AUTOSOMAL DISORDERS

GENETICS IN PEDIATRIC DENTISTRYCommon chromosomal Syndromesin ChildrenSyndromeDown'ssyndromeEtiologyTrisomy of21st chromosomeCraniofacial features Flat face

Large anterior fontanelle

Open sutures

Small slanting eyes withepicanthal folds

Open mouth

Frequent prognathism

Macroglossia

Fissured or pebbley tongue

High arched palate

Malformed teeth

Decreased cariesOther features Sexual underdevelopment

Cardiac abnormalities

Hypermobility of joints

Mentally retarded

SyndromeKlinefeltersyndromeEtiologyExtra Xchromosomein malesCraniofacial featuresTaurodontism

Other featuresRelatively short limbsSyndromeTurner's syndromeEtiologyMissing XchromosomeCraniofacial featuresHeart-shaped facies

Prominent ears

Webbing of posterior neck

Low posterior hairline

Other features Congenital lymphedema

Broad chest

HypogonadismAUTOSOMAL DISORDERS

Autosomal dominant disordersAutosomal recessive disordersAutosomal dominant disordersarise due to defect in atleast one gene out of a pair of genes on autosomes.

Features

Disease usually appears in each generation Delayed age of onset Vertically transmitted Affected individual has an affected parent Male and female siblings are equally affected Capability of transmission is same in both the affected parents

Examples

Osteogenesis imperfecta, mesiodens, Hypocalcified type I Hereditary Dentinogenesis imperfecta,Dentin dysplasia (Radicular type), Apert's syndromeAutosomal recessive disordersoccur when both thegenes on autosomes are affected. Features

The illness usually appears suddenly in the family Males and females are equally affected Early age of onset Most of the offsprings are normal in the family An affected offspring mayor may not have an affected parentExamples

Dentin dysplasia (coronal type), hereditary amelogenesis imperfecta (hypocalcified type II), hypoPhosphatasia,Hurler's syndrome

Genetic CounsellingA genetic counselor must have:I. Precise and fully confirmed diagnosis of the disease2. Accurate pedigree of the family3. Knowledge of the mode of inheritance of the conditionINDICATIONS FOR PRENATAL DIAGNOSIS

I. Advanced maternal age (e.g., Down's syndrome)2. Previous child with chromosome aberration3. Congenital anomaly4. Structural anomalies found on ultrasonography5. Person with mental retardation or developmental delay

PROCEDURES FOR PRENATAL DIAGNOSISVisualization of Fetus

Ultrasonography: With this technique it is now possibleto visualize the embryo as early as 51/2 to 6 weeks of pregnancy and cardiac activity is detectable at 7-8weeks.Radiography can also be done2. Analysis of Fetal Tissue

AmniocentesisChorionic villus samplingAmniocentesis (Optimum time: 16-18 weeks of gestation):

Under strict aseptic conditions and localanesthesia, 20-30 ml of fluid is aspirated.

About 90% of all amniocentesis are performed for cytogeneticanalysis. The rest 10% is used for biochemicalinvestigation.

The fibroblast-like cells obtained atAmniocentesis. A minimum of 15 cells are examinedand the modal chromosome number is established.Sex determination of fetus is 99% accurate by thismethod.Chorionic villus sampling (optimal time 9-12 weeks)10-25 mg of chorionic villi iscollected. Because the Langerhans cells of the cytotrophoblastare in dividing phase, it is possible to performa "direct" chromosome analysis, immediately after sampling,or alternately after 24 hours of incubation in atissue culture medium. OTHER TESTSFetal and maternal blood analysis non-invasive prenatal diagnosis.

Fetal liver biopsyFetal skin biopsyGENETICS IN PREVENTION OF DENTALCARIESGenetic Engineering in Dental Caries

S mutans has been genetically modified, lacking the specific gene codes for theenzymes necessary to produce decay. These modifiedstrains are being incorporated in daily use eatables likeapple, milk, yoghurt.Recent Discoveries

1. Recently a vaccine has been discovered, a protein called p1025. This protein tricks S mutans leaving no vacant sites for its attachment on tooth.

2. Robert Buine (2000) had developed strains of S mutans that are endowed with a gene to increase production of urease which creates basic conditions conducive to remineralisation.

3. Replacement Therapy: A harmless effector strain is permanently implanted in the host's microflora.

Biomimetic Materials

Genetically engineered materials are under the trialwhich may mimic the nature of tooth substance and helpto regenerate the dental tissue. STEM CELLSTwo properties which must be satisfied for a cell to bedefined as a stem cell are:

Self-renewal Multi-lineage differentiationStem cells can be classified as:

Embryonic or fetal stem cells

Postnatal or adult stem cellsDental Applications of Stem CellsDental Pulp Stem Cells (DPSC)DPSCs are the stem cells which have the ability to regeneratethe dentin-pulp complex.Stem Cells from Human Exfoliated Primary Teeth(SHED)

The stem cells from human exfoliated primary teeth havebeen identified to form part of highly proliferative,clonogenic cell capable of differentiating into variety of cells types including neural cells, adipocytes, andodontoblasts.

The DPSCs and SHED are being utilized to a greatextent in regenerative endodontics.