NEET MDS Synopsis
Duodenum
PhysiologyAs the contents of the stomach become thoroughly liquefied, they pass into the duodenum, the first segment of the small intestine. The duodenum is the first 10" of the small intestine
Two ducts enter the duodenum:
one draining the gall bladder and hence the liver
the other draining the exocrine portion of the pancreas.
From the intestinal mucosal cells, and from the liver and gallbladder. Secretions from the pancreas and bile from the gallbladder enter the duodenum through the hepatopancreatic ampulla and the sphincter of Oddi. These lie where the pancreatic duct and common bile duct join before entering the duodenum. The presence of fatty chyme in the duodenum causes release of the hormone CCK into the bloodstream. CCK is one of the enterogastrones and its main function, besides inhibiting the stomach, is to stimulate the release of enzymes by the pancreas, and the contraction of the gallbladder to release bile. It also stimulates the liver to produce bile. Consumption of excess fat results in excessive bile production by the liver, and this can lead to the formation of gallstones from precipitation of the bile salts.
The acid in the chyme stimulates the release of secretin which causes the pancreas to release bicarbonate which neutralizes the acidity
The Soft Palate
Anatomy
This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).
The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.
During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.
Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.
The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
This aponeurosis attaches to the posterior margin of the hard palate.
Carbenicillin
Pharmacology
Carbenicillin
Antibiotic that is chemically similar to ampicillin. Active against gram-negative germs. It is well soluble in water and acid-labile.
DNA (Deoxyribonucleic acid)
PhysiologyDNA (Deoxyribonucleic acid) - controls cell function via transcription and translation (in other words, by controlling protein synthesis in a cell)
Transcription - DNA is used to produce mRNA
Translation - mRNA then moves from the nucleus into the cytoplasm & is used to produce a protein . requires mRNA, tRNA (transfer RNA), amino acids, & a ribosome
tRNA molecule
sequence of amino acids in a protein is determined by sequence of codons (mRNA). Codons are 'read' by anticodons of tRNAs & tRNAs then 'deliver' their amino acid.
Amino acids are linked together by peptide bonds (see diagram to the right)
As mRNA slides through ribosome, codons are exposed in sequence & appropriate amino acids are delivered by tRNAs. The protein (or polypeptide) thus grows in length as more amino acids are delivered.
The polypeptide chain then 'folds' in various ways to form a complex three-dimensional protein molecule that will serve either as a structural protein or an enzyme.
Onlay Preparation
Conservative DentistryOnlay Preparation
Onlay preparations are a type of indirect restoration used to restore teeth
that have significant loss of structure but still retain enough healthy tooth
structure to support a restoration. Onlays are designed to cover one or more
cusps of a tooth and are often used when a full crown is not necessary.
1. Definition of Onlay
A. Onlay
An onlay is a restoration that is
fabricated using an indirect procedure, covering one or more cusps of a
tooth. It is designed to restore the tooth's function and aesthetics while
preserving as much healthy tooth structure as possible.
2. Indications for Onlay Preparation
Extensive Caries: When a tooth has significant decay
that cannot be effectively treated with a filling but does not require a
full crown.
Fractured Teeth: For teeth that have fractured cusps or
significant structural loss.
Strengthening: To reinforce a tooth that has been
weakened by previous restorations or caries.
3. Onlay Preparation Procedure
A. Initial Assessment
Clinical Examination: Assess the extent of caries or
damage to determine if an onlay is appropriate.
Radiographic Evaluation: Use X-rays to evaluate the
tooth structure and surrounding tissues.
B. Tooth Preparation
Burs Used:
Commonly used burs include No. 169 L for initial cavity preparation
and No. 271 for refining the preparation.
Cavity Preparation:
Occlusal Entry: The initial occlusal entry should
be approximately 1.5 mm deep.
Divergence of Walls: All cavity walls should
diverge occlusally by 2-5 degrees:
2 degrees: For short vertical walls.
5 degrees: For long vertical walls.
Proximal Box Preparation:
The proximal box margins should clear adjacent teeth by 0.2-0.5 mm,
with 0.5 ± 0.2 mm being ideal.
C. Bevels and Flares
Facial and Lingual Flares:
Primary and secondary flares should be created on the facial and
lingual proximal walls to form the walls in two planes.
The secondary flare widens the proximal box, allowing for better
access and cleaning.
Gingival Bevels:
Should be 0.5-1 mm wide and blend with the secondary flare,
resulting in a marginal metal angle of 30 degrees.
Occlusal Bevels:
Present on the cavosurface margins of the cavity on the occlusal
surface, approximately 1/4th the depth of the respective wall, resulting
in a marginal metal angle of 40 degrees.
4. Dimensions for Onlay Preparation
A. Depth of Preparation
Occlusal Depth: Approximately 1.5 mm to ensure adequate
thickness of the restorative material.
Proximal Box Depth: Should be sufficient to accommodate
the onlay while maintaining the integrity of the tooth structure.
B. Marginal Angles
Facial and Lingual Margins: Should be prepared with a
30-degree angle for burnishability and strength.
Enamel Margins: Ideally, the enamel margins should be
blunted to a 140-degree angle to enhance strength.
C. Cusp Reduction
Cusp Coverage: Cusp reduction is indicated when more
than 1/2 of a cusp is involved, and mandatory when 2/3 or more is involved.
Uniform Metal Thickness: The reduction must provide for
a uniform metal thickness of approximately 1.5 mm over the reduced cusps.
Facial Cusp Reduction: For maxillary premolars and
first molars, the reduction of the facial cusp should be 0.75-1 mm for
esthetic reasons.
D. Reverse Bevel
Definition: A bevel on the margins of the reduced cusp,
extending beyond any occlusal contact with opposing teeth, resulting in a
marginal metal angle of 30 degrees.
5. Considerations for Onlay Preparation
Retention and Resistance: The preparation should be
designed to maximize retention and resistance form, which may include the
use of proximal retentive grooves and collar features.
Aesthetic Considerations: The preparation should
account for the esthetic requirements, especially in anterior teeth or
visible areas.
Material Selection: The choice of material (e.g., gold,
porcelain, composite) will influence the preparation design and dimensions.
Antiarrhythmic Drugs-Class I Sodium Channel Blockers
Pharmacology
Class I Sodium Channel Blockers
• Block movement of sodium into cells of the cardiac conducting system
• Results in a stabilizing effect and decreased formation and conduction of electrical impulses
• Have a local anesthetic effect
• Are declining in use due to proarrhythmic effects and increased mortality rates
• Na channel blockers - Class 1 drugs are divided into 3 subgroups
• 1A. 1B, 1C based on subtle differences in their mechanism of action.
• Blockade of these channels will prevent depolarization.
• Spread of action potential across myocardium will slow and areas of pacemaker activity is suppressed.
Class IA Sodium Channel Blockers
• Treatment of: symptomatic premature ventricular contractions, supraventricular tachycardia, and ventricular tachycardia, prevention of ventricular fibrillation
– Quinidine (Cardioquin, Quinaglute)
– Procainamide (Pronestyl, Procanbid)
– Disopyramide (Norpace)
• Quinidine – prototype
• Low therapeutic index
• High incidence of adverse effects
Class IB Sodium Channel Blockers
• Treatment of: symptomatic premature ventricular contractions and ventricular tachycardia, prevention of ventricular fibrillation
– Lidocaine (Xylocaine)
– Mexiletine (Mexitil)
– Tocainide (Tonocard)
– Phenytoin (Dilantin)
Side Effects: Lidocaine
• Drowsiness • Paresthesias • Muscle twitching • Convulsions • Changes in mental status (disorientation, confusion) • Hypersensitivity reactions (edema, uticaria, anaphylaxis)
Side Effects: Phenytoin (Dilantin)
• Gingival hyperplasia
• Nystagmus
• Ataxia, slurring of speech
• Tremors
• Drowsiness
• Confusion
• Lidocaine – prototype
• Must be given by injection
• Used as a local anesthetic
• Drug of choice for treating serious ventricular arrhythmias associated with acute myocardial infarction, cardiac surgery, cardiac catheterization and electrical conversion
Class IC Sodium Channel Blockers
• Treatment of: life-threatening ventricular tachycardia or fibrillation and supraventricular tachycardia unresponsive to other drugs
– Flecainide
– Propafenone
Adverse Effects
• CNS - dizziness, drowsiness, fatigue, twitching, mouth numbness, slurred speech vision changes, and tremors that can progress to convulsions.
• GI - changes in taste, nausea, and vomiting. CV - arrhythmias including heart blocks, hypotension, vasodilation, and potential for cardiac arrest.
• Other Rash, hypersensitivity reactions loss of hair and potential bone marrow depression.
Drug-Drug Interactions
• Increased risk for arrhythmias if combined with other drugs that are know to cause arrhythmias- digoxin and beta blockers
• Increased risk of bleeding if combined with oral anticoagulants.
Drug Food Interactions
• Quinidine needs an acidic urine for excretion. Increased levels lead to toxicity
• Avoid foods that alkalinize the urine- citrus juices, vegetables, antacid, milk products
Bases
Conservative DentistryBases in Restorative DentistryBases are an essential component in restorative dentistry, serving as a
thicker layer of material placed beneath restorations to provide additional
protection and support to the dental pulp and surrounding structures. Below is
an overview of the characteristics, objectives, and types of bases used in
dental practice.
1. Characteristics of BasesA. Thickness
Typical Thickness: Bases are generally thicker than
liners, typically ranging from 1 to 2 mm. Some bases may be
around 0.5 to 0.75 mm thick.
B. Functions
Thermal Protection: Bases provide thermal insulation to
protect the pulp from temperature changes that can occur during and after
the placement of restorations.
Mechanical Support: They offer supplemental mechanical
support for the restoration by distributing stress on the underlying dentin
surface. This is particularly important during procedures such as amalgam
condensation, where forces can be applied to the restoration.
2. Objectives of Using BasesThe choice of base material and its application depend on the Remaining
Dentin Thickness (RDT), which is a critical factor in determining the
need for a base:
RDT > 2 mm: No base is required, as there is sufficient
dentin to protect the pulp.
RDT 0.5 - 2 mm: A base is indicated, and the choice of
material depends on the restorative material being used.
RDT < 0.5 mm: Calcium hydroxide (Ca(OH)₂) or Mineral
Trioxide Aggregate (MTA) should be used to promote the formation of
reparative dentin, as the remaining dentin is insufficient to provide
adequate protection.
3. Types of BasesA. Common Base Materials
Zinc Phosphate (ZnPO₄): Known for its good mechanical
properties and thermal insulation.
Glass Ionomer Cement (GIC): Provides thermal protection
and releases fluoride, which can help in preventing caries.
Zinc Polycarboxylate: Offers good adhesion to tooth
structure and provides thermal insulation.
B. Properties
Mechanical Protection: Bases distribute stress
effectively, reducing the risk of fracture in the restoration and protecting
the underlying dentin.
Thermal Insulation: Bases are poor conductors of heat
and cold, helping to maintain a stable temperature at the pulp level.
Complement Fixation Test (CFT)
General MicrobiologyComplement Fixation Test (CFT)
This test is based upon two properties of the complement viz:
a. Complent combines with all antigen-antibody complexes whether or not it is required for that reaction
b. Complement is needed in immunolytic reaction.
Test system
It contains an antigen and a serum suspected to be having antibody to that antigen. The serum is heat treated prior to the test to destroy its complement. Complement Is added in measured quantity to this system. This complement is the form of guinea pig serum which is considered a rich source of complement. The test system is incubated.
Indicator system
To test system, after incubation, is added the indicator system which consists of sheep
RBCs and antibody to sheep RBCs (haemolysin) and another incubation is allowed.
If there is specific antibody in the test system, it will bind to antigen and to this complex the complement will also get fixed. Hence, no complement will be available to combine with indicator system which though contains RBCs and their specific antibody, cannot undergo haemolysis unless complement gets attached. Absence of haemolysis shall indicated positive test or presence of specific antibody in the serum which has been added in the test system. Erythrocytes lysis is obtained in negative test.