Craniofacial and Tooth biology Theme 1 Flashcards
What is mesial drift ?
roots are usually diverted distally
this is due to crowns moving mesially during development
What is the palatal cingulum ?
convex tubercle on the cervical third of the anatomical crown
What are the features of an upper central incisor ?
broadest incisor mesial angle is 90 distal angle is more rounded short fat rounded triangualr root palatal fossa
What are the features of the upper lateral incisor ?
smaller
mesial angle is more acute
distal angle is more rounded
conical flattened root
What are the features of the lower central incisor ?
smallest tooth symmetrical crown mesial and distal angle are both 90 crown displaced lingually DLG more distinct
What are the features of the lower lateral incisors ?
wider and asymmetrical fan shaped
flattened root with DLG
mesial angle almost 90 and distal angle is acute
distal side emerges at a greater angle from the long axis of the tooth than the mesial side
What are the features of the upper canines ?
longest root
mesial surface is almost a straight line
distal surface meets the root at an obtuse angle
distal slope is greater than mesial slope
palatal ridge passes from the tip of the cusp to the palatal cingulum and is separated from the marginal ridges by the mesiopalatal and the distopalatal fossa
What are the features of the lower canines ?
the enamel of labial surface extends further than the lingual surface
difference in the slopes less pronounced
How many cusps do premolars have ?
2 cusps - 1 buccal and 1 lingual
What separates the cusps in premolars ?
the central fissure which runs from mesial to distal
What are the features of upperr premolars ?
they are inclined lingually resulting in a prominet buccal cusp
round and circular
What are the features of upper premolars ?
they are more angular and wider buccolingually
How many roots do premolars have ?
they all have 1 except upper first premolars
What are the features of the upper first premolars ?
2 roots
prominet buccal cusp
buccal ridge
mesial slope of the buccal cusp is greater than the dista; slope
central fissure can extend as the canine groove which can turn into a depression between the roots
What are the feature of the upper second premolar ?
1 root which is deeply grooved on both sides
no canine groove
buccal and palatal cusps are more equivalent in size
mesial slope of the buccal cusp is smaller than the distal slope
What are the features of the lower first premolars ?
circular
single conical root
buccal cusp is larger
might gave disto-lingual accessory cusp
What are the features of upper molars ?
they have 3 roots- 2 buccal and 1 palatal - palatal is the thickest
rhomboid shape
3-4 cusps that are aymmetrical
What are the features of the upper first molar ?
rhomoid shape 4 cusps- 2 buccal and 2 palatal. Buccal are separated by buccal fissure H shaped central fissure cusp of carabelli 3 roots- 2 buccal and 1 palatal
What are the features of the upper second molars ?
there are 3 types
type 1- similar to upper first molar, has 4 cusps but is reduced in size
type 2- heart shaped - 3 cusps
type 3- oval crown with 3 cusps
What are the features of the upper 3rd molar ?
most variable tooth
often resembles the type 2 heart shaped upper 7
roots may be reduced in size and fused
What are the features of the lower molars ?
they have a rectangular shape
they have 4-5 cusps
symmetrical cusps
2 roots
What are the features of the lower first molar ?
5 cusps- 3 buccal and 2 lingual
2 roots - 1 mesial and distal
What are the features of the lower second molar ?
4 cusps
rectangular shaped
2 roots
cross shaped occlusal fissure
What are the features of the lower third molar ?
irregular branching occlusal pattern
4 cusps
2 roots are partly fused
1 root may be subdivided
What are the general features of primary teeth ?
smaller in size more bulbous less minerlaised- so whiter enamel enamel is thinner so more likely to wear away and be effected by caries labial cingulum near the cervical line
Why do primary teeth show less interproximal caries ?
they are less crowded
What significant about primary pulp horns ?
they are higher therefore can be exposed more
closer to the EDJ
How is the transverse diameter of the primary anterior teeth ?
transverse diameter is greater than the length
What are the characteristics of the primary central incisors (upper) ?
low rounded labial cingulum near the cervical line
transverse diameter=vertical diameter
shallow palatal fossa
mesial angle is 90 and distal angle is rounded
conical root is compressed in the labio-palatal direction
What are the characteristics of the upper lateral incisors ?
distal angle is more rounded and mesial angle is now acute
labial and palatal cingulum (low)
What are the characteristics of the primary lower central incisors ?
symmetrical
low labial cingulum
mesial and distal angle is 90
What are the characteristics of the primary lower lateral incisors ?
asymmetrical
wider
low labial cingulum
rounded root
What are the characteristics of upper primary canines ?
symmetrical triangular low labial cingulum 2 shallow palatal fossae mesial slope > distal slope long root
What are the characteristics of the lower primary canines ?
asymmetrical
slender
distal slope is greater than the medial slope
labial cingulum
What is significant about primary molar roots ?
they are more divergent
How many cusps and roots do upper Ds have ?
4 and 3
Which side of the upper D is bigger ?
buccal
What is the shape of the upper D ?
irregular quadrilateral
What is a feature of the upper D ?
buccal cingulum extends mesially to make a molar tubercle
How many roots and cusps do the lower D have ?
2 roots
2 cusps
Which cusps in the lower D are bigger ?
buccal and the mesial
What is the transverse ridge in the lower D ?
connects the 2 mesial cusps together
splits the central fissure into mesial and distal pits
What are the characteristics of the upper D ?
low buccal cingulum
no molar tubercle
similar to upper 6 with 5 cusps but whiter, smaller and more divergent roots
carabellis tubercle
3 roots- distobuccal and palatal may be fused
What are the characteristics of the lower Es ?
similar to lower 6 5 cusps 2 roots - mesial and distal mesial root is grooved buccal cingulum more distinct than lower 6
What does postnatal jaw growth require ?
a second set of teeth
How are the adult dentition displaced >
anteriorly and laterally
Do mandibular or maxillary teeth erupt first ?
mandibular
Do anterior or posterior teeth erupt first ?
anterior
Do teeth erupt mesially or distally first ?
mesially to distally
Which teeth erupt in the first phase of adult growth ?
6 1 2
Which teeth erupt in the second phase of adult growth ?
3 4 5 7
Which teeth erupt in the third phase of adult growth ?
8
When do primary first molars erupt ?
1.5 years
When do primary second molars erupt ?
2.5 years
When do permanent first molars erupt ?
6 years
When do permanent second molars erupt ?
12 years
When to permanent third moalrs erupt ?
18 years
What are the stages in tooth eruption ?
calcification
crown completion
root bifurcation
root completion
What is calcification ?
the first radiographic appearance of the crown
Radiographically how is crown calcification visible ?
cusps and the lamina dura
When do primary teeth calcify?
4-6 months in utero
When do 6s calcify ?
just before birth
When do permanent incisors calcify ?
3-5 months
When do permanent canines calcify ?
6-9 months
When do 4s calcify ?
1.85-2.65 years
When do 7s calcify ?
by 3 years
When do 8s calcify ?
by 8 years
When is crown completion ?
halfway between calcification and eruption
How is crown completion visible ?
white dense enamel
dentine underneath visible - found downwards
What is root bifurcation ?
the first calcification of the bifurcation of the lower permanent molar roots
When do the roots of the lower 6s calcify ?
4.5 years
When do the roots of the lower 7s calcify ?
8.5 years
How can we see radiographically the presence of root bifurcation ?
crescent shape
What are the 2 steps in root completion ?
root lengthening
root completion
When do the primary teeth complete their roots ?
1-1.5 years after eruption
When do the permanent teeth complete their roots ?
2-3 years after eruption
What happens in root lengthening ?
tooth has erupted and the pulp horns are fully formed
apical end of the root is still funnel shaped
What happens when the root is almost complete ?
root canal is now shut and has an apical foramen
What are the basic steps to determining age from a DPT ?
find the lower 6
find the lower 7
look for evidence of calcification of 8
degree of incisor eruption
If the lower 6 crown is complete what age can be estimated ?
more than 3 years
What age can be estimated if the roots of the lower 6 are calcified ?
4.5 years
If there is no lower 6 what age can be estimated ?
more than 6 years
If the roots of the lower 6 arent complete what age can be estimated ?
less than 9 years
If the crown of the lower 7 is complete what age can be estimated ?
more than 6.5 years
If the lower 7 root is calcified what age can be estimated ?
8.5 years
If the lower 7 is unerupted what age can be estimated ?
less than 12 years
If the root is incomplete for the lower 7 what age can be estimated ?
around 15 years
When does the lower 8 calcify ?
8-10 years
What is tooth eruption ?
the process of tooth movement form within the alveolar bone upwards to reach functional occlusion``
What are the 2 types of emergence ?
through the alveolar bone and then through the gingiva
What is the definition of clinical emergence ?
tooth is visible in the oral cavity
What happens to the PDL in emergence ?
bone is constantly remodelled to let teeth through and the PDL makes connections with tooth and bone
What must happen before permanent teeth erupt ?
resorption of primary roots and resorption of the alveolar bone
What is exfoliation ?
the shedding of primary teeth
What is the mixed dentition ?
begins at 6 with the appearance of the 1st permanent molars and ends at 11 with the appearance of the permanenet premolars
How long does it take from clinical emergence to full occlusion for incisors ?
3 months
How long does it take for clinical emergence to full occlusion for molars ?
6 months
How long does it take from the onset of resorption to exfoliation for anterior teeth ?
1 year
How long does it take from the onset of resorption to exfoliation of molar teeth ?
1.5 years
Are distal or mesial roots resorbed first ?
distal
How do permanent primary teeth move prior to eruption ?
they move behind the roots of the primary anterior teeth
How do the developing premolars move prior to eruption ?
the premolars move between the roots of the priamary molars
What is the pattern of root resorption in primary incisors and canines ?
the roots are more resorbed on the lingual side than the labial side
pulp is still intact
What is the pattern of root resorption in primary molars ?
in an occlusal direction
pulp chamber is eroded
Why might there be an early loss of primary teeth ?
caries/extraction/ trauma
What are the consequences of an early loss of primary teeth ?
symmetrical and space problems
accelerated eruption of permanent teeth
Why might there be prolonged retention of primary teeth ?
failure of the permanent teeth to resorb the primary roots
ectopic position of successor
variation in exfoliation age
Why might there be delayed eruption ?
congenital, systemic, local
ectopic teeth can form cyst and prevent eruption of the successor
Why might there be impacted teeth ?
lack of space
selection pressures mean that jaws are now smaller and there is no room for 8s. - reducing the space for eruption
Why might shedding of primary teeth be delayed ?
successor teeth are missing
Why does shedding eventually occur ?
nanci states that large masticatory muscles put pressure on primary teeh, damaging the PDL and initiating tooth resorption
What are supernumerary teeth ?
more common in permanent teeth
isolated or part of syndrome
prevent eruption of other teeth
What is dilaceration ?
abnormal angulation between crown and root due to trauma
can cause successors to fail to erupt
What can trauma lead to ?
cessation of root growth
root is stunted and doesnt protect the crown
What is cephalometry ?
study of head images like lateral radiographs to assess the facial and dentoskeletal relationships
used for orthodontics
What is a class I skeletal relationship ?
the lower dental base is centrally related to the upper dental base- this gives a flattened profile
What is a class II skeletal relationship ?
the lower dental base is retruded relative to the upper
gives a smaller mandible and a larger maxilla
What is a class III skeletal relationship ?
lower dental base is retruded
mandible sticks out
What is a class I incisor relationship ?
the lower incisor edges occlude with or lie below the palatal cingulum of the upper incisors
What is a class I div I relationship ?
the lower incisor edges lie posterior to the palatal cingulum of the upper incisors
overjet is increased
What is a class I div II relationship ?
lower incisor edges lie posterior to the palatal cingulum of the upper incisors- but the upper incisors are retroclined so the overjet is reduced
What is class III incisor relationship ?
lower incisor edges lie anterior to the palatal cingulum of the upper incisors
What is a class I molar relationship ?
mesiobuccal cusp of the upper 6 lies in the buccal groove of the lower 6
What is a class II molar relationship ?
upper 6 is one whole tooth mesial to the class I position the distobuccal groove of the upper 6 lie in the buccal groove of the lower 6
What is a class III relationship ?
upper 6 is whole tooth distal to the class I position mesiobuccal cusp of the upper 6 is behind the distobuccal cusp of the lower 6
What is the intercuspal position ?
centric occlusion that occurs as a result of the position of the jaws so that the maxillary and mandibular teeth are in maximum intercuspation
What is dynamic occlusion ?
relationships of the teeth that occur when the mandible is moving.
movements can be lateral or protrusive
Which teeth are likely to be guider teeth ?
incisors and canines
What is the rest position ?
at rest the teeth are slightly separated by a couple of milimetres
in relaxed position the teeth arent in contact
What is a normal crossbite ?
normally the upper arch is bigger
this means the palatal cusps of the upper teeth fit into the central fossae of the lower teeth
the buccal cusps of the lower teeth fit into the central fossae of the upper teeth
What is a buccal crossbite ?
lower jaw is wider
buccal cusps of the upper teeth fit into the central fossae of the lower teeth
lingual cusps of the lower teeth fit into the central fossa of the upper teeth
What is a scissorbite ?
the upper jaw is signnficantly wider than the lower jaw so teeth dont contact.
What is the functional cusp ?
the cusp that bites into the central fossa of the opposing posterior tooth. usually the palatal cusps of uppers and buccal cusps of the lowers
What is the working side ?
when you move the jaw to chew food- the side you move it to is called the working side
What are the guidance teeth ?
when the lower jaw is slided across to the working side
the teeth that make contact are the guidance teeth
When do primary incisors erupt ?
6-9 months
When does the first primary molars erupt ?
1-1.5 years
When does the 2nd primary molars erupt ?
1.75-2 years
When do the lower central incisors erupt ?
6-7 years
When do the lower lateral incisors erupt ?
7-8 years
When do the upper central incisors erupt ?
7-8 years
When do the upper lateral incisors erupt ?
7.5-8.5 years
When do the upper permanent canines erupt ?
10-12 years
When do the lower permanent canines erupt ?
9.25-10.5 years
When do the upper and lower first premolars erupt ?
10-11 years
When do the upper and lower 2nd premolars erupt ?
10.5-12 years
When does the 1st permanent molar erupt ?
6 years
When does the lower 7 erupt ?
11-12 years
When do the upper 7s erupt ?
12-13 years
When do the 8s erupt ?
17-21 years
When do the 8s erupt ?
17-21 years
When do the primary teeth erupt ?
4-6 months in utero
When do the permanent incisors calcify ?
3-5 months
When do the upper permanent canines calcify ?
9 months
When do the lower permanent canines calcify ?
6.5 months
When do the permanent premolars erupt ?
1.85-2.65 years
When does the 6 calcify ?
just before birth
When do the 7s calcify ?
3 years
When do the lower 8s calcify ?
8-9 years
When do primary teeth complete their roots ?
1-1/5 years after eruption
When do permanent incisros ,canines and premolars complete their roots ?
2 years after eruption
When do the lower 6s complete their roots ?
9 years
When do the 7s complete their roots ?
15 years
When do the 8s complete their roots ?
more than 3 years after eruption
When does root bifurcation happen ?
before eruption
When does the lower 6 roots bifurcate ?
4.5 years
When do the lower 7s bifurcate ?
8.5 years
When do the upper 2s complete their crowns ?
4.5 years
When do the 6s complete their crowns ?
3 years
