Primary Tooth Morphology Flashcards
What are early problems babies can have prior to teeth eruption? (4 points)
- Gingival Cysts (Epstein’s P e arls/Bohns nodules)
- Congenital Epulis
- Natal or neonatal teeth
- Eruption cysts
How would you treat gingival cysts?
- Do not need to do anything to them - they will resolve
What are Bohn’s nodules?
- Tiny multiple cysts in new-borns. They are found at the junction of the hard and soft palates and along buccal and lingual parts of the dental ridges and are derived from epithelial remnants of mucous gland tissue
What are Epstein pearls?
Small white or yellow cystic vesicles often seen in the medial palatal raphe of the mouth of newborn infants. They are typically seen on the roof of the mouth and are filled with fluid. They are caused by entrapped epithelium during the development of the palate
What is a congenital epulis?
- A proliferation of cells on the jaw at birth. This is more commonly found in female babies. The cause of this type of epulis is unknown
What is a natal tooth?
- Tooth there when the baby is born
What is a neonatal tooth?
- Tooth erupted just after the baby if born
Are natal/neonatal teeth extra teeth?
- No, they have just been in an ectopic position
What is an ectopic position?
- An abnormal position/location
What is an eruption cyst?
Where tooth is erupting and blood has gotten into the follicle space
- Don’t need to do anything about them - they will resolve themselves
What number would you use for an upper right deciduous tooth?
5
What number would you use for an upper left deciduous tooth?
6
What number would you use for an lower right deciduous tooth?
8
What number would you use for a lower left deciduous tooth?
7
In which week of intra-uterine life do teeth start to form?
- Week 5
In which week of intra-uterine life does hard tissue formation start and can be detected on subsequent ultrasound scans?
- Week 13
At how many weeks I.U.L does the hard tissue formation begin for the deciduous maxillary central incisor?
13-16
At how many weeks I.U.L does the hard tissue formation begin for the deciduous mandibular central incisor?
13-16 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous maxillary lateral incisor?
14.7-16.5 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous mandibular lateral incisor?
14.7-16.5 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous maxillary canine?
15-18 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous mandibular canine?
16-18 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous maxillary first molar?
14.5-17 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous mandibular first molar?
14.5-17 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous maxillary second molar?
16-23.5 weeks
At how many weeks I.U.L does the hard tissue formation begin for the deciduous mandibular second molar?
- 17-19.5 weeks
What can systemic disturbances during calcification lead to?
- Can lead to defects in the enamel which was forming at the time
- Defects in the primary dentition (which are not hereditary) are most likely the result of a difficult pregnancy for the mother or complications at birth
How much of the crown of central incisors are present at birth?
1/2
How much of the crown of lateral incisors are present at birth?
1/3
How much of the crown of primary canines are present at birth?
- Just the tip
How much of the crown of first primary molars are present at birth?
1/2
How much of the crown of second primary molars are present at birth?
1/3
How much of the crown of first permanent molars are present at birth?
- The tip of the cusps
The exact biology of tooth eruption has not been explained by any one theory. It is likely that it is a multifactorial process. What needs to happen for tooth eruption to occur?
- A force must be generated to propel the tooth through the bone and gingival tissue. In the case of the permanent dentition the primary tooth root must also be removed in some cases
What are the possible theories behind tooth eruption? (4 points)
- Cellular proliferation at the apex of the tooth
- Localised change in blood pressure/hydrostatic pressure
- Metabolic pressure within the PDL
- Resorption of the overlying hard tissue and apoptosis
How does resorption of the overlying hard tissue occur?
- Due to enzymes in the dental follicle
- Dental follicle best seen on radiograph as a dark halo round the unerupted tooth
Is remodelling of bone or primary tooth tissue essential to the process of tooth eruption?
- Yes
- BUT animal studies have shown that the resorption process can be uncoupled from the eruption process i.e. it is not necessary for the tooth to erupt to cause resorption of the bone
The follicle has been shown to play an essential role in active tooth eruption. What is the follicle activated to initiate?
- Initiates osteoclastic activity in the alveolar bone a head of the tooth and clear a path for tooth eruption
- Once the crestal bone has been beached (and just have soft tissues ahead) the follicle is likely to play a lesser role
Theories regarding which 3 things have been discounted as major factors for tooth eruption?
- Root elongation
- Periodontal ligament
- Local changes in vascular pressure
Eruption occurs gradually. When does it stop?
- Stops when the tooth comes into contact with something - usually the tooth on the opposing arch
- Continues throughout life to compensate for vertical growth of the jaws and tooth wear
What is the age and eruption sequence of the primary dentition?
L central = 6 months
U central = 7 months
L lateral = 7 months
U lateral = 9 months
L 1st molar = 12 months
U 1st molar = 14 months
L canine = 16 months
U canine = 18 months
L 2nd molar = 20 months
U 2nd molar = 24 months
When does the deciduous lower central start to erupt?
6 months
When does the deciduous upper central start to erupt?
7 months
When does the deciduous lower lateral start to erupt?
7 months
When does the deciduous upper lateral start to erupt?
9 months
When does the deciduous lower 1st molar start to erupt?
12 months
When does the deciduous upper 1st molar start to erupt?
14 months
When does the deciduous lower canine start to erupt?
16 months
When does the deciduous upper canine start to erupt?
18 months
When does the deciduous lower 2nd molar start to erupt?
20 months
When does the deciduous upper 2nd molar start to erupt?
24 months
As a general rule the lower teeth erupt before the uppers. What is the exception to this rule?
- Exception of lateral incisors
What is the general sequence of eruption of deciduous teeth?
Central incisor -> lateral incisor -> first primary molar -> canine -> second primary molar
What are the average eruption dates for the deci duous lateral incisors?
7-16 months
What are the average eruption dates for deciduous 1st molars?
13-19 months
What are the average eruption dates for deciduous canines?
16-22 months
What are the average eruption dates for deciduous 2nd molars?
15-33 months
How long does it usually take between teeth of the same series and their contra lateral teeth to erupt?
- Normally erupt within 3 moths of each other
At what age on average should the primary dentition be complete?
By 2.5-3 years of age
Is it normal for children to still have no teeth at all by the age of one?
yes, we wold not do any investigations at this point, would just be waiting
What is the difference between primary and secondary incisors?
- Primary incisors are smaller in both their crown and root proportions
What is the difference between primary and secondary molars?
- Primary molars are wider mesiodistally than the permanent premolars which take their place
- Primary molar crowns are more bulbous
In terms of colour what is different between the primary and secondary teeth?
- Primary teeth are usually whiter in colour
What is a prominent anatomical feature of the upper primary first molars?
Prominent mesiobuccal tubercle
What is a prominent anatomical feature of the lower primary first molars?
- Prominent tubercle mesiobuccal
the succeeding premolar doesn’t have tubercles
What is a prominent anatomical feature of the primary upper second molars?
- Transverse ridge
- Runs across secondary primary molar
What is a prominent anatomical feature of the lower primary second molars?
- Three buccal cusps (like first permanent molar)
What are the differences between primary and permanent teeth roots? (2 points)
- The roots of primary teeth tend to be narrower when compared with their primary counterparts
- The roots of the primary molars are longer and more slender than the roots of the permanent molars. These roots tend also to flare apically to allow room in between for the developing permanent tooth crowns
What are the differences between the pulp of primary and permanent teeth?
- The pulp chambers of the primary teeth are relatively large in proportion to the crowns that surround them
- The pulp horns of primary teeth extend high occlusally, placing them closer to the enamel than the pulp horns of permanent teeth - hence pulpal exposure on cavity prep is more likely
What is the difference between the root canals of primary and permanent teeth?
- Primary teeth - Tend to be ribbon shaped with multiple interconnecting and accessory canals (clinically impossible to clean properly)
What is the difference in the coronal dentine in primary teeth compared to permanent teeth?
- The thickness of the coronal dentine is much thinner than in permanent teeth
What is the difference in the enamel of primary teeth compared to permanent teeth?
- The enamel of the primary teeth is relatively thin and has a constant depth - so doesn’t vary in depth as with the permanent dentition
What is desired in the primary dentition is there is t o be no crowding in the permanent dentition?
- Some anterior spacing in the primary dentition
What is meant by the term ‘anthropoid/primate’ spacing?
- Spacing mesial to the upper deciduous canine
- Spacing distal to the lower deciduous canine
What is meant by ‘leeway space’ in the deciduous dentition?
- Extra mesio-distal space occupied by the primary molars which are wider than the premolars which will replace them
What does the leeway space in the primary dentition equate to?
- Usually equates to 1.5mm per side on the upper arch and 2.5mm per side on the lower arch
Facial growth can affect someone’s occlusion. In what direction dies the face grow?
- Downward and forward growth of the facial portion of the skull
When does the mixed dentition stage begin?
- From the time the first permanent tooth erupts, until the exfol iation of the last primary tooth
- This is usually the time between 6 and 11 yeahrs of age bt there are normal variations
- At least 5 years of mixed dentition to seal with
What is the eruption sequence of permanent teeth in the upper arch?
- 1st permanent molars and then front to back EXCEPT canines
- 6, 1, 2, 4, 5, 3, 7, 8
What is the eruption sequence on the permanent dentition in the lower arch?
- 1st permanent molars and then front to back
- 6, 1, 2, 3, 4, 5, 7, 8
- Again as a general rule lower teeth tend to erupt before upper teeth with the exception of second premolars
Do permanent teeth on the upper or lower arch erupt first?
- As a general rule lower teeth tend to erupt before upper teeth with the exception of second premolars
At what age does the permanent upper central usually erupt?
7 y/o
At what age does the permanent upper lateral usually erupt?
8 y/o
At what age does the permanent upper canine usually erupt?
11 y/o
At what age does the permanent upper first premolar usually erupt?
10 y/o
At what age does the permanent upper second premolar usually erupt?
10 y/o
At what age does the permanent upper first molar usually erupt?
6 y/o
At what age does the permanent upper second molar usually erupt?
12 y/o
At what age does the permanent lower central usually erupt?
6 y/o
At what age does the permanent lower lateral usually erupt?
7 y/o
At what age does the permanent canine usually erupt?
9 y/o
At what age does the permanent lower first premolar usually erupt?
10 y/o
At what age does the permanent lower second premolar usually erupt?
10 y/o
At what age does the permanent lower first molar usually erupt?
6 y/o
At what age does the permanent lower second molar usually erupt?
12 y/o
What is the eruption path of the incisors and why can this be a problem?
- Permanent incisors develop palatal to the primary incisors
- Trauma risk to the permanent teeth if primary incisors are displaced towards the developing tooth
The ‘ugly duckling stage’ where there is transient spacing of the upper centrals is caused by what?
- May occur due to the close proximity of their roots to the erupting 2’s and 3’s.
- Would explain to a patient that it is a physiological phase and would not do anything about it until permanent canine comes through as space will change
How long does it take from the date of eruption for the root of primary dentition to be fully formed?
1.5 years on average
How long does it take from the date of eruption for the root of permanent dentition to be fully formed?
Around 3 years
