Influence of Water Aging on Microtensile Bond Strength of a Flowable and a Packable Bulk-fill Resin Composites to Dentin

Abstract

AIM: Investigation of the aging effect on the microtensile bond strength (μTBS) of bulk-fill resin composite (RC) versus a conventionally incrementally applied one.
 MATERIALS AND METHODS: A total number of 45 sound human impacted third molars extracted molars have been selected to prepare specimens for the μTBS test. Teeth were randomly divided into three groups (C) according to type of RC material which used for restoring the teeth. Where nanohybrid RC (Grandio®SO) was used as the control Group (C1), packable bulk-fill RC (X-tra fil®) was used for restoring teeth in C2 group and flowable bulk-fill RC (X-tra base®) was used for restoring teeth in C3 group. Each group was further subdivided into 3 subgroups (n = 5) according to the water storage time, where in subgroup 1; teeth were stored for 24 h, subgroup 2; teeth were stored for 3 months while for subgroup 3; and teeth were stored for 6 months. After water storage, teeth were sectioned for preparation of μTBS testing beams. Maximum tensile stresses were recorded in megapascal (MPa).
 RESULTS: After 24 h of water storage, the X-tra base® showed a higher statistically significant μTBS to dentin (33.82 ± 9.84 MPa) than did the other two types of RCs. After 3 months, the X-tra fil® showed the lowest mean value of μTBS (10.90 ± 5.66 MPa), meanwhile, after 6 months of water storage Grandio®SO showed the highest mean value of μTBS (15.85 ± 6.76 MPa). Regardless of the time the X-tra fil® showed the lowest mean of μTBS (15.07 ± 11.73 MPa), while there is no significant difference between the X-tra base® and Grandio®SO. Furthermore, the water aging adversely affects μTBS values which deceased gradually by time.
 CONCLUSION: The packable bulk-fill RC characterized by lower μTBS to dentin in comparison to the flowable bulk fill and the incrementally applied nanohybrid RCs. Furthermore, the μTBS of the three tested materials decreased gradually by aging.

Effect of Two Different Deproteinizing Agents on Microtensile Bond Strength between Resin Composite and Deep Dentin using Two Restorative Protocols. An In-Vitro Study

“…This is attributed to its composition which has stress reliever molecules and polymerization modulators. Bulk-fill resin composite is available either as a packable bulkfill resin composite designed to restore the entire of the prepared cavities or flowable bulk-fill resin composite designed to be applied as a base or lining material leading to decrease in polymerization contraction stresses (10) .…”

“…In addition, these materials are claimed to have less shrinkage stresses compared to conventional resin composite. This may be attributed to having stress reliever molecules and polymerization modulators (10,11) . Moreover, application of flowable resin composite liner is beneficial to minimize polymerization shrinkage stresses at the bonded interface and increase the adaptation of resin composite to cavity boundaries (12) .…”