| Abstract|| |
Context: Class V cavity presents a clinical challenge in the field of restorative dentistry as the margin placement is partially in enamel and partly in cementum, and the trouble associated with this design is the microleakage at the tooth restoration interface. Aims: To evaluate and compare marginal microleakage in Class V cavities when restored with flowable composite and Cention-N restorative material. Methods and Material: This in-vitro study was performed on 30 human maxillary premolars, which were extracted for orthodontic reasons. Class V cavities were prepared on the buccal surfaces of each tooth. After application of seventh-generation bonding agent (3M ESPE, Single Bond Universal Adhesive), the teeth were divided into two groups of 15 each and restored with flowable composite (3M ESPE Filtek Z350 XT) and Cention-N (Ivoclar Vivadent) and were subjected to thermocycling. The teeth were then immersed in 0.1% Rhodamine B dye for 48 h. They were sectioned longitudinally into mesial and distal parts with the help of an isomet diamond saw. The sections were observed under a confocal laser scanning microscope (CLSM). Statistical Analysis Used: The results were subjected to statistical analysis using the Mann–Whitney U test and Pearson's Chi-square test. Results: The analysis showed statistically significant results among the groups. Cention-N showed lesser microleakage, which was statistically significant when compared to flowable composite (P = 0.005). Conclusions: Cention-N showed significantly lesser leakage and better adaptation than flowable composite.
Keywords: Bonding agent, Cention-N, Class V cavity preparation, confocal microscope, flowable composites
|How to cite this article:|
Shenoi PR, Kokane VB, Thawale HV, Kubde RR, Gunwal MK, Shahu SP. Comparing marginal microleakage in Class V cavities restored with flowable composite and Cention-N using confocal microscope-an in-vitro study. Indian J Dent Res 2021;32:348-53
|How to cite this URL:|
Shenoi PR, Kokane VB, Thawale HV, Kubde RR, Gunwal MK, Shahu SP. Comparing marginal microleakage in Class V cavities restored with flowable composite and Cention-N using confocal microscope-an in-vitro study. Indian J Dent Res [serial online] 2021 [cited 2022 May 26];32:348-53. Available from: https://www.ijdr.in/text.asp?2021/32/3/348/338136
| Introduction|| |
One of the most important features of adhesive restorative materials is marginal adaptability, which plays an important role in the success of restoration of class V cavities. Substandard marginal adaptability leads to the formation of gaps at the tooth-restorative interface resulting in microleakage. Clinically, microleakage is the major cause for the failure of restorations, especially in Class V cavities, as margins of these cavities are generally located in dentin/cementum.
Since 1996, flowable composite resins are the most common resin materials that are recommended for restoring Class V cavities because they have good aesthetic properties, have low viscosity,,, are easier to place, and more self-adaptable as compared to conventional composite resins., A recent advance is the introduction of self-adhering flowable composite resins, which are a product of combining an all-in-one bonding system and flowable composite resin. Based on previous studies, these have the highest elastic modulus, hardness, and degree of conversion compared to other conventional flowable composite resins. In addition, they exhibited higher hygroscopic dimensional expansion and more water sorption, compared to other flowable composite resins.
New materials and techniques have been developed to fulfil the requirements of clinicians for ideal restorative material. Cention-N [Ivoclar Vivadent, India] an 'alkasite' restorative material is a new category of filling material, which is a subgroup of composite resin material similar to compomers and ormocers. Cention-N is available in the tooth shade A2 and is a dual-cured restorative material available in powder and liquid form. One scoop of powder is used for one drop of liquid, corresponding to a powder/liquid weight ratio of 4.6:1. The powder comprises various glass fillers, initiators, and pigments. These glass fillers release different alkaline ions such as fluoride, calcium, and hydroxyl that can neutralize acidic ions surrounding the restoration. The liquid contains four different dimethacrylate monomers that interconnect (cross-links) during polymerization resulting in strong mechanical properties and good long-term stability.
The long-term release of fluoride ions in acidic conditions is higher from Cention-N in comparison to traditional GIC. They also release hydroxide ions and calcium ions, which further help prevent demineralization of the tooth substrate.
To date, no research has been carried out to evaluate and compare microleakage of Cention- N and flowable composites in Class V tooth preparations using confocal laser scanning microscope. The null hypothesis tested was that there is no significant difference between Cention-N and flowable composite resin in terms of microleakage at the tooth-restoration interface.
| Subjects and Methods|| |
Thirty extracted human maxillary premolars were included in the study [Figure 1]. Human premolars extracted for orthodontic reasons were included in the study, and the teeth with previous restorations, visible cracks, decay, fracture, abrasion or structural deformities were excluded from the study. The teeth were cleaned and stored as per the Occupational Safety and Health Administration (OSHA) and Centers for Disease Control and Prevention (CDC) guidelines. (Ethics Comm.Reg.No. -ECR/885/Inst/MH/2017).
Preparation of sample
Class V cavities, measuring 5 mm in mesiodistal width, 2 mm occlusogingivally, and 1.5 mm in depth, were prepared on the buccal surface of each tooth with the use of a carbide fissure bur (010 SS White, Switzerland) under air and water spray. The dimensions of the prepared cavities were standardized using Vernier caliper. The cavities were prepared to have their centre at the cemento-enamel junction. A new bur was used for every 4th tooth.
The teeth were then randomly divided into two groups of 15 each.
- Group I: Flowable Composite
Seventh-generation bonding agent (3M ESPE, Single Bond Universal Adhesive) was applied and light-cured (Bluephase-N, Ivoclar Vivadent) for 20 s, then flowable composite (3M ESPE Filtek Z350 XT) was dispensed and light-cured for 20 s
- Group II:- Cention-N
Seventh-generation bonding agent (3M ESPE, Single Bond Universal Adhesive) was applied and light-cured (Bluephase-N, Ivoclar Vivadent) for 20 s, then Cention-N (Ivoclar Vivadent, India) was mixed and light-cured for 20 s.
Finishing and polishing of the restorations were performed after 24 h using Sof-Lex Finishing and Polishing Kit (3M ESPE, St Paul, USA), and the samples were stored in distilled water at 37°C for 24 h.
Microleakage Testing: The specimens were then subjected to 500 thermocycles at 5°C and 55°C. The cycle in each temperature lasted for 1 min with a transfer time of 10 s. The apices were sealed using composite, and all the teeth were painted with two coats of nail varnish to within 1 mm of the margins of the restorations to limit dye penetration to cavity margins. Teeth were then immersed in 0.1% Rhodamine B dye for 48 h. After separating the radicular portion, specimens were rinsed and sectioned mesiodistally using an Isomet diamond saw.
Microleakage was measured with confocal microscopy (Confocal Fluorescence Imaging Microscope, Leica TCS-SP5, and DM 6000-CFS) [Figure 2] in the fluorescent mode. Evaluation of microleakage was carried out by a blinded researcher to avoid observational bias.
The degree of dye penetration was identified according to the criteria given by Wahab et al.
0 = no penetration;
1 = penetration to the enamel or cementum aspect of the preparation wall;
2 = penetration to the dentin aspect of the preparation wall, but not including the pulpal floor;
3 = penetration including the pulpal floor.
Statistical analysis was performed using (SPSS) version 21 for Windows (SPSS Inc, Chicago, IL) descriptive quantitative data were expressed in mean, standard deviation, and in percentage, respectively. Mann–Whitney test was used to compare mean microleakage between the two groups. Confidence interval set at 95% and the probability of alpha error set at 5%. Power of the study set at 80%.
| Result|| |
A total of 30 maxillary premolars were evaluated under a confocal laser scanning microscope, and the scores were calculated.
Mann–Whitney U test revealed a significant difference in the comparison of two restorative materials with respect to microleakage (P = 0.005) [Table 1]. Group II showed less microleakage which was statistically significant when compared to Group I (P < 0.05).
|Table 1: Comparison of Mean (±S.D.) for microleakage restored with flowable composite resin, and cention-N using a confocal microscope, respectively|
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Comparing of microleakage type/scores [Graph 1] in Class V cavity filled with flowable composite resin, and Cention -N using confocal microscope respectively, it was found that Group I (flowable composite) have significantly higher microleakage scores (P < 0.05) at enamel and dentin/restoration interface as compared to Group II (Cention-N), which showed higher microleakage score 0 (no penetration) and at enamel interface.
[Figure 3] shows fluorescence between restoration and dentinal tubules in Group I, (flowable composite) which indicates a poor adaptation of restorative material and microleakage.
|Figure 3: CLSM image of flowable composite restorative material with an arrow indicating the presence of fluorescence between restoration and dentinal tubules|
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[Figure 4] shows minimal microleakage between restoration and dentinal tubules in Group II (Cention -N) with good adaptation of the restorative material.
|Figure 4: CLSM image of Cention- N restorative material with an arrow indicating the presence of fluorescence between restoration and dentinal tubules|
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| Discussion|| |
Marginal adaptability is an important factor for the success of restoration, and it ensures the long-term stability of the restoration. It depends on several factors, including bonding to tooth structure, polymerization shrinkage, volumetric contraction, the elastic modulus of composite resin, the thermal expansion coefficient of composite resin and water sorption. Stresses resulting from polymerization shrinkage give rise to marginal gaps, which lead to microleakage around tooth/restorations interface.
In the present study, Class V cavities were prepared with a high C-factor due to the high ratio of bonded surfaces-to-unbonded free surfaces. Microleakage was assessed and compared using a confocal laser scanning microscope. Confocal laser scanning microscopy (CLSM) is a technique used for visualizing subsurface tissue characteristics and scans the sample, sequentially point by point and line by line, and assembles the pixel information into one image. Thermocycling was done because it is a widely used method to simulate temperature changes that take place in the oral environment.
Based on the results of the present study, there was a significant difference in microleakage among the two groups. The flowable composite had statistically significant microleakage scores (P = 0.005) as compared to Cention-N, refuting the null hypothesis of the study. This is consistent with the results reported by Samanta S et al. (2017) who reported significant differences between the microleakage of flowable composite resins and Cention-N in class V cavities under a stereomicroscope.
The flowable composite showed higher microleakage at dentin restoration interface (60%) when compared to Cention-N (20%) and lesser microleakage at enamel/cementum restoration interface (13%). Scanning electron microscope images have shown that self-adhering flowable composite resin has a relatively superficial reaction with the tooth structure and does not form a clear hybrid layer. Due to such poor reaction between self-adhering flowable composite resins and tooth structures, several studies have reported that the use of bonding agents increases the marginal seal of these composite resins at dentinal walls.
These resins have filler loading reduced to 37%–53% (volume), which eventually leads to higher polymerization shrinkage and resultant volumetric contractions ranging between 2.6% and 4.8%. This shrinkage results in corresponding stresses which may cause mechanical failure at the composite/tooth interface, debonding, and subsequent microleakage. Hakimeh et al. (2000), demonstrated that polymerization contraction stresses might be the primary cause of microleakage when the restorations were subjected to thermocycling.
In addition to filler content, the relative proportion of Bis-GMA, TEGDMA, and other monomers are reported to affect volumetric shrinkage. The resin matrix of most flowable composites is a blend of Bis-GMA and TEGDMA. TEGDMA's low molecular weight offers a large number of double bonds and provides a high degree of cross-linking leading to greater shrinkage. The aforementioned may explain in part the slightly higher shrinkage of flowable composite [Filtek Z350 XT] (2.35%) as compared to that of Cention-N.
Cavities restored with Cention-N showed score 0 (no penetration) in 46.6% of samples and score 1 (penetration to the enamel or cementum) in 33% of samples as the interface is largely sealed as an acid resistant, resin-dentin interdiffusion zone, i.e., hybrid layer. Our findings are similar to that of the study conducted by Manuela Lopes.
Chole et al. 2019, in vitro study, reported that Cention-N showed highest flexural strength compared to other restorative materials. The highest flexural strength of Cention-N can be attributed to two factors 1) Higher filler loading and filler content 2) Monomer composition containing a combination of urethane dimethacrylate (UDMA), tricyclodecan-dimethanol dimethacrylate (DCP), an aromatic aliphatic-UDMA, and polyethylene glycol 400 (PEG-400) DMA instead of Bis GMA and TEGDMA. Due to the sole use of cross-linking methacrylate monomers in combination with a stable, efficient self-cure initiator, Cention-N exhibits a high polymer network density and degree of polymerization over the complete depth of the restoration.
It also includes a special patented filler Isofiller (partially functionalized by silanes) which acts as a shrinkage stress reliever and minimizes shrinkage force, whereas the organic/inorganic ratio as well as the monomer composition of the material is responsible for the low volumetric contraction. Due to its low elastic modulus (10 GPa), these Isofillers within Cention-N acts like spring (i.e. it expands slightly as the forces between the fillers grow during polymerization) among the standard glass fillers, which have a higher elastic modulus of 71 GPa. Ultimately, the volumetric shrinkage and shrinkage stress in Cention-N are reduced during polymerization, allowing bulk increments to be placed.
The results of our study are in accordance with Arjun Kini et al. (2018) and Mazumdar P et al. (2019) who stated that Cention-N, demonstrated the least microleakage in comparison with various other restorative materials. In summary, the results of our study indicate that Cention-N is better than the flowable composites in terms of marginal adaptation in Class V restorations. The Cention-N has performed better than the flowable composite in both the enamel/cementum and dentin margins.
| Clinical Implications|| |
Based on the present in-vitro study, the dentist can utilize the Cention-N material as a restorative material for class V cavities, which is better in terms of good marginal adaptation and prevent postoperative sensitivity, secondary caries, and pulpitis when compared to flowable composite.
The present study did not compare the tested restorations by subjecting these restorations to cyclic occlusal loading. The present study was done under in-vitro conditions; hence, future studies should be focused on conducting in-vivo conditions to evaluate the clinical behaviour of the tested restorative materials.
| Conclusion|| |
Within the limitation of this in vitro study, the following conclusions can be drawn.
- In Class V restorations, both the restorative material showed microleakage.
- Among both the groups marginal microleakage scores of novel restorative material, Cention-N was minimal and within acceptable limits.
- Cention-N offers a promise for the future as a direct posterior restorative material.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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Dr. Himani V Thawale
VSPM Dental College and Research Centre, Digdoh Hills, Hingna Road, Nagpur - 440 0019, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]