NEET MDS Synopsis
Epoxy Resin Sealers Composition in Endodontics
EndodonticsEpoxy resin sealers are widely used in endodontics due to their favorable
properties, including excellent sealing ability, biocompatibility, and
resistance to washout. Understanding their composition is crucial for dental
professionals to select the appropriate materials for root canal treatments.
Here’s a detailed overview of the composition of epoxy resin sealers used in
endodontics.
Key Components of Epoxy Resin Sealers
Base Component
Polyepoxy Resins:
The primary component that provides the sealing properties. These
resins are known for their strong adhesive qualities and dimensional
stability.
Commonly used polyepoxy resins include diglycidyl ether of bisphenol
A (DGEBA).
Curing Agent
Amine-Based Curing Agents:
These agents initiate the curing process of the epoxy resin, leading
to the hardening of the material.
Examples include triethanolamine (TEA) and other amine compounds
that facilitate cross-linking of the resin.
Fillers
Inorganic Fillers:
Materials such as zirconium oxide and calcium oxide are often added
to enhance the physical properties of the sealer, including
radiopacity and strength.
Fillers can also improve the flowability of the sealer, allowing it
to fill irregularities in the canal system effectively.
Plasticizers
Additives:
Plasticizers may be included to improve the flexibility and
workability of the sealer, making it easier to manipulate during
application.
Antimicrobial Agents
Incorporated Compounds:
Some epoxy resin sealers may contain antimicrobial agents to help
reduce bacterial load within the root canal system, promoting
healing and preventing reinfection.
Examples of Epoxy Resin Sealers
AH-Plus
Composition:
Contains a polyepoxy resin base, amine curing agents, and inorganic
fillers.
Properties:
Known for its excellent sealing ability, low solubility, and good
adhesion to dentin.
AD Seal
Composition:
Similar to AH-Plus, with a focus on enhancing flowability and
reducing cytotoxicity.
Properties:
Offers good sealing properties and is used in various clinical
situations.
EndoSeal MTA
Composition:
Combines epoxy resin with bioceramic materials, providing additional
benefits such as bioactivity and improved sealing.
Properties:
Known for its favorable physicochemical properties and
biocompatibility.
Clinical Implications
Selection of Sealers: The choice of epoxy resin sealer should be
based on the specific clinical situation, considering factors such as the
complexity of the canal system, the need for antimicrobial properties, and
the desired setting time.
Application Techniques: Proper mixing and application techniques
are essential to ensure optimal performance of the sealer, including
achieving a fluid-tight seal and preventing voids.
Conclusion
Epoxy resin sealers are composed of a combination of polyepoxy resins, curing
agents, fillers, and additives that contribute to their effectiveness in
endodontic treatments. Understanding the composition and properties of these
sealers allows dental professionals to make informed decisions, ultimately
enhancing the success of root canal therapy.
Here are some notable epoxy resin sealers used in endodontics, along with their
key features:
1. AH
Plus
Description: A widely used epoxy resin-based root canal sealer.
Properties:
Excellent sealing ability.
High biocompatibility.
Good adhesion to gutta-percha and dentin.
Uses: Suitable for permanent root canal fillings.
2. Dia-ProSeal
Description: A two-component epoxy resin-based system.
Properties:
Low shrinkage and high adhesion.
Outstanding flow characteristics.
Antimicrobial activity due to the addition of calcium hydroxide.
Uses: Effective for sealing lateral canals and suitable for warm
gutta-percha techniques.
3. Vioseal
Description: An epoxy resin-based root canal sealer available in a
dual syringe format.
Properties:
Good flowability and sealing properties.
Radiopaque for easy identification on radiographs.
Uses: Used for permanent root canal fillings.
4. AH
Plus Jet
Description: A variant of AH Plus that features an auto-mixing
system.
Properties:
Consistent mixing and application.
Excellent sealing and adhesion properties.
Uses: Ideal for various endodontic applications.
5. EndoREZ
Description: A resin-based sealer that combines epoxy and
methacrylate components.
Properties:
High bond strength and low solubility.
Good flow and adaptability to canal irregularities.
Uses: Suitable for permanent root canal fillings, especially in
complex canal systems.
6. Resilon
Description: A thermoplastic synthetic polymer-based root canal
filling material that can be used with epoxy resin sealers.
Properties:
Provides a monoblock effect with the sealer.
Excellent sealing ability and biocompatibility.
Uses: Used in conjunction with epoxy resin sealers for enhanced
sealing.
Conclusion
Epoxy resin sealers are essential in endodontics for achieving effective and
durable root canal fillings. The choice of sealer may depend on the specific
clinical situation, the complexity of the canal system, and the desired
properties for optimal sealing and biocompatibility.
Root Formation and Obliteration
Dental Anatomy
Root Formation and Obliteration
1. In general, the root of a deciduous tooth is completely formed in just about one year after eruption of that tooth into the mouth.
2. The intact root of the deciduous tooth is short lived. The roots remain fully formed only for about three years.
3. The intact root then begins to resorb at the apex or to the side of the apex, depending on the position of the developing permanent tooth bud.
4. Anterior permanent teeth tend to form toward the lingual of the deciduous teeth, although the canines can be the exception. Premolar teeth form between the roots of the deciduous molar teeth
Benzodiazepines
Pharmacology
Benzodiazepines (BZ):
newer; depress CNS, selective anxiolytic effect (no sedative effect); are not general anesthetics (but does produce sedation, stupor) or analgesics
BZ effects:
1. Central: BZs bind GABAA receptors in limbic system (amygdala, septum, hippocampus; involved in emotions) and enhance inhibition of neurons in limbic system (this may produce anxiolytic effects of BZs)
a. GABA receptor: pentameric (α, β, δ, γ subunits)
i. Binding sites: GABA (↑ conductance (G) of Cl-, hyperpolarization, inhibition), barbiturate (↑ GABA effect), benzodiazepine (↑ GABA effect), picrotoxin (block Cl channel)
b. GABA agonists: GABA (binds GABA → Cl influx; have ↑ frequency of Cl channel opening; BZs alone- without GABA don’t affect Cl channel function)
c. Antagonists: bicuculline (competitively blocks GABA binding; ↓ inhibition,→ convulsions; no clinical use), picrotoxin (non-competitively blocks GABA actions, Cl channel → ↓ inhibition → convulsions)
2. Other agents at BZ receptor:
a. Agonists: zolpidem (acts at BZ receptor to produce pharmacological actions)
b. Inverse agonists: β-carbolines (produce opposite effects at BZ binding site-- ↓ Cl conductance; no therapeutic uses since → anxiety, irritability, agitation, delirium, convulsions)
3. Antagonists: flumazenil (block agonists and inverse agonists, have no biological effects themselves; can precipitate withdrawal in dependent people)
Metabolism: many BZs have very long action (since metabolism is slow); drugs have active metabolites
2 major reactions: demethylation and hydroxylation (both very slow reactions)
Fast reaction: glucuronidation and urinary excretion
Plasma half life: long (for treating anxiety, withdrawal, muscle relaxants), intermediate (insomnia, anxiety), short (insomnia), ultra-short (<2hrs; pre-anesthetic medication)
Acute toxicity: very high therapeutic index and OD usually not life threatening (rarely see coma or death)
Treatment: support respiration, BP, gastric lavage, give antagonist (e.g., glumazenil; quickly reverses BD-induced respiratory depression)
Tolerance: types include pharmacodynamic (down-regulation of CNS response due to presence of drug; this is probably the mechanism by which tolerance develops), cross-tolerance (with other BZ and CNS depressants like EtOH and BARBS), acquisition of tolerance (tolerance develops fastest in anticonvulsant > sedation >> muscle relaxant > antianxiety; means people can take BZs for long time for antianxiety without → tolerance)
Physical dependence: low abuse potential (no buz) but physical/psychological dependence may occur; physical dependence present when withdrawal symptoms occur (mild = anxiety, insomnia, irritability, bad dreams, tremors, anorexia; severe = agitation, depression, panic, paranoia, muscle twitches, convulsions)
Drug interactions: minimally induce liver enzymes so few interactions; see additive CNS depressant effects (can be severe and → coma and death if BZs taken with other CNS depressants like ethanol)
Histamine
Pharmacology
Histamine:
Involved in inflammatory and anaphylactic reactions
Local application causes swelling redness, and edema, mimicking a mild inflammatory reaction.
Large systemic doses leads to profound vascular changes similar to those seen after shock or anaphylactic origin.
Storage: widely distributed; in tissues, primarily in mast cells; in blood- in basophils, platelets; non-mast cell sites (epidermis, CNS, regenerating cells)
Histamine Stored in complex with:
Heparin
Chondroitin Sulfate
Eosinophilic Chemotactic Factor
Neutrophilic Chemotactic Factor
Proteases
Release: during type I (IgE-mediated) immediate hypersensitivity rxns, tissue injury, in response to some drugs
a. Process: Fcε receptor on mast cell or basophil binds IgE, when Ag binds → ↑ PLC activity → histamine
Symptoms: bronchoconstriction, ↓ Pa, ↑ capillary permeability, edema
Action
H1 receptors are located mainly on smooth muscle cells in blood vessels and the respiratory and GI tracts. When histamine binds with these receptors producing the following effects.
-Contraction of smooth muscle in the bronchi and bronchioles producing bronchoconstraction.
-stimulation of vagus nerve endings to produce reflex bronchoconstraction and cough.
-Increased permeability of veins and capillaries, which allows fluid to flow into subcutaneous tissues and form edema (little lower blood pressure).
-Increased secretion of mucous glands. Mucosal edema and increased nasal mucus produce the nasal congestion characteristic of allergic rhinitis and the common cold.
-Stimulation of sensory peripheral nerve endings to cause pain and pruritus.
Histamine promotes vasodilation by causing vascular endothelium to release nitric oxide. This chemical signal diffuses to the vascular smooth muscle, where it stimulates cyclic guanosine monophosphate production, causing vasodilation.
H2-receptors present mostly in gastric glands and smooth muscle of some blood vessels. When receptors are stimulated, the main effects are increased secretion of gastric acid and pepsin, increased rate and force of myocardial contraction.
The H3-receptor functions as a negative-feedback mechanism to inhibit histamine synthesis and release in many body tissues. Stimulation of H3 receptors opposes the effects produced by stimulation of H1 receptors.
The H4- receptor is expressed in only a few cell types, and their role in drug action is unclear.
Drugs cause release of histamine:
Many drugs can cause release of histamine in the body.
-Intracutaneouse morphine injection in humans produced localized redness, localized edema and a diffuse redness. This is due to release of histamine.
-I.V. inj of curare may cause bronchial constriction due to release of histamine.
-codeine , papaverine, meperidine (pethedine), atropine, hydralizine and sympathomimetic amines, histamine releases by these drugs may not be significant unless they are administered I.V in large doses
Pharmacological effects
- If injected I.V. (0.1 mg of histamine) causes a sharp decline in the blood pressure, flushing of the face and headache.
- There is also stimulation of gastric acid secretion.
- If this injection is given to an asthmatic individual, there will be a marked decrease in vital capacity and a sever attack of asthma.
Circulatory effects of histamine:
The two factors involved in the circulatory action of histamine are:
Arteriolar dilatation and
Capillary permeability
So it leads to loss of plasma from circulation
Effect on gastric secretion:
Histamine is a potent stimulant of gastric Hcl secretion.
Prenatal Counseling
Pedodontics Prenatal Counseling for Dental Health
Prenatal counseling is a crucial aspect of establishing a child's dental
preventive program. Initiating this process before the birth of the child allows
parents to prepare for their child's health and well-being effectively. This
period is particularly significant for first-time parents, as they are often
more receptive to health recommendations and eager to learn how to provide the
best care for their child.
Importance of Prenatal Counseling
Timing: The best time to begin counseling is during
pregnancy, as expectant parents are highly motivated to learn about health
practices that will benefit their child.
Parental Awareness: Expectant parents become acutely
aware of their child's dependence on them for nurturing and health care,
fostering a strong instinct to provide the best possible environment for
their child.
Key Counseling Topics
Parental Hygiene Habits:
Role Modeling: Parents should be encouraged to
adopt good oral hygiene practices, as children often emulate their
parents' behaviors.
Impact on Child's Oral Health: Discuss how parents'
oral health can directly affect their child's health, including the
transmission of bacteria that can lead to dental issues.
Pregnancy Gingivitis:
Education: Inform the mother-to-be about the
potential for pregnancy gingivitis, a common condition characterized by
swollen and bleeding gums due to hormonal changes.
Myth Dispelling: Address common myths surrounding
childbirth and dental health, emphasizing the importance of maintaining
oral hygiene during pregnancy.
Infant Dental Care:
Early Care: Provide a review of infant dental care
practices, including:
The importance of cleaning the infant's gums even before teeth
erupt.
Guidelines for the introduction of the first toothbrush and
toothpaste.
Recommendations for regular dental check-ups starting at the age
of one or when the first tooth appears.
Benefits of Prenatal Counseling
Improved Oral Health: By educating expectant parents
about their own oral hygiene and its impact on their child, both the parents
and the child can achieve better oral health outcomes.
Preparation for Parenthood: Counseling helps parents
feel more prepared and confident in their ability to care for their child's
dental health from an early age.
Long-term Health: Establishing good dental habits early
on can lead to a lifetime of healthy oral practices for the child.
Drug-Receptor Interactions
Pharmacology
Drug-Receptor Interactions
Drug Receptor: any functional macromolecule in a cell to which a drug binds to produce its effects. at receptors, drugs mimic or block the action of the body's own regulatory molecules.
Receptors and Selectivity of Drug Action : If a drug interacts with only one kind of receptor, and if that receptor regulates just a few processes, then the effects of the drug will be limited.
Even though a drug is selective for one type of receptor, it can still produce a variety of effects.
Selectivity does not guarantee safety.
Theories of Drug-Receptor Interaction
- Simple Occupancy Theory: Two factors - The intensity of the response to a drug is proportional to the number of receptors occupied by that drug, and the maximal response will occur when all available receptors have been occupied.
- Modified Occupancy Theory: Assumes that all drugs acting at a particular receptor are identical with respect to the ability to bind to the receptor and the ability to influence receptor function once binding has taken place.
• Affinity: The strength of the attraction between a drug and its receptor. Affinity is reflected in potency. (Drugs with high affinity are very potent).
• Intrinsic Activity: The ability of a drug to activate a receptor following binding. Reflected in the maximal efficacy (drugs with high intrinsic activity have high maximal efficacy).
CRACKED TOOTH SYNDROME
Endodontics
Cracked tooth syndrome denotes an incomplete fracture of a tooth with a vital
pulp. The fracture involves enamel and dentin, often involving the dental pulp.
Prevalence
Molars of older individuals most frequently present with cracked tooth syndrome.
Most cases occur in teeth with class I restorations (39%) or in those that are
unrestored (25%), but with an opposing plunger cusp occluding centrically
against a marginal ridge. Mandibular molars are most commonly affected ,
followed by maxillary molars and maxillary premolars.
Symptoms
The patient usually complains of mild to excruciating pain at the initiation or
release of biting pressure. Such teeth may be sensitive for years because of an
incomplete fracture of enamel and dentin that produces only mild pain.
Eventually, this pain becomes severe when the fracture involves the pulp chamber
also. The pulp in these teeth may become necrotic.
Clinical features
Close examination of the crown of the tooth may disclose an enamel crack, which
may be better visualized by using the following methods:
Fiber optic light: this is used to transilluminate a fracture
line. Most cracks run mesiodistally and are rarely detected radiographically
when they are incomplete.
Dye: Alternatively, staining the fractute with a dye, such as
methylene blue, is a valuable aid to detect a fracture.
Tooth slooth: this is a small pyramid shaped plastic bite
block, with a small concavity at the apex of the pyramid to accommodate the
tooth cusp. This small indentation is placed over the cusp, and the patient is
asked to bite down. Thus, the occlusal force is directed to one cusp at a time,
exerting the desired pressure on the questionable cusp.
Microvascular Trigeminal Decompression
Oral and Maxillofacial SurgeryMicrovascular Trigeminal Decompression (The Jannetta Procedure)
Microvascular decompression (MVD), commonly known as the
Jannetta procedure, is a surgical intervention designed to relieve the symptoms
of classic trigeminal neuralgia by addressing the underlying vascular
compression of the trigeminal nerve. This procedure is particularly effective
for patients who have not responded to medical management or who experience
significant side effects from medications.
Overview of the Procedure
Indication:
MVD is indicated for patients with classic trigeminal neuralgia,
characterized by recurrent episodes of severe facial pain, often
triggered by light touch or specific activities.
Anesthesia:
The procedure is performed under general anesthesia to ensure the
patient is completely unconscious and pain-free during the surgery.
Surgical Approach:
The surgery is conducted using an intraoperative microscope for
enhanced visualization of the delicate structures involved.
The arachnoid membrane surrounding the trigeminal
nerve is carefully opened to access the nerve.
Exploration:
The trigeminal nerve is explored from its entry point at the brainstem to
the entrance of Meckel’s cave, where the trigeminal
ganglion (Gasserian ganglion) is located.
Microdissection:
Under microscopic and endoscopic visualization, the surgeon performs
microdissection to identify and mobilize any arteries or veins that
are compressing the trigeminal nerve.
The most common offending vessel is a branch of the superior
cerebellar artery, but venous compression or a combination of
arterial and venous compression may also be present.
Decompression:
Once the offending vessels are identified, they are decompressed.
This may involve:
Cauterization and division of veins that are
compressing the nerve.
Placement of Teflon sponges between the
dissected blood vessels and the trigeminal nerve to prevent further
vascular compression.
Outcomes and Efficacy
Immediate Pain Relief:
Most patients experience immediate relief from facial pain following
the decompression of the offending vessels.
Reports indicate rates of immediate pain relief as high as 90%
to 98% after the procedure.
Long-Term Relief:
Many patients enjoy long-term relief from trigeminal neuralgia
symptoms, although some may experience recurrence of pain over time.
Complications:
As with any surgical procedure, there are potential risks and
complications, including infection, cerebrospinal fluid leaks, and
neurological deficits. However, MVD is generally considered safe and
effective.