NEET MDS Synopsis
Types of Fixed Orthodontic Appliances
OrthodonticsTypes of Fixed Orthodontic Appliances
Braces:
Traditional Metal Braces: Composed of metal
brackets bonded to the teeth, connected by archwires. They are the most
common type of fixed appliance.
Ceramic Braces: Similar to metal braces but made of
tooth-colored or clear materials, making them less visible.
Lingual Braces: Brackets are placed on the inner
surface of the teeth, making them invisible from the outside.
Self-Ligating Braces:
These braces use a specialized clip mechanism to hold the archwire
in place, eliminating the need for elastic or metal ligatures. They can
reduce friction and may allow for faster tooth movement.
Space Maintainers:
Fixed appliances used to hold space for permanent teeth when primary
teeth are lost prematurely. They are typically bonded to adjacent teeth.
Temporary Anchorage Devices (TADs):
Small screws or plates that are temporarily placed in the bone to
provide additional anchorage for tooth movement. They help in achieving
specific movements without unwanted tooth movement.
Palatal Expanders:
Fixed appliances used to widen the upper jaw (maxilla) by applying
pressure to the molars. They are often used in growing patients to
correct crossbites or narrow arches.
Components of Fixed Orthodontic Appliances
Brackets: Small metal or ceramic attachments bonded to
the teeth. They hold the archwire in place and guide tooth movement.
Archwires: Thin metal wires that connect the brackets
and apply pressure to the teeth. They come in various materials and sizes,
and their shape can be adjusted to achieve desired movements.
Ligatures: Small elastic or metal ties that hold the
archwire to the brackets. In self-ligating braces, ligatures are not needed.
Bands: Metal rings that are cemented to the molars to
provide anchorage for the appliance. They may have attachments for brackets
or other components.
Hooks and Accessories: Additional components that can
be attached to brackets or bands to facilitate the use of elastics or other
auxiliary devices.
Indications for Use
Correction of Malocclusions: Fixed appliances are
commonly used to treat various types of malocclusions, including crowding,
spacing, overbites, underbites, and crossbites.
Tooth Movement: They are effective for moving teeth
into desired positions, including tipping, bodily movement, and rotation.
Retention: Fixed retainers may be used after active
treatment to maintain the position of teeth.
Jaw Relationship Modification: Fixed appliances can
help in correcting skeletal discrepancies and improving the relationship
between the upper and lower jaws.
Advantages of Fixed Orthodontic Appliances
Continuous Force Application: Fixed appliances provide
a constant force on the teeth, allowing for more predictable and efficient
tooth movement.
Effective for Complex Cases: They are suitable for
treating a wide range of orthodontic issues, including severe malocclusions
that may not be effectively treated with removable appliances.
Patient Compliance: Since they are fixed, there is no
reliance on patient compliance for wearing the appliance, which can lead to
more consistent treatment outcomes.
Variety of Options: Patients can choose from various
types of braces (metal, ceramic, lingual) based on their aesthetic
preferences.
Disadvantages of Fixed Orthodontic Appliances
Oral Hygiene Challenges: Fixed appliances can make it
more difficult to maintain oral hygiene, increasing the risk of plaque
accumulation, cavities, and gum disease.
Discomfort: Patients may experience discomfort or
soreness after adjustments, especially in the initial stages of treatment.
Dietary Restrictions: Certain foods (hard, sticky, or
chewy) may need to be avoided to prevent damage to the appliances.
Duration of Treatment: Treatment with fixed appliances
can take several months to years, depending on the complexity of the case.
Waxes
Dental Materials
Waxes
Many different waxes are used in dentistry. The composition, form, and color of each wax are designed to facilitate its use and to produce the best possible results.
Applications
o Making impressions
o Registering of tooth or soft tissue positions
o Creating restorative patterns for lab fabrication
o Aiding in laboratory procedures
Classification
a. Pattern waxes-inlay, casting, and baseplate waxes
b. Impression waxes-corrective and biteplate waxes
c. Processing waxes-boxing, utility, and sticky waxes
Types
1) Inlay wax-used to create a pattern for inlay, onlay or crown for subsequent investing and casting in a metal alloy.
2) Casting wax-used to create a pattern for metallic framework for a removable partial denture
3) Baseplate wax-used to establish the vertical dimension. plane of occlusion. and initial arch form of a complete denture
4) Corrective impression wax-used to form a registry pattern of soft tissues on an impression
5) Bite registration wax-used to form a registry pattern for the occlusion of opposing models or casts
6) Boxing wax-used to form a box around an impression before pouring a model or cast
7) Utility wax -soft pliable adhesive wax for modifying appliances, such as alginate impression trays
8) Sticky wax-sticky when melted and used to temporarily adhere pieces of metal or resin in laboratory procedures
Components
a. Base waxes-hydrocarbon (paraffin) ester waxes
b. Modifier waxes-carnauba, ceresin, bees wax, rosin, gum dammar, or microcrystalline waxes
c. Additives-colorants
Reaction-waxes are thermoplastic
Properties
Physical
a. High coefficients of thermal expansion and contraction
b. Insulators and so, cool unevenly; should be waxed in increments to allow heat dissipation
Chemical
a. Degrade prematurely if overheated
b. Designed to degrade into CO2and H2Oduring burnout
Mechanical-stiffness, hardness, and strength depend on modifier waxes used
Time for tooth development
Dental Anatomy
Time for tooth development
Entire primary dentition initiated between 6 and 8 weeks of embryonic development.
Successional permanent teeth initiated between 20th week in utero and 10th month after birth Permanent molars between 20th week in utero (first molar) and 5th year of life (third molar)
Wilson disease
Medicine
- Copper accumulation in liver, brain and eyes (Descemet Membrane = Kayser-Fleischer ring)
- Decreased ceruloplasmin blood levels.
- Chromosome 13, WD gene, ATP7B gene (encondes for Copper transporting ATPase)
- Lesion in basal ganglia, especially putamen
- Tx: penicillamine, zinc acetate.
Symptoms: tremor, asterixis, parkinsonian sx, chorea, neuropsychiatric, fatty changes, hepatitis, cirrhosis.
Best initial test:
Slit-lamp examination for Kayser-Fleischer rings (brown ring around eye due to copper deposition)
Most accurate test:
Penicillamine challenge => abnormal increased amount of urinary copper excreation after Penicillamine.
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.
Ether (diethylether)
Pharmacology
Ether (diethylether)
Ether (diethylether) MAC 2.0%, Blood/gas solubility ratio 15
- Ether is generally mixed with 3% ethanol to retard oxidation. Peroxides form on exposure to air and can enhance the danger of an explosion.
- Slow rate of induction and recovery due to its high blood/gas solubility ratio.
- Produces profound muscular relaxation.
- Both the rate and the minute volume of ventilation tend to be elevated during the inhalation of ether.
- Ether maintains good circulatory stability and does not sensitize the heart to the arrhythmogenic action of catecholamines.
- More than 90% of the absorbed ether can be recovered unchanged in the expired air. Metabolism is not extensive and the metabolites are not hepatotoxic.
- Ether is a versatile anesthetic of unexcelled safety, but it is flammable and irritating to breathe. Secretions can be blocked with anticholinergics.
The Optic Nerve
Anatomy
This is the second cranial nerve (CN II) and is the nerve of sight.
Dental Amalgam and Direct Gold Restorations
Conservative DentistryDental Amalgam and Direct Gold Restorations
In restorative dentistry, understanding the properties of materials and the
techniques used for their application is essential for achieving optimal
outcomes. .
1. Mechanical Properties of Amalgam
Compressive and Tensile Strength
Compressive Strength: Amalgam exhibits high compressive
strength, which is essential for withstanding the forces of mastication. The
minimum compressive strength of amalgam should be at least 310 MPa.
Tensile Strength: Amalgam has relatively low tensile
strength, typically ranging between 48-70 MPa. This characteristic makes it
more susceptible to fracture under tensile forces, which is why proper
cavity design and placement techniques are critical.
Implications for Use
Cavity Design: The design of the cavity preparation
should minimize the risk of tensile forces acting on the restoration. This
can be achieved through appropriate wall angles and retention features.
Restoration Longevity: Understanding the mechanical
properties of amalgam helps clinicians predict the longevity and performance
of the restoration under functional loads.
2. Direct Gold Restorations
Requirements for Direct Gold Restorations
Ideal Surgical Field: A clean and dry field is
essential for the successful placement of direct gold restorations. This
ensures that the gold adheres properly and that contamination is minimized.
Conservative Cavity Preparation: The cavity preparation
must be methodical and conservative, preserving as much healthy tooth
structure as possible while providing adequate retention for the gold.
Systematic Condensation: The condensation of gold must
be performed carefully to build a solid block of gold within the tooth. This
involves using appropriate instruments and techniques to ensure that the
gold is well-adapted to the cavity walls.
Condensation Technique
Building a Solid Block: The goal of the condensation
procedure is to create a dense, solid mass of gold that will withstand
occlusal forces and provide a durable restoration.
3. Gingival Displacement Techniques
Materials for Displacement
To effectively displace the gingival tissue during restorative procedures,
various materials can be used, including:
Heavy Weight Rubber Dam: Provides excellent isolation
and displacement of gingival tissue.
Plain Cotton Thread: A simple and effective method for
gingival displacement.
Epinephrine-Saturated String:
1:1000 Epinephrine: Used for 10 minutes; not
recommended for cardiac patients due to potential systemic effects.
Aluminum Chloride Solutions:
5% Aluminum Chloride Solution: Used for gingival
displacement.
20% Tannic Acid: Another option for controlling
bleeding and displacing tissue.
4% Levo Epinephrine with 9% Potassium Aluminum:
Used for 10 minutes.
Zinc Chloride or Ferric Sulfate:
8% Zinc Chloride: Used for 3 minutes.
Ferric Sub Sulfate: Also used for 3 minutes.
Clinical Considerations
Selection of Material: The choice of material for
gingival displacement should be based on the clinical situation, patient
health, and the specific requirements of the procedure.
4. Condensation Technique for Gold
Force Application
Angle of Condensation: The force of condensation should
be applied at a 45-degree angle to the cavity walls and floor during
malleting. This orientation allows for maximum adaptation of the gold
against the walls, floors, line angles, and point angles of the cavity.
Direction of Force: The forces must be directed at 90
degrees to any previously condensed gold. This technique ensures that the
gold is compacted effectively and that there are no voids or gaps in the
restoration.
Importance of Technique
Adaptation and Density: Proper condensation technique
is critical for achieving optimal adaptation and density of the gold
restoration, which contributes to its longevity and performance.