Introduction

Resin composites were first used as aesthetically pleasing materials for front dental restorations, and their use for posterior teeth followed swiftly. Composite restorations still have several shortcomings, even with the advancement of adhesive techniques and the development of composite resins. One of the main problems is polymerization shrinkage, which may cause debonding between the resin composite and tooth structure. This results in minor discoloration and secondary caries that might shorten the restoration's lifespan. Polymerization stress is also generated as a result of this phenomenon [1].

Additionally, these forces can produce cusp displacement and microfractures by transferring into the tooth structure. The chemical formulation of some materials is one of the many attempts that have been undertaken to minimize the volumetric shrinkage of composite resins [2]. One of the most common issues with resin composites is microleakage. A marginal gap may form at the tooth restoration interface when there is a lack of sealing. Microleakage may develop at the tooth restoration interface if the stresses resulting from polymerization surpass the bond strength. These stresses are produced inside the restoration and at its borders [3].

The volumetric polymerization shrinkage, the resin composite's elastic modulus and flow, its adhesion to the cavity walls, and the restoration's configuration factor are some of the factors that affect the creation of stress. The ratio of the bonded cavities to the unbonded surface area is known as the cavity configuration factor or C-factor. A rise in the C-factor is linked to a gradual deterioration of the bond strength. As a result, the strength of the adhesive's interaction with the tooth structure should balance the polymerization stresses generated in the resin composite and at the interface. In the absence of this, gap development and marginal integrity may suffer. The viscoelastic characteristics of the material have a significant influence on the contraction stresses. These pressures could be transmitted to the restoration's margins in a clinical setting, lowering marginal quality. Problems including leaking, recurring cavities, and pulpal irritation might arise when marginal quality is insufficient [4].

Incremental filling procedures are often chosen over bulk filling methods to provide a successful marginal seal and prevent the clinical effects of polymerization shrinkage. Although the progressive method may be necessary for adequate light penetration, there are downsides, including the possibility of trapping voids within layers and the amount of time required to install the repair. Because fewer clinical stages are involved, the bulk application approach is easier to use and expedites the process. Thirteen Significant advancements in composite technology are rare, despite advancements in adhesive methods [5].

A line of goods known as "bulk fill composites" has just been released within this framework. Because of their strong responsiveness to light curing and decreased polymerization stress, these materials may be inserted in a 4 mm bulk placement. It ought to be coated with a traditional composite layer, subject to the material being used [5]. The current study aims to ascertain how much modern bulk-fill composites have changed from traditional composites in marginal adaption in various cavity designs. The assumption that there wouldn't be any variations in marginal adaption in cavities repaired using various composite materials was the null hypothesis analyzed.

Materials and Methods

Using the PubMed, ScienceDirect, and Medline, databases, a comprehensive evaluation of the literature spanning 2010 to 2023 was conducted. The terms that were utilized were " sealing ability, bulk-fill, conventional composites, and Randomized control trials." To illustrate the procedure for choosing the articles to be searched for, a PRISMA schematic was employed (Figure 1).

Inclusion criteria

• Expert opinions, narrative reviews, systematic reviews, or meta-analyses
• Published within the last decade to 2010.
• English language of publication
• In vivo (humans)

Exclusion criteria

• Randomized control studies and Case-controls
• Outside the allotted period
• Not being in the English Language
• In vitro

Assessment of the risk of bias

The quality of the studies was evaluated using the Cochrane risk of bias assessment technique (Table 1).

Table 1. Summary of Cochrane Risk of Bias Assessment

Results and Discussion

Table 2 shows the summary of the included eleven studies, where the objectives, materials and findings have been listed. In class II cavities in maxillary premolars, Shadman et al.'s study [3] sought to evaluate and contrast the marginal dentinal microleakage of bulk fill (in two viscosities) and conventional composites. For this in vitro study, forty-two class II cavities extending 1 mm below the cementoenamel junction were made on both the distal and mesial surfaces of 21 maxillary premolars. Grandio composite was used to reconstruct the cavities in 2-mm increments, in contrast, 4-mm increments of X-tra fil and X-tra base were employed. After a 24-hour storage period at 37 °C and 100% humidity, they were sectioned, thermocycled (500 cycles, 5–55oC), maintained in basic fuchsine, and inspected under a stereomicroscope (×40). Between the groups, there were no significantly different variations (P=0.47) regarding marginal microleakage. In this regard, there was no discernible statistically significant change between the bulk and gradual application approaches (P=0.23).

The study's objective is to compare the marginal adaption of Sonic fill to Ceram X traditional composite resin composites, considering the impact of varying cavity configurations (C-factor). Ninety newly removed non-caries human premolar teeth were utilized, and they were randomly split into two equal significant groups (45 each) based on the tested materials: Sonicfill and Ceram X resin composites. Each group was then subdivided into three equal subgroups of fifteen based on the cavity configuration: class II cavities, class V cavities, and flat tooth surfaces. Each subgroup was subdivided into three five-month storage time intervals: one, three, and six months. The study's findings showed that Sonic-fill had less microleakage than Ceram X. Microleakage is not eliminated by C-factors for both bulk-fill resin materials. The smooth tooth surface in both class II and class V differed significantly. At six months of storage, Sonicfill and Ceram X had significant leakage scores Mohamed et al. [6].

The goal of the study conducted by Mosharrafian et al. [7] was to examine and contrast the microleakage of two bulk fills and one standard composite in class II restorations of primary posterior teeth. Sixty primary mandibular teeth that were second molars were used in this in vitro experiment and were split into three groups at random. Teeth with typical class II cavities were prepared, and the restorations used in groups 1 and 2 were Z250 conventional composite, SonicFill bulk fill composite, and 3M bulk fill composite. The mean (± standard deviation) dye depth of penetration in the gingival margins for 3M bulk fill, SonicFill, and Z250 conventional composite were 543±523μm, 343±290μm, and 597±590μm, in that order. In the occlusal margins, these values were 214±93μm, 302±127μm, and 199±145μm, in that order. Occlusal and gingival microleakage did not vary substantially among the three groups (P>0.05); however, in all three groups, gingival margins exhibited considerably more microleakage than occlusal margins (P<0.05).

The present experiment carried out by GARCÍA et al. [8] examined marginal microleakages of Class II cavities that were repaired using FiltekTM Bulk Fill, a bulk-fill resin, vs FiltekTM Supreme XTE, a traditional composite resin. Forty removed human teeth had two standardized Class II cavities made in them. For twenty molars (groups 1 and 2), the gingival border was positioned above the cementoenamel junction; for the other twenty (groups 3 and 4) (n = 20), it was positioned apically. When comparing the dentin margins to the gingival margins seen in enamel, there was a significant decrease in microleakage (p<0.01). There was no apparent distinction among either groups 1 and 2 (p=0.86) or 3 and 4 (p=0.26). Gingival microleakage in bulk-fill resins is comparable to that in traditional composites.

The current research done by Aljamhan et al. [9] set out to evaluate the effectiveness of various dental RBCs and techniques for class II cavity sealing of the deep dentin edge. Box cavities (class-II) were made on the distal and mesial surfaces of extracted premolar teeth, with the gingival margin 1 mm apical to the cementoenamel junction. Teeth with prepared class II cavities were randomly assigned to four study groups depending on the kind of restorative materials used (conventional RBC lined with flowable RBC, bulk-fill RBC, conventional RBC lined with resin-modified glass-ionomer-cement (GIC) as open sandwich technique, and conventional RBC). Each group was then separated into two subgroups: one called self-etch, which employed a self-etch adhesive method, and the other called total-etch, which used a separate etching phase before applying the bonding agent (n = 10). Group 4 (GIC) had the lowest dye penetration values, while group 2b—bulk-fill employing the self-etch adhesive system—followed with the highest values. The group Bulk-fill using the total-etch adhesive system (2a) reported the maximum dye penetration, followed by the group Conventional RBC using the total-etch adhesive system. Compared to the self-etch adhesive system (1a), the total-etch adhesive system exhibited much higher micro-leakage (p = 0.026).

The purpose of the Tavangar et al. [10] study was to compare microleakage in Class II cavities between bulk-fill composites (flowable, packable) and conventional light-cured composites. Sixty human removed premolars were used in this in vitro experimental investigation. We created typical Class II cavities in the teeth, measuring 1.5 mm in axial depth, 4 mm in height, and 3 mm in buccolingual length. Based on the kind of composite, the teeth were randomly divided into three groups: packable bulk-fill (x-tra fill packable; VOCO Company), flowable bulk-fill (x-tra base; VOCO Company), and conventional composite (Grandio; VOCO Company) comprised group I. According to the data, the bulk-fill packable and conventional composites' enamel and dentinal margins did not differ statistically substantially. (P= 0.06). Dentinal margins demonstrated more dye penetration to the axial surface's enamel edge in the bulk-fill flowable group (P<0.05). P<0.05 showed that there was no discernible variation in the marginal microleakage of enamel and dentin between the three groups.

de Albuquerque et al. [11] study's goal was to compare the volumetric shrinkage of bulk-fill vs standard composite resin, as well as the Class II mesial-occlusal-distal (MOD) restorations' marginal adaptation both before and after thermomechanical loading. A total of twenty-four human molars that were removed, undamaged, noncarious, and not repaired and kept in a 0.1% thymol solution were chosen. To fill in the teeth, the following was done: Group C: progressively filled with Esthet-X HD; Group B: bulk-fill with SureFil SDR flow as a basis (first increment, 4 mm) and covered with the conventional nanohybrid composite Esthet-X HD (second increment, 2 mm). Cluster A: utilize SureFil SDR flow for bulk filling (first increment: 4 mm; second increment: 2 mm). After light curing, the evaluated composites were put into a semi-spherical mold and placed within an AccuVol device to assess volumetric polymerization shrinkage. Groups A and B showed better marginal adaptation in the cervical dentin than Group C, both before and after loading (p< 0.05). Group B outperformed Group C in marginal adaptation to cervical enamel, whereas Group A's findings fell somewhere in between. Moreover, shrinkage was higher with bulk-fill flow than with Esthet-X HD.

The research conducted by Abdelrahman  [12] sought to assess the bulk-fill flowable composite resins' shear bond strength and microleakage using self-adhesive resins. For this investigation, forty removed human teeth that were not carious were chosen. For the microleakage test, twenty Class V cavities were built on the labial surface. Ten teeth were treated: Group II was given a bulk fill flowable composite treatment together with a one-step self-etch adhesive system, whereas Group I was given a self-adhesive flowable composite treatment.he universal testing equipment was used to assess the shear bond strength. In both of the restorative materials under investigation, the mean microleakage score of the cervical margins was non-significantly greater than that of the occlusal margins. Compared to Vertise flow, Filtek flowable bulk fill composite showed a significantly higher mean microleakage score at the cervical and occlusal margins.

The purpose of the research done by Assiri et al. [13] was to assess and contrast the marginal adaptation of multilayer Filtek Z250 resin composite restorations, SonicFill bulk-fill resin composite, and class II (MOD) bulk-fill Tetric EvoCeram restorations. Thirty MOD cavities were made in human molar teeth that were removed. The cavities were separated into ten groups using three different restorative materials (Filtek Z250, Tetric Evoceram Bulk fill, and Sonic fill). A scanning electron microscope was used to evaluate marginal adaption. Comparing the typical bulk fill restorative material (Filtek Z250) with the investigated bulk fill materials (Tetric Evoceram Bulk fill and Sonic Fill), there were no significant differences (P<0.05).

In this investigation, fifteen human third molars that had been removed whole were employed. Based on the composites used, cavities were randomly split into three groups: Filtek Silorane LS-silorane, Filtek Ultimate-nanocomposite, and SonicFill-bulk-fill composite. After that, all specimens underwent heat cycles and were submerged in saline for ten mounds. Samples were aged and then submerged in 2% methylene blue. Once ready, they were immediately coated in gold and subjected to a SEM analysis to determine the marginal seal. Marginal fissures are much more prevalent now (p = 0.001). The microleakage research revealed a substantial influence of both substance (p < 0.000) and time (p < 0.000) [14].

Table 2. Key findings of included studies