|Year : 2022 | Volume
| Issue : 1 | Page : 67-73
A comparative evaluation of gingival microleakage and internal voids in Class II composite restoration with two different lining techniques: An in vitro study
Rachana Shishodia1, Virinder Goyal2, Almas Shaikh3, Aushili Mahule4, Jay Dondani3
1 Department of Paediatric Dentistry, Surendra Dental College and Research Institute, Sri Ganganagar, Rajasthan, India
2 Department of Paediatric Dentistry, Guru Nanak Dev Dental College, Sunam, Punjab, India
3 Department of Prosthodontics, Government Dental College, Mumbai, Maharashtra, India
4 Department of Prosthodontics, Crown Bridge and Oral Implantology, Swargiya Dadasaheb Kalmegh Smruti Dental College and Hospital, Nagpur, Maharashtra, India
|Date of Submission||24-Jun-2021|
|Date of Decision||27-Jan-2022|
|Date of Acceptance||31-Jan-2022|
|Date of Web Publication||13-Apr-2022|
Dr. Aushili Mahule
Department of Prosthodontics, Crown Bridge and Oral Implantology, Swargiya Dadasaheb Kalmegh Smruti Dental College and Hospital, Nagpur, Maharashtra
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Aim: The aim of this study was to evaluate the gingival microleakage and internal voids in Class II composite restoration restored with precure and co-cure lining techniques using stereomicroscopic method. Materials and Methods: Forty-five freshly extracted permanent multirooted human molar teeth were collected and used in the study. After surface debridement and scaling of all teeth, standard Class II mesio-occlusal cavities were prepared. Forty-five samples were randomly divided into three experimental groups (n = 15), and filled according to manufacturer's instructions. Group I was precure group, Group II was co-cure group, and Group III was only bulk fill. The finishing and polishing of the restorations was done after 24 h. Then, all the specimens were subjected to thermocycling for 500 cycles. The gingival microleakage and internal voids of all the groups were evaluated using dye penetration method. Samples were then sectioned and examined under the stereomicroscope at ×40. Readings obtained were subjected to statistical analysis using SPSS ver 20.0 (IBM Corp, ARMONK USA) and Chi-square test. Results: The statistical analysis revealed that extent of microleakage was maximum in Group II (co-cure), followed by Group III (only bulk fill) and Group I (precure). The gingival voids were maximum in Group III (only bulk fill), minimum in Group II (co-cure), and least in Group I (precure). The cervical voids were maximum in Group II (co-cure) and Group III (only bulk fill), followed by Group I (precure). The occlusal voids were maximum in Group II (co-cure) and similar in Group I (precure) and Group III (only bulk fill). Conclusion: The precure lining technique was better than co-cure lining technique in terms of both microleakage and internal voids.
Keywords: Composite resin, microleakage, polymerization shrinkage, voids
|How to cite this article:|
Shishodia R, Goyal V, Shaikh A, Mahule A, Dondani J. A comparative evaluation of gingival microleakage and internal voids in Class II composite restoration with two different lining techniques: An in vitro study. J Indian Soc Pedod Prev Dent 2022;40:67-73
|How to cite this URL:|
Shishodia R, Goyal V, Shaikh A, Mahule A, Dondani J. A comparative evaluation of gingival microleakage and internal voids in Class II composite restoration with two different lining techniques: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2022 [cited 2022 Jun 25];40:67-73. Available from: https://www.jisppd.com/text.asp?2022/40/1/67/343011
| Introduction|| |
Unabating demand for the esthetic restorations both by the clinicians and the patients has led to an increased use of composite resin material. The material presents advantages from aspect of adhesive resin technology as well as of esthetic dentistry., However, despite several improvements in the technology of composite resin and their adhesive systems, polymerization shrinkage till date remains a major problem. Polymerization shrinkage pulls the restorative material away from the cavity walls, resulting in rupture of the adhesion and the formation of marginal gap which results in microleakage. On the other hand, internal voids can appear as a translucent area on radiograph and may be misinterpreted as secondary caries. The internal voids at the margin of the restoration may lead to gross microleakage and discoloration.
Microleakage is defined as passage between the cavity wall and restorative material created because of the shrinkage of resin during polymerization or poor adhesion of resin material between the dentin and composite material. The microleakage can further lead to the entry of bacterial by-products from saliva which can cause secondary caries, postoperative sensitivity, and development of pulpal and periapical pathology. Therefore, the adequacy and durability of sealing the restorative material against the tooth structure is a major consideration in the longevity of the restoration.
To avoid the aforementioned scenarios, various techniques and materials have been introduced with better mechanical properties and marginal sealing ability. One such innovation was the introduction of packable composite which utilizes increased filler or matrix phase to increase viscosity for better condensation and thus decrease polymerization shrinkage. Further, to make composite time efficient, bulk-fill composites were discovered. The rationale of the bulk-fill resins is to reduce clinical steps by filling the cavity in a “single” increment, leading to reduced porosity and a uniform consistency for the restoration, thus reducing the clinical time taken as well as cost factor for the patient than traditional composite., However, the common problem encountered with bulk-fill materials is their adaptation to internal cavity walls and cavosurface margin. One of the most important aspects of resin composite restoration in Class II cavity in posterior teeth is the inadequate adaptation caused by the great dentin: enamel ratio in the cervical area. Bonding to dentin has always been poor as compared to enamel because of the morphological, histological, and compositional differences between the enamel and dentin. Hence, attempts were made to offset this problem by placing materials with low viscosity as cavity liner under these packable composites, which adapted to the cavity better, act as a flexible intermediate layer between restoration and substrate, and relieve stress associated with polymerization shrinkage and reduce the problem of microleakage and internal voids.
Various materials such as flowable composites, glass ionomer, or resin-modified glass ionomer under the composite restoration are being used as a liner. Because of their low filler loading, flowable composites exhibited a lower modulus of elasticity and more stress-buffering capacity than hybrid composite resins, and this leads to their better marginal seal and greater bond strength values than those of conventional materials. Flowable composites provided excellent handling characteristics and syringe delivery system in inaccessible areas and might reduce the effects of polymerization shrinkage through increased stress relaxation, thus reducing gingival microleakage and internal voids. This popularized the use of flowable composites, particularly in proximal boxes of Class II preparations.
To further address the polymerization shrinkage of composite resin, two techniques were introduced, namely precure and co-cure techniques. In precure technique, two different light-cured materials were not polymerized coincidently; they are cured individually after their respective placement. On the other hand, co-cure technique introduced by Jackson and Morgan in 2000, utilizes a thin layer of flowable composite that is applied to cavity floor, which is immediately followed by packable composite increment and light cured. Most of flowable composites are expelled while placing over line composite and its volume will be minimized. This technique offers the advantages of two different composites, including intimate adaptation of filling and handling properties.
As stated above, the microleakage and internal voids may have detrimental effects on the quality as well as the longevity of the composite resin materials; the present study was undertaken to evaluate the gingival microleakage and internal voids in Class II composite restoration restored with precure and co-cure lining techniques using stereomicroscopic method. The null hypothesis was that no difference would be formed in either of the groups.
| Materials and Methods|| |
Forty-five freshly extracted unrestored maxillary and mandibular permanent molar teeth, free of caries, cracks and enamel hypoplasia were collected and used in the present study. Surface debridement of all the teeth was done. Teeth were stored in 5.25% sodium hypochlorite for 2 h to remove periodontal ligament fibers. Ultrasonic scaling was performed and teeth were then stored in 0.5% thymol crystals in distilled water, till they were further needed for the study.
The standard Class II mesio-occlusal cavities was prepared using diamond burs with an ISO Size (BR-46, ISO 001/012) and ISO Size (SF-11, ISO 111/012FG). Dimensions of the prepared cavity were 2 mm wide buccolingually and 2 mm deep pulpally. Gingival seat of the proximal box was placed 2 mm above cementoenamel junction and 2 mm wide. All preparations were carried out with high-speed water-cooled air rotor. After cavity preparation was completed, division and restoration of samples was done. A total number of 45 samples were divided into three experimental groups (n = 15) using statistical software (G POWER 3.1), estimated by assessing the previous literature conducted in the area of research and keeping confidence of interval 95%. The sample size was calculated using the following assumption: effect size – 0.48%, power of the study – 80%, and alpha (α) error – 5%.
Following this, all the prepared cavity surfaces were dried with oil-free compressed air, etched with 37% phosphoric acid for 15 s, and then rinsed with water thoroughly for 40 s and dried. The bonding agent was applied for 5 s to the etched surface, and cured for 20 s by LED-curing light. The study samples were then restored according to manufacturer's instructions: Group I was precure group, Group II was co-cure group, and Group III was only bulk-fill composite. After samples were restored, they were immersed in distilled water at room temperature for 24 h. Finishing and polishing of all the restored teeth was done using finishing and polishing discs.
The specimens were then subjected to thermocycling for 500 cycles between 5°C ± 2°C and 55°C ± 2°C with a dwell time of 30 s in each bath that is in customized cold water bath and hot water bath and 20-s interval time between the baths to simulate oral condition to hot and cold. The study samples were carried in each water bath with the use of aluminum metal case that consisted of three slots, and the study samples of each group were placed in respective slots.
After the samples were subjected to thermocycling, the root apices of the study samples were sealed with the yellow sticky wax and then painted with two coats of nail varnish leaving 1 mm around the restoration margin. Then, the samples were soaked in 2% methylene blue dye for 24 h. This was followed by the nail varnish removal with the help of scalpel and BP blade no. 11. The samples were then sectioned mesiodistally into two halves in a vertical plane parallel to long axis of the tooth using diamond disc at slow speed. The sections were examined under a stereomicroscope at ×40 to evaluate the degree of dye penetration along with capturing of photographs using digital camera (10X Zoom, 18 MegaPixel) [Figure 1], [Figure 2], [Figure 3], [Figure 4]. Then, the photographs were transferred to laptop and further evaluation of apical dye penetration at the gingival margin was done using Adobe Photoshop CS5 software, 12.0 × 32 version (Adobe Inc, United States).
|Figure 1: Extent of gingival microleakage in respective three study groups: (a) Score 4 in one of the study samples in Group II; (b) Score 1 in one of the study samples in Group III; (c) Score 0 in one of the study samples in Group I|
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|Figure 2: Gingival voids in respective three study groups: (a) Score 1 in one of the study samples in Group III; (b and c) Score 0 in one of the study samples in Group II and Group I, respectively|
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|Figure 3: Cervical voids in respective three study groups: (a-c) Score 1 in one of the study samples in Group II, Group III, and Group I, respectively|
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|Figure 4: Occlusal voids in respective three study groups: (a-c) Score 1 in one of the study samples in Group II, Group III, and Group I, respectively|
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The apical dye microleakage at the gingival margin was assessed using a scoring criterion: degree 0: no dye penetration, degree 1: up to ½ the gingival seat, degree 2: >1/2 the gingival seat, degree 3: all along the gingival seat, and degree 4: degree 3 plus into the axial wall. The internal voids were evaluated at three predetermined sites: occlusal half, cervical half, and gingival interface. A score of zero was assigned when no voids were present and one when voids present. The data were subjected to statistical analysis using SPSS ver 20.0 (IBM Corp, ARMONK USA) and Chi-square test at significance level of 0.05.
| Results|| |
It was found that the intergroup comparison between all the experiment groups was significant for gingival microleakage and gingival voids whereas insignificant for cervical and occlusal voids. The study groups revealed that extent of microleakage was maximum in Group II (co-cure), followed by Group III (only bulk fill) and Group I (precure) [Table 1]. The gingival voids were maximum in Group III (only bulk fill), minimum in Group II (co-cure), and least in Group I (precure) [Table 2]. The cervical voids were maximum in Group II (co-cure) and Group III (only bulk fill) followed by Group I (precure) [Table 3]. The occlusal voids were maximum in Group II (co-cure) and similar in Group I (precure) and Group III (only bulk fill) [Table 4].
|Table 1: Intergroup comparison of scores for gingival microleakage of all the three study groups|
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|Table 2: Intergroup comparison of scores for gingival voids of all the three study groups|
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|Table 3: Intergroup comparison of scores for cervical voids of all the three study groups|
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|Table 4: Intergroup comparison of scores for occlusal voids of all the three study groups|
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| Discussion|| |
Marginal adaptation or integrity is one of the essential factors to see the clinical performance of any of the dental restorative materials, or the technique of its placement. The integrity is compromised, when microleakage occurs resulting from polymerization shrinkage. Polymerization shrinkage is the most common cause of failure of direct posterior composite restoration.
With advancement in dentin adhesives and the evolution of esthetic dentistry, composites have become more widely used as posterior restorations. However, despite having good physical properties, the main shortcomings of composite resin materials are polymerization stress., The resulting stresses have been associated with marginal deficiencies, enamel fractures, cuspal movement, and cracked cusps, which in turn may result in microleakage, postoperative sensitivity, and secondary caries. Besides microleakage, the other most important controversial topic related to composite is internal voids. The porosity of dental composite resins has been identified as a factor that may adversely affect critical properties of the final restoration, such as diametral tensile strength, abrasion resistance, water resorption, degree of cure, surface roughness, and color stability. In general, porosity creates bulk or surface geometrical discontinuities which increase fracture propagation and failure probability on loading.
The present study made the use of mesio-occlusal Class II cavities because restoring Class II cavities with composite resin has always remained point of debate. The restoration of the large Class II with resin-bonded composite materials is technique-sensitive procedure in term of time consumption, technique of placement, incremental curing, and the operator time required for separate etching, priming, and bonding techniques. The gingival seat of the prepared cavity was placed 2 mm above the CEJ to avoid discrepancy in terms of marginal microleakage with respect to structural difference between enamel and cementum.
Studies have shown that fifth-generation bonding agent exhibited less microleakage as compared to sixth- and seventh-generation adhesive systems; hence, fifth-generation adhesive was preferred to evaluate the microleakage of restorative materials in our study.,
The purpose of this study was to compare the effect of two different lining techniques in Class II composite restoration by evaluating the presence of internal voids and degree of microleakage. In the present study, the apical dye microleakage at the gingival margin was assessed using a scoring criterion. It was found that microleakage was least in the precure group, followed by the bulk-filled group, and it was maximum in the co-cure group. The results were significant between the precure versus co-cure groups and precure versus only bulk-filled groups, and there was no significant difference between the co-cure versus only bulk-filled groups.
The result obtained from this study was in accordance with the study conducted by Peris et al. and Simi and Suprabha who concluded that the placement of flowable composite liner beneath restoration resulted in significant reduction in microleakage. The use of a low-viscosity resin composite working as a “stress breaker” in compactable resin composite restorations is capable of reducing marginal microleakage. Flowable composite liner if cured serves as a well-adapted first increment, resists disturbance, and absorbs polymerization shrinkage of the overlying composite. In contrast with the present study, the studies conducted by Ziskind et al. and Boruziniat et al. stated that the placement of flowable composite as intermediate material does not reduce microleakage. They discussed that the effect of the restorative material at the cervical margin appears to be dominant factor in gap formation and subsequent microleakage at the floor of the box in Class II restorations because thick lining of packable restorations with composite resin may impair the marginal sealing, especially after thermocycling.
In the present study, the co-cure group with the application of flowable composite liner showed no significant reduction in microleakage. Although it was thought that co-curing the flowable liner and the overlying composite together would help the uncured liner to penetrate better and improve sealing at the margin due to hydraulic pressure of overlying heavier viscosity composite. Contrasting the above finding, our study showed more leakage with co-cure as compared to the precure liner group. This may be attributed to the fact that polymerization shrinkage of overlying packable composite would have created contraction forces that may have disrupted the bond of uncured flowable composite liner from the cavity walls. The result for precure material and co-cure material was in contrast with the study performed by Reddy et al.
The present study has shown maximum gingival voids in the bulk-fill material, followed by co-cure, and least in precure material. The cervical voids were maximum in the co-cure group and only bulk-filled group followed by precure group. The occlusal voids were maximum in the co-cure group and similar in the precure and only bulk-filled groups. The result was in accordance with the study conducted by Sood et al. and Reddy et al. who have stated that curing the flowable liner before packable restorative material leads to lesser number of voids and that too mainly gingival and cervical voids, this is due to low modulus of elasticity, increased wetting of flowable composite and thereby enhanced marginal adaptation. Thus, the present study concluded that application of flowable composite as liner by precuring lining technique showed lesser number of gingival voids. The results obtained for the precure and co-cure groups were in contrast with the study from Korkmaz et al. who concluded that there was no difference in gingival voids and occlusal voids with and without application of flowable composite liner under composite restoration.
The result for the only bulk-filled group showing the maximum number of gingival and cervical voids was in accordance with the study conducted by Samet et al., who concluded that increased stiffness of the packable resin composite, provided sufficient resistance to the condensation forces. Thus, adapting these stiffer materials to internal cavity walls and proximal area became difficult resulting in an increase number of voids and gaps. Hence, to compensate these defects, the use of cavity liner is recommended. However, the only bulk-filled material showed lesser number of occlusal voids than the co-cure material. This was in accordance with the study conducted by Van Ende et al. and may be attributed to the fact that the incremental placement of packable composite is time-consuming and tedious procedure, especially in posterior teeth. The increments may also increase the potential of occlusal voids to form between two incremental layers of composite, thus using bulk fill in single increment can compensate for occlusal voids.
The present study had some limitations which include a smaller sample size. Although the study was conducted on sound natural teeth, it is hard to standardize the invisible microcracks, age changes, and moisture content in in vitro conditions. Thus, the applicability of the present study needs to be verified in in vivo conditions. Furthermore, the teeth in clinical conditions are subjected to different functional and nonfunctional stresses. Hence, further research is required to understand the effect of stresses on the interface between composite and tooth surface and its impact on resultant microleakage.
| Conclusion|| |
The present study concluded that the gingival voids was maximum in the only bulk-fill composite group, minimum in the co-cure group, and least in the precure group. The cervical voids were maximum in the co-cure group and bulk-filled group followed by precure group. The occlusal voids were maximum in the co-cure group and were found to be similar in precure and only bulk-fill restorations. The extent of microleakage was found to be maximum in the co-cure group followed by only bulk-fill restorations and precure group. The precure lining technique was better than co-cure lining technique in terms of both microleakage and internal voids.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4]