Journal of Indian Society of Pedodontics and Preventive Dentistry
Journal of Indian Society of Pedodontics and Preventive Dentistry
                                                   Official journal of the Indian Society of Pedodontics and Preventive Dentistry                           
Year : 2014  |  Volume : 32  |  Issue : 2  |  Page : 140--148

Effect of polishing on the microleakage of three different restorative materials: An in vitro study


Arnab Sengupta, Anil Gupta, Renu Dagur 
 Department of Pedodontics and Preventive Dentistry, IDST Dental College, Kadrabad, Modinagar, Ghaziabad, Uttar Pradesh, India

Correspondence Address:
Arnab Sengupta
Department of Pedodontics and Preventive Dentistry, IDST Dental College, Kadrabad, Modinagar, Ghaziabad, Uttar Pradesh
India

Abstract

Aims and Objectives: The purpose of this in vitro study was to investigate the effect of polishing systems on the microleakage of three different restorative materials (Ketac Molar Easymix, Ketac N100 and Filtek P90). Materials and Methods: Class V cavities were prepared at the cemento-enamel junction of 60 freshly extracted premolars. The prepared teeth were randomly divided into three groups and restored with the three materials. The restored teeth were stored in distilled water at 37°C for 1 week. The restored teeth were then divided into two subgroups (polished and not polished) of 10. Finishing and polishing of the polished group was done using the Sof-Lex polishing system. Furthermore, all the restorations were subjected to dye penetration testing. Results: Results showed that maximum microleakage was observed for the not polished group of Filtek P90 and least levels of microleakage were seen for the polished group of Ketac Molar Easymix. Conclusion: There was a significant difference seen when Ketac Molar Easymix was compared with Ketac N100 and Filtek P90 in terms of the extent of microleakage exhibited on polishing of the three materials; with the former exhibiting the least microleakage scores.



How to cite this article:
Sengupta A, Gupta A, Dagur R. Effect of polishing on the microleakage of three different restorative materials: An in vitro study.J Indian Soc Pedod Prev Dent 2014;32:140-148


How to cite this URL:
Sengupta A, Gupta A, Dagur R. Effect of polishing on the microleakage of three different restorative materials: An in vitro study. J Indian Soc Pedod Prev Dent [serial online] 2014 [cited 2022 Sep 29 ];32:140-148
Available from: http://www.jisppd.com/text.asp?2014/32/2/140/130969


Full Text

 Introduction



The search for restorative materials with the ability to promote dental structure sealing reflects the constant introduction of new products in the market. Two types of restoratives emerged, glass-ionomers and composites, where each in their differing ways fulfilled most of the requirements of a successful restorative material.

Glass-ionomer cements were first introduced to the dental profession in 1972 by Wilson and Kent. Their favorable adhesive and fluoride-releasing properties have led to their widespread use as restorative, lining and luting materials. In recent years, developments in the field of glass-ionomer cements have led to the introduction of hybrid versions of the material, which are light cured. They were introduced to help overcome the problems of moisture sensitivity and low early mechanical strengths associated with the conventional glass-ionomer cements and at the same time maintain their clinical advantages.

Composite resins are one of the most heavily researched materials in dentistry today. Composite resins are being used routinely in class III and V restorations and with increasing frequency in class I and II restorations. One of the major shortcomings of composite restorations is the polymerization contraction during setting those results in microleakage (Ben-Amar, 1989).

In recent times, a new category of polymers for dental restorative use have been introduced, that is the silorane based composites. Polymerization of silorane based composites occurs through a photocationic ring opening reaction which results in lower polymerization contraction compared to the methacrylate based composites. [1]

It is generally accepted that a smooth surface has a beneficial effect on the esthetic quality and longevity of the restoration, as well as on its biocompatibility with the oral tissues. Furthermore, the benefits of a smooth restoration are: [1]

Minimal irritation of soft and hard tissuesStimulates natural tooth surface estheticsLess likely to trap food debris and plaqueReduced potential for corrosionMore hygienic.

The proper finishing and polishing of dental restoratives are critical clinical procedures and very important for the esthetics and longevity of restorations.

Henceforth, the objectives of this study are:

To evaluate the marginal integrity of three restorative materials (Ketac Molar Easymix, Ketac N100 and Filtek P90) in class V cavities through a stereomicroscopic observation.To determine the effect of finishing and polishing on the differences in microleakage of three restorative materials (Ketac Molar Easymix, Ketac N100 and Filtek P90) following finishing/polishing.

 Materials and Methods



A sample of 60 freshly extracted caries free human premolars extracted for orthodontic purposes were collected for the study [Figure 1]. The teeth were first cleaned with an ultra-sonic scaler, and then disinfected with 10% formosaline for 10 min and stored in distilled water at 4°C until required for use. The teeth were then mounted in dental plaster till their cemento-enamel junctions leaving the crowns exposed [Figure 2]. Conventional class V cavities (mesiodistal width of 3 mm, occlusogingival length of 4 mm, and a depth of 2 mm) were prepared on the buccal surfaces 1.5 mm above the cemento-enamel junction with an ISO size (No. 010) straight fissure bur and (No. 014) inverted cone. The occlusal margins of the preparation were in enamel, and the gingival margins were in dentin. The shape of the cavity was box shaped with rounded internal line angles. Following cavity preparation, specimens were randomly divided into three experimental groups (Group I, Group II and Group III) with a number of teeth in each group (n) = 20. Group I consisted of restored teeth with conventional glass-ionomer cement (Ketac Molar Easymix). Group II consisted of restored teeth with resin modified glass-ionomer cement (Ketac N100). Group III consisted of restored teeth with silorane based composite (Filtek P90).

Each of the three groups was further divided into two subgroups of 10 samples each (subgroup A and subgroup B) [Figure 3]. Subgroup A, consisted of teeth which underwent no finishing/polishing. Subgroup B consisted of teeth, which were subjected to immediate finishing/polishing.For subgroup A, no finishing/polishing was done and the teeth were stored in distilled water at 37°C for 1 week.For subgroup B, immediate finishing/polishing was done following which teeth were stored in distilled water at 37°C for 1 week. The polishing systems were used as recommended by the manufacturer. A new bur, disc or cup was used after every five restorations [Table 1].{Table 1}{Figure 1}{Figure 2}

In preparation for dye penetration testing, the teeth were sealed with nail varnish at the apex of the roots, leaving the finished restorations and 1·5 mm beyond the margins exposed to dye. The restorations were then placed in 1% aqueous basic fuchsin dye for 24 h at 37°C [Figure 4].{Figure 3}{Figure 4}

After removal from the dye solution, the teeth were cleaned and sectioned longitudinally through the restorations in a buccopalatal/lingual plane using a diamond disc.

The specimens were observed under stereomicroscope with a magnification of ×10 (Motic; Model No: SMZ 143 series) [Figure 5]. The degree of marginal leakage was determined by the criteria described by Khera and Chan (1978) as follows:{Figure 5}

0° = No leakage [Figure 6]

1° = Less than and up to one-half of the depth of the cavity preparation was penetrated by the dye [Figure 7]

2° = More than one-half of the depth of the cavity preparation was penetrated by the dye, but not up to the junction of the axial and occlusal or cervical wall [Figure 8]

3° = Dye penetration was up to the junction of the axial and occlusal or cervical wall, but did not include the axial wall [Figure 9]

4° = Dye penetration included the axial wall.

Data were subjected to statistical analysis using SPSS (IBM ® SPSS (software package used for statistical analysis ) ® Statistics 20 Student Version (manufactured in august 2011)) Software (Version 20). To find whether the microleakage in the three groups were homogeneous, the microleakage scores were subjected to one-way ANOVA and unpaired t-tests.{Figure 6}{Figure 7}{Figure 8}{Figure 9}

 Results



Group I:

Amongst the polished group 60% (6) samples showed no microleakage. 20% (2) samples showed microleakage up to a depth less than half of the prepared cavity. 0% (0) samples showed microleakage up to a depth more than half of the prepared cavity and 10% (1) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 10% (1) samples exhibited microleakage along the axial wall [Table 2] and [Table 3], [Figure 10]. {Table 2}{Table 3}{Figure 10}

Amongst the not polished group, 40% (4) samples showed no microleakage. 20% (2) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (1) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 30% (3) samples exhibited microleakage along the axial wall [Table 2] and [Table 4], [Figure 10].{Table 4}

The calculated mean of microleakage score for the polished group was 0.9 and the standard deviation was 1.4491 [Table 5], [Figure 11].{Table 5}

The calculated mean of microleakage score for the not polished group was 1.6 and the standard deviation was 1.7764 [Table 3], [Figure 11].{Figure 11}

Group II

Amongst the polished group 40% (4) samples showed no microleakage. 30% (3) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (1) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 20% (2) samples exhibited microleakage along the axial wall [Table 2] and [Table 3], [Figure 12].{Figure 12}

Amongst the not polished group, 20% (2) samples showed no microleakage. 40% (4) samples showed microleakage up to a depth less than half of the prepared cavity. 20% (2) samples showed microleakage up to a depth more than half of the prepared cavity and 20% (2) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 0% (0) samples exhibited microleakage along the axial wall [Table 2] and [Table 4], [Figure 12].

The calculated mean of microleakage score for the polished group was 1.3 and a standard deviation of 1.5670 [Table 5], [Figure 11].

The calculated mean of microleakage score for the not polished group was 1.4 and the standard deviation was 1.0749 [Table 5], [Figure 11].

Group III

Amongst the polished group 30% (3) samples showed no microleakage. 50% (5) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (1) samples showed microleakage up to a depth more than half of the prepared cavity and 10% (1) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 0% (0) samples exhibited microleakage along the axial wall [Table 2] and [Table 3], [Figure 13].{Figure 13}

Amongst the not polished group, 0% (0) samples showed no microleakage. 40% (4) samples showed microleakage up to a depth less than half of the prepared cavity. 20% (2) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 40% (4) samples exhibited microleakage along the axial wall [Table 2] and [Table 4], [Figure 13].

The calculated mean of microleakage score for the polished group was 1.0 and a standard deviation of 0.9428 [Table 5], [Figure 11].

The calculated mean of microleakage score for the not polished group was 2.4 and the standard deviation being 1.4298 [Table 5], [Figure 11].

Intragroup comparison

Comparison was done between the microleakage scores between the specimens of the two subgroups (polished and not polished) for each of the three groups using an unpaired 't'test.

For group I (Ketac Molar easy Mix) the 't' value was found to be 0.3470, which was not significant (P > 0.05) [Table 6].{Table 6}

For group II (Ketac N100) the 't' value was found to be 0.8697, which was not significant (P > 0.05) [Table 6].

For group III (Filtek P90) the 't' value was found to be 0.0187, which was significant (P < 0.05) [Table 6].{Table 6}

Intergroup comparison

One way ANOVA test was carried out to compare the microleakage scores for the three different materials in polished and not polished groups individually.

The 'one way ANOVA 'F' score for the polished group was found to be 0.789237126, which was not significant (P > 0.05) [Table 7].{Table 7}

The 'one way ANOVA 'F' score for the not polished group was found to be 0.283394357, which was not significant (P > 0.05) [Table 8].{Table 8}

 Discussion



A major goal of restorative dentistry is achieving proper adhesion between restorative materials and the cavity walls resulting in good marginal sealing, less microleakage and longer life of the restoration.

Khera and Chan [2] in 1978 stated that since no material is exempted from microleakage, its information is useful for comparative assessment of different materials. The present study was carried out to assess the difference in microleakage of three restorative materials (Ketac Molar Easymix, Ketac N100, Filtek P90) having a good potential for use in pediatric dentistry. All the three restorative materials were chosen from the same manufacturer to avoid any bias.

The microleakage assessment was done by an in vitro method because in vitro tests remain an indispensable method for initial screening of dental materials and in vitro microleakage tests may set a theoretical maximal amount of leakage that could be present in vivo.[3],[4] Furthermore, in vitro microleakage studies are relatively easy to perform and effective in differentiating the quality of various materials in terms of their microleakage resisting potentials as compared to in vivo studies. However, it is the clinical assessment of the materials that reveals their actual performance levels. [5]

The study was conducted on extracted premolars due to the ease of availability of the teeth, on which a cavity with uniform shape and dimension could be prepared. Class V cavities were prepared to assess microleakage to rule out any influence of occlusal loading on microleakage.

Furthermore, it should be noted that even though thermocycling is a widely acceptable method used in in vitro microleakage studies [6] it has not been incorporated in this study. Moreover, some researchers consider it a questionable method. [7],[8] The question is about the validity and clinical significance of the thermocycling method, since the temperatures used to stress restorations may not be the real temperatures of cold and hot food/beverage tolerated by patients.

In this study, aqueous basic fuchsin (1%) was the dye used for microleakage evaluation. Although aqueous basic fuchsin is water based dye and can penetrate the glass-ionomer cement, several studies in which this dye was used, showed that dentin and restoration staining differed more from the actual fissures between the cavity walls and the restoration materials.

It should be noted that the effect of polishing systems on microleakage is material and tissue dependent. For conventional cements polishing at ultra-high speeds can decrease microleakage resistance at the dentin margins. For resin-modified cements, systems utilizing wet polishing technique results in better microleakage resistance at the enamel margins. [9]

Group I-ketac molar easymix

The conventional glass-ionomer cements present chemical adhesion to the tooth, low linear thermal expansion coefficient, similar to the dental structure and small setting shrinkage. Therefore, it would be expected to avoid microleakage and all its consequences.

In the present study, among the polished group 60% (12) samples showed no microleakage. 20% (4) samples showed microleakage up to a depth less than half of the prepared cavity. 0% (0) samples showed microleakage up to a depth more than half of the prepared cavity and 10% (2) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 10% (2) samples exhibited microleakage along the axial wall.

Among the not polished group, 40% (8) samples showed no microleakage. 20% (4) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (2) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 30% (6) samples exhibited microleakage along the axial wall.

After, subjecting these values to statistical analysis by an unpaired t-test, it was observed that there was no significant difference between the microleakage of both groups.

Class V cavity was prepared 1.5 mm occlusally from the cemento-enamel junction. Both cavity margins were made in enamel as various studies showed a difference in microleakage between occlusal and gingival margins. Bonding to dentin is far more challenging and less predictable than bonding to enamel because dentin is inorganic in nature, about 75% as opposed to enamel, which is 95% inorganic. [10],[11]

Matrix was not used for insertion of glass-ionomer cement as a study showed that restorations inserted without a matrix strip exhibited less leakage than those with a matrix strip.

Bottled version of conventional glass-ionomer cement was used rather than encapsulated one because it is more commonly used due to its low cost compared to encapsulated one. [12]

Even though glass-ionomer cement may show some microleakage it provides a means of restoring primary molars with a minimal amount of destruction of sound tissue and reduces treatment time in a young patient. Moreover, the local fluoride release also presents a potential advantage in pediatric dentistry when the quality of the restoration often damaged by unsuitable children's behavior. [13]

Group II-ketac N100

In the present study, among the polished group 40% (8) samples showed no microleakage. 30% (6) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (2) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 20% (4) samples exhibited microleakage along the axial wall.

Among the not polished group, 20% (4) samples showed no microleakage. 40% (8) samples showed microleakage up to a depth less than half of the prepared cavity. 20% (4) samples showed microleakage up to a depth more than half of the prepared cavity and 20% (4) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 0% (0) samples exhibited microleakage along the axial wall.

After subjecting these values to statistical analysis by an unpaired t-test, it was observed that there was no significant difference between the microleakage of both groups.

Glass-ionomer resin composite hybrid materials show curing shrinkage within 5 min after polymerization, increasing over a 24 h period. This rapid initial shrinkage is the result of free-radical polymerization of resin monomers incorporated in the materials. Significantly higher values of curing shrinkage were found for glass-ionomer-resin hybrid materials than for conventional ones. Nevertheless, it might be speculated that setting stresses on the bond of glass-ionomer-resin composite hybrid materials to tooth were not sufficient to result in a significant gap formation and increased microleakage. Gap formation at the tooth restoration interface may have occurred, but was compensated for by swelling from water sorption. The structure of a set glass-ionomer resin composite hybrid material contains a high proportion of hydrophilic functional groups in a highly cross linked matrix. This can be linked to the synthetic hydrogel that will take up water and swell on exposure to moisture. This is a probable explanation to the result obtained in this study where 40% of the polished and 20% of the not polished samples of resin modified glass-ionomer exhibited no microleakage. [14]

Another view for this result has been supported by the study of Rossomando and Wendt [15] in 1995. Even though, the linear coefficient of thermal expansion of resin modified glass-ionomer is higher than the conventional glass-ionomer; dimensional changes resulting from thermal expansion may not be as great as the linear coefficient of thermal expansion would predict because resin modified glass-ionomer is a better thermal insulator than conventional glass-ionomer.

Group III-filtek P90

Resin composite restorations show significant differences in the resin matrix composition as well as in the filler, which influences the properties of materials, including polymerization shrinkage.

In the present study, among the polished group 30% (6) samples showed no microleakage. 50% (10) samples showed microleakage up to a depth less than half of the prepared cavity. 10% (2) samples showed microleakage up to a depth more than half of the prepared cavity and 10% (2) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 0% (0) samples exhibited microleakage along the axial wall.

Among the not polished group, 0% (0) samples showed no microleakage. 40% (8) samples showed microleakage up to a depth less than half of the prepared cavity. 20% (4) samples showed microleakage up to a depth more than half of the prepared cavity and 0% (0) samples showed microleakage up to the junction of axial and cervical/occlusal wall. Only 40% (8) samples exhibited microleakage along the axial wall.

After subjecting these values to statistical analysis by an unpaired t-test, it was observed that there was a significant difference between the microleakage of both groups.

This could be attributed to two main factors that is marked reduction in polymerization shrinkage due to photo-ring opening cationic polymerization and a good bond strength adhesive bond with the tooth structure. [4] Sialorane based composites exhibit 0.9% volumetric shrinkage as compared to 2.3% to 3% for methacrylate based resins. It has been reported that the obtained tight interface at both enamel and dentin indicated that the two-step self-etch adhesive effectively bridged the hydrophilic tooth substrate with the hydrophilic silaorane based composite. [8] Besides this sialorane based composites have added advantage of absence of oxygen inhibition layer. [4]

Ketac molar easymix versus ketac N100

On comparison of group I and group II, it was found that there was no significant difference between the two groups in terms of microleakage scores of the polished and not polished specimens in these two groups.

Although resin modified glass-ionomer cements show higher bond strength to dental hard tissues than conventional materials (glass-ionomer cement), they exhibit variable results in microleakage tests. Not all of them display significantly less leakage against enamel and dentin than their conventional counterparts. This can be supported by work done by Sidhu [16] in 1994, where he found that conventional glass-ionomer cement presented interfacial gaps measuring 26 μm on an average, while the resin modified glass-ionomer cements presented interfacial gaps measuring 8-10 μm on an average. It has also been found that the initial bond obtained immediately after light curing of the resin modified glass-ionomer cement is stronger than that for chemically cured glass-ionomers.

Ketac molar easymix versus filtek P90

When group I was compared with group III, it was found that there was a significant difference between the two groups (P < 0.05) in terms of microleakage scores of the polished and not polished specimens in these two groups.

The polished specimens of the Ketac Molar Easymix group exhibited much lesser microleakage scores as compared to the polished specimens of the Filtek P90 group.

On similar lines, the not polished specimens of the Ketac Molar Easymix group exhibited lesser microleakage scores as compared to the not polished specimens of the Filtek P90 group.

To the best of our knowledge, no studies have been conducted to compare conventional glass-ionomer and a sialorane based composite.

Ketac N100 versus filtek P90

On comparison of group II versus group III, it was found that there was no significant difference between the two groups with Ketac N100 showing similar microleakage to Filtek P90. To the best of our knowledge, no studies have been conducted to compare resin modified glass-ionomer and a sialorane based composite.

Since new materials are constantly being introduced in the market of dentistry, short-term laboratory assessments are required because clinical evaluations are expensive, time consuming and require ethical clearance. [17],[18]

In contrast in vitro studies such as microleakage tests can provide important information on possible clinical performance of new restorative materials. These are methods of screening dental materials and determining the presence of microleakage, with the theoretical ability to transfer the findings to the clinical environment.

 Conclusions



Conclusions drawn from the study were:

Maximum number of samples of Ketac Molar Easymix had no microleakage as compared to Filtek P90.There was no significant difference between microleakage scores of Filtek P90 and Ketac N100.There was a significant difference seen when Ketac Molar Easymix was compared with Ketac N100 and Filtek P90.

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