below the cementoenamel junction. Restorations were placed in one increment using two restorative systems: 3M Filtek A110/ Single Bond (M) and 3M Filtek Z250/ Single Bond (H) in the same tooth, randomly in the buccal and lingual surfaces. Resin composites were polymerized using three techniques: Group 1 - Conventional (60 s - 600 mW/cm(2)); Group 2 - Soft-start (20 s - 200 mW/cm(2) , 40 s - 600 mW/cm(2)); Group 3 - Pulse Activation (3 s - 200 mW/cm(2), 3-min hiatus, 57 s - 600 mW/cm(2)). Buccolingual sections were polished, impressions taken and replicated. Specimens were assessed under scanning electron microscopy up to X1000 magnification. Scores were given for presence or absence of gaps (0 - no gap; 1 - gap in one wall; 2 - gap in two walls; 3 - gap in three walls).

RESULTS

The mean scores of the groups were (+/-SD) were: G1M-3.0 (+/- 0.0); G2M-2.43 (+/- 0.8); G3M- 1.71 (+/- 0.9); G1H- 2.14 (+/- 1.2); G2H- 2.00 (+/- 0.8); G3H- 1.67 (+/- 1.1). Data were analyzed using Kruskal-Wallis and Dunnet's tests. No statistically significant difference (p>0.05) was found among groups. Gaps were observed in all groups.

CONCLUSIONS

The photocuring technique and the type of resin composite had no influence on the internal adaptation of the material to the cavity walls. A positive effect was observed when the slow polymerization techniques were used.

Molecular toxicology of substances released from resin-based dental restorative materials

Resin-based dental restorative materials are extensively used today in dentistry. However, significant concerns still remain regarding their biocompatibility. For this reason, significant scientific effort has been focused on the determination of the molecular toxicology of substances released by these biomaterials, using several tools for risk assessment, including exposure assessment, hazard identification and dose-response analysis. These studies have shown that substances released by these materials can cause significant cytotoxic and genotoxic effects, leading to irreversible disturbance of basic cellular functions. The aim of this article is to review current knowledge related to dental composites' molecular toxicology and to give implications for possible improvements concerning their biocompatibility.

Effect of an antibacterial adhesive on the bond strength of three different luting resin composites

OBJECTIVES

Effect of a dentin adhesive system containing antibacterial monomer-MDPB (Clearfil Protect Bond) on the shear bond strength of all-ceramic-IPS Empress 2 restorations luted with three different dual-polymerizing systems (Variolink 2, RelyX ARC and Panavia F 2.0) to dentin was investigated.

METHODS

One hundred and eight all-ceramic discs (2 x 3mm; IPS Empress 2) were fabricated and ultrasonically cleaned. The buccal surfaces of 108 non-carious extracted human premolars were flattened to expose dentin and subsequently polished with 600-grit wet silicon carbide paper. Three dual-polymerizing luting systems had test groups and control groups consisting of 18 samples each. For the test groups Clearfil Protect Bond was applied to the exposed dentin surfaces. Control groups received the original bonding procedures of each adhesive system. After the all-ceramic samples were luted to the teeth, thermocycling was performed 5000 times. Shear bond strengths were tested using Shimadzu Universal Testing Machine until failure. Analysis of fractured dentin surfaces were performed using Optical Microscope at x10 and x1000 magnifications and the images were analyzed with Image Analyzer. Data was analyzed with one-way ANOVA and Bonferroni test at a significance level of p<0.05.

RESULTS

Mean shear bond strength data of the groups in MPa were; Variolink: 20.45+/-4.75, Variolink+Clearfil Protect Bond:29.32+/-2.37, RelyX ARC:18.82+/-3.19, RelyX ARC+Clearfil Protect Bond:25.58+/-4.05, Panavia F 2.0:17.11+/-2.98, Panavia F 2.0+Clearfil Protect Bond:24.40+/-7.46. Application of the antibacterial adhesive increased the shear bond strengths of all three dual-polymerizing systems to dentin (p=0.00). The surface analysis showed that most of the specimens showed the adhesive failure mode between the dentin and the composite luting agent interface.

CONCLUSION

The antibacterial adhesive system Clearfil Protect Bond can be safely used to prevent the potential risk of complications resulting from bacterial activity regardless of affecting the bond strength of IPS Empress 2 restorations luted with the dual-polimerizing systems used in this study.

Dentin adhesion and microleakage of a resin-based calcium phosphate pulp capping and basing cement

An experimental resin-based bioactive calcium phosphate cement, intended as a pulp capping and basing material, was evaluated for dentin shear bond strength and microleakage. The interfacial morphology was examined by scanning electron microscopy (SEM). For microleakage, dentin cavities without (Group A) or after (Group B) acid etching were restored with the calcium phosphate cement. A resin-based calcium hydroxide (VLC Dycal; Group C) was used as control material according to the manufacturer's instructions. After water storage and thermocycling, the microleakage was scored using a AgNO(3) staining procedure. For the shear bond strength, flat exposed dentin surfaces were treated as for the microleakage test. Metal irises pressed against the dentin surface were filled with the cements, which were photocured. Both tests were carried out after 1 wk. While acid etching did not result in significantly greater microleakage, it led to higher shear bond strength, and allowed, as shown by SEM, the formation of a hybrid layer and resin tags. Both groups treated with the calcium phosphate cement had significantly lower microleakage scores and higher mean shear bond strength values than the groups treated with the control material.

Antibacterial activity and bonding characteristics of an adhesive resin containing antibacterial monomer MDPB

OBJECTIVES

The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability.

METHODS

An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy.

RESULTS

The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control (p>0.05), and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different (p>0.05) between control and experimental adhesive irrespective of addition of MDPB into primer.

SIGNIFICANCE

These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB-containing primer and adhesive should be highly effective in its antibacterial effect before and after curing.

Antibacterial activity of fifth-generation dentin bonding systems

Past concepts that the pulp does not become infected until an actual carious exposure takes place have been challenged. The antibacterial effects of the dentin bonding systems Single Bond, Prime&Bond NT, and Excite were evaluated using the bacteria Streptococcus mutans ATCC 25175, Streptococcus intermedius, Lactobacillus acidophilus, Prevotella oris, Prevotella bivia, Prevotella denticola, Porphyromonas gingivalis, Porphyromonas endodontalis, and Clostridium ramosum with a disk diffusion method. Chlorhexidine (0.2%) was used as a positive control. After incubation zones of inhibited bacterial growth were measured. Prime&Bond NT showed growth inhibition for all bacterial strains. Lactobacillus acidophilus and Streptococcus mutans were remarkably resistant to Single Bond, whereas EX produced no inhibitory effect on Porphyromonas endodontalis, although the adhesive produced the maximum halo inhibition to Streptococcus mutans (15+/-1 mm), showing an antibacterial effect closest to chlorhexidine. The variety of results obtained in this study suggest that antibacterial properties of current dentin adhesives may depend on components that are originally incorporated to promote adhesion.

Evidence for bacterial causation of adverse pulpal responses in resin-based dental restorations

The widespread use of resin and resin-monomers for bonding of dental restorations to dentin has occurred because of a fundamental shift in the view that injury to the pulp is induced by restorative procedures. While, for many years, the toxic effects of restorative materials were thought to be of crucial importance in the development of adverse pulpal responses, the key role of bacterial leakage at the restoration-tooth interface is now well-recognized. Consequently, if optimal conditions for the preservation of pulpal health are to be ensured, dental restorations should provide an impervious seal against the surrounding tooth structure. However, polymerization shrinkage and contraction stresses induced during setting, as well as a variety of technical difficulties encountered during the clinical operation, often produce less than perfect results. Therefore, modern restorative procedures involving resin and resin-bonded restoratives must still rely on the ability of the pulp to cope with the injurious elements to which it may be exposed during and after the procedure. This review examines factors that may govern the pulp's response to restorative procedures that involve adhesive technologies. An assessment is made of the risks involved as far as the continued vital function of the pulp is concerned. It is concluded that an intact, although thin, wall of primary dentin often enables the pulp to overcome both toxic material effects and the influences of bacterial leakage. In contrast, the pulp may not do equally well following capping of open exposures with resin composites. A dearth of controlled clinical studies in this area of dentistry calls for confirmation that pulpal health prevails over the long term following the use of total-etch and resin-bonding techniques.

Biocompatibility of resin-modified filling materials

Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased significantly. It has been found that each resin-based material releases several components into the oral environment. In particular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacrylate (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomer cements [GICs] and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerous unbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradation or erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adverse systemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotected skin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of dental nurses, technicians, and dentists who present with allergic reactions to one or more resin components, like HEMA, glutaraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that, except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce. There is very little reliable information with respect to the biological interactions between resin components and various tissues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp. Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materials be clarified in the near future.

Human pulp reaction to dentine bonded amalgam restorations: a histologic study

OBJECTIVE

The aim of this study was to investigate the human pulp response to Scotchbond Multi Purpose Plus (SMPP) bonding agent in non-exposed Class V cavities.

METHODS

SMPP was placed in 24 of 40 cavites according to manufacturer's instructions and the cavities were restored with amalgam. The remaining 16 cavities were capped with a calcium hydroxide formulation (Dycal) sealed with zinc-oxide eugenol, and restored with the amalgam. After extraction at 10 and 35 days, the teeth were fixed, sectioned and stained for light microscopy.

RESULTS

All Dycal-capped teeth, at both 10 and 35 days, exhibited no pulp inflammation and no demonstrable bacteria. Six cases sealed with SMPP at 10 days showed no pulp inflammation or stained bacterial profiles. The remaining six teeth demonstrated mild to moderate inflammatory pulpal responses and five out of these six cases exhibited stained bacterial profiles. Nine out of 12 teeth showed no inflammatory pulp responses at 35 days, the remaining three cases exhibited mild to moderate pulp inflammation without stained bacteria.

CONCLUSIONS

None of the teeth sealed with SMPP presented severe inflammatory pulpal reactions histologically. SMPP did not exhibit significant deleterious effects on the human pulp tissue during the test periods.

Aqueous extracts from dentin adhesives contain cytotoxic chemicals

It was the aim of our study to investigate the composition and cytotoxicity of aqueous elutes from five dentin adhesives currently used in clinical practice: Solobond Plustrade mark, Solisttrade mark, Scotchbond Multipurposetrade mark, Syntac SCtrade mark, and Prime & Bondtrade mark 2.1. Water extracts were analyzed by gas chromatography/mass spectrometry (GC/MS) and relative quantities of identified compounds were compared by means of an internal caffeine standard [%CF]. The in vitro cytotoxic effects of substances released into DMEM were determined using immortalized 3T3-fibroblast cultures. In addition, the cytotoxicity of ethylene glycol (EG), which was identified in the extracts of Syntac SC, was evaluated. All dentin adhesives tested released various chemical components, like comonomers (mainly ethylene glycol compounds), HEMA, and initiating substances (e.g., camphorquinone). Elutes of Solobond Plus, which contained very high amounts of TEGDMA, were extremely cytotoxic. Two bonding agents (Scotchbond Multi-purpose, Syntac SC), which released significant quantities of HEMA, induced severe cytotoxic effects. In contrast, extracts from Solist and Prime & Bond 2.1 had very small effects on cell proliferation; these elutes contained small amounts of released chemical compounds. EG, a product of HEMA hydrolysis, in concentrations ranging from 0.025-25 mM was not cytotoxic. In summary, these results provide evidence that all dentin adhesives tested in the present study release in aqueous media chemical compounds some of which (for example, TEGDMA and HEMA) are cytotoxic.

Effects of direct resin pulp capping techniques on short-term response of mechanically exposed pulps

The aim of this in vivo study was to evaluate the effects of direct pulp capping techniques on the short-term response of mechanically exposed pulps using three commercially available adhesive resin systems. Class V cavities were prepared on the facial surface of 200 intact monkey teeth. Pulps were exposed with a carbide bur on the cavity floor. Each exposed pulp was capped with one of three commercially available adhesive resins or a hard-setting calcium hydroxide liner. All cavities were sealed with an adhesive resin, and were restored with hybrid resin composites. Inflammatory cell infiltration and dentine bridging of the exposed pulp and protrusion of the exposed pulp tissue into the cavities were evaluated histologically at 3, 7, 14, 30 and 60 days. A slight inflammatory cell infiltration was the principal reaction of the exposed pulp. The exposed area was occluded over time with dentine bridging in all groups. However, a protrusion of pulp tissue into the prepared cavity was observed at the periphery of the exposed area in all groups. These tissues communicated with the underlying pulp. The incidence of pulp tissue protrusion was ranked in order of increasing severity: Liner Bond II < Dycal < Bondwell LC = Super Bond C&B. Following pulp capping of the mechanical exposures, slight inflammation was the main reaction. Exposures became occluded with a dentine bridge over time. However, the protrusion of pulp tissue into cavities varied, depending on the materials used.

Review of dental materials citations: Part B, July to December 1995

OBJECTIVE

A lag of many months occurs between journal issue publication and updates to electronic databases. The objective of this literature analysis was to identify and categorize all of the dental materials citations in biomedical journals that were published from July 1995 through December 1995.

METHODS

Seventeen primary and 51 secondary journals were searched using their tables of contents to detect and record dental materials publications from July to December of 1995. Those journals that were typically rich in dental materials articles were classified as primary ones. Citations were categorized into 17 topics and divided into subsections. The review excluded case reports, most literature related primarily to dental implants, and most articles on biomedical materials used outside of the field of general dentistry.

RESULTS

The greatest number of citations was related to topics of dentin bonding and resin-based restorative filling materials (composites and glass ionomers). There was no major change in the number of dental materials publications per year reported from 1993 (n = 786) to 1995 (n = 751).

SIGNIFICANCE

This citation list provides a comprehensive resource for use by academicians and researchers to bridge the gap between initial publication and access to electronic searching methods for major databases.