Craniofacial growth, Developing dentition Flashcards
What’s the incidence of ankylosis in primary dentition?
7 – 14% in primary dentition
Most often affects lower Ds, followed by lower Es, upper Ds, upper Es
associated with agenesis of succadaneous tooth
multiple teeth seen as frequently as single
Does early correction of unilateral posterior crossbite eliminate morphological and positional asymmetries of the mandible?
yes
What # of weeks define the embryonic period?
The first 8 weeks of life.
What is the most favorable eruption sequence in max permanent dentition?
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612 regular
want 4s to come in (1st PM)
Then 5s (2nd PM)
Then 3s (canines)
Last 7s (so that 3s can take up leeway space)
Name 6 pharyngeal fistulae, cysts, and tumors associated with branchial arch malformation
- Thyroglossal duct cyst/ectopic thyroid (2nd pouch)
- Hemangiomas
- Thymic anomalies (e.g. DiGeorge)
- SCM tumor of infancy (sternocleidomastoid)
- Cervical teratoma/dermoid cyst and midline cervical cleft
- Lymphangioma/cystic hygroma
What is hypertrophy?
Increase in size of individual cells
What radiographs will best locate a supernumerary tooth?
2 PAs or occlusal films reviewed by the parallax rule
also: two PAs either using two projections taken at right angles to one another or the tube shift technique (buccal object rule or Clark’s rule) or by CBCT
What are the 6 stages of histodifferentiation?
- Initiation
- Proliferation
- Histodifferentiation
- Morphodifferentiation
- Apposition
- Mineralization and Maturation
What are the mechanisms of formation for intramembranous bone formation?
Periosteum and sutures, generally in areas of tension
no cartilagenous precursors
If a patient has crowded primary dentition, what % of the time will this patient have crowding in the permanent dentition?
100%
Moyer’s Analysis
Measures the M-D width of the mandibular incisors
Maxillary tooth predicted by mandibular teeth
Tanaka and Johnson also uses m-d width of lower incisor: Y = A + B (X) where
Y is sum of m-d widths of unerupted canines & PMs
X is sum of m-d widths of lower incisors
A and B are constants
Y = 11 + 0.5X for maxillary arch Y = 10.5 + 0.5X for mandibular arch
SNB average?
80˚
>80 then prog
<80 then retro
What is a low birth weight?
2,500 g at birth (5.5 lbs)
Where are most supernumerary teeth located?
Maxilla – 80-90%, ½ of that in the anterior area
Most common site – mesiodens
Second most common – paramolar (max. molar)
25% of mesiodens erupt spontaneously
Calcification of the permanent teeth
Will a permanent molar w/ part of its occlusal surface clinically visible and part under the distal of the second primary molar “jump” and self-correct?
NO
This is the impacted type, not the self-correcting type.
After the age of 7, definitive tx is indicated to manage and/or avoid early loss of the primary second molar and space loss
What is considered a full termbirth?
37-41 wks of completed gestation
T/F The majority of pts have Class I malocclusion.
T. 53%
Class II – 32%
Class III – 14 %
Open bite 5%
deep bite 10%
severe overjet >6mm 15%
29% have malocclusion where tx is highly desirable or mandatory (6.5 mill)
What arch has the stapes, styloid process, and stylohyoid ligament?
2 – Hyoid arch.
Also has lesser cornu/upper portion of body of hyoid, posterior digastric and muscles of facial expression
CN 7
What do the mandibular processes merge to create?
Lower lip and mandible
Systemic conditions implicated in delayed primary exfoliation and permanent eruption
- Vit D resistant rickets
- Endocrine disorders
- CP
- Celiac
- Prematurity/ low birth weight
- diabetes
- Genetic disorders (there are 26! Including OI, Cleidocr dyspl, ED, Chondroectod D, Albright’s, Gorlin, MPS, Gardner, Down, Apert, Achondroplasia, Cherubism and more)
What arch develops into muscles of mastication?
1st arch, also mylohyoid, anterior digastric, tensor palatini, tensor tympani
CN5 – Trigeminal nerve
What are some rules of thumb for timing of primary tooth loss affecting successor eruption?
Loss of 1˚ tth before age 5 => delays premolar
Loss of 1˚ tth after age 8 => accelerates premolar
Loss prior to completion of crown of successor → delays
Loss after crown completion → accelerates eruption
Which branchial arch has the most frequent anomalies?
2nd (95%)
1st arch only has 1% of all branchial anomalies
T/F:
Baume Type I is non-spaced dentition.
False
Baume Type I – generalized spacing of primary dentition (2/3)
Baume Type II – non-spaced (1/3)
Bilateral posterior crossbites in children (primary teeth)
Manifestation of a true skeletal constriction
Associated with dolicocephalic growth, open bite
Midlines are symmetric, no notable shift of mandible
2-3% of posterior crossbites
Treated with expansion
If a patient has no spacing in the primary dentition, what % of the time will this patient have crowding in the permanent dentition?
66%
What branchial arch is the major contributor to the facial structures?
1st arch mainly
some contribution from the 2nd
Ectopic eruption of permanent molars occurs in up to ___% of the population
3%
new guideline
more common in children with cleft lip and palate (25% of kids with CL/P)
Interference with cranial vault growth leads to ___________
Craniosynostosis
“copper-beaten skull”
e.g. Apert’s and Crouzon’s syndromes
What 3 ways do you make up for incisor liability?
- Intercanine width development
- Facial placement of lower anteriors
- primary spacing
If a pt has 3-6mm spacing in the primary dentition, what % of the time will the pt have crowding?
20%
Space regaining appliances
Fixed: active holding arches, pendulum appliances, Jones jig
Removable: Hawley appliance with springs, lip bumper, and headgear
What is development?
Increase in complexity
1st branchial pouch anomalies
Atretic eustachian tube → recurrent OM
eustachian tube diverticuli
absence of tympanic cavity, mastoid antrum
perforated tympanic membrane
bifid tongue
If you cannot palpate the canine bulge and there is radiographic overlapping of the permanent canine with the formed root of the lateral during mixed dentition, what should you do?
EXT the primary canine
Functional Matrix theory
- Functional demands of the craniofacial complex controls growth
- influence of “capsular matrices”
- Moss and Salentijn
- says that bones don’t grow but are grown: soft tissue grows – bone and cartilage respond
What is the precursor for the mandible?
Meckel cartilage
1st arch also has malleus, incus, sphenomandibular ligament
What is a normal nasolabial angle?
100-110˚
T/F
Undermining resorption happens with light, continuous forces on the pdl.
Heavy forces result in hyalinization.
F light forces result in “frontal resorption”
T. heavy forces result in “undermining resorption” and pdl become hyalinized because blood supply to the pdl becomes occluded
Are most children mesial, flush, or distal step?
Mesial 60%
flush 30%
distal 10%
(source??)
Handbook says
mesial 15% “incidence”
flush 75% “incidence”
distal no percentage given
What are the lateral lip and maxilla derived from?
Fusion of median nasal and maxillary processes
What percentage of primary supernumeraries have permanent supernumeraries?
1/3 of cases
What two points make Frankfurt Horizontal?
Po- Or
Porion-Orbitale
Servosystem theory
- Midface grows, maxillary arch follows, maxillary/mandibular relationship leads to muscular repositioning of the mandible, condylar cartilage responds
- Petrovic
2nd arch anomalies
Malformed auricle/microtia ossicular malformation (stapes, malleus, incus) muscular asymmetry of face hyoid malformation (lesser horn and upper body)
Early versus late mesial shift
Early mesial shift – closure of generalized posterior spacing with eruption of the 6s
(uses primate space)
Late mesial shift – mesial drift of the 6s into the leeway space
What are the 5 facial processes?
Median nasal + lateral nasal = median frontonasal Paired maxillary (x2) Paired mandibular (x2)
An example of a disorder of endochondral ossification is
a. cleidocranial dysplasia
b. achondroplasia
c. osteogenesis imperfecta
b. Achondroplasia
results from interference with cranial base growth
short limbs; atypical epiphyseal growth
defect in fibroblast growth factor receptor gene
a. Cleidocranial dysplasia (intramembranous bone)
c. osteogenesis imperfecta (both intra + endo)
What is the most favorable eruption sequence in the mandibular permanent dentition?
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Mandibular eruption is ahead of maxillary
What are risk factors of root resorption due to ortho tx?
open bite
root anatomy
high force levels
extraction therapy
amount of incisor retraction
? asthma
When do you do space maintenance in the primary anterior dentition?
Early loss of max. incisor in child with active digit habit
What % of canines ectopically erupt?
1.5 – 2%
F affected 3x more frequently than M
What is the most favorable eruption sequence in primary dentition?
ABDCE (for both max and mand)
Name three 1st branchial arch syndromes
Treacher Collins (mandibulofacial dysplasia)
Pierre Robin sequence
Hemifacial microsomia
When are facial structures “defined” during in utero development?
Between about 3 and 11 weeks
How long does it take for the root completion of a primary tooth? Permanent tooth?
Primary – 18 months post eruption
Permanent – 3 years post eruption
What type of bone formation is responsible for
- cranial vault
- cranial base
- maxilla
- mandible?
- Cranial vault – intramembranous
- Cranial base – endochondral
- Maxilla – intramembranous
- Mandible – intramembranous (body – appositional along posterior border of ramus and remodeling resorption along anterior border) AND endochondral (condyle)
What % of Class III malocclusion is heritable?
56%
OSAS may be associated with what dental findings?
Narrow maxilla, crossbite, low tongue position, vertical growth, and open bite
Hx associated with OSAS may include snoring, observed apnea, restless sleep, daytime neurobehavioral abnormalities or sleepiness, and bedwetting
Physical findings may include growth abnormalities, signs of nasal obstruction, adenoidal facies, and/or enlarged tonsils
Calcification of the primary teeth begin when?
4th fetal month
When does the greatest rate of increase in all dimensions of the dental arches occur?
Between birth and 3 yo.
Label These
Most forward point of chin – Pg
Lowest most point on the anterior margin of the foramen magnum in the midline – Ba
Intersection of the frontal bone and the nasofrontal suture in the midsagittal plane – Na
What is the incidence of permanent vs primary hypodontia?
Permanent: 3.5 – 6.5%
Primary 0.1 – 0.9%
T/F “Complex” malocclusion involves multiple teeth
F. It is a skeletal discrepancy
Compound is teeth
Simple – single tooth
complex + compound = dental and skeletal component
What % of pts have crowding in the permanent dentition if they have the following typed of primary dentition:
a. spacing ≥ 6 mm
b. spacing 3-6 mm
c. spacing < 3 mm
d. no spacing
e. crowding
Spacing ≥ 6mm ➔ no crowding
spacing 3-6mm ➔ 20% crowding
spacing < 3mm ➔50% crowding
no spacing ➔ 66% crowding
crowding ➔ 100% crowding
The mandibular primary lateral incisors calcify at how many weeks in-utero? 12 14 16 18
ANSWER: c. 16 weeks or 4 months (All primary teeth begin calcification at the 4th fetal month)
Where is the primate space?
ANB should be about what?
2˚
What is accretion?
Increase in non-cellular material
What % of impacted permanent incisors erupt normally after the mesiodens or othersupernumerary incisor is removed?
75%
if no eruption after 6-12 months and sufficient space exists, surgical exposure and orthodontic extrusion is needed
What are the cranial nerves?
O, o, o, to touch and feel very good velvet, such happiness
1. Olfactory
2. Optic
3. Oculomotor(eye mvmts)
4. Trochlear SO4
5. Trigeminal (Passing Through Zanzibar By Motor Car)
6. AbducensLR6
7. Facial (expression, tip of tongue taste)
8. Vestibulocochlear (formerly known as auriculotemporal)
9. Glossopharyngeal (taste last 2/3 tongue, others)
10. Vagus
11. Spinal Accessory(SCM, trap)
12. Hypoglossal (muscles of tongue)
some say marry money but my brother says big boobs matter more.
SO4, LR6
Compare and contrast endochondral versus intramembranous bone formation:
When does the embryonic period end? What follows it?
Embryonic ends wk 8
Fetal period begins wk 9 in utero and lasts until birth
- more growth rather than development
- body grows more rapidly
- ossification begins
How does the prevalence of max central diastema change with age?
Decreases with age:
44-97% 6 yo
33-46% 9 yo
7-20% 14 yo
The vagus nerve is derived from what pouch, and what muscles and skeletal components are also derived from that pouch?
4th Arch
Thyroid cartilage, laryngeal cartilage
Pharyngeal constrictors, laryngeal muscles
CNX Vagus
What % of mesiodens erupt spontaneously?
25%
a mesiodens that is conical in shape and not inverted has a better chance for eruption than one that is tubercular and inverted
T/F The face develops btwn 24thand 28th day.
T.
The 3rd arch has what skeletal, muscle, and nerve derivatives?
Lower part of body of hyoid (bone)
stylopharyngeus muscle (muscle)
glossopharyngeal nerve CN9 (nerve)
Describe the ideal primary dentition occlusion
Flush terminal or mesial step
class I canines
generalized spacing including primate spaces
2 mm overjet
2 mm overbite (30%)
What are the morphologic developmental stages of the tooth?
Lamina
Bud : prolif, morpho
Cap : prolif, histo, morpho
Bell : prolif, histo, morpho
Advanced bell
Hertwig’s Epithelial root sheath
Enamel and Dentin : apposition
What % of incisors erupt ectopically or are impacted from supernumerary teeth?
About 2%
Incisors can also have altered eruption due to pulp necrosis (following trauma or caries) or pulpal tx of the primary incisor
When you extract the primary canine, what % of permanent canines erupt that were previously impacted/off the track
75%
Pharyngeal arch structure
What is the frequency of hypodontia?
1.5 – 10% excluding 3rd molars
Handbook: 4%, no gender differences
- 3rd molars most common (20%)
- mandibular 2nd premolar (3.4%)
- max lateral incisor (2.2%)
- max 2nd premolar (0.85%)
<1% primary (max incisors & 1st molars)
Correlate the arches 1-4 with the cranial nerves:
trigeminal, glossopharyngeal, vagus, facial
- Trigeminal
- Facial
- Glossopharyngeal
- Vagus
Name a common 2nd cleft anomaly
Branchial cleft cyst
- congenital epithelial cyst
- 90% arise from 2nd branchial cleft
- M = F
- cysts twice as common as fistulas
- Tx: surgical excision
Can poor nasal respiration increase facial height and cause anterior open bite?
Yes
also increased OJ and narrow palate
but not the sole or even major cause of these conditions
Which teeth are most commonly affected by microdontia?
- Laterals
- 2nd premolars
- 3rd molars
most to least
Peak mandibular growth occurs between which two stages of Cervical Vertebral Maturation?
When should you treat a strong maxillary frenum?
- Attachment exerts a traumatic force on the gingiva causing the papilla to blanch
- Attachment causes a diastema to remain after the eruption of the permanent canines
Bifid uvula is an example of cleft palate
Yes. Can range from submucous to complete, palatal muscle diastasis, notch in posterior surface of hard palate
Ideal time to ext the mesiodens
Adjacent incisors have at least 2/3 root development will present less risk to the developing teeth but still allow for spontaneous eruption of the incisors
Which headgear tends to open the bite and extrudes molars?
Cervical pull headgear
HPHG minimizes bite opening effect
What is the incidence of hyperdontia?
0.5 – 2%
‘as high as 3%’ in oral surgery guideline
5x more common in the permanent dentition
Males affected 2x more than females
10x more common in maxillary arch versus mandibular
What are average values for SNA, SNB, ANB, and GoGn to SN
SNA – 82
SNB – 80
ANB – 2
GoGn to SN (mandibular plane) – 32
OP to SN – 14
What is growth?
Increase in size
2nd pouch anomalies
Thyroglossal duct cyst
failure of ablation of thyroglossal duct
anywhere from base of tongue to upper mediastinum
cystic lesion just below hyoid in midline that moves with deglutination and tongue protrusion
Lingual thyroid
failure of migration of thyroid → atopic
90% of cases at the base of tongue (ectopic thyroid tissue)
4:1 female: male
usually not noted until teen or young adult
asymptomatic usu; dysphagia, airway compromise
reddish mass at base of tongue
70% lack normal positioned thyroid tissue (only thyroid)
1/3 have hypothyroidism (edema of face and tongue, delayed eruption of teeth)
By what week are the palatal shelves usually fused?
A. 10 wks
b. 11 wks
c. 12 wks
c. 11 wks.
Secondary palate zips closed from incisive foramen posteriorly
Primary palate zips from posterior to anterior.
If canine impaction diagnosed at a later age (11 to 16), if the canine is not horizontal, what % of the time will the permanent canine erupt if you extract the primary canine?
75%
Extraction of the first primary molar also has been reported to allow eruption of the first bicuspids and to assist eruption of the canine
What is average SNA?
82˚
bigger SNA means maxillary prognathism
smaller SNA means maxillary retrognathism
What embryonic structures give rise to the palate?
Median nasal process → primary palate
Maxillary processes → palatal shelves (2o palate)
these structures fuse anteriorly and posteriorly from the area of the incisive foramen
What % of ectopically erupting permanent molars self-correct?
66%
by age 7
(22% for CLP)
What is incisor liability (quantitatively)?
Maxilla: 7.6 mm
Mandible 6.0 mm (handbook – 5mm)
Difference in width between the permanent incisors and primary incisors
How much is Leeway space and what does it mean?
Size difference between primary molars & permanent premolars
Maxillary arch has about 1.5 mm per side
Since A,J 1.5 mm > 4, 13
Mandibular arch has about 2.5 mm per side
Since K,T 2mm > 20, 29
L,S 0.5 mm > 21, 28
Handbook says 0.9 mm per quad for upper
1.7 mm per quad for lower
Does the mandibular intermolar width and arch length increase or decrease with age?
Both decrease
Pharyngeal arch derivatives
If the resting tongue position is normal, does a tongue thrust have clinical significance?
No, only if the resting position is forward
Then incisor displacement is likely
What structures are derived from the median nasal process?
Philtrum, tip of nose, columella, primary palate (premaxilla)
What is the hyperplasia?
Increase in # cells
What process are the palatal shelves part of?
Maxillary process. Union is through fusion.
What is the prevalence of microdontia?
1 – 8%
Which gender has more mesiodens occurrence?
Males
