Urania has also been used in formulations of enamel and porcelain. The same bacteria also secrete acids that dissolve tooth enamel, causing tooth decay. Fluoride helps prevent decay of a tooth by binding to the hydroxyapatite crystals in enamel. Fluoride helps prevent dental decay by binding to the hydroxyapatite crystals in enamel. The enamel and dentin layers of horse teeth are intertwined. Hydroxyapatite is the main component of tooth enamel. Its coloration is yellowish and it is softer than dentin and enamel. This watch was suspended from a diamond and enamel brooch. Dentin is the substance between enamel or cementum and the pulp chamber. It is made of gold with diamonds, rubies, emeralds, sapphires, enamel and pearls. Borax is a component of many detergents, cosmetics, and enamel glazes. The pulp swells when the protective layers of enamel and dentine are compromised. All sarcopterygians possess teeth covered with true enamel. As the enamel and dentin are destroyed, the cavity becomes more noticeable. Approximately 96% of tooth enamel is composed of minerals.