Influence of drying time and temperature on bond strength of contemporary adhesives to dentine

Objectives

To evaluate the bond strength (μTBS) of self-etching adhesives in different solvent evaporation conditions.

Methods

Flat dentine surfaces from extracted human third molars were bonded with: (1) 2 two-steps self-etching adhesives (Clearfil SE Bond—CSEB); (Protect Bond—PB) and (2) 2 one-step self-etch systems (Adper Prompt L Pop—ADPLP); (Xeno III—XIII). Bonded dentine surfaces were air-dried for 5 s, 20 s, 30 s or 40 s at either 21 °C or 38 °C. Composite build-ups were constructed incrementally. After storage in water for 24 h at 37 °C, the specimens were prepared for microtensile bond strength testing. Data were analyzed by two-way ANOVA and Student–Newman–Keuls at α = 0.05.

Results

CSEB and PB performed better at warm temperature with only 20 s of air-blowing. The bond strength increased when XIII was performed at warm temperature at 40 s air-blowing. Extended air-blowing not affect the performance of ADPLP, except at 30 s air-blowing time at warm temperature.

Conclusions

The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength to self-etching adhesives.     

Experimental induction of an incomplete hard-palate cleft in the rat

Incomplete clefts of the hard palate with soft-palate integrity are among the rarest malformations found in human beings. They appear as oval-shaped openings in the midline of the hard palate and do not extend along its whole length. The amniotic-sac-puncture technique was used to induce such clefts in 10 percent of a group of rat fetuses at day 15.3 of pregnancy. The upper jaws of such fetuses, either 17.3 or 21.3 days old, were examined in the scanning electron microscope and in serial Epon sections. At day 17.3 incomplete clefts of the hard palate were extending toward the soft palate, with the anterior portion of palatal shelves still in the vertical position and with the soft palate already fused. At day 21.3, the incomplete hard-palate clefts were smaller in both extension and width. These observations support the idea that fusion of the soft palate can occur independently of fusion in the hard-palate region.     

Effects of irradiation on grafted skin

The reaction of grafted skin to irradiation was studied in the rat and the optimum time for irradiation postoperatively was determined. There was a close correlation between the radiosensitivity and the vascularity of the graft and its recipient bed. Grafts showed different reactions depending on the time of irradiation after grafting. Those in the early hypovascular stage showed reactions similar to those of normal control skin. Severe reactions were observed in the hypervascular stage. Grafts in the late hypovascular stage showed more moderate reactions.