Clinical Development of the Dentition Flashcards
What is orthodontics?
Orthodontics is that branch of dentistry concerned with facial growth, with development of the dentition and occlusion, and with the diagnosis, interception and treatment of occlusal anomalies.
What are the stages of development (of the dentition)?
Newborn, primary (deciduous) dentition, mixed dentition, permanent dentition
Describe newborn “dentition”
Gum pads, upper rounded, lower U shaped
Anterior open bite
Often appear very skeletal class 2
Describe skeletal class I (antero/posterior relationship)
Mandible is 2-3mm posterior to the maxilla
Describe skeletal class II (antero-posterior relationship)
Mandible is retruded relative to the maxilla
Describe skeletal class III (antero-posterior relationship)
Mandible is protruded relative to the maxilla
What is a natal tooth
A tooth present at birth. Rare. Needs to be removed
What is cleft lip and palate?
Congenital defect that has a profound impact on patient’s dental development. Structures that form the upper lip and palate fail to fuse. Require a lot of treatment, early intervention carried out throughout stages of life. Surgery and orthodontics required.
When do primary teeth erupt?
6 months - 3 years
Which primary teeth erupt first?
Lowers erupt before uppers
a-b-c-d-e
How does the primary dentition differ from permanent dentition?
Incisors are more upright than permanent dentition
Spaced
Often marked wear towards the end
Why is it best to having spacing in primary dentition?
To prevent crowding when permanent dentition erupt
What percentage of cases will show crowding with no spacing in primary dentition?
66% crowding
What percentage of cases will show crowding with <3mm spacing?
50% crowding
What percentage of cases will show crowding with 3-6mm spacing?
20% crowding
What percentage of cases will show crowding with >6mm spacing?
No crowding
Describe mixed dentition
Mixture of primary and permanent teeth
Age 6-13 approx.
Incisors and first molars erupt at age 6-8.5
Canines, premolars and second molars erupt at 10-12.5
Which teeth generally erupt at age 6?
Upper and lower 6s
Lower 1s
Which teeth generally erupt at age 7?
Upper 1s
Lower 2s
Which teeth generally erupt at age 8?
Upper 2s
Which teeth generally erupt at age 11?
Lower 3s
Upper and lower 4s
Which teeth generally erupt at age 12?
Upper 3s
Upper and lower 5s
Upper and lower 7s
How are permanent incisors accommodated?
- Spacing of the deciduous dentition
- Increase in inter-canine width: 3.5mm in the maxilla, 3.0mm in the mandible
- Path of erupt is more proclined - bigger arc of circle - increase in AP arch
Which incisors erupt first?
Centrals before laterals
Lowers before uppers
What are supernumerary teeth?
Extra teeth that can block permanent teeth from erupting. Need to be removed
Where are supernumerary teeth most common?
In upper incisor region, can impeded eruption of permanent incisors
What leads to an increase in A-P arch length?
Proclined permanent incisors
Primary incisors are more upright
Define “microdontia”
Small permanent teeth - can build them up with composite, porcelain veneer, etc
Define “macrodontia”
Teeth that are too big. Can be difficult to reduce size without invading the pulp chamber. May need to extract tooth and replace with a prosthetic one
What is increased overjet?
Upper teeth sticking out a bit
Increases risk of trauma to the upper teeth
What is posterior/buccal cross bite?
Uppers and lowers not aligned in transverse axis
What is the “Leeway” space?
Difference in size between e, d, c and 3, 4, 5
Maxilla = 1.5mm
Mandible = 2.5mm
What is dental alveolar disproportion?
Difference in size of teeth and space available to accommodate them in the jaw
What is transposition?
Where 2 permanent teeth get swapped over. Usually involves the upper canine.
Why is the upper canine usually involved in transposition?
The upper canine takes longer to erupt as it develops high up. More scope for it to lose its way and get swapped over with another tooth germ on the way down.
What are the features of an ideal static occlusion?
- Incisors slightly proclined, with the lower incisal edge in contact with the cingulum plateau of the maxillary teeth. Overjet and overbite 2-4mm on average.
- The mesiobuccal cusp of the maxillary permanent molar occludes with the buccal groove of the mandibular first molar.
- Long axis of the teeth have a slight mesial inclination EXCEPT the lower incisors
- Tight approximal contacts with no rotations
- Flat occlusal plane or slight curve of Spee
- The crowns of the canines back to the molars have a lingual inclination
Describe Class I (incisor classification)
The lower incisor edges occlude with or lie immediately below the cingulum plateau of the upper central incisors
Describe Class II Div 1 (incisor classification)
The lower incisal edges lie posterior to the cingulum plateau of the upper incisors
The upper central incisors are proclined or of average inclination, the overjet is increased
Describe Class II Div 2 (incisor classification)
The lower incisal edges lie posterior to the cingulum plateau of the upper incisors
The upper central incisors are retroclined, the overjet is usually minimal but can be increased
Describe Class III
The lower incisal edges lie anterior to the cingulum plateau of the upper incisors
The overjet is reduced or reversed
Define overjet
Distance between the upper and lower incisors in the horizontal plane (normal overjet is 2-4mm)
Define overbite
Vertical overlap of the upper and lower incisors when viewed anteriorly
One third to one half coverage of the lower incisors is normal
Define crowding
When there is insufficient space to accommodate the teeth in perfect alignment
Define hypodontia
Congenital absence of one or more teeth
Define leeway space
Difference in mesio-distal diameter between c, d, e and 3, 4, 5
Define reverse overjet
The lower incisors lie anterior to the upper incisors
Define malocclusion
Variation from the ideal occlusion which has dental health and/or psychosocial implications for the individual
Define ideal occlusion
Anatomically perfect arrangement teeth
Define normal occlusion
Acceptable variation from the ideal occlusion
Define buccal cross bite
The buccal cusps of the lower premolars and/or molars occlude buccally to the buccal cusps of the upper premolars and/or molars
What are natal teeth?
A tooth which is present at birth or erupts soon after
Define transposition
The interchange in position between 2 teeth
