Maxillary canine-tooth mesioversion (MCM) is an inherited disease affecting the Shetland sheepdog breed. The disease is also known as a lance canine, and it is characterised by a developmental dental anomaly characterized by the forward displacement of one or both upper adult canines toward the snout. MCM can have many adverse symptoms including abnormal occlusion, periodontal disease due to closer proximity of the canine
to the upper third incisor, and/or ulceration of the upper lip. Treatment of MCM
includes extraction or orthodontic repositioning. This dental anomaly is observed nearly exclusively in the Shetland Sheepdog breed.
The body size of dogs which are heterozygous for the risk allele is significantly higher compared to dogs which are homozygous for the risk allele. For dogs with two risk alleles there is a strong risk for MCM, for dogs with one copy the weight determines the risk, with lightweight dogs at higher risk.
