Journal of Dental Medicine

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Dentin bonding agents create stronger bonding between dental composites and dentin. But, none of them can prevent the microleakage. The important factors of progressing microleakage are the stress of polymerization shrinkage of resin composite and removal of smear layer in total-etch technique. The aim of this study was the evaluation of the effect of experimental method (modifying smear layer and etching of enamel margin) and comparison with the total-etch technique. In this experimental method, 60 extracted human molar teeth were disinfected. Then, class 5 cavities were prepared on the buccal surface and 1 mm above CEJ. The specimens were divided randomly to 6 groups with iO samples in each group. The specimens groups were:
1- Scotchbond Muiti- Purpose Plus Adhesive System (S.B.M.P.P) +Tetric composite
2- S.B.M.P.P + Ariston composite
3- Ariston liner + Ariston composite
4- S.B.M.P.P without enamel and dentin etching + Tetric composite + rebonding with Flowable Tetric
5- S.B.M.P.P without enamel and dentin etching + Ariston composite + rebonding with Flowable Tetric
6- S.B.M.P.P without enamel and dentin etching + Tetric composite
After finishing and polishing, the specimens were termocycled, stained with fushin, sectioned within the specimens and evaluated for dye penetration with stereomicroscope. Wilcoxon Sign and Kruskal Wallis tests were used for statistical analysis.
Results showed that group 3 had microleakage more than groups of 1, 2 and 5 (P<0.0 5) and this difference was significant. There was no significant difference among the other groups.

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Statement of Problem: Considering that the role of collagen fibers in dentin adhesion has not been thoroughly established yet, the removal of exposed collagen fibers with a deproteinization agent such as sodium hypochlorite following etching may facilitate access of adhesive resins to a substrate that is more penetrable and less sensitive to water content which in turn would lead to a more durable bonding system. Furthermore, due to sodium hypochlorite clinical application as a cleanser or canal irrigator, its effects on the surface before etching may influence adhesive bonding strength.

Purpose: The goal of this study was to evaluate the effects of a two-minute 5.25% NaOCL application on composite restorations microleakage, using two different adhesive systems.

Materials and Methods: In this interventional experimental study, on seventy-two extracted boving incisors class V cavities were prepared on dentinal surfaces. The specimens were then randomly divided into six equal groups: A1) Acid etch (AE) dentin bonding Scontchbond Multipurpose Plus (SBMBP), A2) AE/ dentin bonding One Step (OS), B1) NaOCL/ AE/SBMPp, B2) NaOCL/AE/OS, C1) AE/NaOCL/SBMPp, C2) AE/NaOCL/OS. After bonding procedures according to the manufacturer’s instructions, cavities were restored using Z100 composite. Then, the specimens were thermocycled for 500 times in water baths of 5 and 55C. After thermocycling, the specimens were immersed in a 0.2% solution of basic fuchsin for 24 hours. A buccolingual section at the center of each restoration was obtained and examined with a stereomicroscope to evaluate color penetration into cavities. The data were subjected to two-way variance analysis.

Results: The microleakage of group B was significantly less than those of A and C (P<0.001). No significant difference was found between groups A and C (P=0.73). There were also no significant differences within groups A, B and C (P=0.852). No interaction was observered between dentin bondings and surface treatment (P=0.946).

Conclusion: The findings of this study revealed that NaOCL application after etching, for hybrid layer removal, did not make any difference on microleakage as compared with conventional bonding systems. However, its application before etching improved the seal of restoration. Additionally, there was not any significant difference between two different dentin bondings.

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Background and Aim: An important requirement for a dentin bonding agent is biological compatibility. Since dentin bonding agents are placed in cavity preparations with subgingival extensions, with direct contact to gingival and mucosal tissues, tissue response to these materials must be investigated. The aim of this study was to examine the cytotoxicity of AdheSE, a self etching adhesive, on human gingival fibroblasts.
Materials and Methods: In this experimental in vitro study, primary human gingival fibroblasts were exposed to different dilutions of primer & bond of AdheSE (Vivadent, Liechtenstein). The toxicity of the primer was tested in 30 seconds, 300 seconds and 24 hours. The cytotoxicity of the bond was analyzed in uncured mode after 20 seconds, 5 minutes and 24 hours. In cured mode, tested materials were analyzed after 24 and 48 hours. Cytotoxic effects were evaluated using MTT, cell counting and DNA condensation assays. Data were analyzed by two way repeated measure ANOVA with p<0.05 as the level of significance.
Results: MTT Assay revealed that uncured AdheSE Bond was toxic only in 10-1 dilution and the difference with control group was significant (P<0.05). By increasing the time to 300sec. and 24h, dilutions of 10-2 and 10-4 were the most cytotoxic respectively. Cytotoxicity of uncured primer after 30 sec. and 300 sec. began from 10-2 and after 24h began from 10-2 and reached to 10-1. AdheSE in cured mode showed significant difference with control group in 1:2 (P<0.001),1:4 & 1:6 (P<0.01) dilutions. In cell counting assay only the 1:2 dilution was significantly more toxic than control group. Apoptosis (a morphological and biochemical distinct form of cell death that regulates cell turnover) comprised in less than 5% of total death in both cured and uncured adhesives.
Conclusions: Based on the results of this study, by increasing the exposure time, smaller amounts of bonding could be cytotoxic. Cytotoxicity was related to material, dilution, time of exposure and curing. It would be necessary to identify the toxic ingredients of this adhesive and replace them by more biocompatible components.

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Background and Aim: Amalgam is one of the mostly used restorative materials, but has some disadvantages. Microleakage is one of the short comings of amalgam which may lead to sensitivity and recurrent caries. The aim of this study was to evaluate the effect of three dentin bonding systems on reduction of microleakage in amalgam restorations.

Materials and Methods: Class II amalgam restorations were made in 40 noncarious molar and premolar teeth. Then the specimens were divided into four equal groups. Scotch Bond Multi Purpose, Single bond,
iBond, were used as liner in groups one to three respectively and in group four no liner was used. The teeth were restored with high copper spherical amalgam. After thermocycling for 500 cycles at 5⁰C and 55⁰C, the specimens were immersed in basic fuchsin for 24 hours, bisectioned mesiodistally and evaluated under stereomicroscope at X25 for dye penetration. The data were analyzed by Kruskal-wallis and Scheffe. P<0.05 was considered as the level of significance.

Results: The groups showed significant difference (p=0.003). The group four had significantly less microleakage than the first and second groups (p<0.05). The second and third groups showed significantly different microleakage (p=0.038).

Conclusion: Based on the results of this investigation applying dentin bonding agents has no effect on reducing microleakage in amalgam restorations, however more studies are recommended.

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Background and Aim: Fractured anterior teeth can be restored by adhesive bonding of the separated fragment to the remaining tooth structure. This invitro study evaluated the force required for fracture of rebonded fragments which were dried and rewetted for various time intervals prior to bonding.

Materials and Methods: One hundred and eight human mandibular incisors were selected and were divided into 9 groups and then were fractured. The fragments were stored in air at room temperature and ambient humidity. They were air dried for 30 minutes in group 1, 2 and 3,  6 h in group 4 and 5,  24 h in group 6 and 7, and 3 days in groups 8 and 9. The apical parts of the fractured teeth were stored in water.After storage in air, each fragment in group 1 was bonded to the remaining apical tooth structure with a bonding agent and flowable composite.In groups 2, 4, 6 and 8 after air drying the fragments were stored in water for 30min. The time of storage in water in groups 3, 5, 7, 9 was 24 hours. Then each fragment was bonded to the apical part structure. The mean force required for fracture was measured by a mechanical testing machine. One way ANOVA and Tuckey tests were used for analysis.

Results: There were statistically significant differences between different groups (p<0.001).The highest and lowest force required for fracture belonged to groups 3 and 8 respectively. The force required for fracture in group 1 was lower than group 2, 3, 5 and 7 and 9 and more than groups 4,6 and 8 with significant differences.While there were no significant differences among groups 3, 5, 7, 9 and 4, 6, 8 the force required for fracture in groups 2, 3, 5, 7 and 9 was more than 4, 6, 8 with significant differences.

Conclusion: This research revealed that the force required for fracture was affected by air storage of fragments prior to bonding. Also showed that with an increase in duration of drying the force required for fracture decreased and after a period of time it becomes steady. This study showed that in order to increase the fracture strength after air drying the fragment should be immersed in water for at least 24 hours prior to bonding.

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Background and Aim: Evaluation of shear bond strength and microleakage of bonding agents is important as these properties play main roles in adhesion of composite to dental tissues. Microleakage results in bacterial penetration into dentin tubules and enamel surfaces and causes sensitivity and recurrent caries followed by destruction of composite filling. Insufficient shear bond strength results in early failure of filling in low masticatory forces. The main goal of this study was to compare the microleakage and shear bond strength of an experimental adhesive and Scotchbond multi-purpose (MP) adhesive system.
Materials and Methods: In this experimental study, sixty extracted caries free human molar teeth were randomly assigned into 4 groups of 15 each for shear bond strength. Variables were bonding agents, enamel and dentin. Twenty teeth assigned into 2 groups of 10 each were used for valuation of the microleakage. Microleakage and shear bond strength were performed according to ISO TR 11405. All data were analyzed with parametric and non-parametric tests according to their normality distribution. Also, Weibull distribution performed on data.
Results: Data obtained from both microleakage and shear bond strength tests showed no significant difference between the experimental bonding and Scotchbond MP bonding (P>0.05). Furthermore, there was no significant difference between the microleakage of occlusal and gingival parts of both bondings (P>0.05).
Conclusion: Experimental adhesive bonding showed acceptable results regarding microleakage and shear bond strength. It may be concluded that the experimental dentin bonding had a comparable performance quality with that of commercial system.

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Background and Aims: In this in-vitro study, the effect of multiple adhesive coating on the microshear bond strength of composite to dentin and surface microhardness of dentin after treatment with four adhesives (One Step Plus, One Step, Single Bond, Single Bond 2) were evaluated.

Materials and Methods: One hundred intact human molars were cut to obtain disks of dentin having 2 mm thickness. For the microshear bond test, sixty disks were randomly divided into four groups. In each group one type of adhesive was used. In one half of a disk two layers and in another half six layers of adhesive were applied. Cylinders with 1mm height was filled with a composite and light cured. The cross-head speed was 0.5 mm/min. Vickers microhardness was tested on forty dentin disks which divided into four groups and prepared in the same manner used for microshear bond test. Data were analyzed by Two-way ANOVA and Tukey tests.

Results: The highest and lowest bond strength were recorded as 29.49 ± 5.74 MPa (One Step Plus 6 layers), and 21.23 ± 4.83 MPa (One Step Plus 2 layers), respectively. The results indicated that One Step Plus bond strength in 6 Layers was significantly higher than 2 layers. The highest and lowest dentin hardness values were
39.08 ± 8.34VHN (Single Bond 2 layers) and 28.53 ± 5.98 VHN (One Step Plus 6 layers). None of the adhesives exhibited significant difference in hardness with regards to the layers applied (P>0.05). Presence of filler in adhesives had no significant effect on bond strength (P=0.05) whereas caused significant decrease in the dentin microhardness (P<0.05). In addition, type of solvent had significant effect on the bond strength and bond strength was significantly higher in acetone-base adhesives (P<0.05). However, dentin microhardness was significantly higher in the ethanol-base adhesives (P<0.05).

Conclusion: Multiple adhesive coating had no influence on the microshear bond strength of composite to dentin and dentin surface microhardness. It was dependent on the type of adhesive used.

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Background and Aims: The aim of this in vitro study was to assess the shear bond strength of amalgam to dentin using four dentin adhesive systems.
Materials and Methods: One hundred human molars were selected. After enamel removal, a dentin cylinder with 3 mm thickness was prepared. Eighty specimens were resorted with amalgam and four dentin adhesive systems as follows (n=20): group 1, Scotch Bond Multi-Purpose group 2, One Coat Bond group 3, PQ1 and group 4, Panavia-F. In group 5, 20 specimens were resorted with amalgam and varnish as control group. The specimens were incubated at 37°C for 24 h. The shear bond strengths were then measured by using push out method. The data were analyzed by one-way ANOVA and post hoc Duncan's tests.
Results: Mean values for bond strengths of test groups were as follows: group 1=21.03±8.9, group 2=23.47±9, group 3=13.16±8.8, group 4=20.07±8.9 and group 5=14.15±8.7 MPa±SD. One-way ANOVA showed the statistically significant difference between the bond strengths of five groups (P=0.001). Post hoc Duncan's test showed significant difference between groups 1and 3 (P=0.008), groups 1 and 5 (P=0.019), groups 2 and 5 (P=0.0008), groups 4 and 5 (P=0.042), and groups 3 and 4 (P=0.018).
Conclusion: Results of this study showed that the bond strength of amalgam to dentin using One Coat Bond as dentin adhesive system was higher than that observed in other dentin adhesive systems.