Orthodontics Flashcards
when do you do brief ortho exam?
9 years
when can an extensive ortho exam be done?
11- 12 – when premolars canine erupt
what is Ideal occlusion?
Rare
1. Molar relationship
* Distal surface of disto-buccal cusp of upper first molar occludes with mesial surface of mesio-buccal cups of lower 2nd molar
2. Crown angulation
3. Crown inclination
4. No rotations
5. No spaces
6. Flat occlusal planes
(Andrews 6 keys)
what is malocclusion?
Are more sig deviations from the ideal that may be considered unsatisfactory (aesthetically or functionally)
May require tx but pt factor may influence decision
what must you ask about in relation to PDH for ortho exam?
Ask about trauma to permanent dentition
* History of trauma
* Root resorption?
* RCT?
what habits are important to know of when doing ortho exam?
- Thumb sucking
- Lower lip sucking
- Tongue thrust
- Chewing finger nails
what are competent lips?
- Competent – lips meet at rest
o Relaxed mentalis M
what are incompetent lips?
o Lips that do not meet at rest
o Relaxed mentalis M
what is a lip trap? and what could a relapse lead to?
- May procline upper incisors
- May lead to relapse of overjet if persists at end of tx
what would hyper active lower lip do?
retrocline lower incisorS
What should you know about tongue when doing ortho exam?
Position
Habitual
Swallowing
in terms of tongue position and swallowing pattern when doing ortho exam what should you know?
- Tongue position and swallowing pattern
o Tongue thrust on swallowing can be associated with an anterior (AOB)
o Can be either endogenous or adaptive tongue thrust (cause or effect?)
o May cause relapse of AOB at end of tx if endogenous
what are occlusal effects of a thumb habit?
o Proclination of upper anteriors
o Retroclination of lower anteriros
o Localise AOB or incomplete OB
o Narrow upper arch +/- unilateral posterior cross bite
o Remember that effects will be superimposed on existing skeletal pattern and incisor relationship
what should you know about TMJ when doing ortho exam?
- Patho of closure
- Range of movement
- Pain, click from joint
- Deviation on opening
- Muscle tenderness
- Mandibular displacement
o Discrepancy in retruded contact position and inter cuspal position
o RCP does not equal ICP
o Displacement of mandible up and to the right from RCP to ICP -note center line position
what are the 3 planes facial skeleton is considered in?
- Antero-posterior
- Vertical
- Transverse
what is a class I skeletal?
maxilla 2-3mm in front of mandible
what is a class II skeletal?
maxilla more than 3mm in front
what is a class III skeletal?
mandible in front of maxilla
how do you check skeletal bases?
- Direct palpation of skeletal bases
how is vertical skeletal assessment done?
Frankfort – mandibular planes angle (FMPA)
how is lateral skeletal assessment done?
Mid sagittal ref line
what must you assess during IO for ortho exam?
- Crowding
- Space
- Rotations
- Palpate for canines if not erupted
- Note teeth of abnormal shape/size e.g peg lateral
- Lower arch – angulation of incisors to mandibular plane – upright, proclined, retroclined
- Upper arch – angulation of incisors to Frankfort plane – upright, proclined, retroclined
- Teeth in occlusion
what do you check when teeth in occlusion during ortho exam?
Max interdigitation or RCP
what involves with checking max interdigitation or rcp?
Incisor relationship
Overjet
Overbite/ open bite
Molar relationship (angle’s classification)
Canine relationship
Cross bites
Centre lines
what is incisor relationship classes?
o Class I
Lower incisor edges occlude with or lie immediately below cingulum plateau of upper central incisors
o Class II
Lower incisor edges lie posterior to cingulum plateau of upper incsiors
Division 1
- Upper incisors are proclined or of average inclination there is an increase in overjet
Division 2
- Upper central incisors are retroclined. The overjet is usually minimal or may be increased
o Class II
Lower incisor edges lie anterior to the cingulum plateau of the upper incisors. The overjet is reduced or reversed
what does molar relationship (angle’s classification) also mean?
buccal segment relationship
what is involved with buccal segment relationship?
- Angles classification
o Class I
o Class II
o Class III - Crossbites
what do you compare patient to parent for?
Malocclusion
* Especially class 3 malocclusions
Growth potential
what radiographs can you do for ortho exam?
OPT
Maxillary anterior occlusal
Lateral cephalogram
what is aetiology of malocclusion?
- skeletal
-dental - soft tissue
- other such as habits
what is definition of local cause of malocclusion?
localised problem or abnormality within either arch, usually confined to one, two or several teeth producing a malocclusion
what are some types of local causes of malocclusion?
variation in tooth number
variation in tooth size or form
abnormalities of tooth position
local abnormalities of soft tissues
local pathology
what are types of variation in tooth number?
- Supernumerary teeth (extra)
- Hypodontia (developmentally absent teeth)
- (variation of timing)
- Retained primary teeth
- Early loss of primary teeth
- Unscheduled loss of adult teeth
what is supernumerary tooth?
o A Tooth or tooth like entity which is additional to the normal series
where is a supernumerary most common?
Most commonly in anterior maxilla
Males > females
what are the 4 types of supernumerary?
- Conical
- Tuberculate
- Supplemental
- Odontoma
what is a conical supernumerary? where would it tend to be? what can it do?
o Small, peg shaped
o Close to midline (mesiodens)
o May erupt (extract)
o Usually 1 or 2
o Tend not to prevent eruption but may displace adjacent teeth
what does a conical supernumerary tend to do?
Tend not to prevent eruption but may displace adjacent teeth
what is a tuberculate supernumerary? what does it tend to cause? what does it tend to do and what do you tend to do?
o Tend not to erupt
o Paired
o Barrel-shaped
o Usually extracted
o One of the main causes of failure of eruption of permanent upper incisors
what is one of the main causes of failure of eruption for the permanent upper incisors?
tuberculate
what is a supplemental supernumerary? what is it most common? what do you do?
o Extra teeth of normal morphology
o Most often upper laterals or lower incisors
o Can be third premolars, 4th molars
o Often extract – decision based on form and position
what is a supplemental normally?
o Most often upper laterals or lower incisors
o Can be third premolars, 4th molars
what determines extraction of supplemental supernumerary?
decision based on form and position
what is an odontoma broken categorised as?
o Compound
Discreet denticles
o Complex
Disorganised mass of dentine, pulp and enamel
what is the definition of hypodontia?
developmental absence of more teeth
what is hypodontia commonly as?
o Females > males
o Commonly upper laterals (2s) > 2nd premolars (5s)
what is a retained primary tooth? when should you be worried?
o Disruption in sequence of eruption
o A diff of more than 6 months between the shedding of conta lateral teeth – alarm bells
when are you alarmed about a retained primary tooth?
A diff of more than 6 months between the shedding of conta lateral teeth
what are some reasons of retained primary teeth?
1. Absent successor
2. Ectopic successor or dilacerated
3. Infra-occluded (ankylosed) primary molars
4. Dentally delayed in terms of development
5. Pathology/ supernumerary
what would you do in the event of an absent sucessor?
- Either maintain primary tooth as long as possible (if good prognosis)
- Or extract primary tooth early to encourage spontaneous space closure in crowded cases
- Early ortho referral for advice
what is the defintion of infra-occluded (ankylosed) primary molars?
process where a tooth fails to achieve or maintain its occlusal relationship with adjacent teeth
what are some reasons for early loss of primary teeth?
1. Trauma
2. Periapical pathology
3. Caries
4. Resorption by successor
what would happed if primary incisor is extracted?
o Very little
o No compensating or balancing ext
what would you need to do if primary canine is extracted?
o Unilteral loss in crowded arch, can givr centre-line shift
o Will get some mesial drift of buccal segments
o Consider balancing extraction
what would happen if primary molar is extracted?
o More space loss with E’s > Ds
o More space loss in upper > lower
o 6s drift mesially and steal 5 space
how does when a primary tooth is extracted effect?
- Most effect when primary teeth extracted early
- Little effect if done late
what does balancing extraction mean?
- By extraction of a tooth from opposite side of same arch
- Designed to minimise midline shift
what does balancing extraction designed to do?
minimise midline shift
what does compensating extraction mean?
- By extraction of a tooth from the
o Opposing arch of same side - Designed to maintain occlusal relationship
what does compensating extraction designed to do?
maintain occlusal relationship
what is ideal choice for relief of crowding?
6s
* Planned loss early is better than enforced older
what are some factors that influence impact of loss of 6s?
- Age at loss
- Crowding
- Malocclusion
what is has more impact in loss of 6? upper or lower arch?
lower arch
what happens if lower 7s erupted late when 6 is lost?
- Often poor space closure
what happens if 6 is lost too early in lower arch? and when in particular?
- Distal drift of 5s, particularly is Es lost at same time as 6s
what is there the potential of when 6s are lost in upper arch in regards to crowding?
Potential for rapid space loss
what is there the potential of when 6s are lost in lower arch in regards to crowding?
Spaced -> will have spaces
Aligned -> will have spaces
Crowded -> best results likely
what does early unscheduled loss of central incisor result in?
result drift of adjacent teeth
what does late unscheduled loss of central incisor result in?
result long term space
what do you ideally do in instance of unscheduled loss of central incisor?
maintain space
- implant
- simple denture
what to do if lateral incisor drifts to fill space?
- Re-open space for prosthesis
- Build up lateral
what are types of variation in tooth size or form?
- Too large – macrodontia
- Too small – microdontia
- Abnormal form
what does macrodontia mean?
Tooth/teeth larger than average
Localised or generalsied
what are problems from macrodontia?
- Crowding
- Asymmetry
- aesthetics
what does microdontia mean? what does it link to and lead to?
Tooth/teeth smaller than average
Localised or generalised
Leads to spacing
Linked to hypodontia
what are some types of abnormal tooth forms?
o 1. Peg shaped laterals
o 2. Dens in dente
o 3. Geminated/fused teeth
o 4. Talon cusps
o 5. Dilaceration
o 6. Accessory cusps and ridges
what are some types of abnormalities of tooth position?
- ectopic teeth
what are ectopic teeth?
teeth that develop in abnormal locations in mouth
what are the most common teeth to be ectopic?
8’s
3’s
6’s
1’s
what do you check for upper 3?
Check for palpable buccal canine bulge from 9 years onwards
where do ectopic palatal 3s normal occur?
well aligned arches
when is there a higher incidence of ectopic 3s?
o Absent/peg shaped U laterals
o Class II, div 2 incisor relationship
what do you do for a clinical assessment of ectopic 3?
o 1. Visualisation/palpation of any obvious bumps of 3
o 2. Inclination of 2
o 3. Mobility of c or 2
o 4. Colour of c or 2
what kind of radiographic assessment is needed for ectopic 3? and what types of radiographs?
o 2 radiographs needed to localise position
Usually OPT and upper anterior obloque occlusal
- parallax
what are the management options of an ectopic 3?
o 1. Prevention
Appropriate monitoring from age 9 onwards
Clinical assessment
Symmetry
o 2. Extraction ‘c’ to encourage improvement in position of ‘3’ (interceptive)
o 3. Retain ‘3’ and observe (accept its position)
o 4. Surgical exposure and ortho alignment
o 5. (surgical) extraction
o 6. Autotransplantion
what do you do for palatally ectopic canines?
- surgically expose them and align them with fixed appliances
describe ectopic 6s? what can be done?
- More commonly U arch
- Reversible before age 8
- Caries risk
what are signs of ectopic 6s?
o Crowding (greater in CLP)
o Mesial path of eruption
o Abnormal morphology of E
what is management of ectopic 6s?
o 1. Separator
o 2. Attempt distalise ‘6’
o 3. Extract ‘e’
what do you check for in regards to ectopic 1?
o Sequence
o Symmetry
what are some possible causes of ectopic 1s?
o No obvious cause
o Supernumerary
Tuberculate
Odontome
o Trauma to primary predecessor
Ankylosis or primary tooth
Displacement of tooth germ
Dilaceration of root
what is dilaceration of root?
when the root of a tooth is abnormally curved or bent
what does transposition mean?
Interchange in position of 2 teeth
what is classification of transposition?
True/pseudo
what teeth are most commonly transposition?
- Upper canines and first premolar
- Lower canines and incisors
what are tx options for transposition?
- accept
- Extract
- correct
what are some local abnormalities of soft tissues?
- Digit sucking
- Fraenum
- Tongue thrust
what are outcomes of digit sucking?
1. Proclined UI
2. Retroclined LI
3. Anterior open bite
4. Unilateral posterior crossbite
* Due to narrow maxillary arch
* May cause mandibular displacement
what would labial fraenum cause?
median diastema
what are types of local pathology that would cause malocclusion?
- Caries
- Cysts
- Tumours
what is physiology basis of ortho?
If an external force is applied to a tooth, the tooth will move as the bone around it remodels
This bony remodelling is mediated by the periodontal ligament
If a tooth has no PDL or is ankylosed it will NOT move
Cementum is much more resistant to resorption than bone, although some degree of root resorption after orthodontics should be expected
what is bone remodelling mediated by?
PDL
what is piezo-electric theory?
- piezo-electric currents are generated when crystalline structures, such as bone, are deformed.
- once thought to be the prime mechanism by which tooth movement was modulated.
- however , these currents are relatively short-lived and very small so unlikely to play a significant role in bone remodelling
what is differential pressure theory?
in areas of compression bone is resorbed and in areas of tension is deposited
what is mechano-chemical theory?
The mechano-chemical theory of orthodontics proposes that tooth movement during orthodontic treatment is the result of a combination of mechanical and chemical factors. The mechanical aspect involves applying a controlled force to the teeth, causing bone deformation and remodeling, while the chemical aspect involves the biological response of the bone to the applied force. The theory suggests that the effectiveness of orthodontic treatment depends on both mechanical and chemical factors, and an understanding of the underlying biological mechanisms can help optimize treatment outcomes. Different types of appliances are used in orthodontic treatment to apply forces to the teeth, and the forces are carefully monitored and adjusted to achieve the desired tooth movement and minimize any adverse effects.
mechanical load is put onto fibres of what?
PDL
what do osteoblasts produce?
prostagladins and leukotrienes
what do fibroblasts produce in mechano-chemical theory?
matrix metalloproteinases (enzymes that break down the extracellular matrix)
what do macrophages increase in mechano-chemical theory?
interlukin 1 (IL-1)
osteocytes produce?
cytokine
cytokines activate what to recruit what?
osteoblasts to recruit osteoclasts
when cytokines active osteoblasts what do they produce?
prostagladins and leukotrienes
what do the postroglandins and leukotrienes cause osteoblasts to produce?
intracellular messenger (secondary messengers)
what do the intracellular secondary messenger initiate?
the production of receptor activator of nuclear factor RANKL and colony stimulating factor and interleukin-1
what does interleukin (IL-1) increase production of?
RANKL
what does RANKL and colony stimulating factor cause?
blood monocytes to fuse and form multinucleated osteoclasts
what does RANKL stimulate?
osteoclasts to become active and resorb the bone
what does the osteoblast do in areas of compression?
- they bunch up together to expose the osteoid layer giving osetoclasts the access to resorb bone
- osteoblasts send signs to osteoclasts (e.g RANKL) to recruit and activate osteoclasts to resorb bone
what does the osteoblasts do in areas of tension?
- they are flattened covering the osteoid layer and preventing osteoclasts from gaining access to the bone
- they secrete collagen and other proteins forming the organic matrix into which they then secrete hydroxyapatite crystals which forms new bone
what protein do osteoblasts release?
osteoprotegrin (OPG)
what does osteoprotegrin (OPG) prevent?
osteoclastic differentiation and suppresses their activity
how is bone remodelling regulated?
balance between amount of RANKL and OPG produced
what are types of appliances?
- removable
- functional
- fixed
how do functional appliances work?
- mandible postured away from normal rest position
- facial musculature is stretched which generates forces transmitted to teeth and alveolus
types of tooth movement?
Tipping
Bodily movement
Intrusion
Extrusion
Rotation
Torque
what is weight of optimum tipping force?
35-60 grams
what is weight of optimum bodily movement force?
150-200 grams
what is weight of optimum intrusion force?
10-20 grams
what is weight of optimum extrusion force?
35-60 grams
what is weight of optimum rotation force?
35-60 grams
what is weight of optimum apical root torque force?
50-100 grams
what is intrusion in relation to ortho?
pressure on the supporting structures is evenly distributed and bone resorption is necessary, particularly at the apical area and at alveolar crest
what is extrusion in relation to ortho?
tension is induced in the supporting structures and bone deposition is necessary to maintain tooth support
how long would you wear a twin block?
6-12 months
what is mode of action of functionals?
- skeletal change (30%), growth of mandible, restraint of maxilla
- dentoalveolar change (70)% retroclination of upper teeth, proclination of lower teeth?
- mesial migration of the lower teeth
- distal migration of the upper teeth
- combination of the above achieves class I
what is the effect of light force in ortho?
frontal resporption
what happens within PDL during light force?
hyperaemia
what is there a resorption of from pressure side during light force?
lamina dura
what happens to tension side during light force?
apposition of osteoid on tension side
how is remodelling of socket known as for light force?
frontal resoprtion
what happens to gingival fibres during frontal resorption?
appear not to become reorganised but remain distorted
moderate forces during ortho is related to which type of resorption?
undermining resorption
during moderate force what happens on pressure side?
occlusion of vessels of pdl
during moderate force what happens on tension side?
hyperaemia of vessels pdl
what kind of areas are on pressure side?
cell free areas on pressure side (hylinsation)
theres a period of what during moderate forces?
stasis
there is increases endosteal vascularity during moderate forces which is what?
undermining resorption
what happens to tooth during moderate forces?
relatively rapid movement of tooth with bone deposition on tension side - tooth may become slightly loose
what happens to pdl during moderate force at the end?
healing of pdl - reorganisation and remodelling
what are unwanted side effects of excessive force? when is there root resorption significant?
- Pain
o Necrosis and undermining resorption takes place resulting in permanent changes
Root resorption – significant If > 1/3 root length lost
Anchorage loss
Possible loss of tooth vitality
what are factors that affect the response to ortho force?
o Magnitude
o Duration
o Age
o Anatomy
No bone – wasting/cleft
Soft tissues
Mid-palatal suture
what are deleterious effects of ortho force?
o Pain and mobility
o Pulpal changes
o Root resorption
o Loss of alveolar bone support
o Relapse
how much movement of the tooth per month is ideal?
1mm
how long is treatment time for fixed appliances?
24 months
Why is the study of facial growth important to orthodontists?
o Insight into growth of the face
predict changes
utilize growth to correct malocclusion
time our orthodontics and surgery
o Understand development of facial anomalies
o To measure changes in growth and treatment using cephalometry
life in utero consists of what 2 phases and their times?
embryonic – 1-8 weeks
foetal – 8 weeks to term
All of the limbs and organs including the face have formed within the…?
first 2 months
what is nerual crest cell migration?
Neural crest cell migration is the process by which neural crest cells move from their site of origin in the neural tube to their final destination in various parts of the body during embryonic development
when do the neural fold fuse to form the neural tube?
towards end of week 3
what will failure of neural folds to fuse lead to?
failure to fuse will lead to spina bifida.
what does the neural tube develop into?
brain and spinal cord
what will failure of neural tube development lead to?
anencephaly
what are neural crest cells?
During the folding of the neural plate, cells develop from the ectoderm along the edge of the groove, termed neural crest cells.
what do neural crest cells do?
- These undergo extensive migration within the developing embryo and ultimately differentiate into many cell types e.g. spinal and autonomic ganglia; Schwann cells, adrenal medulla, meninges of the brain.
- This neural crest derived ectomesenchyme contributes to branchial arch cartilage, bone and connective tissue proper, as well as dental tissues - pulp, dentine, cementum and periodontal ligament.
when does formation of face occur?
Formation of the face occurs during the first eight weeks after fertilisation
defects of the face particularly midline is related to defects where?
defects of the anterior parts of the brain
most of the face forms from what?
Most of the face forms from migrating neural crest cells, either in the frontonasal process or the branchial arches. Interference with this migration can lead to severe facial deformities.
how does cleft formation come about?
Failure of fusion between the various facial processes or between the palatine processes
what do the migrating neural crest cells do in week 4?
form the frontonasal process and laterally the branchial arches
the skull can be divided into what 2 parts?
neurocranium
viscerocranium
what is neurocranium?
forms a protective case around the brain
what is viscerocranium?
forms the skeleton of the face
what is intramembranous bone formation?
Bone is deposited directly into primitive mesenchymal tissue.
Intramembranous bones include the vault of the skull, the maxilla and most of the mandible.
Needle-like bone spicules form, which progressively radiate from the primary ossification centres to the periphery. Progressive bone formation results in the fusion of adjacent bony centres.
what is endochondral bone formation? What does it form?
bones are preceded by a hyaline cartilage ‘model’
forms base of skull
Several centres of ossification which eventually fuse
what does the base of the skull undergo?
undergo endochondral ossification from multiple centres, starting with the basi-occiput at 10-12 weeks.
At birth cartilagenous growth centres remain between what?
the sphenoid and occipital bones and in the nasal septum
when does the anterior fontanelle close?
2 years
when does posterior fontanelle close?
1 year
Growth occurs at fibrous sutures in response to what?
intracranial pressure
growth of the skull continues until when?
7 years
maxilla and mandible form in what way?
intramembranously
what do maxilla and mandible develop adjacent to?
o Although the maxilla and mandible form intramembranously, they develop adjacent to a pre-existing cartilaginous skeletons - the nasal capsule and Meckel’s cartilage
o (6 weeks)
the mandibular processes develops what units?
o A condylar unit
o An angular unit
o A coronoid unit
o An alveolar unit
describe the condylar unit/
A condylar unit which forms the articulation and contains the largest secondary cartilage formation
describe the angular unit?
An angular unit which forms in response to the lateral pterygoid and masseter muscles;
describe the coronoid unit?
A coronoid unit which responds to temporalis muscle development (muscular processes).
describe the alveolar unit?
o An alveolar unit which forms only if teeth are developing.
the body of the mandible forms in response to what?
inferior dental nerve
what are the 3 main sites of secondary cartilage formation in mandible? and when do they cartilages appear?
- condylar cartilage
- coronoid cartilage
- symphyseal end of each half of the bony mandible
- between 12 and 14 IU
growth at the condylar cartilage continues until when?
20 years
Ossification of the face and skull commences when?
7-8 weeks
what is a primary abnomality?
Defect in the structure of an organ or part of an organ that can be traced back to an anomaly in it’s development (spina bifida, cleft lip, CHD)
what is a secondary abnormality?
Interruption of the normal development of an organ that can be traced back to other influences
what is deformation?
Anomalies that occur due to outer mechanical effects on existing structures
what is agenesia?
Absence of an organ due to failed development during embryonic period
what is sequence?
Single factor results in numerous secondary effects (PierreRobin)
what is syndrome?
Group of anomalies that can be traced to a common origin
(Trisomy 21 in Down’s Syndrome)
what are some facial syndromes arising from early problems with facial development? (1-8 week)
Foetal Alcohol Syndrome
Hemifacial microsomia
Treacher Collins syndrome (mandibulofacial dysostosis)
Clefts of lip and palate
describe foetal alcohol syndrome?
o microcephaly (small head)
o typical facies having
short palpebral fissures,
short nose,
long upper lip with deficient philtrum,
small midface
small mandible.
o Mild mental retardation
describe hemifacial microsomia?
o Multifactorial
o Neural crest cell migration? (day 19-28)
o 3D Progressive facial asymmetry
o Unilateral mandibular hypolasia, zygomatic arch hypoplasia, high arched palate, malformed pinna
o But clinical spectrum (ear tags only, to complete lack of condyle, coronoid and ramus)
o Normal intellect, deafness, cardiac and renal problems
describe treacher collins?
o Deformity of 1st and 2nd branchial arches, (day 19-28)
o Anti-mongoloid slant palpebral fissures
o Colomboma of lower lid outer 1/3rd
o Hypoplastic or missing zygomatic arches
o Hypoplastic mandible with antigonial notch
o Deformed pinna, conductive deafness
what are dental features of cleft?
o impacted Teeth
o Crowding
o Hypodontia
o Supernumeraries
o Hypoplastic teeth
o Caries
Syndromes associated with problems of development of the skull and facial bones?
o Achondroplasia
o Crouzon’s (craniofacial dysostosis)
what is achodnroplasia?
Problem with endochondrial ossification
Defects in long bones, short limbs =dwarfism(70%)
Defects in base of the skull, retrusive middle third of the face, frontal bossing, depressed nasal bridge
Defects in base of the skull, retrusive middle third of the face, frontal bossing, depressed nasal bridge
what is crouzon’s?
Premature closure of cranial sutures (esp coronal and lamdoid)
Proptosis (shallow orbits), orbital dystopia, mild hypertelorism
Retusion and vertical shortening of midface
Prominent nose
Class III malocclusion
Narrow spaced teeth
Early closure of the sutures is termed cranial synostosis and requires surgical intervention. e.g. Crouzon’s syndrome.
Distraction osteogenesis
what are sutures?
Specialised fibrous joints situated between intramembranous bone
Each suture is a band of connective tissue which has osteogenic cells in the centre and the most peripheral of these cells provide new bone growth
growth of sutures is a response to what?
growing structures separating the bone – e.g. growth of the calvarium in response to development of the brain. Where the bones are pushed apart new bone forms in the suture. In the suture growth occurs in areas of tension.
When facial growth is complete the sutures fuse and become inactive
where are synchondroses found? Exist between what?
These are found in the midline
They exist between the ethmoid, sphenoid and occipital bones
A cartilage – based growth centre with growth occurring in both directions. The bones on either side of the synchondrosis are moved apart as growth takes place.
New cartilage is formed in the centre of a synchondrosis as cartilage at the periphery is transformed into bone
when is the rate of growth greatest?
during first 3 years
how does growth occur in cranial vault?
- Bone growth at the sutures
- External and internal surfaces are remodelled through surface deposition and resorption to displace the bones radially
where do fontanelles form? How many present at birth and when do they close by?
more than 2 bones meet
-6 fontanelles are present at birth and these close by age 18 months. When facial growth is complete all of the sutures fuse
how does growth occur in cranial base?
Endochondral ossification
Surface remodelling
when does the spheno-ethmoidal synchondrosis fuse?
around 7 years
when does spheno-occipital synchondrosis close?
13-15 years in females
15-17 in males
when does spheno-occipital synchondrosis fuse?
around 20 years
how does cranial base play and important role in determining how the maxilla and mandible relate? In terms of angles
A small angle is more likely to be associated with a class III skeletal relationship
A large angle more likely to be associated with a class II skeletal pattern
what are Differences in the growth of the maxilla and mandible?
o Mandible
Increases in length by 26mm in males 20mm in females between ages 4-20 years
Growth accelerates significantly during the pubertal growth spurt
Growth slows to adult level around age 17 years in females and 19 years in males
o Maxilla
Increases in length by 8mm in males 5.5mm ( females) between ages 4-20 years
After age 7 years growth of the maxilla proceeds very slowly
Growth slows to adult levels at around age 12 years
what is a growth rotation due to?
A growth rotation is due to an imbalance in the growth of the anterior and posterior face heights
what does forward rotations lead to?
short face
what does backwards rotations lead to?
long face
how does adult facial growth affect you?
o Tendency to increased overall length and prominence of nose and chin (and forehead in men)
o Lips become thinner and more retrusive (soft tissue changes)
how to measure facial growth changes?
o Casts of the face
o Cephalometry
o 3D laser scanning
o 3D photogrammetry
what are indications for lateral cephalometry?
To aid diagnosis
Treatment planning
Progress monitoring
Research projects Indications for taking a lateral ceph.
how are lateral cephalometry good?
Reproducible - patient positioned in a cephalostat a set distance from the cone and the film
what do you identify and measure with a lateral cephalometry?
o Identify
Points, landmarks with precise definitions
Lines
o Measure
Lengths
Heights
Angles
o Relationship between jaws and cranial base
o Relationship between the upper and lower jaw
o Position of teeth relative to the jaws
o Soft tissue profile Analysis
what is eastman analysis?
Measures the antero-posterior position of the maxilla and mandible relative to the base of skull
what are errors in cephalometry?
o Radiographic projection errors
o Errors within the measuring system
o Errors in landmark identification
what are radiographic projection errors in cephalometry?
magnification
distortion
what are errors within the measuring system in cephalometry?
non linear fields
what are errors in landmark identification in cephalometry?
quality of image
landmark definition and location
operator and registration procedure
what is eruption of deciduous teeth
o 6 months-2.5yrs
o a-b-d-c-e
o lowers before uppers
when to extract natal/neo-natal teeth?
mobile and presents a risk of inhalation
Is causing difficulty with breastfeeding
what are most common natal tooth?
lower incisors
when does pre eruptive phase start and end?
starts when the crown starts to form and ends when crown formation complete / root formation about to start.
what is pre-eruptive phase?
The developing crowns move constantly within the jaws
Small mesial and distal tooth movements occur
The developing crowns reposition themselves in response to increasing length , width and height of the jaws
Movement of tooth crowns is contained within the bony crypts
when does eruptive phase start and end? And what is it split into?
starts as soon as the root starts to form and ends when the teeth reach the occlusal plane Split into intra-osseous stage and extra-osseous stage.
why do relative position of deciduous and permanent teeth alter in eruptive phase?
eruption of the deciduous teeth and increase in height of the surrounding alveolar bone
movements in eruptive phase occur in response to what?
- Positional changes of neighbouring crowns
- Growth of the mandible and maxilla
- Resorption of the deciduous tooth roots
what is the root formation part of intra osseous in eruptive phase?
- Root formation – starts with proliferation of the epithelial root sheath and continues with the production of dentine and pulp
just explain intra-osseous in eruptive phase?
- Root formation – starts with proliferation of the epithelial root sheath and continues with the production of dentine and pulp
- Movement of the developing tooth – in an occlusal or incisal direction (slow - several months)
- The reduced enamel epithelium fuses with the oral epithelium
- Within the Dental follicle degeneration occurs. Blood vessels decrease in number, nerve fibres break up into pieces. The resulting area becomes known as the ‘eruption pathway’
o In the periphery of the eruption pathway other fibres are formed from the dental follicle . This is known as the Gubernacular cord. Theory : this guides the teeth to erupt in the oral cavity - Adjacent to, and overlying, the teeth bone loss keeps pace with the occlusal movement of the teeth (osteoclasts and osteoblasts are constantly remodelling the bone)
what is eruption pathway?
- Within the Dental follicle degeneration occurs. Blood vessels decrease in number, nerve fibres break up into pieces. The resulting area becomes known as the ‘eruption pathway’
what guides the teeth to erupt in oral cavity and what is it known as?
In the periphery of the eruption pathway other fibres are formed from the dental follicle . This is known as the Gubernacular cord. Theory : this guides the teeth to erupt in the oral cavity
what is extra-osseous?
- Penetration of the tooth’s crown tip through the epithelial layers (fast 1-2 weeks )
- The crown continues to move through the mucosa in an occlusal direction until it contacts the opposing tooth (slow -several months)
- Environmental factors such as muscle forces from cheeks, lips and tongue help determine final tooth position
what is post-eruptive phase?
tooth movement / eruption continues as the root forms and throughout life in extremely small increments
what does movement in post eruptive phase occur in response to?
- Occurs in response to increases in height of the growing alveolar bone and jaws
- In response to attrition and abrasion
o teeth erupt slightly to compensate for wear on occlusal surfaces
o proximal surface tooth wear leads to mesial drift - In response to loss of opposing teeth = over-eruption
what does proximal surface tooth wear lead to?
o proximal surface tooth wear leads to mesial drift
what causes teeth to erupt?
Root formation
Remodelling of the alveolar bone
Development of the periodontal ligament (membrane)
combo of
where does signalling for teeth to erupt take place?
It is believed that signalling takes place between the dental follicle and the reduced enamel epithelium
what is tooth eruption controlled by?
Tooth eruption is controlled by a signalling cascade of cytokines (including Interleukin1, CSF 1, RANKL/ Osteoprotegerin pathway)
what are the roles of the dental follicle?
Initiates resorption of the bone overlying the tooth
Facilitates connective tissue degradation and creates the eruption pathway
Promotes alveolar bone growth at the base of the tooth
Provides traction forces within the periodontal ligament (special fibroblasts with contractile properties)
Ectomesenchymal cells from dental follicle contribute to root formation (cementoblasts and cementum)
what is definition of interceptive ortho?
Any procedure that will reduce or eliminate the severity of a developing malocclusion’
how is space gained to accomomadate larger anterior teeth of the permanent dentition?
- increase in the intercanine width through lateral growht of jaws
- upper incisors erupting onto a wider arc
- leeway space
what is leeway space of upper arch?
primary canine + first molar + second molar
minus
permanent canine + first premolar + second premolar
=
1 to 1.5mm
what is leeway space of lower arch?
primary canine + 1st molar + 2nd molar
minus
permanent canine + 1st premolar + 2nd premolar
=
2 to 2.5mm
what is diastema?
gap in between teeth
when should a diastema close?
<2.5mm
what are the management options if a first permanent molar gets stuck between the ‘e’ and fails to fully erupt?
- If patient <7years wait 6 months (90% self correct)
- Orthodontic Separator
- Attempt to distalise the first molar
- Extract E
- Distal disking of ‘e’
what is case assessment of unerupted central incisors?
- Case history –esp. regarding trauma
- palpate labially and palatally
- if retained Primary tooth present, Is primary mobile? Is it discoloured ?
- Radiograph (AOM/ Periapical)
how to deal with unerupted central incisor supernumeraries?
- Remove primary teeth & Supernumeraries
- Create space/maintain space
- Monitor for 12 months
If patient < 9 years (immature root apex)
Still fails to erupt? OR patient >9 years (mature root apex)
- Monitor for 12 months
- Expose/bond gold chain and apply orthodontic traction
what does early loss of decidous teeth cause?
localised crowding
how does the effect of localised crowding from early loss of deciduous teeth vry?
- Degree of crowding already present
- Age
- Which arch? Which tooth?
what is a balancing extraction and why?
o Balancing Extraction = removal of a tooth from the opposite side of the same arch
Why?
To maintain the position of the dental centreline (preserve symmetry)
what is a compensating extraction and why?
o Compensating Extraction = removal of a tooth from the opposing quadrant
Why?
To maintain the buccal occlusion.
what is management of early loss of A’s and B’s?
little impact
don’t balance or compensate
what is management of early loss of C’s
balance
what is management of early loss of D’s?
small CL. shift, balance under GA?
what is management of early loss of E’s
tend not to balance
major space loss
upper>lower
Consider space maintainer
describe compensating for a C?
if you remove an upper C you gotta remove a lower C
what are types of space maintainers?
- removable
- fixed
what is a type of removable space maintainer?
passive URA
what are typical components of passive URA?
o Retention e.g. clasp UR6,UL6 (0.7mmHSSW) Labial bow UR3 to UL3 (0.7mmHSSW) OR Southend clasp (0.7mmHSSW)
o Baseplate – extend acrylic around teeth to prevent unwanted mesial drift
o +/-Mesial Stop (0.6mm HSSW) on individual teeth if required
what would factors of extracting carious 6’s be?
o Age of patient / stage of dental development
o Degree of crowding
o Malocclusion type
when would the most ideal result of extracting carious 6’s?
o 7’s bifurcation calcifying
o 8’s present
o Class 1 av/reduced OB
o Moderate lower crowding
o Mild/moderate upper crowding
what are general rules for extracting class 1 6’s?
o If extracting lower take upper
o Don’t balance with sound tooth. Don’t balance if well aligned or spaced.
o If extracting upper don’tneed to take lower.
how to clinically assess anterior cross-bites?
- displacement
- mobility of lower incisor
- tooth wear
- gingival recession
what are types of cross bite?
- Posterior Unilateral Crossbites
- posterior cross-bites
- anterior cross-bites
what does anchorage mean?
prevention of unwanted tooth movements
when is treatment of posterior unilateral cross bite needed?
only if it shifts midline by >2mm. so if pt bites down and between the motion to RCP he laterally shifts >2mm then thats treatment needed
what is digit habit management?
- positive reinforcement
- bitter-tasting nail varnish
- glove on hand, elastoplast
- habit breaker appliance (habit deterrent) - fixed or removable
breakdown interceptive ortho and what you do and for what?
-unerupted incisors - remove ob/space/obs
- impacted 6’s - observe 6/12 or intercept
- balance c’s - but not critical
- carious lower 6’s - take upper
- uni cross bites - IOTN displacement?
- habits - stop before 9
what can be used to help fix habits?
detterents apliance
Why is correct orthodontic diagnosis important?
Orthodontic appliances can move teeth very well,
but can modify skeletal relationship minimally.
A severe skeletal discrepancy may require
surgical intervention.
what are objectives of ortho treatment?
To produce an occlusion which is:
- Stable
- Functional
- Aesthetic
And to facilitate other forms of
dentistry (crowns, bridges etc.)
what are stages of treatment planning?
- Plan around the lower arch (angulation of LLS is stable)
- Decide on treatment in lower (ext/nonext)
- Build upper arch around lower
aim for class I incisor and canine relationship (OJ and OB normal*) - Decide on molar relationshipClass I or full unit class II molar relationship
(if upper and lower incisors normal size, shape and number)
what do you look to examine in lower arch?
- Crowding / Angulation of incisors Mand plane
- Angulation of the canines / Centrelines
- Curve of Spee
Space required? What are the options?
Extraction or non extraction?
what do you look to examine in upper arch?
- Crowding /Angulation of incisors to the Max Plane
- Angulation of the canines / Centrelines
what do you examine when teeth in occlusion ICP?
Incisor relationship
OJ
OB (curve of Spee)
Centrelines
Canine relationship
Molar relationship
what do you consider when assessing crowding?
Do you need to extract teeth?
Measure space available and space required
Overlap technique
what are the general principles in space required in lower arch?
Mild (0-4mm)
moderate (5-8mm)
sever (8+mm)
what are the general principles in space required in lower arch?
if mild (0-4mm)
non-ext (stripping)
ext 5’s
what are the general principles in space required in lower arch?
if moderate (5-8mm)
ext 5’s
ext 4’s
what are the general principles in space required in lower arch?
if severe (8+mm)
ext 4’s
what are the general principles to consider when considering lower arch extraction when yes and no?
yes
- extract in upper arch (MR class I)
No
- extract in upper arch (MR class II)
- Distalise UBS using headgear (MR class I)
what are treatment options?
- Accept malocclusion
- Extractions only
- URA
- Functional appliances
- Fixed appliances
- Complex treatment involving orthodontics and restorative treatment or orthodontics and orthognathic surgery
what are limitations of ortho treatment?
Effects of orthodontic treatment are almost purelydentoalveolar and tooth movement, with little effect on theskeletal pattern.
Tooth movements are limited by the shape and size of thealveolar processes.
Teeth will only remain stable in a position where there isequilibriumbetween the forces of the soft tissues, theocclusion and the periodontal structures. All other positionsare unstable and will be prone to relapse.
what do you asses clinical for anterior cross bites?
Displacement?
Mobility of lower incisor
Tooth wear
Gingival recession
why treat anterior open bite early?
o To maximise potential for spontaneous correction of anterior open bite whilst there is still eruptive potential for incisors (8-10 years/ root formation still incomplete)
o To prevent effects on vertical and transverse skeletal development which could lead to permanent skeletal change if habit persists
what are steps of digit habit management?
o 1. Positive reinforcement
o 2. Bitter-tasting nail varnish
o 3. Glove on hand, Elastoplast
o 4. Habit breaker appliance (habit deterrent) – fixed or removable
what is the aetiology of infra occluding teeth?
ankylosis of primary tooth. surrounding alveolar bone continues to grow. primary tooth gets left behind?
what is the diagnosis of infra occluding teeth?
- perucssion
- check for mobility
- radiographs
what do you assess radiograph for with infra occlusion?
- presence /absence of successor
- Ankylosis of primary tooth (no PDL space/no clear lamina dura)
- Root resorption of primary
what do you do if permanent successor is present when dealing with infra occlusion?
- Monitor 6-12 months
- Extract if primary tooth is below the interproximal contact point
- Consider extraction if root formation of successor near completion
- If extract …..maintain space
- Be more vigilant in upper arch
how long do you monitor permanent successor present for infra occlusion?
6- 12months
when do you extract if permanent successor is present when dealing with infra occlusion? and what do you do after if you extract?
- Extract if primary tooth is below the interproximal contact point
- Consider extraction if root formation of successor near completion
- If extract …..maintain space
what are doing nothing if permanent successor is present when dealing with infra occlusion?
- Permanent successor can become more ectopic
- Infra-occlusion worsens with tipping of adjacent teeth - primary tooth becomes inaccessible for extraction
- Caries and periodontal disease
when does infra occlusion worsen?
- Infra-occlusion worsens with tipping of adjacent teeth - primary tooth becomes inaccessible for extraction
when dealing with infra occlusion what does treatment plan depend on if permanent successor is absent?
o degree of crowding
o degree of infra-occlusion
o any other features of malocclusion ?
when dealing with infra occlusion what do you do if you extract when permanent successor is absent?
plan space mangement
o Either maintain space for prosthetic tooth
o Reduce space to one premolar unit ( requires fixed appliance)
o Close space ( fixed appliance)
in delayed eruption when should you assess position of upper canines?
- Assess position of upper canines from (9 to) 10 years onwards
- Should palpate by 11 years
- Mobile C’s, symmetry
- Angulation of lateral incisors
when is extraction fo the c’s likely to be successful?
o Patient is age between 10-13 years
o The canine is distal to the midline of the upper lateral incisor
o There is sufficient space available
o The canine is less than 55 degrees to mid-sagittal plane
what are the risks of doing nothing when dealing with ectopic primary maxillary canines?
o Permanent successor can become more ectopic
o Permanent canine then fails to erupt (Impacted Canine)
o Risk of root resorption of adjacent teeth
o Risk of root resorption of canine crown (lower risk)
o Risk of cyst formation around canine (rare)
o Permanent canine can become ankylosed (incidence tends to increase with age)
what are the options for growth modification for interceptive treatment of class III?
- Protraction headgear +/- RME (rapid maxillary expansion)
- Functional appliances e.g.Reverse Twin Block / Frankel III
when is growth modification in class III most successful?
- skeletal I or only mild class III
- maxillary retrusion
- anterior displacement on closing
- avergae or reduced lower face height
- patient age 8-10 years
what are general aetiological factors of malocclusion?
Skeletal
Muscular
- form and function of muscles that surround teeth
dentolveolar
- size of teeth in relation to size of jaws
what are possible environmental factors of malocclusion?
masticatory muscles
mouth breathing
head posture
in class 1 skeletal what may jaws have?
jaws usually correctly sized but may have bi-maxillary protrusion or retrusion
what is a lateral cephalogram?
- standardised lateral radiographs of the face and base of skull
- reproducible – pt position in a cephalostat a set distance from cone and film
what is radiographic technique of lateral cephalogram?
- ALARA
o Aluminium soft tissue filter
o Thyroid collar
o Triangular collimation
o Fastest film possible (60-70kV)
where is the frankfurt plane measure from?
lower orbital rim to superior border of external acoustic meatus
where is mandibular plane?
lower border of mandible
where do manibular and frankfurt planes meet?
external occipital protuberance
what is a long facial type from? what tendency does it tend to have?
- backward mandibular growth rotation
- anterior open bite tendency
what is a short facial type from and what does it tend to have? what tendency does it have?
- forward mandibular growth rotation
- deep overbite tendency
what doe arches with discrepancies tend to have?
causes unilateral or bilateral buccal segment cross bite
when does mandibular displacement occur?
occurs when inter arch width discrepancy causes upper and lower teeth to meet cusp to cusp
what is dental causes of facial asymmetries?
- displacement of normal mandible due to unilateral cross bite
what is crowding caused by?
small jaws normally sized teeth
macrodontia
what is macrodontia?
large teeth
what is spacing caused by?
large jaws, normally size teeth or small teeth microdontia
in class 1 cephalometrics what does SNA, SNB and ANB relate to?
o SNA relates maxilla to anterior cranial base
o SNB relates mandible to anterior cranial base
o ANB relates mandible to maxilla
in class 1 cephalometrics what is average value of SNA?
ave value 81 degrees +/- 3 degrees
in class 1 cephalometrics what is average value of SNB?
ave value 78 degrees +/- 3 degrees
in class 2 cephalometrics what is ANB value?
ANB > 5 degrees
in class 3 cephalometrics what is ANB value?
ANB < 1 degree or negative
what is upper anterior face height measured from?
Brow ridge (glabella) to base of nose
what is lower anterior face height measured from?
Base of nose (sub nasale) to inferior aspect of chin (soft tissue menton)
what is average ratio of lower anterior face height to total anterior face height?
Average ratio LAFH to TAFH = 50 percent
what is average value of FMPA?
27 degrees +/- 4 degrees
for long facial height what is the fmpa and LAFH to TAFH values?
o LAFH to TAFH proportion > 55 percent
o FMPA > 31 degrees
for short facial height what is the fmpa and LAFH to TAFH values?
o LAFH to TAFH proportion < 55 percent
o FMPA < 23 degrees
