NEET MDS Synopsis
Hockey Stick or London Hospital Elevator
Oral and Maxillofacial SurgeryHockey Stick or London Hospital Elevator
The Hockey Stick Elevator, also known as the London
Hospital Elevator, is a dental instrument used primarily in oral
surgery and tooth extraction procedures. It is designed to facilitate the
removal of tooth roots and other dental structures.
Design and Features
Blade Shape: The Hockey Stick Elevator features a
straight blade that is angled relative to the shank, similar to the Cryer’s
elevator. However, unlike the Cryer’s elevator, which has a
triangular blade, the Hockey Stick Elevator has a straight blade with a
convex surface on one side and a flat surface on the other.
Working Surface:
The flat surface of the blade is the working
surface and is equipped with transverse serrations.
These serrations enhance the instrument's grip and contact with the root
stump, allowing for more effective leverage during extraction.
Appearance: The instrument resembles a hockey stick,
which is how it derives its name. The distinctive shape aids in its
identification and use in clinical settings.
Principles of Operation
Lever and Wedge Principle:
The Hockey Stick Elevator operates on the same principles as the
Cryer’s elevator, utilizing the lever and wedge principle.
This means that the instrument can be used to apply force to the tooth
or root, effectively loosening it from the surrounding bone and
periodontal ligament.
Functionality:
The primary function of the Hockey Stick Elevator is to elevate and
luxate teeth or root fragments during extraction procedures. It can be
particularly useful in cases where the tooth is impacted or has a curved
root.
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
Methadone
Pharmacology
Methadone
Pharmacology and analgesic potency similar to morphine.
Very effective following oral administration.
Longer duration of action than morphine due to plasma protein binding (t1/2 approximately 25 hrs).
Used in methadone maintenance programs for drug addicts and for opiate withdrawal. Opiate withdrawal is more prolonged but is less intense than it is following morphine or heroin.
Lymphomas
General Pathology
Lymphomas
A. Hodgkin’s disease
1. Characterized by enlarged lymph nodes and the presence of Reed-Sternberg cells (multinucleated giant cells) in lymphoid tissues.
2. Disease spreads from lymph node to lymph node in a contiguous manner.
3. Enlarged cervical lymph nodes are most commonly the first lymphadenopathy observed.
4. The cause is unknown.
5. Occurs before age 30.
6. Prognosis of disease depends largely on the extent of lymph node spread and systemic involvement.
B. Non-Hodgkin’s lymphoma
1. Characterized by tumor formation in the lymph nodes.
2. Tumors do not spread in a contiguous manner.
3. Most often caused by the proliferation of abnormal B cells.
4. Occurs after age 40.
5. Example: Burkitt’s lymphoma
a. Commonly associated with an EpsteinBarr virus (EBV) infection and a genetic mutation resulting from the translocation of the C-myc gene from chromosome 8 to 14.
b. The African type occurs in African children and commonly affects the mandible or maxilla.
c. In the United States, it most commonly affects the abdomen.
d. Histologically, the tumor displays a characteristic “starry-sky” appearance.
The Palate
AnatomyThe Palate
The palate forms the arched roof of the mouth and the floor of the nasal cavities.
The palate consists of two regions: the anterior 2/3 or bony part, called the hard palate, and the mobile posterior 1/3 or fibromuscular part, known as the soft palate.
The Hard Palate
The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.
Anteriorly and laterally, the hard palate is bounded by the alveolar processes and the gingivae.
Posteriorly, the hard palate is continuous with the soft palate.
The incisive foramen is the mouth of the incisive canal.
This foramen is located posterior to the maxillary central incisor teeth.
This foramen is the common opening for the right and left incisive canals.
The incisive canal and foramen transmit the nasopalatine nerve and the terminal branches of the sphenopalatine artery.
Medial to the third molar tooth, the greater palatine foramen pierces the lateral border of the bony palate.
The greater palatine vessels and nerve emerge from this foramen and run anteriorly into two grooves on the palate.
The lesser palatine foramen transmits the lesser palatine nerve and vessels.
This runs to the soft palate and adjacent structures.
Nutrition and tooth development
Dental Anatomy
Nutrition and tooth development
As in other aspects of human growth and development, nutrition has an effect on the developing tooth. Essential nutrients for a healthy tooth include calcium, phosphorus, fluoride, and vitamins A, C, and D. Calcium and phosphorus are needed to properly form the hydroxyapatite crystals, and their levels in the blood are maintained by Vitamin D. Vitamin A is necessary for the formation of keratin, as Vitamin C is for collagen. Fluoride is incorporated into the hydroxyapatite crystal of a developing tooth and makes it more resistant to demineralization and subsequent decay.
Deficiencies of these nutrients can have a wide range of effects on tooth development. In situations where calcium, phosphorus, and vitamin D are deficient, the hard structures of a tooth may be less mineralized. A lack of vitamin A can cause a reduction in the amount of enamel formation. Fluoride deficency causes increased demineralization when the tooth is exposed to an acidic environment, and also delays remineralization. Furthermore, an excess of fluoride while a tooth is in development can lead to a condition known as fluorosis.
Functional Matrix Hypothesis
OrthodonticsFunctional Matrix Hypothesis is a concept in orthodontics
and craniofacial biology that explains how the growth and development of the
craniofacial complex (including the skull, face, and dental structures) are
influenced by functional demands and environmental factors rather than solely by
genetic factors. This hypothesis was proposed by Dr. Robert A. K.
McNamara and is based on the idea that the functional matrices—such as
muscles, soft tissues, and functional activities (like chewing and
speaking)—play a crucial role in shaping the skeletal structures.
Concepts of the Functional Matrix Hypothesis
Functional Matrices:
The hypothesis posits that the growth of the craniofacial skeleton
is guided by the functional matrices surrounding it. These matrices
include:
Muscles: The muscles of mastication, facial
expression, and other soft tissues exert forces on the bones,
influencing their growth and development.
Soft Tissues: The presence and tension of soft
tissues, such as the lips, cheeks, and tongue, can affect the
position and growth of the underlying skeletal structures.
Functional Activities: Activities such as
chewing, swallowing, and speaking create functional demands that
influence the growth patterns of the craniofacial complex.
Growth and Development:
According to the Functional Matrix Hypothesis, the growth of the
craniofacial skeleton is not a direct result of genetic programming but
is instead a response to the functional demands placed on it. This means
that changes in function can lead to changes in growth patterns.
For example, if a child has a habit of mouth breathing, the lack of
proper nasal function can lead to altered growth of the maxilla and
mandible, resulting in malocclusion or other dental issues.
Orthodontic Implications:
The Functional Matrix Hypothesis has significant implications for
orthodontic treatment and craniofacial orthopedics. It suggests that:
Functional Appliances: Orthodontic appliances
that modify function (such as functional appliances) can be used to
influence the growth of the jaws and improve occlusion.
Early Intervention: Early orthodontic
intervention may be beneficial in guiding the growth of the
craniofacial complex, especially in children, to prevent or correct
malocclusions.
Holistic Approach: Treatment should consider
not only the teeth and jaws but also the surrounding soft tissues
and functional activities.
Clinical Applications:
The Functional Matrix Hypothesis encourages clinicians to assess the
functional aspects of a patient's oral and facial structures when
planning treatment. This includes evaluating muscle function, soft
tissue relationships, and the impact of habits (such as thumb sucking or
mouth breathing) on growth and development.
Pulmonary ventilation
PhysiologyVentilation simply means inhaling and exhaling of air from the atmospheric air into lungs and then exhaling it from the lung into the atmospheric air.
Air pressure gradient has to exist between two atmospheres to enable a gas to move from one atmosphere to an other.
During inspiration: the intrathoracic pressure has to be less than that of atmospheric pressure. This could be achieved by decreasing the intrathoracic pressure as follows:
Depending on Boyle`s law , the pressure of gas is inversely proportional to the volume of its container. So increasing the intrathoracic volume will decrease the intrathoracic pressure which will allow the atmospheric air to be inhaled (inspiration) . As decreasing the intrathoracic volume will increase the intrathoracic pressure and causes exhaling of air ( expiration)
So. Inspiration could be actively achieved by the contraction of inspiratory muscles : diaphragm and intercostal muscles. While relaxation of the mentioned muscles will passively cause expiration.
Contraction of diaphragm will pull the diaphragm down the abdominal cavity ( will move inferiorly) , and then increase the intrathoracic volume ( vertically) . Contraction of external intercostal muscle will pull the ribs upward and forward which will additionally increase the intrathoracic volume ( transversely , the net result will be increasing the intrathoracic volume and decreasing the intrathoracic pressure.
Relaxation of diaphragm will move it superiorly during expiration, the relaxation of external intercostal muscles will pull the ribs downward and backward , and the elastic lungs and chest wall will recoil. The net result is decreasing the intrathoracic volume and increasing intrathoracic pressure.
All of this occurs during quiet breathing. During forceful inspiration an accessory inspiratory muscle will be involved ( scaleni , sternocleidomastoid , and others) to increase negativity in the intrathoracic pressure more and more.
During forceful expiration the accessory expiratory muscles ( internal intercostal muscles and abdominal muscles ) will be involved to decrease the intrathoracic volume more and more and then to increase intrathoracic pressure more and more.
The pressure within the alveoli is called intralveolar pressure . Between the two phases of respiration it is equal to the atmospheric pressure. It is decreased during inspiration ( about 1 cm H2O ) and increased during expiration ( about +1 cm H2O ) . This difference allow entering of 0.5 L of air into the lungs.
Intrapleural pressure is the pressure of thin fluid between the two pleural layers . It is a slight negative pressure. At the beginning of inspiration it is about -5 cm H2O and reachs -7.5 cm H2O at the end or inspiration.
At the beginning of expiration the intrapleural pressure is -7.5 cm H2O and reaches -5 cmH2O at the end of expiration.
The difference between intralveolar pressure and intrapleural pressure is called transpulmonary pressure.
Factors , affecting ventilation :
Resistance : Gradual decreasing of the diameter of respiratory airway increase the resistance to air flow.
Compliance : means the ease , which the lungs expand.It depends on both the elastic forces of the lungs and the elastic forces , caused by the the surface tension of the fluid, lining the alveoli.
Surface tension: Molecules of water have tendency to attract each other on the surface of water adjacent to air. In alveoli the surface tension caused by the fluid in the inner surface of the alveoli may cause collapse of alveoli . The surface tension is decreased by the surfactant .
Surfactant is a mixture of phospholipids , proteins and ion m produced by type II pneumocytes.
Immature newborns may suffer from respiratory distress syndrome , due to lack of surfactant which is produced during the last trimester of pregnancy.
The elastic fibers of the thoracic wall also participate in lung compliance.