Shear bond strength of orthodontic brackets bonded with a new self-adhering flowable resin composite

Effects of Thermocycling with Two Different Curing Techniques on Enamel Micro-Cracks Formation, Debonding, and Failure Modes of Ceramic Brackets: An In Vitro Study

Despite the rise in popularity of ceramic braces for adults, the risk of enamel microcracks (EMCs) upon removal remains a significant drawback for both dental professionals and patients. Our study aimed to assess the effects of thermocycling, pre-curing, and co-curing techniques with different bonding agents on the enamel surface of teeth after the removal of ceramic brackets. We also examined the incidence, quantity, length, and direction of EMCs on tooth surfaces. Additionally, the adhesive remnant index (ARI) scores and orthodontic bracket bond failure modes were evaluated and compared. The study divided 40 extracted upper canine teeth into ten groups for further analysis. Two groups had intact enamel as the negative control, while the remaining groups had orthodontic ceramic brackets bonded using different bonding agents and curing techniques. Thermocycling was performed in five groups, and ARI was assessed after debonding. The study findings were statistically significant (p < 0.05) in demonstrating the impact of curing techniques on EMCs and debonding outcomes. Seventh-generation bonding agents resulted in complete adhesive removal (ARI = 0). The microcracks' incidence, number, and length showed insignificant results. Differences in ARI between thermocycler and non-thermocycler samples were insignificant. Both co-curing and pre-curing techniques yielded comparable ARI results. This study highlights the importance of using advanced bonding agents to minimize enamel damage during ceramic bracket debonding.

Cyclic shear fatigue of orthodontic brackets bonded to enamel using self-adhering flowable composites

Background

Self-adhering composites are claimed to bond to teeth without prior acid etching and bonding steps. This study aimed to evaluate the cyclic shear fatigue (CSF) of metal orthodontic brackets bonded to enamel using self-adhering flowable composites (Constic and VertiseTM Flow) in comparison with that of total-etch and self-etch adhesives.

Materials and methods

Twenty-five human premolars comprising 100 surfaces were randomly divided into four groups (n = 25): total-etch, self-etch, Constic, and VertiseTM Flow. A total of 10 surfaces were used per group for baseline static shear bond strength (SSBS) evaluation and 15 surfaces for CSF evaluation. Each tooth was treated with the four bonding agents. Both SSBS and CSF were evaluated using a universal testing machine. For CSF, the staircase method was used with an initial pulling load equivalent to 60% of the SSBS of each group for 1000 cycles or until failure. The adhesive remaining index (ARI) was evaluated for surviving samples using a stereomicroscope.

Statistical analysis

A one-way ANOVA with Tukey's post hoc test was used to analyze the CSF data, and a chi-square test was used to analyze the ARI.

Results

The total-etch adhesive showed significantly higher CSF values than that of the other groups (p < 0.001). Both total-etch (10.78 ± 0.31 MPa) and self-etch (6.75 ± 0.91 MPa) adhesives showed significantly higher CSF than did Constic (1.94 ± 0.31 MPa) and VertiseTM Flow (2.01 ± 0.25 MPa), (p < 0.001). The ARI indicated that more resin remnants were observed with the total-etch and self-etch adhesives than those with the self-adhering flowable composites. However, no significant differences were observed among groups (p > 0.05).

Conclusions

Total-etch and self-etch adhesives showed satisfactory bond strengths for orthodontic treatment. However, Constic and VertiseTM Flow self-adhering flowable composites may not be clinically sufficient for bonding metallic orthodontic brackets to enamel.

Effect of varying functional monomers in experimental self-adhesive composites: polymerization kinetics, cell metabolism influence and sealing ability

The aim was to evaluate the effects of adding different functional monomers to experimental self-adhesive composites (SACs) on polymerization kinetics, cell metabolic activity, and sealing ability. SACs were formulated using urethane dimethacrylate as the base monomer and triethylene glycol dimethacrylate. Additionally, 10 wt.% of distinct functional monomers were added - 10-methacryloyloxydecyl dihydrogen phosphate, glycerol phosphate dimethacrylate (GPDM), 2-hydroxyethyl methacrylate (HEMA) or hydroxyethyl acrylamide (HEAA). ATR-FTIR was used to determine real-time polymerization kinetics (20 min,n= 3). The final extrapolated conversion and polymerization rates were determined (DC,max;Rp,max). TheDC,maxvalues were employed to calculate volumetric shrinkage. The MTT assay was performed on MDPC-23 cells using disc extracts at different concentrations (n= 8). Class V cavities were prepared in 60 sound human molars, assigned to six groups (n= 10), depending on the composite used and aging type (T0 or TC, if thermocycled for 10 000 cycles). One-way ANOVA, two-way, andKruskal-Wallistests were employed to treat the data (ɑ= 0.05). Varying the functional monomers had a large impact on DC,max, as confirmed by one-way ANOVA (p<0.001). The highest was obtained for HEMA (64 ± 3%). The HEMA and HEAA formulations were found to be significantly more toxic at concentrations below 100%. For microleakage, having a functional monomer or not did not show any improvement, irrespective of margin or aging period (Mann-Whitney U,p> 0.05). Larger functional monomers MDP and GPDM affected polymerization properties. Conversely, their acidity did not seem to be detrimental to cell metabolic activity. Regarding sealing ability, it seems that the functional monomers did not bring an advantage to the composites. Varying the functional monomer in SACs had a clear impact on the polymerization kinetics as well as on their cytotoxic potential. However, it did not confer better microleakage and sealing. Claiming self-adhesiveness based only on functional monomers seems dubious.

12-Month flexural mechanical properties of conventional and self-adhesive flowable resin composite materials

The aim of this study was to investigate the 12-month flexural mechanical properties of 23 flowable resin-based composites (FRBC) that included 5 self-adhesive FRBC materials. Specimens were evaluated following ISO 4049:2019 guidelines, but additionally stored in physiologic 0.2M phosphate buffered saline solution being tested at 24 h, 1 week, 1 month, and at 3-, 6-, 9-, and 12-months. While some deviation and degradation were noted at testing intervals, conventional FRBC materials overall demonstrated greater flexural strength than the self-adhesive and compomer materials. Three self-adhesive materials and the compomer were below recommended ISO 4049:2019 flexural strength values at 24 h with another after 6 months storage. Conventional FRBC materials, except at 1 month, overall demonstrated increased flexural modulus than the self-adhesive FRBC materials. Although results were material dependent, conventional FRBC materials demonstrated overall greater flexural mechanical properties as compared to the self-adhesive FRBC materials and the compomer evaluated.

Effect of Different Adhesive Strategies on the Microshear Bond Strength of Calcium-Silicate-Based Materials

Aim:

To evaluate the microshear bond strength (µSBS) of mineral trioxide aggregate and Biodentine to various resin-based materials using different adhesive strategies.

Materials and Methods:

Three resin-based materials—a self-adhering resin composite with or without acid etching (Vertise flow; Kerr, Orange, CA, USA), a conventional flowable composite with a total-etch adhesive (Filtek Ultimate Flowable; 3M ESPE, St. Paul, MN, USA), and a flowable resin-modified glass ionomer cement (RMGIC) without any surface modification (Ionoseal; VOCO GmbH, Cuxhaven, Germany)—and two calcium-silicate-based materials—Biodentine and BIOfactor mineral trioxide aggregate (MTA)—were tested. A total of 100 cylindrical acrylic molds were prepared. Biodentine and BIOfactor MTA were prepared and placed into the central holes on the molds. Specimens were divided into two main groups according to materials and into five subgroups ( n = 10). µSBS were evaluated using a µSBS testing device. The failure modes were examined under a stereomicroscope with magnification. They were categorized as adhesive, cohesive, or mixed. Data were analyzed using two-way analysis of variance (ANOVA) and Tukey test. The significance level was taken as α = 0.05.

Results:

It was observed that both calcium-silicate-based material type and resin-based material type influenced the µSBS significantly according to two-way ANOVA. Biodentine exhibited higher bond strength values than MTA. However, no statistically significant interaction was demonstrated between these factors ( P = .396). The µSBS values of intermediate materials to Biodentine and MTA were listed from the lowest to the highest as follows: RMGIC < Acid Etch + RMGIC < SARC (self-adhering resin composite) < FC (flowable composite) < Acid Etch + SARC.

Conclusion:

Self-adhering composites can be used on calcium-silicate-based materials in vital pulp treatments because of their mechanical properties. Acid-etching ensures high µSBS values. Although the µSBS of Biodentine were higher than MTA according to this study’s results, there was no statistically significant difference in µSBS of FC and acid-etched SARC to MTA.

Bracket Bonding to All-Ceramic Materials with Universal Adhesives

The need for bracket bonding to ceramic restorations is increasing. The aim of this study was to evaluate the effect of universal adhesives on bracket adhesion to polished or glazed lithium disilicate (LDS) and monolithic zirconia (MZ) surfaces. One hundred and twenty brackets (N = 10) were bonded to either polished or glazed LDS (e.max CAD B32, Ivoclar Vivadent, Schaan, Liechtenstein) and MZ (In-Ceram^® YZ, VITA, Bad Sackingen, Germany) blocks using three different adhesives combined with Transbond™ XT Paste (3M Unitek, Monrovia, CA, USA). Tested universal adhesives were Scotchbond™ Universal Adhesive (SU, 3M St. Paul, MN, USA) and Assure Plus (AP, Reliance, Itasca, IL, USA). Transbond™ XT Primer (XTP, 3M Unitek, Monrovia, CA, USA) served as a control adhesive. Bracket bond strength was measured in shear mode (SBS). Failure type was determined by the Modified Adhesive Remnant Index (ARI). Data were statistically analyzed. On polished LDS, SU yielded bracket SBS significantly superior to those of AP and XTP. On polished MZ, the use of SU and AP significantly enhanced bracket retention as compared with XTP. Low SBS values, below the threshold of clinical acceptability, were reached by all tested adhesives on glazed LDS and MZ specimens. SBS measurements corresponded with failure type observations. Universal adhesives SU and AP could be considered for use on polished LDS and MZ surfaces.

No-primer adhesive vs. self-adhesive resin: bonding strength following LED curing

PURPOSE

The goal of this study was to compare the shear bond strength (SBS) and failure modes of three different adhesive resins following the use of two different dental curing light units.

METHODS

A total of 160 human premolars were randomly divided into four groups (N = 40 for each): group 1, Transbond™ XT (3M Unitek, Monrovia, CA, USA) adhesive paste; group 2, Heliosit Orthodontic paste with no primer; group 3, Maxcem Elite (Kerr, Orange, CA, USA) self-adhesive resin with prior etching; group 4, Maxcem Elite self-adhesive resin with no etching. Each group was further divided into 2 subgroups: half (named "a") were cured with VALO LED (Ultradent Products, South Jordan, UT, USA), and the other half (named "b") with the Elipar LED unit (3M Unitek LED, Monrovia, CA, USA). The brackets were submitted to SBS testing 24 h after bonding. Adhesive Remnant Index (ARI) scores and bonding time were also measured. Two-way analysis of variance (ANOVA) and Kruskal-Wallis tests were used for statistical analysis.

RESULTS

No significant differences in SBS were observed when comparing the two different LED devices within the same bonding material. The mean SBS of group 1 was significantly higher compared to groups 2, 3, and 4 (p < 0.001). Mean SBS values of groups 2 and 3 were significantly higher than that of group 4 (p < 0.001). ARI scores were significantly different in groups 4a and 4b compared to the other groups (p < 0.05). Group 4a showed significantly lower bonding time/tooth compared to the other groups except to groups 3a and 4b (p < 0.001).

CONCLUSIONS

Decreasing curing time using high-power LED device did not significantly affect SBS. However, the composite type did affect SBS.

Bond strength of self-adhesive flowable composite resins to dental tissues: A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

Although the clinical use of self-adhesive flowable composite resins is convenient, the decision to use flowable or conventional composite resin remains controversial.

PURPOSE

The purpose of this systematic review and meta-analysis was to assess the in vitro bond strength of self-adhesive flowable composite resins to enamel or dentin compared with conventional composite resins using etch-and-rinse or self-etch adhesive systems.

MATERIAL AND METHODS

Two independent reviewers performed searches in the PubMed (MEDLINE), Cochrane Wiley, Web of Science, Scopus, and Google Scholar databases for studies reporting on the bond strength of self-adhesive flowable and conventional composite resins to enamel and dentin published from January 2010 up to September 2020. A meta-analysis software program was used for the meta-analysis. Comparisons were conducted using standardized mean differences considering the random-effects model (α=.05).

RESULTS

Twenty-two studies were considered for the meta-analysis. Immediate and long-term bond strength to enamel was improved when a conventional composite resin was used in combination with an adhesive system (P<.001). Bond strength to dentin was improved by using an adhesive system in combination with a conventional composite resin (P<.001).

CONCLUSIONS

The bond strength of self-adhesive flowable composite resins is lower than that of conventional composite resins, indicating limited ability to bond to enamel and dentin.

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.

In vitro evaluation of shear bond strength of orthodontic metal brackets to aged composite using a self-adhesive composite: Effect of surface conditioning and different bonding agents

OBJECTIVES

Bracket bonding to composite surfaces is increasing. This study sought to assess the effect of different adhesives (acid etchant+Transbond XT™, acid etchant+Vertise Flow™, Vertise Flow™) with different surface treatments (no preparation, bur, sandblasting, Er:YAG laser) on shear bond strength (SBS) of metal brackets to aged composite.

MATERIALS AND METHODS

In this in vitro, experimental study, Filtek™ Z250 composite discs were fabricated (10×4mm). After thermocycling (10,000 cycles between 5-55°C), the samples were randomly divided into three groups (n=48) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. Samples in each group were randomly divided into four subgroups (n=12) based on the surface treatment including no-treatment, diamond bur, sandblasting and Er:YAG laser. Samples in each group were randomly divided into three subgroups (n=12) based on the type of adhesive namely acid etchant+Transbond XT™, Vertise Flow™, and acid etchant+Vertise Flow™. After bracket bonding to composite discs, the samples underwent thermocycling (5000 cycles between 5-55°C), and their SBS was measured in a universal testing machine. The samples were then inspected under a stereomicroscope at x10 magnification to determine their mode of failure and adhesive remnant index (ARI).

RESULTS

No significant difference was noted in SBS between adhesives in no-preparation and laser groups (P>0.05). In all adhesive groups, sandblast had highest SBS, but it was not significantly different in Vertise Flow™ groups, with and without etching. The SBS provided by acid etchant+Transbond XT™ was significantly higher than that of the other two adhesives (P<0.05). The SBS of sandblasted samples was significantly higher compared with other surface treatments in all adhesive subgroups (P<0.05).

CONCLUSION

Bracket bonding to aged composite using Vertise Flow™ with or without surface treatment can serve as an alternative to the conventional orthodontic adhesives.

Bracket bonding to polymethylmethacrylate-based materials for computer-aided design/manufacture of temporary restorations: Influence of mechanical treatment and chemical treatment with universal adhesives

Objective

To assess shear bond strength and failure mode (Adhesive Remnant Index, ARI) of orthodontic brackets bonded to polymethylmethacrylate (PMMA) blocks for computer-aided design/manufacture (CAD/CAM) fabrication of temporary restorations, following substrate chemical or mechanical treatment.

Methods

Two types of PMMA blocks were tested: CAD-Temp® (VITA) and Telio® CAD (Ivoclar-Vivadent). The substrate was roughened with 320-grit sandpaper, simulating a fine-grit diamond bur. Two universal adhesives, Scotchbond Universal Adhesive (SU) and Assure Plus (AP), and a conventional adhesive, Transbond XT Primer (XTP; control), were used in combination with Transbond XT Paste to bond the brackets. Six experimental groups were formed: (1) CADTemp®/SU; (2) CAD-Temp®/AP; (3) CAD-Temp®/XTP; (4) Telio® CAD/SU; (5) Telio® CAD/AP; (6) Telio® CAD/XTP. Shear bond strength and ARI were assessed. On 1 extra block for each PMMA-based material surfaces were roughened with 180-grit sandpaper, simulating a normal/medium-grit (100 mm) diamond bur, and brackets were bonded. Shear bond strengths and ARI scores were compared with those of groups 3, 6.

Results

On CAD-Temp® significantly higher bracket bond strengths than on Telio® CAD were recorded. With XTP significantly lower levels of adhesion were reached than using SU or AP. Roughening with a coarser bur resulted in a significant increase in adhesion.

Conclusions

Bracket bonding to CAD/CAM PMMA can be promoted by grinding the substrate with a normal/medium-grit bur or by coating the intact surface with universal adhesives. With appropriate pretreatments, bracket adhesion to CAD/CAM PMMA temporary restorations can be enhanced to clinically satisfactory levels.

Effect of in vitro aging by water immersion and thermocycling on the mechanical properties of PETG aligner material

PURPOSE

The mechanical properties of orthodontic aligners made from thermoplastic polymers decrease over time in the intraoral milieu. However, there is a lack of information on this topic in the literature. Thus, the elastic properties of polyethylene terephthalate glycol (PETG) aligner films were investigated in vitro under extreme temperature changes simulated by thermocycling, environmental temperature and water absorption.

MATERIALS AND METHODS

A total of 60 specimens made from PETG aligner films (CA Clear Aligner, Scheu Dental, Iserlohn, Germany) were divided into three groups (immersed in distilled water, subjected to accelerated ageing by thermocycling, control). These groups were again divided and tensile testing was performed for all groups at 22 and at 37 °C. Young's modulus (E), 0.2% offset yield strength (R_p02) and ultimate tensile strength (UTS) were evaluated. Water absorption was determined using an analytical scale.

RESULTS

All treated specimens showed water absorption, whereby specimens that were thermocycled absorbed 48% more water than the immersed ones. Young's modulus and UTS were significantly lower for all three groups at 37 °C compared to the corresponding groups tested at 22 °C. Thermocycled and immersed groups showed a significantly lower Young's modulus compared to the control group tested at the same temperature. The mean R_p02 was statistically different when comparing the control group tested at 22 °C to the one tested at 37 °C.

CONCLUSIONS

The results of this study add to the understanding of the clinically well-known degradation of orthodontic aligners during wear time. Extreme alternating temperatures along with warming up to intraoral temperature and water absorption can reduce the material's Young's modulus and may therefore promote a decrease of resulting orthodontic forces.

In Vitro Evaluation of Experimental Self-Adhesive Orthodontic Composites Used to Bond Ceramic Brackets

The aim of this study was to evaluate the degree of conversion (DC), flexural strength (FS), and shear bond strength (SBS) of ceramic brackets bonded to enamel with experimental self-adhesive orthodontic composites. Functional monomers 10-methacryloyloxy-decyl-dihydrogen-phosphate (MDP) and glycerol-dimethacrylate-phosphate (GDMA-P) were used in experimental composites. They were compared to the same composite without an acidic monomer (negative control) and with enamel acid-etching prior to adhesive application (positive control). DC was evaluated by Raman micro-spectroscopy. Flexural three-point bending testing was performed in a universal testing machine. Ceramic brackets were bonded to bovine enamel and SBS was evaluated before and after 2000 thermal-cycles. Fracture patterns were surveyed with manual removal with specific pliers and analyzed by SEM. Statistics was performed using ANOVA and Tukey’s test (p < 0.05). DC of the control composite was significantly higher (p < 0.001) than that of GDMA-P and MDP. FS showed no significant difference between composites (p = 0.451). Regarding adhesion, the positive control (8.47 ± 0.88 MPa) and MDP (7.07 ± 2.69 MPa) obtained higher overall results. The predominant fracture pattern of the positive control and MDP was mixed while it was adhesive for further groups. The MDP-containing orthodontic composite attained similar adhesion to a conventional three-step orthodontic bonding system, with a similar fracture pattern and mechanical properties. Nevertheless, the presence of acidic functional monomers reduced the DC.

Shear Bond Strength of Self-Adhesive Flowable Composite, Conventional Flowable Composite and Resin-Modified Glass Ionomer Cement to Primary Dentin

Objectives:

This study aimed to compare the shear bond strength (SBS) of self-adhesive and conventional flowable composites and resin-modified glass-ionomer cement (RMGIC) to primary dentin.

Materials and Methods:

In this in vitro, experimental study, the buccal surface of 48 primary canine and first molar teeth was longitudinally sectioned to expose dentin. The teeth were randomly divided into three groups (n=16) of 37.5% phosphoric acid+ OptiBond+ Premise Flow composite (group 1), Vertise Flow composite (group 2) and RMGIC (group 3). A plastic cylindrical mold was placed on the exposed dentin and filled with restorative materials. The samples were then immersed in distilled water at 37°C for 24 hours, subjected to 1000 thermal cycles between 5–55°C and underwent SBS test. The mode of failure was determined under a stereomicroscope. Data were analyzed using one-way ANOVA and Tukey’s test.

Results:

A significant difference was noted in SBS of the groups (P<0.05). The SBS of conventional flowable composite was significantly higher that of RMGIC and self-adhesive flowable composite (P<0.05). The difference in SBS of RMGIC and self-adhesive flowable composite was not significant (P>0.05). Failure at the dentin-restoration interface (adhesive failure) had the highest frequency in groups 1 and 2. The frequency of adhesive failure was 100% in group 3.

Conclusion:

Within the limitations of this study, the conventional flowable composite yielded the highest SBS to primary dentin. Self-adhesive flowable composite and RMGIC showed the lowest SBS with no significant difference with each other.

Effects of different primers on indirect orthodontic bonding: Shear bond strength, color change, and enamel roughness

Objective

We aimed to perform in-vitro evaluation to compare 1) shear bond strength (SBS), adhesive remnant index (ARI), and color change between self-etched and acid-etched primers; 2) the SBS, ARI and color change between direct and indirect bonding; and 3) the enamel roughness (ER) between 12-blade bur and aluminum oxide polisher debonding methods.

Methods

Seventy bovine incisors were distributed in seven groups: control (no bonding), direct (DTBX), and 5 indirect bonding (ITBX, IZ350, ISONDHI, ISEP, and ITBXp). Transbond XT Primer was used in the DTBX, ITBX, and ITBXp groups, flow resin Z350 in the IZ350 group, Sondhi in the ISONDHI group, and SEP primer in the ISEP group. SBS, ARI, and ER were evaluated. The adhesive remnant was removed using a low-speed tungsten bur in all groups except the ITBXp, in which an aluminum oxide polisher was used. After coffee staining, color evaluations were performed using a spectrophotometer immediately after staining and prior to bonding.

Results

ISONDHI and ISEP showed significantly lower SBS (p < 0.01). DTBX had a greater number of teeth with all the adhesive on the enamel (70%), compared with the indirect bonding groups (0–30%). The ER in the ITBX and ITBXp groups was found to be greater because of both clean-up techniques used.

Conclusions

Direct and indirect bonding have similar results and all the primers used show satisfactory adhesion strength. Use of burs and polishers increases the ER, but polishers ensure greater integrity of the initial roughness. Resin tags do not change the color of the teeth.

Bonding performance of self-adhesive flowable composites to enamel, dentin and a nano-hybrid composite

This study aimed to analyze bond strengths of self-adhesive flowable composites on enamel, dentin and nano-hybrid composite. Enamel, dentin and nano-hybrid composite (Venus Diamond, Heraeus Kulzer, Germany) specimens were prepared. Three self-adhesive composites (Constic, DMG, Germany; Fusio Liquid Dentin, Pentron Clinical, USA; Vertise Flow, Kerr Dental, Italy) or a conventional flowable composite (Venus Diamond Flow, Heraeus Kulzer, Germany, etch&rinse technique) were applied to enamel and dentin. Nano-hybrid composite specimens were initially aged by thermal cycling (5000 cycles, 5-55 °C). Surfaces were left untreated or pretreated by mechanical roughening, Al₂O₃ air abrasion or silica coating/silanization. In half of the composite specimens, an adhesive (Optibond FL, Kerr Dental, Italy) was used prior to the application of the flowable composites. Following thermal cycling (5000 cycles, 5-55 °C) of all specimens, shear bond strengths (SBS) and failure modes were analyzed (each subgroup n = 16). Statistical analysis was performed by ANOVAs/Bonferroni post hoc tests, Weibull statistics and χ ²-tests (p < 0.05). SBS (MPa) of the self-adhesive composites on enamel and dentin were significantly lower (enamel: < 5, dentin: < 3) than those of the conventional flowable composite (enamel: 13.0 ± 5.1, dentin: 11.2 ± 6.3), and merely adhesive failures could be observed. On the nano-hybrid composite, SBS were significantly related to the pretreatment. Adhesive application improved SBS of the conventional, but not of the self-adhesive composites. The self-adhesive composite groups showed less cohesive failures than the reference group; the occurence of cohesive failures increased after surface pretreatment. Bonding of self-adhesive flowable composites to enamel and dentin is lower than bonding to a nano-hybrid composite.

Comparison of traditional and simplified methods for repairing CAD/CAM feldspathic ceramics

PURPOSE

To evaluate the adhesion to CAD/CAM feldspathic blocks by failure analysis and shear bond strength test (SBSt) of different restorative systems and different surface treatments, for purpose of moderate chipping repair.

MATERIALS AND METHODS

A self-adhering flowable composite (Vertise Flow, Kerr) containing bi-functional phosphate monomers and a conventional flowable resin composite (Premise Flow, Kerr) applied with and without adhesive system (Optibond Solo Plus, Kerr) were combined with three different surface treatments (Hydrofluoric Acid Etching, Sandblasting, combination of both) for repairing feldspathic ceramics. Two commercial systems for ceramic repairing were tested as controls (Porcelain Repair Kit, Ultradent, and CoJet System, 3M). SBSt was performed and failure mode was evaluated using a digital microscope. A One-Way ANOVA (Tukey test for post hoc) was applied to the SBSt data and the Fisher's Exact Test was applied to the failure analysis data.

RESULTS

The use of resin systems containing bi-functional phosphate monomers combined with hydrofluoric acid etching of the ceramic surface gave the highest values in terms of bond strength and of more favorable failure modalities.

CONCLUSION

The simplified repairing method based on self-adhering flowable resin combined with the use of hydrofluoric acid etching showed high bond strength values and a favorable failure mode. Repairing of ceramic chipping with a self-adhering flowable resin associated with hydrofluoric acid etching showed high bond strength with a less time consuming and technique-sensitive procedure compared to standard procedure.

Trends in restorative composites research: what is in the future?

Clinical trials have identified secondary caries and bulk fracture as the main causes for composite restoration failure. As a measure to avoid frequent reinterventions for restoration replacement, composites with some sort of defense mechanism against biofilm formation and demineralization, as well as materials with lower susceptibility to crack propagation are necessary. Also, the restorative procedure with composites are very time-consuming and technically demanding, particularly concerning the application of the adhesive system. Therefore, together with bulk-fill composites, self-adhesive restorative composites could reduce operator error and chairside time. This literature review describes the current stage of development of remineralizing, antibacterial and self-healing composites. Also, an overview of the research on fiber-reinforced composites and self-adhesive composites, both introduced for clinical use in recent years, is presented.

Investigation of the Er: YAG laser and diamond bur cavity preparation on the marginal microleakage of Class V cavities restored with different flowable composites

The purpose of this study was to evaluate the efficiency of the Er:YAG laser and diamond bur cavity preparation on the marginal microleakage of Class V cavities. Group 1: bur preparation (bp) + Vertise Flow (VF); Group 2: laser preparation (lp) + VF; Group 3: bp + Adper Easy One (AEO) + Filtek Ultimate Flowable Composite (FUFC); Group 4: lp + AEO + FUFC; Group 5: bp + Clearfil S3 Bond (CSB) + Clearfil Majesty Flow (CMF); Group 6: lp + CSB + CMF. Data were analyzed by Kruskal-Wallis and Mann-Whitney U tests (p < .05). More microleakage was observed in cervical regions compared to occlusal regions in all groups (p < .05). No significant difference was observed among all groups in terms of occlusal and cervical surfaces, respectively (p > .05). The use of the Er:YAG laser for cavity preparation with different adhesive systems and flowable composites did not influence microleakage.

Shear Bond Strength and Tooth-Composite Interaction With Self-Adhering Flowable Composites

PURPOSE

To evaluate the tooth-composite interaction (A) and shear bond strength (SBS; B) of self-adhering flowables.

METHODS AND MATERIALS

(A) Thirty-two human molars with one Class V cavity were restored with Vertise Flow (VF), Fusio Liquid Dentin (FLD), an experimental self-adhering flowable (EF), or Adper Prompt-L-Pop/Filtek Supreme XT Flowable (PLP). Teeth were prepared according to laboratory standard and stored in water (24 hours, 37°C). Microleakage (ML; percentage interface length at enamel [E]/dentin [D]) and tooth-composite interaction were investigated. (B) The buccal surface of 160 embedded human molars was abraded to expose an enamel/dentin area of diameter ≥3 mm. Composite specimens were produced on enamel/dentin with VF, FLD, EF, or PLP. Prior to loading, 80 samples were water stored (24 hours, 37°C) and 80 thermocycled (5°C-55°C, 1500 cycles). The SBS was measured, and failure modes were classified by scanning electron microscopy.

STATISTICS

Kruskal-Wallis, Mann-Whitney U, and Fisher exact tests were performed (α=0.05).

RESULTS

(A) At enamel margins, EF and VF showed significantly lower ML than did FLD and PLP (p_i≤0.009; 81%-89%); in dentin, lower values resulted with FLD and VF compared with PLP and EF (p_i≤0.01; 77%-94%). Adhesive tags at E were consistently verifiable with EF and VF but irregularly with FLD and PLP. At D, tags were detectable with all systems. (B) In all groups, SBS decreased by up to 97% after thermocycling. It was generally diminished with self-adhering flowables (E: 50%-98%, D: 59%-98%; p_i<0.02). More cohesive defects were observed with PLP (p_i<0.009).

CONCLUSION

Tooth-composite morphology and bond strength indicate that the clinical use of self-adhering flowables must be pursued cautiously.

The Effect of Energy Densities on the Shear Bond Strength of Self-Adhering Flowable Composite to Er:YAG Pretreated Dentin

Objective. To investigate the shear bond strength of self-adhering flowable resin composite, to dentin, after exposing it to Er:YAG laser radiation, at different energy densities. Materials and Methods. Sixty freshly extracted human third molars were randomly divided into five groups (n = 12). In the control group, dentin was left unirradiated, whereas, in the other four groups, dentin was irradiated with Er:YAG laser in noncontact mode (MSP mode = 100 µs; 10 Hz; beam diameter: 1.3 mm; speed of 1 mm/second; air 6 mL/min; and water 4 mL/min), and respectively, with the following level of energy (50 mJ, 60 mJ, 80 mJ, and 100 mJ). Then, self-adhering flowable resin composite was bonded to all prepared dentin surfaces. Shear bond strength (SBS) was applied and fractured surfaces were examined using scanning electron microscopy. Results. SBS values showed significant differences in 60 mJ (P < 0.05) compared to other groups. Morphological evaluation revealed tags or plugs in dentinal tubules, especially when 60 mJ and 80 mJ were used. All four groups tended to leave more residues on the dentin surface, than the control group. Conclusion. Er:YAG dentin irradiation may enhance SBS of the self-adhering flowable resin composite when it is used at the appropriate low level of energy density.

Pediatric patients tolerance: a comparative study about using of Er:YAG laser and self-adhesive flowable composite for treatment of primary decayed teeth

Aim

To verify the tolerance of children aged between 3 and 8 years, having class I caries and treated with Er:YAG Laser in association with a new self-adhesive flowable resin in comparison with a high-speed diamond bur and a conventional flowable resin treatment.

Methods

A group of 80 healthy children (43 male and 37 female) ranging in age from 3 to 8 years, who had been diagnosed with at least one active occlusal non-cavitated superficial carious lesions in first or second deciduous molars, were selected for the present study. They were divided in 4 groups: group A: Class I occlusal cavities prepared using an Er:YAG laser and a self-adhesive flowable resin; Group B: Class I occlusal cavities prepared using an Er:YAG laser and a conventional flowable resin; Group C: Class I occlusal cavities prepared using a high-speed diamond bur and a self-adhesive flowable resin; Group D: Class I occlusal cavities prepared using a high-speed diamond bur and a conventional flowable resin. Before and after the treatments the patient tolerance was tested with the modified Wong-Baker pain level scale.

Results

In the first group, the tolerance rate was 95% with 0 score (no hurt) for 19 patients; in Group D, the tolerance rate was 75%. Just one child of group D experienced hurting worst because of non cooperative patient.

Conclusion

From these results it emerged that, although the limits of the study, Er:Yag laser in association with self-adhering composite, is very effective in pediatric dentistry and is a good treatment option especially for non cooperative patients.

Orthodontic bracket bonding to glazed full-contour zirconia

Objectives

This study evaluated the effects of different surface conditioning methods on the bond strength of orthodontic brackets to glazed full-zirconia surfaces.

Materials and Methods

Glazed zirconia (except for the control, Zirkonzahn Prettau) disc surfaces were pre-treated: PO (control), polishing; BR, bur roughening; PP, cleaning with a prophy cup and pumice; HF, hydrofluoric acid etching; AA, air abrasion with aluminum oxide; CJ, CoJet-Sand. The surfaces were examined using profilometry, scanning electron microscopy, and electron dispersive spectroscopy. A zirconia primer (Z-Prime Plus, Z) or a silane primer (Monobond-S, S) was then applied to the surfaces, yielding 7 groups (PO-Z, BR-Z, PP-S, HF-S, AA-S, AA-Z, and CJ-S). Metal bracket-bonded specimens were stored in water for 24 hr at 37℃, and thermocycled for 1,000 cycles. Their bond strengths were measured using the wire loop method (n = 10).

Results

Except for BR, the surface pre-treatments failed to expose the zirconia substructure. A significant difference in bond strengths was found between AA-Z (4.60 ± 1.08 MPa) and all other groups (13.38 ± 2.57 - 15.78 ± 2.39 MPa, p < 0.05). For AA-Z, most of the adhesive remained on the bracket.

Conclusions

For bracket bonding to glazed zirconia, a simple application of silane to the cleaned surface is recommended. A zirconia primer should be used only when the zirconia substructure is definitely exposed.

Orthodontic bracket bonding without previous adhesive priming: A meta-regression analysis

OBJECTIVE

To determine the consensus among studies that adhesive resin application improves the bond strength of orthodontic brackets and the association of methodological variables on the influence of bond strength outcome.

MATERIALS AND METHODS

In vitro studies were selected to answer whether adhesive resin application increases the immediate shear bond strength of metal orthodontic brackets bonded with a photo-cured orthodontic adhesive. Studies included were those comparing a group having adhesive resin to a group without adhesive resin with the primary outcome measurement shear bond strength in MPa. A systematic electronic search was performed in PubMed and Scopus databases.

RESULTS

Nine studies were included in the analysis. Based on the pooled data and due to a high heterogeneity among studies (I(2)  =  93.3), a meta-regression analysis was conducted. The analysis demonstrated that five experimental conditions explained 86.1% of heterogeneity and four of them had significantly affected in vitro shear bond testing. The shear bond strength of metal brackets was not significantly affected when bonded with adhesive resin, when compared to those without adhesive resin.

CONCLUSIONS

The adhesive resin application can be set aside during metal bracket bonding to enamel regardless of the type of orthodontic adhesive used.

Shear bond strength and debonding characteristics of a new premixed self-etching with a reference total-etch adhesive

Background

To determine the shear bond strength and adhesive remnant index of a new premixed self-etching primer and adhesive (Tectosan, BonaDent, Germany) for orthodontic appliances in comparison to a reference total-etch system Transbond XT.

Methods

Bovine incisors were embedded in resin and randomly divided into two groups of 16 samples each. Brackets (Discovery, Dentaurum, Germany) were bonded in group 1 (total-etch-system, Transbond XT) and in group 2 (self-etch-system, Tectosan) with curing light for 40 s. Shear bonding strengths were measured after 24 h of storage in distilled water at 37 °C with a Zwicki 1120 testing machine (Zwick Roell, Germany). A force was applied on the bracket base at the wings in occluso-gingival direction. Then the adhesive remnant index (ARI) was determined.

Results

No statistical differences on SBS were found for both bonding agents (p = 0.63). ARI scores however differed statistically significantly (p = 0.035): in the total-etch group more adhesive remained on the teeth, whereas in the self-etch group more adhesive remained on the brackets. There were no visible enamel damages in both groups.

Conclusions

No differences in the shear bond strength were found between both bonding agents. In our study the self-etch-system shifted the adhesive remnant index from more adhesive on the teeth to more adhesive on the bracket - as other already published self-etch systems did - with the new benefit of not increased enamel damages. Tectosan might therefore be a promising alternative to adhesive systems.

Shear Bond Strengths of Brackets Bonded with a New Self-Adhering Resin Composite

Purpose

To determine the shear bond strength (SBS) of orthodontic brackets bonded with a self-adhering resin composite.

Methods

45 freshly extracted mandibular incisors were randomly divided into 3 groups (n = 15 per group). Brackets were bonded with 3 bonding systems and cured with an LED light. Brackets were bonded with a new self-adhering resin cement in the study group. A conventional etch-and-rinse adhesive system and a self-etching adhesive system were used for comparison. After bonding, the SBS of the brackets were tested with a universal testing machine.

Results

Analysis of variance indicated a significant difference between groups (p<0.001). The highest values for SBS were measured in group I (21.80 ± 2.57 MPa). The SBS was significantly lower in groups II and III than in group I (P<.001). The lowest values for SBS were measured in group III (5.90 ± 0.90 MPa). SBS was significantly higher in group II than in group III (p<0.001).

Conclusions

The self-adhering adhesive system showed a clinically insufficient SBS, whereas the SBS of conventional etch-and-rinse adhesive system and the self-etching adhesive system were significantly higher and clinically sufficient.

Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material

PURPOSE

The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material.

MATERIALS AND METHODS

A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05.

RESULTS

Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001).

CONCLUSION

Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used.

Shear bond strength of self-adhering flowable composite on dentin with and without application of an adhesive system

PURPOSE

The aim of this study was to evaluate the shear bond strength (SBS) of conventional and self-adhering flowable resin composites on the dentin surfaces of primary and permanent teeth and to evaluate the effect of the application of an adhesive system under self-adhering flowable resin composite on SBS.

METHODS

Prepared permanent and primary tooth dentin surfaces were randomly distributed into 3 groups according to application protocols as follows: group 1: Vertise Flow; group 2: OptiBond + Filtek Ultimate; and group 3: OptiBond + Vertise Flow. A universal testing machine was used to measure SBS of prepared specimens, and data were analyzed using 1-way ANOVA and Tukey test.

RESULTS

Statistically significant differences were observed among all groups for primary and permanent teeth (P<0.05). The highest values were observed in group 2, followed by group 3, in both permanent and primary teeth. SBSs of all groups were significantly higher for permanent teeth than for primary teeth (P<0.05).

CONCLUSION

Although SBS values of Vertise Flow groups were lower than those for conventional flowable resin composite groups, with further developments in material technology, self-adhering materials could be promising materials especially for pediatric dentistry.

Shear bond strength of a self-adhering flowable composite when used for lingual retainer bonding

OBJECTIVE

The goal of this work was to assess the shear bond strength (SBS) and fracture mode of a self-adhering flowable composite when used after thermocycling for lingual retainer bonding.

MATERIALS AND METHODS

A total of 80 human mandibular incisor teeth were categorized into four equal groups: group 1: Vertise™ Flow (VF) without acid etching; group 2: VF with acid etching; group 3: VF with a self-etching bonding agent accompanied by an additional acid etching; group 4: Transbond LR control. Either VF or Transbond LR was applied to the lingual surface of the teeth by packing the material into cylindrical plastic matrices to simulate the lingual retainer bonding area. After all teeth were thermocycled (5000 cycles, 5 and 55 °C), fracture modes were examined under × 20 magnification. The SBS data were assessed via analysis of variance (ANOVA) and Tukey's tests. Fracture modes were analyzed by the χ(2) test at a significance level of 0.05.

RESULTS

Statistically significant differences in SBS values between groups (p < 0.001) were observed. Group 4 exhibited the highest (14.63 ± 1.36 MPa) and group 1 the lowest SBS (2.67 ± 1.35 MPa) values. Statistically significant differences were noted in fracture modes between groups 1, 3, and 4 (p < 0.001). In all the self-adhering flowable composite groups, the adhesive type (tooth-composite interface) fracture occurred more frequently than cohesive and mixed-type fractures.

CONCLUSION

When applied to bond lingual retainers to unetched enamel or with self-etching bonding agent accompanied by an additional acid etching, Vertise™ Flow resulted in a significant decrease in bond strength.

Effect of different surface treatments on the microtensile bond strength of two self-adhesive flowable composites

The aim of this study was to evaluate the effect of different surface treatments on the microtensile bond strength (μTBS) of two different self-adhesive flowable composite materials (SACs) to dentin. Forty extracted human molars were horizontally flattened to expose the dentin surfaces. The teeth were divided into eight groups according to the surface treatments (acid etching, Er:YAG laser quantum square pulse (QSP) mode, and Er:YAG laser medium-short pulse (MSP) mode at 10 Hz, 1.2 W, 120 mJ, and control-SiC) and SAC type (Vertise Flow and Fusio Liquid Dentin) (n = 5). Light cured 4-mm-high composite build-ups were made on the dentin surfaces, and the specimens were sectioned into serial sticks (n = 15). Later, the specimens were attached to microtensile testing machine and tensile force was applied at a crosshead speed of 1 mm/min until failure occurred. The failure modes were evaluated using a stereomicroscope at ×40 magnification, and one sample from each group was used for scanning electron microscopy (SEM) evaluation. The data were analyzed with two-way ANOVA and Tukey's HSD test (α = 0.05). In all surface treatment groups along with the control groups, Vertise Flow showed better μTBS than the Fusio Liquid Dentin with the exception of the Er:YAG MSP mode surface treatment (p < 0.05). Etching with phosphoric acid and the Er:YAG QSP mode surface treatment significantly increased the μTBS of Vertise Flow (p < 0.05). Etching with phosphoric acid, Er:YAG QSP mode surface treatment, and Er:YAG MSP mode surface treatment significantly increased the μTBS of Fusio Liquid Dentin (p < 0.05). The μTBS of Vertise Flow was higher than the μTBS of Fusio Liquid Dentin. The Er:YAG laser irradiation increased the μTBS of both self-adhesive flowable resin composites in two pulse modes tested (MSP or QSP). However, the highest μTBS was recorded when Vertise Flow was applied with acid etching.

Bonding effectiveness of self-adhesive composites to dentin and enamel

Self-adhesive composites (SACs) are claimed to bond to tooth substrate without a separate adhesive. Bonding effectiveness data are however still limited.

OBJECTIVES

In SubProject 1, the hypothesis was tested that the micro-tensile bond strength (μTBS) to dentin of two flowable SACs was alike that of a one-step self-etch adhesive (1-SEa) combined with a flowable composite (flowC). In SubProject 2, the hypothesis was tested that the nature of the smear layer did not affect the μTBS of the SACs to dentin/enamel.

METHODS

SubProject 1: The μTBS to bur-cut dentin of two SACs (Fusio Liquid Dentin, Pentron; Vertise Flow, Kerr) was measured and compared to that of four 1-SEa/flowC combinations (AdheSe One/Tetric EvoFlow, Ivoclar Vivadent; Adper Prompt L-Pop/Filtek Supreme XT Flowable, 3M ESPE; iBond/Venus flow, Heraeus Kulzer; Xeno V/X-flow, Dentsply) and of one 3-step etch-and-rinse adhesive (3-E&Ra: OptiBond FL, Kerr) combined with Premise Flowable (Kerr). The effect of pre-etching dentin with phosphoric acid on the μTBS of the SAC Vertise Flow (Kerr) was measured as well. SubProject 2: The μTBS of the two SACs and one 1-SEa/flowC combination (Adper Prompt L-Pop/Filtek Supreme XT Flowable, 3M ESPE) to either bur-cut or SiC-paper ground dentin/enamel was measured. The effect of pre-etching enamel with phosphoric acid on the μTBS of the SAC Vertise Flow (Kerr) was also measured.

RESULTS

SubProject 1: The μTBS to dentin of both SACs was significantly lower than that of the 1-SEa/flowC and the 3-E&Ra/flowC combinations, of which the latter performed best. The SAC Fusio Liquid Dentin (Pentron) bonded significantly better to dentin than Vertise Flow (Kerr), except when dentin had additionally been pre-etched with phosphoric acid. SubProject 2: Surface smear did not interfere with bonding of the SACs to dentin/enamel, while their μTBS remained significantly lower than that of the 1-SEa/flowC combination. Prior phosphoric-acid etching of dentin/enamel significantly ameliorated the bonding effectiveness of Vertise Flow (Kerr).

SIGNIFICANCE

The bonding effectiveness of flowable SACs underscores that of 1-SEa's and one 'gold-standard' 3-E&Ra when combined with their proprietary flowable composite. Consequently, routine clinical application of SACs should be carefully considered.