Pesqui Odontol Bras v. 15, n. 4, p. 277-282, out./dez. 2001.

Dentstica

In vitro quantitative evaluation of marginal microleakage in class II restorations confected with a glass ionomer cement and two composite resins Avaliao quantitativa in vitro da microinfiltrao marginal em restauraes classe II, confeccionadas com um cimento de ionmero de vidro e duas resinas compostas
Maria Fernanda Borro BIJELLA* Maria Francisca Thereza Borro BIJELLA** Salete Moura Bonifcio da SILVA***
BIJELLA, M. F. B.; BIJELLA, M. F. T. B.; SILVA, S. M. B. da. In vitro quantitative evaluation of marginal microleakage in class II restorations confected with a glass ionomer cement and two composite resins. Pesqui Odontol Bras, v. 15, n. 4, p. 277-282, out./dez. 2001. This study evaluated, in vitro, marginal microleakage in class II restorations confected with the glass ionomer cement Vitremer and with the composite resins Ariston pHc and P-60. The aims of the study were to assess the effect of thermocycling on those materials and to evaluate two methods utilized in the analysis of dye penetration. Sixty premolars divided in three groups were utilized; the teeth had proximal cavities whose cervical walls were located 1 mm below the cementoenamel junction. Half of the test specimens from each group underwent thermocycling; the other half remained in deionized water, at 37C. The specimens were immersed, for 24 hours, in a basic 0.5% fuchsin solution at 37C. For the analysis of microleakage, the specimens were sectioned in a mesio-distal direction, and the observation was carried out with the software Imagetools. The results were evaluated through the 2-way ANOVA and through the Tukeys test. All groups presented marginal microleakage. The smallest values were obtained with Vitremer, followed by those obtained with the composite resins P-60 and Ariston pHc. There was no statistically significant difference caused by thermocycling, and the method of maximum infiltration was the best for detecting the extension of microleakage. UNITERMS: Dental leakage; Composite resins; Glass ionomer cements.

INTRODUCTION

Over the past years, aesthetical restorative dentistry has shown considerable progress, leading to the development of countless improved restoring materials for posterior teeth. Currently, the main concerns regarding the performance of these materials refer to their durability and to the integrity of marginal sealing13, especially in cavities that involve the cement region, where clinical problems are aggravated18. Many studies have evaluated the microleakage of different materials1,3,4,5,7,9,17,19,21,24,27, suggesting modifications in the materials themselves and in the restorative techniques, in an attempt to solve
this problem and increase the life span of restorations. Resin-modified glass ionomer cements are some of the most utilized dental materials in pedodontics. Besides their adhesive properties, these hybrid systems present fluoride release, biocompatibility and reduced syneresis and absorption, with enhanced control of the working time due to their photochemically activated resinous component20,26, being regarded as some of the best materials for the suppression of microleakage6. Up to now, their low resistance to compression and tension contraindicates their utilization in the proximal surfaces of posterior teeth20. That stimu-

Part of Dissertation for the obtainment of Master Degree. * Graduate Student, School of Dentistry of Bauru - USP. ** Associate Professor; ***PhD Department of Pedodontics, School of Dentistry of Bauru - USP.
BIJELLA, M. F. B.; BIJELLA, M. F. T. B.; SILVA, S. M. B. da. In vitro quantitative evaluation of marginal microleakage in class II restorations confected with a glass ionomer cement and two composite resins. Pesqui Odontol Bras, v. 15, n. 4, p. 277-282, out./dez. 2001.
lates the research on materials that surpass the glass ionomer without losing its excellent properties. Manufacturers have developed an aesthetically restorative material that can be accommodated within the dental cavity, for the confection of class I or class II restorations, which they denominated the condensable2 composite resin. The 3M company has recently released an evolution of the Z-100 resin, the Filtek P-60 resin; however, these resins still require a sensitive technique and a long clinical time span that is quite problematic when treating children. Also aiming at this segment of the market, Vivadent developed the Ariston pHc resin10,12,14. It is a resin that, according to the manufacturer, proportionally releases ions of calcium17, fluoride and hydroxyl11, when the pH of the oral cavity reaches values close to the critical limit. It inhibits or reduces the incidence of secondary caries8,15,25 and the formation of plaque, remineralizing the dental structure through the deposition of calcium and fluoride, and neutralizing the effect of acids with hydroxyl ions11,16,22. The aim of this study was: to assess, in vitro, marginal microleakage in class II restorations restored with a glass ionomer cement and with two composite resins, to test the usefulness of thermocycling these materials and, also, to analyze two methods utilized in the evaluation of marginal microleakage.
submitted to thermocycling distilled water baths of 15 seconds, at 5C ( 2) and 55C ( 2), totalizing 500 cycles. Thereafter, all teeth received two layers of nail polish, respecting a margin of 1 mm around the restorations. They were submerged in an aqueous basic 0.5% fuchsin solution for 24 hours at 37C and, finally, thoroughly rinsed in running water for 24 hours. For the analysis of microleakage, the teeth were sectioned in a mesio-distal direction, which produced 4 to 5 sections per specimen, with the thickness of 0.8 to 1.0 mm. Each identified section was then scanned. Two images were obtained for each segment, which resulted in 8 surfaces for the analysis. Dye penetration through the interface was measured with the Imagetools software. All sections obtained from the same tooth were analyzed, taking in account, for purposes of comparison between the groups, the average values of infiltration and the higher value of dye penetration. The data were analyzed through the 2-way ANOVA test and Tukeys multiple comparison test, with a significance level of 5%.

RESULTS

The results obtained with and without thermocycling can be seen in Table 1. They reveal the similarity between the behaviors of the materials, evaluated by means of the maximum infiltration values and by the average of the observed infiltration values. First, the statistic test was carried out with the average infiltration values (Table 2), and the existence of a statistically significant difference at the level of 5% was verified.
TABLE 1 - Mean values (X) and standard deviation (sd) of mean and maximum infiltration, obtained for the three tested materials, with and without thermocycling.

MATERIAL AND METHODS

One hundred and twenty proximal surfaces of sixty healthy human premolars were selected and randomly split into three groups containing 20 premolars each (40 cavities). The teeth from Group I were restored with the resin-modified glass ionomer cement Vitremer; the teeth from Group II, with the semi-condensable resin Ariston pHc and those from Group III received the condensable resin P-60. All materials were handled following the manufacturers instructions. The proximal cavities of the modified class II type (vertical slots) were standardized: their buccolingual width was 4 mm, their depth, 1 mm at the gingival wall, and the gingival margin was located 1 mm beyond the cementoenamel junction. The specimens were immersed in deionized water at 37C for 24 hours and the groups were subdivided. Half of the restorations were kept in deionized water at 37C and the other half was 278
Average Maximum Studied Thermomaterial cycling X (mm) sd (mm) X (mm) sd (mm) Vitremer Ariston pHc P-60 with without with without with without 0.0455 0.0280 0.6440 0.7165 0.5725 0.3715 0.0960 0.0504 0.3423 0.4291 0.3369 0.3322 0.1120 0.1145 0.9330 1.0260 0.8960 0.6215 0.2134 0.1729 0.4024 0.4507 0.3408 0.3829
TABLE 2 - Parameters for the 2-way ANOVA employing the values of mean infiltration obtained for each specimen.
Variation source Material Thermocycling Interaction

df Effect 2* 1 2

MS Effect 4.3127* 0.0710 0.0194

df Error 114* 114 114

MS Error 0.0895* 0.0895 0.0895

F 48.1846* 0.7938 2.1707

p 0.0000* 0.3748 0.1188
*Significant at the level of 5%. TABLE 3 - Tukeys test applied to mean values for multiple comparisons between the materials.
Studied material Vitremer P-60 Ariston pHc 0.0367 0.0472 0.0680
There is statistical difference between the groups that are not linked by a vertical bar.
The results from all groups were gathered in order to carry out the Tukeys test (Table 3). However, when using the maximum microleakage value obtained for each specimen (Table 4), besides the statistical significant difference between the tested materials (at the level 5%), the results also revealed a significant interaction between the groups. Therefore, in order to apply the Tukeys test, the groups were divided according to the submittal to thermocycling (Table 5).

DISCUSSION

In this research, an average of 4 sections of each tooth, cut in a mesio-distal direction, was obtained, allowing for up to eight analysis per tooth and for up to 160 analysis for each sub-group. Table 1 shows that Vitremer submitted to thermocycling, evaluated by means of the average
infiltration values, presented an average value of 0.0455 mm, which was similar to the results obtained when it was not submitted to thermocycling (0.0280 mm). These values came even closer to each other when the samples were evaluated by means of their maximum infiltration, corresponding to 0.1120 mm and 0.1145 mm for Vitremer with and without thermocycling, respectively. The proximity to zero, which means improved efficacy in reducing microleakage, can be imputed to the adhesion of the material to the dental structure and to the similarity between its thermal expansion ratio and that of the dental structure that was the material that presented the lowest microleakage values in this research. These data are in agreement with those obtained by several other authors4,19,21,24 who considered that the results obtained with Vitremer were the best ones. On the other hand, these results differ from those obtained by VIEIRA et al.27, who stated that there was no difference as to marginal microleakage when comparing Vitremer, Dyract and Compoglass, and from the results obtained by CARRARA5, who considered the performances of Vitremer, Compoglass and Z-100 similar to each other, although the materials and methodologies utilized were different. Table 1 also shows that the resin P-60 was the most affected by thermocycling. Regarding the average infiltration, P-60 presented values of

TABLE 4 - Parameters for the 2-way ANOVA using the maximum infiltration value found for each specimen.

df Effect 2* 1 2*

MS Effect 8.1052* 0.1068 0.3666*

df Error 114* 114 114*

MS Error 0.1172* 0.1172 0.1172*
F 69.1479* 0.9112 3.1277*

p 0.0000* 0.3418 0.0476*

*Significant at the level of 5%.
TABLE 5 - Tukeys test applied to the maximum values for multiple comparisons between materials.
Studied material Vitremer P-60 Ariston pHc
Thermocycling with without without with with without 0.1120 0.1145 0.6215 0.8960 0.9330 1.0260
There is no statistical difference between the groups linked by a vertical bar.
0.5725 mm and 0.3715 mm, with and without thermocycling, respectively; regarding maximum infiltration, the values were 0.8960 mm with thermocycling and 0.6215 mm without it, which points out the increase of microleakage when thermocycling was applied, although there was no statistically significant difference. These data corroborate the findings of ROSSOMANDO, WENDT JUNIOR23 (1995), who observed that, for composite resins, there is no statistically significant difference related to the utilization of thermocycling. The resin Ariston pHc, unlikely P-60 (Table 1) and maybe due to its specific properties, underwent an intermediate dislodgment in which thermocycling positively influenced its microleakage. It presented higher microleakage values than the other tested materials. When average microleakage measurements were considered, the values were 0.6440 mm and 0.7165 mm, with and without thermocycling, respectively. When maximum infiltration was taken into account, the values were 0.9330 mm and 1.0260 mm, with and without thermocycling, respectively. These results could be due to the fact that Ariston pHc presents a level of polymerization shrinkage similar to that of the new composite resins (2.2%) but it utilizes a single liner for dentinal sealing that could cause marginal fissures. However, FONTANA et al.8 (1999) and SCHIFFNER25 (1999), in studies on the efficacy of this material against secondary caries, are unanimous in stating that Ariston pHc has demonstrated the best performance in cavities with marginal fissures, suggesting that the existence of these fissures enhances its protective effect by producing an unpropitious environment for the development of S. mutans, through the pro280

claimed exchanges of ions. These exchanges (release of Ca++, F and OH ) are also underscored by other authors12,22. KIELBASSA et al.15 (1999), in a research carried out in situ, compared the release of fluorine by Ariston pHc, Dyract, Vitremer and Ketac-Molar. They concluded that only Ariston pHc presented a significant reduction of the prevalence of caries. The authors suggested that restoring materials that are addressed to prevent secondary caries should release both ions fluorine and hydroxyl. Considering the microleakage mean values (Table 2), the results of the 2-way ANOVA demonstrated the existence of a statistically significant difference, at the level of 5%, between the studied materials. However, the results demonstrated that there is no significant interaction (p = 0.11) nor statistically significant difference related to the submittal to thermocycling (p = 0.37). Based on these results, the Tukeys test for multiple comparisons was carried out considering all groups of the study, regardless of the submittal to thermocycling (Table 3). The results revealed statistically significant difference between the condensable resin P-60 and the semi-condensable resin Ariston pHc, which is in disagreement with the conclusions of BRAUN et al.1 (2000), who, in a six-month clinical survey, found out that there is no statistically significant difference between the marginal sealing of the condensable composite resin Solitaire and the semi-condensable composite resin Ariston pHc, although the methodologies of both studies were different. Considering the maximum microleakage values (Table 4) the results of the 2-way ANOVA revealed that, besides the statistically significant difference (at the level of 5%) between the tested materials, there is also a significant interaction between the groups, showing that thermocycling influenced the tested materials in different ways, although without statistic significance. Thus, to carry out the Tukeys test (Table 5) the groups were divided, separating the specimens that had or had not been submitted to thermocycling. However, among the tested materials, Vitremer was regarded as the one that allowed for the smallest dye penetration, regardless of thermocycling. However, when considering the resins P-60 and Ariston pHc, an interaction is verified, especially when thermocycling had been carried out. The results obtained in this research are in agreement with those obtained by DJOU et al.7

(1996), who stated that the maximum statistic infiltration parameter is the most suited comparative measure for clinical conditions, because even if it is small, when the significance level of 5% is applied, it is possible to see the interaction between materials. The results of this research revealed that none of the studied materials was able to totally prevent marginal microleakage, although there was a statistically significant difference between them. Vitremer presented the smallest microleakage, followed by the composite resins P-60 and Ariston pHc, which were similar to each other. Regarding thermocycling, in vitro studies on microleakage demonstrated that, in spite of influencing the materials in different ways, the procedure did not lead to statistical differences. As to the methods for the evaluation of microleakage, maximum infiltration seems to have a greater clinical value since it detects more precisely the extension of microleakage. Additionally, Ariston pHc, notwithstanding the
presented results, may be of some importance in pedodontics because, even if it does not completely seal the tooth-restoration interface eliminating microleakage, it is said to have preventive properties8,15,25 release of Ca++, F and OH which, according to reports, prevent or delay the development of secondary caries, maintaining a satisfactory oral environment. Nonetheless, more laboratorial and clinical evidences that prove the effectiveness of this material are necessary.

CONCLUSIONS

Based on these results, it is possible to conclude that all tested groups presented marginal microleakage. Vitremer presented the best results, followed by P-60 and Ariston pHc. There was no statistically significant difference related to thermocycling and, regarding the methods for evaluating microleakage, the method that employs values of maximum infiltration seems to be the best in detecting the extent of microleakage.
BIJELLA, M. F. B.; BIJELLA, M. F. T. B.; SILVA, S. M. B. da. Avaliao quantitativa in vitro da microinfiltrao marginal em restauraes classe II, confeccionadas com um cimento de ionmero de vidro e duas resinas compostas. Pesqui Odontol Bras, v. 15, n. 4, p. 277-282, out./dez. 2001. Avaliou-se in vitro a microinfiltrao marginal em restauraes classe II realizadas com Vitremer, com as resinas compostas Ariston pHc e P-60, com o propsito de verificar a influncia da ciclagem trmica para estes materiais, como tambm dois mtodos de anlise da penetrao do corante. Foram utilizados 60 pr-molares, divididos em 3 grupos, cujas cavidades proximais apresentavam parede cervical 1 mm abaixo da juno cemento-esmalte. Metade de cada grupo sofreu processo de termociclagem, enquanto a outra metade permaneceu em gua deionizada a 37C. Os espcimes foram imersos em soluo de fucsina bsica a 0,5% por 24 horas a 37C. Para anlise da microinfiltrao, os dentes foram seccionados no sentido msio-distal e a anlise realizada atravs do software Imagetools. Os resultados foram avaliados atravs do teste ANOVA 2-critrios e Tukey. Pelos resultados, todos os grupos apresentaram microinfiltrao marginal, sendo menores para o Vitremer, seguidos pela resina composta P-60 e por ltimo pela resina Ariston pHc. No houve diferena estatisticamente significante no uso ou no da termociclagem e o mtodo atravs da mxima infiltrao demonstrou ser o melhor para detectar a extenso da microinfiltrao. UNITERMOS: Infiltrao dentria; Resinas compostas; Cimentos de ionmero de vidro.