NEET MDS Synopsis
ORMOCER (Organically Modified Ceramic)
Conservative DentistryORMOCER (Organically Modified Ceramic)
ORMOCER is a modern dental material that combines organic and inorganic
components to create a versatile and effective restorative option. Introduced as
a dental restorative material in 1998, ORMOCER has gained attention for its
unique properties and applications in dentistry.
1. Composition of ORMOCER
ORMOCER is characterized by a complex structure that includes both organic
and inorganic networks. The main components of ORMOCER are:
A. Organic Molecule Segments
Methacrylate Groups: These segments form a highly
cross-linked matrix, contributing to the material's strength and stability.
B. Inorganic Condensing Molecules
Three-Dimensional Networks: The inorganic components
are formed through inorganic polycondensation, creating a robust backbone
for the ORMOCER molecules. This structure enhances the material's mechanical
properties.
C. Fillers
Additional Fillers: Fillers are incorporated into the
ORMOCER matrix to improve its physical properties, such as strength and wear
resistance.
2. Properties of ORMOCER
ORMOCER exhibits several advantageous properties that make it suitable for
various dental applications:
Biocompatibility: ORMOCER is more biocompatible than
conventional composites, making it a safer choice for dental restorations.
Higher Bond Strength: The material demonstrates superior
bond strength, enhancing its adhesion to tooth structure and restorative
materials.
Minimal Polymerization Shrinkage: ORMOCER has the least
polymerization shrinkage among resin-based filling materials, reducing the
risk of gaps and microleakage.
Aesthetic Qualities: The material is highly aesthetic
and can be matched to the natural color of teeth, making it suitable for
cosmetic applications.
Mechanical Strength: ORMOCER exhibits high compressive
strength (410 MPa) and transverse strength (143 MPa), providing durability
and resistance to fracture.
3. Indications for Use
ORMOCER is indicated for a variety of dental applications, including:
Restorations for All Types of Preparations: ORMOCER can
be used for direct and indirect restorations in various cavity preparations.
Aesthetic Veneers: The material's aesthetic properties
make it an excellent choice for fabricating veneers that blend seamlessly
with natural teeth.
Orthodontic Bonding Adhesive: ORMOCER can be utilized as
an adhesive for bonding orthodontic brackets and appliances to teeth.
COMPOSITE RESINS -Bonding Agents
Dental Materials
Bonding Agents
Applications-composites, resin-modified gIass ionomers, ceramic bonded to enamel restorations, veneers, orthodontic brackets, and desensitizing dentin by covering exposed tubules (Maryland bridges, composite and ceramic repair systems, amalgams and amalgam repair, and pinned amalgams)
Definitions;-
Smear layer - Layer of compacted debris on enamel and/or dentin from the cavity preparation process that is weakly held to the surface (6 to 7 MPa) , and that limits bonding agent strength if not removed
Etching (or, conditioning)- smear layer removal and production of microspaces for micromechanical bonding by dissolving –minor amounts of surface hydroxyapatite crystals
Priming..- micromechanical (and chemical) bonding to the microspaces created by conditioning step.
Conditioning/priming agent-agent that accomplishes both actions
Bonding- formation of resin layer that connect the primed surface to the overlying restoration (e.g., composite) .. –
Enamel bonding System-for bonding to enamel (although dentin bonding may be a Second step)
Dentin bonding system for bonding to dentin (although enamel bonding may have been a first step)
• First-generation dentin bonding system for bonding to smear layer
• New-generation dentin bonding system- for removing smear layer and etching intertubular dentin to allow primer and/or bonding agent to diffuse into spaces between collagen and form hybrid zone
Enamel and dentin bonding system-for bonding to enamel and dentin surfaces with the same procedures
Amalgam bonding system for bonding to enamel, dentin, and amalgam, dentin and amalgam during an amalgam placement procedure or for amalgam repair
Universal bonding system-for bonding to enamel, dentin, amalgam, porcelain , or any other substrate intraorally that may be necessary for a restorative procedure using the same set of procedures and materials
Types
Enamel bonding systems
Dentin bonding systems
Amalgam bonding systems
Universal bonding systems
Structure
o Components of bonding systems
o Conditioning agent-mineral or organic acid
Enamel only 37% phosphoric acid
Dentin only or enamel and .dentin---37% phosphoric acid, citric acid, maleic acid, or nitric acid
o Priming agent
Hydrophobic-solvent-soluble, light cured monomer system
Hydrophilic-water-soluble, light-cured monomer system
Bonding agent
BIS-GMA-type monomer system
UDMA-type monomer system
Reaction
Bonding occurs primarily by intimate micromechanical retention with the relief created by the conditioning step
Chemical bonding is possible but is not recognized as contributing significantly to the overall bond strength
Manipulation-follow manufacturer's directions
Properties
Physical-thermal expansion and contraction may create fatigue stresses that debond the interface and permit micro leakage
Chemical-water absorption into the bonding agent may chemically alter the bonding
Mechanical-mechanical stresses may produce fatigue that debonds the interface and permits microleakage
Enamel bonding-adhesion occurs by macrotags (between enamel prisms) and microtags (into enamel prisms) to produce micromechanical retention
Dentin bonding-adhesion occurs by penetration of smear layer and formation of microtags into intertubular dentin to produce a hybrid zone (interpenetration zone or diffusion zone) that microscopically intertwines collagen bundles and bonding agent polymer
Biologic
Conditioning agents may be locally irritating if they come into contact with soft tissue
Priming agents (uncured), particularly those based on HEMA, may be skin sensitizers after several contacts with dental personnel
Protect skin on hands and face from inadvertent contact with unset materials and/ or their vapors
HEMA and other priming monomers may penetrate through rubber gloves in relatively short times (60 to 90 seconds)
The developing tooth bud -Bell stage
Dental Anatomy
Bell stage
The bell stage is known for the histodifferentiation and morphodifferentiation that takes place. The dental organ is bell-shaped during this stage, and the majority of its cells are called stellate reticulum because of their star-shaped appearance. Cells on the periphery of the enamel organ separate into three important layers. Cuboidal cells on the periphery of the dental organ are known as outer enamel epithelium.The cells of the enamel organ adjacent to the dental papilla are known as inner enamel epithelium. The cells between the inner enamel epithelium and the stellate reticulum form a layer known as the stratum intermedium. The rim of the dental organ where the outer and inner enamel epithelium join is called the cervical loop
Other events occur during the bell stage. The dental lamina disintegrates, leaving the developing teeth completely separated from the epithelium of the oral cavity; the two will not join again until the final eruption of the tooth into the mouth
The crown of the tooth, which is influenced by the shape of the internal enamel epithelium, also takes shape during this stage. Throughout the mouth, all teeth undergo this same process; it is still uncertain why teeth form various crown shapes—for instance, incisors versus canines. There are two dominant hypotheses. The "field model" proposes there are components for each type of tooth shape found in the ectomesenchyme during tooth development. The components for particular types of teeth, such as incisors, are localized in one area and dissipate rapidly in different parts of the mouth. Thus, for example, the "incisor field" has factors that develop teeth into incisor shape, and this field is concentrated in the central incisor area, but decreases rapidly in the canine area. The other dominant hypothesis, the "clone model", proposes that the epithelium programs a group of ectomesenchymal cells to generate teeth of particular shapes. This group of cells, called a clone, coaxes the dental lamina into tooth development, causing a tooth bud to form. Growth of the dental lamina continues in an area called the "progress zone". Once the progress zone travels a certain distance from the first tooth bud, a second tooth bud will start to develop. These two models are not necessarily mutually exclusive, nor does widely accepted dental science consider them to be so: it is postulated that both models influence tooth development at different times.Other structures that may appear in a developing tooth in this stage are enamel knots, enamel cords, and enamel niche.
Moro Reflex and Startle Reflex
PedodonticsMoro Reflex and Startle Reflex
Moro Reflex
The Moro reflex, also known as the startle
reflex, is an involuntary response observed in infants, typically elicited
by sudden movements or changes in position of the head and neck.
Elicitation:
A common method to elicit the Moro reflex is to pull the baby
halfway to a sitting position from a supine position and then suddenly
let the head fall back a short distance.
Response:
The reflex consists of a rapid abduction and extension of the arms,
accompanied by the opening of the hands.
Following this initial response, the arms then come together as if
in an embrace.
Clinical Importance:
The Moro reflex provides valuable information about the infant's
muscle tone and neurological function.
An asymmetrical response may indicate:
Unequal muscle tone on either side.
Weakness in one arm.
Possible injury to the humerus or clavicle.
The Moro reflex typically disappears by 2 to 3 months of age, which
is a normal part of development.
Startle Reflex
The startle reflex is similar to the Moro
reflex but is specifically triggered by sudden noises or other unexpected
stimuli.
Response:
In the startle reflex, the elbows are flexed, and the hands remain
closed, showing less of an embracing motion compared to the Moro reflex.
The movement of the arms may involve both outward and inward
motions, but it is less pronounced than in the Moro reflex.
Clinical Importance:
The startle reflex is an important indicator of an infant's sensory
processing and neurological integrity.
It can also be used to assess the infant's response to environmental
stimuli and overall alertness.
Amorphous Calcium Phosphate
Conservative DentistryAmorphous Calcium Phosphate (ACP)
Amorphous Calcium Phosphate (ACP) is a significant compound in dental
materials and oral health, known for its role in the biological formation of
hydroxyapatite, the primary mineral component of tooth enamel and bone. ACP has
both preventive and restorative applications in dentistry, making it a valuable
material for enhancing oral health.
1. Biological Role
A. Precursor to Hydroxyapatite
Formation: ACP serves as an antecedent in the
biological formation of hydroxyapatite (HAP), which is essential for the
mineralization of teeth and bones.
Conversion: At neutral to high pH levels, ACP remains
in its original amorphous form. However, when exposed to low pH conditions
(pH < 5-8), ACP converts into hydroxyapatite, helping to replace the HAP
lost due to acidic demineralization.
2. Properties of ACP
A. pH-Dependent Behavior
Neutral/High pH: At neutral or high pH levels, ACP
remains stable and does not dissolve.
Low pH: When the pH drops below 5-8, ACP begins to
dissolve, releasing calcium (Ca²⁺) and phosphate (PO₄³⁻) ions. This process
is crucial in areas where enamel demineralization has occurred due to acid
exposure.
B. Smart Material Characteristics
ACP is often referred to as a "smart material" due to its unique properties:
Targeted Release: ACP releases calcium and phosphate
ions specifically at low pH levels, which is when the tooth is at risk of
demineralization.
Acid Neutralization: The released calcium and phosphate
ions help neutralize acids in the oral environment, effectively buffering
the pH and reducing the risk of further enamel erosion.
Reinforcement of Natural Defense: ACP reinforces the
tooth’s natural defense system by providing essential minerals only when
they are needed, thus promoting remineralization.
Longevity: ACP has a long lifespan in the oral cavity
and does not wash out easily, making it effective for sustained protection.
3. Applications in Dentistry
A. Preventive Applications
Remineralization: ACP is used in various dental
products, such as toothpaste and mouth rinses, to promote the
remineralization of early carious lesions and enhance enamel strength.
Fluoride Combination: ACP can be combined with fluoride
to enhance its effectiveness in preventing caries and promoting
remineralization.
B. Restorative Applications
Dental Materials: ACP is incorporated into restorative
materials, such as composites and sealants, to improve their mechanical
properties and provide additional protection against caries.
Cavity Liners and Bases: ACP can be used in cavity
liners and bases to promote healing and remineralization of the underlying
dentin.
Alcoholic cirrhosis
General Pathology
Alcoholic (nutritional, Laennec’s) cirrhosis
Pathology
Liver is at first enlarged (fatty change), then return to normal size and lastly, it becomes slightly reduced in size (1.2 kg or more).
- Cirrhosis is micronodular then macronodular then mixed.
M/E
Hepatocytes:- show fatty change that decreases progressively. Few hepatocytes show increased intracytoplasmic haemochromatosis.
b. Fibrous septa:- Regular margins between it and regenerating nodules.
-Moderate lymphocytic infiltrate.
– Slight bile ductular proliferation.
Prognosis:- It Progresses slowly over few years.
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.
POLISHING MATERIALS
Dental Materials
POLISHING MATERIALS
1 Tin Oxide. Tin oxide is used in polishing teeth and metal restorations. Tin oxide is a fine, white powder that is made into a paste by adding water or glycerin.
2. Pumice. Pumice is used as an abrasive and polishing agent for acrylic resins, amalgams, and gold. It consists mainly of complex silicates of aluminum, potassium, and sodium. Two grades--flour of pumice and coarse pumice--are listed in the Federal Supply Catalog.
3. Chalk (Whiting). Chalk is used for polishing acrylic resins and metals. It is composed primarily of calcium carbonate.
4.Tripoli. Tripoli is usually used for polishing gold and other metals. It is made from certain porous rocks.
5. Rouge (Jeweler's). Rouge is used for polishing gold and is composed of iron oxide. It is usually in cake or stick form.
6. Zirconium Silicate. Zirconium silicate is used for cleaning and polishing teeth. It may be mixed with water or with fluoride solution for caries prevention treatment. For full effectiveness, instructions must be followed exactly to obtain the proper proportions of powder to liquid.