|Year : 2018 | Volume
| Issue : 3 | Page : 140-147
Evaluation of marginal seal of different composite restored class V cavity preparations with different cavosurface margins
Israa O Nagy, Hussein Y El-Sayed, Magda E Shalaby
Department of Conservative Dentistry, Faculty of Dentistry, Tanta University, Tanta, Egypt
|Date of Submission||16-Sep-2017|
|Date of Acceptance||10-Jan-2018|
|Date of Web Publication||10-Oct-2018|
Israa O Nagy
Department of Conservative Dentistry, Faculty of Dentistry, Tanta University, Tanta
Source of Support: None, Conflict of Interest: None
The aim was to evaluate and compare the marginal seal of Class V composite restored with different cavosurface margins.
Materials and methods
A standardized Class V cavity, 4 mm wide, 3 mm high, and 3 mm deep, were prepared on the buccal surface of 60 extracted molars with the occlusal margin located in enamel and the gingival margin located in dentin-cementum 1.0 mm below the cementoenamel junction. The teeth were divided into two main groups: group I, cavosurface angle was 90° butt-joint; group II, beveled enamel and dentin cavosurface margins. Each group subdivided into three subgroups: group A, restored with Filtek bulk-fill flowable composite. Group B, restored with Filtek bulk-fill posterior composite. Group C, restored with Filtek Z250XT Universal composite. Restorations were cured with LED light curing unit. All specimens were stored in 37°C and 100% humidity for 24 h, thermo cycled for 600 cycles with baths held between 5 and 55°C, a dwell time of 30 s and a transfer time of 10 s. The restored coronal portion were cut 3 mm beyond the cementoenamel junction, each specimen were sectioned in bucco–lingual direction through the center of each restoration resulting in two sections. The cut surfaces were examined at the occlusal and gingival margins using a stereomicroscope at 30× magnification with an attached digital camera.
There was significant difference in microleakage between the three tested materials where flowable bulk-fill showed a lower degree of microleakage than posterior bulk-fill and conventional composite at P value of less than 0.05 and there was a degree of significant in microleakage at occlusal and gingival margin where occlusal margins showed the a lowest degree of microleakage.
There was significant inverse correlation between flowable bulk-fill and conventional composite and high significant between occlusal and gingival margin and there is no need for a bevel in Class V carious lesions.
Keywords: bulk-fill composite, bulk-fill flowable composite, cavosurface configuration margins, microleakage
|How to cite this article:|
Nagy IO, El-Sayed HY, Shalaby ME. Evaluation of marginal seal of different composite restored class V cavity preparations with different cavosurface margins. Tanta Dent J 2018;15:140-7
|How to cite this URL:|
Nagy IO, El-Sayed HY, Shalaby ME. Evaluation of marginal seal of different composite restored class V cavity preparations with different cavosurface margins. Tanta Dent J [serial online] 2018 [cited 2018 Dec 9];15:140-7. Available from: http://www.tmj.eg.net/text.asp?2018/15/3/140/243077
| Introduction|| |
Since, their initial introduction in the 1960s, composite resins have been undergone improvement in all areas, including esthetics, wear, and handling. However, high polymerization shrinkage continues to represent major disadvantages . Previous research has shown polymerization shrinkage to lead to bond failure and microleakage of resin composite restorations . Consequently, these shrinkage stresses could lead to abundant clinical problems such as microleakage , which is a matter of concern because it leads to staining at the margins of restorations, recurrent caries, hypersensitivity, and pulp pathology .
Resin-based restorative materials have been a common choice of dental practitioners for restoring cervical lesions due to their esthetic quality and ability to be bonded to tooth structure. However, cervical lesions have been a restorative challenge for dentists for many years. The complex morphology of Class V cavities with margins partly in enamel and partly in dentin presents a challenging scenario for the restorative material . The primary problem associated with the restoration of this kind of cavity is leakage at the gingival margin located in dentin ,. Several restorative techniques have been proposed to minimize the polymerization shrinkage consequences and achieve a better marginal adaptation in Class V cavities ,, because the bond strength to enamel is usually greater than to the dentin .
The primary rational behind the use of flowable composites is the formation of an elastic layer that may compensate for polymerization shrinkage stresses . Some studies demonstrated no statistically significant difference between flowable and hybrid composites with respect to microleakage at cervical and occlusal margins . Clinicians still desire easier and quicker composite restorations with less shrinkage and significant advances have been made in composite formulations that target less shrinkage and are more user friendly; these include highly filled flowable, bulk-fill flowable, and bulk-fill nonflowable composites. Flowable composite was introduced in the 1990s, and it was promoted because it is injectable, which is regarded as a desirable handling property and allows simplification of the placement procedure ,.
Typically, flowable composite has a lower filler content and higher volume of resin matrix when compared with nonflowable composite, so the first generation flowable composite was applied as a cavity liner or Class V restoration due to the low-elastic modulus. However, the recent generations of flowable composite have higher filler content and are claimed to have improved mechanical properties; thus, they are indicated not only as a cavity liner but also for larger posterior restorations .
The latest version of flowable composites for simplifying restorative procedure is the bulk-filling posterior flowable are intended to be placed and bulk-cured in one increment up to 4 mm. The matrix composition of these two bulk-fill flowables and bulk-fill nonflowable composites is based on modified urethane dimethacrylate (UDMA). The manufacturer says that it differs from conventional composites by incorporating stress-decreasing resin technology, which comprises a high-molecular weight polymerization modulator in the matrix structure. This unique molecular structure contributes to the delay of the gel point which represents an increase of viscosity through network formation, and it allows for a greater pregelation-phase time .
Also, the new technology is based on changes in monomer chemistry by modifying the Bowen monomer – Bis-GMA: 2, 2-bis [4-(2-hydroxy-3-methacryloxypropoxy) phenyl] propane – to create monomers with lower viscosity , and further could achieved by incorporating hydroxyl-free Bis GMA, aliphatic UDMAs, partially aromatic UDMA, or highly branched methacrylate . The outcomes of these changes in monomer and composite organic matrix have been shown to reduce polymerization shrinkage and stresses over 70% ,,.
Along with the bulk-fill flowables, the bulk-fill nonflowable composite was recently launched with the claim that it would substitute for not only the conventional nonflowable composite but also for the bulk-fill flowables that are required for the final 2 mm when using the incremental layering technique. According to the manufacturer's information, this new bulk-fill nonflowable composite will achieve full-depth bulk-fill curing up to 4 mm without a superficial capping layer of strong composite, unlike the bulk-fill flowables. Some studies states that a new fillers (prepolymers) act as shrinkage stress reliever to minimize polymerization shrinkage ,.
The cavosurface margin bevel plays an important role in the reduction of marginal leakage, improved esthetics, and increased adhesion. However, when beveling is needed in a small-sized Class V conventional cavity preparation, it changes the configuration of the cavity in a way that causes reduced retention . The issue of beveling the cavosurface margin of Class V preparations has been under discussion since the introduction of dentin bonding agents designed to increase the adhesion of composite to dentin . So the aim of this study is to evaluate the marginal seal of contemporary tooth colored restorative systems in the gingival and occlusal margins of cavity preparations with and without a bevel.
| Materials and Methods|| |
Sixty caries-free, freshly extracted molars from diabetic patients aged 50–70 years old were selected for this study. The teeth were cleaned from tissue remnants and debris using a hand scalar and polished with pumice then stored in sterile normal saline solution for less than 3 months at room temperature to prevent their dehydration . Only the roots were embedded into acrylic resin block below cementoenamel junction (CEJ). A standardized Class V cavity, 4 mm wide (mesial-distal), 3 mm high (occlusal-gingival), and 3 mm deep, were prepared on the buccal surface of each tooth with the occlusal margin located in enamel and the gingival margin located in dentin-cementum 1.0 mm below the CEJ. Cavities were prepared using #D8 diamond fissure burs in water-cooled and high-speed handpiece.
The teeth were randomly divided into two main groups (n = 30) based on the configuration of the cavosurface margins into group I: conventional cavity with no bevel on the enamel or dentin. Group II: beveled enamel and dentin cavosurface margins using a flame shaped diamond bur. The single bond universal one step self-etch adhesive system (3M ESPE, Minnesota, USA) was applied to all prepared teeth and rubbed for 20 s then gently air dried for approximately 5 s to evaporate the solvent then cured with LED curing unit (http://www.CE-marking.EU; Wellkang Ltd, London, UK) according to manufacturer's instruction prior to application of the resin composite.
Each group of 30 cavities were further randomly subdivided into three subgroups (groups A, B, C; n = 10) according to the type of composite resin used for restoring the preparations. The two groups IA and IIA were restored with Filtek bulk-fill flowable composite (3M ESPE) and the two groups IB and IIB were restored with Filtek bulk-fill posterior composite3 (3M ESPE, Minnesota, USA) with composite of 3 mm thickness in a single step while the other two groups IC and IIC were restored with Filtek Z250XT Universal composite3 (3M ESPE, Minnesota, USA) with incremental layering technique then all specimens were cured with LED light curing unit.
After immediate finishing and polishing with diamond finishing burs and flexible discs3, the teeth were stored in 37°C and 100% humidity for 24 h. The specimens were then thermo cycled for 600 cycles with baths held between 5 and·55°C), a dwell time of 30 s, and a transfer time of 10 s .
The samples were dried and then all external surfaces of each specimen were isolated with two layers of nail polish except for an area within 1 mm around the restoration. The restored coronal portion of teeth was then immersed in 2% methylene blue solution for 24 h at room temperature . After storage the teeth were gently washed and scrubbed to remove any surface traces of the dye and dried. The restored coronal portion was cut 3 mm beyond the CEJ, each specimen was sectioned in bucco–lingual direction through the center of each restoration resulting in two sections . The cut surfaces were examined at the occlusal and gingival margins using a stereomicroscope at 30× magnification with an attached digital camera.
Images were transferred to the computer using computer software (Cell^A) and were saved and analyzed. Depth of longitudinal dye penetration in millimeter were then measured at the composite tooth interface from the cavosurface margin for both the occlusal and gingival margins inward to axial wall. Measurements for all specimens were done blindly by one calibrated rater . The collected data were tabulated and analyzed using SPSS (statistical package of the social sciences; SPSS Inc., Chicago, Illinois, USA).
A written consent were taken from these patients after the study were approved by the Ethics Committee of Tanta University to ensure their agreement to use their teeth in current study.
| Results|| |
Stereomicroscope examination 30× show depth of dye penetration in micron for both occlusal and gingival margins of restored cavities with different cavosurface margins of the different main groups restored with two bulk-fill composites and one control nanohybrid composite group and data were collected and analyzed by using Cell^A software as mentioned in [Figure 1].
|Figure 1: Column chart representing the mean Microleakage depth values (micron) in class V cavities restored by the tested composite materials with different cavosurface margin configurations.|
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Depth of dye penetration of occlusal and gingival margins of cavities with different cavosurface configuration of each tested composite type
From [Figure 2] it was observed that, the mean value of microleakage at the gingival margins in group (IA, IB, IC) restored with Filtek flowable bulk-fill composite, Filtek bulk-fill posterior composite and Filtek Z 250 XT composite respectively with butt-joint recorded a higher significant values of microleakage than the occlusal margins at P value of less than 0.001. Moreover group (IIA, IIB, IIC) with beveled cavosurface margins, the gingival margins recorded a higher significant values of microleakage than the occlusal margins at P value of less than 0.05.
|Figure 2: Stereo- microscope examination 30X digital image magnification on the readings show depth of dye penetration in micron.|
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Depth of dye penetration between beveled and nonbeveled cavities at occlusal and gingival margins for each material
At the occlusal margins and gingival margins, it was found that the mean value of microleakage by using Filtek flowable bulk-fill composite with butt-joint cavity margins recorded a nonsignificant higher dye penetration than the mean value of microleakage with beveled cavity margins. Also, the mean value of microleakage by Filtek bulk-fill posterior with butt-joint cavity margins recorded a nonsignificant higher dye penetration than the mean value of microleakage with beveled cavity margins. Moreover, concerning mean value of microleakage by using Filtek Z 250 XT composite with butt-joint cavity margins recorded a nonsignificant higher dye penetration than the mean value of microleakage with beveled cavity margins as shown in [Table 1].
|Table 1: Statistical analysis, mean, and SD of dye penetration depth values at the occlusal and gingival margins in class V cavity with different cavosurface margins of the three tested materials|
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Depth of dye penetration between three tested restorative materials by using either butt-joint or beveled cavosurface margins
It was found that at the gingival and occlusal margins in butt-joint and beveled cavities, the highest mean value of microleakage was recorded by group restored with Filtek bulk-fill posterior followed by group restored with Filtek Z 250 XT while the lowest mean microleakage depth value was found by group restored with Filtek flowable bulk-fill.
Tukey's test was performed to find out which material responsible for the recorded difference and found that the responsibility fall on group A using Filtek flowable bulk-fill as there was statistical significant difference was recorded between it and other subgroups (groups B and C) using Filtek bulk-fill posterior and Filtek Z 250 XT, while there were no significant differences between subgroups (groups B and C). As shown in [Table 2] and [Table 3].
|Table 2: Statistical analysis, mean, and SD of dye penetration depth values in class V cavities with butt-joint and bevel of the three tested materials|
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|Table 3: Tukey's test between three tested materials using butt-joint and beveled cavosurface margins at a level of significance (P>0.05)|
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| Discussion|| |
A proper marginal sealing is essential to improve the longevity of composite resin restorations. Class V cavities were chosen in this study because they remain a challenge for restorative procedures. Thus, most of the clinical studies evaluating the performance of an adhesive system use class V cavities. The reason for studying Class V cavities was that (a) it is easier to standardize the preparation of Class V cavities, (b) Class V restoration margins are located in enamel as well as in dentin, (c) preparation and restoration of Class V lesions are minimal and relatively easy, thereby somewhat reducing practitioner variability, and (d) Class V cavities have unfavorable C-factors, resulting in high-contraction scores within an adhesively fixed resin material. Moreover, these cavities frequently present gingival margins in the dentin, consisting of an additional challenge to obtain a proper marginal sealing ,.
The bulk-fill type of composite materials is placed in up to 4-mm thick increments and can be adequately cured up to that depth. The composition of these materials has been altered in various ways to allow for increased depth of curing while having less shrinkage and shrinkage stress than previous generations of composite materials. Recent studies support that the bulk-fill materials result in significant reduction of polymerization shrinkage and, satisfactory bond strength in comparison to the conventional types of composite resins. Thus, problems related to polymerization shrinkage such as gap formation, secondary caries, pulp irritation, postoperative sensitivity during chewing, or cusp deflection could be minimized ,.
Microleakage is usually evaluated with in-vitro models. A number of techniques including bacterial, chemical or radioactive tracer molecules infiltration are available. Color dye penetration studies are the most commonly employed techniques. Microleakage studies have been carried out both in vivo and in vitro, but in-vitro studies evaluating the integrity and durability of the marginal seal of different resin composites at cavity margins are more common ,.
In the present study, none of the composite tooth interfaces either at occlusal and gingival margins showed an absence of dye infiltration, although the degree of infiltration differed in relation to the type of composite material and cavosurface margins. The dye penetration was significantly affected by the marginal substrate and its interaction with the resin material. The depth of infiltration on enamel was significantly lower than that on dentin in all tested materials. This finding is consistent with previous reports regarding adhesion on enamel and dentin. The presence of less dye penetration and better marginal seal on enamel is related to the low organic content of enamel compared with dentin; dentin has a complex structure rich in organic molecules, making adhesion to dentin more variable and difficult to achieve and this agreed with Scotti et al.  who used nanohybrid high-viscosity composite resin, flowable resin and new bulk-fill flowable resin and found that dye penetration was significantly affected by the marginal substrate and its interaction with the resin material.
Also, Ameri et al. , found that the gingival margin showed significantly more microleakage than the enamel margin (P < 0.05) using flowable resin-based composite. Silveira de Araujo et al.  said that enamel margins exhibited lower leakage than dentin margins (P < 0.01) in class V cavities filled with hybrid composite restoration. On contrary, Tuncer et al.  evaluated the adaptation at the cervical margin by dye penetration of three tested material resin composite (G-aenial posterior), bulk-fill flowable composite (x-tra base), bulk-fill fiber-reinforced composite (everX Posterior) in class II endodonticlly treated teeth, and reported that, there were statistically significant differences observed between the microleakage of the occlusal and gingival margins for all three of the treatment groups; the microleakage scores for the gingival margins were significantly lower than the microleakage scores for the occlusal margins. This finding also agree with Demirci et al.  who concluded and demonstrated that one step self-etch bond resulted in higher microleakage for enamel margins compared with dentinal margins.
Beveling of the cavosurface margins has been employed for many years as an accepted modification for composite restorations in permanent anterior teeth. The bevel exposes more enamel rods for bonding . It is known that a beveled margin with enamel prisms is a configuration more favorable than a butt-joint margins. Probably, the bonding strength to enamel was sufficient to resist polymerization stresses, but these stresses exceeded the cohesive resistance of enamel, originating cracks in the mass of enamel. This phenomenon was also observed by Stavridakisand colleagues , in class I bulk-filled restoration. In Class V cavities enamel margins are beveled based on the notion that beveling decreases marginal leakage, increases adhesion, and improves esthetics. However, on the other hand it has been suggested that bonding to beveled margins did not produce a better marginal seal than the unbeveled margins but only improves esthetics .
In the current study a group of cavity preparations were prepared without an enamel margin beveling in anticipation of insignificant findings at least the same degree of microleakage as cavity preparations with an enamel margin beveling, accordingly so the elimination of enamel cavosurface beveling in Class V cavities could be realized, and this agree with Santiniand colleagues ,who compared microleakage in Class V cavities restored with micro hybrid composite using self-etch and total etch bond with 90° cavosurface margin and enamel bevel restored with micro hybrid composite and concluded that no significant difference in microleakage was found. Also according to Bagheri and Ghavamnasiri  who compared the marginal leakage of hybrid and microfilled composite resin in Class V restorations with and without an enamel bevel, no significant difference between the two types of composites and two types of enamel margins with respect to microleakage were noted. On the other hand, Owens et al.  found that a Class V restoration using either an incremental or single-step (bulk) insertion technique with a gingival bevel demonstrated greater microleakage than occlusal bevel.
It was realized that, flowable composites can be readily inserted into small cavities and are expected to adapt better to the internal cavity wall than conventional and bulk-fill posterior restorative composites, which are more viscous this can be explained by their lower stress due to low-elastic modulus, compared with the higher elastic modulus of conventional composites and their lower wettability ,. Orłowski et al.  agreed with our result who stated that statistically significant better marginal integrity of flowable tested materials, SDR, SonicFill, and Filtek bulk-fill compared to the composite TetricEvoCeram bulk-fill, may be due to their flow consistency during application. Moreover, Peutzfeldt and Asmussen showed and reported that the degree of fluidity when applying the composite material influences the marginal adaptation; increased fluidity of the composite makes it adhere better to the walls of the cavity.  On the other hand, Braga et al.  and Cadenaro et al.  concluded that flowable resin composites have shown shrinkage stress comparable to conventional resin composites, supporting the hypothesis that the use of flowable materials does not lead to marked stress reduction, and the risk of debonding at the adhesive interface as a result of polymerization contraction is similar for both types of materials. Also, Furness et al.  found no significant difference in proportion of gap-free interfaces between bulk and incremental composites. Differences between specific materials also were generally not significant. The proportion of gap-free interfaces tended to decrease with increasing depth in the preparation, but was largely unaffected by composite type or placement technique. The results of our study also stated that there was no significantly difference between bulk-fill posterior composite and nanohybrid composite in relation to marginal microleakage. This agree with Al-Harbi et al.  who analyze the cervical marginal integrity of bulk-fill versus incremental and open-sandwich class II resin composite restorations after thermo mechanical cycling and reported that bulk-fill composites provide similar marginal performance to open-sandwich and incremental composites.
Moreover, Agarwal et al.  agree with our result who evaluated the cervical marginal and internal adaptation of posterior bulk-fill resin composites of different viscosities, before and after thermo cycling and found that no significant differences in marginal and internal adaptation at the cervical tooth restoration interface in cavities restored using either the bulk-fill or the incremental fill technique. They reported that viscosity of the bulk-fill restorative material influenced the proportion of gap-free marginal interface and the internal adaptation in dentin. On contrary, Kreitzer et al.  who evaluate bulk-fill composites in Class II restorations, it found that there was a significant difference between using bulk-filled composites as compared to using a nonflowablenano composite. It was also evident that using a bulk-filling technique provides better marginal adaptation on the gingival floor and proximal wall of the restorations.
Meanwhile, in the present study, the data collected lead to the conclusion that, bulk-fill flowable composite resins, showed a lesser marginal microleakage on dentin and enamel with and without beveling compared with nanohybrid high-viscosity composite resins and bulk-fill nonflowable composite and this may be attributed to the degree of fluidity when applying the composite material influences the marginal adaptation; increased fluidity of the composite makes it adhere better to the walls of the cavity. Also, this can be explained by lower stress of bulk-fill flowable due to low-elastic modulus, compared with the higher elastic modulus of conventional composites and bulk-fill nonflowable and lower wettability.
The results of the study indicate that there was a significant minimum microleakage at the enamel margins compared to dentin margins of all tested groups. This is because of the efficient bonding of composite resin with the enamel and adhesion to dentin is less predictable and more variable dependent than bonding to enamel. Also, good results were obtained with flowable composite and found that complete elimination of microleakage at the dentinal margin is not achieved with flowable composite.
| Conclusion|| |
- Gingival margins exhibit significantly higher microleakage values compared to occlusal margins
- Beveling cavosurface margins did not affect microleakage values neither negatively nor positively compared to butt-joint cavosurface margins
- Type of tested composite materials was an effective variable on the recorded microleakage values. Statistically significant different was recorded in Filtek flowable bulk-fill composite with lowest values of dye penetration compared to the remaining tested composite materials.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]