F1000ResearchF1000Research2046-1402F1000 Research LimitedLondon, UK10.12688/f1000research.12306.2Research ArticleArticlesMethods of Clinical Decision-MakingInterfacial microscopic examination and chemical analysis of resin-dentin interface of self-adhering flowable resin composite
[version 2; peer review: 2 approved]
HamdyTamer M.InvestigationMethodologyProject AdministrationWriting – Original Draft PreparationWriting – Review & Editinghttps://orcid.org/0000-0003-0948-194Xa12
Endodontics, Restorative & Dental Materials Research Department, National Research Centre (NRC), Giza, Dokki, 12622, Egypt
Dr. Tamer Hamdy Dental Clinic, Giza, Egyptdr_tamer_hamdy@yahoo.com
Competing interests: No competing interests were disclosed.
Background: The newly introduced self-adhering flowable resin-composites decrease the required time for application by incorporation of an acidic adhesive monomer, thus reducing the number of the steps, but its bonding is still uncertain. The aim of this study was to evaluate the interfacial microscopic examination and chemical analysis at the resin-dentin interface of a self-adhering flowable resin composite (Vertise-Flow) versus a total-etch (Te-Econom Plus) resin composite, using an etching agent (Eco-Etch gel) and bonding agent (Single Bond Universal).
Methods: Sixteen freshly extracted sound human posterior teeth were used. The teeth were randomly divided into two groups: 8 specimens per type of composite. Standard-shaped class V cavities were prepared on the buccal surface. One group was restored by Te-Econom Plus resin composite by total-etch technique using Eco-Etch gel, which was applied to dentine for 15 seconds, followed by rinsing, drying and bonding agent application (Single Bond Universal). The other group restored directly with self-adhering resin composite (Vertise-Flow) without application of etch or bond. Curing was done for 20 seconds using a light emitting diode light curing unit. Evaluation of the resin-dentin interface was done microscopically by examination of marginal gap distance in μm using scanning electron microscope (SEM), and chemical analysis of silver particles was observed using SEM with energy-dispersive X-ray spectrometry after 24 hours of specimen storage in ammoniacal silver nitrate.
Results: Regarding marginal gap distance (μm) and silver atomic % mean values, teeth restored with self-adhering resin composite (Vertise-Flow) showed significantly higher mean values than the multi-step etch and rinse resin composite group (5.2
vs 0; 12.2
vs 8.2, respectively).
Conclusions: Resin-dentin bonding using total-etch resin composite technique was more effective than self-adhering flowable resin composite (Vertise-Flow) regarding marginal gap formation and penetration of silver particles. Further studies for bond strength could be performed.
Self-adheringtotal-etchbonding systemresin compositegap distanceresin-dentin interfaceThe author(s) declared that no grants were involved in supporting this work.Amendments from Version 1
In response to Dr. Rania El-Saady Badawy's report, I have re-phrased some of the text in the Introduction, Methods, Results and Discussion sections.
Introduction
Adhesive dentistry has seen a paradigm shift from the invasive to be minimally invasive, due to a revolution in bonding systems. There are great demands for simplified restorative materials. A new self-adhering flowable resin composite (Vertise™ Flow Self-Adhering Flowable Composite, Kerr Dental, USA), was recently introduced onto the market. Bonding of flowable composites to tooth structure is achieved by incorporation of an acidic adhesive monomer into the material
1. It is still a big challenge to seal the resin-dentin interface
2,
3.
The total-etch (etch and rinse) technique is a widely accepted technique to improve bonding of dental resins to tooth structure
2. The dentin bonding mechanism is based on the micro-mechanical interlocking of the infiltrated resin monomers into porosities created in demineralized organic part
4. Debonding of restorations may arise from gap-formation at the resin-dentin interface and hence recurrent caries, discoloration and tooth pain may follow
5. Thus sufficient marginal seal should be obtained. Recently, an innovative self-adhesive and flowable resin composite was developed. These materials are claimed to eliminate the need for a separate step of bond-application, finally simplifying the restorative procedure. Therefore, the aim of this study was to evaluate the sealing performance of this new material.
MethodsPreparation of specimens
After attaining written informed consent from each patient to use their extracted teeth in research, sixteen sound human molar teeth were extracted in a private dental clinic (Dr. Tamer Hamdy Dental Clinic), which were randomly divided into two groups (eight specimens per group). Standard-shaped class V cavities (3 mm width, 3 mm length, 2 mm of depth) were prepared in the teeth using a #169L carbide bur (KG Sorensen, Brazil) on the buccal surface. One group’s (Group A) cavities were filled with Te-Econom Plus
® (Ivoclar Vivadent, Africa) resin composite after etching and bond application. The etching agent, Eco-Etch gel (Ivoclar Vivadent), was applied to dentine for 15 seconds, followed by rinsing and drying. After rinsing, a bonding agent (Single Bond Universal, 3M ESPE, USA) was applied to teeth for 20 seconds, afterwards the teeth were air-dried for 5 seconds and light-cured for 10 seconds. Finally, the Te-Econom Plus resin composite was applied. The other group’s (Group B) cavities were filled with self-adhering resin composite (Vertise-Flow), which was applied without etch or bond. Curing was done for 20 seconds using a light emitting diode (LED) light curing unit (Satelec, Acteon, France).
Interfacial microscopic examination
All teeth were stored in distilled water for 24 hours at 37°C. Subsequently, the specimens were vertically sectioned with a diamond saw (Isomet, Buehler Ltd., USA) under water lubrication into approximately 1mm thick slab composed of tooth structure bonded to resin composite. These were examined for marginal gap distance in μm using scanning electron microscope (SEM; Model Quanta 250 FEG; FEI, Thermo Fisher Scientific, USA): accelerating voltage 30 K.V., magnification 14x up to 1000000 and resolution for Gun.1n, to ensure high brightness and resolution at low accelerating voltage.
Chemical analysis of the interface
Specimens slab were then placed in freshly prepared 50 weight % ammoniacal silver nitrate solution for an additional 24 hours at 37°C in the dark. Ammoniacal silver nitrate solution (pH=9.5) was prepared according to
Tay et al. (2002)6. After 24 hours of storage in silver nitrate solution, the silver impregnated specimens were rinsed thoroughly in distilled water and placed in photo-developing solution for 8 hours under a fluorescent light (200 Watt)
3.
The specimens were then observed under environmental SEM Model Quanta 250 FEG attached with energy-dispersive X-ray (EDX; Inspect S 50, FEI, Netherlands): accelerating voltage 30 K.V., magnification 4000x and resolution for Gun.1n. The Blackscattered backscattered electron mode was used for elemental analysis of the atomic silver %.
Statistical analysis
Numerical data were explored for normality using Kolmogorov-Smirnov and Shapiro-Wilk tests, followed by Student’s t-test to compare between both groups. The significance level was set at P ≤ 0.05. Statistical analysis was performed with IBM
®SPSS
® Version 20 for Windows (SPSS Inc., IBM Corporation, USA).
Results
Regarding marginal gap formation, Group A showed a significantly lower mean gap distance values than Group B (p<0.001), as shown in
Table 1 and
Figure 1 and
Figure 2.
Marginal gap formation (µm) between groups of teeth restored with different composites.
Group A, treated with total-etch technique; Group B, treated with self-adhering resin composite. Mean and standard deviation (SD) values and results of Student’s t-test for the comparison between gap distances are shown (n=8/group).
Group A
Group B
P-value
Mean
SD
Mean
SD
0.0
0.0
5.2
0.3
<0.001
*
*: Significant at P ≤ 0.05
Selected scanning electron microscopy shows absence of gap formation in dentin for teeth treated with total-etch technique.
Image representative of 8 teeth.
Selected scanning electron microscopy shows presence of gap formation in dentin for teeth treated with a self-adhering resin composite.
Image representative of 8 teeth.
The SEM with EDX analysis results revealed significantly lower mean silver atomic % values for Group A compared to Group B (p< 0.001) A selected, as shown in
Table 2 A. Selected SEM/EDX analysis is shown in
Figure 3 and
Figure 4.
Chemical analysis of the interface between groups of teeth restored with self-adhering resin composite.
Group A, treated with total-etch technique; Group B, treated with self-adhering resin composite. Mean and standard deviation (SD) values and results of Student’s t-test for the comparison between silver atomic % values are shown (n=8/group).
Group A
Group B
P-value
Mean
SD
Mean
SD
8.2
0.4
12.2
0.7
<0.001
*
*: Significant at P ≤ 0.05
Selected scanning electron microscopy/energy-dispersive X-ray analysis at the resin-superficial dentin interfaces in teeth treated with total-etch technique.
Image representative of 8 teeth.
Selected scanning electron microscopy/energy-dispersive X-ray analysis at the resin-superficial dentin interface in teeth treated with self-adhering resin composite.
Image representative of 8 teeth.
Discussion
A proper marginal sealing of restoration is essential to improve the durability of resin composite/bonding systems
7. Most of the clinical studies assessing the performance of an adhesive system use class V cavities
8. EDX analysis permits identification of silver particles, thus giving an indication about the chemical analysis of the interface
9.
Our results revealed better sealing ability of composites treated with multi-step etch and rinse technique, presenting lower marginal gap formation and lower penetration of silver particles compared to Vertise-Flow. This may be indicate that the presence of exposed collagen fibers could increase micromechanical interlocking of the bonding agent within the dentin surface
10. The poorer sealing of Vertise-Flow may be due to included adhesive monomer, the glycerol that etches instead of bonds to hydroxyapatite
11.
Conclusions
Total-etch resin composite technique was more effective regarding marginal gap formation and penetration of silver particles as compared to a flowable resin composite (Vertise-Flow). Further studies on bond strength should be undertaken.
Data availability
The data referenced by this article are under copyright with the following copyright statement: Copyright: � 2017 Hamdy TM
Data associated with the article are available under the terms of the Creative Commons Zero "No rights reserved" data waiver (CC0 1.0 Public domain dedication).
Dataset 1: Raw values for silver atomic % in teeth treated with total-etch technique (Group A) and self-adhering resin composite (Group B) (n=8/group/method). doi,
10.5256/f1000research.12306.d17706112
Dataset 2: Scanning electron microscopy (SEM) showing gap formation (raw values included on the images) and SEM/energy-dispersive X-ray analysis (EDX) at the resin-superficial dentin interface in teeth treated with total-etch technique (Group A) and self-adhering resin composite (Group B) (n=8/group/method). doi,
10.5256/f1000research.12306.d17706213
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Data Source10.5256/f1000research.13966.r27027Reviewer response for version 2El-Saady BadawyRania1Referee
Department of Dental Materials, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
Competing interests: No competing interests were disclosed.
The following points need to be corrected, otherwise it is approved
is based on the micro-mechanical interlocking of the infiltrated resin monomers into porosities created
by demineralized inorganic part of dentin 4.
Comment: created
indemineralized inorganic part....
Chemical analysis of the interface Specimens slabs were then placed in freshly prepared 50 weight/volume % ammoniacal silver nitrate solution for an additional 24 hours at 37°C in the dark.
Comment: Specim
en slab
s were placed.......
lower mean gap distance values than Group B (p<0.001), as shown in Table 1 and Figure 1 and Figure 2.
Comment: and Figur
es 1 and 2
The SEM with EDX analysis results revealed that Group A showed significantly lower mean silver atomic % values than Group B (p<0.001), as shown in Table 2 A. Selected SEM/EDX analysis is shown in Figure 3 and Figure 4.
Comment: The SEM with EDX analysis results revealed significantly lower mean silver atomic % values for Group A compared to Group B (p< 0.001). A selected SEM/EDX analysis is shown in Figu
res 3 and 4.
A proper
marginal sealing is essential to improve the durability of resin composite/bonding systems 7
Comment:A proper marginal se
al is essential
This may be attributed to the fact that phosphoric acid included in acid-etch step demineralized the smear layer, exposing the collagen fibers of superficially demineralized dentin. These could increase micromechanical interlocking of the bonding agent within the dentin surface 10
Comment: The presence of exposed collagen fibers could increase....
Is the work clearly and accurately presented and does it cite the current literature?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Yes
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
Reviewer Expertise:
NA
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
HamdyTamerNational Research Centre, Egypt, Egypt
Competing interests: No competing interests were disclosed.
18102017
Thanks for your concern, corrections done.
10.5256/f1000research.13321.r26333Reviewer response for version 1BadrNadia A.1Referee
Department of Dental Biomaterials, Faculty of Oral and Dental Medicine, Cairo University, Cairo, Egypt
Competing interests: No competing interests were disclosed.
The scientific idea of this article to evaluate the adaptability of resin/dentine interface of the most commonly used direct aesthetic restorative material is superb.
The article lacks the name of the company & country of the main investigated material (flowable composite, Vertise-Flow).
Despite the used method is well known for detection of nanoleakage of restorative materials, it is smartly employed for assessment of adaptability of composite at resin/dentine interface.
The suggestions is logical but it is preferable to be separate item not involved in context of conclusion section.
Summary:
The article is presented clearly & accurately
The study design is appropriate
Sufficient details were provided except the name of the company & country of the investigated material (Vertise-Flow)
The used method for detection of marginal gap is smartly employed
The data are reproducible
And the unique conclusion is obvious
The suggestion is promising for further researches
Is the work clearly and accurately presented and does it cite the current literature?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Yes
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
Reviewer Expertise:
Dental biomaterials
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.
HamdyTamerNational Research Centre, Egypt, Egypt
Competing interests: No competing interests were disclosed.
18102017
Many thanks for your valuable comments, I do the required corrections, belong to "the suggestions is logical but it is preferable to be separate item not involved in context of conclusion section" I do that according to editorial request according to the journal role
10.5256/f1000research.13321.r26488Reviewer response for version 1El-Saady BadawyRania1Referee
Department of Dental Materials, Faculty of Dentistry, Suez Canal University, Ismailia, Egypt
Competing interests: No competing interests were disclosed.
After reviewing the entire manuscript, several modifications were added to different parts of the manuscript.
For the Introduction part, it shortly covered the idea of investigated resin composites describing the aim of the study.
Materials and Methods described steps and method of slab preparation (missing a few details).
Results were objectively presented.
The results were vaguely discussed.
This manuscript is approved for publication after elaborating the changes required.
Specific Comments:
Bonding is achieved by incorporation of an acidic adhesive monomer into the flowable composites
1.
Comment: Bonding of flowable composites to tooth structure is achieved by incorporation of an acidic adhesive monomer into the material.
It is still a big challenge to seal the resin-dentin interface, due to the heterogeneous nature of dentin, the wet tubular structure, composition and surface morphology and or improperly designed adhesives
2,3
Comment: Too long sentence
The total-etch (etch and rinse) technique is a widely accepted technique to improve bonding of dental resins
2.
Comment: improve bonding of dental resins to tooth structure
...is based on the micro-mechanical interlocking of the infiltrated resin monomers into porosities created
by demineralized inorganic part of dentin
4.
Comment: created in demineralized organic part....
Restoration debonding may arise from gap formation at the resin-dentin interface and hence recurrent caries, discoloration and tooth pain
5
Comment: Debonding of restorations may arise from gap-formation ..........., discoloration and tooth pain may follow
These materials are claimed to eliminate the need for a separate bonding application step, thus simplifying the restorative procedure
Comment: to eliminate the need for a separte step of bond-application, finally simplifying the restorative procedure
Thus, the aim of this study was to evaluate the sealing performance of this new material
Comment: Therefore, the aim of.....
Preparation of specimens. After attaining written informed consent from each patient to use their extracted teeth in research
Comment: Why should we get a patients approval to work on extracted teeth?? You should better start with: Sixteen sound human molar teeth.......
.
..sixteen sound human posterior molar teeth were extracted in a private
Comment: Only say human molar teeth- it is known that molars are posterior
(eight specimens per group). Standard-shaped class V cavities (3x3 mm, 2 mm of depth) were prepared
Comment: Dimensions of the cavity are unclear
One group’s (Group A) cavities were filled with Te-Econom Plus® (Ivoclar Vivadent, Africa) resin composite after etching and bonding application.
Comment: and bond application
A bonding agent (Single Bond Universal, 3M ESPE, USA) was applied to the teeth for 20 Seconds
Comment: After rinsing, a bonding agent ......... was applied to the teeth for 20 sec
...teeth for 20 seconds, then air-dried for 5 seconds, then light-cured for 10 seconds.
Comment: was applied to teeth for 20 seconds, afterwards the teeth were air-dried for 5 sec and light-cured for 10 sec
...under water lubrication into approximately 1mm thick slabs.
Comment: Slab of what??? Please explain specific composition the slab. Please mention that it is a slab composed of tooth structure bonded to resin composite of any type!!!
Chemical analysis of the interface. Specimens slab were then placed in freshly prepared 50 weight/volume % ammoniacal silver nitrate solution for an additional 24 hours at 37°C in the dark.
Comment: Specimen slabs were placed.......weight or volume percent????
Ammoniacal silver nitrate solution (pH=9.5) was prepared according to the protocol of Tay et al. (2002)
6.
Comment: prepared according to Tay
et al
After 24 hours of storage in ammoniacal silver nitrate, the silver impregnated specimens were then rinsed thoroughly in distilled water and placed in photo-developing
Comment: storage in silver nitrate solution, the silver impregnated specimens were rinsed. Thoroughly
The specimens were then observed under environmental SEM Model Quanta 250 FEG attached with energy-dispersive X-ray (EDX; Inspect S 50, FEI, Netherlands): accelerating voltage 30 K.V., magnification 4000x and resolution for Gun.1n.
Comment: he treated specimens were observed.
Backscattered electron mode was used for elemental analysis of the atomic silver %.
Comment: The Blackscattered ......
...followed by Student’s t-test to compare between the two groups.
Comment: to compare between both groups
lower mean gap distance values than Group B (p<0.001), as shown in Table 1 and Figure 1 and Figure 2.
Comment: and Figures 1 and 2
The SEM with EDX analysis results revealed that Group A showed significantly lower mean silver atomic % values than Group B (p<0.001), as shown in Table 2 A. Selected SEM/EDX analysis is shown in Figure 3 and Figure 4.
Comment: revealed significantly lower mean silver atomic % values for Group A compared to Group B (p< 0.001) A selected..... in Figures 3 and 4.
Table 1. Marginal gap formation (μm) between groups of teeth treated with different composites
Comment: groups of teeth restored with different...
Figure 1. Selected scanning electron microscopy shows absence of gap formation in dentin in teeth treated with total etch technique.
Comment: in dentin for teeth treated with....
Figure 2. Selected scanning electron microscopy shows presence of gap formation in dentin in teeth treated with self-adhering resin composite.
Comment: in dentin for teeth........ with a self-adhering ....
Table 2. Chemical analysis of the interface between groups of teeth treated with different composites.
Group A, treated with total-etch technique; Group B, treated with self-adhering resin composite.
Comment: restored with self-adhering resin composite
Dataset 1. Raw values for silver atomic % in teeth treated with total-etch technique
(Group A) and self-adhering resin composite (Group B) (n=8/group/method)
Comment: Group (A), …
Dataset 2. Scanning electron microscopy (SEM) showing gap formation (raw values included on the images) and SEM/energy dispersive X-ray analysis (EDX) at the resin-superficial dentin interface in teeth treated with total-etch technique (Group A) and self-adhering resin composite (Group B) (n=8/group/method)
Comment: Group (A), …
A proper
marginal sealing is essential to improve the durability of resin composite/bonding systems
7
Comment: sealing of what???
From the present results, it was obvious that the multi-step etch and rinse technique provides better sealing regarding
Comment: Our results revealed better sealing ability of composites treated with multi-step etch and rinse technique, presenting lower marginal gap formation and lower penetration of silver particles compared to Vertise-Flow.
This may be attributed to the fact that phosphoric acid included in acid-etch step demineralized the smear layer, exposing the collagen fibers of superficially demineralized dentin.
These could increase micromechanical interlocking of the bonding agent within the dentin surface
10
Comment: Presence of exposed collagen fibers could increase....
The poorer sealing of Vertise-Flow may be due to the included adhesive monomer, which is called glycerol phosphate dimethacrylate “GPDM”, that etches instead of bonds to hydroxyapatite
11.
Comment: included adhesive monomer, the glycerol.........
Further studies for bond strength could be performed. It is important to emphasize that this study ignored the effect of oral condition,
Comment: Further studies on bond strength should be undertaken.
Is the work clearly and accurately presented and does it cite the current literature?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Yes
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
Reviewer Expertise:
NA
I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.
HamdyTamerNational Research Centre, Egypt, Egypt
Competing interests: No competing interests were disclosed.
6102017
Thanks for your valuable revision. Corrections done
Belong to your comment
Comment: Why should we get a patients approval to work on extracted teeth?? You should better start with: Sixteen sound human molar teeth......
It was done according to journal editor revision due to the rule of the journal.