Related Experiment Video
Updated: Jan 31, 2026

Accuracy in Dental Medicine, A New Way to Measure Trueness and Precision
Published on: April 29, 2014
Dental Sealants Part 4: Bisphenol A: What dentists should know
S Colombo1, M Beretta2, G F Ferrazzano3
1Department of Paediatric Dentistry, Istituto Stomatologico Italiano (ISI), Milan, Italy.
Background:
Bisphenol A (BPA) is a synthetic chemical resin used worldwide to produce plastic products. It is also a component of the bisphenol A diglycidylether methacrylate (Bis-GMA), which is a monomer found in dental resin-based materials (including resin-based dental sealants, RBSs). The controversy about its possible toxicity begins around the early '30s. Even if the amount of BPA released by dental sealants is well below the limit proposed by the U.S. Environmental Protection Agency and the European Food Safety Authority, we can reduce the risk of exposure, particularly for children, following precautionary measures.
Related Concept Videos
Dipeptidyl Peptidase 4 Inhibitors
Amides to Amines: LiAlH4 Reduction
Amide reduction requires two equivalents of the reducing agent, acting as a source of hydride ions. As shown in the figure, the reaction is initiated with a nucleophilic attack by the hydride ion at the carbonyl carbon to form a tetrahedral intermediate.
Piaget's Stage 4 of Cognitive Development
Abstract Reasoning and Hypothetical-Deductive Thinking
Unlike the concrete operational...
Nitriles to Amines: LiAlH4 Reduction
As shown below, the mechanism involves three steps. Firstly, the hydride ion acting as a nucleophile attacks the nitrile carbon to form an anion. In the second step, a second equivalent of the hydride ion attacks the anion to...
Acid Halides to Alcohols: LiAlH4 Reduction
The mechanism proceeds in three steps. First, the nucleophilic hydride ion attacks the carbonyl carbon of the acid halide to form a tetrahedral intermediate. Next, the carbonyl group is re-formed, and the halide ion departs as a leaving group, generating an aldehyde. A second nucleophilic attack by the hydride yields an alkoxide ion, which, upon protonation, gives a primary alcohol as...
Criteria for Aromaticity and the Hückel 4n + 2 Rule
For the first time, Eric Hückel, a German chemical physicist, derived a set of structural features for a compound to be classified as aromatic. This is now known as Hückel’s rule or the 4n +...

