Crossbite is a form of malocclusion where a tooth (or teeth) has a more buccal or lingual position (that is, the tooth is either closer to the cheek or to the tongue) than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches. Anterior crossbite
An anterior crossbite can be referred as negative overjet, and is typical of class III skeletal relations (prognathism). Primary/mixed dentitions
An anterior crossbite in a child with baby teeth or mixed dentition may happen due to either dental misalignment or skeletal misalignment. Dental causes may be due to displacement of one or two teeth, where skeletal causes involve either mandibular hyperplasia, maxillary hypoplasia or combination of both. Dental crossbite
An anterior crossbite due to dental component involves displacement of either maxillary central or lateral incisors lingual to their original erupting positions. This may happen due to delayed eruption of the primary teeth leading to permanent teeth moving lingual to their primary predecessors. This will lead to anterior crossbite where upon biting, upper teeth are behind the lower front teeth and may involve few or all frontal incisors. In this type of crossbite, the maxillary and mandibular proportions are normal to each other and to the cranial base. Another reason that may lead to a dental crossbite is crowding in the maxillary arch. Permanent teeth will tend to erupt lingual to the primary teeth in presence of crowding.
Sarcosinemia (SAR), also called hypersarcosinemia and SARDH deficiency, is a rare autosomal recessive metabolic disorder characterized by an increased concentration of sarcosine in blood plasma and urine ("sarcosinuria"). It can result from an inborn error of sarcosine metabolism, or from severe folate deficiency related to the folate requirement for the conversion of sarcosine to glycine. It is thought to be a relatively benign condition. Cause
Sarcosinemia is thought to be caused by a mutation in the sarcosine dehydrogenase (SARDH) gene, which is located at human chromosome 9q34.The disease is inherited in an autosomal recessive manner, which means the defective gene responsible for the disorder is located on an autosome (chromosome 9 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder. Diagnosis
Treatment
See also
Inborn errors of metabolism

References
External links
Sarcosinemia at NIHs Office of Rare Diseases