Classification review of dental adhesive systems: from the IV generation to the universal type

Adhesive dentistry has undergone great progress in the last decades. In light of minimal-invasive dentistry, this new approach promotes a more conservative cavity design, which relies on the effectiveness of current enamel-dentine adhesives. Adhesive dentistry began in 1955 by Buonocore on the benefits of acid etching. With changing technologies, dental adhesives have evolved from no-etch to total-etch (4^th and 5^th generation) to self-etch (6^th, 7^th and 8^th generation) systems. Currently, bonding to dental substrates is based on three different strategies: 1) etch-and-rinse, 2) self-etch and 3) resin-modified glass-ionomer approach as possessing the unique properties of self-adherence to the tooth tissue. More recently, a new family of dentin adhesives has been introduced (universal or multi-mode adhesives), which may be used either as etch-and-rinse or as self-etch adhesives. The purpose of this article is to review the literature on the current knowledge for each adhesive system according to their classification that have been advocated by many authorities in most operative/restorative procedures. As noted by several valuable studies that have contributed to understanding of bonding to various substrates helps clinicians to choose the appropriate dentin bonding agents for optimal clinical outcomes.

Telechelic poly(2-oxazoline)s with a biocidal and a polymerizable terminal as collagenase inhibiting additive for long-term active antimicrobial dental materials

Dental repair materials face the problem that the dentin below the composite fillings is actively decomposed by secondary caries and extracellular proteases. To address this problem, poly(2-methyloxazoline) with a biocidal and a polymerizable terminal was explored as additive for a commercial dental adhesive. 2.5 wt% of the additive rendered the adhesive contact-active against Streptococcus mutans and washing with water for 101 d did not diminish this effect. The adhesive with 5 wt% additive kills S. mutans cells in the tubuli of bovine dentin. Further, the additive inhibits bacterial collagenase at 0.5 wt% and reduces activity of MMP-9. Human MMPs bound to dentin are inhibited by 96% in a medium with 5 wt% additive. Moreover, no adverse effect on the enamel/dentine shear bond strength was detected.

Morphological evaluation of new total etching and self etching adhesive system interfaces with dentin

Aim:

The purpose of this study is to evaluate the resin-dentin interface, quality of the hybrid layer of total-etching and self-etching adhesive systems under scanning electron microscopy (SEM).

Materials and Methods:

Class V cavities were prepared in 40 extracted human molars. In Group I XP bond (Dentsply), in Group II Adper Single Bond II (3M ESPE), in Group III Adper Easy One (3M ESPE), and in Group IV Xeno V (Dentsply) were applied. Teeth were restored with resin composite, subjected to thermocycling, and sectioned in Buccolingual plane. The samples were demineralized using 6N HCl, for 30 sec, and deproteinized with 2.5% NaOCl for 10 min, gold sputtered, and viewed using a scanning electron microscope.

Results:

Among the total-etch systems used, the XP Bond showed a clear, thick hybrid layer, with long resin tags and few voids. Among the self-etch adhesive systems, the Xeno V did not show a clearly recognizable hybrid layer, but there were no voids and continuous adaptation was seen with the dentin.

Conclusion:

The adaptation of self-etch adhesives to the resin-dentin interface was good without voids or separation of phases; showing a thin, continuous hybrid layer.

Immediate enamel bond strength of universal adhesives to unground and ground surfaces in different etching modes

The purpose of this study was to determine the immediate bond effectiveness of universal adhesives to unground and ground enamel surfaces in different etching modes, through shear bond strength (SBS) tests and scanning electron microscopy observations. Three universal adhesives, a conventional two-step self-etch adhesive, and a conventional single-step self-etch adhesive were compared. Human enamel specimens from lower anterior teeth were divided into four groups and subjected to the following treatments: (i) unground enamel in self-etch mode; (ii) ground enamel in self-etch mode; (iii) unground enamel in etch-&-rinse mode; and (iv) ground enamel in etch-&-rinse mode. Bonded assemblies were subjected to SBS testing. All the adhesives showed significantly higher SBS values in etch-&-rinse mode than in self-etch mode, regardless of whether enamel was unground or ground. The influence of the enamel surface condition on SBS was different in different etching modes. Without pre-etching, all tested materials showed lower SBS values in unground enamel than in ground enamel. In etch-&-rinse mode, no significant differences in SBS values were observed between unground enamel and ground enamel for any of the adhesives tested. Phosphoric acid pre-etching before application of self-etch adhesives to an unground enamel surface is essential to enhance initial enamel bond effectiveness.

Luting of CAD/CAM ceramic inlays: direct composite versus dual-cure luting cement

The aim of this study was to investigate bonding effectiveness in direct restorations. A two-step self-etch adhesive and a light-cure resin composite was compared with luting with a conventional dual-cure resin cement and a two-step etch and rinse adhesive. Class-I box-type cavities were prepared. Identical ceramic inlays were designed and fabricated with a computer-aided design/computer-aided manufacturing (CAD/CAM) device. The inlays were seated with Clearfil SE Bond/Clearfil AP-X (Kuraray Medical) or ExciTE F DSC/Variolink II (Ivoclar Vivadent), each by two operators (five teeth per group). The inlays were stored in water for one week at 37°C, whereafter micro-tensile bond strength testing was conducted. The micro-tensile bond strength of the direct composite was significantly higher than that from conventional luting, and was independent of the operator (P<0.0001). Pre-testing failures were only observed with the conventional method. High-power light-curing of a direct composite may be a viable alternative to luting lithium disilicate glass-ceramic CAD/CAM restorations.

Shear bond strength and SEM morphology evaluation of different dental adhesives to enamel prepared with ER:YAG laser

CONTEXT

Early observations of enamel surfaces prepared by erbium lasers motivated clinicians to use laser as an alternative to chemical etching.

AIMS

Evaluate shear bond strength (SBS) values of different dental adhesives on Erbium:Yttrium Aluminum Garnet (Er:YAG) laser prepared enamel and to evaluate possible etching patterns correlations between dental adhesives and SBS values.

SUBJECTS AND METHODS

One hundred bovine incisors were randomly assigned to SBS tests on enamel (n = 15) and to enamel morphology analysis (n = 5) after Er:YAG laser preparation as follows: Group I - 37% phosphoric acid (PA)+ ExciTE(®); Group II - ExciTE(®); Group III - AdheSE(®) self-etching; Group IV - FuturaBond(®) no-rinse. NR; Group V - Xeno(®) V. Teeth were treated with the adhesive systems and subjected to thermal cycling. SBS were performed in a universal testing machine at 5 mm/min.

STATISTICAL ANALYSIS USED

One-way ANOVA and post-hoc tests (P < 0.05). For the morphology evaluation, specimens were immersed in Ethylenediamine tetraacetic acid (EDTA) and the etching pattern analyzed under Scanning Electron Microscope (SEM).

RESULTS

Mean bond strengths were Group I - 47.17 ± 1.61 MPa (type I etching pattern); Group II - 32.56 ± 1.64 MPa, Group III - 29.10 ± 1.34 MPa, Group IV - 23.32 ± 1.53 MPa (type III etching pattern); Group V - 24.43 MPa ± 1.55 (type II etching pattern).

CONCLUSIONS

Different adhesive systems yielded significantly different SBSs. Acid etching significantly increased the adhesion in laser treated enamel. No differences in SBS values were obtained between AdheSE(®) and ExciTE(®) without condition with PA. FuturaBond(®) NR and Xeno(®) V showed similar SBS, which was lower in comparison to the others adhesives. No correlation between enamel surface morphology and SBS values was observed, except when PA was used.

How "Universal" is Adhesion? Shear Bond Strength of Multi-mode Adhesives to Enamel and Dentin

PURPOSE

The purpose of this in vitro study was to compare the shear bond strength of different universal adhesives to enamel and dentin with and without additional phosphoric acid etching before and after thermocycling (TC).

MATERIALS AND METHODS

The mesial, distal, lingual, and buccal surfaces of the teeth were ground flat to expose two enamel areas and two dentin areas. Specimens were randomly divided into 36 groups (n = 10). Four adhesives were tested: Scotchbond Universal (SBU), Prime & Bond Elect (PBE), All-Bond Universal (ABU), and iBond Universal (IBU). The application was performed in the self-etch mode (SE) or in the etch-and-rinse mode (ER). Optibond FL (OFL) was used as an etch-and-rinse control. After composite buildups were made, half of the groups were tested before and the other half after TC. The failure mode was evaluated using a light microscope.

RESULTS

In enamel, mean bond strengths ranged from 13.4 to 21.9 MPa in the SE mode before TC. When used as an ER adhesive, mean bond strengths exceeded 30 MPa. TC did not influence the mean bond strengths in either application mode. Regarding dentin, significant differences in the SE mode were adhesive dependent. Differences were only detected between SBU and IBU before TC and were not present after TC. When SBU, PBE, and ABU were used as ER adhesives, no differences were detected before TC. TC only affected IBU when compared to the other adhesives.

CONCLUSION

Universal adhesives benefit from phosphoric acid etching, as bond strengths increased especially at enamel surfaces.

Influence of etching mode and composite resin type on bond strength to dentin using universal adhesive system

Adhesive bond strength at the composite/dentin interface is influenced by various factors, including the etching mode and composite resin type. The purpose of this study was to evaluate the influence of the total-etch and self-etch mode on the microtensile bond strength (μTBS) of conventional and bulk-fill composite to dentin, using the universal adhesive system. Sixty non-carious human teeth were sectioned parallel to their longitudinal axis, using a low-speed diamond saw to obtain a flat dentin surface. According to the etching technique and composite resin type used, teeth were randomly divided into four different groups (n = 15): TC (total-etch/conventional composite), TB (total-etch/bulk-fill composite), SC (self-etch/conventional composite), and SB (self-etch/bulk-fill composite). Cylindric composite build-ups were made with 3M Filtek Z250 and 3M Filtek Bulkfill Posterior, using a plastic mold, 4 mm in diameter and 4 mm in height. The specimens were subjected to the μTBS test in a universal testing machine and failure force was recorded. Failure modes were determined using stereoscopic and scanning electron microscopy. Data were analyzed using the two-way ANOVA and Student's t test. The μTBS was significantly affected by the etching technique. A significant statistical difference was determined between total-etch and self-etch groups, irrespective of the composite resin type used. Higher bond strength was obtained in total-etch groups. The μTBS was not affected by the composite resin type. No significant statistical difference was determined between the conventional and bulk-fill groups, irrespective of the etching-mode.

In Vitro Study of Shear Bond Strength in Direct and Indirect Bonding with Three Types of Adhesive Systems

This study aimed to compare the shear bond strength (SBS) and adhesive remaining index (ARI) using one conventional and two novel adhesive systems with clinical step reduction and direct and indirect bonding. A sample of 72 human premolars were divided into six groups of 12 samples. The first three groups (G1, G2, G3) were bonded with a direct technique, while the remaining groups (G4, G5, G6) were bonded by the indirect technique. Groups G1 and G4 used conventional acid-etching primer composite (XT); groups G2 and G5 used self-etching bonding (BO), and groups G3 and G6 had an acid-etching treatment followed by a self-adhesive composite (OC). All groups were exposed to thermocycling. Shear bond strength was analyzed with a universal test machine, and the ARI was examined with 4× magnification. The results showed statistically significant differences between the three adhesive systems. The highest strength values were observed in the XT group G1 (13.54 ± 4 MPa), while the lowest were shown in the BO G2 samples (5.05 ± 2 MPa). There was no significant difference between the direct or indirect bonding techniques on the three compared groups. The type of primer and bonding material significantly influenced the SBS. Values with self-etching bonding were below the minimum recommended for clinical use (5.9-7.8 MPa). There was no difference between indirect and direct bonding techniques. The lowest ARI scores (0-1) were observed in both self-etching and BO groups. Further clinical studies are needed to compare in vivo results.

Does Bonding Approach Influence the Bond Strength of Universal Adhesive to Dentin of Primary Teeth?

OBJECTIVE

To evaluate the effect of bonding strategy on microtensile bond strength (μTBS) of a new universal adhesive system to primary tooth dentin.

STUDY DESIGN

Flat dentin surfaces from 25 primary molars were assigned to 5 groups according to the adhesive and bonding approach: Adper Single Bond 2 (two-step etch-and-rinse adhesive) and Clearfil SE Bond (two-step self-etch system), as controls; Scotchbond Universal Adhesive-self-etch, dry or wet-bonding etch-and-rinse strategies. Composite buildups were constructed and the teeth were sectioned to obtain bonded sticks (0.8 mm²) to be tested under tension at 1mm/min. The μTBS means were analyzed by one-way ANOVA and Tukey's tests (α = 0.05). Failure mode was evaluated using a stereomicroscope (400×).

RESULTS

Universal adhesive applied following both dry and wet-bonding etch-and-rinse strategies showed similar bond strength compared with control adhesive systems. Self-etch approach resulted in the lowest μTBS values. For all groups, adhesive/mixed failure prevailed. The percentage of premature debonded specimens was higher when the universal adhesive was used as self-etch mode.

CONCLUSION

The universal adhesive does not share the same versatility of being used in the etch-and-rinse and self-etch approaches; however, the use of the new adhesive following either wet or dry-bonding may be a suitable option as alternative to two-step etch-and-rinse adhesive protocol.

An in vitro evaluation of shear bond strength of silorane and bis-GMA resin-based composite using different curing units

AIM

To evaluate shear bond strength of silorane and bis-GMA based composite resins using self-etch and total-etch adhesive systems, and compare the effect of Quartz-tungten-halogen (QTH) and Light emitting diode (LED) on the shear bond strength of the experimental materials.

MATERIALS AND METHODS

Flat dentin surfaces were exposed on intact extracted molars and composite resin was built 2 mm in diameter. Teeth were divided randomly into four groups. Groups 1 and 2 were restored with P90 system adhesive and Filtek P90 and cured with QTH and LED units respectively. Groups 3 and 4 were restored with total etch adhesive and Filtek Z100 and cured with QTH and LED units respectively. Specimens were subjected to shear bond strength testing using Instrom Universal testing machine.

RESULTS

Data was subjected to one-way analysis of variance. Total-etch groups gave significantly higher shear bond strength values than the self-etch groups. No significant difference in shear bond strength was found between Groups 3 and 4, while Group 1 showed significantly higher values than Group 2.

CONCLUSION

Type of light curing unit is not a significant factor affecting shear bond strength for bis-GMA RBCs using total-etch technique; while for curing silorane resin based composite (RBCs), conventional halogen curing units showed better results.

Clinical effects of different etching modes for universal adhesives: a systematic review and meta-analysis

BACKGROUND

To evaluate the clinical performance of universal adhesives in etch-and-rinse or self-etch application modes through meta-analysis.

METHODS

A literature search was performed by two reviewers in the PubMed, Cochrane Library, and Embase databases (from January 2000 to March 2020). A total of 2,516 non-replicated records were identified and filtered. Studies that evaluated the clinical performance of universal adhesives using etch-and-rinse or self-etch mode were included. RevMan 5.3.5 (Cochrane, London, UK) was used to perform the meta-analysis.

RESULTS

A total of 13 studies were included in the meta-analysis. The retention rates were higher in etch-and-rinse groups compared with self-etch groups [odds ratio (OR) =0.35, 95% confidence interval (CI): 0.18-0.71, P=0.003]. The etch-and-rinse approach also had better performance in marginal adaptation (OR =0.49, 95% CI: 0.36-0.67, P<0.001) and marginal staining (OR =0.49, 95% CI: 0.36-0.66, P<0.001). The current data showed a very low incidence rate of secondary caries or postoperative sensitivity, and there were no significant differences in the incidence rates between the etch-and-rinse groups and self-etch groups.

DISCUSSION

The current evidence shows that, compared with self-etch approach, the etch-and-rinse approach for universal adhesives provides improved clinical outcomes in terms of retention rates, marginal adaptation, and marginal staining.

Bonding performance of universal adhesives to er,cr:YSGG laser-irradiated enamel

Universal adhesives have been recently introduced for use as self-etch or etch-and-rinse adhesives depending on the dental substrate and clinical condition. However, their bonding effectiveness to laser-irradiated enamel is still not well-known. Thus, the aim of this study was to compare the shear bond strength (SBS) of universal adhesives (Single Bond Universal; Nova Compo-B Plus) applied to Er,Cr:YSGG laser-irradiated enamel with SBS of the same adhesives applied in self-etch and acid-etching modes, respectively. Crown segments of sixty bovine incisors were embedded into standardized acrylic blocks. Flattened enamel surfaces were prepared. Specimens were divided into six groups according to universal adhesives and application modes randomly (n = 10), as follows: Single Bond Universal/acid-etching mode; Nova Compo-B Plus/acid-etching mode; Single Bond Universal/self-etching mode; Nova Compo-B Plus/self-etching mode; and Single Bond Universal/Er,Cr:YSGG Laser-etching mode; Nova Compo-B Plus/Er,Cr:YSGG Laser-etching mode. After surface treatments, universal adhesives were applied onto surfaces. SBS was determined after storage in water for 24 h using a universal testing machine with a crosshead speed of 0.5 mm min^-1 . Failure modes were evaluated using a stereomicroscope. Data was analyzed using two-way of analyses of variances (ANOVA) (p = 0.05). Two-way ANOVA revealed that adhesive had no effect on SBS (p = 0.88), but application mode significantly influenced SBS (p = 0.00). Acid-etching significantly increased SBS, whereas there are no significant differences between self-etch mode and laser-etching for both adhesives. The bond strength of universal adhesives may depend on application mode. Acid etching may significantly increase bond strength, while laser etching may provide similar bond strength when compared to self-etch mode.

Effects of artificial aging on the bond strengths of universal dental adhesives

Aims

The effect of mechanical loading on the microtensile bond strength (μTBS) of universal adhesives to dentin was evaluated in this study.

Methods and Materials

Human molar teeth had the occlusal dentin surfaces exposed and were allocated into ten groups (five experimental groups and five control groups) that used the following universal adhesive systems in self-etch mode: All-Bond Universal (ABU), Single Bond Universal (SBU), Gluma Bond Universal (GBU), Tetric N-Bond Universal (TBU), and Clearfil Universal Bond (CUB). Following the bonding procedures and build-ups, the specimens were either stored in water at 37°C for 24 h or were mechanically loaded (50 N for 60,000 cycles) prior to the μTBS test. Data were analyzed using the one-way analysis of variance (ANOVA) and Tukey's posthoc test (P = 0.05).

Results

Both the adhesive type and mechanical loading had significant effects on the μTBS (P < 0.05). The μTBS values of SBU and ABU were significantly higher than the values of the other adhesives (P < 0.05). However, the μTBS values of ABU decreased significantly after mechanical loading (P < 0.05).

Conclusions

With the exception of ABU, mechanical loading had no deleterious effects on the μTBS of the universal adhesive systems examined in this study.

Effect of Different Surface Treatments on Repair Micro-shear Bond Strength of Silica- and Zirconia-filled Composite Resins

Background and aims

Effect of surface treatments on repair bond strength of aged composite resins might be different due to their dissimilar fillers. The aim was to evaluate the effect of different surface treatments on repair micro-shear bond strength (µSBS) of silica- (Spectrum TPH) and zirconia-filled (Filtek Z250) composite resins.

Materials and methods

Twenty-seven composite resin blocks were made from each type of composite resin: Z250 and Spectrum TPH. After aging, blocks of each type were randomly divided into three groups according to surface treatments: alloy primer, silane, and only surface roughening. Subsequently, each group was further subdivided into 3 subgroups based on the adhesive system used: Single Bond, Clearfil SE Bond, and Margin Bond. Four composite resin columns were added on each block. After thermocycling, µSBStest were done at cross head speed of 0.5 mm/min. Data was analysed using multifactor ANOVA, one-way ANOVA and a post-hoc Bonferroni tests (α = 0.05).

Results

Analysis of data showed that the effect of composite resin type was not significant (p > 0.05), but the effects of the type of surface treatment (p = 0.01) and the type of adhesive system (p = 0.01) were significant on repair µSBS. In addition, the cumulative effect of the composite type-surface treatment and the composite type with the type of adhesive system were not statistically significant (p > 0.05). However, the cumulative effects of the adhesive system-surface treatment (p = 0.03) and the composite type-the adhesive system-surface treatments (p = 0.002) were significant.

Conclusion

Although repair µSBS values of both silica- and zirconia-filled composite resins were similar, use of different combinations of surface treatments and adhesive systems affected their repair µSBS differently.

Bonding Performance of Simplified Dental Adhesives with Three Application Protocols: An 18-month In Vitro Study

PURPOSE

To evaluate the influence of application protocol on the shear bond strength (SBS) and nanoleakage of simplified adhesives over 18 months.

MATERIALS AND METHODS

810 dentin slices were obtained from 405 caries-free human molars. They were randomly assigned to 54 experimental groups resulting from the combination of "adhesive" (Adper Scotchbond 1XT [S1XT], Solobond M [SM], Scotchbond Universal Adhesive in etch-and-rinse mode [SUER] and self-etch mode [SUSE], Adper Easy Bond [EB], Clearfil S3 Bond Plus [CS3]), "application protocol" (manufacturer's instructions [MI], two extra layers of adhesive [EL], hydrophobic resin layer [HL]), and "aging time" (24 h [24H], 6 months [6M], and 18 months [18M] in water). SBS tests were carried out using a Watanabe device followed by failure mode analysis. For the nanoleakage study, specimens from 54 additional molars were prepared as previously described, immersed in ammoniacal silver nitrate, and evaluated with SEM. SBS data were analyzed with ANOVA followed by Tukey's post-hoc tests; failure mode data were analyzed using chi-squared tests (α = 0.05). Nanoleakage data were analyzed with the Kruskal-Wallis test followed by LSD tests (α = 0.05).

RESULTS

After 18M, S1XT and SUSE achieved the highest mean SBS (p < 0.05). Regarding the application protocols, EL and HL provided higher mean SBS than those obtained with MI (p < 0.05). HL resulted in the highest mean SBS and the lowest mean nanoleakage after 18M.

CONCLUSION

Simplified adhesives may need an extra hydrophobic resin layer to achieve a stable and durable adhesive interface. The self-etch approach should be recommended for the universal adhesive.

Effect of Casein Phosphopeptide-amorphous Calcium Phosphate Treatment on Microtensile Bond Strength to Carious Affected Dentin Using Two Adhesive Strategies

Background and aims. The aim was to evaluate the effect of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) on microtensile bond strength (μTBS) to carious affected dentin (CAD) using etch-and-rinse and self-etch adhesive systems.

Materials and methods. The occlusal surface of 32 human molars with moderate occlusal caries was removed. Infected dentin was removed until reaching CAD and the teeth were randomly divided into two groups based on the Single Bond (SB) and Clearfil SE Bond (CSE) adhesive systems. Before composite resin bonding, each group was subdivided into three subgroups of ND, CAD and CPP-ACP-treated CAD (CAD-CPP) based on the dentin substrate. After dissecting samples to l-mm-thick cross-sections (each subgroup: n = 13), μTBS was measured at a strain rate of 0.5 mm/min. Data was analyzed using two-way ANOVA, independent samples t-test and post-hoc Tukey tests (α=0.05).

Results. Bond strength of both adhesive systems to ND was significantly higher than that to CAD (P <0.001) and CAD/CPP (P < 0.001). There were no significant differences between the μTBS of SB to CAD and CAD-CPP (P > 0.05).μTBS of CSE to CAD-CPP was higher than that to CAD; however, the difference was not significant (P > 0.05). Significant differences were found between SB and CSE systems only with CAD substrate (P < 0.001).

Conclusion. Regardless of the adhesive system used, surface treatment of CAD with CPP-ACP did not have a significant effect on bond strength. However, bond strength to CAD was higher with SB rather than with CSE.

In Vitro Study on the Effect of a New Bioactive Desensitizer on Dentin Tubule Sealing and Bonding

Bioactive mineral-based dentin desensitizers that can quickly and effectively seal dentinal tubules and promote dentin mineralization are desired. This in vitro study evaluated a novel nanohydroxyapatite-based desensitizer, Predicta (PBD, Parkell), and its effect on bond strength of dental adhesives. Human dentin discs (2-mm thick) were subjected to 0.5 M EDTA to remove the smear layer and expose tubules, treated with PBD, and processed for surface and cross-sectional SEM examination before and after immersion in simulated body fluid (SBF) for four weeks (ISO 23317-2014). The effects of two dental desensitizers on the microshear bond strength of a universal adhesive and a two-step self-etch system were compared. SEM showed coverage and penetration of nanoparticles in wide tubules on the PBD-treated dentin at the baseline. After four weeks in SBF, untreated dentin showed amorphous mineral deposits while PBD-treated dentin disclosed a highly mineralized structure integrated with dentin. Desensitizers significantly reduced microshear bond strength test (MSBS) of adhesives by 15-20% on average, depending on the bonding protocol. In conclusion, PBD demonstrated effective immediate tubules sealing capability and promoted mineral crystal growth over dentin and into the tubules during SBF-storage. For bonding to desensitizer-treated dentin, a two-step self-etching adhesive or universal bond with phosphoric acid pretreatment are recommended.

Effect of 2% Chlorhexidine on Resin Bond Strength and Mode of Failure Using Two Different Adhesives on Dentin: An In Vitro Study

Aim

To evaluate the shear bond strength and failure mode of total-etch and self-etch bonding agents on human dentin with and without application of 2% chlorhexidine gluconate (CHX).

Materials and Methods

Eighty extracted premolars were chosen and stored in 10% formalin until use. Samples were mounted in cold cure acrylic resin and the occlusal enamel perpendicular to long axis of each tooth was removed using a low-speed diamond saw under water coolant. The prepared teeth were randomly divided into four groups of 20 samples each according to the adhesive system used. Groups 1 and 2 were the control group in which total-etch and self-etch adhesives were applied as per manufacturer's instructions, Groups 3 and 4 were the experimental groups in which 2% CHX was applied and blot dried prior to the application of total-etch and self-etch adhesives. A custom-designed rig was fabricated to place composite on samples. The customized rig comprised a cylindrical mold with height of 3 mm and internal diameter of 2.5 mm. Resin was placed in increments of 1 mm and was cured after each increments. After the composite placements, samples were placed in distilled water at 37°C for 24 h. The samples were then thermocycled between 5°C and 55°C in water with a dwell time of 30 s in each temperature to a total of 10,000 cycles. The shear test was performed using universal testing machine and fracture modes were evaluated using stereomicroscope.

Results

Both the experimental total-etch and self-etch groups showed better shear bond strength than the control groups, which was statistically significant, and also the least mode of failure at the adhesive interface was observed in both the experimental groups.

Conclusion

2% Chlorhexidine gluconate effectively improved the shear bond strength and helped maintaining the durability of adhesive interface in both total-etch and self-etch adhesives.

Clinical efficacy of universal adhesives for the restoration of noncarious cervical lesions: A randomized clinical trial

Introduction

The efficacy of an adhesive agent is an important aspect in restoring noncarious cervical lesion (NCCL) as studies have proved that compromise in adhesive agent results in reduced bond strength. The purpose of this prospective randomized double-blind clinical trial was to evaluate the efficacy of the newly formulated "universal" dental adhesive in the restoration of NCCLs in permanent dentition using either a self-etch or a selective-etch approach.

Materials and Methods

The study was done following the consolidated standards of reporting trials. 100 NCCLs randomly divided into 2 groups were restored using G-Premio Bond adhesive and Genial flowable composite in selective etch mode and self-etch mode. Restorations were evaluated at 1 week, 6 months, and 12 months using modified US Public Health Service criteria for marginal staining, fracture, and postoperative sensitivity. Statistical analysis was performed using appropriate tests.

Results

Recall rates were 100%, 98%, and 78% at the evaluation time. The result showed that neither the self-etch nor the selective etch mode had significant difference in ALPHA/BRAVO/CHARLIE scores (P > 0.05). Percentage-wise comparison showed less changes reported in the selective etch group compared to self-etch group.

Conclusion

It was concluded that there was no statistical significance between the groups for the parameters evaluated, but selective etch performed better than self-etch group.

Short- and Long-Term Dentin Bond Strength of Bioactive Glass-Modified Dental Adhesives

This study investigated the short- and long-term effects of dental adhesives doped with nano-sized bioactive glass 45S5 (BAG) on the resin-dentin interfacial bond strength. Two etch-and-rinse adhesives (Adper Scotchbond Multi-Purpose (ASB) and Solobond Plus (SB)) and one self-etch adhesive (Clearfil SE Bond (CF)) were doped with different concentrations of BAG (5, 10, and 20 wt%). The unmodified (0 wt% BAG) commercial adhesives served as control groups. Dentin of 120 molars (n = 10 per group) was treated with the different adhesives, followed by buildups with a conventional composite restorative material. From each tooth, 14 sticks were prepared for micro-tensile bond strength (µTBS) testing. The sticks were stored in simulated body fluid at 37 °C and tested after 24 h or six months for µTBS and failure mode. Data were analyzed using Kruskal-Wallis tests in combination with post-hoc Conover-tests and Wilcoxon signed-rank tests at a level of significance of α = 0.05. After 24 h and six months, both etch-and-rinse adhesives with a low BAG content (up to 10 wt% for ASB and 5 wt% for SB) showed similar µTBSs as their respective control groups (0 wt% BAG). CF showed a significant decrease in µTBS even after addition of 5 wt% BAG. At a high concentration of added BAG (20 wt%), all three adhesives showed a significant decrease in µTBS compared to the unmodified controls. The CF control group showed significantly lower µTBS after 6 months of storage than after 24 h. In contrast, the µTBS of all CF groups modified with BAG was unaffected by aging. In conclusion, the tested etch-and-rinse adhesives can be modified with up to 5 wt% (SB), or 10 wt% (ASB) of BAG without reducing their short- and long-term dentin bond strength. Moreover, the addition of nano-sized BAG may prevent long-term bond strength deterioration of a self-etch adhesive.

Bonding strategies to deal with caries-affected dentin using cross-linking agents: Grape seed extract, green tea extract, and glutaraldehyde - An in vitro study

Aim

This study evaluated the effect of three collagen cross-linking agents - proanthocyanidins (grape seed extract [GSE] and green tea extract [GTE]) and glutaraldehyde [GA] on microshear bond strength (μSBS) of caries-affected dentin (CAD)-resin complex.

Materials and Methods

Freshly extracted 96 teeth with caries up to the middle third of dentin were sectioned through the deepest part of the occlusal fissure, perpendicular to the long axis of the crown. Caries was excavated with large round bur until firm dentin was obtained, confirmed by visual inspection and tactile examination. Flat occlusal dentin surfaces were treated as follows: Group-1 - 6.5% GSE (n = 30), Group-2 - 2% GTE (n = 30), Group-3 - 5% Glutaraldehyde (n = 30), Group-4 - control group (no agents) (n = 6). Each group was further divided into Subgroup A - Etch-N-Rinse 15s, Subgroup B - Etch-N-Rinse 45s, and Subgroup C - Self-etch. Two increments of 1.5-mm thick composite (Tetric-N-Ceram - Ivoclar Vivadent) with a 1-mm diameter were built-up. Each sample was subjected to μSBS test in Universal Testing Machine. Student's t-test was done for intragroup comparison and one-way ANOVA for intergroup comparison.

Results

Statistically significant difference was present in mean μSBS, with Group 1B showing the best results and Group 4C, the least.

Conclusions

Thus, the application of these collagen cross-linkers, to CAD, increases μSBS and promises a new approach to improve dentin bond strength.

Effect of etching on bonding of a self-etch adhesive to dentine affected by amelogenesis imperfecta

AIM

Dentine affected by amelogenesis imperfecta (AI) is histologically altered due to loss of hypoplastic enamel and becomes hypermineralized. In the present study, we examined the effect of additional acid etching on microtensile bond strength of a self-etch adhesive to AI-affected dentine.

METHODS

Flat coronal dentine obtained from extracted AI-affected and non-carious permanent molars were allocated to two groups: (a) Clearfil SE Bond (control); and (b) Clearfil SE Bond and additional etching with 34% phosphoric acid for 15 seconds. The bonded teeth were sectioned into .8-mm² beams for microtensile bond strength testing, and stressed to failure under tension. The bond strength data were analyzed using two-way analysis of variance (dentine type and etching step) and Student-Newman-Keuls multiple comparison test (P<.05). Representative fractured beams from each group were examined under scanning electron microscopy.

RESULTS

Both factors, dentine substrate (P<.001) and etching step (P<.05), and their interactions (P<.001), were statistically significant. Additional etching had an adverse effect on the bond strength of Clearfil SE Bond to normal dentine (P<.005), and no significant improvement was found for AI-affected dentine (P=.479).

CONCLUSION

Additional acid etching does not improve the bond strength of a self-etch adhesive to AI-affected dentine.

Microleakage of pit and fissure sealings placed after enamel conditioning with phosphoric acid or with self-etching primers/adhesives

Background

It is still not fully understood what pretreatment is best for achieving maximum tightness for pit and fissure sealings (PFS).

Aim

This study investigated microleakage of PFS placed after etching with phosphoric acid or after the application of self‐etching primers/adhesives (SEPA).

Design

131 third molars were assigned to ten groups. In Hel‐P, Helioseal® was applied after phosphoric acid etching. In the other groups, SEPA were used (Dyr‐AP: Adper™ Prompt™ L‐Pop™, Dyract® Seal; Bea: BeautiSealant Primer and Paste; Hel‐Exp: Experimental primer, Helioseal®; Hel‐Cl: Clearfil™ SE Bond¹, Helioseal®). Specimens were stored in distilled water at 37°C (28 days), followed by 3500 thermocycles and staining with 5% methylene blue (M) or 5% silver nitrate (S). After methylene blue staining and sectioning, microleakage was assessed light microscopically. During silver nitrate staining, specimens were dissolved by 32% HCl and remaining PFS were evaluated under a SEM.

Results

Tightness, percentage of penetrated area, and maximum dye penetration were best for Hel‐P and Hel‐Cl (p < 0.05).

Conclusions

Phosphoric acid etching of enamel and Clearfil™ SE Bond resulted in the best sealing quality. Methylene blue staining allowed the evaluation of more criteria (fissure shape, voids, sealant penetration depth) compared to silver nitrate.

Effect of an extra layer of hydrophobic resin on the microleakage of Cl V composite resin restorations with a universal adhesive system

AIM

The aim of the present study was to evaluate the effect of the application of a hydrophobic resin on the microleakage of Cl V composite resin restorations using a universal adhesive system applied in the self-etch (SE) and etch-and-rinse (ER) modes.

METHOD

Cl V cavities were prepared on the buccal surfaces of 64 human premolar teeth and divided into four groups (n = 16): ER, ER with hydrophobic resin (ERH), SE, and SE with hydrophobic resin (SEH). Microleakage at occlusal and gingival margins was evaluated using 0.5% methylene blue dye penetration technique under stereomicroscope at 40 × magnification. Data were analyzed using Kruskal-Wallis and Mann-Whitney U-tests (P < 0.05).

RESULTS

At the enamel margins, the ER group had significantly less microleakage than the SE and SEH groups (P < 0.001), but had no significant difference compared with the ERH group (P > 0.05). There was also no statistically-significant difference between the SE and SEH groups (P > 0.05). At the dentinal margins, the SE group had significantly less microleakage compared with the ER (P < 0.001) and ERH groups (P = 0.005). Furthermore, microleakage of the SEH group was significantly less than the SE group (P < 0.001).

CONCLUSION

Applying an extra layer of hydrophobic resin significantly decreased microleakage in the SE mode at the dentinal margin, but had no significant effect in the ER mode.