Orthodontics Chapter 4

What is Orthodontics?

• 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.

Prevalence of Malocclusion

• Crowding: ~60%
• Class I: 60%
• Class II/1: 20%
• Class II/2: 10-18%
• Class III: ~5%

Why Orthodontics?

• 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.

Functional Reasons for Rx

• 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).

Index of Orthodontic Treatment Need (IOTN)

• Developed to standardize and quantify the need for orthodontic treatment.
• Severe malocclusion may affect self-esteem and psychological well-being.

What to Refer and When

• 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.

Definitions

• 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.