SciELO - Scientific Electronic Library Online

 
vol.11 issue1 author indexsubject indexarticles search
Home Pagealphabetic serial listing  

RSBO (Online)

On-line version ISSN 1984-5685

RSBO (Online) vol.11 n.1 Joinville Jan./Mar. 2014

 

ORIGINAL RESEARCH ARTICLE

 

Repair on silorane-based composite

 

 

Dilcele Silva Moreira DziedzicI; Shiffa al SaydI; Leonardo Fernandes da CunhaII; Lino Oliveira Carvalho de SantanaI; Carla Castiglia GonzagaI; Adilson Yoshio FuruseI

I Department of Dentistry, Positivo University – Curitiba – PR – Brazil
II Private practice – Brasília – DF – Brazil

Corresponding author

 

 


ABSTRACT

Introduction: Silorane-based composites have low polymerization shrinkage and good color stability. However, the effectiveness and the best surface treatment to carry out repairs to this type of restoration is unclear. Objective: To evaluate the effect of different types of repair made on a silorane-based composite. Material and methods: 80 disks of silorane-based composite were prepared (Filtek P90, 3M ESPE) and divided into eight groups (n = 10), according to the surface treatment being carried out before repairs of either the same silorane composite or a dimethacrylate material (Filtek Z350, 3M ESPE) were conducted. In two groups the immediate adhesion without repair (positive control) was evaluated. In other two groups repairs without any surface treatment (negative control) were evaluated. Surface treatments before the repair of the four remaining groups included the application of adhesive systems specific to silorane (Silorane System Adhesive, 3M ESPE) or to dimethacrylate (Adper Single Bond 2, 3M ESPE) and roughening followed by application of adhesive system. All groups were stored into distilled water at 37°C for 1 week prior to the microshear bond strength evaluation. Results: The group immediate adhesion silorane-dimethacrylate and group repair silorane-dimethacrylate without surface treatment showed lower microshear bond strength values and were statistically different from groups with surface treatment and immediate adhesion silorane-silorane (p < 0.05). Conclusion: Surface treatments with application of adhesive systems compatible with the repair material or roughening prior to the application of these adhesive systems are suitable for repairing silorane-based composites.

Keywords: silorane resins; composite resins; shear strength.


 

 

Introduction

Both the resin composites and the adhesive systems are very versatile and their use have favored the greatest advancements in aesthetic Dentistry leading to the preservation of tooth tissues and obtaining nearly invisible restorations by little wearing of the sound tooth structure. Thus, Dentistry has been currently experiencing the perspectives predicted for over one decade 19, by emphasizing restorative direct techniques and conservative preparations. However, the polymerization shrinkage of dimethacrylate-based composites has been considered as their major shortcoming resulting in marginal failures and leakage. The current development of composites whose polymerization occurs by the opening of the rings rather than by free radical polymerization and approximation of dimethacrylate monomers has evidenced a reduction in polymerization shrinkage. Silorane-based resin composites have their organic matrix formed by siloxane and oxirane with cationic polymerization and opening of the rings during polymerization reaction 14,24. This has resulted in low polymerization shrinkage, insolubility to simulated biological fluids, and good color stability when compared with dimethacrylatebased composites s 5,7,10,24. Despite these advantages, further studies are necessary to evaluate the behavior of silorane-based resin composites in cases requiring repair.

During the clinical life of a restorat ion, failures can occur, which leads to the indication of repair instead of its total replacement. Clinical researches on repairing, reshaping and sealing of direct restorations have demonstrated that these minimal intervention procedures are conservative alternatives indicated in cases of failure in marginal adaptation and staining 13,21. Therefore, when properly indicated, the repair procedure has been considered as an alternative to total replacement of a restoration 6 decreasing the weariness of the sound tooth structure and the time amount required to remove the restorative material completely 16.

Notwithstanding, the repairing requires that the restoration surface is adequately treated 1,9. Among these treatments, silanization has shown controversial results, with either effectiveness in 22 or unable of increasing the bond strength 3. On the other hand, the surface roughness has exhibited good results 9, probably because of promoting a micromechanical linking between the old resin composite and the new restorative system.

The superficial treatments for repairing most taught in dental schools have been the roughening of the exposed surface, etching with phosphoric acid, cleaning with pumice and abrading with aluminum oxide 1. The materials most used in repairing have been the adhesive agents, resin composite, silane agent, and flowable resin 1. However, most of the studies were conducted with resins containing organic matrixes with similar chemical characteristics 9,11.

The concern with the compatibility between resins with different organic matrix, such as silorane-based and conventional resins, is clinically relevant for eventual repairs because not even the dentist knows the composite type employed firstly 4. The surface weariness followed by siloranebased bonding agent has been recommended to repair silorane-based resins with similar resins while the application of the primer agent has been contraindicated 17. On the other hand, when a dimethacrylate-based resin is used in the repair, an application of an intermediary layer of siloranebased bonding agent has been advised 12,23.

Dimethacrylate-based material bond strength to silorane-base materials has been little studied probably because the latter is recently on the market. Consequently, both the repairing effectiveness and which would be the best surface treatment has not been clarified yet. Moreover, the behavior of the interaction between the different layers should be evaluated at long-term, which can be simulated by laboratorial studies.

The aim of this study was to evaluate the microshear bond strength of the repair interface between a silorane-/silorane-based resin as well as a silorane-/dimethacrylate-based resin.

 

Material and methods

Eighty matrixes made from acrylic resin (Clássico, São Paulo, SP, Brazil) within PVC tubes (3/4" in diameter, 1 cm in height), with a center cylindrical orifice with 5 mm in diameter and 3 mm in mean depth. The restorative materials and the adhesive agents employed are described in table I.

 

 

 

The silorane-based resin composite (Filtek P90, 3M ESPE, St. Paul, USA) was inserted within the orifice of acrylic resin matrix with the aid of a spatula, at two increments, in order to obtain a base disc as substrate for the silorane-based resin composite. Each increment (1.5 mm in thickness) was individually light-cured for 40 s with the aid of a light-curing unit (Coltolux LED, Coltène/Whaledent, Altstätte, Switzerland), at intensity of 1,000 mW/cm2. After the insertion of the last increment of resin composite P90, a polyester strip (TDV Dental Ltda., Pomerode, SC, Brazil) was placed onto the surface of the resin not polymerized and pushed with the aid of a glass lamina with 1 mm in thickness to achieve a flat surface prior to photoactivation, which was carried out through the polyester strip. To obtain the aging of the resin composite specimens prior to the repairing procedures, the discs were stored into distilled water at 37°C for one week. This was executed to mimic the condition of a restoration exposed to the humidity within oral cavity.

The discs were divided into six groups (G1 to G6). The specimens from G1, G3 and G5 were repaired with a silorane-based material (Filtek P90), while those from G2, G4 and G6 were repaired with a dimethacrylate-based material (Filtek Z350 XT, 3M ESPE, St. Paul, USA). The repairs were executed after the washing of the discs with air jet for 15 s and drying with air jet for 20 s at 10 cm of distance. G5 and G6 specimens were roughened with the aid of 600-grit sandpaper, at a single direction with water lubrication (Ecomet 250, Lake Buff, IL, USA), prior to the treatment with the adhesive systems and repairing procedures.

The specimens of G4 and G6 underwent 37% phosphoric acid etching (Dentak Villevie, Joinville, SC, Brazil) for 30 s. G6 specimens received silane application (ProSil, FGM, Joinville, SC, Brazil), while the adhesive system Single Bond 2 (3M ESPE, St. Paul, USA) was applied onto the specimens of G4 and G6 prior to the repairing procedure with dimethacrylate-based resin (Z350 XT). The adhesive system Single Bond 2 application was performed with the aid of a microbrush, twice, followed by gentle air drying for 5 s and light-curing for 10 s.

The specimens of G3 and G5 were washed and dried before the treatment with the adhesive system P90 (3M ESPE, St. Paul, USA) and the repairing procedure was executed with silorane-based material (P90). The application of the two-flask adhesive system P90 (Self-Etch Primer and Bond agent) was executed according to the manufacturer's recommendation. The self-etch primer agent was applied with the aid of a microbrush for 15 s, followed by gentle air drying and light-curing for 10 s. Table II exhibited the description of the experimental groups.

 

 

 

Cylindrical silicone tubes (Perfitécnica, Salto, SP, Brazil) with 0.95 mm in internal diameter and 1.5 mm in height were used as matrixes for either the immediate adhesion or repairing procedure after the surface treatment of each silorane disc, according to the group assigned (n = 10). One portion of resin composite was inserted into the cylindrical silicone tube with the aid of a spatula. After the cleaning of the tube extremities with the same spatula, the set was put in contact with the center of the silorane disc with the aid of dental tweezers. The photoactivation of the resin within the cylindrical tube in contact with the disc enabled their adhesion therefore simulating the execution of a repairing procedure, but with standardized characteristics. Elapsing 10 minutes, the silicone tube was cut with the aid of a size 15 blade to expose the resin cylinder and the repairing interface. Following, the specimens were stored into distilled water at 37°C.

Cyl inders of si lorane- (Fi ltek P90) and dimethacrylate-based (Z350 XT) materials were constructed directly onto the discs of G7 and G8, respectively, without previous aging, to analyze the immediate adhesion between the materials.

Thus, 80 specimens were submitted to micro shear bond strength test through a universal testing machine (EMIC, model DL3000, São José dos Pinhais, PR, Brazil) and observed regarding to failure types. The acrylic resin matrixes were mounted into a round device and fixed to the testing machine with load applied with the aid of a steel wire (0.2 mm in diameter) and crosshead speed of 0.5 mm/min until rupture.

The bonding strength was calculated with the aid of software linked to the testing machine by dividing the maximum force recorded (in Newton) by the bonding area (in mm2), and expressed in MPa. After the shear bond strength test, the specimens were examined with the aid of stereoscopic magnifying glass at x30 magnification (SZX9, Olympus, Tokyo, Japan), to determine the failure mode, which were classified as follows: adhesive (at the bonding interface), cohesive (at the base resin or cylinder resin) and mixed. The data was submitted to statistical analysis through Student's t test with level of confidence of 95%.

 

Results

Micro shear bond strength values indicated an increasing in the bonding strength of the repairing procedures with roughening and application of the adhesive system onto the base disc (P90). Moreover, the results showed in table III and figure 1 demonstrated that the differences among G1, G3, G4, G5, G6 and G7 were not statistically significant (p < 0.05). The greatest micro shear bond strength mean values were observed in the specimens of G7 with immediate adhesion between silorane-/siloranebased resins without previous aging.

 

 

 

 

 

The smallest micro shear bond strength mean values were observed in the specimens of G8 and G2, that is, in the repairing procedure between silorane-/dimethacrylate-based material without surface treatment and in the immediate silorane- /dimethacrylate-based material respect ively. Significantly highest micro shear bond strength values were observed in groups in which the surfaces had been treated with adhesive systems (G5 and G6), both for repairing procedures with silorane (G3 and G5) and dimethacrylate (G4 and G6), but without statistically significant differences when compared with G7 (immediate adhesion between silorane-/silorane-based materials). The decreasing of the adhesivity after the aging period of the material surface was observed by comparing G7 with G1, without statistically significant differences.

Figures 2 and 3 exempli f ied the fai lure types seen with the aid of the stereoscopic magnifying glass at x30 magnification. Cohesive failures were observed when part of the material within the cylinder was retained onto the base resin (figure 3B). The highest micro shear bond strength mean values (table III), exhibited by the immediate adhesion between silorane-/siloranebased materials (G7), and corresponded to cohesive failures. All failures of the immediate adhesion between silorane-/dimethacrylate-based materials (G8) and of the repairing procedure between silorane-/dimethacrylate-based materials without surface material (G2) were adhesive type (figure 2). In the groups submitted to the surface treatment with adhesive system and roughening, both for silorane-/silorane-based materials and silorane-/dimethacrylate-based materials, showing bond strength mean values significantly higher than those of G2 and G8, exhibited mixed and cohesive failures.

In mixed failures, fragments of the cylinder resin were retained into the base resin (figure 3C). All failures within G2 and G8 were adhesive failures (figure 2), with the smallest micro shear bond strength mean values (figure 1). Adhesive failures where the base resin (substrate of resin composite P90) were clean and smooth, without resin remnants of the cylinder resin (figure 3D).

 

 

 

 

 

Discussion

By consider ing the different chemical characteristics between the dimethacrylate- and silorane-based resin composite, the aim of this study was to evaluate the bond strength between them. In the dimethacrylate-based composites, the oxygen-inhibited layer formed onto the surface after the polymerization of the material increments in contact with the environmental air enables a better adhesion between the layers of these materials 8. On the other hand, the cationic polymerization of silorane-based materials do not lead to the formation of oxygen-inhibited layer and the decreasing of adhesion among successive increments of silorane over time 23 would cause the decreasing of micro shear bond strength. For this reason, in this present study, the preparation of each specimen of G7 (control group – immediate adhesion between silorane/silorane) was executed with less than 5 min, to assure the greatest reactivity among successive increments, as suggested by Tezvergil-Mutluay et al. 23, who observed the greastet immediate adhesion values of silorane increments when those were inserted and light-cured in few seconds 23. The greatest micro shear bond strength values were observed in the specimens of G7, as cylinders of silorane-based composites were made immediately onto discs of the same resin, therefore enabling cohesive failures within all specimens.

As discussed above, the chemical reactivity of the components of silorane-based composites accounting for the adhesion of successive increments decreases over time and could affect the adhesion of repairing procedures 23. Notwithstanding, in this present study, the reduction of the adhesivity after the aging of the material surface was not stat ist ically significant when the specimens submitted to immediate adhesion between silorane- /silorane-based material (G7) were compared with those underwent repairing without surface treatment (G1). These results demonstrated that despite of the aging period and conditions, the material still has enough reactivity to provide adhesion with chemically-compatible repairing material.

The smallest micro shear bond strength mean values were seen in G8 specimens submitted to immediate adhesion between si lorane-/ dimethacrylate-based materials. Other authors still verified a smaller immediate bond strength between silorane-/dimethacrylate-based materials, without either aging period or surface treatment 23. The result of the lack of adhesion between the dimethacrylate-based and freshly-light-cured silorane-based material when this exhibits the greatest chemical reactivity confirms the lack of chemical affinity between the materials.

This present study used a one-week period into distilled water at 37°C as aging method. Different authors studying repairing procedures on siloranebased resins have employed different techniques to mimic the conditions to which the restoration are submitted within oral cavity: 72 hours into saline solution at 37°C 12, 24 hours into water at 100ºC 15, one month into water at 60°C 18, and 24 hours into water at 37°C 20. These methods have been used to promote the water sorption and leaching of components not participating in the polymerization reaction, prior to the repairing procedure.

Micro shear bond strength testing was chosen in this study because it does not require additional cuts after the bonding of the segments during the preparation of the specimens, taking into consideration the low bond strength observed by other authors in both the immediate adhesion and the repairing between silorane- and dimethacrylatebased resins 4,12,23. The evaluation method of micro shear bond strength through orthodontic wire has been suggested as an alternative to microtensile bond strength because of its easier execution and good distribution of stresses in the adhesive interfaces 2.

According to Tezvergil-Mutluay et al. 23, the interposition of silorane-based adhesive system as intermediary layer would provide a better immediate adhesion between silorane-/dimethacrylate-based materials than that provided by dimethacrylatebased adhesive systems. The initial adhesion between silorane-/dimethacrylate-based materials thorugh silorane adhesive system, composed by dimethacrylate with carboxylic and phosphoric acid groups, enables the reaction of the phosphate group with oxirane and that of acrylate with dimethacrylate promoting chemical adhesion 12,23. The effect of the lack of chemical affinity between silorane and dimethacrylate impairing the initial adhesion (G8) was not decreased by the surface aging of G2, but it occurred with the application of dimethacrylate-based adhesive system (G4). In the treatment with the exclusive application of the dimethacrylate-based adhesive system (G4) prior to repairing procedure, the micro shear bond strength values were not statistically different from those of the initial silorane-silorane adhesion (G7). The effect of dimethacrylate-based adhesive system application was more substantial than the decreasing of silorane chemical reactivity during the aging period, with statistically significant difference between G3 and G8.

In G5 and G6, where the repaired surfaces were treated with roughening prior to the application of the adhesive systems, bond strength values were not statistically different from those of the immediate silorane/silorane adhesion (G7), both repaired with silorane- (G5) and dimethacrylate-based resins (G6). The roughening of material surface to be repaired promoted the weariness and development of micro rugosities. The intermediary interfaces created by roughening and the filling with low viscosity material provide micro retentions and allow a better adaptation with the repairing material of high viscosity. The roughening obtained with the aid of 600-grit sandpaper, employed in this present study, was also used by other authors 12. Other roughening methods have been used in silorane repairing: 80-grit sandpaper 18, 320-grit sandpaper 15, abrasion with diamond drill and aluminum oxide blasting 25.

The surface treatment for the repairing between silorane-/dimethacrylate-based materials with roughening but without silane application prior to the application of the dimethacrylate adhesive system was not analyzed by this present study. The silane application executed in the repairing procedure of G6 could have contributed to increase the micro shear bond strength values as observed by other authors who used silane-based adhesive system 18 and silane prior to the adhesive system 25, which suggested that the silane promoted a greater superficial leakage.

The greatest micro shear bond strength mean values observed in G7 (table III) corresponded to cohesive failures (figure 2). In mixed failures, fragments of the cylinder resin were retained into the base (figure 3C). The failures in G2 and G8 were of adhesive type (figure 2), with the smallest micro shear bond strength mean values (table III). In adhesive failures, the silorane discs were clean and smooth, without fragments of the cylinder resin (figure 3D). These results suggested that there would be little or none adhesion between the two resins.

In this present study, adhesive systems indicated for either P90 and dimethacrylate, considering the two possible clinical situations: the composition of the original resin to be repaired is either known or unknown. Although this present study did not verify significant differences between the roughening treatment followed by the adhesive system and the single application of the adhesive system, roughening seems to be a more reliable surface treatment for repairing procedures because it increases the adhesion area.

 

Conclusion

Surface treatments with the application of either adhesive systems or roughening enabled the repairing procedures in silorane-based resin composites when an adhesive system compatible with the repairing material was used. These results suggested that repairing procedures onto silorane-based resin composites can be executed successfully, regardless of the surface roughening and the composition of the repairing material.

 

Acknowledgments

This study was carried out during the Undergraduate Research Program of Positivo University, Curitiba, Paraná, Brazil (2012/2013). The restorative materials employed were kindly supplied by 3M ESPE.

 

References

1. Blum IR, Lynch CD, Wilson NH. Teaching of direct composite restoration repair in undergraduate dental schools in the United Kingdom and Ireland. Eur J Dent Educ. 2012 Feb;16(1):e53-8.         [ Links ]

2. Braga RR, Meira JB, Boaro LC, Xavier TA. Adhesion to tooth structure: a critical review of "macro" test methods. Dent Mater. 2010 Feb;26(2): e38-49.

3. Brosh T, Pilo R, Bichacho N, Blutstein R. Effect of combinations of surface treatments and bonding agents on the bond strength of repaired composites. J Prosth Dent. 1997 Feb;77(2):122-6.

4. Cunha LF, Dziedzic DSM, Nascimento BM, Baratto SSP, Gonzaga CC, Furuse AY et al. Influence of different surface treatments on the shear bond strength of a methacrilate composite repaired with silorane. RSBO. 2013. In press.

5. Cunha LF, Santana LOC, Baratto SSP, Mondelli J, Haragushiku GA, Gonzaga CC et al. Staining susceptibility of methacrylate and silorane-based materials: influence of resin type and storage time. RSBO. 2013;10(2):161-6.

6. Demarco FF, Correa MB, Cenci MS, Moraes RR, Opdam NJ. Longevity of posterior composite restorations: not only a matter of materials. Dent Mater. 2012 Jan;28(1):87-101.

7. Eick JD, Smith RE, Pinzino CS, Kostoryz EL. Stability of silorane dental monomers in aqueous systems. J Dent. 2006 Jul;34(6):405-10.

8. El-Askary FS, Fawzy AS, Abd Elmohsen HM. Tensile bond strength of immediately repaired anterior microfine hybrid restorative composite using nontrimmed hourglass specimens. J Adhes Dent. 2009 Feb;11(1):41-7.

9. Furuse AY, Cunha LF, Benetti AR, Mondelli J. Bond strength of resin-resin interfaces contaminated with saliva and submitted to different surface treatments. J Appl Oral Sci. 2007 Dec;15(6):501-5.

10. Furuse AY, Gordon K, Rodrigues FP, Silikas N, Watts DC. Colour-stability and gloss-retention of silorane and dimethacrylate composites with accelerated aging. J Dent. 2008 Nov;36(11):945-52.

11. Furuse AY, Pirolo R, Rodrigues LK, Pizzatto E, Losso EM, Mondelli J. The efficacy of acid etching for removing contamination in layered dental restorations. Gen Dent. 2012 Sep-Oct;60(5): e312-4.

12. Giachetti L, Scaminaci Russo D, Baldini M, Goracci C, Ferrari M. Reparability of aged silorane with methacrylate-based resin composite: micro shear bond strength and scanning electron microscopy evaluation. Oper Dent. 2012 Jan- Feb;37(1):28-36.

13. Gordan VV. Clinical evaluation of replacement of class V resin based composite restorations. J Dent. 2001 Sep;29(7):485-8.

14. Guggenberger R, Weinmann W. Exploring beyond methacrylates. Am J Dent . 2000 Nov;13(Spec No):82D-4D.

15. Hamano N, Chiang YC, Nyamaa I, Yamaguchi H, Ino S, Hickel R et al. Effect of different surface treatments on the repair strength of a nanofilled resin-based composite. Dent Mater. J 2011;30(4):537-45.

16. Krejci I, Lieber CM, Lutz F. Time required to remove totally bonded tooth-colored posterior restorations and related tooth substance loss. Dent Mater. 1995 Jan;11(1):34-40.

17. Luhrs AK, Gormann B, Jacker-Guhr S, Geurtsen W. Repairability of dental siloranes in vitro. Dent Mater. 2011 Feb;27(2):144-9.

18. Maneenut C, Sakoolnamarka R, Tyas MJ. The repair potential of resin composite materials. Dent Mater. 2011 Feb;27(2):e20-7.

19. Manhart J, Garcia-Godoy F, Hickel R. Direct posterior restorations: clinical results and new developments. Dent Clin North Am. 2002 Apr;46(2):303-39.

20. Mobarak EH. Effect of surface roughness and adhesive system on repair potential of silorane-based resin composite. J Advance Res. 2012;3:279-86.

21. Moncada G, Martin J, Fernandez E, Hempel MC, Mjor IA, Gordan VV. Sealing, refurbishment and repair of Class I and Class II defective restorations: a three-year clinical trial. J Am Dent Assoc. 2009 Apr;140(4):425-32.

22. Soderholm KJ. Flexure strength of repaired dental composites. Scand J Dent Res. 1986 Aug;94(4):364-9.

23. Tezvergil-Mutluay A, Lassila LV, Vallittu PK. Incremental layers bonding of silorane composite: the initial bonding properties. J Dent. 2008 Jul;36(7):560-3.

24. Weinmann W, Thalacker C, Guggenberger R. Siloranes in dental composites. Dent Mater. 2005 Jan;21(1):68-74.

25. Wiegand A, Stawarczyk B, Buchalla W, Taubock TT, Ozcan M, Attin T. Repair of silorane composite – using the same substrate or a methacrylate-based composite? Dent Mater. 2012 Mar;28(3):e19-25.

 

 

Corresponding author:
Dilcele Silva Moreira Dziedzic
Universidade Positivo – Graduação em Odontologia
Rua Professor Pedro Viriato Parigot de Souza, n. 5.300 – Campo Comprido
CEP 81280-330 – Curitiba – PR – Brasill
E-mail: dilcele@up.edu.br

Received for publication: March 18, 2013
Accepted for publication: July 20, 2013