|Year : 2016 | Volume
| Issue : 4 | Page : 324-330
A comparative microleakage evaluation of three different base materials in Class I cavity in deciduous molars in sandwich technique using dye penetration and dentin surface interface by scanning electron microscope
Babita Niranjan1, Nandihalli Devendrappa Shashikiran2, Shilpy Singla3, Ruchi Thakur4, Aashutosh Dubey5, Satish Maran1
1 Department of Pedodontics and Preventive Dentistry, Rishiraj College of Dental Sciences, Bhopal, Madhya Pradesh, India
2 Department of Pedodontics and Preventive Dentistry, College of Dental Science, Karad, Maharashtra, India
3 Department of Pedodontics and Preventive Dentistry, People's College of Dental Sciences and Research, Bhopal, Madhya Pradesh, India
4 Department of Pedodontics and Preventive Dentistry, RKDF College of Dental Science, Bhopal, Madhya Pradesh, India
5 Department of Periodontology and Oral Implantology, People's Dental Academy, Bhopal, Madhya Pradesh, India
|Date of Web Publication||29-Sep-2016|
Department of Pedodontics and Preventive Dentistry, Rishiraj College of Dental Sciences, Bhopal, Madhya Pradesh
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Introduction: A major objective in restorative dentistry is the control of marginal leakage, which may occur because of dimensional changes or lack of adaptation of restorative material to the cavity preparation. Numerous techniques have been advocated to overcome polymerization shrinkage in composite restorations. Aim and Objectives: This study investigated microleakage of three different bases under composite resin in sandwich technique using dye penetration and dentin surface interface using scanning electron microscope (SEM). Materials and Methods: Sixty extracted deciduous molars were stored in distilled water and Class I cavities with a width of about one-fourth of intercuspal distance and a depth of 0.5-1 mm below the dentino-enamel junction was prepared without bevels. In Group 1 - glass ionomer cement (GIC); Group 2 - mineral trioxide aggregate (MTA); Group 3 - Biodentine™ was placed as a base under composite. Teeth were longitudinally sectioned in two halves, through the centers of the restoration, immersed in 2% methylene blue and microleakage was evaluated under stereomicroscope and surface interface between base and dentin was evaluated under SEM. Results:Under the condition of in vitro study, less microleakage and less internal gaps were seen in Biodentine™ (0.00 ± 0.00 and 4.00 ± 1.59) group than MTA (0.00 ± 0.00 and 6.08 ± 1.82) and GIC (25.25 ± 6.57 and 14.73 ± 3.72, respectively) and showed very strong positive correlation between microleakage and internal gaps. Conclusion: Biodentine™ exhibits superior marginal sealing ability as well as marginal adaptation under composite resin as compared to MTA and GIC.
Keywords: Biodentine™, composite, glass ionomer cement, microleakage, mineral trioxide aggregate
|How to cite this article:|
Niranjan B, Shashikiran ND, Singla S, Thakur R, Dubey A, Maran S. A comparative microleakage evaluation of three different base materials in Class I cavity in deciduous molars in sandwich technique using dye penetration and dentin surface interface by scanning electron microscope. J Indian Soc Pedod Prev Dent 2016;34:324-30
|How to cite this URL:|
Niranjan B, Shashikiran ND, Singla S, Thakur R, Dubey A, Maran S. A comparative microleakage evaluation of three different base materials in Class I cavity in deciduous molars in sandwich technique using dye penetration and dentin surface interface by scanning electron microscope. J Indian Soc Pedod Prev Dent [serial online] 2016 [cited 2018 Dec 9];34:324-30. Available from: http://www.jisppd.com/text.asp?2016/34/4/324/191410
| Introduction|| |
The restoration of deciduous teeth remains a clinical challenge; the most adhesive materials used are mainly composite resin, glass ionomer cement (GIC), and hybrid GIC. Amalgam was earlier considered the material of choice for restoring posterior teeth. However, due to its unpleasing appearance coupled with the potential of mercury toxicity, composites came up as a potential alternative. Composite resins though are widely used in smaller lesions, use of composite resins in larger cavity lesions is still a challenge, because of polymerization shrinkage which leads to gap formation.  In larger restorations to reduce the effect of polymerization shrinkage, use of an intermediary bonding base material like GIC may be beneficial. The technique is referred to as "sandwich technique" which was introduced in the early 1990s.  GIC is considered a gold standard for sandwich technique due to properties such as potential to adhere to tooth structure, good sealing ability, fluoride releasing potential, and prevents recurrent caries. On the other hand polymerization, shrinkage decreases as bulk of composite resin decreases.  Disadvantages include moisture sensitivity which influences both physico-mechanical properties and bond strength of GIC to tooth structure, abrasive nature, and less aesthetic as compared to composite restorations. 
Recently, new materials like mineral trioxide aggregate (MTA) and Biodentine™ are introduced which are less sensitive to the application procedures, with improved mechanical and physical properties, and with better control during clinical handling. MTA was originally formulated to provide the physical properties, setting requirements, and characteristics necessary for an ideal repair and medicament material. The main advantage includes the presence of moisture for complete setting, proper sealing ability, chemical bond with tooth structure and regenerative properties. On the other hand, potential disadvantages of MTA are setting time is 24 h, poor handling properties. Biodentine™ has some features which are superior to MTA. As the setting is faster, there is a lesser risk of bacterial contamination. It exhibits better characteristics of biocompatibility and sealing ability, as when it set in alkaline pH leads to controlled formation of calcium salts. 
The adhesive nature of restorative materials can be analyzed by scanning electron microscope (SEM), which allows a qualitative evaluation of the adhesive interfaces created between the dentin biostructure and surface prepared from two different material adhesive systems in the sandwich technique. 
Hence, the aim of present study was to evaluate sealing ability of GIC, MTA, and Biodentine™ as a dentin substitute in sandwich technique in deciduous molars and surface interface of these materials with dentin interface by two techniques dye penetration and SEM.
| Materials and Methods|| |
The study was an in vitro comparative study conducted in the department of Pedodontics and Preventive Dentistry. The study was approved by ethical clearance of the institutional review board. The parents of patient were explained about the procedure and asked to sign "WHO parent Informed consent form." Freshly extracted sixty intact, noncarious deciduous molars without hypoplasia, any restoration, and any cracks were collected from the department. Samples were randomly divided into three groups - control group (Group 1) and two experimental groups (Groups 2 and 3) depending on the base materials used [Figure 1]. All soft tissue and debris were removed using ultrasonic tip and specimens were washed with 40% polyacrylic acid and cleaned with pumice slurry or water spray. The extracted molars were stored in deionized water at room temperature till the commencement of the study, for not more than 1 week. ISO (1991) reported that no other chemical agent than deionized water should be used since other agents may be absorbed by, and alter tooth substance.  The crowns were separated from roots with a double sided diamond disc under continuous irrigation at the level of cementoenamel junction. Using a diamond straight fissure bur (No. 030), Class I cavity was prepared with a width of about one-fourth of intercuspal distance and a depth of 0.5-1 mm below the dentino-enamel junction (DEJ) without bevels. Cavities were thoroughly cleaned with 30% phosphoric acid gel (3M ESPE, USA) for effective removal of smear layer. According to the base material used for the sandwich technique, samples were randomly divided into groups as follow.
|Figure 1: Group allocation into control group (Group 1 -glass ionomer cement) and experimental group (Group 2 -mineral trioxide aggregate and Group 3 -Biodentine)|
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Group 1 (control group)
Type IX GIC (GC corporation® , Tokyo, Japan) was mixed as per manufacturer's instructions and applied as the base of 1 mm. After initial setting of GIC (1-4 min) cavity was etched with 37% phosphoric acid gel (3M) for 15 s and rinsed for 10 s. Single Bond adhesive system (3M ESPE, USA) was applied in two layers and subjected to gentle air current for 5 s to evaporate the solvent. After application of bond adhesive system curing of each layer of adhesive was done for 20 s. Composite resin (Z-100, 3M ESPE, USA) was placed in increment technique and each layer was cured for 20 s.
Group 2 (experimental group)
ProRoot MTA (Maillefer, Dentsply, Switzerland) was mixed as per manufacturer's instructions and applied as a base of 1 mm. The paste was obtained by mixing 3 part of powder with 1 part of water to obtain a putty consistency. The mixture was homogenous and with a consistency similar to wet sand. Then small increment of MTA was introduced into the prepared Class I cavity with amalgam carrier and condensed with a plugger. The moist cotton pellet was left over MTA for the complete setting of the material and was sealed with the temporary restorative material. The samples were incubated at 37°C for 24 h. After incubation, temporary filling material along with moist cotton pellet was removed followed by placement of the final composite restoration.
Group 3 (experimental group)
Biodentine™ (Septodont Healthcare India Pvt. Ltd., Mumbai, India) was mixed as per manufacturer's instructions and applied as a base of 1 mm. Paste was obtained by mixing 3 part of powder with 1 part of water to obtain a putty consistency. The mixture was homogenous and with a consistency similar to wet sand. Then small increment of Biodentine™ was introduced into the prepared Class I cavity with amalgam carrier and condensed with a plugger. After complete setting of Biodentine™, final composite restoration was placed.
All samples were subjected to 500 rounds of thermocycling at 5/55°C with a dwell time of 60 s. The tooth surfaces were dried and covered with two layers of nail varnish up to 1 mm from the restoration margins.
Sample preparation for stereomicroscope
Collected samples were immersed in 2% methylene blue (Scientific Products, West Chester, PA, USA) for 24 h followed by rinsing of teeth under running water for 30 s. The teeth were longitudinally sectioned in mesiodistal direction in two halves, through the centers of the restoration, with double ended diamond disc in high-speed handpiece using a water coolant. The depth of dye penetration was evaluated using stereomicroscope with ×20 and ×40 lenses (iNEA Olympus Pvt. Ltd., New Delhi, India). Representative images were recorded from all specimens, and maximum degree of dye penetration was registered according to the following scores (ISO/TS 11405-2003):
- 0 = No dye penetration
- 1 = Dye penetration into the enamel part of the cavity wall
- 2 = Dye penetration into the dentin part of the cavity wall but not including the pulpal floor of the cavity
- 3 = Dye penetration including the pulpal floor of the cavity. 
Sample preparation for scanning electron microscope
For evaluation of surface interface between base and the dentin, five specimens from each group were randomly selected. All samples were washed; air dried and were attached to aluminum stubs and then sputtered with a 2000Ε thick layer of gold under sputtering unit (JEOL JFC-1600, Auto fine coater). Dentin surface evaluation was done using SEM (JEOL JSM-6390A) with a magnification of ×10-×20,000.
| Results|| |
Data analysis was done using Statistical Package for Social Sciences version 21 for windows (Armonk, NY: IBM Corp.). [Table 1] shows mean and standard deviation values of microleakage (μm) [Table 1]. Mean value and standard deviation of microleakage (μm) for control group (GIC, n = 20) was 25.25 ± 6.57, whereas for experimental groups MTA (n = 20) and Biodentine™ (n = 20) it was 0.00 ± 0.00 and 0.00 ± 0.00 μm, respectively. [Table 2] shows mean and standard deviation values of microleakage scores [Table 2]. Mean value and standard deviation for GIC was 2.00 ± 0.00, whereas for MTA and Biodentine™ it was 0.00 ± 0.00 and 0.00 ± 0.00 respectively [Figure 2]a-c.
Microleakage (μm) and microleakage scores, were assessed by nonparametric test Kruskal-Wallis ANOVA followed by Mann-Whitney U-test, which was used for pair-wise comparison. Kruskal-Wallis ANOVA showed a significant difference between the control group (GIC) and experimental groups (MTA and Biodentine™) (P < 0.05). In addition, MTA and Biodentine™ did not show any significant difference in microleakage.
|Figure 2: (a) Stereo-microscopic images using dye penetration method for glass ionomer cement. (b) Stereo-microscopic images using dye penetration method for mineral trioxide aggregate. (c) Stereo-microscopic images using dye penetration method for Biodentine|
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Internal gaps were assessed by one-way ANOVA followed by Tukey post hoc test which was used for pair-wise comparison. The mean value and standard deviation for GIC were 14.73 ± 3.72, whereas for MTA and Biodentine™ it was 6.08 ± 1.82 and 4.00 ± 1.59, respectively. Tukey's post hoc test showed a significant difference in internal gaps (μm) when compared between both GIC and MTA, as well as GIC and Biodentine™ (P < 0.05). However, there was no significant difference observed between MTA and Biodentine™ at dentin interface [Table 3] [Figure 3]a-c. Spearman's rho test showed very strong positive and significant (P < 0.05) correlation between microleakage and internal gaps in experimental base materials [Table 4]. It means as the size of internal gaps increases; microleakage also increases [Figure 4].
|Figure 3: (a) Microscopic images of specimens where the base of glass ionomer cement was applied, showed internal gaps between dentin and base material. (b) Microscopic images of specimens where the base of mineral trioxide aggregate was applied, showed less internal gap between dentin and base material. (c) Microscopic images of specimens where the base of Biodentine™ was applied, showed less internal gap between dentin and base material|
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|Figure 4: Correlation between microleakage and internal gaps in experimental base materials|
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|Table 4: Correlation between microleakage and internal gaps in experimental base materials|
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| Discussion|| |
One of the main goals in restorative dentistry is the control of marginal leakage, which may occur due to dimensional changes or lack of adaptation of restorative material to cavity preparation, leading to recurrent caries and pulpal disease.  Adaptation of the restorative material to cavity margins and internal cavity surface is of great importance for the long-term performance of restoration.  A major factor responsible for defects at the marginal and internal interface of restoration is shrinkage that accompanies polymerization of composite restorative material. This phenomenon results in a change in density of material, generating a reduction of 1.7-5.7% in volume. The shrinkage stress may cause failure in the bond, generating gap formation (10-15 μm).  These openings or gaps have deleterious effects as they allow the transit of fluids and bacteria between dentin-pulp complex and oral environment, which often leads to postoperative sensitivity and secondary caries formation.  To overcome the polymerization shrinkage different restorative techniques like horizontal incremental technique, oblique incremental technique, sandwich technique has been recommended. In a "sandwich technique," the resin composite is replaced in the dentin part of the cavity by a suitable base material with lower elastic modulus. Sandwich restoration with conventional GIC was introduced in the 1977 by McClean with the aim to minimize effects of resin composite polymerization shrinkage.  Glass ionomer sets as a result of a reaction between an acid and a base, with the product of the reaction, a hydrogel salt, acting as a binding matrix.  GIC has properties like the ability to adsorb permanently to hydrophilic surfaces of hard oral tissues, capacity of fluoride ion release and uptake. However, in the cavity or in areas where proper isolation cannot be achieved glass ionomer cannot be used, as moisture and contaminants not only influences the bond strength of glass ionomer tooth; but negatively influences the physicomechanical properties of materials as well.  To overcome these disadvantages various materials like MTA and Biodentine™ are introduced. MTA shares many properties with glass ionomer as it can form chemical bond with tooth structure, compressive strength is comparable to dentin, high sealing ability, highly bio-compatible and radio-opaque. MTA is a Portland cement, which was introduced in dental literature by Torabinejad in 1993. The advantage of MTA over to glass ionomer is that it is not sensitive to moisture; in fact, moisture is necessary for its setting reaction. Therefore, it is advised to place a wet cotton pellet over the MTA in the first visit followed by replacement with permanent restoration at the second visit.  Torabinejad et al. suggested that sealing ability of MTA is not influenced by contamination with blood, and it exhibited a better seal compared to other materials under study.  Despite its good physical, biological properties and being hydrophilic in nature, its disadvantages include toxic arsenic content, the material is expensive, difficult to handle and long setting time. According to Torabinejad et al. setting time of gray MTA is about 2 h and 45 min (±5 min), whereas Islam et al. reported 2 h and 55 min for gray MTA, and 2 h and 20 min for white MTA.  The majority of studies demonstrated that the final setting time continues for 24-72 h which is similar with GIC. Hence, the search for an alternative to MTA material is aimed to reduce cost, setting time, improve handling properties, biocompatibility, and to increase feasibility to both professional and patient.
Biodentine™ was developed by Septodont's research group as a new class of dental material which could conciliate high mechanical properties with excellent biocompatibility, as well as a bioactive behavior.  The decrease of the liquid content in the system decreases setting time to harden within 9-12 min.  Biodentine™ proves superior to MTA as it does not require a two-step placement and the setting is faster, so there is a lower risk of bacterial contamination. In the present study, Class I cavity was prepared with a width of about one-fourth of intercuspal distance and a depth of 0.5-1 mm below the DEJ without bevel. Thermocycling is used to mimic intra-oral temperature variations and subjecting the restoration on the tooth to temperature extremes compatible with oral cavity. 
In this study, microleakage was evaluated using dye leakage method and methylene blue dye was used. The use of dyes is one of the oldest and most common methods of studying microleakage. Kersten and Moorer found that leakage of the commonly used dye methylene blue was comparable with that of a small bacterial metabolic product of similar molecular size. Methylene blue is a small molecular weight dye which has high penetration ability. 
The result of the present study revealed that MTA and Biodentine™ have significantly less microleakage when compared with GIC base (25.25 μm). The inability of conventional GIC to produce an effective seal can be attributed to two factors: The material's sensitivity to moisture during placement and the dehydration after setting resulted in crazing and cracking.  The physical properties of cement might be influenced by crystal size. Smaller particle increases surface contact with the mixing liquid and leads to greater early strength as well as ease of handling. Lee et al. reported particle sizes ranging from 1 to 10 μm for grey-MTA powder, before hydration.  Motamedi et al. conducted a study on MTA and GIC to evaluate the microleakage in sandwich techniques in Class II composite techniques and found that MTA could be as efficacious as glass ionomer in decreasing microleakage.  Biodentine™ showed significantly less microleakage than GIC; because Biodentine™ is composed of a mixture of 5 μm round particles embedded in a calcium silicate hydrate matrix which are very smaller than the size of MTA particle.  Raskin et al. investigated the microleakage of Class II sandwich technique with a biocompatible Ca 3 SiO 5 -based dentin substitute and found that Biodentine™ can be indicated in open-sandwich Class II restorations without any preliminary treatment. 
When examining under SEM, mean diameter of internal gaps for Group 3 (Biodentine™) was 4.00 ± 1.59 μm, which is found to be statistically significant. This could be attributed to when Biodentine™ come in contact with dentin, results in the formation of tag-like structures along the side of an interfacial layer. This is called as "mineral infiltration zone," where the alkaline caustic effect of the calcium silicate cement's hydration products degrades the collagenous component of the interfacial dentin.  Koubi et al. evaluated the tolerance of Biodentine™ covered with a composite resin and demonstrated that when it is covered with a composite, Biodentine™ is a convenient, efficient and well-tolerated dentin substitute and can be used as a dentin substitute under a composite for posterior restoration.  In the present study, mean diameter of internal gaps for control group (GIC) was 14.73 ± 3.72 μm, as in glass ionomer polyacrylic and tartaric acid and their salt hinders the penetration of material. Furthermore, during setting, GIC absorb a considerable amount of water, which may affect their sealing ability and physical properties. 
| Conclusion|| |
The conclusion of present study are:
- Less microleakage and internal gaps were present in Biodentine™ group than MTA (experimental group) and GIC (control group). There was significant difference between the control group (GIC) and experimental groups (MTA and Biodentine™) (P < 0.05)
- A very strong positive and significant (P < 0.05) correlation was seen between microleakage and internal gaps in experimental base materials. It indicates as size of internal gaps increases, microleakage also increases
- Although all materials can be used as a suitable base (dentin replacement material) in the sandwich technique, Biodentine™ exhibits superior marginal sealing ability as well as marginal adaptation and confirms best as dentin substitute under composite resin as compared to MTA and GIC.
Take this opportunity to express my profound gratitude and deep regards to my guide Dr. Nandihalli Devendrappa Shashikiran MDS Professor and Head of the Department for his impeccable guidance, monitoring and constant encouragement throughout the course of this thesis. I thank my parents for showering their blessings and love on me, which has provided me with the inspiration and zest to tread through the path of life.
Financial support and sponsorship
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]