|Year : 2016 | Volume
| Issue : 1 | Page : 34-39
Clinical evaluation of class II composite: Resin restorations placed by two different bulk-fill techniques
Rahaf M Alkurdi, Souad A Abboud
Department of Endodontic and Conservative, University of Damascus, Damascus, Syria
|Date of Web Publication||6-May-2016|
Dr. Rahaf M Alkurdi
Andalus Street, Aleppo
Source of Support: None, Conflict of Interest: None
Clinical trial registration NCT02185573
Objective: The purpose of this study was to compare the clinical performance of class II composite resin restorations placed by two different bulk-fill techniques according to the United States Public Health Service (USPHS) criteria. Materials and Methods: Sixty class II restorations were placed in 60 patients in the age range of 20-50 years. The patients were divided into three groups according to the technique of the restoration were applied. Group 1: Tetric Evo Ceram (Ivoclar Vivadent) was placed in 2 mm increments. Group 2: Tertic N Ceram Bulk Fill (Ivoclar Vivadent) was placed in single increment. Group 3: Sonic Fill (Kerr, Kavo) was placed in single increment by sonic vibration. The restorations were evaluated using modified USPHS criteria at baseline and then after 3 months, 6 months, 9 months, and 12 months. Results: After 12 months, 58 Class II restorations could be observed. Two cases were dropped out. All the restorations of the three groups showed acceptable clinical performance according to the modified USPHS criteria, and statistically there were no significant differences between the two bulk-fill techniques. Conclusion: Both the bulk-fill techniques performed satisfactorily over the 12-month observation period. Due to the low viscosity of Sonic Fill, it may preponderance Tertic N Ceram Bulk Fill in the regard to depth of cure and marginal integrity and marginal discoloration.
Keywords: Bulk fill, clinical, composite resin, sonic, United States Public Health Service (USPHS)
|How to cite this article:|
Alkurdi RM, Abboud SA. Clinical evaluation of class II composite: Resin restorations placed by two different bulk-fill techniques. J Orofac Sci 2016;8:34-9
|How to cite this URL:|
Alkurdi RM, Abboud SA. Clinical evaluation of class II composite: Resin restorations placed by two different bulk-fill techniques. J Orofac Sci [serial online] 2016 [cited 2019 Oct 23];8:34-9. Available from: http://www.jofs.in/text.asp?2016/8/1/34/181926
| Introduction|| |
A great deal of discussion has taken place around the polymerization shrinkage of composite resin restoratives in dental applications.  It should be distinguished between polymerization shrinkage and polymerization stress. Visible light cured composite resin contain multifunctional and reactive molecules called monomers. When exposed to light, these monomers link together to create large molecules called polymers, which, in turn, link together to form a continuous network. The polymerization process requires that monomers physically move closer together to achieve the chemically reactive of free radicals. This process results in a net loss of volume referred to as polymerization shrinkage if not restricted by bonding to a cavity. When this shrinkage process is restricted stress builds up in the material. 
Shrinkage stress exert forces on bonded interfaces to which the composite resin is attached. This transfer of polymerization stress to tooth structure is the cause of many clinical problems as follows: Enamel fracture, cuspal movement, and cracked cusps. In less well bonded restorations, polymerization stress has the potential to initiate failure of the composite-tooth interface (adhesive failure). The resulting gap between the composite and cavity walls may produce postoperative sensitivity, microleakage, and/or secondary caries.  Therefore, if the magnitude of polymerization stress due to shrinkage can be reduced, the resulting effect on clinical success of composite resin systems may be improved.
Several factors have been identified as influencing the shrinkage stress of a restoration: The size and geometry of the restoration configuration factor [(C-factor), depth, and diameter], materials used, and the curing protocol.  Extensive efforts have also been made to develop low shrinkage composite resins not only by changing filler amount, size, and shape, monomer structure or chemistry, and by modifying the polymerization reaction. 
Several restorative techniques have also been used to minimize the development of polymerization shrinkage and stress, such as multiple increment techniques, the use of ceramic inserts, and the replacement of the dentin with a glass ionomer cement in the sandwich technique. 
Incremental filling techniques have been proposed as a means to reduce shrinkage stress of composite restorations due to the reduction of C factor. There has been disagreement among authors recently on this issue. Despite differing conclusions, incremental filling techniques are generally recommended and dentists may choose to restore composite resin restorations in this manner on the basis of additional factors such as acceptable depth of cure, proper adaptation, and adequate bond formation. 
The conventional increment technique can be very time-consuming and complicated when it is used to fill large and voluminous cavities in posterior teeth. As a result, many dentists eagerly anticipated the arrival of an alternative to this highly technique sensitive multiple layering technique. The bulk-fill composite resins have been developed in response to this growing demand for more efficiency. Bulk-fill materials can be placed in increments of 4-5 mm thickness.  Increasing the depth of cure can be done by enhanced translucency of the composite resin which cause increased depth of cure per layer, optimization of the photo-initiator system of the light-curing composite can cause shorter curing times and increased depth of cure, the use of low-shrinkage composite resins with minimal stress build-up can help in apply thicker layers, high-performance, also the use of low viscosity composite resin can help in good adaption with the internal wall of the cavity. 
The aim of this clinical study was to compare the efficiency of two different bulk-fill techniques (Tetric N Ceram Bulk Fill, Sonic Fill) used to restore class II cavities, and comparing them intraindividually with conventionally layered technique (Tetric Evo Ceram). The null hypothesis tested was that there would be no difference between the different techniques under investigation.
| Materials and Methods|| |
The original study sample included 60 patients (20 patients for each group). Each patient fulfilled the following criteria:
- Inclusion criteria were as follows: 1. good oral hygiene, 2. permanent premolars and molars requiring class II for treating primary carious lesions, and 3. caries degree D3-D4 according to DIAGNOdent.
- Exclusion criteria were as follows: 1. unerupted tooth or partially erupted tooth, 2. poor hygiene, 3. heavy bruxism habits, 4. periodontal problems, 5 pathologic pulpal diagnosis with pain (nonvital), 6. fractured or visibly cracked teeth.
Sample size considerations
The sample size was calculated on the basis of the previous sample size calculations performed in similarly designed studies of posterior restoration evaluations. Based on previous investigations, a power analysis determined that for an alpha value 5% and a power of 80%, a sample size of 16 per group would be required. Accordingly, assignment continued until 20 restorations were enrolled in the three groups of this study to compensate for any unexpected dropouts. It has been possible to determine significant differences between material groups in similarly designed intraindividual comparison evaluations in previous studies. 
The materials used in this study are listed in [Table 1]. Caries degree were measured by DIAGNOdent device. Existing caries were removed under constant water cooling, no bevel were prepared, and the operative field was carefully isolated with rubber dam. None of the cavities received Ca(OH) 2 or other base materials. In all cavities etch (N Etch, Ivoclar Vivadent) was applied for 15 s then was rinsed after that bond (N Bond, Ivoclar Vivadent) was applied and cured for 20 s. Ring matrix (Palodent, Dentsply) was used. Polymerization was performed with an LED unit Light Hemao (Hemao Midical Instrument Co. Ltd, China), and output was measured using a curing radiometer.
Group 1: Tetric Evo Ceram (Ivoclar, Vivadent) was placed in 2 mm increments, and each increment was light-cured for 20 s.
Group 2: Tertic N Ceram Bulk Fill (Ivoclar Vivadent) was placed in single increment, and was light-cured for 40 s.
Group 3: Sonic Fill (Kerr, Kavo) was placed in single increment by sonic vibration and was light-cured for 40 s.
The occlusion and articulation were checked and adjusted, and then the composite restorations were finished with fine-grit diamond instruments and were polished with polishing disks, brushes, and finishing strips (OptiDisc, Kerr).
Modified United States Public Health Service (USPHS) criteria ,,,,, were used to evaluate postoperative sensitive, marginal integrity, marginal discoloration, surface texture, color stability, wear, fracture, and secondary caries at baseline, then after 3 months, 6 months, 9 months, and 12 months. The baseline rating was carried out immediately after the finishing and polishing procedures. Statistical analysis was carried out with Statistical Package for the Social Sciences (SPSS) 16.0 (SPSS-Inc., Chicago, IL). Kruskal-Wallis test was used to explore significant differences between groups and Wilcoxon signed ranks test was used to explore significant differences between the results at baseline and after 12 months.
| Results|| |
Sixty restorations were at baseline, only 58 restorations were evaluated after 12 months. Two restorations (one from group 1 and the other from group 2) could not be observed because the patients were moved away and could not come for final recalls. All restorations were judged as alpha at the baseline evaluation. The numbers of restorations judged as bravo rating at the recall visit were seven for marginal discoloration, six for surfaces texture, eight for wear of restoration, seven for marginal integrity, twenty-three for postoperative sensitivity, seven for color stability. The numbers of restorations judged as Charlie rating at the recall visit were three for marginal discoloration and two for postoperative sensitivity. [Table 2] summarizes the results of clinical evaluation of the restoration at baseline and after 12 months. The overall success rate was 91.3%. Five restorations failed, four in group 2 and one in group 1 (Tertic N Ceram Bulk Fill: 2 marginal discoloration, 2 persisting hypersensitivity; Tertic Evo Ceram: 1 marginal discoloration), resulting in a 100% success rate for Sonic Fill, 94.7% success rate for Tertic Evo Ceram, and 78.9% success rate for Tertic N Ceram Bulk Fill (P > 0.05).
|Table 2: The results of clinical evaluation of the restorations at baseline and after 12 months|
Click here to view
| Discussion|| |
Composite resin bulk-fill technology has undergone major developments over the last decade. However, these developments have been so rapid that long-term clinical data on specific products are rarely available. Laboratory tests might provide useful information to the potential performance of a filling material and its handling, but such tests cannot adequately evaluate the clinical performance of a material or clinical handling characteristics. Besides, in vitro studies cannot answer questions about in vivo longevity of these tooth-colored restorations.  Clinical studies of bulk-fill materials are lacking and there is insistent need for long-term studies to evaluate the clinical performance of these newly developed materials.
The results of this study supported the null hypothesis that there are no significant differences in clinical performance between the two bulk-fill techniques, also between the bulk-fill technique and multi-layering technique.
According to that, it is possible to use clinically thicker increments as determined in other similar studies,  and that can overcome the problems associated with multi-layering technique such as incorporating air, contaminated between the layers, waste time and efforts, also some authors indicated that incremental layering induced high stresses at the interfacial margins. ,
Bulk-fill composites do not constitute a uniform class of materials. Considerable differences exist between the individual products with regard to the composition and size of the filler particles, they also differ from each other in the way of clinical application and the way in which the fillings are built up. 
Bulk-fill composite resins are generally more translucent than multi-layer composite resins, shade and translucency level influence the depth of cure of composites,  and this provides a partial explanation for why thick increments of bulk-fill composite resins cure just as effectively as thin 2-mm layers of conventional composite resins. llie et al. found that high translucency reduces light scattering and improves light penetration that enhances the light polymerization of thick restoration layers.  In addition to that Tetric N Ceram Bulk Fill features an photo-initiator called Ivocerin that is highly reactive to incoming photons and therefore enables the restorative material to cure to a depth of 4 mm,  whereas Sonic Fill had enhanced the depth of cure by increasing the levels of photo-initiators in the composite material that allows to achieve a full 5-mm depth of cure. 
The satisfactory clinical results that obtained in this study for Tetric N-Ceram Bulk Fill and Sonic Fill in the regard to the fracture and recurrent caries (100% alpha) may be because the improvements in the structure of the materials which have done to minimize polymerization shrinkage and shrinkage stress which is particularly important in a material that is applied in increments up to 4-5 mm. , Tetric N-Ceram Bulk Fill contains a polymer filler that is considered as shrinkage stress reliever with a low modulus of elasticity attenuating the forces generated during shrinkage.  Whereas Sonic Fill consists of low shrinkage resin, in addition sonic activation of the composite resin dramatically lowers the viscosity during placement providing superior adaptation to the cavity walls. 
In this study, although there were no statistically significant differences in clinical efficacy between the two different bulk-fill techniques, yet the scores recorded for Sonic Fill restorations were better than that recorded for Tetric N Ceram Bulk Fill.
According to the results of this study, Tetric N Ceram Bulk Fill exhibited 82% alpha scores after 12 months with regard to wear and 88% alpha scores with regard to surface texture (roughness), whereas Sonic Fill exhibited 95% alpha scores with regard to both wear and surface texture. That may be because Sonic Fill has high filler load of the material (83.5% in weigh) more than Tetric N Ceram Bulk Fill (75% in weigh) which give the material this good properties. ,
According to the results of this study, three composite resins demonstrated similar results with regard to color stability. And that may be because the three materials have relatively small filler particles that provide an advantage in terms of color properties,  also they have a Urethane Dimethacrylate (UDMA) polymer matrix, which provides better resistance to color change as Bayne et al. found in their study. 
Marginal discoloration usually results from defects present between tooth-colored restorations and cavity margins.  According to the results of this study, Tetric N Ceram Bulk Fill exhibited 76% alpha scores after 12 months with regard to marginal discoloration and integrity, whereas Sonic Fill recorded 90-95% alpha scores in the same regard. That may be because sonic vibration lowers the viscosity of the Sonic Fill composite resin, allowing the material to flow and possess a good wetting ability, and that favors their adaptation to the cavity walls, which results in better marginal properties more than Tetric N Ceram Bulk Fill.
In the present 1-year clinical study, postoperative sensitivity was recorded only at baseline (56 % alpha score for the three groups) and disappeared after 12 months. Postoperative sensitive seemed to be a problem related to resin composite restorations. Many studies  have indicated that up to 30% of the study populations have reported postoperative sensitivity following the placement of a posterior resin restoration. In the current study, postoperative sensitivity was seen in premolar teeth more than that in molar teeth, and more in Tetric N Ceram Bulk Fill group than in Sonic Fill group. Two failed class II premolar restorations in Tetric N Ceram Bulk Fill group were recording. The patients suffered from severe postoperative sensitivity to temperature changes and pressure during the first 3 weeks after the treatment and they needed pulp treatment may be due to lack of monomer conversion in deep cavities. Especially in premolar teeth that usually have less thickness of dentine above pulp chamber may cause leakage of monomer to the pulp that results in irreversible irritation.
| Conclusion|| |
- Both of the bulk fill techniques showed acceptable clinical results and were similar to the conventional layering technique over the 12-month evaluation periods.
- According to the results of this present study, bulk-fill restorations can overcome the difficulties with multi-layer technique, saving time and efforts with satisfactory clinical outcome.
- Due to the low viscosity of Sonic Fill, it preponderance Tetric N Ceram Bulk Fill in the regard to depth of cure and marginal integrity, as sonic energy is applied through the handpiece increasing the flowability of the Sonic Fill enabling quick placement and precise adaptation to the cavity walls.
Financial support and sponsorship
Syrian Arab Republic Government, University of Damascus.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2]
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