Horse teeth wild forebears never faced. Typical wear patterns in horses include: A horse's incisors, premolars, and molars, once fully developed, continue to erupt as the grinding surface is worn down through chewing. A young adult horse's teeth are typically 4.5–5 inches long, but the majority of the crown remaining below the gumline in the dental socket. The rest of the tooth slowly emerges from the jaw, erupting about 1/8" each year, as the horse ages. When the animal reaches old age, the crowns of the teeth are very short and the teeth are often lost altogether. Very old horses, if lacking
Hinge teeth sides). This arrangement is characteristic of the venus clams (Veneridae), the cockles (Cardiidae) and several other important groups. In the "desmodont" hinge, also known as an "asthenodont" hinge, the hinge consists of a large ligamentous resilifer (or chondrophore) which replaces the cardinal teeth, as in the soft-shell clams (Myidae). The "anodont" hinge is characterized by a strong ligament (or a series of transverse ligamental grooves as in the "Isognomonidae"), however, true teeth are absent in adults as is the case in the pen shells (Pinnidae), tree oysters (Isognomonidae), the pearl oysters (Pteriidae), and some freshwater mussels such as the genus