NEET MDS Synopsis
Problems in Film Processing
Radiology
Common Problems in Film Processing
1. Light Radiographs
Causes:
Under Development:
Temperature too low
Time too short
Depleted developer solution
Under Exposure:
Insufficient milliamperage
Insufficient kVp
Insufficient exposure time
Film-source distance too great
Film packet reversed in the mouth
2. Dark Radiographs
Causes:
Over Development:
Temperature too high
Time too long
Accidental exposure to light
Improper safe lighting
Developer concentration too high
Over Exposure:
Excessive milliamperage
Excessive kVp
Excessive exposure time
Film-source distance too short
3. Insufficient Contrast
Causes:
Improper processing conditions (under or over development)
Depleted developer solution
Contaminated solutions
4. Film Fog
Causes:
Excessive kVp
Improper safe lighting
Light leaks in the darkroom
Contaminated developer solution
5. Dark Spots or Tines
Causes:
Contaminated solutions
Film contaminated with developer before processing
Film in contact with tank or another film during fixation
6. Light Spots
Causes:
Insufficient washing
Film contaminated with fixer before processing
Film in contact with tank or another film during development
7. Yellow or Brown Stains
Causes:
Insufficient washing after fixation
Depleted fixer solution
Contaminated solutions
8. Blurring
Causes:
Movement of the patient during exposure
Movement of the X-ray tube head
Double exposure
Misalignment of the X-ray tube head (cone cut)
9. Partial Images
Causes:
Top of film not immersed in developing solution
Film in contact with tank or another film during processing
10. Emulsion Peel
Causes:
Excessive bending of the film
Improper handling of the film
11. Static Discharge
Causes:
Static discharge to film before processing (results in dark lines
with a tree-like image)
12. Fingerprint Contamination
Causes:
Fingerprint contamination during handling of the film
13. Excessive Roller Pressure
Causes:
Excessive roller pressure during processing can lead to artifacts on
the film.
Plaque Formation
PeriodontologyPlaque Formation
Dental plaque is a biofilm that forms on the surfaces of teeth and is a key
factor in the development of dental caries and periodontal disease. The process
of plaque formation can be divided into three major phases:
1. Formation of Pellicle on the Tooth Surface
Definition: The pellicle is a thin, acellular film that
forms on the tooth surface shortly after cleaning.
Composition: It is primarily composed of salivary
glycoproteins and other proteins that are adsorbed onto the enamel surface.
Function:
The pellicle serves as a protective barrier for the tooth surface.
It provides a substrate for bacterial adhesion, facilitating the
subsequent stages of plaque formation.
2. Initial Adhesion & Attachment of Bacteria
Mechanism:
Bacteria in the oral cavity begin to adhere to the pellicle-coated
tooth surface.
This initial adhesion is mediated by specific interactions between
bacterial adhesins (surface proteins) and the components of the
pellicle.
Key Bacterial Species:
Primary colonizers, such as Streptococcus sanguis and Actinomyces
viscosus, are among the first to attach.
Importance:
Successful adhesion is crucial for the establishment of plaque, as
it allows for the accumulation of additional bacteria.
3. Colonization & Plaque Maturation
Colonization:
Once initial bacteria have adhered, they proliferate and create a
more complex community.
Secondary colonizers, including gram-negative anaerobic bacteria,
begin to join the biofilm.
Plaque Maturation:
As the plaque matures, it develops a three-dimensional structure,
with different bacterial species occupying specific niches within the
biofilm.
The matrix of extracellular polysaccharides and salivary
glycoproteins becomes more pronounced, providing structural integrity to
the plaque.
Coaggregation:
Different bacterial species can adhere to one another through
coaggregation, enhancing the complexity of the plaque community.
Composition of Plaque
Matrix Composition:
Plaque is primarily composed of bacteria embedded in a matrix of
salivary glycoproteins and extracellular polysaccharides.
Implications for Removal:
The dense and cohesive nature of this matrix makes it difficult to
remove plaque through simple rinsing or the use of sprays.
Effective plaque removal typically requires mechanical means, such
as brushing and flossing, to disrupt the biofilm structure.
Histology of the Periodontal Ligament (PDL)
Dental Anatomy
Histology of the Periodontal Ligament (PDL)
Embryogenesis of the periodontal ligament
The PDL forms from the dental follicle shortly after root development begins
The periodontal ligament is characterized by connective tissue. The thinnest portion is at the middle third of the root. Its width decreases with age. It is a tissue with a high turnover rate.
FUNCTIONS OF PERIODONTIUM
Tooth support
Shock absorber
Sensory (vibrations appreciated in the middle ear/reflex jaw opening)
The following cells can be identified in the periodontal ligament:
a) Osteoblasts and osteoclasts b) Fibroblasts, c) Epithelial cells
Rests of Malassez
d) Macrophages
e) Undifferentiated cells
f) Cementoblasts and cementoclasts (only in pathologic conditions)
The following types of fibers are found in the PDL
-Collagen fibers: groups of fibers
-Oxytalan fibers: variant of elastic fibers, perpendicular to teeth, adjacent to capillaries
-Eluanin: variant of elastic fibers
Ground substance
PERIODONTAL LIGAMENT FIBERS
Principal fibers
These fibers connect the cementum to the alveolar crest. These are:
a. Alveolar crest group: below CE junction, downward, outward
b. Horizontal group: apical to ACG, right angle
c. Oblique group: numerous, coronally to bone, oblique direction
d. Apical group: around the apex, base of socket
e. Interradicular group: multirooted teeth
Gingival ligament fibers
This group is not strictly related to periodontium. These fibers are:
a. Dentogingival: numerous, cervical cementum to f/a gingiva
b. Alveologingival: bone to f/a gingiva
c. Circular: around neck of teeth, free gingiva
d. Dentoperiosteal: cementum to alv. process or vestibule (muscle)
e. Transseptal: cementum between adjacent teeth, over the alveolar crest
Blood supply of the PDL
The PDL gets its blood supply from perforating arteries (from the cribriform plate of the bundle bone). The small capillaries derive from the superior & inferior alveolar arteries. The blood supply is rich because the PDL has a very high turnover as a tissue. The posterior supply is more prominent than the anterior. The mandibular is more prominent than the maxillary.
Nerve supply
The nerve supply originates from the inferior or the superior alveolar nerves. The fibers enter from the apical region and lateral socket walls. The apical region contains more nerve endings (except Upper Incisors)
Dentogingival junction
This area contains the gingival sulcus. The normal depth of the sulcus is 0.5 to 3.0 mm (mean: 1.8 mm). Depth > 3.0 mm is considered pathologic. The sulcus contains the crevicular fluid
The dentogingival junction is surfaced by:
1) Gingival epithelium: stratified squamous keratinized epithelium 2) Sulcular epithelium: stratified squamous non-keratinized epithelium The lack of keratinization is probably due to inflammation and due to high turnover of this epithelium.
3) Junctional epithelium: flattened epithelial cells with widened intercellular spaces. In the epithelium one identifies neutrophils and monocytes.
Connective tissue
The connective tissue of the dentogingival junction contains inflammatory cells, especially polymorphonuclear neutrophils. These cells migrate to the sulcular and junctional epithelium.
The connective tissue that supports the sulcular epithelium is also structurally and functionally different than the connective tissue that supports the junctional epithelium.
Histology of the Col (=depression)
The col is found in the interdental gingiva. It is surfaced by epithelium that is identical to junctional epithelium. It is an important area because of the accumulation of bacteria, food debris and plaque that can cause periodontal disease.
Blood supply: periosteal vessels
Nerve supply: periodontal nerve fibers, infraorbital, palatine, lingual, mental, buccal
Examples of calculations of doses of vasoconstrictors
Pharmacology
Examples of calculations of doses of vasoconstrictors
Ratio concentrations represent grams per millilitre
1:100,000 = 0.01 mg/mL or 10 µg/mL
1:200,000 = 0.005 mg/mL or 5 µg/mL
1:50,000 = 0.02 mg/mL or 20 µg/mL
1 cartridge of epinephrine 1:200,000 = 9 µg
1 cartridge of epinephrine 1:100,000 = 18 µg
1 cartridge of epinephrine 1:50,000 = 36 µg
1 cartridge of levonordefrin 1:20,000 = 90 µg
Clinical importance of cementum
Dental Anatomy
Clinical importance of cementum
1) Deposition of cementum continues throughout life.
The effects of the continuous deposition of cementum are the maintenance of total length of the tooth (good) and constriction of the apical foramen (bad).
2) With age, the smooth surface of cementum becomes more irregular due to calcification of some ligament fiber bundles. This is referred to as spikes.
Behavior of cementum in pathologic conditions
Carbenicillin
Pharmacology
Carbenicillin
Antibiotic that is chemically similar to ampicillin. Active against gram-negative germs. It is well soluble in water and acid-labile.
Nance Appliance
OrthodonticsThe Nance Appliance is a fixed orthodontic device used
primarily in the upper arch to maintain space and prevent the molars from
drifting forward. It is particularly useful in cases where there is a need to
hold the position of the maxillary molars after the premature loss of primary
molars or to maintain space for the eruption of permanent teeth. Below is an
overview of the Nance Appliance, its components, functions, indications,
advantages, and limitations.
Components of the Nance Appliance
Baseplate:
The Nance Appliance features an acrylic baseplate that is
custom-made to fit the palate. This baseplate is typically made of a
pink acrylic material that is molded to the shape of the patient's
palate.
Anterior Button:
A prominent feature of the Nance Appliance is the anterior button,
which is positioned against the anterior teeth (usually the incisors).
This button helps to stabilize the appliance and provides a point of
contact to prevent the molars from moving forward.
Bands:
The appliance is anchored to the maxillary molars using bands that
are cemented onto the molars. These bands provide the necessary
anchorage for the appliance.
Wire Framework:
A wire framework may be incorporated into the appliance to enhance
its strength and stability. This framework typically consists of a
stainless steel wire that connects the bands and the anterior button.
Functions of the Nance Appliance
Space Maintenance:
The primary function of the Nance Appliance is to maintain space in
the upper arch, particularly after the loss of primary molars. It
prevents the adjacent teeth from drifting into the space, ensuring that
there is adequate room for the eruption of permanent teeth.
Molar Stabilization:
The appliance helps stabilize the maxillary molars in their proper
position, preventing them from moving forward or mesially during
orthodontic treatment.
Arch Development:
In some cases, the Nance Appliance can assist in arch development by
providing a stable base for other orthodontic appliances or treatments.
Indications for Use
Premature Loss of Primary Molars: To maintain space for
the eruption of permanent molars when primary molars are lost early.
Crowding: To prevent adjacent teeth from drifting into
the space created by lost teeth, which can lead to crowding.
Molar Stabilization: To stabilize the position of the
maxillary molars during orthodontic treatment.
Advantages of the Nance Appliance
Fixed Appliance: As a fixed appliance, the Nance
Appliance does not rely on patient compliance, ensuring consistent space
maintenance.
Effective Space Maintenance: It effectively prevents
unwanted tooth movement and maintains space for the eruption of permanent
teeth.
Minimal Discomfort: Generally, patients tolerate the
Nance Appliance well, and it does not cause significant discomfort.
Limitations of the Nance Appliance
Oral Hygiene: Maintaining oral hygiene can be more
challenging with fixed appliances, and patients must be diligent in their
oral care to prevent plaque accumulation and dental issues.
Limited Movement: The Nance Appliance primarily affects
the molars and may not be effective for moving anterior teeth.
Adjustment Needs: While the appliance is generally
stable, it may require periodic adjustments or monitoring by the
orthodontist.
Digit Sucking and Infantile Swallow
PedodonticsDigit Sucking and Infantile Swallow
Introduction to Digit Sucking
Digit sucking is a common behavior observed in infants and young children. It
can be categorized into two main types based on the underlying reasons for the
behavior:
Nutritive Sucking
Definition: This type of sucking occurs during
feeding and is essential for nourishment.
Timing: Nutritive sucking typically begins in the
first few weeks of life.
Causes: It is primarily associated with feeding
problems, where the infant may suck on fingers or digits as a substitute
for breastfeeding or bottle-feeding.
Non-Nutritive Sucking
Definition: This type of sucking is not related to
feeding and serves other psychological or emotional needs.
Causes: Non-nutritive sucking can arise from
various psychological factors, including:
Hunger
Satisfying the innate sucking instinct
Feelings of insecurity
Desire for attention
Examples: Common forms of non-nutritive sucking
habits include:
Thumb or finger sucking
Pacifier sucking
Non-Nutritive Sucking Habits (NMS Habits)
Characteristics: Non-nutritive sucking habits are often
comforting for children and can serve as a coping mechanism in stressful
situations.
Implications: While these habits are generally normal
in early childhood, prolonged non-nutritive sucking can lead to dental
issues, such as malocclusion or changes in the oral cavity.
Infantile Swallow
Definition: The infantile swallow is a specific pattern
of swallowing observed in infants.
Characteristics:
Active contraction of the lip musculature.
The tongue tip is positioned forward, making contact with the lower
lip.
Minimal activity of the posterior tongue and pharyngeal musculature.
Posture: The tongue-to-lower lip contact is so
prevalent in infants that it often becomes their resting posture. This can
be observed when gently moving the infant's lip, causing the tongue tip to
move in unison, suggesting a strong connection between the two.
Developmental Changes: The sucking reflex and the
infantile swallow typically diminish and disappear within the first year of
life as the child matures and develops more complex feeding and swallowing
patterns.