Category: Laboratory Research
Do Physical Properties of Luting-Resins Correlate with CAD/CAM Composite-Dentin Adhesion?
Farid El-Askarya* (faridelaskary@asfd.asu.edu.eg) | Abdullah Hassanienb | Emad Aboalazmb | Nader Maher Tadrosa | Mohamed Amr Kamela | Mutlu Özcanc
aAin Shams University, Cairo, Egypt
bEgyptian-Russian University, Cairo, Egypt
cUniversity of Zürich, Zürich, Switzerland
Objectives: To correlate CAD/CAM composite-dentin micro-tensile bond strength (µTBS) with film thickness (FT), Vicker`s hardness (HV) and ultimate-tensile strength (UTS) of photo- and dual-polymerized luting resins.
Methods: For µTBS, human molars (N=30) were randomly divided into 6-groups according to: 1: Luting-resins [Bifix QM “BF” (dual-polymerized), GrandioSO Heavy-Flow “GHF” (photo-polymerized), and VisCalor-Bulk “VB” (photo-polymerized), VOCO GmbH, Germany] and 2: Adhesive-protocol (Optibond Universal, Kerr); self-etching “SE” and etch-and-rinse “E&R”. CAD/CAM blocks (Grandio blocks, shade A2 HT, VOCO) of 7x7x4 mm were air-abraded (50 μm Al2O3/10s/0.2 MPa). Silane was applied (60 s) and air dried (10 s). All dentin surfaces were wet abraded (#600 SiC/30 s). For E&R mode, dentin was etched (15 s), rinsed (30 s) and blot-dried. For both E&R and SE protocols, adhesive was applied (20 s), air- dried (5 s) and photo-polymerized (10 s). Bonded dentin-CAD/CAM specimens were cut into 1x1 mm sticks. For each group, half of sticks were randomly stored for 24 h and the other half for 6 months (distilled-water/37 °C). After each storage time, sticks were pulled in tension (1 mm/min). Debonded sticks were evaluated for failure mode analysis. For HV, 15- discs (7 mm x 0.5 mm) were prepared from each luting-resin (n=5) and tested using Vicker’s hardness tester. Regarding FT, cemented CAD/CAM slabs (n=9/each luting-resin) were evaluated using stereomicroscope (x40). For UTS, hourglass specimens (1x0.6 mm, n=8/each luting-resin) were prepared and pulled in tension. Data were analysed using ANOVA/Tukey’s and Pearson`s correlation tests (α=0.05).
Results: While correlation between µTBS/HV was not revealed (r=.322, p=.242), strong correlation between µTBS/FT(r=.766, p<.0001) and positive correlation between µTBS/UTS(r=.487, p=.016) were observed. “Luting-resin”, “adhesive-protocol”, and “storage-time”, showed significant effect on µTBS (MPa) (p<0.05); “luting-resin”, GHF(27.4±10.9)=BF(24.3±11.9)>VB(20.7±9.4);“adhesive-protocol”, E&R(25.7±11.1)>SE(22.3±10.8); “storage-time”, 24-h(27.0±10.3)>6-months(20.3±11).
Failure modes: Adhesive=35.8%, mixed=42.1% and cohesive: luting-resin=22.1%, CAD/CAM composite=0.0% and dentin=0.0%. For FT (µm): VB(123.0±19.1)>BF(49.1±13.5)=GHF(41.0±7.0). The HV (Kgf): GHF(91.6±0.4) >VB(76.0±2.5)>BF(70.4±2.6). Regarding UTS (MPa): GHF(112.5±19.7)=VB(98.6±23.1) >BF (67.7±9.2).
Conclusion: Among tested materials, photo-polymerized flowable luting-resin can substitute dual-polymerized resin-cement for CAD/CAM composite-dentin bonding.
Funding/Conflict of Interest: The authors would like to thank VOCO GmbH, Germany for supplying CAD/CAM blocks, photo- and dual-polymerized luting resins used in this study. The authors declare that there is no conflict of interest regarding any materials used in this study.
Keywords: CAD/CAM composite, film thickness, luting resins, micro-tensile bond strength, ultimate tensile strength, hardness
