Orthodontics Chapter 4

Study Notes

Orthodontics is the branch of dentistry concerned with the growth of the face, development of the dentition, and prevention and correction of occlusal anomalies.
Ortho (from Greek) means straight.
Malocclusion is not a disease, but a variation from ideal occlusion.

Aesthetics and function are the main indications for orthodontic treatment.
Research shows that individual motivation has more effect upon the presence of plaque than alignment of the teeth.

Deep traumatic overbite, especially if the lips are incompetent (i risk of trauma).
Labial crowding of a lower incisor (as this reduces periodontal support labially).

Primary dentition:
- Cleft lip and/or palate (if patient not under the care of a cleft team).
- Other craniofacial anomalies (if patient not under the care of a multidisciplinary team).
Early mixed dentition:
- Delayed eruption of the permanent incisors.
- Impaction or failure of eruption of the 6s.
- Severe Class III skeletal problems suitable for orthopaedic Rx with protraction facemask.
Late mixed dentition:
- Growth modification of skeletal Class II malocclusions.
- Hypodontia.
- Most routine problems.

Ideal occlusion: Anatomically perfect arrangement of the teeth.
Normal occlusion: Acceptable variation from ideal occlusion.
Competent lips: Lips meet with minimal or no muscle activity.
Incompetent lips: Evident muscle activity is required for lips to meet.
Frankfort plane: Line joining porion (superior aspect of external auditory meatus) with orbitale (lowermost point of bony orbit).
Class I: Lower incisor edges occlude with, or lie immediately below, the cingulum of upper incisors.
Class II:
- Division 1: Upper central incisors are upright or proclined and the o/j is i.
- Division 2: Upper central incisors are retroclined and the o/j is usually d but may be i.
Class III: Lower incisor edges lie anterior to the cingulum of the upper incisors and the o/j is d or reversed.
Bimaxillary proclination: Both upper and lower incisors are proclined.
Overjet: Distance between the upper and lower incisors in the horizontal plane.
Overbite: Overlap of the incisors in the vertical plane.
Complete overbite: Lower incisors contact the upper incisors or the palatal mucosa.