Tooth-composite bond failure with a universal and an etch-and-rinse adhesive depending on mode and frequency of application

OBJECTIVES

To evaluate the effect of an additional layer of universal adhesive on the interfacial enamel/dentin-composite gap formation in relation to application mode and aging, via spectral domain optical coherence tomography (SD-OCT) and scanning electron microscopy (SEM).

METHODS

In vitro class V cavities in 114 caries-free premolars were restored by applying one or two layers of a universal adhesive (Scotchbond Universal, SBU) in self-etch (se) and etch-and-rinse (er) mode or the reference adhesive OptiBond FL (OFL-er). The restorations were imaged by SD-OCT (six groups, n = 8) and SEM (n = 3) directly after filling (t1), water storage (t2, 24 h), embedding (t3), and thermo-mechanical loading (t4, TCML). The interfacial gaps were quantified using 26 parameters and analyzed using principal component analysis and linear mixed effect models.

RESULTS

Gap formation at enamel and dentin was significantly influenced by the adhesive, the application mode and number of layers (p < 0.001). This was due to the influence of the SBU-er mode (p < 1e-05), which showed significantly more gap formation and a greater range of variation with double application when compared to SBU-se and OFL. The fewest interfacial gaps occurred with one or two applications of OFL-er and one layer of SBU-er.

SIGNIFICANCE

Adhesive application mode and the number of adhesive layers are relevant factors in the tooth-composite bond failure. Double application worsened the adaptation of SBU to freshly prepared dentin conditioned with phosphoric acid.

Kinetics of allopurinol after single intravenous and oral doses. Noninteraction with benzbromarone and hydrochlorothiazide

An high-pressure liquid chromatographic method was used to measure allopurinol and oxipurinol in plasma and urine in 6 healthy volunteers after a single intravenous or oral dose of allopurinol. The influence of coadministered benzbromarone and hydrochlorothiazide on the pharmacokinetics of allopurinol and oxipurinol was also investigated. After intravenous injection of allopurinol 300 mg the plasma disappearance was biexponential, with a mean distribution half-life of 2.32 +/- 1.08 min (mean +/- SD) and an elimination half-life of 47.8 +/- 10.6 min. The total clearance of allopurinol was 11.37 +/- 2.70 ml/min/kg, whereas its renal clearance was only 1.73 +/- 0.79 ml/min/kg. Oxipurinol disappeared monoexponentially from plasma with a mean half-life of 12.2 +/- 2.6 h. Its renal clearance was 0.42 +/- 0.091 ml/min/kg. After oral administration of allopurinol 300 mg the peak plasma concentration of 2.1 +/- 0.6 micrograms/ml (1.5 x 10(-5) M) was reached within 30 to 120 min. The peak level of oxipurinol of 5.8 +/- 1.5 micrograms/ml (3.8 x 10(-5) M) was found within 2 to 5 h after intravenous and oral allopurinol. The bioavailability of oral allopurinol computed from plasma data was 90.4 +/- 8.7%. The total recovery from urine was 77% (allopurinol 8%, oxipurinol 69%) after oral and 88% after i.v. administration. It was concluded that about 10% of the oral dose was not absorbed and that 12% was eliminated by an unknown mechanism, presumably as riboside. The pharmacokinetics of allopurinol and oxipurinol were not significantly influenced by coadministration of benzbromarone or hydrochlorothiazide.