NEET MDS Synopsis
Mouthguards
PedodonticsClassification of Mouthguards
Mouthguards are essential dental appliances used primarily in sports to
protect the teeth, gums, and jaw from injury. The American Society for Testing
and Materials (ASTM) has established a classification system for athletic
mouthguards, which categorizes them into three types based on their design, fit,
and level of customization.
Classification of Mouthguards
ASTM Designation: F697-80 (Reapproved 1986)
Type I: Stock Mouthguards
Description: These are pre-manufactured mouthguards
that come in standard sizes and shapes.
Characteristics:
Readily available and inexpensive.
No customization for individual fit.
Typically made from a single layer of material.
May not provide optimal protection or comfort due to their
generic fit.
Usage: Suitable for recreational sports or
activities where the risk of dental injury is low.
Type II: Mouth-Formed Mouthguards
Description: Also known as "boil-and-bite"
mouthguards, these are made from thermoplastic materials that can be
softened in hot water and then molded to the shape of the wearer’s
teeth.
Characteristics:
Offers a better fit than stock mouthguards.
Provides moderate protection and comfort.
Can be remolded if necessary, allowing for some customization.
Usage: Commonly used in youth sports and activities
where a higher risk of dental injury exists.
Type III: Custom-Fabricated Mouthguards
Description: These mouthguards are custom-made by
dental professionals using a dental cast of the individual’s teeth.
Characteristics:
Provides the best fit, comfort, and protection.
Made from high-quality materials, often with multiple layers for
enhanced shock absorption.
Tailored to the specific dental anatomy of the wearer, ensuring
optimal retention and stability.
Usage: Recommended for athletes participating in
contact sports or those at high risk for dental injuries.
Summary of Preference
The classification system is based on an ascending order of preference:
Type I (Stock Mouthguards): Least preferred due to
lack of customization and fit.
Type II (Mouth-Formed Mouthguards): Moderate
preference, offering better fit than stock options.
Type III (Custom-Fabricated Mouthguards): Most
preferred for their superior fit, comfort, and protection.
ACRYLIC RESINS
Dental Materials
ACRYLIC RESINS
Use. Acrylic (unfilled) resins are used as temporary crown material. Temporary crowns are placed to protect the crown preparation and provide patient comfort during the time the permanent crown is being constructed
Muscle pathology
General Pathology
Muscle pathology
1. Myasthenia gravis
a. An autoimmune disease caused by autoantibodies to acetylcholine receptors at the neuromuscular junctions.
b. Characterized by muscle weakness or the inability to maintain long durations of muscle contractions; this worsens during exercise but recovers after rest.
c. Affects various muscle groups, including:
(1) Eyes—diplopia, ptosis.
(2) Neck—dysphagia, problems swallowing or speaking.
(3) Extremities—arms and legs.
d. Treatment: cholinesterase inhibitors(neostigmine), anti-immune therapy.
2. Muscle tumors
a. Rhabdomyoma—benign tumor of skeletal muscle.
b. Leiomyoma
(1) Benign tumor of smooth muscle.
(2) Most common tumor found in women.
(3) Usually affects the uterus, although it can occur anywhere.
c. Rhabdomyosarcoma
(1) Malignant tumor of skeletal muscle.
(2) Most common sarcoma found in children.
(3) Usually affects head and neck region—orbit, nasal cavity, and nasopharynx.
Blood Groups
PhysiologyBlood Groups
Blood groups are created by molecules present on the surface of red blood cells (and often on other cells as well).
The ABO Blood Groups
The ABO blood groups are the most important in assuring safe blood transfusions.
Blood Group
Antigens on RBCs
Antibodies in Serum
Genotypes
A
A
Anti-B
AA or AO
B
B
Anti-A
BB or BO
AB
A and B
Neither
AB
O
Neither
Anti-A and anti-B
OO
When red blood cells carrying one or both antigens are exposed to the corresponding antibodies, they agglutinate; that is, clump together. People usually have antibodies against those red cell antigens that they lack.
The critical principle to be followed is that transfused blood must not contain red cells that the recipient's antibodies can clump. Although theoretically it is possible to transfuse group O blood into any recipient, the antibodies in the donated plasma can damage the recipient's red cells. Thus all transfusions should be done with exactly-matched blood.
The Rh System
Rh antigens are transmembrane proteins with loops exposed at the surface of red blood cells. They appear to be used for the transport of carbon dioxide and/or ammonia across the plasma membrane. They are named for the rhesus monkey in which they were first discovered.
There are a number of Rh antigens. Red cells that are "Rh positive" express the one designated D. About 15% of the population have no RhD antigens and thus are "Rh negative".
The major importance of the Rh system for human health is to avoid the danger of RhD incompatibility between mother and fetus.
During birth, there is often a leakage of the baby's red blood cells into the mother's circulation. If the baby is Rh positive (having inherited the trait from its father) and the mother Rh-negative, these red cells will cause her to develop antibodies against the RhD antigen. The antibodies, usually of the IgG class, do not cause any problems for that child, but can cross the placenta and attack the red cells of a subsequent Rh+ fetus. This destroys the red cells producing anemia and jaundice. The disease, called erythroblastosis fetalis or hemolytic disease of the newborn, may be so severe as to kill the fetus or even the newborn infant. It is an example of an antibody-mediated cytotoxicity disorder.
Although certain other red cell antigens (in addition to Rh) sometimes cause problems for a fetus, an ABO incompatibility does not. Rh incompatibility so dangerous when ABO incompatibility is not
It turns out that most anti-A or anti-B antibodies are of the IgM class and these do not cross the placenta. In fact, an Rh−/type O mother carrying an Rh+/type A, B, or AB fetus is resistant to sensitization to the Rh antigen. Presumably her anti-A and anti-B antibodies destroy any fetal cells that enter her blood before they can elicit anti-Rh antibodies in her.
This phenomenon has led to an extremely effective preventive measure to avoid Rh sensitization. Shortly after each birth of an Rh+ baby, the mother is given an injection of anti-Rh antibodies. The preparation is called Rh immune globulin (RhIG) or Rhogam. These passively acquired antibodies destroy any fetal cells that got into her circulation before they can elicit an active immune response in her.
Rh immune globulin came into common use in the United States in 1968, and within a decade the incidence of Rh hemolytic disease became very low.
Classification of Fatty Acids and Triglycerides
Biochemistry
Classification of Fatty Acids and Triglycerides
Short-chain: 2-4 carbon atoms
Medium-chain: 6-12 carbon atoms
Long-chain: 14-20 carbon atoms
Very long-chain: >20 carbon atoms
• are usually in esterified form as major components of other lipids
A16-carbon fatty acid, with one cis double bond between carbon atoms 9 and 10 may be represented as 16:1 cisD9.
Double bonds in fatty acids usually have the cis configuration. Most naturally occurring fatty acids have an even number of carbon atoms
Examples of fatty acids
18:0
stearic acid
18:1 cisD9
oleic acid
18:2 cisD9,12
linoleic acid
18:3 cisD9,12,15
linonenic acid
20:4 cisD5,8,11,14
arachidonic acid
There is free rotation about C-C bonds in the fatty acid hydrocarbon, except where there is a double bond. Each cis double bond causes a kink in the chain,
CHEMICAL AGENTS
General Microbiology
CHEMICAL AGENTS
Chlorine and iodine are most useful disinfectant Iodine as a skin disinfectant and chlorine as a water disinfectant have given consistently magnificent results. Their activity is almost exclusively bactericidal and they are effective against sporulating organisms also.
Mixtures of various surface acting agents with iodine are known as iodophores and these are used for the sterilization of dairy products.
Apart from chlorine, hypochlorite, inorganic chioramines are all good disinfectants but they act by liberating chlorine.
Hydrogen peroxide in a 3% solution is a harmless but very weak disinfectant whose primary use is in the cleansing of the wound.
Potassium permanganate is another oxidising agent which is used in the treatment of urethntzs.
Formaldehyde — is one of the least selective agent acting on proteins. It is a gas that is usually employed as its 37% solution, formalin.
When used in sufficiently high concentration it destroys the bacteria and their spores.
Classification of chemical sterilizing agents
Chemical disinfectant
Interfere with membrane functions
• Surface acting agents : Quaternary ammonium, Compounds, Soaps and fatty acids
• Phenols : Phenol, cresol, Hexylresorcinol
• Organic solvent : Chloroform, Alcohol
Denatures proteins
• Acids and alkalies : Organic acids, Hydrochloric acid , Sulphuric acid
Destroy functional groups of proteins
• Heavy metals : Copper, silver , Mercury
• Oxidizing agents: Iodine, chlorine, Hydrogen peroxide
• Dyes : Acridine orange, Acriflavine
• Alkylating agents : Formaldehyde, Ethylene oxide
Applications and in-use dilution of chemical disinfectants
Alcohols : Skin antiseptic Surface disinfectant, Dilution used 70%
Mercurials : Skin antiseptic Surface disinfectant Dilution Used 0.1 %
Silver nitrate : Antiseptic (eyes and burns) Dilution Used 1 %
Phenolic compound : Antiseptic skin washes Dilution Used .5 -5 %
Iodine : Disinfects inanimate object, Skin antiseptic Dilution used 2%
Chlorine compounds : Water treatment Disinfect inanimate objects , Dillution used 5 %
Quaternary ammonium Compounds : Skin antiseptic , Disinfects inanimate object, Dilution Used < 1 %
Glutaraldehyde: Heat sensitve instruments, Dilution used 1-2 %
Cold sterilization can be achieved by dipping the precleaned instrument in 2% solution of gluteraldehyde for 15-20 minutes. This time is sufficient to kill the vegetative form as well as spores ofthe organisms that are commonly encountered in the dentistry.
Ethylene oxide is an a agent extensively used in gaseous sterilization. It is active against all kinds of bacteria and their spores. but its greatest utility is in sterilizing those objects which are damaged by heat (e.g. heart lung machine). It is also used to sterlise fragile, heat sensitive equipment, powders as well as components of space crafts.
Evaluation of Disinfectants
Two methods which are widely employed are:
Phenol coefficient test, Kelsey -Sykes test
These tests determine the capacity of disinfectant as well as their ability to retain their activity.
Fibrous and Fibro-Osseous Tumors
General Pathology
Fibrous and Fibro-Osseous Tumors
Fibrous tumors of bone are common and comprise several morphological variants.
1. Fibrous Cortical Defect and Nonossifying Fibroma
Fibrous cortical defects occur in 30% to 50% of all children older than 2 years of age; they are probably developmental rather than true neoplasms. The vast majority are smaller than 0.5 cm and arise in the metaphysis of the distal femur or proximal tibia; almost half are bilateral or multiple. They may enlarge in size (5-6 cm) to form nonossifying fibromas. Both lesions present as sharply demarcated radiolucencies surrounded by a thin zone of sclerosis. Microscopically are cellular and composed of benign fibroblasts and macrophages, including multinucleated forms. The fibroblasts classically exhibit a storiform pattern. Fibrous cortical defects are asymptomatic and are usually only detected as incidental radiographic lesions. Most undergo spontaneous differentiation into normal cortical bone. The few that enlarge into nonossifying fibromas can present with pathologic fracture; in such cases biopsy is necessary to rule out other tumors.
2. Fibrous Dysplasia
is a benign mass lesion in which all components of normal bone are present, but they fail to differentiate into mature structures. Fibrous dysplasia occurs as one of three clinical patterns:
A. Involvement of a single bone (monostotic)
B. nvolvement of multiple bones (polyostotic)
C. Polyostotic disease, associated with café au lait skin pigmentations and endocrine abnormalities, especially precocious puberty (Albright syndrome).
Monostotic fibrous dysplasia accounts for 70% of cases. It usually begins in early adolescence, and ceases with epiphyseal closure. It frequently involves ribs, femur, tibia & jawbones. Lesions are asymptomatic and usually discovered incidentally. However, fibrous dysplasia can cause marked enlargement and distortion of bone, so that if the face or skull is involved, disfigurement can occur.
Polyostotic fibrous dysplasia without endocrine dysfunction accounts for the majority of the remaining cases.
It tends to involve the shoulder and pelvic girdles, resulting in severe deformities and spontaneous fractures.
Albright syndrome accounts for 3% of all cases. The bone lesions are often unilateral, and the skin pigmentation is usually limited to the same side of the body. The cutaneous macules are classically large, dark to light brown (café au lait), and irregular.
Gross features
• The lesion is well-circumscribed, intramedullary; large masses expand and distort the bone.
On section it is tan-white and gritty.
Microscopic features
• There are curved trabeculae of woven bone (mimicking Chinese characters), without osteoblastic rimming
• The above are set within fibroblastic proliferation
Individuals with monostotic disease usually have minimal symptoms. By x-ray, lesions exhibit a characteristic ground-glass appearance with well-defined margins. Polyostotic involvement is frequently associated with progressive disease, and more severe skeletal complications (e.g., fractures, long bone deformities, and craniofacial distortion). Rarely, polyostotic disease can transform into osteosarcoma, especially following radiotherapy.
ERUPTION - Permanent teeth
Dental Anatomy
Permanent teeth
1. The permanent teeth begin formation between birth and 3 years of age (except for the third molars)
2. The crowns of permanent teeth are completed between 4 and 8 years of age, at approximately one- half the age of eruption
The sequence for permanent development
Maxillary
First molar → Central incisor → Lateral incisor → First premotar → Second pmmolar → Canine → Second molar → Third molar
Mandibular
First molar → Central incisor → Lateral incisor → Canine → First premolar → Second premolar → Second molar → Third molar
Permanent teeth emerge into the oral cavity as
Maxillary Mandibular
Central incisor 7-8 years 6-7 years
Lateral incisor 8-9 years 7-8 years
Canine 11-12 years 9-10 years
First premolar 10-Il years 10-12 years
Second premolar 10-12 years 11-12 years
First molar 6-7 years 6-7 years
Second molar 12-13 years 11-13 years
Third molar 17-21 years 17-21 years
The roots of the permanent teeth are completed between 10 and 16 years of age, 2 to 3 years after eruption