Orthodontics

Definition

Orthodontics (from Greek orthos "straight" and odont "tooth") is the first specialty created in dentistry. It focuses on the alignment of teeth and the dental arches (the maxilla and the mandible) to improve both function (chewing and speech) and facial aesthetics.

The Biology of Tooth Movement

Orthodontic treatment relies on the physiological process of Bone Remodeling.

Periodontal Ligament (PDL): The sensory tissue that mediates the force between the tooth and the bone.
Osteoclasts: Cells that break down bone on the side where the tooth is being pushed.
Osteoblasts: Cells that build new bone on the side where the tooth is being pulled.

Optimal force must be light and continuous to prevent root resorption.

Angle's Classification of Malocclusion

In 1899, Edward Angle classified the relationship of the teeth into three main groups:

Class I: The "ideal" bite where the mesiobuccal cusp of the upper first molar aligns with the buccal groove of the lower first molar.
Class II: Often characterized by a receding lower jaw or protruding upper teeth (overjet).
Class III: Characterized by a prominent lower jaw or a "crossbite" where lower teeth are in front of upper teeth.

Orthodontic Appliances

Fixed Braces

The most common method, involving:

Brackets: Bonded to the tooth using Adhesive Dentistry techniques.
Archwires: The engine of the movement; often made of Nickel-Titanium (NiTi) for its "shape memory" properties.

Clear Aligner Therapy (CAT)

A modern alternative to braces, such as Orthodontic Aligners. They offer superior aesthetics and oral hygiene but require high patient compliance (22 hours/day wear).

Orthopedic Appliances

Used primarily in growing children to modify jaw growth (e.g., Twin Block, Headgear, or Rapid Palatal Expanders).

Retention Phase

After active treatment, teeth have a natural tendency to return to their original positions (relapse). Retainers are mandatory to allow the bone and ligaments to stabilize:

Fixed Retainers: A wire bonded to the back of the teeth.
Removable Retainers: Clear Essix-style trays or Hawley retainers.