An impacted tooth is one that fails to erupt into the dental arch within the expected developmental window. Because impacted teeth do not erupt, they are retained throughout the individuals lifetime unless extracted or exposed surgically. Teeth may become impacted because of adjacent teeth, dense overlying bone, excessive soft tissue or a genetic abnormality. Most often, the cause of impaction is inadequate arch length and space in which to erupt. That is the total length of the alveolar arch is smaller than the tooth arch (the combined mesiodistal width of each tooth). The wisdom teeth (third molars) are frequently impacted because they are the last teeth to erupt in the oral cavity. Mandibular third molars are more commonly impacted than their maxillary counterparts. Some dentists believe that impacted teeth should be removed except, in certain cases, canine teeth: canines may just remain buried and give no further problems, thus not requiring surgical intervention. However, removal of asymptomatic, pathology-free, impacted teeth isnt a medical consensus: watchful monitoring may be a more prudent and cost-effective strategy and make the future placement of a dental implant through such impacted tooth a feasible approach. Classification
Classifications enable the oral surgeon to determine the difficulty in removal of the impacted tooth. The primary factor determining the difficulty is accessibility, which is determined by adjacent teeth or other structures that impair access or delivery pathway. The majority of classification schemes are based on analysis on a radiograph. The most frequently considered factors are discussed below.
In regions of the world where the disease is common eflornithine is provided for free by the World Health Organization. Research
Trypanosomiasis could, in future be prevented by genetically altering the tsetse fly. As the tsetse fly is the main vector of transmission, making the fly immune to the disease by altering its genome could be the main component in an effort to eradicate the disease. New technologies such as CRISPR allowing cheaper and easier genetic engineering could allow for such measures. A pilot program in Senegal, funded by the International Atomic Energy Agency, has considerably reduced the tsetse fly population by introducing male flies which have been sterilized by exposure to gamma rays. This has allowed a change of cattle breeds from lower producing trypanotolerant breeds to higher-producing foreign breeds, and was selected as one of the Best Sustainable Development Practices on Food Security by EXPO Milan 2015. Other animals
Nagana, or animal African trypanosomiasis, also called Souma or Soumaya in Sudan. Surra
Mal de cadeiras, or Quebra Bunda (of central South America, Brazil)
Murrina de caderas (of Panama;  Derrengadera de caderas)
Dourine
Cachexial fevers (various)
Gambian horse sickness (of central Africa)
Baleri  (of Sudan)
Kaodzera  (Rhodesian trypanosomiasis)
Tahaga  (a disease of camels in Algeria)
Galziekte, galzietzke (bilious fever of cattle; gall sickness of South Africa)
Peste-boba (of Venezuela; Derrengadera)Some species of cattle such as the African buffalo, Ndama, and Keteku appear trypanotolerant and do not develop symptoms. Calves are more resistant than adults.Tsetse-borne species of trypanosomes have entered zoos outside the traditional tsetse zone in infected animals imported for the zoo.