Aim: This study compared the shear bond strength (SBS) and flexural strength (FS) of repaired interfaces using three techniques of surface preparation and repair of a micro-hybrid composite.
Methods And Materials: Composite specimens for SBS tests (n=36: diameter=8 mm, thickness=3 mm) for repair were shaped in a metal mold, visible-light cured, and embedded in dental stone. Composite specimens for FS tests (n=36: 2 mm x 2 mm x 12.5 mm) for repair were shaped in a silicone mold. Three different methods of surface preparation were evaluated: Group A (control) specimens were treated by etching with 35% phosphoric acid; Group B specimens were air-abraded with 50 microm aluminum oxide at 100 psi; and Group C specimens received two parallel, 1 mm-deep grooves using a (1/4)-round bur before being treated by etching with 35% phosphoric acid. After surface treatment, a bonding agent was placed on each specimen, which was then light cured. Repairs were accomplished by adding more composite to the SBS or FS specimens. Specimens were thermocycled 500 times between 5 degrees C and 55 degrees C with 30-second dwell times. All specimens were tested by loading to failure at a rate of 0.5 mm/min using an Instron Universal Testing Machine.
Results: Mean SBSs in MPa were: Group A=24.5 +4.4, Group B=28.5 +4.3, and Group C=27.0 +2.8. Mean FSs (MPa) were: Group A=60.5 +9.9, Group B=73.9 +13.2 and Group C=81.3 +14.3. For the FS tests, Group B and C were significantly different than Group A, but Group C was not significantly different than group B. For the SBS test, Group B was significantly different than Group A, but Group C was not significantly different.
Conclusion: Acid-etching alone was not very effective in producing well-bonded composite repairs (only 55% of the FS of normal micro-hybrid composite). Mechanical retention was more effective (SBS, FS) than acid-etching and as effective (SBS) or more effective (FS) than air-abrasion (p<0.05) for repaired composite specimens.
Clinical Significance: Either mechanical retention or air abrasion is recommended prior to repairing an existing composite restoration to achieve the highest bond strength.
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Acta Crystallogr C Struct Chem
January 2025
College of Chemistry and Materials Science, Anhui Normal University, Wuhu, Anhui 241000, People's Republic of China.
A new twofold interpenetrated 3D metal-organic framework (MOF), namely, poly[[μ-aqua-diaqua{μ-2,2'-[terephthaloylbis(azanediyl)]diacetato}barium(II)] dihydrate], {[Ba(CHNO)(HO)]·2HO}, (I), has been assembled through a combination of the reaction of 2,2'-[terephthaloylbis(azanediyl)]diacetic acid (TPBA, HL) with barium hydroxide and crystallization at low temperature. In the crystal structure of (I), the nine-coordinated Ba ions are bridged by two μ-aqua ligands and two carboxylate μ-O atoms to form a 1D loop-like Ba-O chain, which, together with the other two coordinated water molecules and μ-carboxylate groups, produces a rod-like secondary building unit (SBU). The resultant 1D polynuclear SBUs are further extended into a 3D MOF via the terephthalamide moiety of the ligand as a spacer.
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