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Effect of different surface-cleaning techniques on the bond strength of composite resin restorations
Effect of different surface-cleaning techniques on the bond strength of composite resin restorations Selim Erkut, DDS, PhD,a Burak Yilmaz, DDS, PhD,b Bora Bagis, DDS, PhD,c Cigdem Küçükes¸men, DDS, PhD,d Erdem Ozdemir, DDS, PhD,e and Ozlem Acar, DDS, PhDf Faculty of Dentistry, Baskent University, Ankara, Turkey; The Ohio State University College of Dentistry, Columbus, Ohio; Faculty of Dentistry, Izmir Katip Celebi University, Izmir, Turkey; Faculty of Dentistry, Suleyman Demirel University, Isparta, Turkey Statement of problem. Different techniques have been suggested for cleaning dentin surfaces after the removal of an interim prosthesis and before the application of a bonding agent. How different surface-cleaning techniques affect the bond strength of the composite resin restorations is not clear. Purpose. The purpose of this study was to investigate the effects of different surface-cleaning techniques on the bond strength of composite resin restorations and the surface topography of the prepared tooth surfaces. Material and methods. The occlusal surfaces of 25 molars were ground until the dentin was exposed. A bonding agent and interim cement were applied on the teeth. The teeth were divided into 5 groups (n¼5) according to the method used for surface-cleaning (microairborne-particle abrasion, alcohol, rubber-rotary instrument, desiccating agent, and control). Once the surfaces of the teeth had been cleaned, the same bonding material was applied to the teeth. A 5-mm-thick composite resin layer was built up. Each specimen was sectioned to microbars, and 6 centrally located beams were selected for microtensile testing (n¼30) (1.10 0.10 mm). The data were statistically analyzed with 1-way ANOVA (1-sample Kolmogorov-Smirnov test). The Bonferroni test was used for significantly different groups (a¼.05). One specimen from each group was observed under a scanning electron microscope and an atomic force microscope. Energy dispersive x-ray analysis also was performed. Results. Bond strength values were in the following descending order: microairborne-particle abrasion, desiccating agent, alcohol, rubber-rotary instrument, control. Differences between the microairborne-particle abrasion group and the remainder of the groups, desiccating agent–rubber-rotary instrument, desiccating agent-control, alcohol–rubber-rotary instrument, and alcohol-control groups, were statistically significant (P<.05). The microairborne-particle abrasion group displayed the roughest surface and a different surface topography from the remainder of the groups. Increased aluminum was observed in the microairborne-particle abrasion group. Conclusions. Surface-cleaning techniques, except for the rubber-rotary instrument, increased the bond strength of composite resin. The roughest dentin surfaces and highest bond strength were achieved with the microairborne-particle abrasion technique. (J Prosthet Dent 2014;112:949-956)
Clinical Implications When using a dual-polymerizing technique that involve a bonding agent, clinicians may prefer to clean dentin surfaces with microairborne-particle abrasion after removing interim restorations.
a
Associate Professor, Department of Prosthetic Dentistry, Faculty of Dentistry, Baskent University, Ankara, Turkey. Assistant Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry. c Associate Professor, Department of Prosthetic Dentistry, Faculty of Dentistry, Izmir Katip Celebi University, Izmir, Turkey. d Assistant Professor, Department of Pediatric Dentistry, Faculty of Dentistry, Süleyman Demirel University, Isparta, Turkey. e Private practice, Antalya, Turkey. f Fellow, Department of Prosthetic Dentistry, Faculty of Dentistry, Baskent University, Ankara, Turkey. b
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Volume 112 Issue 4 When adhesive restorations are placed in a single visit, it is relatively easy to provide a contaminant-free bonding surface such as prepared dentin. However, restorations that require multiple visits need interim prostheses1,2 that are luted with an interim luting agent. Results of studies have provided information regarding the effect of interim luting agent remnants that are difficult to remove even with magnification.3-6 Results of these studies also showed a decrease in the bond strength between the dentin and the prosthesis after an interim restoration when different cleansing methods were used.5,7 Several studies have reported the difficulty of removing interim cement from the prepared tooth surface and the negative impact of the definitive cements to the tooth surface on the bond strength.3-6,8-11 The dual-polymerizing (DP) technique is the application of dentin bonding agents on the prepared tooth surfaces immediately after tooth preparation and the application of the same agent before definitive cementation of the indirect prosthesis.12-15 The aim of the DP technique is to minimize postoperative sensitivity,16-21 to seal the exposed dentinal tubules immediately after tooth preparation, to enhance the bond strength, and to minimize the negative effects of interim cements. In the conventional bonding technique, partial disruption between the hybrid layer and the overlying resin is uncommon. In the DP technique, longer resin tags are formed, and no discontinuity exists in the dentin-resin interface or between the prepolymerized adhesive and the luting composite resin. In the conventional technique, the luting space is mostly occupied by luting composite resin, and unpolymerized dentin adhesive is thinned out by more viscous composite resin when the restoration is inserted. In the DP technique, the luting space is thicker because it is composed of 2 distinct layers: the prepolymerized adhesive and the luting composite resin.22 In a finite element analysis study, Coelho et al23 stated that, from a clinical standpoint,
adhesive layer shrinkage due to thicker adhesive layers should be avoided because it will increase stress concentration regardless of tension and compression at the adhesive layers and will introduce shearing components between both composite resin and dentin bonding interfaces. They reported that the effectiveness of the DP technique should be confirmed with long-term clinical studies.23
Table I.
In the DP technique, as opposed to the conventional method, the interim cement is in contact with a hybridized dentin surface coated with a polymeric layer that has different surface properties than dentin.12,24 Several in vitro studies have reported enhanced bond strength with the DP technique through the elimination of the effects of interim cements on the dentin surfaces.25-27 Even though the application steps of
Test groups
Groups Control 1. Clean with water and fluoride-free pumice 2. Wash and dry with oil-free air 3. Etch and dry 4. Apply bonding agent and light polymerize 5. Apply composite resin and light polymerize Microairborne-particle abrading 1. Clean with water and fluoride-free pumice 2. Wash and dry with oil-free air 3. Airborne-particle abrade 4. Dry with oil-free air and alcohol 5. Apply bonding agent, light polymerize 6. Apply composite resin and light polymerize Alcohol 1. Clean with water and fluoride-free pumice 2. Rinse and dry with oil-free air 3. Wipe with alcohol and dry 4. Etch and dry 5. Apply bonding agent and light polymerize 6. Apply composite resin and light polymerize Desiccating agent 1. Clean with water and fluoride-free pumice 2. Rinse and dry with oil-free air 3. Wipe with desiccating agent and dry 4. Etch, rinse, and dry 5. Apply bonding agent and light polymerize 6. Apply composite resin and light polymerize Rubber-rotary instrument
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1. Remove the interim luting agent with rubber-rotary instrument 2. Rinse and dry with oil-free compressed air 3. Etch, rinse, and dry 4. Apply bonding agent and light polymerize 5. Apply composite resin and light polymerize
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October 2014 the DP technique are similar in different studies, different techniques have been reported for cleaning the surface of hybridized dentin. The purpose of this study was to investigate the effects of different surfacecleaning techniques on the bond strength of the definitive prosthesis and surface topography of the prepared tooth surfaces when the DP technique is used. The bond strength was evaluated by using microtensile bond strength tests. Scanning electron microscopy (SEM) was used to evaluate the interfacial layers in different bonding techniques and the resin-based luting agents. The atomic force microscopy (AFM) technique was used to observe the tooth surfaces after the surfaces were cleaned with different techniques after interim prosthesis removal and before definitive cementation. The null hypothesis of this study was that no differences would be found between the effects of different surface-cleaning methods with the DP technique on the bond strength of the composite resin restorations and the surface topography of surfaces treated with a bonding agent.
951 with standard mode (Elipar Freelight LED 2; 3M ESPE). Noneugenol interim cement (Rely X Temp NE; 3M ESPE) then was applied to the ground surface of the teeth. The teeth were stored in distilled water at 37 C for 24 hours. After the excess interim cement had been cleaned from the teeth with water and fluoride-free pumice, the surfaces were washed and dried with oil-free compressed air. Twenty-five teeth were assigned to 5 groups (n¼5 per group) according to the method of surface cleaning (Table I). The groups were as follows: control (Cont), microairborneparticle abrasion (MAPA), alcohol (Alco), desiccating agent (DA), and rubber-rotary instrument (RRI). After the teeth had been dried with oil-free compressed air, the surfaces in the Cont group were not treated with anything. Once the teeth surfaces were cleaned, the same bonding agent (Single Bond 2; 3M ESPE) was reapplied on the surface of the teeth and polymerized as previously described. A 5-mmthick composite resin layer, cylindrical in shape and perpendicular to the dentin flat surface, then was built up incrementally (Clearfil Ap-x Restorative
System; Kuraray) on each tooth. All composite resin foundations were light polymerized with the light-emitting diode in standard mode (Elipar Freelight LED 2). While the microtensile bond strength (mTBS) test specimens were being prepared, the specimens were stored in distilled water at 37 C for 72 hours. Each was then serially sectioned vertically into rectangular beams (1.10 0.10 1.10 0.10 mm) with a slow-speed diamond wafering blade (Ernst Leitz GMBH) (Fig. 1). Cross-sectional areas were measured with digital calipers. Six centrally located beams from each tooth were used for the microtensile bond strength (mTBS) test (n¼30 per group). The specimens were attached to a microtensile tester (Bisco) with cyanoacrylate resin (Zapit; DVA) and subjected to microtensile testing at a crosshead speed of 0.5 mm/min. until they were debonded. The values of the variables were normally distributed, and the variance of each group was equal; therefore, the bond strength differences were statistically analyzed by using the repeated measures of ANOVA (1-sample
MATERIAL AND METHODS The project was approved by the institutional review board of Karadeniz Technical University, Trabzon, Turkey. Twenty-five caries-free and restorationfree human molars extracted from individuals between 22 and 50 years of age were used for this study (80% power [type II error]). The teeth were stored in a 0.5% chloramine solution at 4 C for up to 1 month after extraction. The soft tissues were removed with a scaler (Scaler, H6/H7; Hu-Friedy). Each tooth was wet ground occlusally with silicon carbide abrasive up to paper no. 1000 (FEPA, Struers RotoPol 11; Struers A/S). The occlusal surfaces were ground until all enamel islands were removed and only dentin was exposed. A bonding agent (Single Bond 2; 3M ESPE) was first applied on the surface of the teeth with a brush and was light polymerized with a solid-state, light-emitting diode polymerizing device
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1 Schematic, showing specimen preparation.
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Volume 112 Issue 4 The MAPA group had the highest bond strength, and the differences between the MAPA group and the remainder of the groups were statistically significant (P<.05). The DA group displayed the second highest bond strength, and the difference between the DA-RRI and DACont groups was statistically significant (P<.05). The third highest bond strength was seen in the Alco group, and the bond strength of the Alco group was significantly higher than the
bond strength of the RRI and the Cont groups (P<.05). The RRI group had a higher bond strength than the Cont group; however, the difference was not statistically significant (P>.05). The failure modes were evaluated under SEM, and the distribution of the failure modes is displayed in Figure 3. In the SEM evaluation, the 750 magnification of the images was taken into consideration. The MAPA group displayed the roughest surface (Fig. 4A).
Means and standard deviations (SD) for microtensile bond strength (n¼30)
Table II.
Mean (SD) microtensile bond strength (MPa)*
Groups Control
16.69 2.56c
Microairborne-particle abrasion
32.24 2.7a
Desiccating agent
24.77 1.73b
Alcohol
23.54 3.27b
Rubber-rotary instrument
18.96 3.06c
*Different superscript letters show significant differences (P<.05).
RESULTS
Mean Bond Strength (MPa)
Kolmogorov-Smirnov test). The Bonferroni test was used to evaluate the significantly different groups (a¼.05). Failure modes were observed with a stereomicroscope (Stereomicroscope; Wild M3B) and were classified as adhesive failure between cement and dentin, cohesive failure in cement, and mixed type of failure. To determine the surface texture, 1 specimen for every surface-cleaning method also was prepared for SEM analysis. The specimens were sectioned buccolingually with a slow-speed saw (Microcut; Metkon) under water cooling, as previously described. The sectioned specimens were placed in distilled water and subjected to ultrasonic cleaning in an ultrasonic unit for 10 minutes (BioSonic UC50; Coltène/ Whaledent). The specimens then were polished with 600-grit silicon carbide abrasive paper (Kovax Co), acid etched in 10% phosphoric acid (H3PO4) acid solution (Sigma-Aldrich Co) for 10 seconds, and rinsed in distilled water for 60 seconds. They then were placed in 5% sodium hypochlorite (NaOCl) solution (Sigma-Aldrich) and rinsed in distilled water. The conditioned specimens were coated with a thin layer of gold with a SC500 sputter coater (Polaron; VG Microtech) and photographed with an SEM (JSM 5600; JOEL). Additional specimens were prepared (n¼1 per group) to evaluate the effects of the surface treatment methods on the dentin surfaces at a microscopic level. An AFM (EasyScan 2 AFM; Nanosurf AG) was used to obtain 20 20mm 3-dimensional images of the surfaces, all located in the center of the specimens, for visual inspection. During the SEM analyses, the energy dispersive x-ray analysis (EDS) technique also was used to identify the elemental composition of the specimens on their surface for the Cont and MAPA groups.
40 35 30 25 20 15 10 5 0 Control
Microairborne- Desiccating particle abrasion agent
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Rubber-rotary instrument
Evaluated Groups
2 Mean bond strengths of groups.
Control Microairborneparticle abrasion Desiccating agent
Alcohol Rubber-rotary instrument 0
The microtensile bond strengths of specimens cleaned with different techniques were compared (Table II, Fig. 2).
Alcohol
20
40
Adhesive
60
80
Cohesive
100
120
Mixed
3 Failure modes of groups and percentages.
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4 A, Scanning electron microscope (SEM) image of microairborne-particle abrasion (MAPA) group (750 magnification). B, SEM image of control (Cont) group (750 magnification). C, SEM image of alcohol (Alco) group (750 magnification). D, SEM image of rubber-rotary instrument (RRI) group (750 magnification). E, SEM image of desiccating agent (DA) group (750 magnification). F, SEM image of microairborne-particle abrasion group (1000). Note aluminium oxide (Al2O3) particle on surface. The Cont, Alco, RRI, and DA groups displayed relatively smoother surfaces (Fig. 4B-E). When the 1000 magnification image of the MAPA group was evaluated, an aluminium oxide (Al2O3) particle embedded into the surface could be observed at the center of the image (Fig. 4F). AFM images indicated that MAPA displayed a different surface topography compared with the remainder of the groups (Fig. 5A). The projections on the dentin in the MAPA group after surface cleaning had rounder features than the projections in the remaining groups. The projections in the Cont group (Fig. 5B) were slightly rounder in the Alco (Fig. 5C) and DA groups
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(Fig. 5D). The RRI group also displayed a different surface structure than the other groups (Fig. 5E). The shape of the projections in the RRI group was different from that in the Cont, Alco, and DA groups. The elemental composition of the surfaces of the MAPA and Cont groups was analyzed and is displayed in Figure 6A and B.
DISCUSSION The null hypothesis of this study was rejected because significant differences were found between the bond strengths of the definitive restorations and the surface topography of the
dentin surfaces treated with a bonding agent when different surface-cleaning methods were used with the DP technique. Both the SEM and AFM analyses revealed a different surface topography for surfaces cleaned with the MAPA technique. The significantly higher bond strength of the composite resin achieved by the MAPA group could be attributed to the different surface texture. A positive relationship also may exist between increased surface area and increased mTBS values. Ozcan et al28 reported that airborneparticle abrasion improved the composite resin to composite resin bond strength. They attributed this result
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5 Atomic force microscopy images: A, Microairborne-particle abrasion (MAPA) group. B, Control (Cont) group. C, Alcohol (Alco) group. D, Desiccating agent (DA) group. E, Rubber-rotary instrument (RRI) group.
to the fact that 40% to 50% of the unreactive methacrylate groups were present after the composite resins had been light polymerized, which allowed for the adhesion of new resin layers as shown in previous studies.29,30 Similarly, in the present study, the bond strength was found to be better with airborneparticle abrasion, caused perhaps by the potential existence of unreactive methacrylate groups. In a similar study, Rodrigues et al31 compared the effects of airborne-particle abrasion with alumina particles or silica-modified alumina particles on the bond strength of repair composite resins and found that they were effective surface treatments for the repair of composite resin
restorations. The investigators observed similar mean surface roughness values with airborne-particle abrasion with aluminum oxide and silica coating, and attributed these results to the similar surface roughness pattern produced in both composite resins. Similarly, Chaiyabutr and Kois32 evaluated the in vitro bond strength of a self-adhesive luting cement by using 4 different techniques to remove surface contamination on dentin. Microairborne-particle abrasion was shown to provide a higher bond strength than the other techniques (hand instrument, a mixture of pumice and water). In a previous study, the effect of cleansing protocols on the bond strength of self-adhesive resin
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cement to dentin contaminated with a hemostatic agent was evaluated.33 In the mentioned study, the interim cement also was used before the contamination process. According to the results of the study, similar microairborne-particle abrasion significantly improved the bond strength of contaminated dentin. In addition, Santos et al34 showed that microairborne-particle abrasion produced significantly higher shear bond strength values than any other treatment groups (chlorhexidine pretreatment, and pumice application). Sarac et al35 tested the effectiveness of the DA for cleaning the dentin treated with interim cement before the application of resin cement. Similar to the results of
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Full scale counts: 1943 AI
2000
1500
1000
500
Au O
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
keV
A
Full scale counts: 1000 Si
1000 800 600
Au 400 200 0
AI O
Na
Au
K
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
keV
B
6 Energy dispersive x-ray analysis spectra: A, Microairborne-particle abrasion (MAPA) group. Note high Al presence. B, Control (Cont) group. Note high Si presence. Also O, Na, Al, K elements on dentin surface may be arise from bonding agent layer and from scanning electron microscope coating (Au). the present study, they also found the DA effective in removing the remnants of interim cement. In the present study, the Alco (3.27 MPa) and RRI (3.06 MPa) groups showed higher standard deviation (SD) values than those of the other groups. The RRI group was used with an operator, which may have caused uneven pressure on the specimen surfaces during application. The same higher SD seen in the Alco group may be related to ethyl and its variable ability to solve different remnants. Although the RRI group showed higher bond strength values than the control group, the difference was not
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significant. According to SEM micrographs, the RRI group showed shallow surface texture compared with the MAPA group. However, it can be seen that the RRI group clearly produced a surface texture with significant height differences among peaks. Therefore, the authors of the present study speculated that, due to the surface texture seen on SEM and AFM images, mTBS values of the RRI group did not increase. When the failure modes were evaluated, it was observed that the percentages of adhesive failures were high when the microtensile bond strength values were low. The percentages of
adhesive failures were low for the MAPA group. This result can be attributed to the high bond strength between the cement and the dentin surface, which was treated by using the DP technique and was cleaned by using the airborneparticle abrasion technique. These results were in agreement with the results of a previous study.32 The percentages of the adhesive failures were high for the Cont and RRI groups, in which the bond strength values were significantly lower than for the remainder of the groups. No cohesive failures were observed with the Cont group. The groups with high microtensile bond strength (MAPA, DA, Alco) had relatively high percentages of mixed failures. According to these results, all the surface-cleaning techniques tested, except for the RRI cleaning technique, increased the bond strength of the composite resin to dentin when they were compared with the Cont group. The evaluation of the failure modes was not done statistically and was only used to support the interpretation of the bond strength evaluation. In the SEM evaluation, the roughest surfaces were observed when the MAPA technique was used. Also, alumina particles embedded in the surface were seen particularly in the SEM micrographs of the MAPA method (Fig. 4F). Similarly, the energy dispersive x-ray analysis of the MAPA group revealed that some alumina particles were embedded into the surface in the MAPA group. The amount of aluminum observed in the Cont group and the MAPA group are displayed in Figure 6A and B, respectively. The Al2O3 airborne-particle abrasion seemed to explain the alumina particles on the surface. The alumina particles may enhance the bond strength of the composite resin, and the favorable bond strength of the MAPA group may be due to the alumina particles on the surface. The results of this in vitro study should be corroborated with in vivo studies. In addition, the results of this study are limited to the materials tested; a different bonding system may behave differently.
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Volume 112 Issue 4 CONCLUSION Within the limitations of this study, the following conclusions can be drawn. The surface-cleaning techniques, except for the RRI technique, increased the bond strength of cement to dentin; the highest bond strength for the cement among the groups was achieved with the MAPA technique; and the use of the MAPA technique displayed the roughest hybridized dentin surfaces.
REFERENCES 1. Garber DA, Goldstein RE. Impression and provisional restorations porcelain and composite inlays and onlays: esthetic posterior restorations. Chicago: Quintessence; 1994. p. 57-65. 2. Shillingburg HT, Sather DA, Wilson EL, Cain JR, Mitchell DL, Blanco LJ, et al. Provisional restorations. fundamentals of fixed prosthodontics. 4th ed. Chicago: Quintessence; 2012. p. 279-303. 3. Millstein PL, Nathanson D. Effects of temporary cementation on permanent cement retention to composite resin cores. J Prosthet Dent 1992;67:856-9. 4. Paul SJ, Scharer P. Effect of provisional cements on the bond strength of various adhesive bonding systems on dentine. J Oral Rehabil 1997;24:8-14. 5. Bachmann M, Paul SJ, Luthy H, Scharer P. Effect of cleaning dentine with soap and pumice on shear bond strength of dentine-bonding agents. J Oral Rehabil 1997;24:433-8. 6. al-Wazzan KA, al-Harbi AA, Hammad IA. The effect of eugenol-containing temporary cement on the bond strength of two resin composite core materials to dentin. J Prosthodont 1997;6:37-42. 7. Mojon P, Hawbolt EB, MacEntee MI. A comparison of two methods for removing zinc oxide-eugenol provisional cement. Int J Prosthodont 1992;5:78-84. 8. Watanabe EK, Yamashita A, Imai M, Yatani H, Suzuki K. Temporary cement remnants as an adhesion inhibiting factor in the interface between resin cements and bovine dentin. Int J Prosthodont 1997;10:440-52. 9. Watanabe EK, Yamashita A, Yatani H, Ishikawa K, Suzuki K. Improvement in the tensile bond strength between resin cement and dentin surfaces after temporary cement application. Int J Prosthodont 1998;11:203-11.
10. Aykent F, Usumez A, Ozturk AN, Yücel MT. Effect of provisional restorations on the final bond strengths of porcelain laminate veneers. J Oral Rehabil 2005;32:46-50. 11. Xie J, Powers JM, McGuckin RS. In vitro bond strength of two adhesives to enamel and dentin under normal and contaminated conditions. Dent Mater 1993;9:295-9. 12. Paul SJ, Scharer P. The dual bonding technique: a modified method to improve adhesive luting procedures. Int J Periodontics Restorative Dent 1997;17:536-45. 13. Magne P, Douglas WH. Porcelain veneers: dentin bonding optimization and biomimetic recovery of the crown. Int J Prosthodont 1999;12:111-21. 14. Dagostin A, Ferrari M. Effect of resin sealing of dentin on the bond strength of ceramic restorations. Dent Mater 2002;18:304-10. 15. Ozturk N, Aykent F. Dentin bond strengths of two ceramic inlay systems after cementation with three techniques and one bonding system. J Prosthet Dent 2003;89:275-81. 16. Hu J, Zhu Q. Effect of immediate dentin sealing on preventive treatment for post cementation hypersensitivity. Int J Prosthodont 2010;23:49-52. 17. Brännström M. The effect of dentin desiccation and aspirated odontoblasts on the pulp. J Prosthet Dent 1968;20:165-71. 18. Suzuki S, Cox CF, White KC. Pulpal response after complete crown preparation, dentinal sealing, and provisional restoration. Quintessence Int 1994;25:477-85. 19. Pashley DH, Matthews WG, Zhang Y, Johnson M. Fluid shifts across human dentine in vitro in response to hydrodynamic stimuli. Arch Oral Biol 1997;41:1065-72. 20. Lundy T, Stanley HR. Correlation of pulpal histopathology and clinical symptoms in human teeth subjected to experimental irritation. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1969;27:187-201. 21. Nagaoka S, Miyazaki Y, Liu HJ, Iwamoto Y, Kitano M, Kawagoe M. Bacterial invasion into dentinal tubules of human vital and non-vital teeth. J Endod 1995;21:70-3. 22. Magne P, Belser U. Restorations in the anterior dentition: a biomimetic approachQuintessence; 2002. p. 358e62. 23. Coelho PG, Calamia C, Harsono M, Thompson VP, Silva NA. Laboratory and FEA evaluation of dentin-to-composite bonding as a function of adhesive layer thickness. Dent Mater 2008;24:1297-303. 24. Bertschinger C, Paul SJ, Luthy H, Scharer P. Dual application of dentin bonding agents: effect on bond strength. Am J Dent 1996; 9:115-9.
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25. Erkut S, Kucukesmen HC, Eminkahyagil N, Imirzalioglu P, Karabulut E. Influence of previous provisional cementation on the bond strength between two definitive resin-based luting and dentin bonding agents and human dentin. Oper Dent 2007;32:84-93. 26. Magne P, So WS, Cascione D. Immediate dentin sealing supports delayed restoration placement. J Prosthet Dent 2007;98:166-74. 27. Magne P, Kim TH, Cascione D, Donovan TE. Immediate dentin sealing improves bond strength of indirect restorations. J Prosthet Dent 2005;94:511-9. 28. Ozcan M, Barbosab SH, Melob RM, Galhanob GAP, Bottinob MA. Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions. Dent Mater 2007;23:1276-82. 29. Vankerckhoven H, Lambrechts P, van Beylen M, Davidson CL, Vanherle G. Unreacted methacrylate groups on the surfaces of composite resins. J Dent Res 1982;61:791-5. 30. Sau CW, Oh GS, Koh H, Chee CS, Lim CC. Shear bond strength of repaired composite resins using a hybrid composite resin. Oper Dent 1999;24:156-61. 31. Rodrigues SA Jr, Ferracane JL, Della Bona A. Influence of surface treatments on the bond strength of repaired resin composite restorative materials. Dent Mater 2009;25:442-51. 32. Chaiyabutr Y, Kois JC. The effects of tooth preparation cleansing protocols on the bond strength of self-adhesive resin luting cement to contaminated dentin. Oper Dent 2008; 33:556-63. 33. Chaiyabutr Y, Kois JC. The effect of toothpreparation cleansing protocol on the bond strength of self-adhesive resin cement to dentin contaminated with a hemostatic agent. Oper Dent 2011;36:18-26. 34. Santos MJ, Bapoo H, Rizkalla AS, Santos GC. Effect of dentin-cleaning techniques on the shear bond strength of self-adhesive resin luting cement to dentin. Oper Dent 2011;36:512-20. 35. Sarac D, Bulucu B, Sarac Y, Kulunk S. The effect of dentin-cleaning agents on resin cement bond strength to dentin. J Am Dent Assoc 2008;139:751-8. Corresponding author: Dr Burak Yilmaz The Ohio State University College of Dentistry Division of Restorative, Prosthetic and Primary Care Dentistry Columbus, OH 43210-1267 E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
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Clinical Implications When using a dual-polymerizing technique that involve a bonding agent, clinicians may prefer to clean dentin surfaces with microairborne-particle abrasion after removing interim restorations.
a
Associate Professor, Department of Prosthetic Dentistry, Faculty of Dentistry, Baskent University, Ankara, Turkey. Assistant Professor, Division of Restorative and Prosthetic Dentistry, The Ohio State University College of Dentistry. c Associate Professor, Department of Prosthetic Dentistry, Faculty of Dentistry, Izmir Katip Celebi University, Izmir, Turkey. d Assistant Professor, Department of Pediatric Dentistry, Faculty of Dentistry, Süleyman Demirel University, Isparta, Turkey. e Private practice, Antalya, Turkey. f Fellow, Department of Prosthetic Dentistry, Faculty of Dentistry, Baskent University, Ankara, Turkey. b
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Volume 112 Issue 4 When adhesive restorations are placed in a single visit, it is relatively easy to provide a contaminant-free bonding surface such as prepared dentin. However, restorations that require multiple visits need interim prostheses1,2 that are luted with an interim luting agent. Results of studies have provided information regarding the effect of interim luting agent remnants that are difficult to remove even with magnification.3-6 Results of these studies also showed a decrease in the bond strength between the dentin and the prosthesis after an interim restoration when different cleansing methods were used.5,7 Several studies have reported the difficulty of removing interim cement from the prepared tooth surface and the negative impact of the definitive cements to the tooth surface on the bond strength.3-6,8-11 The dual-polymerizing (DP) technique is the application of dentin bonding agents on the prepared tooth surfaces immediately after tooth preparation and the application of the same agent before definitive cementation of the indirect prosthesis.12-15 The aim of the DP technique is to minimize postoperative sensitivity,16-21 to seal the exposed dentinal tubules immediately after tooth preparation, to enhance the bond strength, and to minimize the negative effects of interim cements. In the conventional bonding technique, partial disruption between the hybrid layer and the overlying resin is uncommon. In the DP technique, longer resin tags are formed, and no discontinuity exists in the dentin-resin interface or between the prepolymerized adhesive and the luting composite resin. In the conventional technique, the luting space is mostly occupied by luting composite resin, and unpolymerized dentin adhesive is thinned out by more viscous composite resin when the restoration is inserted. In the DP technique, the luting space is thicker because it is composed of 2 distinct layers: the prepolymerized adhesive and the luting composite resin.22 In a finite element analysis study, Coelho et al23 stated that, from a clinical standpoint,
adhesive layer shrinkage due to thicker adhesive layers should be avoided because it will increase stress concentration regardless of tension and compression at the adhesive layers and will introduce shearing components between both composite resin and dentin bonding interfaces. They reported that the effectiveness of the DP technique should be confirmed with long-term clinical studies.23
Table I.
In the DP technique, as opposed to the conventional method, the interim cement is in contact with a hybridized dentin surface coated with a polymeric layer that has different surface properties than dentin.12,24 Several in vitro studies have reported enhanced bond strength with the DP technique through the elimination of the effects of interim cements on the dentin surfaces.25-27 Even though the application steps of
Test groups
Groups Control 1. Clean with water and fluoride-free pumice 2. Wash and dry with oil-free air 3. Etch and dry 4. Apply bonding agent and light polymerize 5. Apply composite resin and light polymerize Microairborne-particle abrading 1. Clean with water and fluoride-free pumice 2. Wash and dry with oil-free air 3. Airborne-particle abrade 4. Dry with oil-free air and alcohol 5. Apply bonding agent, light polymerize 6. Apply composite resin and light polymerize Alcohol 1. Clean with water and fluoride-free pumice 2. Rinse and dry with oil-free air 3. Wipe with alcohol and dry 4. Etch and dry 5. Apply bonding agent and light polymerize 6. Apply composite resin and light polymerize Desiccating agent 1. Clean with water and fluoride-free pumice 2. Rinse and dry with oil-free air 3. Wipe with desiccating agent and dry 4. Etch, rinse, and dry 5. Apply bonding agent and light polymerize 6. Apply composite resin and light polymerize Rubber-rotary instrument
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1. Remove the interim luting agent with rubber-rotary instrument 2. Rinse and dry with oil-free compressed air 3. Etch, rinse, and dry 4. Apply bonding agent and light polymerize 5. Apply composite resin and light polymerize
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October 2014 the DP technique are similar in different studies, different techniques have been reported for cleaning the surface of hybridized dentin. The purpose of this study was to investigate the effects of different surfacecleaning techniques on the bond strength of the definitive prosthesis and surface topography of the prepared tooth surfaces when the DP technique is used. The bond strength was evaluated by using microtensile bond strength tests. Scanning electron microscopy (SEM) was used to evaluate the interfacial layers in different bonding techniques and the resin-based luting agents. The atomic force microscopy (AFM) technique was used to observe the tooth surfaces after the surfaces were cleaned with different techniques after interim prosthesis removal and before definitive cementation. The null hypothesis of this study was that no differences would be found between the effects of different surface-cleaning methods with the DP technique on the bond strength of the composite resin restorations and the surface topography of surfaces treated with a bonding agent.
951 with standard mode (Elipar Freelight LED 2; 3M ESPE). Noneugenol interim cement (Rely X Temp NE; 3M ESPE) then was applied to the ground surface of the teeth. The teeth were stored in distilled water at 37 C for 24 hours. After the excess interim cement had been cleaned from the teeth with water and fluoride-free pumice, the surfaces were washed and dried with oil-free compressed air. Twenty-five teeth were assigned to 5 groups (n¼5 per group) according to the method of surface cleaning (Table I). The groups were as follows: control (Cont), microairborneparticle abrasion (MAPA), alcohol (Alco), desiccating agent (DA), and rubber-rotary instrument (RRI). After the teeth had been dried with oil-free compressed air, the surfaces in the Cont group were not treated with anything. Once the teeth surfaces were cleaned, the same bonding agent (Single Bond 2; 3M ESPE) was reapplied on the surface of the teeth and polymerized as previously described. A 5-mmthick composite resin layer, cylindrical in shape and perpendicular to the dentin flat surface, then was built up incrementally (Clearfil Ap-x Restorative
System; Kuraray) on each tooth. All composite resin foundations were light polymerized with the light-emitting diode in standard mode (Elipar Freelight LED 2). While the microtensile bond strength (mTBS) test specimens were being prepared, the specimens were stored in distilled water at 37 C for 72 hours. Each was then serially sectioned vertically into rectangular beams (1.10 0.10 1.10 0.10 mm) with a slow-speed diamond wafering blade (Ernst Leitz GMBH) (Fig. 1). Cross-sectional areas were measured with digital calipers. Six centrally located beams from each tooth were used for the microtensile bond strength (mTBS) test (n¼30 per group). The specimens were attached to a microtensile tester (Bisco) with cyanoacrylate resin (Zapit; DVA) and subjected to microtensile testing at a crosshead speed of 0.5 mm/min. until they were debonded. The values of the variables were normally distributed, and the variance of each group was equal; therefore, the bond strength differences were statistically analyzed by using the repeated measures of ANOVA (1-sample
MATERIAL AND METHODS The project was approved by the institutional review board of Karadeniz Technical University, Trabzon, Turkey. Twenty-five caries-free and restorationfree human molars extracted from individuals between 22 and 50 years of age were used for this study (80% power [type II error]). The teeth were stored in a 0.5% chloramine solution at 4 C for up to 1 month after extraction. The soft tissues were removed with a scaler (Scaler, H6/H7; Hu-Friedy). Each tooth was wet ground occlusally with silicon carbide abrasive up to paper no. 1000 (FEPA, Struers RotoPol 11; Struers A/S). The occlusal surfaces were ground until all enamel islands were removed and only dentin was exposed. A bonding agent (Single Bond 2; 3M ESPE) was first applied on the surface of the teeth with a brush and was light polymerized with a solid-state, light-emitting diode polymerizing device
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1 Schematic, showing specimen preparation.
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Volume 112 Issue 4 The MAPA group had the highest bond strength, and the differences between the MAPA group and the remainder of the groups were statistically significant (P<.05). The DA group displayed the second highest bond strength, and the difference between the DA-RRI and DACont groups was statistically significant (P<.05). The third highest bond strength was seen in the Alco group, and the bond strength of the Alco group was significantly higher than the
bond strength of the RRI and the Cont groups (P<.05). The RRI group had a higher bond strength than the Cont group; however, the difference was not statistically significant (P>.05). The failure modes were evaluated under SEM, and the distribution of the failure modes is displayed in Figure 3. In the SEM evaluation, the 750 magnification of the images was taken into consideration. The MAPA group displayed the roughest surface (Fig. 4A).
Means and standard deviations (SD) for microtensile bond strength (n¼30)
Table II.
Mean (SD) microtensile bond strength (MPa)*
Groups Control
16.69 2.56c
Microairborne-particle abrasion
32.24 2.7a
Desiccating agent
24.77 1.73b
Alcohol
23.54 3.27b
Rubber-rotary instrument
18.96 3.06c
*Different superscript letters show significant differences (P<.05).
RESULTS
Mean Bond Strength (MPa)
Kolmogorov-Smirnov test). The Bonferroni test was used to evaluate the significantly different groups (a¼.05). Failure modes were observed with a stereomicroscope (Stereomicroscope; Wild M3B) and were classified as adhesive failure between cement and dentin, cohesive failure in cement, and mixed type of failure. To determine the surface texture, 1 specimen for every surface-cleaning method also was prepared for SEM analysis. The specimens were sectioned buccolingually with a slow-speed saw (Microcut; Metkon) under water cooling, as previously described. The sectioned specimens were placed in distilled water and subjected to ultrasonic cleaning in an ultrasonic unit for 10 minutes (BioSonic UC50; Coltène/ Whaledent). The specimens then were polished with 600-grit silicon carbide abrasive paper (Kovax Co), acid etched in 10% phosphoric acid (H3PO4) acid solution (Sigma-Aldrich Co) for 10 seconds, and rinsed in distilled water for 60 seconds. They then were placed in 5% sodium hypochlorite (NaOCl) solution (Sigma-Aldrich) and rinsed in distilled water. The conditioned specimens were coated with a thin layer of gold with a SC500 sputter coater (Polaron; VG Microtech) and photographed with an SEM (JSM 5600; JOEL). Additional specimens were prepared (n¼1 per group) to evaluate the effects of the surface treatment methods on the dentin surfaces at a microscopic level. An AFM (EasyScan 2 AFM; Nanosurf AG) was used to obtain 20 20mm 3-dimensional images of the surfaces, all located in the center of the specimens, for visual inspection. During the SEM analyses, the energy dispersive x-ray analysis (EDS) technique also was used to identify the elemental composition of the specimens on their surface for the Cont and MAPA groups.
40 35 30 25 20 15 10 5 0 Control
Microairborne- Desiccating particle abrasion agent
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Rubber-rotary instrument
Evaluated Groups
2 Mean bond strengths of groups.
Control Microairborneparticle abrasion Desiccating agent
Alcohol Rubber-rotary instrument 0
The microtensile bond strengths of specimens cleaned with different techniques were compared (Table II, Fig. 2).
Alcohol
20
40
Adhesive
60
80
Cohesive
100
120
Mixed
3 Failure modes of groups and percentages.
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4 A, Scanning electron microscope (SEM) image of microairborne-particle abrasion (MAPA) group (750 magnification). B, SEM image of control (Cont) group (750 magnification). C, SEM image of alcohol (Alco) group (750 magnification). D, SEM image of rubber-rotary instrument (RRI) group (750 magnification). E, SEM image of desiccating agent (DA) group (750 magnification). F, SEM image of microairborne-particle abrasion group (1000). Note aluminium oxide (Al2O3) particle on surface. The Cont, Alco, RRI, and DA groups displayed relatively smoother surfaces (Fig. 4B-E). When the 1000 magnification image of the MAPA group was evaluated, an aluminium oxide (Al2O3) particle embedded into the surface could be observed at the center of the image (Fig. 4F). AFM images indicated that MAPA displayed a different surface topography compared with the remainder of the groups (Fig. 5A). The projections on the dentin in the MAPA group after surface cleaning had rounder features than the projections in the remaining groups. The projections in the Cont group (Fig. 5B) were slightly rounder in the Alco (Fig. 5C) and DA groups
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(Fig. 5D). The RRI group also displayed a different surface structure than the other groups (Fig. 5E). The shape of the projections in the RRI group was different from that in the Cont, Alco, and DA groups. The elemental composition of the surfaces of the MAPA and Cont groups was analyzed and is displayed in Figure 6A and B.
DISCUSSION The null hypothesis of this study was rejected because significant differences were found between the bond strengths of the definitive restorations and the surface topography of the
dentin surfaces treated with a bonding agent when different surface-cleaning methods were used with the DP technique. Both the SEM and AFM analyses revealed a different surface topography for surfaces cleaned with the MAPA technique. The significantly higher bond strength of the composite resin achieved by the MAPA group could be attributed to the different surface texture. A positive relationship also may exist between increased surface area and increased mTBS values. Ozcan et al28 reported that airborneparticle abrasion improved the composite resin to composite resin bond strength. They attributed this result
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5 Atomic force microscopy images: A, Microairborne-particle abrasion (MAPA) group. B, Control (Cont) group. C, Alcohol (Alco) group. D, Desiccating agent (DA) group. E, Rubber-rotary instrument (RRI) group.
to the fact that 40% to 50% of the unreactive methacrylate groups were present after the composite resins had been light polymerized, which allowed for the adhesion of new resin layers as shown in previous studies.29,30 Similarly, in the present study, the bond strength was found to be better with airborneparticle abrasion, caused perhaps by the potential existence of unreactive methacrylate groups. In a similar study, Rodrigues et al31 compared the effects of airborne-particle abrasion with alumina particles or silica-modified alumina particles on the bond strength of repair composite resins and found that they were effective surface treatments for the repair of composite resin
restorations. The investigators observed similar mean surface roughness values with airborne-particle abrasion with aluminum oxide and silica coating, and attributed these results to the similar surface roughness pattern produced in both composite resins. Similarly, Chaiyabutr and Kois32 evaluated the in vitro bond strength of a self-adhesive luting cement by using 4 different techniques to remove surface contamination on dentin. Microairborne-particle abrasion was shown to provide a higher bond strength than the other techniques (hand instrument, a mixture of pumice and water). In a previous study, the effect of cleansing protocols on the bond strength of self-adhesive resin
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cement to dentin contaminated with a hemostatic agent was evaluated.33 In the mentioned study, the interim cement also was used before the contamination process. According to the results of the study, similar microairborne-particle abrasion significantly improved the bond strength of contaminated dentin. In addition, Santos et al34 showed that microairborne-particle abrasion produced significantly higher shear bond strength values than any other treatment groups (chlorhexidine pretreatment, and pumice application). Sarac et al35 tested the effectiveness of the DA for cleaning the dentin treated with interim cement before the application of resin cement. Similar to the results of
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Full scale counts: 1943 AI
2000
1500
1000
500
Au O
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
keV
A
Full scale counts: 1000 Si
1000 800 600
Au 400 200 0
AI O
Na
Au
K
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5
keV
B
6 Energy dispersive x-ray analysis spectra: A, Microairborne-particle abrasion (MAPA) group. Note high Al presence. B, Control (Cont) group. Note high Si presence. Also O, Na, Al, K elements on dentin surface may be arise from bonding agent layer and from scanning electron microscope coating (Au). the present study, they also found the DA effective in removing the remnants of interim cement. In the present study, the Alco (3.27 MPa) and RRI (3.06 MPa) groups showed higher standard deviation (SD) values than those of the other groups. The RRI group was used with an operator, which may have caused uneven pressure on the specimen surfaces during application. The same higher SD seen in the Alco group may be related to ethyl and its variable ability to solve different remnants. Although the RRI group showed higher bond strength values than the control group, the difference was not
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significant. According to SEM micrographs, the RRI group showed shallow surface texture compared with the MAPA group. However, it can be seen that the RRI group clearly produced a surface texture with significant height differences among peaks. Therefore, the authors of the present study speculated that, due to the surface texture seen on SEM and AFM images, mTBS values of the RRI group did not increase. When the failure modes were evaluated, it was observed that the percentages of adhesive failures were high when the microtensile bond strength values were low. The percentages of
adhesive failures were low for the MAPA group. This result can be attributed to the high bond strength between the cement and the dentin surface, which was treated by using the DP technique and was cleaned by using the airborneparticle abrasion technique. These results were in agreement with the results of a previous study.32 The percentages of the adhesive failures were high for the Cont and RRI groups, in which the bond strength values were significantly lower than for the remainder of the groups. No cohesive failures were observed with the Cont group. The groups with high microtensile bond strength (MAPA, DA, Alco) had relatively high percentages of mixed failures. According to these results, all the surface-cleaning techniques tested, except for the RRI cleaning technique, increased the bond strength of the composite resin to dentin when they were compared with the Cont group. The evaluation of the failure modes was not done statistically and was only used to support the interpretation of the bond strength evaluation. In the SEM evaluation, the roughest surfaces were observed when the MAPA technique was used. Also, alumina particles embedded in the surface were seen particularly in the SEM micrographs of the MAPA method (Fig. 4F). Similarly, the energy dispersive x-ray analysis of the MAPA group revealed that some alumina particles were embedded into the surface in the MAPA group. The amount of aluminum observed in the Cont group and the MAPA group are displayed in Figure 6A and B, respectively. The Al2O3 airborne-particle abrasion seemed to explain the alumina particles on the surface. The alumina particles may enhance the bond strength of the composite resin, and the favorable bond strength of the MAPA group may be due to the alumina particles on the surface. The results of this in vitro study should be corroborated with in vivo studies. In addition, the results of this study are limited to the materials tested; a different bonding system may behave differently.
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Volume 112 Issue 4 CONCLUSION Within the limitations of this study, the following conclusions can be drawn. The surface-cleaning techniques, except for the RRI technique, increased the bond strength of cement to dentin; the highest bond strength for the cement among the groups was achieved with the MAPA technique; and the use of the MAPA technique displayed the roughest hybridized dentin surfaces.
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25. Erkut S, Kucukesmen HC, Eminkahyagil N, Imirzalioglu P, Karabulut E. Influence of previous provisional cementation on the bond strength between two definitive resin-based luting and dentin bonding agents and human dentin. Oper Dent 2007;32:84-93. 26. Magne P, So WS, Cascione D. Immediate dentin sealing supports delayed restoration placement. J Prosthet Dent 2007;98:166-74. 27. Magne P, Kim TH, Cascione D, Donovan TE. Immediate dentin sealing improves bond strength of indirect restorations. J Prosthet Dent 2005;94:511-9. 28. Ozcan M, Barbosab SH, Melob RM, Galhanob GAP, Bottinob MA. Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions. Dent Mater 2007;23:1276-82. 29. Vankerckhoven H, Lambrechts P, van Beylen M, Davidson CL, Vanherle G. Unreacted methacrylate groups on the surfaces of composite resins. J Dent Res 1982;61:791-5. 30. Sau CW, Oh GS, Koh H, Chee CS, Lim CC. Shear bond strength of repaired composite resins using a hybrid composite resin. Oper Dent 1999;24:156-61. 31. Rodrigues SA Jr, Ferracane JL, Della Bona A. Influence of surface treatments on the bond strength of repaired resin composite restorative materials. Dent Mater 2009;25:442-51. 32. Chaiyabutr Y, Kois JC. The effects of tooth preparation cleansing protocols on the bond strength of self-adhesive resin luting cement to contaminated dentin. Oper Dent 2008; 33:556-63. 33. Chaiyabutr Y, Kois JC. The effect of toothpreparation cleansing protocol on the bond strength of self-adhesive resin cement to dentin contaminated with a hemostatic agent. Oper Dent 2011;36:18-26. 34. Santos MJ, Bapoo H, Rizkalla AS, Santos GC. Effect of dentin-cleaning techniques on the shear bond strength of self-adhesive resin luting cement to dentin. Oper Dent 2011;36:512-20. 35. Sarac D, Bulucu B, Sarac Y, Kulunk S. The effect of dentin-cleaning agents on resin cement bond strength to dentin. J Am Dent Assoc 2008;139:751-8. Corresponding author: Dr Burak Yilmaz The Ohio State University College of Dentistry Division of Restorative, Prosthetic and Primary Care Dentistry Columbus, OH 43210-1267 E-mail: [email protected] Copyright ª 2014 by the Editorial Council for The Journal of Prosthetic Dentistry.
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