Magnetic retention and bar-clip attachment for implant-retained auricular prostheses: A comparative analysis

Retention systems for implant-retained auricular prostheses using either bar-clip attachments with 2 or 3 clips or retention with 2 or 3 magnets were wear tested (insertion and removal cycles) to simulate clinical periods of use. Measurements were taken at intervals of 540 cycles, which represents a period of use of approximately 6 months, for up to 3,240 cycles. Assessments of retentive force were carried out before, during, and after the wear test. Statistical analysis indicated that the bar-clip systems provided higher retention than the magnetic systems. The bar-clip attachment with 2 clips showed a significant loss of retentive force after wear testing (P < .05), suggesting lower durability and shorter clinical life. The retention provided by the bar-clip attachment with 3 clips remained stronger than that provided by all other systems tested. At the end of the wear test, the magnetic systems showed very little loss of retention but were still less retentive than the bar-clip systems, suggesting higher durability under clinical simulation despite the lower retention initially provided.

Effects of Nd:YAG Laser Irradiation on the Hybrid Layer of Different Adhesive Systems

Purpose: The aim of this in vitro study was to evaluate the microtensile bond strength (mu TBS) and hybrid layer morphology of different adhesive systems, either followed by treatment with Nd:YAG laser irradiation or not. Previous studies have shown the effects of Nd:YAG laser irradiation on the dentin surface at restoration margins, but there are few reports about the significance of the irradiation on the hybrid layer. Materials and Methods: The flattened coronal and root dentin samples of 24 bovine teeth were randomly divided into 8 groups, according to the adhesive system used - Scotchbond Multi Purpose (SBMP) or Clearfil SE Bond (CSEB) - and were either irradiated with Nd:YAG or not, with different parameters: 0.8 W/10 Hz, 0.8 W/20 Hz, 1.2 W/10 Hz, 1.2 W/20 Hz. The left sides of specimens were the control groups, and right sides were irradiated. A composite crown was built over bonded surfaces and stored in water (24 h at 37 degrees C). Specimens were sectioned vertically into slabs that were subjected to mu TBS testing and observed by SEM. Results: Control groups (27.81 +/- 1.38) showed statistically higher values than lased groups (21.37 +/- 0.99), and CSEB control group values (31.26 +/- 15.71) were statistically higher than those of SBMP (24.3 +/- 10.66). There were no significant differences between CSEB (20.34 +/- 10.01) and SBMP (22.43 +/- 9.82) lased groups. Among parameters tested, 0.8 W/10 Hz showed the highest value (25.54 +/- 11.74). Nd:YAG laser irradiation caused dentin to melt under the adhesive layer of both adhesive systems tested. Conclusion: With the parameters used in this study, Nd:YAG laser irradiation of the hybrid layer promoted morphological changes in dentin and negatively influenced the bond strength of both adhesive systems.

Influence of oil contamination on in vitro bond strength of bonding agents to dental substrates

Purpose: To evaluate the influence of cleaning procedures (pumice, anionic detergent and both procedures together) on the tensile bond strength of etch-and-rinse and self-etch adhesive systems to bovine enamel and dentin in vitro. Methods: Eighty non-carious, bovine incisors were extracted, embedded in acrylic resin to obtain enamel/dentin specimens. Flat bonding surfaces were obtained by grinding. Groups were divided according to substrate (enamel or dentin), adhesive system [etch-and-rinse, Adper Single Bond 2 (SB) or self-etch, Clearfil Protect Bond (PB)]; and cleaning substances (pumice, anionic detergent and their combination). The teeth were randomly divided into 20 groups (n=8): G1 - Enamel (E) + SB; G2 -E + oil (O) + SB; G3 - E + O + Pumice (P) + SB; G4 - E + O + Tergentol (T) + SB; G5 - E + O + P + T + SB; G6 - E + PB; G7 - E + O + PB; G8 - E + O + P + PB; G9 - E + O + T + PB; GIO - E + O + P + T + PB; G11 - Dentin (D) + SB; G12 D + SB + O; G13 - D + SB + O + P; G14 - D + SB + O + T; G15 - D + SB + O + P + T; G16 - D + PB; G17 - D + O + PB +; G18 - D + O + P + PB; G19 - D + O + T + PB; G20 - D + O + P + T + PB. Specimens were contaminated with handpiece oil for 5 seconds before bonding. Adhesive systems and resin composite were applied according to manufacturers` instructions. Specimens were tested in tension after 24 hours of immersion using a universal testing machine at a crosshead speed of 0.5 mm/minute. Bond strengths were analyzed with ANOVA. Failure sites were observed and recorded. Results: Tensile bond strength in MPa were: G1 (23.6 +/- 0.9); G2 (17.3 +/- 2.2); G3 (20.9 +/- 0.9); G4 (20.6 +/- 0.5); G5 (18.7 +/- 2.3); G6 (23.0 +/- 1.0); G7 (21.5 +/- 2.4); G8 (19.9 +/- 1.3); G9 (22.1 +/- 1.2); G10 (19.1 +/- 1.2); G11 (18.8 +/- 1.3); G12 (15.7 +/- 2.1); G13 (17.8 +/- 3.3); G14 (15.3 +/- 2.9); G15 (15.6 +/- 1.9); G16 (14.7 +/- 2.3); G17 (5.5 +/- 0.9); G18 (19.3 +/- 1.8); G19 (15.6 +/- 1.6); G20 (20.3 +/- 3.9). Statistical analysis showed that the main factors substrate and cleaning were statistically significant, as well as the triple interaction between factors of variance. However, the factor adhesive system did not show statistical difference. Oil contamination reduced bond strengths, being less detrimental to enamel than to dentin. Etch-and-rinse (SB) and two-step self-etch (PB) systems had similar bond strengths in the presence of oil contamination. For etch-and-rinse (SB), the cleaning procedures were able to clean enamel, but dentin was better cleaned by pumice. When self-etch (PB) system was used on enamel, anionic detergent was the best cleaning substance, while on dentin the tested procedures were similarly efficient.