Introduction to orthodontics Flashcards
What is orthodontics?
Branch of dentistry concerned with facial growth, dentition development and occlusion, and with the diagnosis, interception and treatment of occlusal anomalies.
During which stage of development may developmental abnormalities be identified ?
Mixed dentition (ages 6-13)
What type of radiograph is used to investigate possible development abnormalities e.g. ectopic teeth?
OPT
Possible causes of ectopic teeth
Supernumerary tooth blocking eruption pathway, or displacement of tooth germ due to trauma
How can an ectopic tooth be surgically exposed?
Using a metal gold plate to pull downwards on the tooth
Type of malocclusion where an upper anterior tooth is posterior to the lower anterior teeth
Anterior crossbite
Why should an anterior crossbite be resolved ASAP?
Anterior crossbite may cause enamel wear due to attrition, gum recession and mobile teeth
What is an increased overjet?
Type of malocclusion where upper anterior teeth protrude more than 4 mm infront of lower anterior teeth
What is overjet?
Horizontal distance between upper and lower incisors. normal overjet is 2-4mm
What is a reverse overjet?
type of malocclusion where lower incisors protrude infront of upper incisors. (may be the case in class III)
Which AP jaw relationship is more likely to cause a reverse overjet?
Class III
What is a posterior crossbite?
Type of malocclusion where the buccal cusps of the lower posterior teeth occlude buccally to the buccal cusps of the upper posterior teeth.
How does the arch length increase to accommodate for the 6, 7, 8?
Arch length increases posterior to first deciduous molar (not infront)
What is the Leeway space?
The difference in mesio-distal diameter between c, d, e and 3, 4, 5
How much greater is the Leeway space of the deciduous dentition in the maxilla?
1.5 mm
How much greater is the Leeway space of the deciduous dentition in the mandible?
2.5 mm
Function of the Leeway space
creates more space to prevent crowding in the permanent dentition.
Which teeth are commonly extracted to resolve crowding?
Premolars (4/5s)
Name of eruption abnormality in which there is an interchange in position of 2 teeth
transposition
Cause of ectopic canine
can get stuck in the palate (palatal ectopic canine- palpate the palate for the canine
How can an ectopic canine be resolved?
By surgical exposure
What percentage of the population has an ectopic canine?
2%
What is overbite?
Vertical overlap of upper and lower incisors when viewed anteriorly (1/3 -1/2 coverage of lower incisors is normal)
How many features of an ideal static occlusion are there?
6
What are the 6 features of an ideal static occlusion?
- slightly proclined incisors, with the lower incisal edge in contact with the cingulum plateau of the maxillary teeth. Overjet and overbite 2-4 mm average.
- mesiobuccal cusp of upper permanent molar occludes with buccal groove of mandibular first molar
- long axis of teeth have a slight mesial angulation except lower incisors
- tight approximal contacts with no rotations
- flat occlusal plane or slight curve of Spee
- lingual inclination of crowns of canines to molars
What are the incisor classifications for BSI? (British Standards Institute)
Class I, Class II division 1, Class II division 2, Class III
Description of class I
The lower incisal edges occlude with / lie immediately below the cingulum plateau of the upper central incisors
Feature of both division 1 and 2 for class II incisor classification
lower incisor edges lie posterior to the cingulum plateau of the upper incisors
Feature of class II division 1
upper central incisors are proclined or of average inclination and the overjet is increased
Feature of class II division 2
upper central incisors are retroclined, the overjet is usually minimal
Description of class III incisor classification
the lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed
