ABO Orthodontics key terms

A reproducible anatomic point on a skull or soft-tissue profile radiograph used to construct angles and distances for skeletal and dental analysis. Examples include sella, nasion, and point A.

The angle formed by sella, nasion, and point A, expressing the anteroposterior position of the maxilla relative to the cranial base. A larger value suggests a protrusive maxilla.

The angle formed by sella, nasion, and point B, expressing the anteroposterior position of the mandible relative to the cranial base. A larger value suggests a protrusive mandible.

The difference between SNA and SNB, indicating the anteroposterior jaw relationship. Positive values suggest a skeletal Class II pattern; negative values suggest a skeletal Class III pattern.

A reference plane through porion and orbitale used in cephalometrics and facebow transfer. It approximates the natural horizontal orientation of the head for angular measurements.

A system describing the first molar relationship: Class I when the mesiobuccal cusp of the upper first molar occludes in the buccal groove of the lower first molar, Class II when it lies mesial to that groove, and Class III when distal.

The horizontal distance between the incisal edge of the maxillary central incisor and the labial surface of the mandibular central incisor, measured parallel to the occlusal plane. Increased overjet is common in Class II division 1.

The vertical overlap of the maxillary central incisors over the mandibular central incisors. Deep overbite may indicate skeletal or dental vertical discrepancy and can complicate bracket placement.

A discrepancy in which the sum of mesiodistal tooth widths exceeds available arch length, producing overlapping or displaced teeth. Management depends on severity and may include extraction or arch expansion.

The difference between the space required for teeth and the space available in the dental arch. It is quantified during model analysis to decide between non-extraction and extraction treatment.

A method comparing mesiodistal tooth widths of maxillary and mandibular teeth to detect interarch size discrepancies. Anterior and overall ratios guide decisions about tooth extraction or buildup.

Resistance to unwanted tooth movement used to control the reaction forces of orthodontic appliances. Sources include adjacent teeth, palatal structures, extraoral appliances, and temporary skeletal anchorage devices.

A small screw or plate placed in bone to provide skeletal anchorage for tooth movement. It allows intrusion, retraction, or protraction without relying on patient compliance or adjacent teeth.

An extraoral appliance that applies force to the maxilla or maxillary teeth via a facebow and straps. It is used for orthopedic growth modification or anchorage reinforcement and depends on patient compliance.

A device that records the spatial relationship of the maxillary arch to the temporomandibular joints and transfers it to an articulator. In treatment it can also deliver extraoral orthopedic force.

A removable appliance that alters mandibular position to influence muscle activity and skeletal growth, commonly used in growing Class II patients. Examples include the Twin Block and activator.

Orthopedic treatment during active growth that aims to alter the size, shape, or position of the jaws. Success depends on identifying the patient's growth status and remaining growth potential.

A method of estimating skeletal maturity from the shape of cervical vertebrae on a lateral cephalogram. It helps time growth modification and determine whether growth remains.

A malocclusion in which the lower molar is positioned distal to the upper molar relationship, often with increased overjet. It may be dental, skeletal, or a combination.

A malocclusion in which the lower molar is positioned mesial to the upper molar relationship, often with anterior crossbite or negative overjet. It may reflect mandibular prognathism, maxillary deficiency, or both.

An extraoral appliance that applies anteriorly directed force to the maxilla, commonly via a face mask, to correct maxillary deficiency in Class III patients. It is most effective during growth.

A lack of vertical overlap between opposing anterior or posterior teeth. It may be skeletal, dental, or habit-related and can relapse if tongue posture or growth pattern is not addressed.

A pattern in which the tongue moves forward against or between the teeth during swallowing or at rest. It may contribute to open bite or relapse and is often managed with habit therapy.

Exercises and behavioral training that aim to correct abnormal oral muscle patterns such as tongue thrust or lip incompetence. It is often adjunctive to orthodontic treatment.

An abnormal transverse relationship in which a maxillary tooth lies lingual or buccal to its mandibular counterpart. It may be unilateral, bilateral, dental, or skeletal and can affect arch coordination.

An appliance that widens the maxilla by separating the midpalatal suture or tipping teeth buccally. Rapid maxillary expansion is used in growing patients with transverse deficiency.

A maxillary canine that fails to erupt into the arch, often due to insufficient space or abnormal path. Management may involve surgical exposure, orthodontic traction, or extraction.

Eruption of a tooth in an abnormal position, such as a first molar erupting beneath the distal contour of the second primary molar. It may cause premature loss or resorption of adjacent teeth.

The phase after active orthodontic treatment in which appliances or retainers maintain tooth position while tissues reorganize. Duration and type depend on the initial malocclusion and patient factors.

Return of teeth toward their pretreatment positions after treatment. It results from periodontal fiber tension, growth, muscle forces, or inadequate retention.

A bonded wire attached to the lingual surfaces of anterior teeth to maintain alignment. It offers continuous retention but requires monitoring for bond failure and oral hygiene.

A removable appliance system using a series of custom plastic trays to move teeth incrementally. Success depends on case selection, attachment design, and patient compliance with wear time.

A three-dimensional imaging modality that provides detailed views of teeth, bone, and airway with lower radiation than conventional CT. It is useful for impacted teeth, root resorption, and surgical planning.

An examination format presenting a patient scenario with records and asking the candidate to interpret findings, select a diagnosis, and justify a treatment plan.

The process of integrating clinical photographs, radiographs, models, and history to reach a diagnosis and plan. It emphasizes evidence and systematic interpretation over isolated findings.

A structured sequence of interventions addressing a patient's diagnosis, goals, and constraints. It includes appliance choice, extraction decisions, timing, retention, and contingency options.

The process of explaining diagnosis, treatment options, risks, benefits, and alternatives so a patient or guardian can make a voluntary decision. Documentation of the discussion is part of the record.

The certifying body that assesses orthodontists through a written examination and a clinical case examination. Certification is voluntary and distinct from state licensure.

A credential awarded after passing the certifying examinations of a specialty board. It demonstrates that a practitioner has met defined standards beyond initial licensure.