NEET MDS Synopsis
First Generation Cephalosporins
Pharmacology
First Generation Cephalosporins
Prototype Drugs are CEFAZOLIN (for IV use) and CEPHALEXIN (oral use).
1. Staph. aureus - excellent activity against b-lactamase-producing strains
Not effective against methicillin-resistant Staph. aureus & epidermidis
2. Streptococci - excellent activity versus Streptococcus sp.
Not effective against penicillin-resistant Strep. pneumoniae
3. Other Gm + bacteria - excellent activity except for Enterococcus sp.
4. Moderate activity against gram negative bacteria.
Caution: resistance may occur in all cases.
Susceptible organisms include:
E. coli
Proteus mirabilis
Indole + Proteus sp. (many strains resistant)
Haemophilus influenzae (some strains resistant)
Neisseria sp. (some gonococci resistant)
Uses
1. Upper respiratory tract infections due to Staph. and Strep.
2. Lower respiratory tract infections due to susceptible bacteria e.g. Strep.pneumoniae in penicillin-allergic patient (previous rash)
3. Uncomplicated urinary tract infections (Cephalexin)
4. Surgical prophylaxis for orthopedic and cardiovascular operations (cefazolin preferred because of longer half-life)
5. Staphylococcal infections of skin and skin structure
Frenectomy
Oral and Maxillofacial SurgeryFrenectomy- Overview and Techniques
A frenectomy is a surgical procedure that involves the
removal of a frenum, which is a thin band of fibrous tissue that connects the
lip or tongue to the underlying alveolar mucosa. This procedure is often
performed to address issues related to abnormal frenal attachments that can
cause functional or aesthetic problems.
Key Features of Frenal Attachment
A frenum consists of a thin band of fibrous tissue and a few muscle
fibers, covered by mucous membrane. It serves to anchor the lip or
tongue to the underlying structures.
Common Locations:
Maxillary Midline Frenum: The most commonly
encountered frenum, located between the central incisors in the upper
jaw.
Lingual Frenum: Found under the tongue; its
attachment can vary in length and thickness among individuals.
Maxillary and Mandibular Frena: These can also be
present in the premolar and molar areas, potentially affecting oral
function and hygiene.
Indications for Frenectomy
Functional Issues: An overly tight or thick frenum can
restrict movement of the lip or tongue, leading to difficulties in speech,
eating, or oral hygiene.
Aesthetic Concerns: Prominent frena can cause spacing
issues between teeth or affect the appearance of the smile.
Orthodontic Considerations: In some cases, frenectomy
may be performed prior to orthodontic treatment to facilitate tooth movement
and prevent relapse.
Surgical Techniques
Z-Plasty Procedure:
Indication: Used when the frenum is broad and the
vestibule (the space between the lip and the gums) is short.
Technique: This method involves creating a Z-shaped
incision that allows for the repositioning of the tissue, effectively
lengthening the vestibule and improving the functional outcome.
V-Y Incision:
Indication: Employed for lengthening a localized
area, particularly when the frenum is causing tension or restriction.
Technique: A V-shaped incision is made, and the
tissue is then sutured in a Y configuration, which helps to lengthen the
frenum and improve mobility.
Postoperative Care
Pain Management: Patients may experience discomfort
following the procedure, which can be managed with analgesics.
Oral Hygiene: Maintaining good oral hygiene is crucial
to prevent infection at the surgical site.
Resin Modified GIC
Conservative DentistryResin Modified Glass Ionomer Cements (RMGIs)
Resin Modified Glass Ionomer Cements (RMGIs) represent a significant
advancement in dental materials, combining the beneficial properties of both
glass ionomer cements and composite resins. This overview will discuss the
composition, advantages, and disadvantages of RMGIs, highlighting their role in
modern dentistry.
1. Composition of Resin Modified Glass Ionomer Cements
A. Introduction
First Introduced: RMGIs were first introduced as
Vitrebond (3M), utilizing a powder-liquid system designed to enhance the
properties of traditional glass ionomer cements.
B. Components
Powder: The powder component consists of fluorosilicate
glass, which provides the material with its glass ionomer properties. It
also contains a photoinitiator or chemical initiator to facilitate setting.
Liquid: The liquid component contains:
15 to 25% Resin Component: Typically in the form of
Hydroxyethyl Methacrylate (HEMA), which enhances the material's bonding
and aesthetic properties.
Polyacrylic Acid Copolymer: This component
contributes to the chemical adhesion properties of the cement.
Photoinitiator and Water: These components are
essential for the setting reaction and workability of the material.
2. Advantages of Resin Modified Glass Ionomer Cements
RMGIs offer a range of benefits that make them suitable for various dental
applications:
Extended Working Time: RMGIs provide a longer working
time compared to traditional glass ionomers, allowing for more flexibility
during placement.
Control on Setting: The setting reaction can be
controlled through light curing, which allows for adjustments before the
material hardens.
Good Adaptation: RMGIs exhibit excellent adaptation to
tooth structure, which helps minimize gaps and improve the seal.
Chemical Adhesion to Enamel and Dentin: RMGIs bond
chemically to both enamel and dentin, enhancing retention and reducing the
risk of microleakage.
Fluoride Release: Like traditional glass ionomers, RMGIs
release fluoride, which can help in the prevention of secondary caries.
Improved Aesthetics: The resin component allows for
better color matching and aesthetics compared to conventional glass
ionomers.
Low Interfacial Shrinkage Stress: RMGIs exhibit lower
shrinkage stress upon setting compared to composite resins, reducing the
risk of debonding or gap formation.
Superior Strength Characteristics: RMGIs generally have
improved mechanical properties, making them suitable for a wider range of
clinical applications.
3. Disadvantages of Resin Modified Glass Ionomer Cements
Despite their advantages, RMGIs also have some limitations:
Shrinkage on Setting: RMGIs can experience some degree
of shrinkage during the setting process, which may affect the marginal
integrity of the restoration.
Limited Depth of Cure: The depth of cure can be limited,
especially when using more opaque lining cements. This can affect the
effectiveness of the material in deeper cavities.
Respiratory Viral Diseases
General Pathology
Respiratory Viral Diseases
Respiratory viral infections cause acute local and systemic illnesses. The common cold, influenza, pharyngitis, laryngitis (including croup), and tracheobronchitis are common.
An acute, usually afebrile, viral infection of the respiratory tract, with inflammation in any or all airways, including the nose, paranasal sinuses, throat, larynx, and sometimes the trachea and bronchi.
Etiology and Epidemiology
Picornaviruses, especially rhinoviruses and certain echoviruses and coxsackieviruses, cause the common cold. About 30 to 50% of all colds are caused by one of the > 100 serotypes of rhinoviruses.
Symptoms and Signs
Clinical symptoms and signs are nonspecific.
After an incubation period of 24 to 72 h, onset is abrupt, with a burning sensation in the nose or throat, followed by sneezing, rhinorrhea, and malaise.
Characteristically, fever is not present, particularly with a rhinovirus or coronavirus. Pharyngitis usually develops early; laryngitis and tracheobronchitis vary by person and causative agent. Nasal secretions are watery and profuse during the first days, but become more mucoid and purulent.
Cough is usually mild but often lasts into the 2nd wk.
Stainless Steel Crowns
PedodonticsStainless Steel Crowns
Stainless steel crowns (SSCs) are a common restorative option for primary
teeth, particularly in pediatric dentistry. They are especially useful for teeth
with extensive carious lesions or structural damage, providing durability and
protection for the underlying tooth structure.
Indications for Stainless Steel Crowns
Primary Incisors or Canines:
SSCs are indicated for primary incisors or canines that have
extensive proximal lesions, especially when the incisal portion of the
tooth is involved.
They are particularly beneficial in cases where traditional
restorative materials (like amalgam or composite) may not provide
adequate strength or longevity.
Crown Selection and Preparation
Crown Selection:
An appropriate size of stainless steel crown is selected based on
the dimensions of the tooth being restored.
Contouring:
The crown is contoured at the cervical margin to ensure a proper fit
and to minimize the risk of gingival irritation.
Polishing:
The crown is polished to enhance its surface finish, which can help
reduce plaque accumulation and improve esthetics.
Cementation:
The crown is cemented into place using a suitable dental cement,
ensuring a secure fit even on teeth that have undergone significant
carious structure removal.
Advantages of Stainless Steel Crowns
Retention:
SSCs provide excellent retention and can remain in place even when
extensive portions of carious tooth structure have been removed.
Durability:
They are highly durable and can withstand the forces of mastication,
making them ideal for primary teeth that are subject to wear and tear.
Esthetic Considerations
Esthetic Limitations:
One of the drawbacks of stainless steel crowns is their metallic
appearance, which may not meet the esthetic requirements of some
children and their parents.
Open-Face Stainless Steel Crowns:
To address esthetic concerns, a technique known as the open-face
stainless steel crown can be employed.
In this technique, most of the labial metal of the crown is cut
away, creating a labial "window."
This window is then restored with composite resin, allowing for a
more natural appearance while still providing the strength and
durability of the stainless steel crown.
Theories Regarding the Mineralization of Dental Calculus
PeriodontologyTheories Regarding the Mineralization of Dental Calculus
Dental calculus, or tartar, is a hard deposit that forms on teeth due to the
mineralization of dental plaque. Understanding the mechanisms by which plaque
becomes mineralized is essential for dental professionals in managing
periodontal health. The theories regarding the mineralization of calculus can be
categorized into two main mechanisms: mineral precipitation and the role of
seeding agents.
1. Mineral Precipitation
Mineral precipitation involves the local rise in the saturation of calcium
and phosphate ions, leading to the formation of calcium phosphate salts. This
process can occur through several mechanisms:
A. Rise in pH
Mechanism: An increase in the pH of saliva can lead to
the precipitation of calcium phosphate salts by lowering the precipitation
constant.
Causes:
Loss of Carbon Dioxide: Bacterial activity in
dental plaque can lead to the loss of CO2, resulting in an increase in
pH.
Formation of Ammonia: The degradation of proteins
by plaque bacteria can produce ammonia, further elevating the pH.
B. Colloidal Proteins
Mechanism: Colloidal proteins in saliva bind calcium
and phosphate ions, maintaining a supersaturated solution with respect to
calcium phosphate salts.
Process:
When saliva stagnates, these colloids can settle out, disrupting the
supersaturated state and leading to the precipitation of calcium
phosphate salts.
C. Enzymatic Activity
Phosphatase:
This enzyme, released from dental plaque, desquamated epithelial
cells, or bacteria, hydrolyzes organic phosphates in saliva, increasing
the concentration of free phosphate ions and promoting mineralization.
Esterase:
Present in cocci, filamentous organisms, leukocytes, macrophages,
and desquamated epithelial cells, esterase can hydrolyze fatty esters
into free fatty acids.
These fatty acids can form soaps with calcium and magnesium, which
are subsequently converted into less-soluble calcium phosphate salts,
facilitating calcification.
2. Seeding Agents and Heterogeneous Nucleation
The second theory posits that seeding agents induce small foci of
calcification that enlarge and coalesce to form a calcified mass. This concept
is often referred to as the epitactic concept or heterogeneous
nucleation.
A. Role of Seeding Agents
Unknown Agents: The specific seeding agents involved in
calculus formation are not fully understood, but it is believed that the
intercellular matrix of plaque plays a significant role.
Carbohydrate-Protein Complexes:
These complexes may initiate calcification by chelating calcium from
saliva and binding it to form nuclei that promote the deposition of
minerals.
Clinical Implications
Understanding Calculus Formation:
Knowledge of the mechanisms behind calculus mineralization can help
dental professionals develop effective strategies for preventing and
managing calculus formation.
Preventive Measures:
Maintaining good oral hygiene practices can help reduce plaque
accumulation and the conditions that favor mineralization, such as
stagnation of saliva and elevated pH.
Treatment Approaches:
Understanding the role of enzymes and proteins in calculus formation
may lead to the development of therapeutic agents that inhibit
mineralization or promote the dissolution of existing calculus.
Research Directions:
Further research into the specific seeding agents and the
biochemical processes involved in calculus formation may provide new
insights into preventing and treating periodontal disease.
VITAMIN C
Biochemistry
VITAMIN C: ASCORBIC ACID, ASCORBATE
Vitamin C benefits the body by holding cells together through collagen synthesis; collagen is a connective tissue that holds muscles, bones, and other tissues together. Vitamin C also aids in wound healing, bone and tooth formation, strengthening blood vessel walls, improving immune system function, increasing absorption and utilization of iron, and acting as an antioxidant.
RDA The Recommended Dietary Allowance (RDA) for Vitamin C is 90 mg/day for adult males and 75 mg/day for adult females
Vitamin C Deficiency
Severe vitamin C deficiency result in the disease known as scurvy, causing a loss of collagen strength throughout the body. Loss of collagen results in loose teeth, bleeding and swollen gums, and improper wound healing.
Lamotrigine
Pharmacology
Lamotrigine (Lamictal): newer; broad spectrum (for most seizure types)
Mechanism: ↓ reactivation of Na channels (↑ refractory period, blocks high frequency cell firing)
Side effects: dizziness, ataxia, fatigue, nausea, no significant drug interactions