<p>Mirror-writing is the production of letters, words or sentences in reverse direction, so that they look normal when viewed in a mirror. Some people may mirror-write intentionally;</p><p><br></p><p>Picture yourself in a taxi on a cold, rainy day, condensation on the s. You want to write ‘bye-bye’ to your daughter waving at you from the house. In order to be read by her, you would need to write in reverse on the inside of the , transforming your habitual writing actions to do so. This is ‘mirror-writing’ – reversed writing that looks normal when viewed in a mirror; like the sign on the front of an ambulance. Since Western s typically run from left to right</p> <p>Wisdom teeth (third molars) become impacted because they don't have enough room to come in (erupt) or develop normally.</p><p>Wisdom teeth usually emerge sometime between the ages of 17 and 25. Some people have wisdom teeth that emerge without any problems and line up with the other teeth behind the second molars. In many cases, however, the mouth is too crowded for third molars to develop normally. These crowded third molars become trapped (impacted</p><p><br></p><p>Impacted wisdom teeth are third molars at the back of the mouth that don't have enough room to emerge or develop normally.</p><p><br></p><p>Wisdom teeth are the last adult teeth to come into the mouth (erupt). Most people have four wisdom teeth at the back of the mouth — two on the top, two on the bottom.</p><p>Symptoms</p><p>Impacted wisdom teeth don't always cause symptoms. However, when an impacted wisdom tooth becomes infected, damages other teeth or causes other dental problems, you may experience some of these signs or symptoms:</p><p>Red or swollen gums</p><p>Tender or bleeding gums</p><p>Jaw pain</p><p>Swelling around the jaw</p><p>Bad breath</p><p>An unpleasant taste in your mouth</p><p>Difficulty opening your mouth</p><p>When to see a doctor</p><p>See your dentist if you experience symptoms in the area behind your last molar that may be associated with an impacted wisdom tooth.</p> <p>Enamel [ɪˈnæml]牙釉质</p><p>Dentin:[ˈdɛntən]牙本质</p><p>Pulp 牙髓</p> <p>What are incisors?</p><p>Your eight incisor teeth are located in the front part of your mouth. You have four of them in your upper jaw and four in your lower jaw.</p><p>Incisors are shaped like small chisels [ˈtʃɪzlz]. They have sharp edges that help you bite into food. Whenever you sink your teeth into something, such as an apple, you use your incisor teeth.</p><p>Incisors are usually the first set of teeth to erupt, appearing at about 6 months old. The adult set grows in between the ages of 6 and 8.</p><p><br></p><p>What are canines?</p><p>Your four canine teeth sit next to the incisors. You have two canines on the top of your mouth and two on the bottom.</p><p>Canines have a sharp, pointy surface for tearing food.</p><p>The first baby canines come in between the ages of 16 months and 20 months. The upper canines grow in first, followed by the lower canines.</p><p>Lower adult canines emerge in the opposite way. First, the lower canines poke through the gums around age 9, then the upper canines come in at age 11 or 12.</p><p>What are premolars?</p><p>Your eight premolars sit next to your canines. There are four premolars on top, and four on the bottom.</p><p>Premolars are bigger than canines and incisors. They have a flat surface with ridges for crushing and grinding food into smaller pieces to make it easier to swallow.</p><p>Baby molar teeth are replaced by adult premolars. Infants and young children don’t have premolars because these teeth don’t start to come in until around age 10.</p><p>What are molars?</p><p>Your 12 molars are your biggest and strongest teeth. You have six on the top and six on the bottom. The main eight molars are sometimes divided into your 6-year and 12-year molars, based on when they typically grow in.</p><p>The large surface area of your molars helps them grind up food. When you eat, your tongue pushes food to the back of your mouth. Then, your molars break up the food into pieces small enough for you to swallow.</p><p>The molars include four wisdom teeth, which are the last set of teeth to come in. They usually come in between the ages of 17 and 25. Wisdom teeth are also called third molars.</p><p>Not everyone has enough room in their mouth for this last group of teeth. Sometimes, the wisdom teeth are impacted, meaning they’re stuck under the gums. This means they don’t have space to grow in. If you don’t have room for your wisdom teeth, you’ll likely have to have them removed.</p><p>The bottom line</p><p>Your 32 teeth are essential for biting and grinding up food. You also need your teeth to help you speak clearly. While your teeth are solidly built, they won’t last a lifetime unless you take good care of them.</p><p>To keep your teeth in good shape, floss and brush regularly, and follow up with professional dental cleanings every six months.</p>