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macrodontia Teeth that are larger than normal.

magnetic force Repelling and attracting forces created by small rare earth magnets, incorporated in fixed and removable orthodontic appliances to cause changes in tooth position or optimize response in functional magnetic growth guidance appliances.

MRI (Magnetic Resonance Imaging) Creation of images specifically of the TMJ for studies of articular disc position.

mal- Prefix denoting a bad or unfavorable condition. Malalignment, malocclusion, malposition and malrelation are common terms used in describing unfavorable tooth positions.

malocclusion (relationship of teeth in occlusion) A deviation in intramaxillary and/or intermaxillary relations of teeth from normal occlusion. Often associated with other dentofacial deformities. See Angle classification.

malar Relating to the cheek or cheekbone. See zygoma.

mandible The lower jaw.

mandibular resection (osteotomy) Surgical removal of a part of the mandible to allow repositioning of the remaining parts.

mandibular osteotomy Surgical sectioning of the mandible into two or more parts to allow repositioning of the resulting components.

materia alba White accumulation or aggregation of microorganisms, desquamated epithelial cells, blood cells and food debris loosely adhered to surfaces of teeth, soft tissues, dental restorations and orthodontic appliances. Less adherent than plaque, but may change into plaque.

maxilla Paired facial bones that form the base for the upper dental arch, floor of the nose and much of the lower border of the orbit and cheek bones.

maxillary Of or pertaining to the upper jaw. May be used to describe teeth, dental restorations, orthodontic appliances or facial structures.

maxillary osteotomy Surgical sectioning and repositioning of maxillary bone structure to alter bone and jaw relationships.

maximum force An orthodontic force having the greatest magnitude within a range of force values that will produce tooth movement at a clinically acceptable rate.

mechanotherapy Orthodontic treatment by mechanical forces, acting on the dentofacial complex.

mediolateral The global direction perpendicular to a sagittal plane of the dentofacial complex; the medial direction/sense is toward, and the lateral direction/sense is away from the mid-sagittal plane.

menton The most inferior point on the chin in the lateral view. A cephalometric landmark.

mesial Toward or facing the midline, following the dental arch. Used to describe surfaces of teeth, as well as direction.

mesial drift A term applied to either a natural developmental phenomenon whereby the posterior teeth continually move slightly forward as the interproximal surfaces wear or where contiguous teeth are missing and there is movement into that space..

mesioclusion An occlusal relationship in which the lower teeth are positioned mesially relative to the upper teeth, similar to the relationship in an Angle Class III malocclusion.

mesiodens A supernumerary tooth in the midline of the upper alveolar process. Often unerupted, it may inhibit or otherwise disrupt eruption and positioning of the incisor teeth.

mesiodistal The local direction tangent to the ideal arch form and parallel to the occlusal plane; the mesial direction/sense is toward, and the distal direction/sense is away from, the midline of the dentition.

midsagittal plane The imaginary, vertical plane that separates the left and right sides of the dentofacial complex.

mesognathic Position of jaws forward from their normal position in relation to other facial structures.

microdontia Abnormal smallness of teeth.

micrognathia An abnormally small jaw.

migration (dental) Spontaneous movement of a tooth or teeth after eruption.

mixed dentition The developmental stage during which both primary and permanent teeth are present in the mouth (approximately 6 to 12 years of age).

model (dental) Popular name for a cast of a tooth or teeth, usually in plaster or similar material.

moment A tendency to rotate resulting from the application of a force not through the center of resistance of a body. Moments are measured either as 1) the magnitude of a single applied force times the perpendicular distance the force acts away from the center of resistance, or 2) in the case of a couple, the magnitude of one of the forces of the couple times the distance between the forces of the couple.

monobloc A removable activator type orthodontic appliance.

mouthguard A removable elastic appliance used to protect the teeth and supporting tissues while engaging in contact sports.

movement

first order movement Movement of teeth in a faciolingual or y direction; also known as in and out movements.

second order movement Movement of teeth in a mesiodistal, x, direction.

third order movement Movement of teeth in a vertical, z, direction.

MS Master of Science, a degree awarded by a university graduate school, after completion of an advanced dental specialty education program.

MSD Master of  Science in Dentistry, a degree awarded by a dental school after completion of an advanced dental education program.

mucosa The epithelial lining of body cavities opening to the outside. The oral mucosa lines all of the soft tissue surfaces of the mouth.

myalgia Muscle pain.