Tooth Structure Removed in Primary Molar Prefabricated Crown Preparations of Typodont Teeth.

Purpose: Esthetic prefabricated pediatric crowns require more tooth reduction than stainless steel crowns due to their passive fit. The purpose of this study was to determine tooth reduction in primary molar preparations for various pediatric prefabricated crowns.

Methods: Fifty primary maxillary and fifty mandibular typodont molars were scanned with an optical scanner.

Justifying the risks of COVID-19 challenge trials: The analogy with organ donation.

In the beginning of the COVID pandemic, researchers and bioethicists called for human challenge trials to hasten the development of a vaccine for COVID. However, the fact that we lacked a specific, highly effective treatment for COVID led many to argue that a COVID challenge trial would be unethical and we ought to pursue traditional phase III testing instead. These ethical objections to challenge trials may have slowed the progress of a COVID vaccine, so it is important to evaluate their merit.