Principles of Orthodontic Removable Appliances

These flashcards cover the principles, materials, components, and mechanical concepts of orthodontic removable appliances as detailed in the lecture notes.

Removable Appliance

A term used to describe appliances consisting of an acrylic base plate held in place with clasps, commonly incorporating active components like springs or expansion screws.

Clear Aligners

Thin, transparent removable trays digitally designed using computer-aided technology and 3D-printing to gradually adjust teeth position.

18/8 Stainless-Steel

The material used for orthodontic wires containing $18\%$ chromium and $8\%$ nickel; it is biocompatible, tasteless, and immune to corrosion.

Elasticity

The property which enables a material to return to its original shape and dimension after deformation.

Malleability

The property of a metal to be permanently deformed by compression without cracking.

Deflection

How much an orthodontic wire bends or deforms when a force is applied to it; influenced by material, thickness, force, and wire shape.

Force (F) Formula for Cantilever Springs

The relationship where force is delivered by a spring is defined as $F \propto DR^4/L^3$, where $D$ is deflection, $R$ is radius, and $L$ is length.

Tipping Movement

The simple tooth movement achieved by removable appliances where the crown moves but the root remains relatively stationary.

Buccal Canine Retractor

An active component made of $0.7\,mm$ wire used to move buccally erupted canines distally, occlusally, and palatally.

Double Cantilever (Z-spring)

An active component made of $0.5\,mm$ stainless steel wire used to procline retroclined incisors.

T-spring

An active component used for the buccal movement of premolars ($0.5\,mm$ wire) and molars ($0.6\,mm$ wire).

Palatal Finger Spring

A component used to move a tooth mesiodistally in the line of the arch, often used for closing a midline diastema.

Robert’s Retractor

Used to retrocline proclined upper incisors, constructed with $0.5\,mm$ wire and stainless steel tubing.

Expansion Screw

An active component used to treat crossbites by expanding a narrow maxilla; typically activated by one quarter turn ($0.25\,mm$) per week.

Coffin Spring

An expansion component made of $1.25\,mm$ stainless steel wire used when more than one tooth needs to be moved.

Adam’s Clasp

The standard retentive component in orthodontics made of $0.7\,mm$ wire, featuring arrowheads that engage undercuts.

C-clasp

A retentive component made of $0.7\,mm$ wire used when Adam’s clasp placement is difficult; it engages the undercut below the height of contour.

Southend Clasp

A retentive component made of $0.7\,mm$ wire consisting of two C-clasps connected together.

Ball End Clasp

A $0.7\,mm$ wire retentive component used when there is no undercut, such as in anterior bite plane cases.

Labial Bow

A retentive component made of $0.7\,mm$ wire that contacts the labial surfaces of incisors and includes U-loops.

Anterior Biteplane

An acrylic addition to the baseplate used to reduce excessive overbite by allowing the eruption of posterior teeth.

Posterior Biteplane

An acrylic addition used to temporarily prop the occlusion to allow teeth to move over the bite during the correction of anterior crossbite.

Anchorage

The resistance to unwanted tooth movement, following Newton's Third Law.

Simple Anchorage

Anchorage used when moving a single tooth while intending to keep the adjacent teeth stable.

Reciprocal Anchorage

Anchorage where the force exerted on one set of teeth is balanced by the force on another set, causing both to move in opposite directions.

Stationary Anchorage

When the anchor unit is held firmly to resist tipping and requires much higher forces to move bodily compared to the tooth intended for movement.

Extraoral Anchorage

Anchorage provided by external reinforcement, such as headgear, to distalize posterior teeth.

Temporary Anchorage Devices (TADs)

Also known as miniscrews, these provide skeletal anchorage for orthodontic movements.