BCO flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Arch length discrepancy

The difference between available arch perimeter and the sum of mesiodistal tooth widths. Values under 4 mm per arch are usually resolvable without extraction; over 8 mm often require it.

E-line reference

A line from nose tip to soft-tissue pogonion. In common adult Caucasian references the upper lip sits about 4 mm behind and the lower lip about 2 mm behind this line.

Cervical vertebral maturation

A method staging cervical vertebral shape on lateral cephalograms. Stages CS3 and CS4 bracket the pubertal growth spurt, guiding timing of growth-dependent treatment.

Functional matrix theory

The concept that soft tissue volume and function, such as airway, tongue, and muscles, drive skeletal growth and adaptation rather than bone growth alone determining form.

Center of resistance

The point in a tooth where a force produces pure translation. For a single-rooted tooth it lies roughly one-third of root length apical to the alveolar crest.

Moment-to-force ratio

The ratio of applied moment to force that determines movement type. Matching it to the bracket-to-center-of-resistance distance produces translation; lower values produce tipping.

Hyalinization

Pressure-induced necrosis of periodontal ligament in the lag phase of tooth movement. It follows heavy force and requires undermining resorption before movement resumes.

MBT prescription

A preadjusted bracket system with specified tip, torque, and in-out values. Slot size 0.022 inch accepts 0.019 x 0.025 inch wire for sliding mechanics.

Rapid maxillary expansion

Skeletal widening of the maxilla by activating a jackscrew appliance about 0.5 to 1 mm daily. It splits the midpalatal suture and is most effective before mid-adolescence.

Temporary anchorage device

A small titanium miniscrew, typically 1.2 to 2.0 mm in diameter, placed in bone to provide absolute anchorage for retraction, intrusion, or protraction.

Le Fort I osteotomy

A maxillary surgical procedure that separates the maxilla at the Le Fort I level, allowing advancement, impaction, or setback, commonly 5 to 10 mm.

BSSO

Bilateral sagittal split osteotomy, the standard mandibular orthognathic procedure. It splits the ramus sagittally to allow advancement or setback with rigid internal fixation.

Rule of tens

A timing guideline for cleft lip repair: about 10 weeks of age, 10 pounds of weight, and 10 g/dL hemoglobin, ensuring the infant can tolerate anesthesia.

Alveolar bone grafting

Surgical grafting of the cleft alveolar defect, usually at 6 to 9 years, before the permanent canine erupts, to provide bone support for the tooth.

Velopharyngeal insufficiency

Inadequate closure of the velopharyngeal port causing hypernasal speech. It is assessed by nasoendoscopy and managed with therapy or pharyngeal surgery.

Disc displacement with reduction

A TMJ condition in which the displaced disc reduces on opening, producing a reciprocal click and usually full, if deviated, mandibular opening.

Closed lock

Disc displacement without reduction causing limited opening under about 40 mm, deviation to the affected side, and absence of a click.

Stabilization splint

A hard acrylic appliance with even occlusal contacts used in TMD to reduce parafunction and joint load. It does not permanently alter the occlusion.

Bonded lingual retainer

A fixed wire bonded to the lingual surfaces of anterior teeth, usually canine to canine, providing the most reliable long-term retention against lower incisor relapse.

Supracrestal fiberotomy

Surgical sectioning of gingival fibers around a rotated tooth to reduce rotational relapse. It is performed after orthodontic alignment and before or during retention.

Informed consent

Documented disclosure of diagnosis, treatment options including no treatment, material risks, and the opportunity for questions, signed by the patient or guardian.

Record retention

The professional and legal obligation to keep orthodontic records, commonly 7 to 10 years after the last visit or until the age of majority plus the retention period.

PICO framework

A structure for clinical questions: Population, Intervention, Comparison, and Outcome. It guides literature searching and evidence-based decision making.

Intention-to-treat analysis

An analysis that includes all randomized participants in their assigned groups regardless of compliance, preserving the benefits of randomization and reducing attrition bias.

Funnel plot

A graph of effect size against study precision used to detect publication bias. Asymmetry suggests small negative studies were not published.

Peer assessment rating index

A validated occlusal index scoring malocclusion and treatment change across alignment, overjet, overbite, and buccal relations, used to measure treatment outcome.

SNA angle

A cephalometric angle from sella to nasion to point A, indicating anteroposterior maxillary position relative to the cranial base. The mean is about 82 degrees.

SNB angle

A cephalometric angle from sella to nasion to point B, indicating anteroposterior mandibular position relative to the cranial base. The mean is about 80 degrees.

Anchorage loss

Unwanted movement of the reactive unit during tooth movement, proportional to the reactive force. It is minimized by skeletal anchorage or by grouping posterior teeth.

Self-ligating brackets

Brackets with an integral clip instead of elastomeric ligatures. They reduce but do not eliminate friction, mainly at low wire angulation, and do not shorten treatment reliably.

Orthognathic decompensation

Preoperative orthodontic movement that removes dental compensation, placing incisors in a position that reveals the true skeletal discrepancy before surgical correction.

Nasoalveolar molding

Presurgical infant orthopedics using a plate and nasal stent to approximate alveolar segments and reshape nasal cartilage before cleft lip repair.