CTB Flashcards
Concresence
Fusion of teeth after eruption due to fusion of their cementum surfaces
Causes of concrescence?
Crowding or trauma
Dilacerated root?
Cause
Curved or bent roots
Developmental trauma
Cause of multiple (lateral) roots?
Abnormal folding of HERS
IF cleft palate fuses with premaxilla what teeth are likely to not develop?
Lateral incisors
Process of tooth development with signalling molecules involved in enamel knot formation
Initiation stage - overlapping gradients of signalling molecules (BMP and FGF) cause transcriptional response in dental mesenchyme (PAX9 and MSX1). Determines tooth position
Bud stage - mesenchyme secretes FGF and BMP and induces formation of enamel knot in dental epithelium
Cap stage - enamel knot secretes signalling molecules, BMP induces cell cycle arrest in enamel knot cells, FGF induces cell proliferation in surrounding cells. determines tooth shape
2 processes the mandible undergoes during growth in adult displacement and relocation?
Adult growth = bone remodelling Bone formation (osteoblasts) Bone resorption (by osteoclasts)
Rotations within the mandible, causes and results?
Forward rotation, due to excessive growth in posterior face height = deep bite
Backward rotation, due to excessive growth in anterior face height = open bite
How does anterior and posterior face height increase?
Growth at cervical region of vertebrae displace head from shoulder girdle
This causes stretch of muscles from mandible to skull base, from mandible to hyoid and from hyoid to should girdle
This causes descent of mandibular symphysis and hyoid bone resulting in increased anterior face height
Growth of condyle = increased posterior face height
How does craniosynostosis change head shape?
Premature fusing of sutures of the skull
So brain expansion causes excess bone growth in the parallel direction to ensure intracranial pressure does not increase
Saggital craniosynostosis = long
Coronal = wide
Why is cementum thicker at apical and interradicular regions?
This is where cellular cementum is deposited as we age due to masticatory forces to ensure tooth stays in occlusion
Histological difference between cervical loop and HERS?
Cervical loop = IEE, OEE, SI, SR
HERS = IEE and OEE only
Formation of enamel pearls
Epithelial rests of mallassez formed when HERS stretches and degenerates but leaves remnants
Epithelial rests can form enamel pearls
Due to localised attachment of rests to predestine due to lack of cementum. Signs from pre-dentine could cause HERS cells to differentiate into ameloblasts (Stem cells) or if remnants of SI, SR stuck in HERS, they can then signal ameloblast differentiation
What is the cerivical loop and what is its role?
Growing end of the enamel organ (IEE, SR, SI, OEE), involved in cell interactions and root formation
How is cervical loop involved in crown formation?
IEE of the cervical loop separated from dental papilla by a cell free zone
IEE elongate into pre-ameloblasts and release signals for differentiation of odontoblasts from dental papilla cells
Odontoblasts align and produce pre-dentine
Signals from odontoblasts in pre-dentien induce differentiation of pre-ameloblasts into ameloblasts and produce pre-enamel
How is cervical loop involved in root formation?
IEE and OEE of the cervical loop proliferate down after crown formation and form a double layer of epithelial cells = HERS
A child presents with opacities on the occlusal side of the incisors and all four first molars. You ask if she used to swallow toothpaste as a baby and when learning to first brush teeth or whether she is from a foreign country. What problem are you trying to eliminate?
Dental fluorosis
What do cephalometric line show?
Angles
Determine skeletal pattern and anteroposterior position of dentition
2 classes of skeletal relationship according to angles and what do both show?
Class II = retrognathic = mandible posteriorly displaced
More acute angle associated with taller head (docicephalic)
Div I = U1 proclined = larger overjet
Div II = U1 retroclined = normal overjet
Class III = prognathic = mandible more anteriorly displaced = more obtuse angle
associated with wider head (brachycephalic)
Compensation of mandibular rotation
Skeletal compensation - open bite (backward rotation)
Growth of wider ramps will more mandible forward
Dento-alveolar compensation - open bite means mandibular incisors grow up and maxillary incisor grow down to reach occlusion = curve in occlussion
Width of mantle dentine?
20-150 micrometres
How is mantle dentine framed and what are its properties?
Formed from newly differentiated odontoblasts (first to be formed), lacks phosphoprotein, highly acidic and attracts calcium = reduced demineralisation
Loosely packed collagen fibrils and strongly branched tubules = prevent cracks
Width of dentine in root corresponding to mantle?
Hyaline = 20 micrometres
Size of PDL
0.15-0.38mm - thinnest in the middle PDL thickness decreases with age 11-16 = 0.21 mm 35-53 = 0.18mm 53-67 = 0.15 mm Mastication increases PDL remodelling = increased width in areas of tension not compression
Disease affecting all enamel in teeth?
Amelogenesis imperfecta
What fails to fuse in bilateral and unilateral cleft palate?
Bilateral = failure of both maxillary processes to fuse with medial nasal process Uni = on one side so only one maxillary process
What is the structure of the Trabecular bone, what does it contain, and why is it a structural component of the bone given that the compact bone is harder?
Trabecular bone contains many cavities filled with bone marrow interrupted by a network of bone plates
Compact bone is harder and forms the outer layer but it is very dense, trabecular bone allows the bone to be light and moveable
Osteocytes - how are they connected what is the purpose of this?
Osteoblasts that have become trapped in matrix
Linked by cannaliculi - exchange nutrient and mechanical sensors to maintain bone integrity
Direction of cannaliculi of cementocytes? why?
Towards the PDL
Connects cells to PDL to provide nutrients to cementocytes
REE
Function
Remnants of enamel organs and flattened ameloblasts
Surrounds the erupting tooth and prevents enamel from being resorbed by osteoclasts. Forms the JE
Function of layers of the enamel organ
OEE = cuboidal = exchanges substances with DF (nutrients and waste) via capillaries DF = condensed mesenchymal cells surround the enamel organ = form the periodontium. Provide nutrients to OEE. Some capillary links with ameloblasts (when enamel and dentine form links with DP destroyed) DP = condensed mesenchyme cells beneath the EO = form odontoblasts and fibroblasts of the pulp SR = star shaped cells operated with GAGs between = protects the developing tooth and maintaining shape (cushioning) SI = flat epithelial cells = ameloblast supporting function and produce alkaline phosphatase which aids mineralisation IEE = form ameloblasts which form enamel (pre-ameloblasts signal fro odontoblast differentiation)
What are the embryological origins of the olfactory sensory epithelium?
Olfactory placodes and neural crest cells
Hypertolerism
Large distance between eyes
What does HERS form?
Epithelial rests of Malassez which allow dental follicle cells to enter and differentiate into cementoblasts
Give an example of a hyperplasia that causes problems during extraction? Why?
Hyperplasia = over secretion/formation
Hypercementosis = abnormally high cementum deposition
May result in attachment to surrounding alveolar bone or other teeth
Problems associated with HERS
Abnormal folding can cause the formation of lateral roots
It can form epithelial rest of Malassez which can from periodontal cysts and enamel pearls in cementum
Embryological origin of HERS?
Proliferation of IEE and OEE from cervical loop after crown completion
IEE and OEE = epithelium = ectoderm
Structural difference between primary and secondary dentine
Visible change in tubule direction between the 2
Secondary dentine at the pulp border has fewer tubules and is unevenly distributed around the pulp chamber
Primary has more tubules (more odontoblasts when they were formed), the tubules are straighter
What is growth through primary and secondary displacement?
Primary displacement - growth in one one location causes the bone to be pushed away from other structures
Secondary displacement - Bone displaced as a result of growth of another bone
Example of primary and secondary displacement in nasomaxillary complex
Primary - growth at sutures causes forward and downward displacement e.g. growth at zygomaticomaxillary suture = maxilla down and forward
Secondary - growth of the middle cranial fossa displaces the nasomaxillary complex forward and down
Example of primary and secondary displacement in mandible?
Primary - condylar growth = forward and downward displacement
Secondary - growth of cranial base moves mandible forward and down
Reversible pulpitis
Short duration of pain that disappears when stimulus is removed (thermal and sweet)
Irreversible pulpitis
Long duration of pain that doesn’t disappear when stimulus is removed.
Cold can make pain better by reducing pressure
Management of reversible vs irreversible pulpits?
Reversible = remove irritant and restore, preserving pulp Irreversible = pulpotomy, pulpectomy or extraction
Identifying feature of apical periodontitis
Symptomatic = tenderness to pressure and widening of apical PDL
Symptomatic and non-symptomatic = apical radiolucency
Identifying feature of apical accesses
Tenderness to pressure
Radiolucency
Swelling
What is condensing osteitis? Identifiable feature?
Inflammatory disease after dental infection causing bone formation
Radiopaque
Alveolar osteitis?
after tooth extraction the socket fills with blood and forms a clot
Detachment of the clot can cause bone inflammation - bad odour
Identifiable feature of cracked cusp syndrome?
Small crack hard to see
Sharp pain on mastication
Pain goes when biting released
Identifiable features of pulp necrosis
Tooth much darker in colour
Identifiable feature of ankylosis
Tinny on percussion
What is ankylosis? - consequence
Fusion of tooth to bone - infraocclusion
Calcium hydroxyapatite formula
Ca10(PO4)6(OH)2
Solution of pH 9 on tooth
Critical pH 5.5, below this is rapid demineralisation
Normal pH of mouth 6.2-6.5
Above this the equilibrium moves to left and remineralisation occurs = bond making = exothermic reaction = temperature rise
Mechanism of F- action that contribute to caries resistance?
When bacteria produce acid hydroxyapatite dissociates
Can then bind to fluoride which has a reduced solubility product = more resistant to acid
Why not give tetracylines to children?
High affinity for calcium, during development it would be incorporated into tooth structure and result in dark brown spots in enamel
Signalling molecule determining tooth shape?
BMP, FGF
Function of osteocytes
Presence of canaliculi allows recruitment of osteoblasts and osteoclasts to maintain bone homeostasis
When do paired primary cartilages develop?
6 weeks i.u
When do secondary cartilages develop?
10 weeks i.u
Name 3 secondary cartilages?
Condyle, coronoid and sympyseal
4 bone remodelling stages
- Resorption - active osteoclasts = bone resorption
- Reversal - disappearance of osteoclasts (apoptosis or migration)
- Formation - activation of osteoblasts
- Resting - cessation of been formation - surface covered in flat bone lining cells
Male vs female skull
Female = flatter and more delicate, zygomatic bone more prominent Male = bulky, wide long nose, large overhang of supraorbital ridges
Dentine that forms too quickly?
Interglobular
Difference between pre-enamel and pre-dentine?
Pre-enamel is already partially mineralised (30%)
Pre-dentine is completely unmineralised = 100% protein matrix
3 risks of orthodontic treatment
Root resorption (especially if history of trauma) Decalcification Relapse (PDL) Transient inflammatory response in pulp PD due to difficulty cleaning
Component of Tomes processes
Distal portion = prismatic (rod) enamel
Proximal portion = inter prismatic (inter-rod) enamel
Advantages of prism decussation
Prevent propagation of cracks
Function of MSX1
Transcriptional response in dental mesenchyme to allow determination of tooth position - causing formation of enamel knot
Determines tooth identity (incisors)
Histological features present at late bell stage
Pre-dentine Pre-enamel SR Cervical loop Dental lamina breaks down
A patient comes into clinic with sensitivity to hot and cold drinks, he has sharp pains but no carious lesion present. What is this and how would you treat it?
Pulpitis
Pain isn’t relieved by cold so probably reversible pulpitis
Remove irritant and restore, preserving the pulp.
Irreversible = pulpotomy, pulpectomy or extraction
What is a risk faced in the 3-8 week period of craniofacial development and what is the reason?
Weeks 3-8 = embryonic period (craniofacial development)
High susceptibility to teratogens
Failure of neural tube to close - anacephaly
Incomplete removal of dental lamina result in:
Eruption cysts
Supernumary teeth
Odontomes
Why does sclerotic dentine and dead tracts form, how does it differ in the root and crown, and why does it appear transparent?
Sclerotic = continues peritubular dentine formation to occlude tubules = transparent due to increased mineralisation
Dead tracts = recession of odontoblast processes in tubules = air filled
May be that root = due to ageing and mastication
Crown due to caries
Result of PAX9 and MSX1 mutation?
Characteristics?
Hypodontia
PAX9 = missing molars
MSX1 = missing pre-molars
Role of submucosa
Loose connective tissue containing BV, N glands
Mobility and cushioning
Phases of tooth development?
Initiation, morphogenesis, histogenesis
Problems in children with posterior cleft palate?
Cannot eat and breathe = problems breastfeeding
Speech difficulties
3 functions of HERS
Extends around the pulp and defines future root shape
IEE of HERS induce odontoblast differentiation = root dentine
Curved end = epithelial diaphragm = primary apical fo.
Disintegration of HERS causes differentiation of odontoblasts, cementocytes and fibroblasts from DF
Bone holding anterior teeth structures?
Pre-maxilla
4 functions of REE
Fuse with OE to form a continuum so no bleeding on eruption
Protects the erupting crown from resorption by osteoclasts
Form JE
Forms Nasmyths membrane
Cephalometry
a) Sella
b) Nasion
c) Orbitale
d) A
e) ANS
f) PNS
g) B
h) Menton
i) Gonion
a) centre of sells turcica
b) point when frontal and nasal bones meet
c) base orbit
d) Deepest concavity on anterior maxilla
e) anterior nasal spine = tip of anterior maxilla
f) posterior nasal spine = posterior tip of maxilla
g) deepest concavity on anterior mandible
h) lowermost point of mandibular symphysis
i) most posterior-inferior point on angle of mandible
Cartilages giving rise to
a) lesser and greater wing of sphenoid
b) body of sphenoid
c) temporal
d) nasal cartilage
a) ala orbitali and ala temporalis
b) hypophyseal and trabecular
c) optic capsule and parachordal
d) paired nasal and prechordal
Most common cause of white patches in mouth?
Candida albicans
Most abundant type fo collagen in PDL?
Type 1 = fibrillar
type 3 = reticular
Why are BV near PDL fenestrated?
To allow passage of nutrients to other cells e.g. cementocytes
What type of bone is made in response to fracture?
woven
What type of bone attached bone to PDL?
Bundle bone
Which movement requires a low orthodontic force?
Intrusion (15-25g)
How much force does tipping require?
50-75g
How much force does rotation and extrusion require?
50-100g
How much force does translation require?
100-150g
How does enamel repair?
Physicochemical processes
Remineralisation
What fibre resists tooth extraction and intrusion
Extraction = oblique Intrusion = alveolar crest, apical and interradicular
Name long period phasic lines in
a) enamel
b) dentine
a) Striae of Retzius
b) Andresen lines
Name short period lines in
a) enamel
b) dentine
a) cross-striations
b) Von-Ebner lines
What cell has tight junctions distally?
Ruffle-ended ameloblasts
Functions of ruffle ended ameloblasts
Increase mineral content of enamel
Function of smooth-ended ameloblasts
Decrease organic content of enamel
What cell has tight junctions proximally?
Smooth-ended
Describe the cranial base angle of retrognathic profile
Cranial base angle more obtuse = backward rotation of the mandible
Describe the cranial base angle of prognathic profile
Cranial base angle more acute = forward rotation of mandible
What head form, occlusion and mandible type would a small cranial base flexion person have?
Class III
Brachycephalic head
Prognathic jaw
Forward rotated mandible
What occurs during gastrulation?
Formation of ectoderm, mesoderm and endoderm, they fold
Derivatives of ectoderm?
Epithelium, CNS, neural rest cells
Muscular and skeletal derivatives of pharyngeal arches
I = trigeminal = muscles of mastication, mylohyoid. Malleus, incus, meckels cartilage II = facial = muscles of facial expression, stapediua, stylohyoid. Stapes, styloid process, lesser horn of hyoid III = glossopharyngeal = stylophayrngus. Greater horn of hyoid IIII = Vagus = pahyengeal and laryngeal muscles. Laryngeal cartilages
How are neural crest cells specified?
By opposing gradients of signalling molecules at the border between neuroectoderm and epidermis
Fate of neural crest cells
Migrate to pharyngeal arches (due to signalling molecules)
Formation fo primary palate?
Merged medial nasal processes that continue inwards towards oral cavity
Persistence of oronasal membrane?
Choanal atresia = narrowing or blockage of basal airway by tissue
Formation of secondary palate?
Lateral outgrowths of maxillary processes (palatal shelves) grow downwards (7 weeks) Shelves elevate (8 weeks) Shelf fusion (9weeks)
Incomplete removal of medial epithelial seam?
Palatal cyst
Torus palatinus?
Benign overgrowth in midline of hard palate
Enchondondral ossification?
Example?
Bone made from cartilage model (produced by chondrocytes and replaced by osteoid)
Condyle of mandible
Base of skull (synchondroses)
Intramembranous ossification?
Example?
Bones made of osteoclasts differentiated from mesenchymal stem cells
Mandible
Maxilla
Sutural ossification?
Example
Bones made from osteoblasts from mesenchyme but sutures proved fibrous connection =stability
Post-natal growth of skull
Perichondrium
Formation
Source of cells that make chondrocytes
Formed from chondrocytes derived from condensed mesenchymal cells
Structure of epiphyseal growth plate
Resting chondrocytes = reservoir to replenish chondrocytes being made into osteoblasts)
Proliferation chondrocytes = growth in one direction
Prehypterophic chondrocytes = swollen, increased cartilage matriculates
Hypertrophic chondrocytes = very large and swollen = fully matured
Calcification zone = cartilage being replaces by osteoblasts
Synchondroses
Growth?
Cartilaginous jointed of cranial base
Mirror image of 2 epiphyseal growth plates allows growth in both directions
Epiphyseal cartilage vs condylar cartilage
Epiphyseal = growth of endochondral bones (cartilage formed from chondrocyte proliferation, maturation and hypertrophy) Condylar = mediates growth of intramembranous bone = mesenchymal cells respond to functional loading and differentiate into chondrocytes. random alignment = multi-directional growth
Suture
Growth?
Fibrous joints between skull
Skull bone growth in response to brain growth, respond to mechanical stress
Neurocranium
Cranial vault and cranial base = encloses the brain
Viscocranium
Facial skeleton = surrounds oral cavity, pharynx
Simple bone
Formed by ossification fo a single element e.g. endochondral or intramembranous
Compound bone
Formed by fusion of 2 or more ossifying elements e.g. maxilla = 2 intramembranous
Sphenoid = endochondral and intramembranous
When is Meckels cartilage formed?
6 weeks i.u.
Synovial joint
2 bones each covered with particular surface (hyaline cartilage) surrounded by fibrous capsule that creates a joint cavity filled with synovial fluid
TMJ movements
Rotation (horizontal) and translation (forward and backwards)
Fibrous layer covering the condyle contains …
Progenitor cells that form chondrocytes that undergo endochondral ossification
How does cranial base grow?
Remodelling and synchondroses
Growth of what influences the angle of the cranial base?
Spheno-occipital synchondroses
How does cranial vault grow?
Remodelling and sutures
How does maxilla grow in height?
Bone deposition at symptomatic and frontal sutures
vertical drift of alveolar process
Deposition on inferior surface of palate and resorption on superior
Growth of maxilla in width?
Growth at mid palatal suture
Growth of maxilla in length?
Posterior surface of maxillary tuberosity
Forward and downward displacement of mandible results in…
Growth of condylar cartilage
Bone remodelling of ramus
Early enamel formation?
Starts by secretion of enamel proteins, immediately partially mineralised
First layer is a prismatic and formed against mantle dentine. Tomes processes form - proximal = interprismatic, distal = prismatic
Function of amelogenins?
Form nano spheres which surround crystals and prevent them from fusing
Regulates growth and thickness of enamel crystals
Function of non-amelogenins?
Form enamel sheath
Enamelin = promotes and guides formation of enamel crystals
Amelobastin = adhesion of ameloblasts to enamel surfaces
What process can epithelial rest of malassez under go?
Epithelial-mesenchymal transition
How far do odontoblast processes extend in the tubules?
Normally to the EDJ
Increased age/attrition can cause retraction of processes (peritubular, dead tracts)
Some times can overshoot = enamel spindles
Main nerves in the pulp?
Mainly unmyelinated C fibres
Major = afferent (terminate at odontoblasts layers and transmit pain to CNS)
Minor = efferent (cause vasodilation/constriciton of capillaries)
Some myelinated afferent fibres
Equivalent to Contour lines of Owen in enamel?
Wilson lines
What does gnarled enamel look like and how is it caused?
Very angular prism decussation
Ameloblasts adapting to rapidly expanding enamel layer
Cohorts of ameloblasts are displaced apically by their own enamel production
Granular layer of Tomes
Where?
How?
Mineralisation?
Peripheral root dentine, beneath hyaline dentine
Extensive branching and backwards looping of odontoblast processes or incomplete fusion of calcospherites
Hypomineralised
Prism direction in primary and permanent teeth?
Primary = inclined occlusally Permanent = inclined apically
Enamel tuft
Hypomineralised voids from EDJ extending a short distance into enamel following prism decussation, they contain residual enamel proteins
Enamel lamellae
Tufts passing through the full thickness of enamel containing organic material
Keratinisation status of gingival epithelium?
Parakeratinised plus some orthokeratinisation in areas of higher abrasive forces
Keratinisation of sulcular epithelium
Non-keratinised = binds gingival sulcus and may act as epithelial barrier
How is correct depth of sulcular epithelium determined?
Masticatory forces
What is Nasmyths membrane?
Primary enamel cuticle and remnants of REE
What is primary enamel cuticle?
Internal basal lamina produced by cells of REE, attached to enamel
How does junctional epithelium attach to enamel?
Via enamel cuticle and hemidesmosomes
How does structure of JE change in the deepest part compared to upper part?
Deepest part = REE cells (2-3 layers of cuboidal/flat epithelial cells)
Upper part = gingival epithelium cells (multiple layers of cells with epithelial ridges)
Consequence of inflammation on the sulcular epithelium?
Causes the epithelium to form long, irregular rate pegs that project into the lamina proprietary = epithelium hyperplasia . This is to compensate for collagen loss due to chronic inflammation
Why are monkeys gingival and palatal epithelium more orthokeratinxied than human?
Functional adaption - eat tougher food
What is submucosa made of?
Loose connective tissue (Fb), adipose tissue, minor salivary glands, BV and N
Where on the hard palate is submucosa found?
Lateral and posterior regions
Functional significance of epithelial-connective tissue interface?
Interdigitation of rete pegs and papillae of lamina proprietary increase SA and stability of epithelial-mesenchyme surface
Type of collagen in gingiva and palatal mucosa and why
Type 1 = fibrillar = high tensile strength and can resist shearing
When does condyle stop growing? What happens to the condyle cartilage?
16-20
Progenitor cells of proliferative zone stop dividing but cells persist through life. Endochondral ossification stops and condyle cartilage converted to fibrocartilage and highly calcified cartilage
Effect of bite jumping device on condyle
Pulls mandible froward inducing condylar growth
Chondroblasts of proliferative zone reactivated by mechanical stress, differentiate into chondroblasts = endochondral ossficiation
