Influence of dentin and enamel pretreatment with acidic sulfur compounds on adhesive performance

OBJECTIVE: This study tested the potential hampering effects of acidic sulfur compounds (ASC) containing hydroxybenzene sulfonic acid, hydroxymethoxybenzene sulfonic acid, and sulfuric acid, prior to self-etch and etch-and-rinse bonding procedures on enamel and dentin. According to the manufacturer, ASC should be applied after cavity preparation and prior to application of a primer in order to reduce the remaining biofilm in the preparation cavity. Despite promoted marketing, data on the investigated liquid are almost completely lacking. MATERIAL AND METHODS: One hundred and fifty-two extracted mandibular bovine incisors were embedded and polished to expose either enamel (E) or dentin (D). Then, specimens were randomly divided and conditioned as follows (n = 12/group): ASC and consecutive phosphoric acid application (E1/D1), ASC (E2/D2; E5/D5), phosphoric acid (E3/D3), and no conditioning (E4/D4; E6/D6). Groups were then treated with either Optibond FL(®) (etch-and-rinse; 1-4) or Clearfil SE Bond(®) (self-etch; 5-6). Hollow acrylic cylinders were bonded with a hybrid composite resin (Filtek Supreme XTE®) to the specimens, and the shear bond strength was measured (1 mm/min). In addition, failure types were assessed. Descriptive statistics and statistical analyses were performed with one-way ANOVA followed by the Scheffé post hoc test. RESULTS: For enamel, the highest shear bond strength values were obtained applying routine bonding procedures (23.5 ± 5.6 MPa for etch-and-rinse and 26.0 ± 6.0 MPa for self-etch, respectively). In contrast, dentin pretreatment with a combination of ASC and phosphoric acid led to the highest shear bond values (22.8 ± 4.1 MPa). CONCLUSION: This study shows that ASC prior to dental restoration placement cannot be recommended for etch-and-rinse procedures on enamel but is appropriate for dentin without interfering with routine bonding procedures. CLINICAL RELEVANCE: The application of acidic sulfur compounds prior to adhesive restoration placement should be restricted to dentin only as it may negatively influence shear bond strength on sound enamel

Two Vernier-templated routes to a 24-porphyrin nanoring.

Many hands make light work: Small templates working together have directed the formation of a giant π-conjugated macrocycle with a diameter of 10 nm-larger than many enzymes. The 24 porphyrin subunits of the nanoring are well resolved in the STM image. The conformation of the nanoring can be controlled by self-assembly of a stable 2:24 double-strand sandwich complex with 1,4-diazabicyclo[2.2.2]octane (DABCO). Copyright © 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim