NEET MDS Synopsis
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.
Velopharyngeal Insufficiency (VPI)
Oral and Maxillofacial SurgeryVelopharyngeal Insufficiency (VPI)
Velopharyngeal insufficiency (VPI) is
characterized by inadequate closure of the nasopharyngeal airway during speech
production, leading to speech disorders such as hypernasality and nasal
regurgitation. This condition is particularly relevant in patients who have
undergone cleft palate repair, as the surgical success does not always guarantee
proper function of the velopharyngeal mechanism.
Etiology of VPI
The etiology of VPI following cleft palate repair is multifactorial and can
include:
Inadequate Surgical Repair: Insufficient repair of the
musculature involved in velopharyngeal closure can lead to persistent VPI.
This may occur if the muscles are not properly repositioned or if there is
inadequate tension in the repaired tissue.
Anatomical Variations: Variations in the anatomy of the
soft palate, pharynx, and surrounding structures can contribute to VPI.
These variations may not be fully addressed during initial surgical repair.
Neuromuscular Factors: Impaired neuromuscular function
of the muscles involved in velopharyngeal closure can also lead to VPI,
which may not be correctable through surgical means alone.
Surgical Management of VPI
Pharyngoplasty: One of the surgical options for managing VPI
is pharyngoplasty, which aims to improve the closure of the nasopharyngeal port
during speech.
Historical Background: The procedure was first
described by Hynes in 1951 and has since been modified by various authors to
enhance its effectiveness and reduce complications.
Operative Procedure
Flap Creation: The procedure involves the creation of
two superiorly based myomucosal flaps from each posterior tonsillar pillar.
Care is taken to include as much of the palatopharyngeal muscle as possible
in the flaps.
Flap Elevation: The flaps are elevated carefully to
preserve their vascular supply and muscular integrity.
Flap Insetting: The flaps are then attached and inset
within a horizontal incision made high on the posterior pharyngeal wall.
This technique aims to create a single nasopharyngeal port rather than the
two ports typically created with a superiorly based pharyngeal flap.
Contractile Ridge Formation: The goal of the procedure
is to establish a contractile ridge posteriorly, which enhances the function
of the velopharyngeal valve, thereby improving closure during speech.
Advantages of Sphincter Pharyngoplasty
Lower Complication Rate: One of the main advantages of
sphincter pharyngoplasty over the traditional superiorly based flap
technique is the lower incidence of complications related to nasal airway
obstruction. This is particularly important for patient comfort and quality
of life post-surgery.
Improved Speech Outcomes: By creating a more effective
velopharyngeal mechanism, patients often experience improved speech
outcomes, including reduced hypernasality and better articulation.
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.
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.
Characteristics of Immunoglobulin subclasses
General Pathology
Characteristics of Immunoglobulin subclasses
I. Ig G:
(i) Predominant portion (80%) of Ig.
(ii) Molecular weight 150, 000
(iii) Sedimentation coefficient of 7S.
(iv) Crosses placental barrier and to extra cellular fluid.
(v) Mostly neutralising effect. May be complement fixing.
(vi) Half life of 23 days.
2.IgM :
(i) Pentamer of Ig.
(ii) Molecular weight 900, 000
(iii) 19S.
(iv) More effective complement fixation and cells lysis
(v) Earliest to be produced in infections.
(vi) Does not cross placental barrier.
(vii) Halflife of 5 days.
3. Ig A :
Secretory antibody. Found in intestinal, respiratory secretions tears, saliva and urine also.
Secreted usually as a dinner with secretory piece.
Mol. weight variable (160,000+)
7 S to 14 S.
Half life of 6 days.
4.Ig D :
Found in traces.
7 S.
Does not cross placenta.
5. Ig E
Normally not traceable
7-8 S (MoL weight 200,000)
Cytophilic antibody, responsible for some hypersensitivity states,
Self-Mutilation in Children
Pedodontics
Self-Mutilation in Children: Causes and Management
Overview of Self-Mutilation
Self-mutilation through biting and other forms of self-injury can be a
significant concern in children, particularly those with severe emotional
disturbances or specific syndromes. Understanding the underlying causes and
appropriate management strategies is essential for healthcare providers.
Associated Conditions
Lesch-Nyhan Syndrome (LNS):
A genetic disorder characterized by hyperuricemia, neurological
impairment, and self-mutilating behaviors, including biting and head
banging.
Children with LNS often exhibit severe emotional disturbances and may
engage in self-injurious behaviors.
Congenital Insensitivity to Pain:
A rare condition where individuals cannot feel physical pain, leading to
a higher risk of self-injury due to the inability to recognize harmful
stimuli.
Children with this condition may bite or injure themselves without
understanding the consequences.
Autism:
Children with autism may engage in self-injurious behaviors, including
biting, as a response to sensory overload, frustration, or communication
difficulties.
Friedlander and colleagues noted that facial bruising, abrasions, and
intraoral traumatic ulcerations in autistic children are often the
result of self-injurious behaviors rather than abuse.
Management Strategies
Management of self-mutilation in children requires careful consideration of the
underlying condition and the child's developmental stage. Two primary approaches
are often discussed:
Protective Appliances:
Mouthguards:
Littlewood and Mitchell reported that mouthguards can be beneficial
for children with congenital insensitivity to pain. These devices
help protect the oral cavity from self-inflicted injuries.
Mouthguards can serve as a temporary measure until the child matures
enough to understand and avoid self-mutilating behaviors, which is
typically learned through painful experiences.
Surgical Procedures:
In some cases, surgical intervention may be necessary to address severe
self-injurious behaviors or to repair damage caused by biting.
The decision to pursue surgical options should be made on a case-by-case
basis, considering the child's overall health, the severity of the
behaviors, and the potential for improvement.
Pharmacological Interventions:
Carbamazepine:
Cusumano and colleagues reported that carbamazepine may be
beneficial for children with Lesch-Nyhan syndrome. This medication
can help manage behavioral symptoms and reduce self-injurious
behaviors.
PHYSICAL AGENTS
General Microbiology
PHYSICAL AGENTS
Heat occupies the most important place as a physical agent.
Moist Heat : This is heating in the presence of water and can be employed in the following ways:
Temperature below 100°C: This includes holder method of Pasteurization where 60°C for 30 minutes is employed for sterilization and in its flash modification where in objects are subjected to a temperature of 71.1°C for 15 seconds. This method does not destroy spores.
Temperatures Around 100°C : Tyndallization is an example of this methodology in which steaming of the object is done for 30 minutes on each of three consecutive days. Spores which survive the heating process would germinate before the next thermal exposure and would then be killed.
Temperatures Above 100°C : Dry saturated steam acts as an excellent agent for sterilization. Autoclaves have been designed on the principles of moist heat.
Time-temperature relationship in heat sterilization
Moist heat (autoclaving)
121°C 15 minutes
126°C 10 minutes
134 C 3 minutes
Dry heat
>160°C >120 minutes
>170°C >60minutes
>180°C >30 minutes
Mechanism of microbial inactivation
The autoclaving is in use for the sterilization of many ophthalmic and parentral products. surgical dressings, rubber gloves, bacteriological media as well a of lab and hospital reusable goods.
Dry Heat: Less efficient, bacterial spores are most resistant. Spores may require a temperature of 140° C for three hours to get killed.
Dry heat sterilization is usually carried out by flaming as is done in microbiology laboratory to sterilize the inoculating loop and in hot air ovens in which a number of time-temperature combinations can be used. It is essential that hot air should circulate between the objects to be sterilized. Microbial inactivation by dry heat is primarily an oxidation process.
Dry heat is employed for sterilization of glassware glass syringes, oils and oily injections as well as metal instruments. -
Indicators of Sterilization:
These determine the efficacy of heat sterilization and can be in the form of spores of Bacillus stearothermophilus (killed at 121C in 12 minutes) or in the form of chemical indicators, autoclave tapes and thermocouples.
Ionizing Radiations
Ionizing radiations include X-rays, gamma rays and beta rays, and these induce defects in the microbial DNA synthesis is inhibited resulting in cell death. Spores are more resistant to ionizing radiations than nonsporulating bacteria.
The ionizing radiations are used for the sterilization of single use disposable medical items.
Mechanism of microbial inactivation by moist heat
Bacterial spores
• Denaturation of spore_epzymes
• Impairment of germination
• Damage to cell membrane
• Increased sensitivity to inhibitory agents
• Structural damage
• Damage to chromosome
Nonsporulating bacteria
• Damage to cytoplasmic membrane
• Breakdown of RNA
• Coagulation of proteins
• Damage to bacterial chromosome
Ultraviolet Radiations :
wave length 240-280 nm have been found to be most efficient in sterilizing. Bacterial spores are more resistant to U.V. rays than the vegetative forms. Even viruses are sometimes more resistant than vegetative bacteria.
Mechanism of Action :
Exposure to UV rays results in the formation of purine and pyrimidine diamers between adjacent molecules in the same strand of DNA. This results into noncoding lesions in DNA and bacterial death.
Used to disinfect drinking water, obtaining pyrogen free water, air disinfection (especially in safety laboratories, hospitals, operation theatres) and in places where dangerous microorganisms are being handled.
Filteration
Type of Filters
Various types of filters that are available are /
Unglazed ceramic filter (Chamberland and Doulton filters)
Asbestos filters (Seitz, Carlson and Sterimat filters)
Sintered glass filters
Membrane filters
Membrane filters are widely used now a days. Made up of cellulose ester and are most suitable for preparing_sterile solutions. The range of pore size in which these are available is 0.05-12 µm whereas the required pore size for sterlization is in range of 0.2-0.22 p.m.
Refractory Material
Conservative DentistryRefractory materials are essential in the field of dentistry, particularly in
the branch of conservative dentistry and prosthodontics, for the fabrication of
various restorations and appliances. These materials are characterized by their
ability to withstand high temperatures without undergoing significant
deformation or chemical change. This is crucial for the longevity and stability
of the dental work. The primary function of refractory materials is to provide a
precise and durable mold or pattern for the casting of metal restorations, such
as crowns, bridges, and inlays/onlays.
Refractory materials include:
- Plaster of Paris: The most commonly used refractory material
in dentistry, plaster is composed of calcium sulfate hemihydrate. It is mixed
with water to form a paste that is used to make study models and casts. It has a
relatively low expansion coefficient and is easy to manipulate, making it
suitable for various applications.
- Dental stone: A more precise alternative to plaster, dental
stone is a type of gypsum product that offers higher strength and less
dimensional change. It is commonly used for master models and die fabrication
due to its excellent surface detail reproduction.
- Investment materials: Used in the casting process of fabricating indirect
restorations, investment materials are refractory and encapsulate the wax
pattern to create a mold. They can withstand the high temperatures required for
metal casting without distortion.
- Zirconia: A newer refractory material gaining popularity,
zirconia is a ceramic that is used for the fabrication of all-ceramic crowns and
bridges. It is extremely durable and has a high resistance to wear and fracture.
- Refractory die materials: These are used in the production of
metal-ceramic restorations. They are capable of withstanding the high
temperatures involved in the ceramic firing process and provide a reliable
foundation for the ceramic layers.
The selection of a refractory material is based on factors such as the intended
use, the required accuracy, and the specific properties needed for the final
restoration. The material must have a low thermal expansion coefficient to
minimize the thermal stress during the casting process and maintain the
integrity of the final product. Additionally, the material should be able to
reproduce the fine details of the oral anatomy and have good physical and
mechanical properties to ensure stability and longevity.
Refractory materials are typically used in the following procedures:
- Impression taking: Refractory materials are used to make models from the
patient's impressions.
- Casting of metal restorations: A refractory mold is created from the model to
cast the metal framework.
- Ceramic firing: Refractory die materials hold the ceramic in place while it is
fired at high temperatures.
- Temporary restorations: Some refractory materials can be used to produce
temporary restorations that are highly accurate and durable.
Refractory materials are critical for achieving the correct fit and function of
dental restorations, as well as ensuring patient satisfaction with the
aesthetics and comfort of the final product.