Abstract
This study aimed to evaluate and compare the internal adaptation of bulk-fill resin-based composite restorative materials with flowable composites as lining materials using self-etch adhesive system. Class I cavities (2mmx4mm) were prepared on flattened occlusal surfaces of fifty extracted human premolars and randomly assigned into five groups (n=10) according to the materials used: Beautifil Bulk-fill Restorative (BR); Beautifil Bulk-fill Flowable (BF); Beautifil Flow Flowable F10 (BF10); and Self-etch adhesive (SEA). Group A: SEA+BR; Group B: SEA+BF10+BR; Group C: SEA+BF+BR; Group D: SEA+BF10+SEA+BR and Group E: SEA+BF+SEA+BR. The samples were thermocycled for 500 cycles, then sectioned mesiodistally, polished and pre-treated prior to scanning electron microscopy (SEM) evaluation. From SEM images, measurement of adhesive and cohesive adaptation failures was recorded at multiple sites of the pulpal floor and in between materials. Data were analysed using one-way ANOVA and post-hoc Tukey tests (p<0.05). Cohesive failure in SEA was observed at the pulpal floor with the lowest percentage in Group A (5.14%), and highest in Group C and E (>16%). However, there were no significant difference among all groups. Adhesive failure was seen at the pulpal floor between SEA+BF/BF10/BR and between SEA+dentine with the highest percentage of gaps formed in Group A between SEA+dentine (6.62%) and SEA+BR (5.30%). Nonetheless, no significant differences were observed among all groups with p=0.89 and p=0.70, respectively. With the use of BF/BF10 at the pulpal floor, adhesive failure was reduced but resulted in increased of cohesive failure. However, both adaptation failures were absent between materials (BF/BF10 and BR) regardless with or without application of SEA.
Highlights
Composite resins have been widely accepted in restorative dentistry since they were first developed due to their competency of replacing biological tissue functionally and aesthetically [1]
No significant differences were evident on the internal gaps formed in between Self-etch adhesive (SEA) and Bulk-fill Restorative (BR) (Group A) and between liner or flowable composites and SEA in Group B, C, D, and E, at the pulpal floor (p=0.89) (Table 3)
Oliveira et al [28] claimed that the use of flowable composite as an intermediate layer would further increase the polymerisation shrinkage stress at the adhesive dentine interphase leading to adhesive failure and gaps formation
Summary
Composite resins have been widely accepted in restorative dentistry since they were first developed due to their competency of replacing biological tissue functionally and aesthetically [1]. Obtaining good marginal seals in a restoration with composite materials determine long-term success of a restored tooth. This requirement of achieving good marginal seals becomes a major concern for every clinician. The contraction stress has the potential of generating gaps at the toothmaterial interface if the strength exceeds the dentine bond strength. Such gaps are considered deleterious because they allow transmission of fluid or bacteria between the dentine pulp complex and the oral environment, leading to post-operative sensitivity, marginal staining and secondary caries [3, 4, 5]
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