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Abstract
This research was designed to investigate the effect of fillers on bond strength of total-etch and self-etch bonding systems. A total of 92 intact, sound, and freshly extracted human molars were selected to conduct the study. Eighty molars were used for shear bond strength testing and 12 molars were used for scanning electron microscopic study. For shear bond strength testing, each tooth was horizontally embedded in a specially fabricated cuboidal shaped copper mould using self-curing acrylic resin and the buccal surfaces were ground to expose a flat superficial dentin surfaces. The prepared specimens were divided into two equal groups, 46 specimens each, according to the type of bonding systems (A) utilized. In the first group, (A1) self-etch bonding systems were used. While in the second group, (A2) total-etch bonding systems were used. Each group was further subdivided into two subgroups, 23 teeth each, according to the presence of filler in the bonding agent (B). In the first subgroup (B1), an unfilled bonding system (One-step) was used. In the second subgroup (B2), a filled bonding system (One-step Plus) was used. Resin composite (AELITE) build ups were constructed and light cured.
Specimens were then loaded to failure at the base of the resin composite using a specially constructed attachment fixed to a universal testing machine, at across head speed 0.5 mm/minute. The shear bond strength values were recorded, tabulated and statistically analyzed.
The remaining 12 samples were used to study resin-dentin interface. After various treatments 3 representive samples from each group, were examined using scanning electron microscope.
The results revealed that for both bonding techniques (total-etch and self-etch) the filled bonding systems (One-step Plus) showed statistically significantly higher mean shear bond strength values compared to their unfilled counter part. Meanwhile, self-etch bonding systems recorded statistically significantly higher mean shear bond strength values than total-etch bonding systems. Also, the unfilled total-etch bonding system showed the statistically significantly lowest mean shear bond strength. While, filled self-etch bonding system showed the statistically significantly highest mean shear bond strength. Meanwhile, there was no statistical significant differences between filled total-etch and unfilled self-etch bonding system. SEM examination of resin/dentin interface revealed differences in the interfacial micromorphology with different bonding systems.
Under the conditions of this research, the following conclusions were evident:
1. Addition of fillers may be considered beneficial for enhancement of bonding to dentin.
2. Self-etch bonding systems may constitute an effective promising modality for dentin surface treatment for prompt adhesion.
3. Self-etch adhesives combined with filler incorporation may constitute a promising dentin treatment modality.
4. No correlations existed between the resultant bond strength and the ultramorphology of the adhesive joint as assessed by SEM.