Year : 2010 | Volume
: 21 | Issue : 2 | Page : 238--243
The influence of silane evaporation procedures on microtensile bond strength between a dental ceramic and a resin cement
Carolina Nemesio de Barros Pereira, Vicente Tadeu Lopes Buono, Joao Mauricio Lima de Figueiredo Mota
Department of Restorative Dentistry, Faculty of Dentistry, Metallurgical and Materials Engineering, School of Engineering, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
Vicente Tadeu Lopes Buono
Department of Restorative Dentistry, Faculty of Dentistry, Metallurgical and Materials Engineering, School of Engineering, Federal University of Minas Gerais, Belo Horizonte, MG,
Aim: To assess the influence of silane evaporation procedures on bond strength between a dental ceramic and a chemically activated resin cement.
Materials and Methods: Eighteen blocks (6 mm Χ 14 mm Χ 14 mm) of ceramic IPS Empress 2 were cemented (C and B) to composite resin (InTen-S) blocks using a chemical adhesive system (Lok). Six groups were analyzed, each with three blocks divided according to ceramic surface treatment: two control groups (no treatment, NT; 10% hydrofluoric acid plus silane Monobond-S dried at room temperature, HFS); the other four groups comprised different evaporation patterns (silane rinsed and dried at room temperature, SRT; silane rinsed in boiling water and dried as before, SBRT; silane rinsed with boiling water and heat dried at 50°C, SBH; silane dried at 50 ± 5°C, rinsed in boiling water and dried at room temperature, SHBRT). The cemented blocks were sectioned to obtain specimens for microtensile test 7 days after cementation and were stored in water for 30 days prior to testing. Fracture patterns were analyzed by optical and scanning electron microscopy.
Statistics and Results: All blocks of NT debonded during sectioning. One way ANOVA tests showed higher bond strengths for HFS than for the other groups. SBRT and SBH were statistically similar, with higher bond strengths than SRT and SHBRT. Failures were 100% adhesive in SRT and SHBRT. Cohesive failures within the «DQ»adhesive zone«DQ» were detected in HFS (30%), SBRT (24%) and SBH (40%).
Conclusion: Silane treatment enhanced bond strength in all conditions evaluated, showing best results with HF etching.
|How to cite this article:|
Pereira CN, Buono VT, Mota JL. The influence of silane evaporation procedures on microtensile bond strength between a dental ceramic and a resin cement.Indian J Dent Res 2010;21:238-243
|How to cite this URL:|
Pereira CN, Buono VT, Mota JL. The influence of silane evaporation procedures on microtensile bond strength between a dental ceramic and a resin cement. Indian J Dent Res [serial online] 2010 [cited 2021 May 13 ];21:238-243
Available from: https://www.ijdr.in/text.asp?2010/21/2/238/66645
Adhesive cementation of ceramic restoration allows a better distribution of masticatory loads, decreasing the risk of restoration fracture.  In addition, resin cement is less soluble than conventional cement and can be used with greater thickness without the loss of mechanical properties.  The cement adhesion protocol to the dental structure is already well known. ,, The inherent problem is the interface between resin cement and the ceramic restoration's inner surface. The success of the treatment of such surface using selective dissolution with acid or abrasion with airborne particles is determined by the ceramic's composition and manufacturing process. ,, Generally, chemical treatment of the ceramic surface with a silane coupling agent is suggested as a protocol for cementation of a ceramic restoration. ,
Abrading with aluminum oxide particles is a surface treatment recommended to produce microretention on feldspathic ceramic and on ceramics reinforced with leucite or lithium, but this procedure can lead to a loss of restoration margins.  Ammonia bifluoride and acidulate phosphate fluoride are known to produce etching patterns that have proven to be less effective than hydrofluoric acid (HF) for ceramic conditioning. ,,, However, the hazards in the clinical use of HF are well known. ,
Silane is used in composite resin manufacturing as a coupling agent between the organic matrix to the inorganic phase. Silane agents applied on ceramics, whether previously treated or not, tend to enhance cementation strength. ,, The main reason points to the increased wetting ability, favouring chemical union between the adhesive system or resin cement and the ceramic surface.  Some authors have reported higher bond strengths after silane application when associated with surface conditioning using HF, ,, whereas others have observed equivalent results with or without the previous mechanical treatment of the ceramic surface. ,,
According to a previous study,  three layers can be identified on the surface of silanized ceramic after drying: an outer layer adsorbed to the glass matrix, which can be removed by organic solvents or by water at room temperature; a second layer with oligomers linked by siloxane bridges, which can be removed by hot water; and a third layer, closer to the glass surface, showing cross-linking, which in turn more uniform and more stable than the others. As this final layer is effective in increasing the bond between the ceramic and resin, the detachment removal of the external silane layers is thought to enhance bond strength.
The study of adhesiveness between resin cement and ceramic is not an easy task. Shear tests induce bending failures instead of sliding patterns. ,, Because tensile tests induce uniform stress patterns, they tend to be more appropriate in assessing adhesive failures. Recent reports indicate that microtensile tests are the best choice to achieve more reliable bond strength values and point to the fact that microtensile test specimens reveal small adhesive areas and less surface flaws. ,, However, it is important to observe that finite element analysis has shown the presence of nonuniaxial loads on microtensile test specimens when these are attached to the lateral sides rather than to the top and bottom ends of the specimen.  The purpose of the present work was to evaluate the relationship between different silane evaporation patterns applied over IPS Empress 2 (Ivoclar Vivadent) and the bond strength between the surface-treated ceramic and a chemically activated resin cement.
Materials and Methods
Eighteen lithium disilicate ceramic blocks (6 mm x 14 mm x 14 mm) (IPS Empress 2, Ivoclar Vivadent, Schaan, Liechtenstein) were hot pressed according to the manufacturer's recommendations. The same number of composite resin blocks (InTen-S, Ivoclar Vivadent), built in 2-mm-thick increments, light polymerized for 40 s, light intensity of 450 mW/cm 2 , were prepared in a polivinylsiloxane soft putty mold (Adsil, Vigodent, Rio de Janeiro, RJ, Brazil). One end surface of each ceramic and resin block was submitted to abrasion using #240-320 SiC paper under water irrigation (Knuth-Rotor-3, Struers, Ballerup, Denmark). All blocks were ultrasonically cleaned and stored in dry plastic containers until bonding.
Six groups were analyzed, each with three ceramic and three resin blocks; two were control groups, while in the other four groups different evaporation patterns were employed. Silane application (Monobond-S, Ivoclar Vivadent) was standardized, i.e., it was brushed on the test surface using a Microbrush (SDI, Bayswater, Victoria, Australia). For heat drying, a dental kiln (Odontobrαs, Ribeirγo Preto, SP, Brazil) was used. The control groups were defined as follows: NT, negative control, surface polishing only, no silane treatment; HFS, positive control, a 10% HF applied to the polished ceramic surface for 1 min, rinsed for 1 min, dried at room temperature for 3 min, followed by silane application and allowed to dry at room temperature for 3 min. The four experimental groups were defined according to the following procedures, applied directly on the polished ceramic surface: SRT, silane application, surface allowed to dry at room temperature for 3 min followed by rinsing under running water for 5 s and drying at room temperature; SBRT, silane applied and dried as before, rinsed with boiling water for 5 s and dried as before; SBH, silane applied and dried as before, rinsed with boiling water for 5 s and dried at 50 ± 5°C for 3 min; SHBRT, silane applied as before, dried at 50 ± 5°C for 3 min, rinsed with boiling water for 5 s and dried at room temperature for 3 min.
Secondary electron images taken by scanning electron microscopy (SEM, Jeol JSM 6360LV, Tokyo, Japan) were used to compare silane adsorption patterns in polished ceramic specimens without acid treatment, prepared specifically for SEM examination; thus, different from the negative controls.
Each ceramic block was bonded to a resin block with the same surface treatment as that of the corresponding ceramic, except in HFS, whose corresponding resin block surface was treated with phosphoric acid. A chemically activated adhesive layer (Lok, SDI, Bayswater, Victoria, Australia) was applied according to the manufacturer instructions. A new brush was used for each ceramic or resin block and the excess adhesive was removed using absorbent paper. C and B (Bisco, Shaumburg, IL, USA) resin cement base and catalyst, equal parts per volume, were dispensed, mixed for 15 s and applied in a thin layer on the ceramic surface, which was then bonded to the corresponding resin block. The resin cement polymerized under a 100 gf load for 5 min. The bonded blocks were stored in water at room temperature for 7 days.
Cemented blocks were glued to a plate using SuperBonder Gel (Loctite, Itapevi, SP, Brazil) and mounted in the sectioning machine (Isomet 1000, Buehler, Lake Bluff, IL, USA). Cuts were performed using a slow-speed diamond wheel saw (Buehler Diamond Blade, #11.4254, 102 mm x 0.3 mm), producing slabs of approximately 2.0 mm in thickness. Outer slabs were eliminated to avoid specimens with excess cement. Each slab was rotated 90° and attached to the same device using a compound tracing stick (Godibar stick, Lysanda, Sγo Paulo, SP, Brazil) for final cuts of testing bars with 2.0 mm x 2.0 mm cross-sections. Forty-five bars per group were then stored in water at room temperature for 30 days before testing. Specimen dimensions were measured using a digital micrometer with 0.01 mm resolution (Mitutoyo, Tokyo, Japan).
Microtensile tests were performed at a crosshead speed of 0.5 mm/min in a universal testing machine (Instron 5869, Norwood, MA, USA) using a 5 kN load cell. A special device was designed to clamp the specimens by their ends with an articulated upper grip to improve load alignment, as shown in [Figure 1]. To connect the specimen to the grips, two brass tubes were machined for each bar tested. The tubes were 3 mm in diameter, with a 0.35-mm-thick wall, and 15 mm long. A hole, 1.6 mm in diameter, was made at one end of each tube so as to attach it to the grip with a coupling pin. The resin extremity of the test bar was glued (SuperBonder Gel, Loctite, Itapevi, SP, Brazil, followed by application of accelerator ZIP KICKER, Loctite, Itapevi, SP, Brazil) to the nonperforated extremity of a brass tube, which was then attached to the upper grip of the test machine through the coupling pin. Another tube was attached to the lower grip and glued, as before, to the ceramic end of the specimen after the upper grip had been lowered for positioning. After applying the polymerizing accelerator for 4 min, the bar was loaded until failure.
Fracture surfaces of all test specimens were examined under optical microscope (Wild M8, Heerbrugg, Switzerland) at 50Χ magnification. Fracture patterns were classified as follows: adhesive (A), occurring predominantly between adhesive and resin or adhesive and ceramic substrates and cohesive (C), taking place predominantly within the resin cement layer. Secondary electron images of selected fracture surfaces were also recorded by SEM for illustration purposes.
[Figure 2] shows secondary electron images obtained by SEM, characterizing the appearance of ceramic surfaces polished as described (A), and then submitted to the silane treatments defined as SRT (B), SBRT (C), SBH (D) and SHBRT (E). Qualitatively, features were sharper for the polished surface (A) and for the surface treated according to the SHBRT sequence (E).
All specimens of the negative control group NT (without surface treatment) were disrupted during the sectioning procedure, and the value of bond strength for this group was considered to be equal to zero. [Table 1] shows the mean values of bond strength for the surface treatments assessed. When pairs of groups were compared using one-way ANOVA (α=0.05), statistically significant differences were found among all pairs, except for the groups SRT and SHBRT and SBRT and SBH. Mean values of bond strength were lower for the first two groups (SRT and SHBRT) and higher for the last two (SBRT and SBH), while the highest values were those for the positive control group, HFS.
During microtensile tests, all fractures occurred within the "adhesion zone," defined as the region comprising of the adhesive, the treated ceramic surface, the resin cement and the region between the adhesive and the treated composite resin surface. Failure pattern analysis by optical microscopy showed adhesive failure in all the specimen of groups SRT and SHBRT, in 76% of the specimens of SBRT, 70% of the HFS and 60% of the SBH. All cohesive failures occurred within the resin cement, and the amount of cement on the fracture surface was higher for the specimens of groups HFS and SBH, while in the SBRT group, edge fractures were the most common pattern. Adhesive failures were further identified by observing the appearance of lines left on the fractured surface. The images shown in [Figure 3] illustrate this point: negative relief indicated a ceramic or resin surface [Figure 3]A, while a positive relief was associated with the adhesive or cement surface [Figure 3]B. Conversely, cohesive failures showed different amounts of resin cement structure in each substrate of the sample, as illustrated in [Figure 4] A and B.
It has been reported that silane treatment improves bond strength between IPS Empress 2 and dual-cure resin cement, regardless of previous conditioning with HF or airborne-particle-abrasion treatment.  Other authors  have reported that rinsing with boiling water after silane application, followed by drying at 50°C, resulted in tensile bond strength values comparable to those obtained using the HF application, followed by silane without heat treatment. However, in the present work, the use of HF (HFS group) gave rise to the highest mean bond strength.
On the other hand, silane application suggested to be effective when compared to no treatment at all, as shown by the fact that specimens in NT failed on cutting. As previously reported,  the effect of silane was strongly dependent on the drying procedure; the groups rinsed with boiling water followed by silane drying (SBRT and SBH) showed the highest mean values of bond strength among silane-treated samples, suggesting that the selective removal of the silane upper layer improved chemical adhesion. Only rinsing with running water, with no heat treatment (SRT), seemed not to effectively improve bond strength. Moreover, the behavior of SHBRT specimens suggested that silane heat-drying immediately after its application decreased the final bond strength, most likely because it favoured impurity deposition on the ceramic surface.
Some components of lithium disilicate ceramics can react chemically with silane coupling agents that link to the composite's organic phase as well as to the ceramic's inorganic phase. ,,, Better bond strength to the composite was observed after silane treatment, regardless of the ceramic surface etching treatment. But, when both procedures were combined, they promoted the best results, ,, as observed in the present study.
Comparison of the images shown in [Figure 2]A (no silane treatment) with 2 B-E suggested that silane modified the ceramic surface topography, creating a smooth layer. When silane was dried before washing [Figure 2]E (SHBRT specimen), the surface showed more relief, suggesting excessive removal of silane or its overadsorption on the ceramic surface. 
A previous study evaluated the bond strength between a resin cement block built on a ceramic block and suggested that the use of a resin cement film between the two substrates would be preferable for this evaluation, reflecting closely the clinical practice.  Considering that the adhesion between the resin cement and composite resin blocks, which are chemically compatible, would be higher than between ceramic blocks and resin cement, this latter design was chosen in the present study to induce the occurrence of failures preferably between ceramic and resin cement. In addition, finite element analysis of microtensile tests suggested that the specimens should be attached by the extremities and loaded along this long axis.  A specially designed device to achieve uniaxial alignment under tensile stress was thus developed.
Correct interpretation of failure modes avoids wrong conclusions about mechanical tests and adhesion zone phenomena. ,,,,, Groups presenting predominantly adhesive failures (SRT and SHBRT) showed lower bond strength mean values. Conversely, groups HFS, SBRT and SBH showed predominantly cohesive failures and higher bond strength average values, demonstrating the correlation between failure patterns and bond strengths. The observed failure patterns suggested that the union between resin cement and the substrates was stronger than the cement cohesive resistance.
In summary, silane evaporation patterns had a positive influence on bond strength between IPS Empress 2 ceramic and C and B resin cement. Different silane treatments lead to statistically different bond strength values, which were lower for groups that did not undergo boiling water treatment, or which were heat dried before rinsing, and higher for groups receiving only silane dried at room temperature before rinsing with boiling water. Bond strength values for specimens treated with HF associated with silane applications were statistically higher than those of all other groups evaluated. Higher bond strength average values were associated with predominantly cohesive failure patterns within the adhesive zone. A limitation of the present study was that the influence of silane evaporation patterns on ceramic surfaces previously treated with HF was not evaluated. This resulted from a previous assumption that silane-treated surfaces could be a substitute for ceramic surface conditioning with HF, as far as bond strength is concerned.
This work was partially supported by the Coordenaηγo de Aperfeiηoamento de Pessoal de Nνvel Superior - CAPES, Brasνlia, DF, Brazil. The Physical Tests Division from the Technological Centre Foundation of Minas Gerais - CETEC, Belo Horizonte, MG, Brazil, is acknowledged for support in the microtensile tests.
|1||Blatz MB, Sadan A, Kern M. Resin-ceramic bonding: A review of the literature. J Prosthet Dent 2003;89:268-74. |
|2||Braga RR, Ballester RY, Carrilho MR. Pilot study on the early shear strength of porcelain-dentin using dual-cure cements. J Prosthet Dent 1999;81:285-9.|
|3||Nakabayashi N, Pashley DH. Hibridization of dental hard tissues. Sγo Paulo: Quintessence; 2000. p. 127.|
|4||Sano H, Shono T, Sonoda H, Takatsu T, Ciucchi B, Carvalho R, et al. Relationship between surface area for adhesion and tensile bond strength - evaluation of a micro-tensile bond test. Dent Mater 1994;10:236-40. |
|5||Tao L, Pashley DH. The relationship between dentin bond strength and dentin permeability. Dent Mater 1989;5:133-9.|
|6||Della Bona A, Anusavice KJ, Hood JA. Effect of ceramic surface treatment on tensile bond strength to a resin cement. Int J Prosthodont 2002;15:248-53.|
|7||Della Bona A, Anusavice KJ, Shen C. Microtensile strength of composite bonded to hot-pressed ceramics. J Adhes Dent 2000;2:305-13. |
|8||Jardel V, Degrange M, Picard B, Derrien G. Correlation of topography to bond strength of etched ceramic. Int J Prosthodont 1999;12:59-64. |
|9||Della Bona A, Anusavice KJ, Mecholsky JJ Jr. Failure analysis of resin composite bonded to ceramic. Dent Mater 2003;19:693-9. |
|10||al Edris A, al Jabr A, Cooley RL, Barghi N. SEM evaluation of etch patterns by three etchants on three porcelains. J Prosthet Dent 1990;64:734-9. |
|11||Della Bona A, van Noort R. Ceramic surface preparation for resin bonding. Am J Dent 1998;11:276-80.|
|12||Hooshmand T, van Noort R, Keshvad A. Bond durability of the resin-bonded and silane treated ceramic surface. Dent Mater 2002;18:179-88.|
|13||Filho AM, Vieira LC, Araϊjo E, Monteiro Jϊnior S. Effect of different ceramics surface treatment on resin microtensile bond strength. J Prosthodont 2004;13:28-35. |
|14||Matsumura H, Kato H, Atsuta M. Shear bond strength to feldspathic porcelain of two cements in combination with three surface treatment. J Prosthet Dent 1997;78:511-7.|
|15||Ozden AN, Akaltan F, Can G. Effect of surface treatments of porcelain on the shear bond strength of applied dual-cured cement. J Prosthet Dent 1994;72:85-8.|
|16||Roulet JF, Sφderholm KJ, Longmate J. Effects of treatment and storage conditions on ceramic/composite bond strength. J Dent Res 1995;74:381-7.|
|17||Chen JH, Matsumura H, Atsuta M. Effect of etchant, etching period, and silane priming on bond strength to porcelain of composite resin. Oper Dent 1998;23:250-7.|
|18||Phrukkanon S, Burrow MF, Tyas MJ. Effect of cross-sectional area on bond strengths between resin and dentin. Dent Mater 1998;14:120-8.|
|19||Spohr AM, Sobrinho LC, Consani S, Sinhoreti MA, Knowles JC. Influence of surface conditions of silane agent on the bond of resin to IPS-Empress 2 ceramic. Int J Prosthodont 2003;16:277-82. |
|20||Stewart GP, Jain P, Hodges J. Shear bond strength of resin to both ceramic and dentin. J Prosthet Dent 2002;88:277-84. |
|21||Della Bona A, van Noort R. Shear vs. tensile bond strength of resin composite bonded to ceramic. J Dent Res 1995;74:1591-6.|
|22||Van Noort R, Noroozi S, Howard IC, Cardew G. A critique of bond strength measurements. J Dent 1989;17:61-7.|
|23||Versluis A, Tantbirojn D, Douglas WH. Why do shear bond tests pull out dentin? J Dent Res 1997;76:1298-307.|
|24||Cardoso PE, Braga RR, Carrilho MR. Evaluation of micro-tensile, shear and tensile tests determining the bond strength of three adhesive systems. Dent Mater 1998;14:394-8.|
|25||Pashley DH, Carvalho RM, Sano H, Nakajima M, Yoshiyama M, Shono Y, et al. The microtensile bond test: a review. J Adhes Dent 1999;1:299-309.|
|26||El Zohairy AA, de Gee AJ, de Jager N, van Ruijven LJ, Feilzer AJ. The influence of specimen attachment and dimension on microtensile strength. J Dent Res 2004;83:420-4. |
|27||Foxton RM, Pereira PN, Masatoshi N, Tagami J, Miura H. Long-term durability of the dual-cure resin cement/silicon oxide ceramic bond. J Adhes Dent 2002;4:125-35. |
|28||El Zohairy AA, De Gee AJ, Mohsen MM, Feilzer AJ. Microtensile bond strength testing of luting cements to prefabricated CAD/CAM ceramic and composite blocks. Dent Mater 2003;19:575-83.|