NEET MDS Synopsis
Primary Retention Form
Conservative DentistryPrimary Retention Form in Dental Restorations
Primary retention form refers to the geometric shape or design of a prepared
cavity that helps resist the displacement or removal of a restoration due to
tipping or lifting forces. Understanding the primary retention form is crucial
for ensuring the longevity and stability of various types of dental
restorations. Below is an overview of primary retention forms for different
types of restorations.
1. Amalgam Restorations
A. Class I & II Restorations
Primary Retention Form:
Occlusally Converging External Walls: The walls of
the cavity preparation converge towards the occlusal surface, which
helps resist displacement.
Occlusal Dovetail: In Class II restorations, an
occlusal dovetail is often included to enhance retention by providing
additional resistance to displacement.
B. Class III & V Restorations
Primary Retention Form:
Diverging External Walls: The external walls
diverge outward, which can reduce retention.
Retention Grooves or Coves: These features are
added to enhance retention by providing mechanical interlocking and
resistance to displacement.
2. Composite Restorations
A. Primary Retention Form
Mechanical Bond:
Acid Etching: The enamel and dentin surfaces are
etched to create a roughened surface that enhances mechanical retention.
Dentin Bonding Agents: These agents infiltrate the
demineralized dentin and create a hybrid layer, providing a strong bond
between the composite material and the tooth structure.
3. Cast Metal Inlays
A. Primary Retention Form
Parallel Longitudinal Walls: The cavity preparation
features parallel walls that help resist displacement.
Small Angle of Divergence: A divergence of 2-5 degrees
may be used to facilitate the seating of the inlay while still providing
adequate retention.
4. Additional Considerations
A. Occlusal Dovetail and Secondary Retention Grooves
Function: These features aid in preventing the proximal
displacement of restorations by occlusal forces, enhancing the overall
retention of the restoration.
B. Converging Axial Walls
Function: Converging axial walls help prevent occlusal
displacement of the restoration, ensuring that the restoration remains
securely in place during function.
Blood
PhysiologyBlood is a liquid tissue. Suspended in the watery plasma are seven types of cells and cell fragments.
red blood cells (RBCs) or erythrocytes
platelets or thrombocytes
five kinds of white blood cells (WBCs) or leukocytes
Three kinds of granulocytes
neutrophils
eosinophils
basophils
Two kinds of leukocytes without granules in their cytoplasm
lymphocytes
monocytes
Anti-Infective and Anticariogenic Agents
PedodonticsAnti-Infective and Anticariogenic Agents in Human Milk
Human milk is not only a source of nutrition for infants but also contains
various bioactive components that provide anti-infective and anticariogenic
properties. These components play a crucial role in protecting infants from
infections and promoting oral health. Below are the key agents found in human
milk:
1. Immunoglobulins
Secretory IgA: The predominant immunoglobulin in human
milk, secretory IgA plays a vital role in mucosal immunity by preventing the
attachment of pathogens to mucosal surfaces.
IgG and IgM: These immunoglobulins also contribute to
the immune defense, with IgG providing systemic immunity and IgM being
involved in the initial immune response.
2. Cellular Elements
Lymphoid Cells: These cells are part of the immune
system and help in the recognition and response to pathogens.
Polymorphonuclear Leukocytes (Polymorphs): These white
blood cells are essential for the innate immune response, helping to engulf
and destroy pathogens.
Macrophages: These cells play a critical role in
phagocytosis and the immune response, helping to clear infections.
Plasma Cells: These cells produce antibodies,
contributing to the immune defense.
3. Complement System
C3 and C4 Complement Proteins: These components of the
complement system have opsonic and chemotactic activities, enhancing the
ability of immune cells to recognize and eliminate pathogens. They promote
inflammation and attract immune cells to sites of infection.
4. Unsaturated Lactoferrin and Transferrin
Lactoferrin: This iron-binding protein has
antimicrobial properties, inhibiting the growth of bacteria and fungi by
depriving them of iron.
Transferrin: Similar to lactoferrin, transferrin also
binds iron and plays a role in iron metabolism and immune function.
5. Lysozyme
Function: Lysozyme is an enzyme that breaks down
bacterial cell walls, providing antibacterial activity. It helps protect the
infant from bacterial infections.
6. Lactoperoxidase
Function: This enzyme produces reactive oxygen species
that have antimicrobial effects, contributing to the overall antibacterial
properties of human milk.
7. Specific Inhibitors (Non-Immunoglobulins)
Antiviral and Antistaphylococcal Factors: Human milk
contains specific factors that inhibit viral infections and the growth of
Staphylococcus bacteria, providing additional protection against infections.
8. Growth Factors for Lactobacillus Bifidus
Function: Human milk contains growth factors that
promote the growth of beneficial bacteria such as Lactobacillus bifidus,
which plays a role in maintaining gut health and preventing pathogenic
infections.
9. Para-Aminobenzoic Acid (PABA)
Function: PABA may provide some protection against
malaria, highlighting the potential role of human milk in offering broader
protective effects against various infections.
Thalassaemia
General Pathology
Thalassaemia. Genetic based defect in synthesis of one of the normal chains.
Beta thalassaemia ---> reduced Hb A and increased HbF (α2, Y2) HBA2(α2)
Alpha thalassaemia ---> reduced Hb-A, Hb-A2 and Hb-F-with formation of Hb-H(β4) and Hb Barts (Y4).
Thalassaemia may manifest as trait or disease or with intermediate manifestation.
Features:
• Microcytic hypochromic RBC is in iron deficjency.
• Marked anisopoikilocytsis with prominent target cells.
• Reticulocytosis and nucleated RBC seen.
• Mongoloid facies and X-ray findings characteristic of marrow hyperplasia
• Decreased osmotic. fragility.
• Increased marrow iron (important difference from iron deficiency anaemia).
• Haemosiderosis, especially with repeated transfusions.
Diagnosis is by Hb electrophoresis and by Alkali denaturation test (for HbF).
HAEMORRHAGIC DISORDERS
General Pathology
HAEMORRHAGIC DISORDERS
Normal homeostasis depends on
-Capillary integrity and tissue support.
- Platelets; number and function
(a) For integrity of capillary endothelium and platelet plug by adhesion and aggregation
(b) Vasoactive substances for vasoconstriction
(c) Platelet factor for coagulation.
(d) clot retraction.
- Fibrinolytic system(mainly Plasmin) : which keeps the coagulatian system in check.
Coagulation disorders
These may be factors :
Deficiency .of factors
Genetic.
Vitamin K deficiency.
Liver disease.
Secondary to disseminated intravascular coagulation.or defibrinatian
Overactive fibrinolytic system.
Inhibitors of the factars (immune, acquired).
Anticoagulant therapy as in myocardial infarctian.
Haemophilia. Genetic disease transmitted as X linked recessive trait. Comman in Europe. Defect in fcatorVII Haemophilia A .or in fact .or IX-Haemaphilia B (rarer).
Features:
May manifest in infancy or later.
Severity depends on degree of deficiency.
Persistant woundbleeding.
Easy Bruising with Haemotoma formation
Nose bleed , arthrosis, abdominal pain with fever and leucocytosis
Prognosis is good with prevention of trauma and-transfusion of Fresh blood or fTesh plasma except for danger of developing immune inhibitors.
Von Willebrand's disease. Capillary fragility and decreased factor VIII (due to deficient stimulatory factor). It is transmitted in an autosomal dominant manner both. Sexes affected equally
Vitamin K Deficiency. Vitamin K is needed for synthesis of factor II,VII,IX and X.
Deficiency maybe due to:
Obstructive jaundice.
Steatorrhoea.
Gut sterilisation by antibiotics.
Liver disease results in :
Deficient synthesis of factor I II, V, Vll, IX and X Incseased fibrinolysis (as liver is the site of detoxification of activators ).
Defibrination syndrome. occurs when factors are depleted due to disseminated .intravascular coagulation (DIC). It is initiated by endothelial damage or tissue factor entering the circulation.
Causes
Obstetric accidents, especially amniotic fluid embolism. Septicaemia. .
Hypersensitivity reactions.
Disseminated malignancy.
Snake bite.
Vascular defects :
(Non thrombocytopenic purpura).
Acquired :
Simple purpura a seen in women. It is probably endocrinal
Senile parpura in old people due to reduced tissue support to vessels
Allergic or toxic damage to endothelium due to Infections like Typhoid Septicemia
Col!agen diseases.
Scurvy
Uraemia damage to endothelium (platelet defects).
Drugs like aspirin. tranquillisers, Streptomvcin pencillin etc.
Henoc schonlien purpura Widespeard vasculitis due to hypersensitivity to bacteria or foodstuff
It manifests as :
Pulrpurric rashes.
Arthralgia.
Abdominal pain.
Nephritis and haematuria.
Hereditary :
(a) Haemhoragic telangieclasia. Spider like tortous vessels which bleed easily. There are disseminated lesions in skin, mucosa and viscera.
(b) Hereditary capillary fragilily similar to the vascular component of von Willbrand’s disease
.(c) Ehler Danlos Syndrome which is a connective tissue defect with skin, vascular and joint manifestations.
Platelet defects
These may be :
(I) Qualitative thromboasthenia and thrombocytopathy.
(2) Thrombocytopenia :Reduction in number.
(a) Primary or idiopathic thrombocytopenic purpura.
(b) Secondary to :
(i) Drugs especially sedormid
(ii) Leukaemias
(iii) Aplastic-anaemia.
Idiopathic thrombocytopenic purpura (ITP). Commoner in young females.
Manifests as :
Acute self limiting type.
Chronic recurring type.
Features:
(i) Spontaneous bleeding and easy bruisability
(ii)Skin (petechiae), mucus membrane (epistaxis) lesions and sometimes visceral lesions involving any organ.
Thrombocytopenia with abnormal forms of platelets.
Marrow shows increased megakaryocytes with immature forms,
vacuolation, and lack of platelet budding.
Pathogenesis:
hypersensitivity to infective agent in acute type.
Plasma thrombocytopenic factor ( Antibody in nature) in chronic type
Q Fever
General Pathology
Q Fever
An acute disease caused by Coxiella burnetii (Rickettsia burnetii) and
characterized by sudden onset of fever, headache, malaise, and interstitial
pneumonitis.
Symptoms and Signs
The incubation period varies from 9 to 28 days and averages 18 to 21 days. Onset
is abrupt, with fever, severe headache, chills, severe malaise, myalgia, and,
often, chest pains. Fever may rise to 40° C (104° F) and persist for 1 to > 3
wk. Unlike other rickettsial diseases, Q fever is not associated with a
cutaneous exanthem. A nonproductive cough and x-ray evidence of pneumonitis
often develop during the 2nd wk of illness.
In severe cases, lobar consolidation usually occurs, and the gross appearance of
the lungs may resemble that of bacterial pneumonia
About 1/3 of patients with protracted Q fever develop hepatitis, characterized
by fever, malaise, hepatomegaly with right upper abdominal pain, and possibly
jaundice. Liver biopsy specimens show diffuse granulomatous changes, and C.
burnetii may be identified by immunofluorescence.
Types of Removable Orthodontic Appliances
OrthodonticsTypes of Removable Orthodontic Appliances
Functional Appliances:
Purpose: Designed to modify the growth of the jaw
and improve the relationship between the upper and lower teeth.
Examples:
Bionator: Encourages forward positioning of the
mandible.
Frankel Appliance: Used to modify the position
of the dental arches and improve facial aesthetics.
Retainers:
Purpose: Used to maintain the position of teeth
after orthodontic treatment.
Types:
Hawley Retainer: A custom-made acrylic plate
with a wire framework that holds the teeth in position.
Essix Retainer: A clear, plastic retainer that
fits over the teeth, providing a more aesthetic option.
Space Maintainers:
Purpose: Used to hold space for permanent teeth
when primary teeth are lost prematurely.
Types:
Band and Loop: A metal band placed on an
adjacent tooth with a loop extending into the space.
Distal Shoe: A space maintainer used in the
lower arch to maintain space for the first molar.
Aligners:
Purpose: Clear plastic trays that gradually move
teeth into the desired position.
Examples:
Invisalign: A popular brand of clear aligners
that uses a series of custom-made trays to achieve tooth movement.
Expansion Appliances:
Purpose: Used to widen the dental arch,
particularly in cases of crossbite or narrow arches.
Examples:
Rapid Palatal Expander (RPE): A device that
applies pressure to the upper molars to widen the maxilla.
Components of Removable Orthodontic Appliances
Baseplate: The foundation of the appliance, usually
made of acrylic, which holds the other components in place.
Active Components: Springs, screws, or other mechanisms
that exert forces on the teeth to achieve movement.
Retention Components: Clasps or other features that
help keep the appliance securely in place during use.
Adjustable Parts: Some appliances may have adjustable
components to fine-tune the force applied to the teeth.
Indications for Use
Correction of Malocclusions: Removable appliances can
be used to address various types of malocclusions, including crowding,
spacing, and crossbites.
Space Maintenance: To hold space for permanent teeth
when primary teeth are lost prematurely.
Tooth Movement: To move teeth into desired positions,
particularly in growing patients.
Retention: To maintain the position of teeth after
orthodontic treatment.
Jaw Relationship Modification: To influence the growth
of the jaw and improve the relationship between the dental arches.
Advantages of Removable Orthodontic Appliances
Patient Compliance: Patients can remove the appliance
for eating, brushing, and social situations, which can improve compliance.
Hygiene: Easier to clean compared to fixed appliances,
reducing the risk of plaque accumulation and dental caries.
Flexibility: Can be adjusted or modified as treatment
progresses.
Less Discomfort: Generally, removable appliances are
less uncomfortable than fixed appliances, especially during initial use.
Aesthetic Options: Clear aligners and other aesthetic
appliances can be more visually appealing to patients.
Disadvantages of Removable Orthodontic Appliances
Compliance Dependent: The effectiveness of removable
appliances relies heavily on patient compliance; if not worn as prescribed,
treatment may be delayed or ineffective.
Limited Force Application: They may not be suitable for
complex tooth movements or significant skeletal changes.
Adjustment Period: Some patients may experience
discomfort or difficulty speaking initially.
Enophthalmos
Oral and Maxillofacial SurgeryEnophthalmos
Enophthalmos is a condition characterized by the inward
sinking of the eye into the orbit (the bony socket that holds the eye). It is
often a troublesome consequence of fractures involving the zygomatic complex
(the cheekbone area).
Causes of Enophthalmos
Enophthalmos can occur due to several factors following an injury:
Loss of Orbital Volume:
There may be a decrease in the volume of the contents within the
orbit, which can happen if soft tissues herniate into the maxillary
sinus or through the medial wall of the orbit.
Fractures of the Orbital Walls:
Fractures in the walls of the orbit can increase the volume of the
bony orbit. This can occur with lateral and inferior displacement of the
zygoma or disruption of the inferior and lateral orbital walls. A
quantitative CT scan can help visualize these changes.
Loss of Ligament Support:
The ligaments that support the eye may be damaged, contributing to
the sinking of the eye.
Post-Traumatic Changes:
After an injury, fibrosis (the formation of excess fibrous
connective tissue), scar contraction, and fat atrophy (loss of fat in
the orbit) can occur, leading to enophthalmos.
Combination of Factors:
Often, enophthalmos results from a combination of the above factors.
Diagnosis
Acute Cases: In the early stages after an injury,
diagnosing enophthalmos can be challenging. This is because swelling (edema)
of the surrounding soft tissues can create a false appearance of
enophthalmos, making it seem like the eye is more sunken than it actually
is.