Orthodontics Flashcards
primary teeth molar relationships
- flush terminal plane
- mesial step
- distal step
- Angle’s Class III
- normal relationship of primary molars, the primary 2nd molars determines the AP position of the permanent 1st molars
- equiv to Angle Class I
- equiv to Angle Class II
- almost NEVER seen cause of normal pattern of craniofacial growth where mandible lags behind maxilla
most common initial relationship of primary molars is
edge to edge, flush terminal plane -> Class I
when erupting, permanent teeth move __ and _-
occlusally and buccaly
arch lengths
max
mand
max - 128
mand - 126
for permanent teeth
incidence of malocclusion in a homogenous or heterogenous population is higher?
higher in HETEROgenous
skeletal open bite (long face syndrome)
assoc. with mouth breathing
- condition is not self correcting and worsens with time
malocclusions more identifiable in kids ages __ to __
7-9 cause eruption of permanent incisors reveal arch length discrepancies
Steiner analysis
- SNA angle
- SNB angle
- ANB angle
- SNA - sella turcica to nasion, shows maxilla and cranial base.
> 82 = mx prognathic
< 82 = mx retrognathic - SNB - SN and NB
> 80 = md prognathic
< 80 = md retrognathic - ANB - difference btw SNA and SNB
> 4 = Class II skeletal
< 0 = Class III skeletal
Angle Class I (A)
MB cusp of mx first molar lines up with buccal groove of md first molar; max centrals overlap md centrals
- most COMMON (70%)
- most common cause is discrepancy btw tooth structure and amt of supporting bone length
- most prevalent characteristic is CROWDING from not enough arch length
when crowding is > __ mm in the mandible, ext are often required
4 mm
In Angle Class II, there are 2 divisions
big diff btw division I and II is in division II, mas laterals are tipped
labially and mesially
Class II, Division I
Class II, Division II
I - max central and laterals are in extreme labioversion (protruded) DEEP BITE
II - body of mandible and its dental arch are in a distal relationship to the maxilla, while molar & canine occlusion are same as Class II, D I.
Sunday bite
forward postural position of mandible adopted by ppl with Class II
Class II (B) canine relation
Class III (C) canine relation
B: mandibular canine’s distal surface is distal to max canine’s mesial surface. max canine is mesial to mand canine
C: mand canine’s distal surface is mesial to max canine’s mesial surface. max canine is distal to mand. canine
when distocclusion occurs on only one side of the arch, it’s called a __ of its division
subdivision
ex. Class II, Division I Subdivision
ectopic eruption
tooth erupts in wrong place
- most common in max 1st molars and mand incisors, more common in maxilla, assoc. with Class II
- in 2-6% of population
- ectopic of max 1st molar - brass wire
- ectopic of mand laterals can cause transposition of lateral incisor and canine
pseudo-class III
mandibular incisors forward of max incisors in centric, but pt can bring mandible back without strain
- FORWARD SHIFT of mandible during closure to avoid incisor interference
- tx by eliminating CO-CR discrepancy
bimaxillary dentoalveolar protrustion
when teeth protrude in both jaws - lip strain
crossbites are assoc. with
jaw size discrepancy, hereditary (genetics), reverse over-jet, scissor bite NOT tongue thrusting
- anatomical - smooth closure into centri
- functional - caused by thumb sucking
when should ortho tx start to correct xbite
asap
max expansion is the first step with PALATAL EXPANDER
scissor bite (bilateral lingual xbite)
from narrow mandible or wide maxilla
anterior xbite in primary dention indicates
skeletal growth problem and developing Class III malocclusion
- NOT self correcting so tx in mixed dentition
- most often assoc. with prolonged retention of primary tooth
- if tx is delayed, can lead to loss of arch length and you need M-D space
symptoms of digit sucking habit
anterior xbite, xbite, proclination of mx incisors, constriction of mx arch, retroclination of md incisors, class II
open bite
some teeth can’t be brought into contact with opposing
- NOT cuased by tongue thrusting
- tongue thrust SWALLOW is the result of displaced incisors, not a cause
most common sequelae of digit sucking is
anterior open bite
- usually asymmetrical
- more common in african americans (but deep bites are more common in caucasians)
which grows first, max or mandible?
maxilla, the mandible LAGS
posterior xbite can be corrected how
palatal expansion to expand nasal floor (will create diastema)
- this is a problem in the TRANSVERSE plane of space
- correct posterior xbites and mild anterior xbites FIRST (severe anterior xbite usually second stage)
most common active tooth movement in the primary dentition is to correct
a posterior xbite (transverse plane prob)
maxillary mandibular plane angle (MMPA)
Mandibular plane Go-Me line and
Maxillary plane ANS-PNS line
the greater MMPA, the longer the anterior facial height
long face -> Class II
short face -> Class III
mandibular plane angle
steep correlates with short or long anterior facial vertical dimension?
STEEP - long face - anterior open bite - Class II
FLAT - short face - anterior deep bite - Class III
poor man’s cephalometric
facial profile analysis
- AP position of jaws
- lip posture
- vertical face proportions
- inclination of mand plane angle
within lower 1/3 of face, mouth should be 1/3 of the way btw the nose and chin
most stable area to evaluate craniofacial growth is the __ cause of its early cessation to growth
anterior cranial base
frankfort-horizontal plane
connects PORION and ORBITALE
represents natural orientation of the skull
to predict time of pubertal growth spurt, get the most valuable info from a
wrist-hand xray
-ulnar sesamoid or hamate bones are landmarks
supervising a child’s development of occlusion is most critical from ages __ to __
7-10 (mixed dentition)
performing a mixed dentition analysis
- measure MD diameter of mand incisors and add
- measure space avail for mand incisors
- subtract, a NEG. means CROWDING
- measure space avail for canine and premolars on each side of arch
- calculate from table the size of canines
- subtract, a NEG. means CROWDING
for the max arch, what teeth are used to predict the size of max canines and premolars?
mandibular incisors
Moyer’s mixed dentition analysis
size of unerupted canines and PMs is predicted from knowing size (MD width) of mand incisors
never use max incisors (too much variation)
primate spaces are where in the:
max arch
mand arch
max arch - btw laterals and canines
mand arch - btw canines and 1st molars
relative to the primary mand. canines, the permanent mand. canines erupt in a __ direction
FACIAL, or are often right in line with the primary canines
in both arches, the permanent incisor tooth buds lie where in relation to the primary incisors?
LINGUAL and APICAL
leeway space is
diff. in total M-D width btw primary canine, first molar, second molar, permanent canine, first PM, second PM
permanent successors are usually SMALLER
mandibular = 3-4 mm maxillary = 2-2.5 mm
late mesial shift of permanent first molar
during canine-premolar transition peirod, permanent 1st molars grow MESIALLY into leeway space after the primary 2nd molars are lost
-causes a loss in arch length
serial extraction
removal of select primary and perm. teeth in predetermined sequence. indicated in severe class I malocclusion in mixed dentition.
Stages
- primary canines
- primary 1st molars
- permanent 1st premolars
interval btw ext is 6-15 mo.
-use lingual arch in mandible and hawley in maxilla
severe arch space deficiency in the permanent dentitition is > __ mm
10 mm, requires EXT
key to success in serial ext is to extract the 1st premolars before __ erupt
permanent canines!
usually concern is with permanent mand. canines and 1st PMs
in maxilla, after serial ext, the max canine will erupt down and back
most common impacted anterior teeth
MAX. CANINE
3 principals when tx planning an impacted tooth
- prognosis based on displacement and surgical trauma req for exposure
- flaps should be reflected so tooth is pulled through KERATINIZED tissue (NOT alveolar mucosa)
- adequate space should be in arch BEFORE you pull it out
assoc. of impacted canines with
missing laterals or short roots of laterals
what guides the eruption of canines?
distal aspect of the lateral roots
Supernumerary teeth
- more common in maxilla in midline
- 2:1 males more common
- assoc. conditions: Gardner’s, Down’s, Cleidocranial Dysplasia, Sturge-Weber syndrome
Oligodontia
more common in females
generalized causes of failed or delayed eruption are assoc. with
localized causes of failed or delayed eruption are
GENERAL
- hereditary gingival fibromatosis
- down’s syndrome
- rickets
LOCAL
- congenital absence
- abnormal position of crypt
- lack of arch space
- supernumerary teeth
- dilacerated roots
hyperparathyroidism causes what
premature exfoliation
maxillary diastema
98% 6 yr olds
49% 11 yr olds
-caused by tooth-size discrep, mesiodens, abnormal frenum attachment, or normal
-2 mm or less will close by itself
-if it’s cause of frenum -> frenectomy when permanent canines erupt
methods to close a diasetma
- lingual arch with finger springs
- hawley with finger springs
- cemented ortho bands
6 types of ortho movements
- tipping
- translation
- extrusion
- intrusion
- torque
- rotation
- tipping - rotation/pivot around axis of rotation (apical 1/3 of root)
- translation - coupled force, difficult
- extrusion
- intrusion - difficult
- torque - controlled root movement when crown is held stable, “uprighting”
- rotation - recurring rotation after ortho tx is from persistence of elastic supracrestal gingival fibers
what kind of fibers are assoc. with relapse after ortho rotation
supracrestal gingival fibers (free gingival and transseptal)
an appropriate candidate for post-ortho circumferential supracrestal fibrotomy is what tooth
a rotated max. lateral
-incise all collagen fibers inserted into the tooth, eliminates relapse potential
rationale for retention is to
allow reorganization of gingival and periodontal tissues
for an appliance to be effective in translating tooth roots, it must be capable of
exerting a torque
fixed ortho appliances offer controlled movement in all 3 planes of space. 4 basic components are:
bands, brackets, archwires, auxillaries
Alloys used for archwires are
1) SS - can be controlled widely by cold work
2) chromium-cobalt - can be supplied softer, and heat increases strength
3) titanium - good combo of strength, springiness, good formability
properties of an ideal wire for ortho should possess
high strength, high range, high formability, low stiffness
-loops and helices are incorporated to increase the activation range
quad helix
FIXED appliance
-consists of 4 helices (2 ant, 2 post) for POSTERIOR CROSSBITE cases from thumb sucking
unbuffered phosphoric acid 35-50%
etching agent for bonding of brackets, tooth looks frosted
DO NOT use topical fluoride before etching cause fluoride decreases enamel solubility
indications for bands instead of bonded brackets
better anchorage for movement, for teeth that need lingual and labial attachment, short clinical crowns, surfaces incompatible with bonding
band cementation with
GI cements due to F- release, use cold slab technique
indirect method of bonding brackets > direct method
pros and cons?
pros - less time, accurate placement, controlled resin thickness btw tooth and bracket, easy clean up
cons - more technique sensitive
used in situations where visibility is a problem ex. lingual appliances
most widely used appliance by orthodontists is the
FIXED EDGEWISE appliance
-tx comprehensive malocclusions of adolescent permanent dentition
Components
- Siamese twin bracket (max anterior teeth)
- Broussard buccal tube
- Straight wire bracket and bracket with a 0.0222 x 0.028 rectangular slot
- Wire is usually 0.125 x 0.028
takes how long to upright a molar
6-12 months
use a EDGEWISE appliance
stabilization should last until lamina dura and PDL reorganize ~ 2 mo. for simple upright, up to 6 for grafts
one of the most significant complications of molar uprighting is
high mandibular plane angle -> can cause open bite, loss of anteiror guidance
whip-spring appliances are used to
DE-rotate one or two teeth
Space maintainers that replace ONE prematurely missing primary tooth
- Band and Loop
- Distal Shoe
- B& L - for primary 1st molar
2. Distal shoe - for primary 2nd molar loss before the permanent 1st molar erupts (kids under 5 or 6)
Space maintainers that replace MULTIPLE prematurely missing primary tooth
- Lingual arch
- Nance
- Partial denture
- Lingual arch - primary 2nd molars or permanent 1st molars are banded, when permanent incisors have erupted
- Nance - bilateral loss of primary max. molars, prevents mesial rotation and drifting of permanent max. molars
- Partial - bilateral posterior space maintenance when incisors haven’t erupted, also for missing anteriors when esthetics an issue
Removable ortho appliances are generally restricted to what movement
TIPPING teeth
- Active removable - head gears, lip bumpers, vacuum formed
- Passive - bite planes, occlusal splints, retainers
indications of removable appliances
- retention after tx
- limited tipping
- growth modification during mixed dentition
most common removable retainer in ortho is the
Hawley retainer
- clasps on molars and outer bow with adjustment loops canine to canine
- palatal coverage make it possible to incorporate a BITE PLATE lingual to mx incisors to control bite depth (good for ppl with overbite)
Begg appliance
round wires that fit loosely into bracket’s vertical slot
Frankel’s appliance
removable app used for abnormal (hyperactive) soft tissue patterns
Headgear used to maintain
extra-oral anchorage and traction
-advantage is it PERMITS POSTERIOR MOVEMENT of teeth in one arch without disturbing the other arch
4 basic headgears
- cervical pull
- straight pull
- high pull
- reverse pull
Cervical pull headgear
- for distal and downward force against maxillary teeth and maxilla
- con = extrusion of max molars
- indications = Class II, Div I
Straight pull headgear
- like cervical but places a force in a straight distal direction from max molar
- indications = Class II, Div I
High pull headgear
- distal and upward force on max teeth and maxilla
- indications = Class II, Div II with open bite
Reverse pull headgear
EXTRAORAL component
-indications = Class III where protraction of maxilla is desirable
finger springs is the best method to
tip max and mandibular anterior teeth
Z-springs can also be used but delivery heavy forces
maxillary incisor rotation is best treated when
after all permanent teeth have erupted with simple removable appliances
Tissue borne functional appliances include (1)
Frankel’s
-expands arch by padding against the pressure of lips and cheeks on teeth, postures the mandible forward and downward
Tooth borne functional appliances include (4)
- activator - advances mandible to edge to edge to induce mandibular growth and correct Class II
- Bionator - similar to activator
- Herbst - fixed or partially removable, posture the mandible forward and induce growth
- Clark’s twin block - postures mandible forward with help of occlusally inclined guiding planes and bite blocks
first order bend in a wire is in which plane
HORIZONTAL
cartilage growth occurs 2 ways
- appositional
- interstitial
- appositional - recruitment of fresh cells, chondroblasts, add new matrix
- interstitial - mitotic division and deposit of more matrix around chondrocytes already in the cartilage, HYALINE CARTILAGE grows this way
sites of interstitial growth incl.
mandibular condyle, nasal septum, spheno-occipital synchondrosis
bone forms by either endochondral or intramembranous ossification
- begins in embryo where mesenchymal cells differentiate into fibrous membrane or cartilage
- grows by APPOSITION
- intramembranous - in membranes of osteoprogenitor cells. MAXILLA and MANDIBLE, flat bones of skull and part of clavicle form this way
- endochondral - remainder of skeleton, in hyaline cartilage model, for short and long bones
bone growth only occurs by __ growth
APPOSITIONAL
major site of growth of the mandible is the
CONDYLE
- resorption along anterior ramus creates space for mand. molars
- main growth thrust is UP and BACK causing the body fo the mandible to move DOWN and FORWARD
growth at the mandibular condyle during puberty results in
increase in posterior facial height
bone deposition in the __ region is responsible for lengthening of the maxillary arch
max tuberosity
-max arch elongates, moves posterior, and increases in height
alveolar bone only exists to
support teeth
-in a kid, the alveolar process grows in height and length to accomodate the developing dentition
space btw jaws into where the teeth erupt is provided by growth at the
mandibular condyles (esp. molars) -soft tissue development carries the mandible forward and down, and condylar growth fills the space to maintain contact with base of the skull
in infancy, ramus is located at the spot where what tooth will erupt
primary first molar
theory that explains why there is a strong tendency for mand anterior crowding in late teens and 20s is
late mandibular growth
- it says mand. incisors and maybe all mand. teeth move DISTALLY
- mandible undergoes more growth in this time than maxilla
most rapid losses in arch perimeter are usually due to
mesial tipping and rotation of the permanent 1st molar after removal of the primary 2nd molar
if a perm 1st molar is ext on a kid before the perm 2nd erupts, what do you do?
allow 2nd molar to erupt and mesially drift to close the space
when can a space maintainer be removed
when the perm tooth erupts through gingiva
most reliable indicator of readiness of eruption of a succedaneous (permanent) tooth and need for space maintainer is
extent of root development
