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ISSN (Print) 1013-9052
EISSN 1658-3558
The Saudi Dental Journal,
P.O. Box 52500,
Riyadh 11563,
Kingdom of Saudi Arabia
P.O. Box 52500,
Riyadh 11563,
Kingdom of Saudi Arabia
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Influence of several materials on the bond strength of glass polyalkenoate to dentin
Khalid A. Al Wazzar *, BDS, MSc
Glass ionomer
(Gl) is a restorative that bonds to dentin by molecular adhesion. During a
dental treatment, several adjunctive materials such as temporary fillings,
cements and intracanal medicaments may be used prior to the placement of Gl
which might adversely influence its adhesion to dentin. The purpose of this
study was to determine the influence of using eugenol containing and eugenol
free zinc oxide temporary cements, calcium hydroxide and iodine potassium
iodide intracanal medicaments, and Epoxy resin sealers on the adhesion of
Ketac-Silver Aplicap, to dentin. Sixty dentin specimens were prepared and
divided to six groups. Each of the five groups was treated with one of the
adjunctive materials for one week. The adjunctive material was removed and
dentin cleaned with pumice-water slurry, etched, rinsed thoroughly and dried
with air. Ketac-silver short cylinders were formed on the dentin between two
sliding surface; a specially designed testing apparatus. The two sliding
surfaces were pulled apart using a testing machine and the debonding force was
recorded. One-way analysis of variance and Tukey's multiple range test were
used to analyze the data. While the debonding force was 2.2MPa for the control,
it was 2.03,2.09,2.00, and 2.16 MPa for specimens subjected to four of the
adjunctive materials and there were no statistically significant differences (P
< 0.05). The only adjunctive material that caused significant difference in
the bond strength between Ketac-Silver and dentin (an improvement) was epoxy
resin sealer (AH-26) yielding a debonding value of 3.50
Mpa.
Glass polyalkenoate (ionomer) cements,
introduced by Wilson and Kent,1 are water based. They are derivatives of
silicate and zinc polycarboxylate cements consisting of ion-leachable glass
powder and polyalkeonic acid. The result of the interaction between the two
constituents is a hard cement composed of glass particles surrounded and
supported by a matrix arising from the dissolution of the surface of the glass
particles in the acid.
Chemical bonding between glass polyalkenoate cements and dentin or enamel has been well documented.2 The cements are also reported to adhere to a number of other substrates such as stainless steel, tin, tin-oxide plated platinum or gold but not to porcelain, pure platinum or pure gold.3 Nonetheless, a glass polyalkeonate luting cement enhanced the retention of gold alloy castings when compared with traditional luting cements.4 In addition to chemical bonding of glass polyalkenoate cements to cavity walls, the continuity of such bonding is assured. The bond between glass polyalkeonate and tooth material is a dynamic one with adhesive bonds being continually broken and reformed as chemical (ion-exchange and water transfer) and biological changes take place.5 Other advantages of glass polyalkenoate materials is the release of fluoride6 which leaches into the tooth structure interfacing the restoration,7 inhibiting recurrent caries,8 and aiding remineralization.9 The materials also have low thermal conductivity and a coefficient of thermal expansion similar to that of tooth structure.10 Glass polyalkenoates, because of their adhesive characteristics and other advantages have gained wide use in dental practice. The materials are primarily used as a permanent cement, as a base band as a class V filling material. They are also used to build cores, to seal occlusal fissures and as endodontic sealers.10 Any of these dental procedures usually requires the use of other materials prior to using the glass polyalkeonate. The influence of these other materials on the adhesive potential of the glass polyalkeonate to dentin needs to be studied. The bonding potential of dental adhesive materials to enamel and dentin is quite sensitive to the prior management of the tooth surface. The effect of several materials on the bond strength of resin composite to dentin had been well studied as reported in the literature. Summitt et al11 studied the effect of air/water rinse versus water only and rinsing times on resin to etched-enamel bond strength. Gwinnett12 studied strength of bonding of composite resin to dentin after air drying and re-wetting. Macchi et al13 studied the influence of several endodontic materials on the bonding of composite resin to dentin. The influence of saliva, plasma, zinc oxide-eugenol cement, non-eugenol zinc oxide cement and handpiece lubricant on bonding composite resin to dentin was studied by Powers et al.14 Tam and Pilliar15 studied the influence of conditioning acid when air dried on the bond strength of dentin-composite resin adhesive interface. The effect of etchant type, surface moisture, and resin composite type on the shear bond strength of three dentin adhesives was studied by Perdigao et al.16 The influence of eugenol in reducing the bond strength between composite resin and dentin is reported. 13,17,18 In as much as enamel and dentin surface treatment influences their adhesion to composite resins, it is likely to influence their adhesion to glass-ionomer cements. Studies to substantiate or vitiate this conclusion are sparse. Capurro et al19 found that IRM, Grossman Cement, Dycal and Cavit had no effect on the bonding of glass ionomer cement to dentin. The purpose of this study was to determine the influence of five materials including temporary cements, intracanal medicaments and sealer cement materials on the bond strength of Ketac-Silver (a glass-ionomer restorative) to dentin.
A glass polyalkeonate material with proven chemical adhesion to
dentin, used for core buildup, was selected for this study (Ketac-Silver
Aplicap ESPE Premiere, Norristown,
PA, USA).
Five materials were used as potential contaminants that may interfere with the
glass-ionomer's adhesion to dentin. These were: eugenol-free zinc oxide
temporary cement (Temp-Bond NE, Kerr, Romulus, Ml, USA), eugenol containing
temporary cement (Temp-Bond, Kerr); a calcium hydroxide [Ca(OH)2] paste packed in anesthesia cartridges (Calasept, Scania Dental
AB, Knivsta, Sweden); biphenol A- diglycidylether based root canal sealing and
filling material, an epoxy resin (AH-26, Dentsply Detrey, Konstanz, Germany);
and a laboratory prepared 2% Iodine Potassium Iodide (IPI) solution, commonly
used as an intracanal medicament.20
Fabrication of test specimens A previously used apparatus to prepare testing specimens was used.18 Each specimen consisted of parts A and B. The configuration of each specimen is illustrated in Fig. 1. The A portion of the specimen was fabricated by embedding a freshly extracted human permanent molar tooth into acrylic resin (Orthoresin; De Trey Dentsply S.A., Bois Coiombes, France), which was then sectioned to a disc 33 mm in diameter and 5 mm thick. Both sides of each disc were flattened. The solid caries-free dentinal surface of the embedded tooth was exposed in one side of the disc. Specimen sectioning and flattening were accomplished by using a fine diamond disc (Brasseler GmbH, Lemgo, Germany). An opening, 5 mm in diameter, was placed in the acrylic to facilitate mounting on the testing machine (Fig. 2). The second component (part B) of each specimen was fabricated based on the testing apparatus designed by Hammad et al21,22 Only the B portion of Hammad's testing device was used in this study. It was fabricated by machining sheets of solid Delrin (Almac Plastics, Minneapolis, MN) acrylic resin to conform precisely to the diagram depicted in Fig. 1. Part B was cast in a base-metal alloy (Wirron 99, Bego, Germany) following the manufacturer's instructions. Part B served as a matrix to hold the Ketac-Silver in position during bonding procedures and provided a means of attaching the specimen to the debonding device (Figs. 2 and 3). Specimen preparation and material application Sixty specimens (part A) were fabricated and divided randomly into six groups of 10 each. The teeth in group 1 received no contaminant and served as a control. In groups 2, 3, 4, 5 and 6, the dentin was coated with Temp-Bond NE, Temp-Bond, IPI, AH-26, or Ca (OH)2, respectively. Manufacturer's instructions were followed carefully. After contaminant application and setting, the specimens were stored in 100% humidity at 37°C for 1 week. Following storage, contaminants were removed from the dentin, except for the IPI group, using a Hollenback carving instrument. The exposed dentin surfaces of all six groups were cleaned with pumice-water slurry and a prophylaxis rubber cup mounted on a slow-speed handpiece. Specimens were then rinsed thoroughly with distilled water and dried with air. ESPE Ketac conditioner was then applied over the dentin surface for 10 seconds then thoroughly rinsed with distilled water for 30 seconds and dried with air. The matrix of each specimen (part B) was aligned over the dentin surface of its corresponding part A and then filled with Ketac-Silver Aplicap core material using the syringe procedure (Fig. 3). The core material was used according to the manufacturer's recommendation and applied to all groups. Specimens were left undisturbed until complete setting was attained. The specimens were allowed to set according to the manufacturer's instructions. All specimens were fabricated by one investigator. Method of testing The longitudinal ends of parts A and B of each specimen were mounted by means of hooks attached to the upper and lower jaws of a universal testing of an Accuforce Elite test machine (Model E500, Ametek, Largo, FL, USA). Force was applied at a crosshead speed of 0.05 in/min until failure occurred (Fig. 4). The presence of two flexible joints, coupled with the slow loading, permitted the specimen to align itself to a uniaxial direction during testing procedures. However, because the bonding interface was not aligned at the middle of the thickness of each specimen, forces were not primarily directed at the dentin-core material interface, and thus forces were directed diagonally. This developed a combination of shear and tensile stresses to simulate complex clinical stress situations. All testings were performed by one investigator. The data obtained were analyzed statistically using a one-way ANOVA and Tukey's post hoc test.
The bond strength results for the five experimental groups and the
control are shown in Table 1. The table suggests that except for AH26, the use
of the four other materials caused little change in the adhesion of
Ketac-Silver to dentin.
Before selecting the proper statistical tests, it was necessary to test the homogeneity of the variances obtained with the various groups. Homogeneity of variance test was significant; however, not significant enough to preclude using a parametric one way analysis of variance (ANOVA). The results of parametric one-way ANOVA is depicted in Table 2. The test showed highly significant differences between groups at (P<0.001) Due to the mild significance of the variance homogeneity test, it was felt necessary to also use non-parametric ANOVA. The results of non-parametric ANOVA, also showed highly significant differences between the groups at (P < 0.001). Tukey's post hoc test showed that the bond strength of Ketac-silver to dentin treated by AH-26 was significantly higher than that for dentin treated with all other materials and than that for untreated dentin (the control) as illustrated in Table 1.
In the present study, the contaminants applied to dentin were kept
on it for one week and then removed by carving followed by pumice-water slurry
and thoroughly rinsed with water. This procedure did not achieve the
decontaminated dentin surface which could have facilitated adherence of resin
composite to dentin. 13,14,18 Accordingly, one may safely
conclude that traces of these contaminants did remain on the dentin surfaces.
As Table 1 shows, four of the contaminants had no effect on the strength of the
bond between the glass-ionomer and dentin suggesting that the glass-ionomer
liquid, a polyacrylic acid, dissolved away the traces of the contaminants thus
eliminating their effect in reducing the bond strength. Similar finding was
reported by Capurro et al.19 Further, when three polyacrylic acid etchants
were used, the bond strength between glass-ionomer cement and dentin was
increased23 emphasizing the etching and
thorough cleaning ability of the polyacrylic acid.
On the other hand, the use of AH-26, an epoxy resin, as a contaminant caused an unexpected increase in the bond strength between the glass-ionomer cement and the dentin (Table 1). This increase suggests that the traces of AH-26 remaining on the specimens of this study after cleaning were not dissolved by the polyacrylic acid of the glass-ionomer cement. This explanation is quite reasonable when one considers that AH-26 was found to be extremely difficult to dissolve except with chloroform applied for more than 30 minutes.24 The presence of these traces of AH-26 increased the bond strength between the dentin and the glass ionomer cement. This increase suggests that AH-26 attaches to dentin with more strength than does the glass-ionomer. Other studies showed that canal sealed with AH-26 leaks less than those sealed with Ketac-endo (a glass-ionomer) suggesting that AH-26 attaches to the dentin even stronger than to the glass ionomer.25 Our data suggests that remnants of most contaminants used on dentin before using a glass-ionomer cement are not likely to influence its bonding to dentin, since the liquid of the cement dissolves them away. However, remnants of AH-26 are not dissolved by the liquid of the glass-ionomer and their presence enhance the glass-ionomer cement bond to dentin.
The authors wish to express their appreciation to Dr. Nazeer Khan
for performing the necessary statistics and analysis. This paper was presented
during the 11th Saudi International Dental Meeting
(Feb.26-March02,2000).
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