NEET MDS Synopsis
Types of microscopy used in bacteriology
General Microbiology
Types of microscopy used in bacteriology
Light microscopy
Phase contrast microscopy
Fluorescence microscopy
Darkfield microscopy
Transmission electron microscopy
Scanning electron microscopy
Fluorescent microscopy in which ultraviolet rays are used to examine cells after treatment with fluorescent days.
Phase contrast microscope enhances the refractive index differences of the cell components. This microscopy can be used to reveal details of the internal structures as well as capsules, endospores and motility
Electron microscope The resolving power is more than 200 times that of light microscope.
COMPOSITE RESINS -Solution Liners (Varnishes)
Dental Materials
Solution Liners (Varnishes)
Applications
o Enamel and dentin lining for amalgam restorations
o Enamel and dentin lining for cast restorations that are used with non adhesive cements
o Coating over materials that are moisture sensitive during setting
Components of copal resin varnish
o 90% solvent mixture (e.g., chloroform, acetone, and alcohol)
o 10% dissolved copal resin
Reaction
Varnish sets physically by drying Solvent loss occurs in 5 to 15 seconds (a film forms the same way as drying fingernail polish)
Manipulation
Apply thin coat over dentin. enamel. And margins of the cavity preparation Dry lightly with air for 5 seconds Apply a second thin coat Final thickness is 1 to 5 µ.m
Properties
o Physical
Electrically insulating barrier that prevents shocks. Too thin to be thermally insulating. Decreases degree of percolation attributable to thermal expansion
o Chemical
Forms temporary barrier that prevents microleakage into dentinal tubules until secondary dentin formation occurs. Decreases initial tendency for electrochemical corrosion
o Mechanical
Very weak and brittle film that has limited lifetime
Film adheres to smear layer
Growth Theories
PedodonticsGrowth Theories
Understanding the growth of craniofacial structures is crucial in
pedodontics, as it directly influences dental development, occlusion, and
treatment planning. Various growth theories have been proposed to explain the
mechanisms behind craniofacial growth, each with its own assumptions and
clinical implications.
Growth Theories Overview
1. Genetic Theory (Brodle, 1941)
Assumption: Genes control all aspects of growth.
Application: While genetic factors play a role,
external factors significantly modify growth, reducing the sole impact of
genetics. Inheritance is polygenic, influencing predispositions such as
Class III malocclusion.
2. Scott’s Hypothesis (1953)
Assumption: Cartilage has innate growth potential,
which is later replaced by bone.
Application:
Mandibular growth is likened to long bone growth, with the condyles
acting as diaphysis.
Recent studies suggest that condylar growth is primarily reactive
rather than innate.
Maxillary growth is attributed to the translation of the
nasomaxillary complex.
3. Sutural Dominance Theory (Sicher, 1955)
Assumption: Sutural connective tissue proliferation
leads to appositional growth.
Application:
Maxillary growth is explained by pressure from sutural growth.
Limitations include inability to explain:
Lack of growth in suture transplantation.
Growth in cleft palate cases.
Sutural responses to external influences.
4. Moss’s Functional Theory (1962)
Assumption: Functional matrices (capsular and
periosteal) control craniofacial growth, with bone responding passively.
Application:
Examples include excessive cranial vault growth in hydrocephalus
cases, illustrating the influence of functional matrices on bone growth.
5. Van Limborgh’s Theory (1970)
Assumption: Skeletal morphogenesis is influenced by:
Intrinsic genetic factors
Local epigenetic factors
General epigenetic factors
Local environmental factors
General environmental factors
Application:
Highlights the interaction between genetic and environmental
factors, emphasizing that muscle and soft tissue growth also has a
genetic component.
Predicting facial dimensions based on parental studies is limited
due to the polygenic and multifactorial nature of growth.
6. Petrovic’s Hypothesis (1974, Cybernetics)
Assumption: Primary cartilage growth is influenced by
differentiation of chondroblasts, while secondary cartilage has both direct
and indirect effects on growth.
Application:
Explains the action of functional appliances on the condyle.
The upper arch serves as a mold for the lower arch, facilitating
optimal occlusion.
7. Neurotropism (Behrents, 1976)
Assumption: Nerve impulses, through axoplasmic
transport, have direct growth potential and influence soft tissue growth
indirectly.
Application:
The effect of neurotropism on growth is reported to be negligible,
suggesting limited clinical implications.
Clinical Implications
Understanding these growth theories is essential for pediatric dentists in
several ways:
Diagnosis and Treatment Planning: Knowledge of growth
patterns aids in diagnosing malocclusions and planning orthodontic
interventions.
Timing of Interventions: Recognizing the stages of
growth can help in timing treatments such as extractions, space maintainers,
and orthodontic appliances.
Predicting Growth Outcomes: Awareness of genetic and
environmental influences can assist in predicting treatment outcomes and
managing patient expectations.
Adult Respiratory Distress Syndrome
General Pathology
Adult Respiratory Distress Syndrome
A constellation of pathologic and clinical findings initiated by diffuse injury to alveolar capillaries. This syndrome is associated with a multitude of clinical conditions which primarily damage the lung or secondarily as part of a systemic disorder.
Pathogenesis
There are many types of injuries which lead to the ultimate, common pathway, i.e., damage to the alveolar capillary unit. The initial injury most frequently affects the endothelium, less frequently the alveolar epithelium. Injury produces increased vascular permeability, edema, fibrin-exudation (hyaline membranes). Leukocytes (primarily neutrophils) plays a key role in endothelial damage.
Pathology
Heavy, red lungs showing congestion and edema. The alveoli contain fluid and are lined by hyaline membranes.
Pathophysiology
Severe respiratory insufficiency with dyspnea, cyanosis and hypoxemia refractory to oxygen therapy.
Modified Gingival Index
PeriodontologyModified Gingival Index (MGI)
The Modified Gingival Index (MGI) is a clinical tool used to assess the
severity of gingival inflammation. It provides a standardized method for
evaluating the health of the gingival tissues, which is essential for diagnosing
periodontal conditions and monitoring treatment outcomes. Understanding the
scoring criteria of the MGI is crucial for dental professionals in their
assessments.
Scoring Criteria for the Modified Gingival Index (MGI)
The MGI uses a scale from 0 to 4 to classify the degree of gingival
inflammation. Each score corresponds to specific clinical findings:
Score 0: Absence of Inflammation
Description: No signs of inflammation are present
in the gingival tissues.
Clinical Significance: Indicates healthy gingiva
with no bleeding or other pathological changes.
Score 1: Mild Inflammation
Description:
Slight change in color (e.g., slight redness).
Little change in texture of any portion of the marginal or
papillary gingival unit, but not affecting the entire unit.
Clinical Significance: Suggests early signs of
gingival inflammation, which may require monitoring and preventive
measures.
Score 2: Mild Inflammation (Widespread)
Description:
Similar criteria as Score 1, but involving the entire marginal
or papillary gingival unit.
Clinical Significance: Indicates a more widespread
mild inflammation that may necessitate intervention to prevent
progression.
Score 3: Moderate Inflammation
Description:
Glazing of the gingiva.
Redness, edema, and/or hypertrophy of the marginal or papillary
gingival unit.
Clinical Significance: Reflects a moderate level of
inflammation that may require active treatment to reduce inflammation
and restore gingival health.
Score 4: Severe Inflammation
Description:
Marked redness, edema, and/or hypertrophy of the marginal or
papillary gingival unit.
Presence of spontaneous bleeding, congestion, or ulceration.
Clinical Significance: Indicates severe gingival
disease that requires immediate intervention and may be associated with
periodontal disease.
Clinical Application of the MGI
Assessment of Gingival Health:
The MGI provides a systematic approach to evaluate gingival health,
allowing for consistent documentation of inflammation levels.
Monitoring Treatment Outcomes:
Regular use of the MGI can help track changes in gingival health
over time, assessing the effectiveness of periodontal treatments and
preventive measures.
Patient Education:
The MGI can be used to educate patients about their gingival health
status, helping them understand the importance of oral hygiene and
regular dental visits.
Research and Epidemiological Studies:
The MGI is often used in clinical research to evaluate the
prevalence and severity of gingival disease in populations.
Cardiac Output
Physiology
Cardiac Output:
Minute Volume = Heart Rate X Stroke Volume
Heart rate, HR at rest = 65 to 85 bpm
Each heartbeat at rest takes about .8 sec. of which .4 sec. is quiescent period.
Stroke volume, SV at rest = 60 to 70 ml.
Heart can increase both rate and volume with exercise. Rate increase is limited due to necessity of minimum ventricular diastolic period for filling. Upper limit is usually put at about 220 bpm. Maximum heart rate calculations are usually below 200. Target heart rates for anaerobic threshold are about 85 to 95% of maximum.
Terms:
End Diastolic Volume, EDV - the maximum volume of the ventricles achieved at the end of ventricular diastole. This is the amount of blood the heart has available to pump. If this volume increases the cardiac output increases in a healthy heart.
End Systolic Volume, ESV - the minimum volume remaining in the ventricle after its systole. If this volume increases it means less blood has been pumped and the cardiac output is less.
EDV - ESV = SV
SV / EDV = Ejection Fraction The ejection fraction is normally around 50% at rest and will increase during strenuous exercise in a healthy heart. Well trained athletes may have ejection fractions approaching 70% in the most strenuous exercise.
Isovolumetric Contraction Phase - a brief period at the beginning of ventricular systole when all valves are closed and ventricular volume remains constant. Pressure has risen enough in the ventricle to close the AV valves but not enough to open the semilunar valves and cause ejection of blood.
Isovolumetric Relaxation Phase - a brief period at the beginning of ventricular diastole when all valves are closed and ventricular volume is constant. Pressure in the ventricle has lowered producing closure of the semilunar valves but not opening the AV valves to begin pulling blood into the ventricle.
Dicrotic Notch - the small increase in pressure of the aorta or other artery seen when recording a pulse wave. This occurs as blood is briefly pulled back toward the ventricle at the beginning of diastole thus closing the semilunar valves.
Preload - This is the pressure at the end of ventricular diastole, at the beginning of ventricular systole. It is proportional to the End Diastolic Volume (EDV), i.e. as the EDV increases so does the preload of the heart. Factors which increase the preload are: increased total blood volume, increased venous tone and venous return, increased atrial contraction, and the skeletal muscular pump.
Afterload - This is the impedence against which the left ventricle must eject blood, and it is roughly proportional to the End Systolic Volume (ESV). When the peripheral resistance increases so does the ESV and the afterload of the heart.
The importance of these parameters are as a measure of efficiency of the heart, which increases as the difference between preload and afterload increases
Multiple sclerosis
General Pathology
Multiple sclerosis
a. A demyelinating disease that primarily affects myelin (i.e. white matter). This affects the conduction of electrical impulses along the axons of nerves. Areas of demyelination are known as plaques.
b. The most common demyelinating disease.
c. Onset of disease usually occurs between ages 20 and 50; slightly more common in women.
d. Disease can affect any neuron in the central nervous system, including the brainstem and spinal cord. The optic nerve (vision) is commonly affected.
Denture Teeth
Dental Materials
Denture Teeth
Use-complete or partial dentures
Type
a. Porcelain teeth
b. Acrylic resin teeth
c. Abrasion-resistant teeth (microfilled composite)
Structure and properties
1. Porcelain teeth (high-fusing porcelain)
Only bonded into denture base mechanically. Harder than natural teeth or other restorations and abrades those surfaces. Good aesthetics.Used when patients have good ridge support and sufficient room between the arches
2. Acrylic resin teeth (PMMA [polymethyl methacrylate])
Bonded pseudochemically into the denture base. Soft and easily worn by abrasive foods . Good initial aesthetics
Used with patients with poor ridges and in cases where they oppose natural teeth
3. Abrasion-resistant teeth (microfilled resins)
Bonded pseudochemically into the denture base.Better abrasion resistance then acrylic resin teeth