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early orthodontic treatment Orthodontic treatment started while patient is still in transitional or primary dentition.

ectopic Located away from normal position; often used to describe a condition in which a tooth develops or erupts in an abnormal position.

edge-to-edge occlusion An occlusion in which the anterior or posterior teeth of both jaws meet along their incisal or buccal cuspal edges. Often associated with a Class III molar relationship.

edgewise appliance A fixed orthodontic appliance characterized by attachment brackets with a rectangular slot for engagement of an orthodontic wire. The most common appliance in use today.

elastic A flexible appliance element, that exhibits substantial elastic range (noun); descriptive of material behavior such that, upon unloading from a deformed state, recovery is totally to the configuration prior to loading (adjective).

elastics (rubber bands) Variously used as Class II elastics, Class III elastics, Diagonal elastics, Up-down (vertical) elastics and cross-elastics. Usually made of latex.

elastic deformation A deformation not sufficiently severe to take the most strained element of a body beyond the elastic limit of the material.

elastic limit The limit of load, stress, deformation, or strain beyond which the loaded (activated) body will exhibit permanent deformation (a new passive shape) upon complete unloading (deactivation).

elastic range The deformation or strain coordinate of the elastic limit.

elastic strength The load or stress coordinate of the elastic limit.

elastomeric ligature A polymeric or rubber band or thread that is stretched around the tie-wings of an orthodontic bracket for the purpose of preventing disengagement of an arch wire or auxiliary from the bracket-slot.

emergence Coming out of; often used to describe the initial appearance of a tooth as it breaks through the gingival tissue during eruption.

enucleate A surgical procedure for removal of a complete structure, such as an unerupted tooth or a cyst.

equilibrate Reshaping the occlusal (functional) surfaces of the teeth to alter the functional relationship; redistributing and balancing the functional load.

eruption Movement of teeth in an incisal or occlusal direction through the supporting bone and gingival tissue into the oral cavity.

esthetics,facial See facial esthetics.

etch The application of a weak acidic solution to the labial or lingual surfaces of teeth as part of the preparation for bonding orthodontic attachments to the teeth.

etiology The cause of a medical or dental condition. 

excessive force Force delivered by an orthodontic appliance of such magnitude that it may damage supporting tissue or cause anchorage loss.

exfoliate Physiological loss or shedding, as when a primary tooth is lost prior to the eruption of the permanent tooth.

exostosis An overgrowth of bone which results in a bony projection, as a tori or spur.

expansion Enlargement;often used to describe the mechanical widening of the dental arches.

expansion key An instrument used to turn the jackscrew in an expansion appliance.

expansion screw A mechanical device incorporated in a removable appliance or a fixed appliance used to enlarge the dental arch in some dimension.

expansion,rapid palatal (RPE) See rapid palatal expansion.

extraction Removal of a tooth.

extraction,serial See serial extraction.

extraoral anchorage Anchorage located outside the mouth.

extraoral force or traction Force originating outside the oral cavity.

extrusion A translational form of tooth displacement with movement occlusally directed and parallel to the long axis.