Repair of silorane-based dental composites: Influence of surface treatments
Introduction
Over the years, polymerization shrinkage remains as one of the major drawbacks of composite materials and leads to microleakage which is among the major factors for composite material failures in the oral environment. Silorane-based dental composite materials (Filtek Silorane, 3M ESPE, Seefeld, Germany) are designed to minimize shrinkage and polymerization stress [1]. Silorane derives from siloxanes and oxiranes, which provide the hydrophobic and low-shrinking silorane base of Filtek Silorane. However, despite the continuing development of composite resins with improved properties, several factors, including fracture and discoloration, may still present concerns. As a result, dentists must decide whether to replace or simply repair these restorations. Complete removal of defective composite restorations is not always necessary or desirable [2]. Repairs of composite restorations are frequently accomplished by the addition of new composite to the existing aged composite. Because aged conventional methacrylate-based composite restorations do not retain an unpolymerized surface layer (oxygen inhibition layer) [3], several techniques are suggested to maximize the composite repair strength. The most common suggestions include increased surface roughness [4], [5], silane treatment [6], [7] and the application of a low viscosity bonding agent [7], [8]. Silorane-based composites polymerize by a cationic ring-opening process and are nearly insensitive to oxygen. If the cations are permanently present in the silorane and can be used for repair (in a process called “living polymerization”), this might offer an advantage for silorane repairs over other methacrylate-based composite repairs.
When composite materials with small average filler sizes are ground, only a small area of pure glass surfaces is evident when examined under a scanning electron microscope (SEM). This raises the question of whether the silane treatment could be omitted.
Another aspect to consider is the use of the solvent of the bonding agent such as acetone or ethanol. Solvents enhance resin surface wetting capabilities, quickly vaporize and remove water molecules from the surface [9]. As the hydrophobicity of sirolane-based composites or bonding agents impedes penetration into the smallest crack and gaps of the water-saturated surface on the aged composite, these functions of solvents may play an important role in the repair process. Acetone also might solubilize and soften the surface [10]. The most important function of a repair liquid is considered to be that it solubilizes the base material, penetrates it, and finally leads to chemical bonding with the repair material [5], reported as “liquid etching” [11]. Therefore the application of acetone as a pretreatment may possibly increase the bonding strength. However, the softened layer may also result in reduced bond strength of the dental composite. In addition, solvents such as acetone or ethanol could act as an inhibitor of polymerization for bonding agents or composites [12].
The purpose of our study was to evaluate how to optimize bond strength for the repair of silorane composite materials, which are a new class of compounds for dental use.
Section snippets
Materials and methods
The materials used in this study are shown in Table 1. The experimental design is outlined in Fig. 1.
Results
The results of the microtensile bond strength tests are summarized in Table 2. The tensile strength of unrepaired silorane (positive control group) was 54.7 ± 6.5 MPa. In general, before thermo-cycling and mechanical loading, all repaired groups had only 30–75% microtensile bond strength when compared to the unrepaired control group. All differences between the repaired groups and the unrepaired group were significant (p < 0.05, one-way ANOVA, Scheffé).
Before fatigue simulation, Group 1 (no
Discussion
Several testing methodologies, namely shear [18], [19], [20], tensile [19], and microtensile tests [21], have been suggested for evaluating the bond strength of dental materials. For the test to measure the bond strength values accurately, it is crucial that the bonding interface should be the most stressed region [18], [19]. However, shear tests have been criticized for the development of non-homogeneous stress distributions in the bonding interface, inducing either a misinterpretation or an
Acknowledgment
The authors would like to express their appreciation to 3M ESPE Corporation for providing Filtek Silorane and two kinds of blind pretreatment agents.
References (29)
- et al.
Siloranes in dental composites
Dental Materials
(2005) Clinical evaluation of replacement of class V resin based composite restorations
Journal of Dentistry
(2001)- et al.
Bond strength of repaired anterior composite resins: an in vitro study
Journal of Dentistry
(1998) - et al.
Effect of surface treatments on the tensile bond strength of repaired water-aged anterior restorative micro-fine hybrid resin composite
Journal of Dentistry
(2008) - et al.
Bonding of composite to water aged composite with surface treatments
Dental Materials
(2007) - et al.
Bonding to resurfaced posterior composites
Dental Materials
(1989) - et al.
Composite–composite repair bond strength: effect of different adhesion primers
Journal of Dentistry
(2003) - et al.
Threedimensional finite element analysis of the shear bond test
Dental Materials
(1995) - et al.
Evaluation of new methods for composite repair
Dental Materials
(1992) - et al.
Effect of solvent type and content on monomer conversion of a model resin system as a thin film
Dental Materials
(2007)
Effects of surface properties on bond strength between layers of newly cured dental composites
Journal of Oral Rehabilitation
Shear bond strength of self-etching bonding systems in combination with various composites used for repairing aged composites
Journal of Adhesive Dentistry
A study on repair restoration of high-filler-content prosthetic composite resins – effect of surface treatment conditions on bending bond strength
Journal of Japan. Prosthodontic Society
Laboratory evaluation of one-component enamel/dentin bonding agents
American Journal of Dentistry
Cited by (25)
A comprehensive review: Physical, mechanical, and tribological characterization of dental resin composite materials
2023, Tribology InternationalCitation Excerpt :γ-MPS is a common silane coupling agent. To connect the reinforcement to the resin matrix in the low-shrink silorane composite, an epoxy functionalized coupling agent, γ-MPS, is employed [66,67]. The methoxy groups hydrolyze to form hydroxyl groups through the reinforcement treatment practice, which is catalysed by an acid or base.
Vinyl sulfonamide based thermosetting composites via thiol-Michael polymerization
2020, Dental MaterialsCitation Excerpt :Many efforts have been undertaken to overcome the inherent disadvantages associated with methacrylates. For example, approaches have included soft-start polymerization with a step-wise modulation of light energy [23], alternate polymerization mechanisms [24], as well as monomer chemistry alterations [25]. Several alternate polymerization reactions have gained attention in the development of dental resins.
Repair bond strength of dental composites: systematic review and meta-analysis
2016, International Journal of Adhesion and AdhesivesRepair of restorations - Criteria for decision making and clinical recommendations
2013, Dental MaterialsCitation Excerpt :Similar to measurements in methacrylate-based materials [43], an improvement in bond-strength by using a low-viscosity experimental flowable silorane-based composite as intermediate agent was also attested for the silorane-based composite [45]. It was however also found that the repair method (no treatment, bonding agent, acetone, acetone + bonding agent, ethanol, ethanol + bonding agent, silane and silane + bonding agent on aged and with 320-grit SiC paper ground surfaces) had no influence on the repair strength after fatigue simulation [90]. In terms of compatibility of resin-based composites based on silorane and methacrylate matrices, increased bond strength was measured when a silane and a phosphate-dimethacrylate-based adhesive system were used for repair [45,56,66].
Biomaterials for dental composite applications: A comprehensive review of physical, chemical, mechanical, thermal, tribological, and biological properties
2022, Polymers for Advanced Technologies