Effect of air-blowing time and long-term storage on bond strength of universal adhesives to dentin.

OBJECTIVES: To evaluate the effects of air-blowing time and storage time on microtensile bond strength (µTBS) of universal adhesives to dentin. MATERIALS AND METHODS: Ninety flat dentin surfaces from extracted human third molars were bonded with three universal adhesives (Clearfil Universal Bond-CU; G-Premio Bond-GP; Scotchbond Universal Adhesives-SB). Bonded dentin surfaces were air-dried for 5 s, 15 s, or 30 s followed by resin composite built-up. Resin-dentin beams were tested with µTBS test after different storage time in distilled water (24 h and 1 year). Data were analyzed by three-way ANOVA and Duncan test at (α = 0.05). Failure mode and resin-dentin interfaces were observed using a scanning electron microscope (SEM). Specific features of fractured beams after µTBS were further observed using SEM at high magnification. RESULTS: Extension of air-blowing time from 5 s to 30 s increased the 24 h µTBS of CU only. Bond strength of all adhesives significantly decreased after 1-year storage except for CU at 5 s and 30 s of air-blowing time. One-year µTBS were significantly higher when air-blowing times were extended to 15 s for SB and 30 s for CU. Air-blowing time had no influence on GP. CONCLUSION: The effect of air-blowing time and storage time on resin-dentin bond was material-dependent. CLINICAL RELEVANCE: Extended air-blowing time increased the bond strength and bond durability of CU. Extension of air-blowing time to 15 s and 30 s improve the long-term bond strength of SB and CU, respectively.

Effects of Double Application of a Resin Cement Primer and Different Diamond Burs on Cement-Dentin Bond Strength.

PURPOSE: To evaluate the effects of double application of resin cement primers to dentin prepared with different diamond burs on the cement-dentin bond strengths. MATERIALS AND METHODS: Sixty flat dentin surfaces were prepared and divided into 12 groups (n = 5) according to three experimental factors: 1. resin cements: RelyX Ultimate (RU), Multilink Automix (ML), and Panavia V5 (PV); 2. resin cement primer application: single or double; 3. dentin surface preparation with regular or superfine diamond burs. Cement-dentin sticks (1 mm2) were prepared for and underwent microtensile bond strength testing (µTBS). Statistical analysis was performed using three-way ANOVA and Duncan's test (α = 0.05). Fractured surfaces and cement-dentin interfaces were observed using SEM. Additional teeth were used to observe the demineralization effect of resin cement primers with SEM and transmission electron microscopy (TEM). RESULTS: All tested factors demonstrated significant effects on µTBS (p < 0.001). The combination of PV with superfine-grit bur and double application yielded the highest bond strengths. Surfaces prepared with superfine-grit burs demonstrated higher µTBS than did the regular-grit group, but a significant effect was not observed for all groups. The double application of primer significantly increased the bond strength for most combinations, except for PV with superfine-grit bur-prepared dentin. CONCLUSIONS: PV showed higher bond strengths than other resin cements. Double application of primer improved the bond strength of all cements to dentin. Bond strengths were higher when dentin was prepared with a superfine-grit bur.

Gradual dehydration affects the mechanical properties and bonding outcome of adhesives to dentin.

This study evaluated the effects of dehydration on the mechanical properties of adhesive resins and dentin, and on the microtensile bond strength (µTBS) of adhesives. Third molars were randomly bonded with Clearfil Mega Bond (MB) or Clearfil SE Bond 2 (SE). After water-storage (37°C; 24 h), µTBS was obtained in 'wet' (tested after 5 min of removal from storage) and 'dehydrated' (tested after 10, 15 min and 24 h) conditions by a universal tester (crosshead speed: 1 mm/min). Data were analyzed by two-way ANOVA and Duncan's test. Hardness (H), Elastic modulus (E) and weight-loss of dentin beams and adhesive-resin discs were also monitored over time and analyzed by one-way repeated measures ANOVA and Bonferroni's test (α=0.05). Significant differences in bond strength were observed for adhesives and for conditions. Except for dentin's E, dehydration caused significant gradual changes in the H, E and weight of adhesive resins and dentin (p<0.05).

Effect of different remaining dentin thickness and long term water storage on dentin bond strength.

The purpose of this study was to investigate the effect of remaining dentin thickness (RDT) and long term water storage on dentin bond strength in-vitro. Twenty-seven third molars were randomly divided into 3 groups: Clearfil Bond SE ONE (SE1, Kuraray Noritake Dental, Okayama, Japan), G-Bond plus (GB, GC, Tokyo, Japan) and Clearfil Mega Bond (MB, Kuraray Noritake Dental). Bonded specimens were stored in water at 37ºC for 24 h. The teeth were then sectioned perpendicular to the adhesive interface to produce beams. RDT of each beam was measured digital calliper. Microtensile bond strength testing was carried out at a crosshead speed of 1 mm/min after 24 h and 1 year water storage. Thicker RDT produced higher bond strengths with one/two-step self-etch materials tested except for the group of 24 h MB. Nevertheless water storage time and RDT affected µTBS in all materials used.

The effect of dentine surface preparation and reduced application time of adhesive on bonding strength.

OBJECTIVE: This study evaluated the effects of surface preparation and the application time of adhesives on the resin-dentine bond strengths with universal adhesives. METHODS: Sixty molars were cut to exposed mid-coronal dentine and divided into 12 groups (n=5) based on three factors; (1) adhesive: G-Premio Bond (GP, GC Corp., Tokyo, Japan), Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc., Okayama, Japan) and Scotchbond Universal Adhesive (SB, 3M ESPE, St. Paul, MN, USA); (2) smear layer preparation: SiC paper ground dentine or bur-cut dentine; (3) application time: shortened time or as manufacturer's instruction. Fifteen resin-dentine sticks per group were processed for microtensile bond strength test (µTBS) according to non-trimming technique (1mm(2)) after storage in distilled water (37 °C) for 24h. Data were analyzed by three-way ANOVA and Dunnett T3 tests (α=0.05). Fractured surfaces were observed under scanning electron microscope (SEM). Another 12 teeth were prepared and cut into slices for SEM examination of bonded interfaces. RESULTS: µTBS were higher when bonded to SiC-ground dentine according to manufacturer's instruction. Bonding to bur-cut dentine resulted in significantly lower µTBS (p<0.000). Shortening the application time resulted in significantly lower bond strength for CU on SiC and GP on bur-cut dentine. SEM of fractured surfaces revealed areas with a large amount of porosities at the adhesive resin interface. This was more pronounced when adhesives were bonded with a reduced application time and on bur cut dentine. CLINICAL SIGNIFICANCE: The performance of universal adhesives can be compromised on bur cut dentine and when applied with a reduced application time.