omparison of the shear bond strength composite resin material with dentinal glass ionomer cements rett Barry South
I. Cohen, PhD,a Lee Musikant, Hackensack,
of a titanium bonding agents
This study compared the in vitro shear bond strength of an autopolymerizing composite resin system (CR) (Ti-Core) with two third-generation dentinal bonding agents (DBA) (Tenure and Scotchbond 2) to glass ionomer cements (GIC) (RetacSilver, GC Miracle Mix, and Ketac-Cem). The experiment was divided in five groups. The shear bond strengths were evaluated on a universal testing apparatus at three different intervals; 15 minutes, 24 hours, and 7 days. Statistically, (twoway analysis of variance), the shear bond strengths from the greatest to least were: Ti-Core CR with Tenure DBA > Ti-Core CR with Scotchbond 2 DBA > Ketac-Silver GIC, GC Miracle Mix GIC > Ketac-Cem GIC. There were no differences in shear bond strengths according to time, and no interactions between groups and time. The shear bond strengths for Tenure DBA with Ti-Core CR were two and a half to three times greater than the silver-filled glass ionomers, KetacSilver GIC and GC Miracle Mix GIC. Tenure DBA with Ti-Core CR also had consistently greater shear bond strengths than Scotchbond 2 DBA with Ti-Core CR, and this trend is in agreement with similar research. (J PROSTHET DENT 1992;68:904-9.)
plethora of dental materials are presently available for the core buildup of teeth, but there have been no direct comparisons of the shear bond strengths for these materials bonded to dentin. Former studies have measured bond strengths of only one category and compared composite resin bonding systems, or they have merely reviewed various glass ionomer systems.1-7 This study compared the in vitro shear bond strengths of an autopolymerizing titanium-reinforced composite resin, bonded to dentin with two different third-generation dentinal bonding systems versus three different formulations of glass ionomer cements (GIC) to pretreated dentin. This study also measured the shear bond strengths at three different time intervals: 15 minutes, 24 hours, and seven days. The third-generation dentinal bonding systems included Scotchbond 2 dentin bonding system (3M Dental Products Division, St. Paul, Minn.). Scotchbond 2 dentin bonding agent (DBA) consists of an aqueous solution of maleic acid and hydroxyethyl methacrylate (HEMA). This solution is applied to alter the smear layer and encourages chemical adhesion to the subsequent composite resin application” After treatment of the smear layer, Scotchbond 2 light-cured dental adhesive is then applied to the dentinal surface. This adhesive con-
Tice President of Dental Research, Essential Dental Laboratories. bClinical Instructor, New York University. CCo-Director of Dental Research, Essential Dental Laboratories. lo/1139413
tains HEMA and Bis-GMA monomers with a photosensitive peroxide as the chemical initiation system.8 The modified Tenure (Z-step) solution dentin bonding system (Den-Mat Corp., Santa Maria, Calif.) is a dentinal conditioner that contains a solution of aluminum oxalate, an “A” acetone solution of the adduct of N (p-tolyl-glycine) and glycidyl methacrylate (NTG-GMA) and a “B” acetone solution of the adduct of pyromellitic acid dianhydride and 2-hydroxyethyl methacrylate (PMDM). The last application consists of Visar Seal (Den-Mat Corp.) light-cured unfilled composite resin.g Ti-Core CR (Essential Dental Systems, Inc., So. Hackensack, N.J.) is a new hybrid autopolymerizing composite resin (Bis-GMA based) reinforced with titanium. The addition of titanium was to improve the compressive and diametral tensile strength of the composite resin to make it comparable to dentin. lo This system also includes a peroxide and an amine chemical initiation system. Ketac-Silver GIC (ESPE-Premier, Norristown, Penn.) and GC Miracle Mix GIC (GC Dental Industrial Corp., Tokyo, Japan) are classified as glass ionomer cement restorations with silver particles added to the cement matrix for improving the mechanical properties and facilitating handling characteristics. Ketac-Silver GIC is composed of ceramic particles sintered with silver whereas GC Miracle Mix GIC contains amalgam alloy (silver) particles without a chemical interaction to the ionomer matrix.li Ketac-Cem GIC is an anhydrous GIC with poly(maleic acid) instead of poly(acrylic acid). I2 This study compared the shear bond strength of a composite resin core material used with dentinal bonding DECEMBER
Table I. Manufacturers, products and batch numbers used in this study Manufacturer Dentin
Den-Mat Corporation Tenure solution Dentin Bonding System 3M Dental Products Scotchbond 2 dentin bonding system Core materials and cements EssentialDental Ti-Core composite resin Systems core material EWE-Premier Ketac-SilverGIC (Applicap) GC Dental Industries GC Miracle Mix GIC
1. Ti-Core CR specimen before shear loading.
Ketac-Cem GIC (radiopaque)
agents containing glass ionomer materials with pretreated dentin at three time intervals. MATERIAL
This experiment was divided into five groups (Table I). Each part involved three time intervals, with 10 samples for each interval. Recently extracted human molar teeth were stored in distilled water for at least 48 hours, sectioned occlusally, placed in acrylic resinous blocks (Formatray, Kerr Mfg. Co., Romulus, Mich.), and cured for 24 hours before testing. Each core material was formed with a template used to ensure a cylinder 0.5 inches high with a diameter of 0.18 inches. Core materials were prepared in each case according to manufacturer’s directions. These cylindrical cores were then bonded to the prepared dentin with the same type of core material (Fig. 1). In the 15-minute group, the shear bond strengths were recorded 15 minutes after bonding without immersion in water. The samples in the remaining two groups were allowed to set for at least 1 hour and were then immersed in water for 24 hours and 7 days respectively. Groups 1 and 2 tested composite resin materials. In group I, Ti-Core CR was bonded with Tenure DBA and in group 2, Ti-Core CR was bonded to dentin with Scotchbond 2 DBA. Both procedures were performed according to manufacturers’ directions. Groups 3 through 5 tested GICs that were bonded to dentin with a 30-second pretreatment of approximately 40% polyacrylic acid of Durelon liquid (ESPE-Premier) diluted with an equal volume of distilled water. The dentin was rinsed with copious amounts of water and dried. In group 3, the Ketac-Silver GIC was applied to treated dentin. In group 4, GC Miracle Mix GIC was applied to treated dentin and in group 5, Ketac-Cem GIC was also placed on the treated dentin. THE
Test samples were positioned in a jig of the universal testing machine (Comten Industries, St. Petersburg, Fla.) and subjected to a shear stress at a crosshead speed of 0.25 inches/minute (0.635 cm/min) until failure. Failures was observed in two modes, either cohesive failure of the cylindrical core or adhesive failure of the core-to-dentin bond. The shear bond strengths were then calculated in pounds per square inch (psi). Statistical
The shear bond strengths were analyzed with a two-way analysis of variance (ANOVA) using the two factors of group and time. The five groups were numbered as follows: (1) Ti-Core CR and Tenure DBA, (2) Ti-Core CR and Scotchbond 2 DBA, (3) Ketac-Silver GIC, (4) GC Miracle Mix GIC, and (5) Ketac-Cem GIC. The three intervals examined were 15 minutes, 24 hours, and 7 days. A two-way ANOVA was computed to examine possible synergistic effects or interactions between groups and time. Duncan’s multiple range test was calculated to determine, specifically, the difference between various groups or times if the ANOVA verified a statistical significance for a specific factor.13 RESULTS Tables II through IV (for 15 minutes, 24 hours, and 7 days) summarizes the mean and standard deviations for the shear bond strengths in decreasing order for the groups. ANOVA revealed a highly significant difference (JJ< 0.0001) between groups, but there was no difference in shear bond strengths with time and no interaction between groups and time. Duncan’s multiple range test showed that there were four distinct groupings according to similar shear bond strengths: 1 versus 2 versus 3 and 4 versus 5. The greatest shear bond strength was attributed to Ti-Core CR with Tenure DBA, and the least was recorded by KetacCem GIC. There were random adhesive failures before shear testing of Ketac-Silver GIC, GC Miracle Mix GIC, and KetacCem GIC after placement at 100% humidity for either 24 905
m 300 % ;
q q q q
Tl-Core/Ten. Ti-Core/Scot. GC Mir.Mix Ketac-Silver Ketac-Cem
Fig. 2. Shear bond strengths
1 2 3 4 5
Ti-Core CR Ti-Core CR Ketac-Silver GC Miracle Ketac-Cem
1 2 4 3 5
Ti-Core CR Ti-Core CR GC Miracle Ketac-Silver Ketac-Cem
of the shear bond strength (or combination)
after 15 minutes
with Tenure DBA with Scotchbond 2 DBA Mix GIC GIC GIC
914 717 352 264 196
of the shear bond strength (or combination)
with Tenure DBA with Scotchbond 2 DBA GIC Mix GIC GIC
hours or 7 days. Samples exhibiting adhesive failure before testing were rerun; namely, after 7 days at 100 % humidity, five samples for GC Miracle Mix GIC, three samples for Ketac-Silver GIC and two samples for Ketac-Cem GIC
at 15 minutes.
212 199 236 133 103
after 24 hours for groups Mean
907 602 433 338 237
317 348 293 143 73
were retested. After 24 hours, two samples of GC Miracle Mix GIC and one sample of Ketac-Cem GIC were replaced, but adhesive failure was not observed for the composite Ti-Core CR with Tenure DBA or Scotchbond 2 DBA. Both
800 700 600 500 400 300 200 100
q q 0
Mean and standard
Shear bond strengths
of the shear bond strength (or combination)
Ti-Core CR with Tenure DBA Ti-Core CR with Scotchbond 2 DBA GC Miracle Mix GIC Ketac-Silver GIC Ketac-Cem GIC
2 4 3 5
modes of failure (adhesive-dentin material failure) were recorded adhesive failures were evident
failure and cohesive-core for the GICs, whereas only for the CR core materials.
DISCUSSION The shear bond strengths were always greater for the Ti-Core CR with Tenure DBA combination than any system studied (Figs. 2 through 4). The shear bond strengths recorded were: 914 psi (15 minutes), 907 psi (24 hours), and 995 psi (7 days). Tenure DBA was reported to have a shear bond strength after 24 hours of 1160 to 1943 psi,‘, 4, ’ but in this study, values of 907 psi were recorded. Differences between investigations can be attributed to variables that in-
Ti-Core/Ten Ti-Core/Scot GC Mir. Ketac-Silver Ketac-Cem
for 24 hours.
after 7 days for groups Mean
379 372 156
5 SD (2) 464 545 338 181
clude specimen preparation for storage, testing methodology, restorative materials, and techniques. Ti-Core CR with Scotchbond 2 DBA recorded the second greatest shear bond strengths: 717 psi at 15 minutes, 602 psi for 24 hours, and 704 psi after 7 days. Scotchbond 2 DBA was reported to have a shear bond strength after 24 hours of 688 to 957 psi,3, 5, i4, l5 but 602 psi was recorded in this study. The next strongest materials were the silver-filled GICs, Ketac-Silver GIC and GC Miracle Mix GIC. There was no statistical difference between these two groups. The shear bond strengths measured were 352 and 264 psi at 15 minutes, 338 and 433 psi for 24 hours, and 372 and 379 for psi
q q 0
Ti-Core/Ten Ti-Core/Scot GC Mir Ketac-Silver Ketac-Cem
Fig. 4. Shear bond strengths
after 7 days, respectively. Ketac-Silver GIC and GC Miracle Mix GIG were reported after 24 hours to exhibit shear bond strengths of 249 and 248 psi, respectively16> l7 but 338 and 433 psi were recorded in this study. Ketac-Cem GIC was the weakest in shear bond strength with values of 196 psi at 15 minutes, 237 psi for 24 hours, and 156 psi after 7 days. Ketac-Cem GIC was reported to develop a shear bond strength of 334 psi after 24 hours,ls but 237 psi was recorded in this investigation. The shear bond strengths measured at 15 minutes, 24 hours, and 7 days for the Ti-Core composite core material with Tenure DBA were two and a half to three times greater than for Ketac-Silver and GC Miracle Mix silver-filled GICs and even more for Ketac-Cem GIC. Tenure DBA had a consistently greater shear bond strength in all time intervals than Scotchbond 2 DBA, and this result is supported by simiIar studies.3, g, l1 There has been some indication that the time of application for shear loading was a critical factor.1g*20 Bond strengths are usually measured after 24 hours of storage in water or saline at body or room temperature. However, Fingerlg stated that the critical time for measuring shear bond strength was early when the stresses from polymerization contraction were established. It has been suggested that bond strengths should be determined immediately after the initial curing,20, ‘r but in this study there were no 908
after ‘7 days.
differences in shear bond strengths for the time intervals; namely 15 minutes, 24 hours, and 7 days.
CONCLUSIONS The shear bond strengths to dentin of Ti-Core titanium reinforced composite resin and two third-generation dentinal bonding agents (Tenure and Scotchbond 2) were compared with Ketac-Silver, GC Miracle Mix, and KetacCem glass ionomer cements. 1. A statistical analysis revealed that the shear bond strengths from the greatest to the least were: Ti-Core CR with Tenure DBA > Ti-Core CR with Scotchbond 2 DBA > Ketac-Silver GIC, GC Miracle Mix GIC > Ketac-Cem Gic. 2. There were no differences in the shear bond strengths with time and no evidence of interactions between groups and time. 3. The shear bond strengths for Tenure DBA with Ti-Core CR were two and a half to three times greater than for the silver-reinforced glass ionomer cements Ketac-Silver GIC and GC Miracle Mix. REFERENCES 1. Barkmeier WW, Co&y RL. Shear bond strength of Tenure Solution dentin bonding system. Am J Dent 1989;2:263-5. 2. O’Brien III JA, Retief DH, Bradley EL, Denys FR. Shear bond strength DECEMBER
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13. Zar JH. Biostatistical Analysis. Englewood Cliffs, NJ: Prentice-Hall, 1974;151-4. 14. Retief DH, Bastos PAM, Bradley EL, Denys Fr. Shear bond strength of Scotchbond 2/Silux to dentin. Am J Dent 1989;1:245-53. 15. Ishioka S, Caputo AA. Interaction between the dentinal smear layer and composite bond strength. J PROSTHET DENT 1989;61:180-5. 16. Walls AWG, McCabe JF, Murray JJ. Factors influencing the bond strength between glass polyalkenoate (ionomer) cements and dentine. J Oral Rehabil 1988;15:537-47. 17. Nation W, Jedrychowski JR, Caputo AA. Effect of surface treatments on the retention of restorative materials to dentin. J PROSTHET DENT 1980;44:638-41.
18. Peddey M. The bond strength of polycarboxylic acid cements to dentine: effect of surface modification and time after extraction. Aust Dent J 1981;26:178-80. 19. Finger WJ. Dentin bonding agents. Relevance of in vitro investigations. Am J Dent 1988;1:184-8. 20. Komatsu M, Finger W. Dentin bonding agents: correlation of early bond strength with margin gaps. Dent Mater 1986;2:257-62. 21. Finger WJ, Ohsawa M. Effect of bonding agents on gap formation in dentin cavities. Oper Dent 1987;12:100-4. Reprint
BRETT I. COHEN, PHD 89 LECNING STREET S. HACKENSACK, NEW JERSEY 07606
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