NEET MDS Synopsis
Microbes causing Food poisoning
Microbiology
Infectious
Salmonella [poultry, meat, eggs]
Salmonella enteritidis
Vibrio parahaemolyticus [seafood]
Enterohemorrhagic E. coli
Other diarrhetic E. coli
Clostridium perfringens [reheated meat]
Yersinia enterocolitica
Campylobacter jejuni/coli
Cholera vibrio [seafood]
Shigella
Typhus bacilli, paratyphoid bacilli
Vibrio vulnificus [seafood]
Toxic
Staphylococcus aureus [meats, mayo, custard]
Clostridium botulinum [canned foods]
Bacillus cereus [reheated rice]
Viral food poisoning
Norovirus
Sapovirus
Viral hepatitis A
Viral hepatitis E
Protozoa
Cryptosporidium
Cyclospora
Barbiturates
Pharmacology
Barbiturates (BARBS):
were used for antianxiety, sedation but now replaced by BZs; for IV sedation & oral surgery
Advantages: effective and relatively inexpensive (common in third world countries), extensively studied so have lots of information about side effects/toxicity
Peripheral effects: respiratory depression (with ↑ dose), CV effects (↓ BP and HR at sedative-hypnotic doses), liver effects (bind CYP450 → induction of drug metabolism and other enzymes → ↑ metabolism of steroids, vitamins K/D, cholesterol, and bile salts)
General mechanisms: potently depress neuron activity in the reticular formation (pons, medulla) and cortex
o Bind barbiturate site on GABAA receptor → enhanced inhibitory effect and ↑ Cl influx; → ↓ frequency of Cl channel opening but ↑ open time of Cl channels (in presense of GABA) so more Cl enters channel (at high [ ] they directly ↑ Cl conductance in absence of GABA- act as GABA mimetics)
Metabolism: liver microsomal drug metabolizing enzymes; most are dealkylated, conjugated by glucoronidation; renal excretion
Uses: anticonvulsant, preoperative sedation, anesthesia
Side effects: sedation, confusion, weight gain, N/V, skin rash
Contraindications: pain (can ↑ sensitivity to painful situations → restlessness, excitement, and delirium) and pulmonary insufficiency (since BARBS → respiratory depression)
Drug interactions: have additive depressant affects when taken with other CNS depressants, enhance depressive effects (of antipsychotics, antihistamines, antiHTNs, ethanol, and TCAs), and accelerates metabolism (of β blockers, Ca-channel blockers, corticosteroids, estrogens, phenothiazines, valproic acid, and theophylline; occurs with chronic BARB ingestion)
Acute toxicity: lower therapeutic index; can be fatal if OD; BARB poisoning a major problem (serious toxicity at only 10x hypnotic dose; → respiratory depression, circulatory collapse, renal failure, pulmonary complications which can be life-threatening)
Symptoms: severe respiratory depression, coma, severe hypotension, hypothermia
Treatment: support respiration and BP, gastric lavage (if recent ingestion)
Tolerance: metabolic (induce hepatic metabolic enzymes, occurs within a few days), pharmacodynamic (↓ CNS response with chronic exposure occurs over several weeks; unknown mechanism), and cross tolerance (tolerance to other general CNS depressants)
Physical dependence: develops with continued use; manifest by withdrawal symptoms (mild = anxiety, insomnia, dizziness, nausea; severe = vomiting, hyperthermia, tremors, delirium, convulsions, death)
Other similar agents: meprobamate (Equanil; pharmacological properties like BZs and barbiturates but mechanism unknown) and chloral hydrate (common sedative in pediatric dentistry for diagnostic imaging; few adverse effects but low therapeutic index)
Other drugs for antianxiety: β-adrenoceptor blockers (e.g., propranolol; block autonomic effects- palpitations, sweating, shaking; used for disabling situational anxiety like stage fright), buspirone (partial agonist at serotonin 1A receptor, produces only anxiolytic effects so no CNS depression, dependence, or additive depression with ethanol but onset of action is 1-3 weeks), lodipem (not a BZ but does act at BZ receptors)
Impression Materials -Applications
Dental Materials
Applications
a. Dentulous impressions for casts for prosthodontics
b. Dentulous impressions for pedodontic appliances
c. Dentulous impressions for study models for orthodontics
d. Edentulous impressions for casts for denture construction
The Nasal Mucosa
AnatomyThe Nasal Mucosa
Mucosa lines the entire nasal cavities except for the vestibule of the nose.
The nasal mucosa is firmly bound to the periosteum and perichondrium of the supporting structures of the nose.
It is continuous with the adjoining cavities to which the nasal cavity communicates (e.g., the nasopharynx and paranasal sinuses).
The inferior 2/3 of the nasal mucosa is called the respiratory area and air passing over this is warmed and moistened before it passes into the lungs.
The superior 1/3 is called the olfactory area.
The Olfactory Area of Nasal Mucosa
This area contains the peripheral organ of smell.
Sniffing draws air into this area
Olfactory receptor cells (from the olfactory nerve, CN I, are located in the mucosa of this area in the nose.
Nerves to the Respiratory Area of Nasal Mucosa
The inferior 2/3 of the nasal mucosa are supplied chiefly by the trigeminal nerve (CN V).
The mucous membrane of the nasal septum is supplied chiefly by the nasopalatine nerve, a branch of the maxillary nerve (CN V2).
Its anterior portion is supplied by the anterior ethmoidal nerve (a branch of the nasociliary nerve) which is derived from the ophthalmic nerve (CN V1).
The lateral walls of the nasal cavity are supplied by branches of the maxillary nerve (CN V2); the greater palatine nerve, and the anterior ethmoidal nerve.
Arteries of the Nasal Mucosa
The blood supply of the mucosa of the nasal septum is derived mainly from the maxillary artery.
The sphenopalatine artery, a branch of the maxillary, supplies most of the blood of the nasal mucosa.
It enters by the sphenopalatine foramen and sends branches to the posterior regions of the lateral wall and to the nasal septum.
The greater palatine artery, also a branch of the maxillary, passes through the incisive foramen to supply the nasal septum.
The anterior and posterior ethmoidal arteries, branches of the ophthalmic artery, supply the anterosuperior part of the mucosa of the lateral wall of the nasal cavity and nasal septum.
Three branches of the facial artery (superior labial, ascending palatine, and lateral nasal) also supply the anterior parts of the nasal mucosa.
Veins of the Nasal Mucosa
The veins of the nasal mucosa form a venous network of plexus in the connective tissue of the nasal mucosa.
Some of the veins open into the sphenopalatine vein and drain to the pterygoid plexus.
Others join the facial and infraorbital veins.
Some empty into the ophthalmic veins and drain into the cavernous sinus.
Enamel
Dental Anatomy
Enamel
Structural characteristics and microscopic features
a. Enamel rods or prisms
(1) Basic structural unit of enamel.
(2) Consists of tightly packed hydroxyapatite crystals. Hydroxyapatite crystals in enamel are four times larger and more tightly packed than hydroxyapatite found in other calcified
tissues (i.e., it is harder than bone).
(3) Each rod extends the entire thickness of enamel and is perpendicular to the dentinoenamel junction (DEJ).
b. Aprismatic enamel
(1) The thin outer layer of enamel found on the surface of newly erupted teeth.
(2) Consists of enamel crystals that are aligned perpendicular to the surface.
(3) It is aprismatic (i.e., prismless) and is more mineralized than the enamel beneath it.
(4) It results from the absence of Tomes processes on the ameloblasts during the final stages of enamel deposition.
c. Lines of Retzius (enamel striae)
(1) Microscopic features
(a) In longitudinal sections, they are observed as brown lines that extend from the DEJ to the
tooth surface.
(b) In transverse sections, they appear as dark, concentric rings similar to growth rings in a tree.
(2) The lines appear weekly during the formation of enamel.
(3) Although the cause of striae formation is unknown, the lines may represent appositional or incremental growth of enamel. They may also result from metabolic disturbances of ameloblasts.
(4) Neonatal line
(a) An accentuated, dark line of Retzius that results from the effect of physiological changes
on ameloblasts at birth.
(b) Found in all primary teeth and some cusps of permanent first molars.
d. Perikymata
(1) Lines of Retzius terminate on the tooth surface in shallow grooves known a perikymata.
(2) These grooves are usually lost through wear but may be observed on the surfaces of developing teeth or nonmasticatory surfaces of formed teeth.
e. Hunter-Schreger bands
(1) Enamel rods run in different directions. In longitudinal sections, these changes in direction result in a banding pattern known as HunterSchreger bands.
(2) These bands represent an optical phenomenon of enamel and consist of a series of alternating dark and light lines when the section is viewed with reflected or polarized
light.
f. Enamel tufts
(1) Consist of hypomineralized groups of enamel rods.
(2) They are observed as short, dark projections found near or at the DEJ.
(3) They have no known clinical significance.
g. Enamel lamellae
(1) Small, sheet-like cracks found on the surface of enamel that extend its entire thickness.
(2) Consist of hypocalcified enamel.
(3) The open crack may be filled with organic material from leftover enamel organ components, connective tissues of the developing tooth, or debris from the oral cavity.
(4) Both enamel tufts and lamellae may be likened to geological faults in mature enamel.
h. Enamel spindle
(1) Remnants of odontoblastic processes that become trapped after crossing the DEJ during the differentiation of ameloblasts.
(2) Spindles are more pronounced beneath the cusps or incisal edges of teeth (i.e., areas where occlusal stresses are the greatest).
Amyotrophic lateral sclerosis
General Pathology
Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
a. Characterized by the rapid degeneration of motor neurons in the spinal cord and corticospinal tracts.
b. More common in men in their 50s.
c. Clinically, the disease results in rapidly progressive muscle atrophy due to denervation. Other symptoms include fasciculations, hyperreflexia, spasticity, and pathologic reflexes. Death usually occurs within a few years from onset, usually by respiratory failure or infection.
Oral Habits
PedodonticsClassification of Oral Habits
Oral habits can be classified based on various criteria, including their
nature, impact, and the underlying motivations for the behavior. Below is a
detailed classification of oral habits:
1. Based on Nature of the Habit
Obsessive Habits (Deep Rooted):
International or Meaningful:
Examples: Nail biting, digit sucking, lip biting.
Masochistic (Self-Inflicting):
Examples: Gingival stripping (damaging the gums).
Unintentional (Empty):
Examples: Abnormal pillowing, chin propping.
Non-Obsessive Habits (Easily Learned and Dropped):
Functional Habits:
Examples: Mouth breathing, tongue thrusting, bruxism (teeth
grinding).
2. Based on Impact
Useful Habits:
Habits that may have a positive or neutral effect on oral health.
Harmful Habits:
Habits that can lead to dental issues, such as malocclusion,
gingival damage, or tooth wear.
3. Based on Author Classifications
James (1923):
a) Useful Habits
b) Harmful Habits
Kingsley (1958):
a) Functional Oral Habits
b) Muscular Habits
c) Combined Habits
Morris and Bohanna (1969):
a) Pressure Habits
b) Non-Pressure Habits
c) Biting Habits
Klein (1971):
a) Empty Habits
b) Meaningful Habits
Finn (1987):
I. a) Compulsive Habits
b) Non-Compulsive Habits
II. a) Primary Habits
4. Based on Functionality
Functional Habits:
Habits that serve a purpose, such as aiding in speech or feeding.
Dysfunctional Habits:
Habits that disrupt normal oral function or lead to negative
consequences.
CLINICAL SIGNIFICANCE OF ENZYMES
Biochemistry
CLINICAL SIGNIFICANCE OF ENZYMES
The measurement of enzymes level in serum is applied in diagnostic application
Pancreatic Enzymes
Acute pancreatitis is an inflammatory process where auto digestion of gland was noticed with activation of the certain pancreatic enzymes. Enzymes which involves in pancreatic destruction includes α-amylase, lipase etc.,
1. α-amylase (AMYs) are calcium dependent hydrolyase class of metaloenzyme that catalyzes the hydrolysis of 1, 4- α-glycosidic linkages in polysaccharides. The normal values of amylase is in range of 28-100 U/L. Marked increase of 5 to 10 times the upper reference limit (URL) in AMYs activity indicates acute pancreatitis and severe glomerular impairment.
2. Lipase is single chain glycoprotein. Bile salts and a cofactor called colipase are required for full catalytic activity of lipase. Colipase is secreted by pancreas. Increase in plasma lipase activity indicates acute pancreatitis and carcinoma of the pancreas.
Liver Enzymes
Markers of Hepatocellular Damage
1. Aspartate transaminase (AST) Aspartate transaminase is present in high concentrations in cells of cardiac and skeletal muscle, liver, kidney and erythrocytes. Damage to any of these tissues may increase plasma AST levels.
The normal value of AST for male is <35 U/ L and for female it is <31 U/L.
2. Alanine transaminase (ALT) Alanine transaminase is present at high concentrations in liver and to a lesser extent, in skeletal muscle, kidney and heart. Thus in case of liver damage increase in both AST and ALT were noticed. While in myocardial infarction AST is increased with little or no increase in ALT.
The normal value of ALT is <45 U/L and <34 U/L for male and female respectively
Markers of cholestasis
1. Alkaline phosphatases
Alkaline phosphatases are a group of enzymes that hydrolyse organic phosphates at high pH. They are present in osteoblasts of bone, the cells of the hepatobiliary tract, intestinal wall, renal tubules and placenta.
Gamma-glutamyl-transferase (GGT) Gamma-glutamyl-transferase catalyzes the transfere of the γ–glutamyl group from peptides. The activity of GGT is higher in men than in women. In male the normal value of GGT activity is <55 U/L and for female it is <38 U/L.
2. Glutamate dehydrogenase (GLD) Glutamate dehydrogenase is a mitochondrial enzyme found in liver, heart muscle and kidneys.
Muscle Enzymes
1. Creatine Kinase Creatine kinase (CK) is most abundant in cells of brain, cardiac and skeletal.
2. Lactate Dehydrogenase
Lactate dehydrogenase (LD) catalyses the reversible interconversion of lactate and pyruvate.