NEET MDS Synopsis
Relationship Classification
Dental Anatomy
Angle classified these relationships by using the first permanent molars
Normal or neutral occlusion (ideal):
Mesiobuccalgroove of the mandibular first molar align with the mesiobuccal cusp of the max laxy first permanent molar
ClassI malocclusion normal molar relationships with alterations to other characteristics of the occlusion such as versions, crossbites, excessive overjets, or overbites
Class II malocclusion a distal relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary first permanent molar
Division I: protruded maxillary anterior teeth
Division II: one or more maxillary anterior teeth retruded
Class III malocclusion a mesial relation of the mesiobuccal groove of the mandibular first permanent molar to the mesiobuccal cusp of the maxillary molar
Osteonecrosis
General Pathology
Osteonecrosis (Avascular Necrosis)
Ischemic necrosis with resultant bone infarction occurs mostly due to fracture or after corticosteroid use. Microscopically, dead bon trabevulae (characterized by empty lacunae) are interspersed with areas of fat necrosis.
The cortex is usually not affected because of collateral blood supply; in subchondral infarcts, the overlying articular cartilage also remains viable because the synovial fluid can provide nutritional support. With time, osteoclasts can resorb many of the necrotic bony trabeculae; any dead bone fragments that remain act as scaffolds for new bone formation, a process called creeping substitution.
Symptoms depend on the size and location of injury. Subchondral infarcts often collapse and can lead to severe osteoarthritis.
PHARMACOLOGY OF VASOCONSTRICTORS
Pharmacology
PHARMACOLOGY OF VASOCONSTRICTORS
All local anesthetics currently used in dentistry today produce some degree of vasodilatation. This
characteristic results in the increased vascularity of the injected site and results in a shorter duration of local
anesthetic action due enhanced uptake of the local anesthetic into the bloodstream.
- Using a “chemical tourniquet” to prolong the effect of local anesthetics
- The vasoconstrictive action of epinephrine reduces uptake of local anesthetic resulting in a significant increase in the duration of local anesthetic action.
- the addition of vasoconstrictors in local anesthetic solutions will:
1. Prolong the effect of the local anesthetic
2. Increase the depth of anesthesia
3. Reduces the plasma concentration of the local anesthetic
4. Reduces the incidence of systemic toxicity
5. Reduces bleeding at surgical site
Local anesthetics containing epinephrine produce:
1. Localized
VASOCONSTRICTION MEDIATED BY ALPHA RECEPTOR ACTIVATION
i. Hemostasis at surgical site
ii. Ischemia of localized tissue
2. Systemic
HEART
i. Increased heart rate (β1)
ii. Increased force and rate of contraction (β 1)
iii. Increased cardiac output
iv. Increases oxygen demand
v. Dilation of coronary arteries
vi. Decreases threshold for arrhythmias
LUNGS
i. Bronchodilation (β2 )
SKELETAL MUSCLE
i. Predominately vasodilation (fight or flight response) (β 2 )
CNS
i. Minimal direct effect due to difficulty in crossing the blood-brain barrier. Most effects on the CNS are manifestations of the vasoconstrictor on other organs such as the heart.
Concentrations of vasoconstrictors
1. Epinephrine The most commonly used epinephrine dilution in dentistry today is 1:100000. However it appears that a 1:200000 concentration is comparable in effect to the 1:100000 concentration.
2. Levonordefrin Levonordefrin is a synthetic compound very similar in structure to epinephrine. It is the only alternate choice of vasoconstrictor to epinephrine. It is prepared as a 1:20000 (0.05mg/ml)(50 mcg/ml) concentration with 2 % mepivacaine.
Cardiovascular considerations
The plasma concentration of epinephrine in a patient at rest is 39 pg/ml.1 The injection of 1 cartridge of lidocaine 1:100000 epinephrine intraorally results in a doubling of the plasma concentration of epinephrine.
The administration of 15 mcg of epinephrine increased heart rate an average of 25 beats/min with some individuals experiencing an increase of 70 beats/min.
Clinical considerations
It is well documented that reduced amounts of epinephrine should be administered to patients with:
HEART DISEASE (ANGINA HISTORYOF MI)
POORLY CONTROLLED HIGH BLOOD PRESSURE
It is generally accepted that the dose of epinephrine should be limited to 0.04 mg (40 mcg) for patients that have these medical diagnoses
Cardiac Conduction
Physiology
A small fraction of cardiac muscle fibers have myogenicity and autorhythmicity.
Myogenicity is the property of spontaneous impulse generation. The slow sodium channels are leaky and cause the polarity to spontaneously rise to threshold for action potential generation. The fastest of these cells, those in the SA node, set the pace for the heartbeat.
Autorhythmicity - the natural rhythm of spontaneous depolarization. Those with the fastest autorhythmicity act as the 1. heart's pacemaker.
Contractility - like skeletal muscle, most cardiac muscle cells respond to stimuli by contracting. The autorhythmic cells have very little contractility however. Contractility in the other cells can be varied by the effect of neurotransmitters.
Inotropic effects - factors which affect the force or energy of muscular contractions. Digoxin, epinephrine, norepinephrine, and dopamine have positive inotropic effects. Betal blockers and calcium channel blockers have negative inotropic effects
Sequence of events in cardiac conduction: The electrical events in the cardiac cycle.
1) SA node depolarizes and the impulse spreads across the atrial myocardium and through the internodal fibers to the AV node. The atrial myocardium depolarizes resulting in atrial contraction, a physical event.
2) AV node picks up the impulse and transfers it to the AV Bundle (Bundle of His). This produces the major portion of the delay seen in the cardiac cycle. It takes approximately .03 sec from SA node depolarization to the impulse reaching the AV node, and .13 seconds for the impulse to get through the AV node and reach the Bundle of His. Also during this period the atria repolarize.
3) From the AV node the impulse travels through the bundle branches and through the Purkinje fibers to the ventricular myocardium, causing ventricular depolarization and ventricular contraction, a physical event.
4) Ventricular repolarization occurs.
CELL ORGANELLES
General Microbiology
CELLS ORGANELLES
Cell parts:
Mitochondrion – double MB structure responsible for cellular metabolism – powerhouse of the cell
Nucleus – controls synthetic activities and stores genetic information
Ribosome – site of mRNA attachment and amino acid assembly, protein synthesis
Endoplasmic reticulum – functions in intracellular transportation
Gogli apparatus/complex – composed of membranous sacs – involved in production of large CHO molecules & lysosomes
Lysosome – organelle contains hydrolytic enzymes necessary for intracellular digestion
Membrane bag containing digestive enzymes
Cellular food digestion – lysosome MB fuses w/ MB of food vacuole & squirts the enzymes inside. Digested food diffuses through the vacuole MB to enter the cell to be used for energy or growth. Lysosome MB keeps the cell iself from being digested
-Involved mostly in cells that like to phagocytose
-Involved in autolytic and digestive processes
-Formed when the Golgi complex packages up an especially large vesicle of digestive enzyme proteins
Phagosome
– vesicle that forms around a particle (bacterial or other) w/in the phagocyte that engulfed it
- Then separates from the cell membrane bag & fuses w/ lysozome to receive contents
- This coupling forms phagolysosomes in which digestion of the engulfed particle occurs
Microbodies:
- Contain catalase
- Bounded by a single membrane bag
- Compartments specialized for specific metabolic pathways
- Similar in function to lysosomes, but are smaller & isolate metabolic reactions involving H2O2
- Two general families:
· Peroxisomes: transfer H2 to O2, producing H2O2 – generally not found in plants
· Glyoxysomes: common in fat-storing tissues of the germinating seeds of plants
¨ Contain enzymes that convert fats to sugar to make the energy stored in the oils of the seed available
Inclusions
– transitory, non-living metabolic byproducts found in the cytoplasm of the cell
- May appear as fat droplets, CHO accumulations, or engulfed foreign matter.
Angle’s Classification of Malocclusion
Orthodontics
Angle’s Classification of Malocclusion
Malocclusion refers to the misalignment or incorrect relationship between the
teeth of the two dental arches when they come into contact as the jaws close.
Understanding occlusion is essential for diagnosing and treating orthodontic
issues.
Definitions
Occlusion: The contact between the teeth in the
mandibular arch and those in the maxillary arch during functional relations
(Wheeler’s definition).
Malocclusion: A condition characterized by a deflection
from the normal relation of the teeth to other teeth in the same arch and/or
to teeth in the opposing arch (Gardiner, White & Leighton).
Importance of Classification
Classifying malocclusion serves several purposes:
Grouping of Orthodontic Problems: Helps in identifying
and categorizing various orthodontic issues.
Location of Problems: Aids in pinpointing specific
areas that require treatment.
Diagnosis and Treatment Planning: Facilitates the
development of effective treatment strategies.
Self-Communication: Provides a standardized language
for orthodontists to discuss cases.
Documentation: Useful for recording and tracking
orthodontic problems.
Epidemiological Studies: Assists in research and
studies related to malocclusion prevalence.
Assessment of Treatment Effects: Evaluates the
effectiveness of orthodontic appliances.
Normal Occlusion
Molar Relationship
According to Angle, normal occlusion is defined by the relationship of the
mesiobuccal cusp of the maxillary first molar aligning with the buccal groove of
the mandibular first molar.
Angle’s Classification of Malocclusion
Edward Angle, known as the father of modern orthodontics, first published his
classification in 1899. The classification is based on the relationship of the
mesiobuccal cusp of the maxillary first molar to the buccal groove of the
mandibular first molar. It is divided into three classes:
Class I Malocclusion (Neutrocclusion)
Definition: Normal molar relationship is present, but
there may be crowding, misalignment, rotations, cross-bites, and other
irregularities.
Characteristics:
Molar relationship is normal.
Teeth may be crowded or rotated.
Other alignment irregularities may be present.
Class II Malocclusion (Distocclusion)
Definition: The lower molar is positioned distal to the
upper molar.
Characteristics:
Often results in a retrognathic facial profile.
Increased overjet and overbite.
The mesiobuccal cusp of the maxillary first molar occludes anterior
to the buccal groove of the mandibular first molar.
Subdivisions of Class II Malocclusion:
Class II Division 1:
Class II molars with normally inclined or proclined maxillary
central incisors.
Class II Division 2:
Class II molars with retroclined maxillary central incisors.
Class III Malocclusion (Mesiocclusion)
Definition: The lower molar is positioned mesial to the
upper molar.
Characteristics:
Often results in a prognathic facial profile.
Anterior crossbite and negative overjet (underbite).
The mesiobuccal cusp of the upper first molar falls posterior to the
buccal groove of the lower first molar.
Advantages of Angle’s Classification
Comprehensive: It is the first comprehensive
classification and is widely accepted in the field of orthodontics.
Simplicity: The classification is straightforward and
easy to use.
Popularity: It is the most popular classification
system among orthodontists.
Effective Communication: Facilitates clear
communication regarding malocclusion.
Disadvantages of Angle’s Classification
Limited Plane Consideration: It primarily considers
malocclusion in the anteroposterior plane, neglecting transverse and
vertical dimensions.
Fixed Reference Point: The first molar is considered a
fixed point, which may not be applicable in all cases.
Not Applicable for Deciduous Dentition: The
classification does not effectively address malocclusion in children with
primary teeth.
Lack of Distinction: It does not differentiate between
skeletal and dental malocclusion.
Muscles
PhysiologyThere are three types of muscle tissue, all of which share some common properties:
Excitability or responsiveness - muscle tissue can be stimulated by electrical, physical, or chemical means.
contractility - the response of muscle tissue to stimulation is contraction, or shortening.
elasticity or recoil - muscles have elastic elements (later we will call these their series elastic elements) which cause them to recoil to their original size.
stretchability or extensibility - muscles can also stretch and extend to a longer-than-resting length.
The three types of muscle: skeletal, cardiac, and visceral (smooth) muscle.
Skeletal muscle
It is found attached to the bones for movement.
cells are long multi-nucleated cylinders.
The cells may be many inches long but vary in diameter, averaging between 100 and 150 microns.
All the cells innervated by branches from the same neuron will contract at the same time and are referred to as a motor unit.
Skeletal muscle is voluntary because the neurons which innervate it come from the somatic or voluntary branch of the nervous system.
That means you have willful control over your skeletal muscles.
Skeletal muscles have distinct stripes or striations which identify them and are related to the organization of protein myofilaments inside the cell.
Cardiac muscle
This muscle found in the heart.
It is composed of much shorter cells than skeletal muscle which branch to connect to one another.
These connections are by means of gap junctions called intercalated disks which allow an electrochemical impulse to pass to all the connected cells.
This causes the cells to form a functional network called a syncytium in which the cells work as a unit. Many cardiac muscle cells are myogenic which means that the impulse arises from the muscle, not from the nervous system. This causes the heart muscle and the heart itself to beat with its own natural rhythm.
But the autonomic nervous system controls the rate of the heart and allows it to respond to stress and other demands. As such the heart is said to be involuntary.
Visceral muscle is found in the body's internal organs and blood vessels.
It is usually called smooth muscle because it has no striations and is therefore smooth in appearance. It is found as layers in the mucous membranes of the respiratory and digestive systems.
It is found as distinct bands in the walls of blood vessels and as sphincter muscles.
Single unit smooth muscle is also connected into a syncytium similar to cardiac muscle and is also partly myogenic. As such it causes continual rhythmic contractions in the stomach and intestine. There and in blood vessels smooth muscle also forms multiunit muscle which is stimulated by the autonomic nervous system. So smooth muscle is involuntary as well
Hepatitis
General Pathology
Hepatitis
Hepatitis viruses—this group of viruses causes hepatitis, a disease affecting the liver.
1. General characteristics of hepatitis.
a. The general presentation of hepatitis is the same regardless of the infecting virus; however, the time and severity of symptoms may differ.
b. Symptoms of hepatitis include fever, anorexia, malaise, nausea, jaundice, and brown-colored urine.
c. Complications of a hepatitis infection include cirrhosis, liver failure, and hepatorenal failure.