| Abstract|| |
Context: Zinc-oxide eugenol (ZOE) is frequently used due to its satisfactory biological response, sedative effect on the pulp, and easy removal. However, literature is very controversial about the influence of the temporary cement-containing eugenol on the bond strength properties. Aims: This study aims to clarify the literature controversy by evaluating the bond strength of ZOE or ZOE-free applied before bonding procedures and the 7-day resting period after the first session. Settings and Designs: Twelve recently extracted third molars were randomly divided into three groups: Group 1: Control (without treatment), Group 2: Temp-Bond NE; Group 3: Temp-Bond. Subjects and Methods: After temporary restorations, the teeth were immersed in distilled water and stored for 7 days at 37°C. The temporary cement was mechanically removed, and prophylaxis was performed. The adhesive procedures were performed, and a 6-mm-high composite resin block was built. The teeth were immediately stored at 100% relative humidity at 37°C for 24 hours. Specimens with 0.7 (±0.2) mm2 of cross-sectional area were obtained and subjected to a microtensile bond strength (μTBS) test at 1 mm/min until failure. Statistical Analysis Used: Analysis of variance (ANOVA) and Tukey's post hoc test were used for statistical analysis. Results: ZOE or ZOE-free cement did not interfere in the μTBS between resin composite and dentine when used with a two-step-etch-rinse adhesive material, considering 7 days of resting period after the first session, by the ANOVA and Tukey's post hoc test (P < 0.05). Conclusions: The authors recommend the removal of the temporary cementation at least seven days after the first session and suggest that the clinicians follow-up further studies to use the cement in case its removal is recommended within a longer period.
Keywords: Dental adhesive, eugenol, microtensile test, resin composite, temporary cement
|How to cite this article:|
Bezerra CP, Campos CF, Leite J, Fernandes MS, Coury Saraceni CH, Rodrigues FP, Dutra-Correa M. On the understanding of zinc-oxide eugenol cement use prior to etch-rinse bonding strategies. Indian J Dent Res 2019;30:424-7
|How to cite this URL:|
Bezerra CP, Campos CF, Leite J, Fernandes MS, Coury Saraceni CH, Rodrigues FP, Dutra-Correa M. On the understanding of zinc-oxide eugenol cement use prior to etch-rinse bonding strategies. Indian J Dent Res [serial online] 2019 [cited 2019 Oct 16];30:424-7. Available from: http://www.ijdr.in/text.asp?2019/30/3/424/264114
| Introduction|| |
Composite resin restorations are used to achieve good esthetic results, and the success of these depends on the hybrid layer quality.
Zinc-oxide eugenol (ZOE) is used due to its biological response, pulp sedation,,, and easy removal. However, literature is controversial about its application before bonding  as it is well known that eugenol has radical-scavenging activity which inhibits polymerization. However, ZOE or ZOE-free did not cause adverse effects ,, and is safely recommended before bonding procedures,,, after 7 days of application although some authors showed reduced bond strength.,
Thus, this study evaluated the bond strength of a two-step-etch-rinse adhesive using ZOE and ZOE-free applied before bonding.
| Subjects and Methods|| |
This research protocol was approved by the University Institutional Review Board (Ethics Committee – Protocol: 063/06). Caries-free human third molars were obtained from the tooth bank of the university; all recently extracted for orthodontic reasons. The teeth were cleaned with pumice/water under slow speed for 15 seconds and then stored in a 0.5% chloramine solution at 4°C. Before bonding procedures (24 h), the teeth were left immersed in distilled water at 4°C.
After this period, the radicular portions of the teeth were mounted on a phenolic ring (Buehler Ltd, Lake Bluff, IL, USA) with acrylic resin, and occlusal surfaces were cross-section removed using proper cutting machine (IsoMet 1000, Buehler Ltd, Lake Bluff, IL, USA) with a diamond cutting disc under water cooling, aiming to expose the dentine for bonding procedures.
The dentinal surface was polished with 600-grit silicon carbide abrasive paper (3M ESPE, ST. Paul, MN, USA) under running water for 60 seconds (Polishing Machine Politriz Maximille Metalotest Solotest Com., São Paulo, SP, Brazil) to standardize the smear layers  before bonding procedures.
Then, 12 teeth were randomly divided into three groups (four teeth per group), with 15 specimens in each group (n = 15): Group 1: Control (untreated); Group 2: ZOE-free Temp-Bond NE (Kerr Corporation, Orange, CA, USA); Group 3: ZOE Temp-Bond (Kerr Corporation, Orange, CA, USA).
One hour after material insertion (Temp-Bond NE and Temp-Bond), the specimens were stored in distilled water at 37°C for 7 days. After this period, the temporary cement was mechanically removed and then cleaned with pumice and water with manual slow-paced movements for 60 seconds and subsequently washed for 30 seconds.
The adhesive procedures were performed on the dentinal surface: phosphoric acid etching at 37% + Single Bond (3M ESPE, St Paul, MN, USA). A 6 mm high composite resin block (P60-3M ESPE) was built with an increment of 2 mm each and light-cured with 600 mW/cm 2 irradiation. The device's curing density power was checked with a curing radiometer (Spring Light Meter, Norristown, PA, USA). All materials were used according to the manufacturer's instructions [Table 1]. The teeth were immediately stored at 100% relative humidity for 24 h at 37°C.,
After this period, all teeth were serially cut in X and Y axis using a metallographic cutter (IsoMet 1000, Buehler Ltd., Lake Bluff, IL, USA) under water, creating specimens with 0.7 (±0.2) mm 2 of cross-sectional area. This area was measured with a digital caliper (Mitutoyo Corp., Kanagawa, Japan). Peripheral specimens and those that showed no perpendicular interface were discarded.,
Each specimen was fixed with cyanoacrylate glue (LOCTITE®, Henkel) on a microtensile device and tested on a Universal Testing Machine at 1 mm/min crosshead speed.
Data were subjected to analysis of variance (two-way) followed by post hoc Tukey test for pairwise comparison (P < 0.05) with Minitab Statistical Software, version 2007 (Minitab Inc., State College, Pennsylvania, USA).
| Results|| |
The bond strength and the respective standard deviations are shown in [Figure 1]. After application of post hoc Tukey test, the results showed that there was no statistically significant difference between the control group and the two experimental groups.
|Figure 1: Editing certificate - On the understanding of zinc-oxide eugenol cement use prior to etch-rinse bonding strategies|
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| Discussion|| |
This study evaluated the temporary cement with or without eugenol applied before adhesive procedures. Results showed that none of the cement promoted adverse effects or interfered in the microtensile bond strength (μTBS). These results are corroborated by other authors in the literature., However, the results need to be interpreted with caution due to differences in materials and methodologies used, in special, because some of the studies performed with these cements used microshear and not microtensile tests.
In this study, the microtensile test was performed rather than microshear as, in the last one, the specimen is subjected to tensile at the loading application area and not to shear. Moreover, it has been shown that it is unlikely that this test is accurately testing the interface as the maximum stresses will not be distributed over a larger circular area (all the perimeters of the interface), such as in a torsion test that generates shear stresses at the whole interface. In the tensile test, stresses are much more homogeneous along the interface than in shear, leading to a maximum principal stresses closer to the nominal strength, justifying the election of this test for the present study. Thus, comparisons between our microtensile study with others using microshear tests were made with caution.
Temporary cement with eugenol is pointed out as a cause of adverse effects when using adhesive systems/resin composites , as lower μTBS is presented by eugenol cement when compared to eugenol-free cement. On the other hand, several researchers described that none of the cement (ZOE/ZOE-free) caused any adverse effect on evaluated adhesive systems.,, Dentine bond strength was not affected by temporary cement with eugenol, even when a self-etching adhesive/resin cement was used., It was observed that studies which investigated the effect of eugenol on resin-dentine bond strength considered different time for the cement removal after the first session, which could explain the differences among the studies, apart from applied tests and verified adhesive systems.
To evaluate the effect of the eugenol exposure time of a eugenol-based provisional restorative material on the shear bond strength (SBS) of two-step and one-step self-etching adhesives to dentine, at different intervals, some authors  found that prior use of eugenol-containing temporary restorative material reduced self-etch adhesive systems bond strength over a 24-h period. However, no reduction in bond strength at 7 or 14 days exposure was observed with either two-step or one-step self-etch adhesive. This information can explain why the bond strength was not reduced as, in the present study, the time for removal was 7 days after the first session. The negative results after 24 h were also reported by other authors  who did not recommend the use of this cement prior resin-based materials application. In their study, after 24 h, the ZOE restoration was mechanically removed, and dentine surfaces were ultrasonically cleaned. Their results showed that despite the prior use of eugenol-contained temporary restoration affected the resin-dentine bond strength of the etch-rinse Single Bond, a more pronounced reduction in bond strength was observed for the two self-etch systems evaluated (iBond, Clearfil SE Bond). The authors of the present study agree that these results need to be interpreted with caution as the use of temporary cement in clinics usually surpasses the 24-h sealing period.
ZOE cement is not stable in the presence of excess water, and it is clinically reasonable to consider the water used for manipulation as well as the water present in dentine after tooth preparation and cleaning. This is one of the main reasons (including low wear abrasion) why it has life and applicability limits as definitive cement: It probably dissolves in the present fluid, percolating due to lack of sealing.
The use of temporary cement with eugenol could affect the interaction success between adhesive systems and dental structure and also the polymerization of resin composite or resin cement., This noninteraction could lead to a bond strength reduction to self-etch adhesive systems  as eugenol can slightly suppress the polymerization of the resin composite  or, in fact, inhibit polymerization, due to its extreme affinity with free radicals. On the other hand, some authors  found no interaction evidence between the temporary cement with eugenol and adhesive systems. Some others, additionally, emphasized that the temporary cement removal type and method (hand scaler for 10 s, prophylaxis with pumice-water slurry for 10 s, and a jet of aluminum oxide for 10 s) may affect the adhesion of resin-bonded indirect restorations.
Use of acid conditioner for temporary cement cleaning was also reported as bond strengths reducer. However, the use of etching in the present study was not particularly investigated, but it seemed not to affect final results. In this study, the type of temporary cement removal was mechanical; prophylaxis with pumice-water slurry was conducted and followed by dental etching before the adhesive procedure. In this way, under these same experimental conditions, none of the cements affected the μTBS.
In a study, which investigated the bond strength to dentine of primary teeth after using pulpotomy agents and some ZOE, powder: liquid (P:L) ratios showed that bond strength was affected by the agents and the ZOE P:L but not by the applied adhesive systems, which were Primer and Bond NT and OptiBond Solo Plus. The same findings were reported by other authors  who investigated the bond strength of six self-etching adhesives (AdheSE, Adper Prompt L-Pop, Clearfil SE Bond, iBond, OptiBond Solo Plus-Self-Etch Adhesive System, and Xeno III) with a universal resin composite in cavities previously cemented with ZOE. When considering Freegenol and Fermit, some others  found that they seemed to have beneficial effects on the SBS values of Syntax and Art Bond. In this referred study, the only bonding system which produces acceptably high average SBS values with eugenol-containing provisional cement was P-Bond.
In summary, the recommendation or not to use ZOE cement needs to be based on the resting period after the first session. Clinicians, as well as researchers, when working in an office and/or in the universities (also teaching), need to explore this topic and recommendations with caution and avoid material misuse. None of the cement interfered in the μTBS of resin composite and dentine when used with etch-rinse adhesive material, considering the recommended resting period after the first session.
| Conclusions|| |
The authors recommend the removal of the temporary cementation, at least, 7 days after the first session and suggest that the clinicians follow-up further studies to use these cement in case, their removal is recommended within a longer period.
Financial support and sponsorship
We thank CNPq #310001/07-2 PhD-Technical Scholarship for the financial support.
Conflicts of interest
There are no conflicts of interest.
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Dr. Maristela Dutra-Correa
Rua Dr. Bacelar, 1212, 4° andar, São Paulo
Source of Support: None, Conflict of Interest: None