NEET MDS Synopsis
Prognosis After Traumatic Brain Injury
Oral and Maxillofacial SurgeryPrognosis After Traumatic Brain Injury (TBI)
Determining the prognosis for patients after a traumatic brain injury
(TBI) is a complex and multifaceted process. Several factors can
influence the outcome, and understanding these variables is crucial for
clinicians in managing TBI patients effectively. Below is an overview of the key
prognostic indicators, with a focus on the Glasgow Coma Scale (GCS) and other
factors that correlate with severity and outcomes.
Key Prognostic Indicators
Glasgow Coma Scale (GCS):
The GCS is a widely used tool for assessing the level of
consciousness in TBI patients. It evaluates three components: eye
opening (E), best motor response (M), and verbal response (V).
Coma Score Calculation:
The total GCS score is calculated as follows: [ \text{Coma
Score} = E + M + V ]
Prognostic Implications:
Scores of 3-4: Patients scoring in this range
have an 85% chance of dying or remaining in a vegetative
state.
Scores of 11 or above: Patients with scores in
this range have only a 5-10% chance of dying or remaining
vegetative.
Intermediate Scores: Scores between these
ranges correlate with proportional chances of recovery, indicating
that higher scores generally predict better outcomes.
Other Poor Prognosis Indicators:
Older Age: Age is a significant factor, with older
patients generally having worse outcomes following TBI.
Increased Intracranial Pressure (ICP): Elevated ICP
is associated with poorer outcomes, as it can lead to brain herniation
and further injury.
Hypoxia and Hypotension: Both conditions can
exacerbate brain injury and are associated with worse prognoses.
CT Evidence of Compression: Imaging findings such
as compression of the cisterns or midline shift indicate significant
mass effect and are associated with poor outcomes.
Delayed Evacuation of Large Intracerebral Hemorrhage:
Timely surgical intervention is critical; delays can worsen the
prognosis.
Carrier Status for Apolipoprotein E-4 Allele: The
presence of this allele has been linked to poorer outcomes in TBI
patients, suggesting a genetic predisposition to worse recovery.
Distoangular Impaction
Oral and Maxillofacial SurgeryDistoangular Impaction
Distoangular impaction refers to the position of a tooth,
typically a third molar (wisdom tooth), that is angled towards the back of the
mouth and the distal aspect of the mandible. This type of impaction is often
considered one of the most challenging to manage surgically due to its
orientation and the anatomical considerations involved in its removal.
Characteristics of Distoangular Impaction
Pathway of Delivery:
The distoangular position of the tooth means that it is situated in
a way that complicates its removal. The pathway for extraction often
requires significant manipulation and access through the ascending ramus
of the mandible.
Bone Removal:
A substantial amount of distal bone removal is necessary to access
the tooth adequately. This may involve the use of surgical instruments
to contour the bone and create sufficient space for extraction.
Crown Sectioning:
Once adequate bone removal has been achieved, the crown of the tooth
is typically sectioned from the roots just above the cervical line. This
step is crucial for improving visibility and access to the roots, which
can be difficult to see and manipulate in their impacted position.
Removal of the Crown:
The entire crown is removed to facilitate better access to the
roots. This step is essential for ensuring that the roots can be
addressed without obstruction from the crown.
Root Management:
Divergent Roots: If the roots of the tooth are
divergent (spreading apart), they may need to be further sectioned into
two pieces. This allows for easier removal of each root individually,
reducing the risk of fracture or complications during extraction.
Convergent Roots: If the roots are convergent
(closer together), a straight elevator can often be used to remove the
roots without the need for additional sectioning. The elevator is
inserted between the roots to gently lift and dislodge them from the
surrounding bone.
Surgical Technique Overview
Anesthesia: Local anesthesia is administered to ensure
patient comfort during the procedure.
Incision and Flap Reflection: An incision is made in the
mucosa, and a flap is reflected to expose the underlying bone and the
impacted tooth.
Bone Removal: Using a surgical bur or chisel, the distal
bone is carefully removed to create access to the tooth.
Crown Sectioning: The crown is sectioned from the roots
using a surgical handpiece or bur, allowing for improved visibility.
Root Extraction:
For divergent roots, each root is sectioned and removed
individually.
For convergent roots, a straight elevator is used to extract the
roots.
Closure: After the tooth is removed, the surgical site
is irrigated, and the flap is repositioned and sutured to promote healing.
Considerations and Complications
Complications: Distoangular impactions can lead to
complications such as nerve injury (especially to the inferior alveolar
nerve), infection, and prolonged recovery time.
Postoperative Care: Patients should be advised on
postoperative care, including pain management, oral hygiene, and signs of
complications such as swelling or infection.
Types of Neurons
Pharmacology
Types of Neurons (Function)
•There are 3 general types of neurons (nerve cells):
1-Sensory (Afferent ) neuron:A neuron that detects changes in the external or internal environment and sends information about these changes to the CNS. (e.g: rods and cones, touch receptors). They usually have long dendrites and relatively short axons.
2-Motor (Efferent) neuron:A neuron located within the CNS that controls the contraction of a muscle or the secretion of a gland. They usually have short dendrites and long axons.
2-Interneuron or association neurons: A neuron located entirely within the CNS in which they form the connecting link between the afferent and efferent neurons. They have short dendrites and may have either a short or long axon.
Basic Properties of Gases
Physiology
Basic Properties of Gases
A. Dalton's Law of Partial Pressures
1. partial pressure - the "part" of the total air pressure caused by one component of a gas
Gas Percent Partial Pressure (P)
ALL AIR 100.0% 760 mm Hg
Nitrogen 78.6% 597 mm Hg (0.79 X 760)
Oxygen 20.9% l59 mm Hg (0.21 X 760)
CO2 0.04% 0.3 mm Hg (0.0004 X 760)
2. altitude - air pressure @ 10,000 ft = 563 mm Hg
3. scuba diving - air pressure @ 100 ft = 3000 mm Hg
B. Henry's Law of Gas Diffusion into Liquid
1. Henry's Law - a certain gas will diffuse INTO or OUT OF a liquid down its concentration gradient in proportion to its partial pressure
2. solubility - the ease with which a certain gas will "dissolve" into a liquid (like blood plasma)
HIGHest solubility in plasma Carbon Dioxide
Oxygen
LOWest solubility in plasma Nitrogen
C. Hyperbaric (Above normal pressure) Conditions
1. Creates HIGH gradient for gas entry into the body
2. therapeutic - oxygen forced into blood during: carbon monoxide poisoning, circulatory shock, asphyxiation, gangrene, tetanus, etc.
3. harmful - SCUBA divers may suffer the "bends" when they rise too quickly and Nitrogen gas "comes out of solution" and forms bubbles in the blood
DISINFECTION AND STERILIZATION
General Microbiology
DISINFECTION AND STERILIZATION
• Sterilization is the best destruction or com removal_of all forms of micro organisms.
• Disinfection is the destruction of many microorganisms but usually the b spores.
• Antisepsis is the destruction or inhibition of microorganisms in living tissues thereby limiting or preventing the harmful effect of infection.
• Astatic Agent would only inhibit the growth of microorganisms (bacteriostatic, fungistatic, sporostatic).
• Acidal agent would kill the microorganism (bactericidal. virucidal, fungicidal)
• Sterilants are the chemicals which under controlled conditions can kill sporinQ bacteria.
Automated Probing Systems
PeriodontologyAutomated Probing Systems
Automated probing systems have become increasingly important in periodontal
assessments, providing enhanced accuracy and efficiency in measuring pocket
depths and clinical attachment levels. This lecture will focus on the Florida
Probe System, the Foster-Miller Probe, and the Toronto Automated Probe,
discussing their features, advantages, and limitations.
1. Florida Probe System
Overview: The Florida Probe System is an automated
probing system designed to facilitate accurate periodontal assessments. It
consists of several components:
Probe Handpiece: The instrument used to measure
pocket depths.
Digital Readout: Displays measurements in
real-time.
Foot Switch: Allows for hands-free operation.
Computer Interface: Connects the probe to a
computer for data management.
Specifications:
Probe Diameter: The end of the probe is 0.4
mm in diameter, allowing for precise measurements in
periodontal pockets.
Advantages:
Constant Probing Force: The system applies a
consistent force during probing, reducing variability in measurements.
Precise Electronic Measurement: Provides accurate
and reproducible measurements of pocket depths.
Computer Storage of Data: Enables easy storage,
retrieval, and analysis of patient data, facilitating better
record-keeping and tracking of periodontal health over time.
Disadvantages:
Lack of Tactile Sensitivity: The automated nature
of the probe means that clinicians do not receive tactile feedback,
which can be important for assessing tissue health.
Fixed Force Setting: The use of a fixed force
setting throughout the mouth may not account for variations in tissue
condition, potentially leading to inaccurate measurements or patient
discomfort.
2. Foster-Miller Probe
Overview: The Foster-Miller Probe is another automated
probing system that offers unique features for periodontal assessment.
Capabilities:
Pocket Depth Measurement: This probe can measure
pocket depths effectively.
Detection of the Cemento-Enamel Junction (CEJ): It
is capable of coupling pocket depth measurements with the detection of
the CEJ, providing valuable information about clinical attachment
levels.
3. Toronto Automated Probe
Overview: The Toronto Automated Probe is designed to
enhance the accuracy of probing in periodontal assessments.
Specifications:
Probing Mechanism: The sulcus is probed with a 0.5
mm nickel titanium wire that is extended under air pressure,
allowing for gentle probing.
Angular Control: The system controls angular
discrepancies using a mercury tilt sensor, which limits
angulation within ±30 degrees. This feature helps
maintain consistent probing angles.
Limitations:
Reproducible Positioning: The probe requires
reproducible positioning of the patient’s head, which can be challenging
in some clinical settings.
Limited Access: The design may not easily
accommodate measurements of second or third molars, potentially limiting
its use in comprehensive periodontal assessments.
Capacity of Motion of the Mandible
Conservative DentistryCapacity of Motion of the Mandible
The capacity of motion of the mandible is a crucial aspect of dental and
orthodontic practice, as it influences occlusion, function, and treatment
planning. In 1952, Dr. Harold Posselt developed a systematic approach to
recording and analyzing mandibular movements, resulting in what is now known as
Posselt's diagram. This guide will provide an overview of Posselt's work, the
significance of mandibular motion, and the key points of reference used in
clinical practice.
1. Posselt's Diagram
A. Historical Context
Development: In 1952, Dr. Harold Posselt utilized a
system of clutches and flags to record the motion of the mandible. His work
laid the foundation for understanding mandibular dynamics and occlusion.
Recording Method: The original recordings were
conducted outside of the mouth, which magnified the vertical dimension of
movement but did not accurately represent the horizontal dimension.
B. Modern Techniques
Digital Recording: Advances in technology have allowed
for the use of digital computer techniques to record mandibular motion in
real-time. This enables accurate measurement of movements in both vertical
and horizontal dimensions.
Reconstruction of Motion: Modern systems can compute
and visualize mandibular motion at multiple points simultaneously, providing
valuable insights for clinical applications.
2. Key Points of Reference
Three significant points of reference are particularly important in the study
of mandibular motion:
A. Incisor Point
Location: The incisor point is located on the midline
of the mandible at the junction of the facial surface of the mandibular
central incisors and the incisal edge.
Clinical Significance: This point is crucial for
assessing anterior guidance and incisal function during mandibular
movements.
B. Molar Point
Location: The molar point is defined as the tip of the
mesiofacial cusp of the mandibular first molar on a specified side.
Clinical Significance: The molar point is important for
evaluating occlusal relationships and the functional dynamics of the
posterior teeth during movement.
C. Condyle Point
Location: The condyle point refers to the center of
rotation of the mandibular condyle on the specified side.
Clinical Significance: Understanding the condyle point
is essential for analyzing the temporomandibular joint (TMJ) function and
the overall biomechanics of the mandible.
3. Clinical Implications
A. Occlusion and Function
Mandibular Motion: The capacity of motion of the
mandible affects occlusal relationships, functional movements, and the
overall health of the masticatory system.
Treatment Planning: Knowledge of mandibular motion is
critical for orthodontic treatment, prosthodontics, and restorative
dentistry, as it influences the design and placement of restorations and
appliances.
B. Diagnosis and Assessment
Evaluation of Movement: Clinicians can use the
principles established by Posselt to assess and diagnose issues related to
mandibular function, such as limitations in movement or discrepancies in
occlusion.
Partial Pressure
Physiology
it's the individual pressure exerted independently by a particular gas within a mixture of gasses. The air we breath is a mixture of gasses: primarily nitrogen, oxygen, & carbon dioxide. So, the air you blow into a balloon creates pressure that causes the balloon to expand (& this pressure is generated as all the molecules of nitrogen, oxygen, & carbon dioxide move about & collide with the walls of the balloon). However, the total pressure generated by the air is due in part to nitrogen, in part to oxygen, & in part to carbon dioxide. That part of the total pressure generated by oxygen is the 'partial pressure' of oxygen, while that generated by carbon dioxide is the 'partial pressure' of carbon dioxide. A gas's partial pressure, therefore, is a measure of how much of that gas is present (e.g., in the blood or alveoli).
the partial pressure exerted by each gas in a mixture equals the total pressure times the fractional composition of the gas in the mixture. So, given that total atmospheric pressure (at sea level) is about 760 mm Hg and, further, that air is about 21% oxygen, then the partial pressure of oxygen in the air is 0.21 times 760 mm Hg or 160 mm Hg.