Post on 07-May-2015
Islam Kassem, BDS , MSc, MOMS RCPS Glasg,
FFD RCSI
Consultant Oral & Maxillofacial Surgeon
Medical Topics in Orthodontics
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Embryonic Development
The construction of an adult from a single cell, the fertilized egg (zygote).
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1. Differentiation
A Single Cell, the Fertilized
Egg, Gives Rise to Hundreds
of Different Cell Types. This
Generation of Cellular Diversity
Is Called Differentiation.
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2. Morphogenesis -- Pattern
Formation
Differentiation is carefully orchestrated. The repertoire includes:
Proliferation
Cell migration
Interactions (Induction)
Epithelial-mesenchymal transformations
Epithelial folding, movement, in- & evagination, fusion
Apoptosis …
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3. Controlled Growth
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Dolly and Bonnie
.
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Homeotic mutation:
Master Regulatory Genes
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Developmental
Regulatory genes are
Transcription factors
Transcription factors or gene regulatory proteins are involved in activating or repressing transcription. TFs act by binding to the control regions of genes or by interacting with other DNA-binding proteins.
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Hedgehog
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Congenital Malformations Causes
– Genetic/chromosomal
– Enviornmental
Incidence – 2-3% of newborn (4-6% by age 5)
– In 40-60% of all birth defects cause is unknown Genetic/chromosomal
– 10%-15%
Environmental – 10%
Multifactorial (genetic & environmental) – 20%-25% ikassem@dr.com
Teratology
Teratology
– Science that studies the causes of abnormal development
– The term is derived from the Greek ―teratos‖ which means monster
– Birth defects is the number one cause of infant mortality
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Terms used in Disease
Sign objective evidence of a disease
Symptom subjective evidence of a disease
Syndrome refers to a set of symptoms & signs which occur together in the morbid (disease) state
Etiology the study of the cause of disease
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Types of Anomalies Malformations
– Occur during formation of structures
Complete or partial absence
Alterations of its normal configuration
Disruptions
– Morphological alterations of structures after formation
Due to destructive processes
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Deformations
– Due to mechanical forces that mold a part of fetus over a prolonged period of time
Clubfeet due to compression in the amniotic cavity
Often involve the musculoskeletal system & may be reversible postnatally
Syndromes
– Group of anomalies occuring together with a specific common etiology
Diagnosis made & risk of recurrence is known
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Environmental factors
Infectious agents
Radiation
Chemical Agents
Hormones
Maternal Disease
Nutritional Deficiencies
Hypoxia
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Infectious Agents Rubella (German Measles)
– Malformations of the eye
Cataract (6th week)
Microphthalmia
– Malformations of the ear (9th week)
Congenital deafness
– Due to destruction of cochlea
– Malformations of the heart (5th -10th week)
Patent ductus arteriosis
Atrial septal defects
Ventricular septal defects
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Cytomegalovirus – Disease is often fatal early on
– Malformations Microcephaly
– Cerebral calcifications
– Blindness Chorioretinitis
– Kernicterus (a form of jaundice)
– multiple petechiae of skin
– Hepatosplenomegaly
– Mother asymptomatic
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Herpes Simplex Virus – Intrauterine infection of fetus occasionally occurs
– Usually infection is transmitted close to time of delivery
– Abnormalities (rare) Microcephaly
Microphthalmos
Retinal dysplasia
Hepatosplenomegaly
Mental retardation
– Usually child infected by mother at birth Inflammatory reactions during first few weeks
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Varicella (chickenpox) – Congenital anomalies
20% incidence following infection in 1st trimester
Limb hypoplasia
Mental retardation
Muscle atrophy
HIV/AIDS – Microcephaly
– Growth retardation
– Abnormal facies (expression or appearance of the face)
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Toxoplamosis – Protozoa parasite (Toxoplama gondii)
Sources – Poorly cooked meat
– Domestic animals (cats)
– Contaminated soil with feces
Syphilis – Congenital deafness
– Mental retardation
– Diffuse fibrosis of organs (eg. liver & lungs)
In general most infections are pyrogenic – Hyperthemia can be teratogenic
Fever
Hot tubs & Saunas
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Radiation Teratogenic effect of ionizing radiation
well established – Microcephaly
– Skull defects
– Spina bifida
– Blindness cleft palate
– Extremity defects
Direct effects on fetus or indirect effects on germ cells
May effect succeeding generations
Avoid X-raying pregnant women ikassem@dr.com
Chemical agents/Drugs
Role of chemical agents & drugs in production of anomalies is difficult to assess – Most studies are retrospective
Relying on mother’s memory
– Large # of pharmaceutical drugs used by pregnant women NIH study – 900 drugs taken by pregnant women
– Average of 4/woman during pregnancy
– Only 20% of women use no drugs during pregnancy
– Very few drugs have been positively identified as being teratogenic
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Drugs
Thalidomide
– Antinauseant & sleeping pill
– Found to cause amelia & meromelia
Total or partial absence of the extremities
– Intestinal atresia
– Cardiac abnormalities
– Many women had taken thalidomide early in pregnancy (in Germany in 1961)
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Anticonvulsants (to treat epilepsy)
– Diphenylhydantoin (phenytoin)
Craniofacial defects
Nail & digital hypoplasia
Growth abnormalities
Mental deficiency
The above pattern is know as ―fetal hydantoin syndrome‖
– Valproic acid
Neural tube defects
Heart defects
Craniofacial & limb anomalies ikassem@dr.com
Antipsychotic drugs (major tranquilizers)
– Phenothiazine & lithium
Suspected teratogenic agents
Antianxiety drugs (minor tranquilizers)
– Meprobamate, chlordiazepoxide,
Severe anomalies in 11-12% of offspring where mothers were treated with the above compared to 2.6% of controls
– diazepam (valium)
Fourfold in cleft lip with or without cleft palate
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Anticoagulants – Warfarin (A.K.A cumadin or cumarol)
Teratogenic
Hypoplasia of nasal cartilage
Chondrodysplasia
Central nervous system defects – Mental retardation
– Atrophy of the optic nerves
Antihypertensive agents – angiotensin converting enzyme (ACE) inhibitor
Growth dysfunction, renal dysfunction, oliogohydramnios, fetal death
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Isotretinoin (13-cis-retinoic acid) – Analogue of vitamin A
– Drug is prescribed for treatment of cystic acne & other chronic dermatoses
– Highly tertogenic Reduced & abnormal ear development
Flat nasal bridge
Cleft palate
Hydrocephaly
Neural tube defects
Heart anomalies
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Recreational drugs
PCP angel dust – Possible malformations & behavioral
disturbances
Cocaine-vasoconstrictor hypoxia – Spontaneous abortion
– Growth retardation
– Microcephaly
– Behavioral problems
– Urogenital anomalies
– gastroschisis
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Alcohol Relationship between alcohol consumption
& congenital abnormalities
Fetal alcohol syndrome – Craniofacial abnormalities
Short palpebral fissures
Hypoplasia of the maxilla
– Limb deformities Altered joint mobility & position
– Cardiovascular defects Ventricular septal abnormalites
– Mental retardation
– Growth deficiency
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Cigarette Smoking
Has not been linked to major birth defects
– Smoking does contribute to intrauterine growth retardation & premature delivery
– Some evidence that is causes behavioral disturbances
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Maternal Disease Disturbances in CHO metabolism (diabetic
mothers) – High incidence of stillbirth, neonatal deaths
– Abnormally large infants
– Congenital malformations risk 3-4X
Cardiac, Skeletal, CNS Anomalies
Caudal dysgensis – Partial or complete agenesis of sacral vertebrae in
conjuction with hindlimb hypoplasia
– Hypoglycemic episodes teratogenic (why?)
– Oral hypoglycemic agents maybe teratogenic
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Hypoxia
Associated with congenital malformations in a great variety of experimental animals
– In humans ???
Maybe smaller babies e.g. offspring at high altitude
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Environmental Chemicals
Mercury
– Fish, seed corn sprayed with mercury containing fungicide
Multiple neurological symptoms
Lead
– abortions
– Growth retardation
– Neurological disorders
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Prevention of birth defects
Good prenatal care
Iodine supplementation eliminates mental retardation & bone deformities
– Prevent cretinism
Folate/Folic Acid supplementation
– incidence of neural tube defects
Avoidance of alcohol & other drugs during all stages of pregnancy
– incidence of birth defects ikassem@dr.com
Chromosomal & Genetic Factors
Numerical Abnormalities
– Trisomy 21 (Down syndrome)
– Trisomy 18
– Trisomy 13
– Klinefelter Syndrome
– Turner Syndrome
– Triple X Syndrome
Structural Abnormalities
Mutant Genes ikassem@dr.com
Chromosomal Abnormalities May be numerical or structural
Important causes of congenital malformations & spontaneous abortions
Estimated that 50% of all conceptions end in spontaneous abortion & 50% of these have major chromosome abnormalities
Most common chromosome abnormalities in aborted fetuses is: – Turner syndrome (45,X)
– triploidy
– trisomy 16 ikassem@dr.com
Numerical Abnormalities
Normal gametes are haploid (n =23)
Normal human somatic cell contains 46 chromosomes; Diploid (2n = 46)
Euploid-Exact multiple of n
Aneuploid-Any chromosome # that is noneuploid
– Additional chromosome
– Missing chromosome
Most common cause is nondisjunction during either meiosis to mitosis
– Risk of meiotic nondisjunction with maternal age
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Structural Abnormalities
May involve one or more chromosomes
Usually result from chromosome breakage – Broken piece may be lost
Partial deletion of chromosome 5 – Cri-du-chat (cry of the cat)
Microcephaly
Mental retardation
Congenital heart disease
Many other relatively rare syndromes result from a partial chromosome loss
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Mutant Genes
Many congenital malformations are inherited – Some show a clear mendelian pattern of
inheritance
– In many cases abnormality is attributed to a change in the structure or function of a single gene. ―single gene mutation‖
– Estimated that this type of defect makes up about 8% of all human malformations
– Dominant vs. recessive vs. X-linked (also recessive)
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Orofacial Embryology
Prenatal Development
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Head formation
rostral or head fold anterior portion of the neural tube
expands as the forebrain, midbrain and hindbrain
the neuroectoderm in this region will form the olfactory, orbital and otic placodes
the hindbrain forms 8 bulges = rhombomeres
the paraxial mesoderm in this region also segments into somites
migration of neural crest cells into this region provides the embryonic connective tissue (mesenchyme) required for development of the craniofacial structures
these neural crest cells arise from the midbrain and the first two rhombomeres as two streams
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Branchial arches
also called pharyngeal arches figure 4-11 fourth week: development of a
frontal prominence forms the stomatodeum
below this is the formation of the first branchial arch (mandibular arch)
6 pairs – U shaped – core of mesenchymal tissue
formed from neural crest cells that migrate in to form the arches
– covered externally by ectoderm and lined internally by endoderm
– each has its own developing cartilage, nerve, vascular and muscular components
these arches separate the stomatodeum from the developing heart
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Branchial arches separated laterally by branchial grooves/clefts
medially they are separated by pharyngeal pouches first arch (mandibular arch) – maxillary and mandibular
processes second arch (hyoid arch) - hyoid bone, part of the temporal bone
(VII nerve) cartilage = Reichert’s cartilage the mesoderm of this arch will form the muscles of facial expression, the
middle ear muscles
third arch –tongue (IX nerve) fourth arch –tongue, most of the laryngeal cartilages (IX and X
nerves) fifth arch – becomes incorporated into the fourth sixth arch – most of the laryngeal cartilages (IX and X nerves)
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Pharyngeal Pouches
– four well-defined pairs of pharyngeal pouches develop from the lateral walls of the pharynx
– first pouch (betwen the 1st and 2nd arches) - external acoustic meatus, tympanic membrane, and eustachian tube
– second pouch – palatine tonsils
– third pouch - thyroid and parathyroid glands,
– fourth pouch – parathryoid gland
– fifth pouch -becomes incorporated into the fourth
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Development of the Face
forms from the fusion of 5 face primordia which develop during week 4 and fuse during weeks 5 through 8 – primordia = ectodermal swellings or
prominences that are filled with mesodermal and neural crest cells frontonasal prominence
mandibular prominences (2) – from branchial arch #1
maxillary prominences (2) – from branchial arch #1
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Development of the Face
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Stomatodeum
primitive stomatodeum forms a wide shallow depression in the face – limited in its depth by the buccopharyngeal membrane
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Upper lip formation
during the fourth week
fusion of the maxillary processes with each medial nasal process
this contributes to the lateral sides of the upper lip – together with the medial nasal processes which contribute to the medial aspect of the upper lip
the maxillary processes also fuse with the lateral nasal processes – results in a nasolacrimal groove which extends from the medial corner of the eye to the nasal cavity
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Development of the Palate involves the formation of a
primary palate, a secondary palate and fusion of their processes
Primary palate
– forms from an internal swelling of the intermaxillary/premaxillary process (fusion of medial nasal processes)
Secondary palate
– forms from the two lateral palatine shelves or processes
– develop as internal projections of the maxillary prominences
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Primary palate fusion of the
median nasal processes gives rise to the median palatine process – fuses to form the primary palate
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Secondary Palate
the common oronasal cavity is bounded anteriorly by the primary palate and occupied by the developing tongue
only after the development of the secondary palate can oral and nasal cavities by distinguished
three outgrowth appear in the oral cavity – nasal septum:
grows downward through the oral cavity
it encounters the primary and secondary palates
– two palatine shelves
closure of the secondary palate is likely to involve the hardening of the palatine shelves – mechanism remains unknown + the withdrawl of the tongue
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Maxilla formation
centers of ossification develop in the mesenchyme of the maxillary processes of the first branchial arch
spreads posteriorly below the orbit towards the developing zygoma and anteriorly toward the future incisor region and superiorly to form the frontal process
ossification also spreads into the palatine process to form the hard palate
at the union between the palatal process and the main body of the developing maxilla is the medial alveolar plate – together with the lateral plates – development of the maxillary teeth
a zygomatic or malar cartilage appears in the developing zygomatic processes and contributes to the development of the maxilla
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Mandible formation the cartilage of the first branchial arch
associated with the formation of the mandible = Meckel’s cartilage
6 weeks: Meckel’s cartilage forms a rod surrounded by a fibrocellular capsule
the two cartilages do not meet at the midline but are separated by a thin line of cartilage = symphysis
on the lateral aspect of this symphysis – a condensation of mesenchyme forms
at 7 weeks intramembranous ossification begins in this mesenchyme and spreads anteriorly and posteriorly to form the bone of the mandible
the bone spreads anteriorly to the midline of the developing lower jaw – the bones do not fuse at the midline – mandibular symphysis forms (from meckel’s cartilage)
– which fuses shortly after birth
the ramus develops from rapid ossification posteriorly into the mesenchyme of the first arch
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Mandible formation
-Meckel’s cartilage does NOT contribute directly to the ossification of the mandible
-posterior extremity – malleolus of the inner ear -portion persists as the sphenomandibular ligament -significant portion is resorbed entirely -most anterior portion near the midline may contribute to the jaw
through endochondral ossification -growth of the mandible until birth is influences by the appearance of
three secondary (growth) cartilages 1. condylar – 12th week, developing ramus by endochondral
ossification, a thick layer persists at birth at the condylar head (mechanism for post-natal growth of the ramus = endochondral)
2. coronoid – 4 months, disappears before birth 3. symphyseal – appears in the connective tissue at the ends of the
Meckel’s cartilage, gone after 1 year after birth
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Development of the Tongue begins to develop about 4 weeks localized proliferation of the
mesenchyme results in formation of several swellings in the floor of the oral cavity
the oral part (anterior two-thirds) develops from the fusion of two distal tongue buds or lateral lingual swellings and a median tongue bud (tuberculum impar)
the pharyngeal part or root of the tongue (posterior one-third) develops from the copula and the hypobranchial eminence (forms from the 2nd, 3rd and 4th branchial arches)
these parts fuse (adult = terminal sulcus)
muscles of the tongue arise from occipital somites which migrate into the tongue area
hypobranchial arch overgrows the 2nd arch
B.As #1,2 and 3
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There are many developmental abnormalities that can affect the teeth and facial skeleton. In most cases, clinicians need little more than to be able to recognize these abnormalities
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Classification of developmental abnormalities
1-Anomalies of the teeth
2-Skeletal anomalies.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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1-Abnormalities in number
Missing teeth
Additional teeth (hyperdontia)
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Missing teeth
• Localized anodontia or hypodontia — usually third molars, upper lateral incisors or second premolars.
• Anodontia or hypodontia associated with
systemic disease — e.g. Down's syndrome,
ectodermal dysplasia.
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Additional teeth (hyperdontia)
• Localized hyperdontia — Supernumerary teeth
— Supplemental teeth
• Hyperdontia associated with specific
syndromes, e.g. cleidocranial dysplasia,
Gardener's syndrome.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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2-Abnormalities in structure
Genetic defects
Acquired defects
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Genetic defects
• Amelogenesis imperfecta — Hypoplastic type
— Hypocalcified type
— Hypomature type
• Dentinogenesis imperfecta
• Shell teeth
• Regional odontodysplasia (ghost teeth)
• Dentinal dysplasia (rootless teeth).
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Acquired defects
• Turner teeth — enamel defects caused by infection from overlying deciduous predecessor • Congenital syphilis — enamel hypoplastic and altered in shape (see below) • Severe childhood fevers, e.g. measles — linear enamel defects Fluorosis — discolouration or pitting of the enamel • Discolouration — e.g. tetracycline staining.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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3-Abnormalities in size
• Macrodontia — large teeth
• Microdontia — small teeth, including
rudimentary teeth.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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4-Abnormalities in shape
Anomalies affecting -whole teeth
Anomalies affecting the crowns
Anomalies affecting roots andlor pulp canals
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Anomalies affecting -whole teeth
• Fusion — two teeth joined together from the fusion of adjacent tooth germs • Gemination — two teeth joined together but arising from a single tooth germ • Concrescence — two teeth joined together by cementum • Dens-in-dente (invaginated odontome) — in folding of the outer surface of a tooth into the interior usually in the cingulum pit region of maxillary lateral incisors.
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Anomalies affecting the crowns
• Extra cusps • Congenital syphilis — Hutchinson 's incisors — crowns small, screwdriver or barrel-shaped, and often notched — Moon's/mulberry molars — dome-shaped or modular • Tapering pointed incisors — ectodermal dysplasia.
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Anomalies affecting roots and or pulp canals
• Number — additional roots, e.g. two-rooted incisors, three-rooted premolars or four-rooted molars • Morphology, including: — Bifid roots — Excessively curved roots — Dilaceration — sharp bend in the root direction — Taurodontism — short, stumpy roots and longitudinally enlarged pulp chambers Pulp stones — localized or associated with specific syndromes, e.g. Ehlers-Danlos (floppy joint syndrome).
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Odontomes
• Enameloma/enamel pearl • Cementoma (see fibro-cemento-osseousmesions in — Benign cementoblastoma (true cementoma) — Periapical cemento-osseous dysplasia — Focal cemento-osseous dysplasia — Florid cemento-osseous dysplasia (gigantiform cementoma) • Composite — Compound odontome — made up of one or more small tooth-like denticles — Complex odontome — complex mass of disorganized dental tissue.
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Anomalies of the teeth
1-Number
2-Structure
3-Size
4-Shape
5-Position.
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5-Abnormalities in position
Delayed eruption
Other positional anomalies
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Delayed eruption
• Local causes — Loss of space — Abnormal crypt position — especially 8/8 and 3/3 — Overcrowding — Additional teeth — Retention of deciduous predecessor — Dentigerous and eruption cysts • Systemic causes — Metabolic diseases, e.g. cretinism and rickets — Developmental disturbances, e.g. cleidocranial dysplasia — Hereditary conditions, e.g. gingival fibromatosis and cherubism.
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Other positional anomalies
• Transposition two teeth occupying exchanged positions
• Wandering teeth, movement of unerupted
teeth for no apparent reason (distal drift)
• Submersion, second deciduous molars apparently descend into the jaws. Since these teeth do not in fact submerge, but rather remain in their original position while the adjacent Other positional anomalies
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Skeletal anomalies
• Abnormalities of the mandible and/or maxilla
• Other rare developmental diseases and
syndromes.
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Abnormalities of the mandible or maxilla
Micrognathia
Macrognathia (prognathism)
Other mandibular anomalies
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Micrognathia
• True micrognathia — usually caused by bilateral
hypoplasia of the jaw or agenesis of the condyles
• Acquired micrognathia — usually caused by unilateral early ankylosis of the temporomandibular joint.
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Macrognathia (prognathism)
• Genetic
• Relative prognathism — mandibular/maxillary
disparity
• Acquired, e.g. acromegaly owing to excessive
growth hormone from a pituitary tumour.
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Other mandibular anomalies
• Condylar hypoplasia
• Condylar hyperplasia
• Bifid condyle
• Coronoid hyperplasia.
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Cleft lip and palate
• Cleft lip — Unilateral, with or without alveolar ridge — Bilateral, with or without alveolar ridge • Cleft palate — Bifid uvula — Soft palate only — Soft and hard palate • Clefts of lip and palate (combined defects) — Unilateral (left or right) — Cleft palate with bilateral cleft lip.
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Alveolar cleft
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Localized bone defects
• Exostoses
— Torus palatinus
— Torus mandibularis
• Idiopathic bone cavities
— Stafne's bone cavity.
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Eagle’s syndrome
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Other rare developmental diseases and syndromes
• Cleidocranial dysplasia
• Gorlin's syndrome (nevoid basal cell
carcinoma syndrome)
• Eagle syndrome
• Crouzon syndrome (craniofacial dysostosis)
• Apert syndrome
• Mandibular facial dysostosis (Treacher Collins
syndrome).
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Tooth Development
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Stages of tooth development
1. Bud stage
2. Cap stage
3. Bell stage
4. Appositional stage (mineralization)
5. Root formation
6. Eruption
(epithelial ingrowth into ectomesenchyme)
(further epithelial growth)
(histo- and morpho-differentiation)
(formation of enamel and dentin of crown)
(formation of dentin and cementum of root)
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Bud stage
1
2
3
4
5
1. oral epithelium 2. dental lamina 3. tooth bud 4. ectomesenchymal cells 5. vestibular lamina
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Cap stage
1. Enamel organ (=dental organ)
2. Dental papilla
3. Dental sac (=dental follicle) 1
2
3
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Enamel organ of cap stage
2 1
3
1) Inner enamel ep 2) Outer enamel ep 3) Cervical loop 4) Stellate reticulum 5) Enamel knot 6) Enamel cord 7) Enamel navel
4
5
6
7
transient structure during cap stage
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Bell stage
1. outer enamel ep.
2. inner enamel ep.
3. stellate reticulum
4. stratum intermedium
3
2
1 4
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Appositional stage
1. oral ep.
2. outer enamel ep.
3. stellate reticulum
4. inner enamel ep.
5. dental papilla
6. cervical loop
3
2
1
5
4
6
blood vessels
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a. predentin b. dentin c. enamel 1. ameloblasts 2. preameloblasts 3. odontoblasts 4. preodontoblasts 5. dental papilla 6. stratum intermedium
4
2
6
a
3
1 b
c
5
Appositional stage
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Appositional stage
(alkaline phosphatase )
dentino- enamel
junction
(collagen fibers of mantle dentin)
Aprismatic
Mantle
odontoblasts
(predentin)
Reduced stellate reticulum
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Formation of roots Hertwig epithelial root sheath
(HERS)
- Apical extension of cervical loop
- Inner+outer enamel ep.
- Not making enamel
- Framework of root formation
root sheath epithelial diaphragm
(size/shape/number of roots)
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Periodontal tissues
oral ep
Periodontal ligament
Alveolar bone
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Tooth eruption
1 mm
4
1
2
3
5
6
1. oral ep. 2. connective tissue 3. alveolar bone 4. Enamel 5. Dentin 6. HERS
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Tooth eruption
1 mm
• Axial movement toward oral epithelium begin when the root formation begin. • Source of erupting force : contraction of fibroblasts generating periodontal ligaments?
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Tooth eruption
reduced enamel ep.
osteoclasts
fused with oral ep.
form junctional ep.
Alveolar bone and connective tissue are resorbed as teeth erupt.
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Periodontal tissues
Junctional ep
oral ep
Periodontal ligament
Alveolar bone
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Relationship of primary teeth and succedaneous permanent teeth
s
open apex resorption of root erupting erupting
D : deciduous tooth P or S : succedaneous tooth
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Summary of tooth development
Oral epithelium
Dental lamina
ameloblasts Inner enamel ep
Stellate reticulum
Stratum intermedium
Outer enamel ep HERS
Ectomesenchyme
Dental sac
Dental papilla odontoblasts
cementoblasts
fibroblasts
fibroblasts
osteoblasts
dentin
cementum
pulp
periodontal ligament
alveolar bone
enamel
guide root formation
oral epithelium
reduced enamel ep junctional ep.
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Most odontogenic epithelial cells degenerate following the completion of tooth formation
Oral epithelium
Dental lamina
ameloblasts Inner enamel ep
Stellate reticulum
Stratum intermedium
Outer enamel ep HERS
Ectomesenchyme
Dental sac
Dental papilla odontoblasts
cementoblasts
fibroblasts
fibroblasts
osteoblasts
dentin
cementum
pulp
periodontal ligament
alveolar bone
enamel
guide root formation
oral epithelium
junctional ep. reduced enamel ep.
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Molecular mechanism of tooth development
Many genes control tooth development but not completely understood – shape, number of cusp (incisor vs molar)
– size
– number (2 vs 3 molars…..)
– location (mesio-distal, maxillo-mandibular….)
– timing of formation and eruption
Future of dentistry? – Control the number and location of teeth
– In vitro formation of tooth
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Most common craniofacial malformation
Cleft lip with or without cleft palate (CL/P) or isolated cleft palate (CP).
CL/P and CP differ with respect to
– Embryology, etiology, candidate genes, associated abnormalities, and recurrence risk.
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Unilateral incomplete
Unilateral complete
Bilateral complete
Incomplete cleft palate
Unilateral complete lip and
palate
Bilateral complete
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Prevalence
CL/P is more common than CP and varies by ethnicity.
CL/P – High in American Indians and Asians (1/500
newborns)
– Low in American blacks (1/2000 newborns)
– Intermediate level in Caucasians (1/1000 newborns)
Isolated CP occurs in only 1/2500 newborns and does not display variation by ethnicity.
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Cleft Lip
Complete closure at 35 days postconception:
– 7 weeks from the LMP.
– Lateral nasal, median nasal, and maxillary mesodermal processes merge.
Failure of closure can produce unilateral, bilateral, or median lip clefting.
Left side unilateral cleft is the most common.
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Cleft lip Severity
Mild, involving only the lip
Extend into the palate and midface thereby affecting the nose, forehead, eyes, and brain.
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Cleft Palate
Lack of fusion of the palatal shelves.
Abnormalities in programmed cell death may contribute to lack of palatal fusion(?).
Isolated disruption of palate shelves can occur after closure of the lip
Palatal closure is not completed until 9 weeks post-conception.
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Environmental agents
Several agents that are associated with an increased frequency of midfacial malformation.
Medications —phenytoin, sodium valproate, methotrexate.
With corticosteroids there is no evidence of an increase in malformations.
– Possible association could not be excluded
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Prenatal Diagnosis
Diagnosed until the soft tissues of the fetal face can be clearly visualized sonographically (13 to 14 weeks).
The majority of infants with cleft lip also have palatal involvement: – 85% of bilateral cleft lips
– 70% associated with cleft palate.
– Cleft palate with an intact lip comprises 27% of isolated CL/P
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Prenatal Diagnosis
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Syndrome ?
A thorough examination of the newborn or stillbirth is always warranted.
Orofacial clefting is noted in over 300 syndromes.
3 deserve additional comment.
– frequency, variable presentations, and modes of inheritance
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Deletion of chromosome 22q11
DeGeorge syndrome.
Spectrum in addition to cleft palate:
– Conotruncal cardiac defects, thymic hypoplasia, and velopharyngeal webs.
Majority of cases represent a new microdeletion
In families with conotruncal malformations and/or CP, further evaluation is appropriate.
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Oral-facial-digital syndrome, type I
X-linked dominant syndromes.
Manifestations in affected females are variable and subtle:
– hyperplastic frenula
– cleft tongue
– cleft lip/palate
– digital anomalies
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Treacher-Collins syndrome
Autosomal dominant disorder
Downward slanting palpebral fissures, micrognathia, dysplastic ears, and deafness.
– Mental development is normal.
The mutations appear to increase cell death in the prefusion neural folds.
A family history with deafness, ear abnormalities, or CP.
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Obstetrical Management
Amniocentesis for karyotype should be offered. – high rate of chromosomal defects
Difficulty in prenatal sonographic diagnosis supports chromosomal evaluation
As of January 2002, "in utero" correction had been attempted only once in Mexico – The child delivered prematurely and died at
two months of life
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Feedings
Infants with CL/P have few feeding problems.
If the cleft involves the hard palate, the infant is usually not able to suck efficiently.
– Experiment (special nipples or alternate feeding positions)
The infant should be held in a nearly sitting position during feeding
– Prevents flowing to the back into the nose.
Should be burped frequently, (q 3-4min).
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Feedings
It is important to keep the cleft clean
Breastfeeding is
extremely challenging.
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Haberman Feeder
Activated by tongue and gum pressure.
Milk cannot flow back. Replenished continuously
as the baby feeds. Prevents the baby from
being overwhelmed with milk.
A gentle pumping action to the body of the nipple will increase flow.
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More than 3,000 syndromes classified Optimal growth, development, and learning requires
early recognition and intervention Team Approach:
– Parents – Pediatrician – Otolaryngologist – Cardiologist – Nephrologist – Geneticist – Speech Therapist – Teachers – Others
The Sydromal
Child
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The Sydromal
Child
History
– Parental factors (age)
– Consanguinity
– Abortions
– Teratogen exposure
– Medical Pedigree
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Physical Exam
– Major and Minor Anomalies
Airway
Skull
Ears
Facial skeleton
– Comparison to Family Members
– Reference Material
The Sydromal
Child
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Down Syndrome
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Described by John Landon Down in 1866
Etiology: nondisjuction mutation resulting in Trisomy 21
Prevalence 1:700
– Most common chromosomal anomaly
Associated with Maternal age > 35
Down
Syndrome
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Facial Characteristics – Macroglossia
– Micrognathia
– Midface hypoplasia
– Flat occiput
– Flat nasal bridge
– Epicanthal folds
– Up-slanting palpebral fissures
– Progressive enlargement of lips
Down
Syndrome
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Down
Syndrome
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Airway Concerns
– Due to midface hypoplasia, the nasopharynx and oropharynx dimensions are smaller
Slight adenoid hypertrophy can cause upper airway obstruction
– Congenital mild-moderate subglottic narrowing not uncommon
Post-extubation stridor
Down
Syndrome
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Obstructive Sleep Apnea
– Prevalence 54-100% in DS patients
– Combination of anatomic and functional mechanisms
Midface hypoplasia, macroglossia, etc
Hypotonia of pharyngeal muscles
Down
Syndrome
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Obstructive Sleep Apnea
– Management:
Polysomnography to confirm
Medical interventions:
– CPAP
– Weight Loss
– Medications to stimulate respiratory drive
Down
Syndrome
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Obstructive Sleep Apnea
– Management:
Surgical
– Adenoidectomy and Tonsillectomy
Controversial
– UPPP
– Partial tongue resection
– Tracheotomy
Down
Syndrome
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Otologic Concerns
– Small pinna, Stenotic EAC
Cerumen impaction
– CHL
ETD: PE tubes
Ossicular fixation: surgical correction
– SNHL
Progressive ossification along outflow pathway of basal spiral tract
Down
Syndrome
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Cardiovascular anomalies (40%)
– ASD, VSD, Tetralogy of Fallot, PDA
GI anomalies (10-18%)
– Pyloric stenosis, duodenal atresia, TE fistula
Malignancy
– 20 fold higher incidence of ALL
– Gonadal tumors
Down
Syndrome
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Treacher
Collins
Syndrome
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TCS
First described by Thomson and Toynbee in 1846-7 – Later, essential components described by Treacher
Collins in 1960
Autosomal dominant inheritance – TCOF1, mapped to 5q32-33.1
60% are from new mutation – Associated with increased paternal age
Prevalence of 1 in 50,000
a.k.a. Mandibulofacial dysostosis ikassem@dr.com
TCS
Characteristics – Likely due to abnormal migration of neural crest cells into
first and second branchial arch structures – Usually bilateral and symmetric – Malar and supraorbital hypoplasia – Non-fused zygomatic arches – Cleft palate in 35% – Hypoplastic paranasal sinuses – Downward slanting palpebral fissures – Mandibular hypoplasia with increased angulation – Coloboma of lower eyelid with absent cilia – Malformed pinna – Normal intelligence
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TCS
OP/Airway concerns
– Cleft palate
– Choanal atresia may be present
Respiratory distress in newborn
Oral airway, McGovern nipple
– Obstructive sleep apnea is the most common airway dysfunction
Mandibular hypoplasia results in retrodisplacement of tongue into oropharynx
Oral airway, tracheotomy
Distraction osteogenesis vs. free fibular transfer
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TCS
Otologic concerns
– Malpositioned auricles
– Malformed pinna
– EAC atresia
– Ossicular abnormalities
– Conductive hearing loss is common
Hearing aids are effective
– Normal intelligence
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TCS
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TCS
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Apert and
Crouzon
Syndromes
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Apert and
Crouzon
Belong to family of Craniosynostoses Apert Syndrome (Acrocephalosyndactyly)
– First described by Wheaton in 1894 – Apert further expanded in 1906
Crouzon Syndrome (Craniofacial Dysostosis) – Described by Crouzon in 1912
Autosomal dominant inheritance – Most are sporadic in Apert Syndrome – 1/3 are sporadic in Crouzon Sydrome
Prevalence: 15 - 16 per 1,000,000
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Apert and
Crouzon
Typical characteristics
– Craniosynostosis
Coronal sutures fused at birth
Larger than average head circumference at birth
– Midfacial malformation and hypoplasia
– Shallow orbits with exophthalmos
– Apert Syndrome: symmetric syndactyly of hands and feet
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Apert and
Crouzon
Crouzon and Apert Syndromes facial features
– Shallow orbits with exophthalmos
– Retruded midface with relative prognathism
– Beaked nose
– Hypertelorism
– Downward slanting palpebral fissures
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Apert and
Crouzon
Airway concerns – Reduced nasopharyngeal dimensions and choanal
stenosis
– OSA
– Cor pulmonale
Polysomnography
Treatment – Adenoidectomy
– Endotracheal intubation
– Tracheotomy
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Apert and
Crouzon
Otologic concerns – CHL resulting from ETD
– Congenital fixation of stapes footplate in Apert syndrome
Treatment – Ventilation tubes
– Stapedectomy or OCR
Fronto-Orbital advancement – Brain growth and expansion of cranial vault, orbital depth
Orthodontics – Maxillary teeth abnormalities
– Crossbite
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Pierre Robin
Sequence
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PRS
Triad of micrognathia, glossoptosis and cleft palate – First described by St. Hilaire in 1822
– Pierre Robin first recognized the association of micrognathia and glossoptosis in 1923
Prevalence: 1 of every 8,500 newborns – Syndromic 80%
Treacher Collins Syndrome
Velocardiofacial Syndrome
Fetal Alcohol Syndrome
– Nonsyndromic 20%
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PRS
Mandibular Deficiency
Hypoplastic and Retruded Mandible (Micrognathia)
Tongue Remains Retruded and High in Oropharynx (Glossoptosis)
Failure of Fusion of Lateral Palatal Shelves
Cleft Palate
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PRS
Airway Obstruction
– Anatomic and Neuromuscular Components
Micrognathia, Retruded Mandible
Glossoptosis
Impaired Genioglossus and Parapharyngeal Muscles
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PRS
Airway Management
– Temporizing Modalities
Prone Positioning
Nasopharyngeal Airway
– NG tube and gavage feeds
Mandibular Traction Devices
Tongue Lip Adhesion
– Tracheotomy
– Distraction Osteogenesis
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My Contact
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You can ge the lectures form
http://www.slideshare.net/islamkassem/newsfeed
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