Orthodontic appliances

Techniques and stages of treatment with bracket systems

Modern orthodontics relies on a number of basic concepts. These include the bioprogressive technique and the straight-wire technique. A key feature of the straight-wire technique is that the final, physiologically correct position of the tooth is already predetermined in the design parameters of the bracket.

The process of applying a fixed bracket system can be divided into three consecutive stages:

1. First stage: aims at initial alignment of the teeth in the dental arch. At this stage, teeth are guided onto the occlusal line, and derotation (correction of undesirable rotations) takes place.
2. Second stage: involves torque control, complete closure of existing interdental spaces, and correction of the occlusal curve.
3. Third stage: final detailing. The clinician makes fine adjustments to the position of each tooth and achieves ideal interdental contacts.

Biomechanics: types of tooth movement

Orthodontic appliances generate forces that cause various types of tooth movement in space:

• Bodily movement (translation) — the root and the crown of the tooth move simultaneously, in the same direction, and by the same distance. Types of bodily displacement include:
• Intrusion ("pressing" into the bone);
• Extrusion ("pulling" out of the bone);
• Tortorotation (rotation strictly along the long axis);
• Vestibular displacement (towards the cheek) and palatal/lingual displacement (towards the oral cavity);
• Mesial (forward along the arch) and distal (backward along the arch).
• Inclined-rotational movement — the root and crown travel different distances. Here, the center of rotation is located apically (closer to the root apex) to the center of resistance. It is carried out in the mesiodistal or vestibuloral directions.
• Torque — a specific type of inclined-rotational movement in the vestibuloral direction, where the center of rotation is located in the coronal part.

Allied surgical methods

To enhance the effectiveness of orthodontic appliances, adjunctive surgical and manipulative interventions are often required:

• Tooth extraction: performed according to strict orthodontic indications to create space. Premolars, third molars, or a lower incisor are most frequently extracted.
• Soft tissue surgery (plastic surgery): includes frenuloplasty of the upper and lower lips, and tongue, as well as vestibuloplasty in cases of a shallow oral vestibule.
• Crown exposure: necessary for impacted teeth to provide access for their subsequent extrusion using orthodontic traction.
• Corticotomy: surgical disruption of the integrity of the dense cortical plate of the jaw bone. This reduces tissue resistance and accelerates root movement.
• Transection of the circular ligament (fibrotomy): performed with a scalpel directly around the tooth with the fixed bracket.

Additional treatment and prevention methods

Comprehensive management of patients with dentofacial anomalies also utilizes:

• Interdental separation (stripping): reduction of a small volume of contact enamel surfaces using separation strips to gain additional space.
• Grinding of cusps of primary teeth.
• Prosthetic treatment: indicated in the presence of hard dental tissue pathology, as well as pronounced defects of the dental arches and jaw bones.
• Cranial therapy and therapeutic exercises.

Class and exam questions

What else to study on this topic

• Endogenous and exogenous (prenatal) causes of dentofacial anomalies.
• Physiology and distinctive features of primary and mixed dentition.
• Classification of dental and jaw anomalies (tortoanomaly, retention, hyperdontia).
• Classification of sagittal lateral bite anomalies.
• Modern theories of tooth movement biomechanics.
• Structural elements of the bracket system and functions of retention appliances.

Other topics in "Chapter 11. Introduction to Orthodontics"

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.