Studies from Asian populations report that the mandibular incisor is most commonly absent.A higher prevalence of hypodontia in females has been reported. The most extensive studies have been in Caucasian populations and suggest a prevalence of 4–6%.One study looked at 33 previous studies with a sample size of 127,000, and concluded that the prevalence of hypodontia in the permanent dentition varied between continents, racial groups and genders. In the white European population they suggested a prevalence of 4.6% in males and 6.3% in females. In an African-American sample they found this to be 3.2% in males and 4.6% in females. The same study found that in the permanent dentition the most likely teeth to be missing and the frequency of these missing teeth was:

Mandibular second premolar 3%
Maxillary lateral incisor 1.7%
Maxillary second premolar 1.5%
Mandibular central incisor 0.3%

References


== External links ==
Comfortis and Trifexis brands treat adult fleas on pets; the latter also prevents heartworm disease. Natroba is sold for treatment of human head lice. Spinosad is also commonly used to kill thrips. Spinosyn A
Spinosyn A does not appear to interact directly with known insecticidal-relevant target sites, but rather acts via a novel mechanism. Spinosyn A resembles a GABA antagonist and is comparable to the effect of avermectin on insect neurons. Spinosyn A is highly active against neonate larvae of the tobacco budworm, Heliothis virescens, and is slightly more biologically active than spinosyn D. In general, spinosyns possessing a methyl group at C6 (spinosyn D-related analogs) tend to be more active and less affected by changes in the rest of the molecule. Spinosyn A is slow to penetrate to the internal fluids of larvae; it is also poorly metabolized once it enters the insect. The apparent lack of spinosyn A metabolism may contribute to its high level of activity, and may compensate for the slow rate of penetration. Resistance
Spinosad resistance has been found in Musca domestica by Liu & Yue 2000, in Plutella xylostella by Sayyed et al 2004, in Bactrocera dorsalis by Hsu & Feng 2006, in Frankliniella occidentalis by Bielza et al 2007, and in Cydia pomonella by Reyes et al 2007; see Insecticide Resistance Action Committees Arthropod Pesticide Resistance Database for continued updates.