Edgewise and Preadjusted Appliance Systems

The edgewise appliance, introduced by Edward Angle, uses a rectangular wire seated edgewise into a rectangular bracket slot, giving three-dimensional control over tooth position. The preadjusted (straight-wire) appliance refines this by building the corrective tip, torque, and in-out values into the brackets themselves, so that a relatively simple, flat archwire can express a planned occlusion with fewer bends.

Definition

Edgewise and preadjusted appliance systems are fixed appliances that use a rectangular archwire in a rectangular bracket slot to control teeth in three planes; the preadjusted version pre-programmes tip, torque, and in-out into the brackets so corrective bends in the wire are minimised.

Scope

This topic explains the edgewise concept and its preadjusted (straight-wire) descendant: how the rectangular slot enables three-dimensional control, what tip, torque, and in-out mean, how Andrews moved that information from the wire into the bracket, and how outcomes of the two approaches have been compared. It is a reference description of these systems, not treatment guidance.

Core questions

• How does the rectangular edgewise slot provide three-dimensional control of teeth?
• What are tip, torque, and in-out, and where are they located in each system?
• How did the preadjusted (straight-wire) appliance change the edgewise approach?
• Do preadjusted and standard edgewise appliances differ in occlusal outcomes?

Key concepts

• Edgewise slot and rectangular wire
• Three-dimensional tooth control
• Tip (mesiodistal angulation)
• Torque (buccolingual root inclination)
• In-out (faciolingual position)
• Preadjusted (straight-wire) prescription
• Wire bending versus bracket programming

Mechanisms

In the edgewise appliance a rectangular wire engaged in a rectangular slot can transmit not only forces but also couples, allowing the operator to control tip, torque, and rotation. In the classic edgewise technique the operator bends this corrective information into the archwire by hand. Andrews' study of naturally normal occlusions defined the positions teeth should occupy and led to the preadjusted appliance, in which the tip, torque, and in-out for each tooth are machined into the bracket; a flat archwire then expresses the prescription as it fully seats (Andrews, 1972; Proffit, 2018). The choice of archwire alloy and size still governs the force used to reach that position (Burstone, 1981).

Clinical relevance

These systems are the dominant labial fixed appliances and form the reference against which other systems are described. This entry explains how they encode and deliver tooth movement for educational purposes and does not provide instructions for treating an individual.

Evidence & guidelines

A systematic review with meta-analysis comparing preadjusted straight-wire and standard edgewise appliances found broadly similar occlusal outcomes between the two, with the preadjusted appliance offering practical efficiencies rather than clearly superior final results (Papageorgiou et al., 2021). Descriptions of the prescriptions and mechanics rely on foundational and textbook sources (Andrews, 1972; Proffit, 2018).

History

Angle introduced the edgewise appliance in the late 1920s, replacing earlier round-wire systems and enabling control in all three planes of space. For decades operators added corrective bends manually. Andrews' six keys to normal occlusion (1972) provided the rationale for the preadjusted appliance, which redistributed corrective information from the wire to the bracket and became the basis of most contemporary labial fixed systems.

Debates

Is the preadjusted appliance better than standard edgewise?

The preadjusted appliance reduces the need for wire bending, but meta-analytic comparison shows broadly similar occlusal outcomes, so its advantage is framed more in efficiency than in superior end results.

Key figures

• Edward H. Angle
• Lawrence F. Andrews
• Charles J. Burstone

Seminal works

• andrews-1972
• burstone-1981

Frequently asked questions

What does edgewise mean?

It refers to placing a rectangular archwire into the bracket slot on edge, which lets the wire transmit the couples needed to control tooth inclination and rotation, not just simple forces.

What is a straight-wire appliance?

It is the preadjusted edgewise appliance in which tip, torque, and in-out are built into each bracket, so a flat archwire can express the planned positions with far fewer bends than the original edgewise technique required.