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iatrogenic An unfavorable response induced by a therapeutic effort.

ideal occlusion A theoretical placement of the teeth in the dental arches which maximizes esthetics function, stability and longevity of the dentition and supporting structures.

idiopathic Pain disease or disorder caused by unknown factors.

imaging The process of acquiring representations of structures in either two or three dimensions.

imbrication An overlap of incisors and canines due to crowding.

immobilization To fix in place so that no movement is possible. Usually used in regard to orthognathic surgery.

impaction (tooth) A condition describing the total or partial lack of eruption of a tooth well after the normal age for eruption.

impaction (surgical) A term usually used to describe orthognathic surgery involving the superior repositioning of the upper jaw. See Le Fort 1.

implant Generally an artificial structure placed into bone, which provides for prosthetic replacement of some missing structure. Also used to describe a graft placed in soft tissue.

impression A negative image of a tooth or dental arch. An impression is produced by placing an elastic compound like alginate in a preformed tray and inserting the tray into the mouth around the teeth until the compound stiffens. The impression is removed from the mouth and filled with plaster to produce an exact positive reproduction of the teeth or dental arch.

incisal Pertaining to the cutting edge of the anterior teeth.

inclination The angle of the long axis of a tooth from a particular line of reference; the tilt or tip of a tooth.

inclined plane An acrylic ledge or platform which is usually added to a maxillary Hawley retainer and is designed to intrude teeth or to position the lower jaw forward.

index of malocclusion A system of measurement to describe and quantify malocclusion characteristics.

indirect bonding A procedure for bonding orthodontic attachments to the teeth. A laboratory process is performed to position the attachments on plaster casts; the prepositioned attachments are then bonded to the teeth utilizing an elastic impression tray as a transfer device.

Individual Practice Association (IPA) A partnership, corporation or other legal entity which contracts with an HMO, union or other provider to provide care to an enrolled group for a fixed monthly amount. In the IPA, the provider can work from his office instead of an HMO center or clinic. Fee-for-service patients can be treated alongside those in the IPA plan. Patients in the IPA plan must use a participating provider. The provider must follow IPA practices, accept reimbursement as full payment and comply with IPA peer review and quality assurance procedures. Typically, the IPA pays the provider a percentage of his fee, with the remaining percentage held in a reserve pool that may be divided at year's end by the provider if any funds remain.

inelastic deformation Deformation of a member sufficiently substantial to exceed the elastic limit of the material and, upon total unloading (deactivation), resulting in a 'permanent set' (a change in geometry/shape from the passive state prior to the deformation).

infection control An important aspect of any health service, following guidelines set by CDC, OSHA, etc.

informed consent An agreement by the patient or parent to proceed with or decline treatment after the benefit and risks of treatment have been presented.

infradentale The highest and most forward point of the alveolar process between the mandibular central incisors.

infraocclusion A tooth or teeth positioned below the normal plane of occlusion.

intensifying screen A stiff sheet of plastic impregnated with a material, which fluoresces when exposed to x-radiation. It is used in an x-ray cassette to intensify the x-ray image and reduce the patient's exposure to radiation. See rare earth screen.

interceptive orthodontics An extension of preventive orthodontics that may include localized tooth movement in an otherwise normal dentition. Such treatment may occur in the primary or transitional dentition and may include such procedures as the redirection of ectopically erupting teeth, correction of isolated dental crossbite or recovery of recent minor space loss where overall space is adequate.

interdental spacing Spacing between the teeth.

interdigitation Intercuspation.

intermaxillary Between the upper and lower jaws.

intermaxillary anchorage Using one dental arch as anchorage to apply traction on the other dental arch.

intermaxillary elastic traction Use of elastics to apply traction between the upper and lower jaws.

intermittent force An orthodontic or orthopedic force that is inactive for intervals of time during the between-appointments period, often exhibiting a cyclic, long-term, magnitude-time pattern (e.g., force exerted by an extraoral appliance worn only at night).

internal derangement An intracapsular problem of the TMJ which may relate to arthritis, fibrosis, tumors, condylolysis, condylar hyperplasia or other internal factors. This condition often reflects a displacement or malrelation of the articular disk to the condyle and articular eminence.

interocclusal clearance Synonymous with freeway space.

intramaxillary Within one dental arch.

intramaxillary anchorage A situation where a tooth or group of teeth provides anchorage to apply traction to other teeth within the same arch.

intraoral anchorage Anchorage located inside the mouth.

intraoral force Force which is generated by orthodontic appliances in the oral cavity.

intrusion A translational form of tooth movement directed apically and parallel to the long axis.