Q:"Not long ago you listed the tooth eruption times for ferrets. Can you repost it, but with more explaination of the teeth?...I think it would it be useful in aging [kits] from pet stores...." A: Useful is as useful does. The majority of mammals have 4 basic types of teeth; Incisors, Canines, Premolars and Molars. Not all mammals; some, like dolphins or anteaters have "molarform" teeth, but--as embryos--the basic four are there. Many mammals have lost some of the basic four, and in many cases, the basic shape has been changed, so the tooth is hard to identify. For example, bovids (cattle, sheep, deer) look like they have 8 lower incisors, but really they have 6; 2 canines only look like incisors. Mammals also have two set of teeth; the baby teeth (deciduous) and the permanent teeth. In some mammals, the baby teeth are lost prior to birth, and in others, teeth are completely resorbed without eruption, but most have both sets. There is an established sequence of tooth eruption and loss for each species of animal. For example, baby molars are not lost until the permanent molars have erupted, and then they are replaced by premolars. Not all species grow or lose teeth in the same order or at the same time, but within species it is quite consistent providing diet and health remain constant. While teeth are made of the same basic substance as bone, because of the way the crystals are laid down and the lack of water, teeth are the hardest substance in the body. They are quite capable of crushing, cutting, and fracturing bones; yet regardless of their hardness, they still continuously wear down. Unlike bones, teeth cannot repair themselves when broken. A broken tooth is permanently injured. Because of chewing stress and wear, the nerve and blood supply slowly withdraws from the root canal, and the space is filled with dentine. This gives the tooth a transparent look because changes of how light passes through the enamel have taken place. Small holes into the root canal are generally plugged with dentine within a short period of time. Incisors are the front teeth and are used for grooming, grasping, pulling and holding. Ferrets have 12; 6 on both the top and bottom (3 each side). The third one on each side of the top is larger than the rest and a little more pointed, the rest being chisel- or peg-like. In ferrets, it is common for the incisors to overlap, making the tooth row look uneven. Maybe 1 ferret in 1000 has an extra incisor, almost always on top, in the middle. This "supernumerary" tooth is almost always a baby tooth that is never lost and there is no need to remove it. The incisors are rarely broken or lost, but such injury is unimportant to the health of the ferret, provide infections do not occur. Incisor eruption: Deciduous = 0(4)10 days; Permanent = 20(22)30 days. The first number is the earliest date erupted, the middle number is the average or typical date, and the last number is the latest date. Canines are the long fangs and are used for killing, protection, tearing and ripping. Ferrets have 4; 2 on top (1 each side) and 2 on bottom (1 each side). The top canines are generally longer and slightly more curved. In ferrets, the top canines are frequently injured, either by chipping the tip, or a gum-line break. While the ferret has a diminished ability to protect itself from aggressive ferrets or larger predators, the loss of the canine in pet ferrets is displeasing, but essentially unimportant. Canine eruption: Deciduous = 20(20)30 days; Permanent = 45(50)55 days. Premolars are the teeth between the canines and the permanent molars and are used to cut, crush and tear. Ferrets have 12, 6 each on the top and bottom (3 on each side). Although the name implies they look like molars, that is not always true. In ferret deciduous teeth, the front ones look like little cones (if you can see them), and the back one is a cutting tooth, called the sectorial or carnassial. In the permanent dentition, the front premolars are conical or triangular shaped. The last premolar (PM4) in the top jaw is the cutting tooth. The loss of one of the conical or triangular premolars is relatively unimportant, but the loss of the cutting premolar is a serious problem because this tooth is used to cut food small enough to swallow. Premolar eruption: Deciduous: pm2 = 24(28)32 days, pm3 = 20(20)45 days, pm4 = 20(20)50 days. Permanent: PM2 = 55(60)65, Upper PM3 = 55(60)65 days, Lower PM3 = 63(67)70, Upper PM4 = 55(60)65, Lower PM4 = 55(74)80. Molars do not have a deciduous form; they are only found in the permanent dentition and are generally used to crush food, although in the ferret they are also used for cutting muscle and bone. Molars don't have to look like molars; in the ferret one is a cutting tooth. Ferrets have 6 molars; 2 on top (1 each side) and 4 on bottom (2 each side). The top molar is a small, oval shaped flat tooth. The 1st molar on the bottom is a cutting (carnassial) tooth. The 2nd molar is a tiny roundish flat tooth. The loss of the tiny molars can impact somewhat on the chewing ability of the ferret, but not much. The loss of the cutting molar is a serious problem. Molar eruption: Upper M1 = 48(53)55, Lower M1 = 48(50)53, Lower M2 70(74)80. The typical eruption date (within parentheses) assumes the ferret is healthy, well-fed and "average." The range of dates reflects individual variation, nutritional status, and impact of disease and stress. What this means is, just because the lower M2 (2nd Molar) is erupting, it doesn't mean the ferret is 74 days old. It could be between 70 and 80 days old. Most will be around 74 days old, but you cannot be sure if yours is one of them, so use qualifier words like "about" or "approximately." Bob C and 19 Mo' Tooth Terrorists [Posted in FML issue 2651]