Shear bond strength of glass-ionomer cements to dentin: Effects of dentin depth and type of material activation

Resistência ao cisalhamento da união de cimentos de ionômero de vidro à dentina: Efeitos da profundidade do substrato e do tipo de ativação do material

Abstracts

The purpose of this study was to determine, through the shear bond strength of in vitro tests, that the type of glass-ionomer cements (conventional or hybrid) and dentin depth (superficial or deep) are factors that may influence the adhesion of these materials to the dentin structure. Specimens of two conventional glass-ionomer cements (Vidrion R® - SS White and Chelon Fil®- Espe) and a hybrid-glass ionomer cement (Vitremer® - 3M) were separated in groups and prepared for the shear bond strength test. The results submitted to statistical analysis were (all values are in MPa): Group I - Vidrion R - superficial dentin 1.97 (<FONT FACE="Symbol">±</FONT> 0.56); deep dentin 3.15 (<FONT FACE="Symbol">±</FONT> 1.51); Group II - Chelon Fil - superficial dentin 2.43 (<FONT FACE="Symbol">±</FONT> 1.43); deep dentin 3.21 (<FONT FACE="Symbol">±</FONT> 0.89); and Group III - Vitremer - superficial dentin 7.04 (<FONT FACE="Symbol">±</FONT> 2.04); deep dentin 10.30 (<FONT FACE="Symbol">±</FONT> 1.99). There were significant differences between dentin depth and type of materials

Shear bond strength; Glass ionomer cements; Superficial dentin; Deep dentin; Adhesion

A proposta deste trabalho foi determinar, através da resistência ao cisalhamento em testes in vitro, se o tipo de cimento de ionômero de vidro, convencional ou híbrido, e a profundidade de dentina, superficial ou profunda, são fatores que influenciam a adesão desses materiais na estrutura dentinária. Espécimes de dois cimentos convencionais (Vidrion R® - SSWhite e Chelon Fil®- Espe) e um cimento de ionômero de vidro híbrido (Vitremer®- 3M) foram divididos em grupos. Os resultados (todos os valores em MPa) submetidos à análise estatística foram: Grupo I - Vidrion R - dentina superficial, 1,97 (<FONT FACE="Symbol">±</FONT> 0,56); dentina profunda, 3,15 (<FONT FACE="Symbol">±</FONT> 1,51); Grupo II - Chelon Fil - dentina superficial, 2,43 (<FONT FACE="Symbol">±</FONT> 1,43); dentina profunda, 3,21 (<FONT FACE="Symbol">±</FONT> 0,89); e Grupo III - Vitremer - dentina superficial, 7,04 (<FONT FACE="Symbol">±</FONT> 2,04); dentina profunda, 10,30(<FONT FACE="Symbol">±</FONT> 1,99). Houve diferenças significantes entre a profundidade de dentina e o tipo de ativação do material

Resistência ao cisalhamento; Cimentos de ionômero de vidro; Dentina superficial; Dentina profunda; Adesão

SHEAR BOND STRENGTH OF GLASS-IONOMER CEMENTSTO DENTIN. EFFECTS OF DENTIN DEPTH ANDTYPE OF MATERIAL ACTIVATION

RESISTÊNCIA AO CISALHAMENTO DA UNIÃO DE CIMENTOS DE IONÔMERO DE VIDRO À DENTINA. EFEITOS DA PROFUNDIDADE DO SUBSTRATO E DO TIPO DE ATIVAÇÃO DO MATERIAL

Elda PISANESCHI^*

Rubens Corte Real de CARVALHO^**

Edmir MATSON^***

PISANESCHI, E. et al. Shear bond strength of glass-ionomer cements to dentin. Effects of dentin depth and type of material activation. Rev Odontol Univ São Paulo, v.11, p.1-7, 1997. Suplemento.

The purpose of this study was to determine, through the shear bond strength of in vitro tests, that the type of glass-ionomer cements (conventional or hybrid) and dentin depth (superficial or deep) are factors that may influence the adhesion of these materials to the dentin structure. Specimens of two conventional glass-ionomer cements (Vidrion R® - SS White and Chelon Fil®- Espe) and a hybrid-glass ionomer cement (Vitremer® - 3M) were separated in groups and prepared for the shear bond strength test. The results submitted to statistical analysis were (all values are in MPa): Group I - Vidrion R - superficial dentin 1.97 (±0.56); deep dentin 3.15 (±1.51); Group II - Chelon Fil - superficial dentin 2.43 (±1.43); deep dentin 3.21 (±0.89); and Group III - Vitremer - superficial dentin 7.04 (±2.04); deep dentin 10.30 (±1.99). There were significant differences between dentin depth and type of materials.

UNITERMS: Shear bond strength; Glass ionomer cements; Superficial dentin; Deep dentin; Adhesion.

INTRODUCTION

Since the advent of adhesive dentistry (BUONOCORE², 1955), one of the major goals in restorative dentistry has been to find an adhesive material to both enamel and dentin.

In 1968, SMITH¹⁸ devised zinc polycarboxilate cement, in which major properties are adhesion to dental structure and biocompatibility.

In 1972, WILSON; KENT²¹, in an attempt to improve the properties of carboxilate cements and associate them to the beneficial properties of silicate cements, proposed a new material, glass-ionomer cement. This material has been well accepted and some of its main properties are: adhesion to dental structure and metals, fluoride release, biocompatibility and a linear coefficient of thermal expansion similar to that of the dental structure (NAVARRO¹¹, 1994).

Since it was introduced, this material has undergone several formula changes, in order to make it more suitable for clinical use and to improve its physical and mechanical properties. In 1989, MATHIS; FERRACANE⁹ added a resin portion to the original material, which yielded a hybrid material with significant improvement in its properties.

The early hybrid ionomers were indicated for pulpal protection, with 10% of a resin compound in a liquid phase, called HEMA, and are now indicated as restorative materials, in which the resin compound content is over 20% (NAVARRO¹¹, 1994).

The adhesion of these materials to mineralized tissues is made basically through the bonding of Ca ions with the resulting adhesion to enamel and is superior to that of dentin. Dentin presents moisture resulting from its permeability to pulpal fluids, mainly deep dentin, and this is one of the reasons to explain the poor adhesion of resin adhesive systems to deep dentin. Glass-ionomer cements are less sensitive to dentin moisture because they are hydrophilic and seem to tolerate moisture better than the resin systems (CARVALHO³, 1995).

The purpose of this study was to test the shear bond strength of two conventional restorative glass-ionomer cements: Vidrion R and Chelon Fil, and a hybrid restorative glass-ionomer cement: Vitremer, to superficial and deep dentin.

MATERIALS AND METHODS

Forty-eight caries-free, recently-extracted human teeth (upper and lower molars and bicuspids) kept in saline were used in this study.

The teeth were embedded on a PVC tube with autopolymerizing resin. They were X-rayed to guide the cuts according to dentin depth. They were transversally cut in a plaster cutter under refrigeration at two depths: superficial dentin - 0.5mm beyond the enamel-dentin interface, and deep dentin - 1.0mm above the pulpal horns (Figure 1).

FIGURE 1
- Dentin depths. A: Superficial dentin surface. B: Deep dentin surface.

The dentin surface was subjected to sequential treatment with 280, 400 and 600 grit wet silicon carbide paper and then cleaned with pumice and water. Then the specimens were subjected to the treatment indicated by the respective manufacturer prior to the application of each material. The groups and materials utilized in the study are listed in Table 1.

Groups Material manufacturer SubstrateNumberof teeth IVidrion R (SSWhite)Superficial8Deep8IIChelon Fil (ESPE)Superficial8Deep8IIIVitremer(3M)Superficial8Deep8

Groups	Material manufacturer	Substrate	Numberof teeth
I	Vidrion R (SSWhite)	Superficial	8
		Deep	8
II	Chelon Fil (ESPE)	Superficial	8
		Deep	8
III	Vitremer(3M)	Superficial	8
		Deep	8

TABLE 1 - Groups used in the study.

A split-teflon matrix, held in place by a split-metal holder was adapted to the teeth crowns (Figures 2, 3 and 4). This device produced a bonded test specimen of 3.5mm in diameter and 5.0mm in height.

FIGURE 2
- Knife-edge shaped rod applied to the test specimen.

FIGURE 3 - Metallic/teflon matrix
FIGURE 4 - PVC-tube-mounted matrix set.

The materials were utilized according to the manufacturers' instructions.

In the case of Vidrion R, surface cleaning was carried out with 25% polyacrylic acid during 30seconds, then washed and dried. The material was proportioned in v/v and mixed, inserted into the matrix fixed to the tooth by means of a Centrix syringe (Centrix Inc. - DFL Ind. - Com.), covered with a polyester matrix for 10minutes and protected by a layer of varnish (Vidrion V - SSWhite).

For Chelon Fil, surface cleaning was carried out with Espe Ketac Conditioner, 25% polyacrylic acid for 10seconds, then washed and dried. The material was proportioned in v/v and mixed, inserted into the matrix fixed to the tooth by means of a Centrix syringe (Centrix Inc. - DFL Ind. - Com.), covered with a polyester matrix for 10 minutes and protected by a layer of varnish (Vidrion V - SSWhite).

For Vitremer, the surface primer which accompanies the product was applied for 30seconds, air-dried and light-cured for 20seconds. The material was proportioned in v/v, mixed and inserted into the matrix in two portions with the aid of a probe and an amalgam condenser, light-cured for 40 seconds each, the second portion being covered with a polyester matrix.

All materials were left to rest for 5 minutes after the removal of the polyester matrix prior to being returned to the saline storage solution.

After a variable time the test specimens were thermocycled in a cycling machine for 500 cycles of 30seconds each at a temperature of 5ºC and 55ºC. They were stored for one week in distilled water at 37ºC before being subjected to the shear test in an Otto Wolpert-Werke testing machine at a crosshead speed of 0.5mm/min. The shearing load was applied by means of a knife-edge shaped rod perpendicular to the test specimen axis, near the interface between the latter and the dentin (Figure5). Upon each fracture of the test specimen the results in kgf were recorded, transformed into MPa and subjected to two-way ANOVA and Tukey statistical tests.

FIGURE 5 - Test specimens - Side view

RESULTS AND DISCUSSION

The results obtained involved 48 measurements expressed in MPa, divided into 3 groups: Group I - Vidrion R (superficial and deep dentin); Group II - Chelon Fil (superficial and deep dentin); and GroupIII - Vitremer (superficial and deep dentin). The mean values and respective standard deviations for each material according to dentin depth are expressed in Table2.

Material SubstrateSuperficial (N=8) Deep (N=8) G III - Vitremer7.04±2.0410.30±1.99G II - Chelon Fil2.43±1.433.21±0.89G I - Vidrion R1.97 ± 0.563.15±1.51

Material Substrate	Superficial (N=8)	Deep (N=8)
G III - Vitremer	7.04±2.04	10.30±1.99
G II - Chelon Fil	2.43±1.43	3.21±0.89
G I - Vidrion R	1.97 ± 0.56	3.15±1.51

TABLE 2 - Means and standard deviations for cements (MPa).

Table 3 shows the variance analysis of original values.

Variation sourceSum of squaresD. F.Mean squares(F)Prob. (H0)Between materials382.08642191.043284.080.001%***Between depth36.1747136.174715.920.048%**Materials/depth interaction14.112227.05613.115.381% nsResidue95.4316422.2722 Total variation527.804947

Variation source	Sum of squares	D. F.	Mean squares	(F)	Prob. (H0)
Between materials	382.0864	2	191.0432	84.08	0.001%***
Between depth	36.1747	1	36.1747	15.92	0.048%**
Materials/depth interaction	14.1122	2	7.0561	3.11	5.381% ns
Residue	95.4316	42	2.2722
Total variation	527.8049	47

TABLE 3 - Variance analysis - original values.

** - 1% significance level.

*** - 0.1% significance level.

ns - non-significant.

In order to analyze whether the materials were different from one another or not, the Tukey test at 1% was applied, as illustrated in Table 4, with the respective means obtained by the materials; Group III presented greater shear strength than Groups I and II [G III, 8.67>(G II, 2.82 = G I, 2.56)].

Variation factor: materialMaterialsMeans (MPa)Tukey (1%)G I - Vidrion R2.56 (±1.26) *2.33G II - Chelon Fil2.82 (±1.23) *G III - Vitremer8.67 (±2.57) u

Variation factor: material
Materials	Means (MPa)	Tukey (1%)
G I - Vidrion R	2.56 (±1.26) *	2.33
G II - Chelon Fil	2.82 (±1.23) *
G III - Vitremer	8.67 (±2.57) u

TABLE 4 - Calculated sampling means: original values.

Different signs identify significant averages (p<0.1).

Substrate depthMean values (S.D.)Deep dentin5.55 (±3.73) uSuperficial dentin3.82 (±2.73) X

Substrate depth	Mean values (S.D.)
Deep dentin	5.55 (±3.73) u
Superficial dentin	3.82 (±2.73) X

TABLE 5 - Mean values of different depths (MPa).

Different signs identify significant averages (p<0.1).

The observation that the light-cured material (Vitremer) presented higher shear bond strength than conventional materials (Vidrion R and Chelon Fil) is in agreement with most papers published. MATHIS; FERRACANE⁹ consider that the enhanced mechanical properties are due to the fact that the resin acts as a reinforcing agent, resulting in significantly higher initial properties, fracture resistance during desiccation and decreased solubility (McLEAN¹⁰, 1994; ERICKSON; GLASSPOOLE⁵, 1994; BELL; BARKMEIER¹, 1994; SIDHU; WATSON¹⁷, 1995).

Since the adhesion of such cements to dental tissues is a result of ionic interaction, several surface treatments have been suggested, such as high-molecular-weight substances which act by cleaning the substrate, thereby not altering dentin characteristics (POWIS¹³, 1982; PRATI¹⁴, 1990).

Treatment utilized for the cements was that indicated by the manufacturers; for conventional cements, we used 25% polyacrylic acid, and for the hybrid cement we utilized the primer, which comes with the product and seems to have given better surface wettability, resulting in higher values of bond strength as observed in other studies (STATMILLER; BURGESS¹⁹, 1994; TRIANA et al.²⁰, 1994; SCOTT¹⁶, 1995).

Still using the calculated sampling means, in their original values, we observed that there were differences between the two substrate depths, as demonstrated in Table5.

There was a statistically significant difference between substrate depths, since the highest shear bond strength values were found in deep dentin, both for conventional and hybrid materials. This finding differs from most studies found in the literature, where adhesion is always greater in superficial dentin (PRATI et al.¹⁵, 1991; PASHLEY¹², 1993; FRIEDL et al.⁶, 1994; FRIEDL et al.⁷, 1995).

This greater adhesion in deep dentin may suggest that the materials showed greater penetration in dentin where dentin tubules are more numerous and larger in diameter (deep dentin) (PRATI et al.¹⁵, 1991), thus favoring a micromechanical retention which may occur with the penetration of glass ionomer cements into the tubules (ERICKSON; GLASSPOOLE⁵, 1994).

An extensive work by LIN et al.⁸ (1992) involving scanning electron microscopy (SEM), confocal microscopy, X-ray photoelectron microscopy (XPS) and secondary ion mass spectrometry (SIMS) has shown strong evidence of ion exchange and penetration of glass-ionomer compounds into dentin structure. The authors suggested that hybrid, light-cured glass-ionomer cements present stronger bond strength to dentin due mainly to higher cohesive strength and possible micromechanical retention to the substrate.

From this point of view, as seen in the study by PRATI et al.¹⁵ (1991), tubules in deep dentin present a larger diameter, with the possibility of the material penetrating into these tubules, resulting in micromechanical retention, which may explain the better results obtained with deep dentin in this study.

The recent study by CARVALHO et al.⁴ (1995) investigated the hypothesis of a new light-activated cement (Variglass) developing micromechanical retention by forming a hybrid layer on the acid-etched dentin. They observed the formation of a hybrid layer similar to that occurring with adhesive resins suggesting the presence of micromechanical retention. ERICKSON; GLASSPOOLE⁵ (1994) have also shown a hybrid-like layer formed at the interface between Vitremer and dentin.

The study by CARVALHO et al.⁴ (1995), together with those by LIN et al.⁸ (1992) and ERICKSON; GLASSPOLE⁵ (1994), may serve as the underpinning for the results obtained in this research.

Based on what has been discussed, superiority of the light-activated glass ionomer in terms of its shear bond strength is evident when compared with that of conventional cements. This finding is supported by existing literature.

As to substrate depth, we observe that the results of this study differ from those of most other research. However, it is premature to close the discussion by considering only the results obtained here. Further morphological studies of the interface between light-activated glass-ionomer cements and dentin are indicated to elucidate their bonding mechanisms.

Although there was no statistical difference in interaction materials versus depth, we provide Graph 1.

GRAPH 1 - Interaction materials versus depht

When analysing the graph we can see the higher performance of Vitremer in relation to the other materials (Chelon Fil and Vidrion R), which confirms what was already shown. The slops demonstrated the increase in bond strength in deep dentin for the three materials.

CONCLUSIONS

Based on the methodology employed in this study and the analysis of the results obtained, we were able to conclude that:

1. There was a statistically significant difference in shear bond strength between the materials tested, with higher values for the light-activated material (Vitremer) versus the chemically-activated materials (Vidrion R and Chelon Fil).

2. There was a statistically significant difference in shear bond strength between the values in the two substrates studied, with higher results obtained in deep dentin for the three materials tested.

3. There was no statistically significant difference in shear bond strength between the two chemically-activated materials, both in deep and superficial dentin.

ACKNOWLEDGMENTS

We thank the members of Dental Materials Laboratory at USP and the members of the Dentistry Laboratory at PUCC University. We also thank 3M Company and SSWhite for the material provided.

PISANESCHI, E. et al. Resistência ao cisalhamento da união de cimentos de ionômero de vidro à dentina: efeitos da profundidade do substrato e do tipo de ativação do material. Rev Odontol Univ São Paulo, v.11, p 1-7, 1997. Suplemento.

A proposta deste trabalho foi determinar, através da resistência ao cisalhamento em testes in vitro, se o tipo de cimento de ionômero de vidro, convencional ou híbrido, e a profundidade de dentina, superficial ou profunda, são fatores que influenciam a adesão desses materiais na estrutura dentinária. Espécimes de dois cimentos convencionais (Vidrion R® - SSWhite e Chelon Fil®- Espe) e um cimento de ionômero de vidro híbrido (Vitremer®- 3M) foram divididos em grupos. Os resultados (todos os valores em MPa) submetidos à análise estatística foram: Grupo I - Vidrion R - dentina superficial, 1,97 (±0,56); dentina profunda, 3,15 (±1,51); Grupo II - Chelon Fil - dentina superficial, 2,43 (±1,43); dentina profunda, 3,21 (±0,89); e Grupo III - Vitremer - dentina superficial, 7,04 (±2,04); dentina profunda, 10,30(±1,99). Houve diferenças significantes entre a profundidade de dentina e o tipo de ativação do material.

UNITERMOS: Resistência ao cisalhamento; Cimentos de ionômero de vidro; Dentina superficial; Dentina profunda; Adesão.

REFERENCES

1. BELL, R. B.; BARKMEIER, W. W. Glass ionomer restorative and liners shear bond strength to dentin.

   J Esthet Dent, v.6, n.3, p.129-134, 1994.

2. BUONOCORE, M. G. A simple method of increasing the adhesion of acrylic filling materials to enamel surfaces.

   J Dent Res, v.34, p.849-853, 1955.

3. CARVALHO, R. M. Ionômero de vidro.

   Maxi Odonto: dentística, v.1, n.5, p.1-10, set./out. 1995.

4. CARVALHO, R. M. et al. Bonding mechanism of Variglass to dentin.

   Am J Dent, v.8, n.5, p.253-258, Oct. 1995.

5. ERICKSON, R. L.; GLASSPOOLE, E. A. Bonding to tooth structure: a comparison of glass-ionomer and composite-resin systems.

   J Esthet Dent, v.6, n.5, p.227-244, 1994.

6. FRIEDL, K. H.; POWERS, J. M. Bond strength of ionomers affected by dentin depth and moisture. In: INTERNATIONAL ASSOCIATION FOR DENTAL RESEARCH. General Session & Exhibition, 72. Seattle, Mar. 10-13, 1994. Abstracts of papers.

   J Dent Res, v.73, p.183, 1994. [Resumo n.653].

7. FRIEDL, K. H. et al. Influence of different factors on bond strength of hybrid ionomers.

   Operat Dent, v.20, n.2, p.74-80, Mar./Apr. 1995.

8. LIN, A. et al. Studies on the adhesion of glass-ionomer cements to dentin.

   J Dent Res, v.71, n.11, p.1836- 1841, Nov. 1992.

9. MATHIS, R. S.; FERRACANE, J. L. Properties of a glass ionomer/resin-composite hybrid material.

   Dent Mater, v.5, p.355-358, 1989.

10. McLEAN, J. W. Evolution of glass-ionomer cements. A personal view.

    J Esthet Dent, v.6, n.5, p.195-206, 1994.

11. NAVARRO, M. F. L. et al.

    O que é preciso saber a respeito do ionômero de vidro? Inovações, vantagens e desvantagens. In: FELLER, C.; BOTTINO, M. A., coord. Atualização na clínica odontológica: a prática da clínica geral. São Paulo:Artes Médicas, 1994. p.61-74.

12. PASHLEY, E. L. et al. Bond strengths to superficial intermediate and deep dentin in vivo with four dentin bonding systems.

    Dent Mater, v.9, p.19-22, Jan. 1993.

13. POWIS, D. R. et al. Improved adhesion of a glass ionomer cement to dentin and enamel.

    J Dent Res, v.61, n.12, p.1416-1422, 1982.

14. PRATI, C. et al. Cementi vetro ionomerici e pretrattamenti dentinali valutazione della adesione alla dentina.

    Minerva Stomatol, v.39, n.2, p.145-148, 1990.

15. PRATI, C. et al. Hydrostatic intrapulpal pressure and bond strength of bonding systems.

    Dent Mater, v.7, n.1, p.54-58, Jan. 1991.

16. SCOTT, K. et al. Shear bond strength of glass ionomers to etched and unetched enamel. In: INTERNATIONAL ASSOCIATION FOR DENTAL RESEARCH. General Session & Exhibition, 73. San Antonio, Mar. 8-12, 1995. Abstracts of papers.

    J Dent Res, v.74, p.106, 1995. [Resumo n.757].

17. SIDHU, S. K.; WATSON, T. F. Resin-modified glass ionomer materials - A status report for the American Journal of Dentistry.

    Am J Dent, v.8, n.1, p.59-67, Feb. 1995.

18. SMITH, D. C. A new translucent cement.

    Br Dent J, v.125, p.381-384, 1968.

19. STATMILLER, S. P.; BURGESS, J. O. Shear bond strength of two glass ionomers to contaminated dentin. In: INTERNATIONAL ASSOCIATION FOR DENTAL RESEARCH. General Session & Exhibition, 72. Seattle, Mar. 10-13, 1994. Abstracts of papers.

    J Dent Res, v.73, p.328, 1994. [Resumo n.1814].

20. TRIANA, R. et al. Shear bond strength to dentin of reinforced glass-ionomer. In: INTERNATIONAL ASSOCIATION FOR DENTAL RESEARCH. General Session & Exhibition, 72. Seattle, Mar. 10-13, 1994. Abstracts of papers.

    J Dent Res, v.73, p.328, 1994. [Resumo n.1808].

21. WILSON, A. D.; KENT, B. E. A new translucent cement for dentistry - The glass ionomer cement.

    Br Dent J, v.132, p.133-135, 1972.

Recebido para publicação em 16/12/96

Aceito para publicação em 04/08/97

^* Assistant Professor of the Restorative Dentistry Department, PUC University, Campinas.

Assistant Professor of the Restorative Dentistry Department, PUC University, Campinas.

^** Assistant Professor of the Restorative Dentistry Department, School of Dentistry, São Paulo University.

^*** Dean of the School of Dentistry of São Paulo University.

Publication Dates

• Publication in this collection
  28 Jan 2000
• Date of issue
  1997

History

• Received
  16 Dec 1996
• Accepted
  04 Aug 1997