NEET MDS Synopsis
Hepatitis D and E virus
General Pathology
Hepatitis D virus—can only infect cells previously infected with hepatitis B.
Delta hepatitis (HDV) is associated with a 35-nm RNA virus composed of a delta antigen-bearing core surrounded by HBV's Ag coat;
HDV requires HBV for replication.
Delta hepatitis can cause quiescent HBV states to suddenly worsened . Its transmission is the same as that of HBV.
Hepatitis E virus—a high mortality rate in infected pregnant women.
Hepatitis E (HEV) is caused by a single-stranded RNA virus. The disease is typically self-limited and does not evolve into chronic hepatitis; it may, however, be cholestatic.
Pregnant women may develop fulminant disease.
Transmission is by the fecal oral route.
HEV occurs mainly in India, Nepal, Pakistan, and Southeast Asia.
Onlay Preparation
Conservative DentistryOnlay Preparation
Onlay preparations are a type of indirect restoration used to restore teeth
that have significant loss of structure but still retain enough healthy tooth
structure to support a restoration. Onlays are designed to cover one or more
cusps of a tooth and are often used when a full crown is not necessary.
1. Definition of Onlay
A. Onlay
An onlay is a restoration that is
fabricated using an indirect procedure, covering one or more cusps of a
tooth. It is designed to restore the tooth's function and aesthetics while
preserving as much healthy tooth structure as possible.
2. Indications for Onlay Preparation
Extensive Caries: When a tooth has significant decay
that cannot be effectively treated with a filling but does not require a
full crown.
Fractured Teeth: For teeth that have fractured cusps or
significant structural loss.
Strengthening: To reinforce a tooth that has been
weakened by previous restorations or caries.
3. Onlay Preparation Procedure
A. Initial Assessment
Clinical Examination: Assess the extent of caries or
damage to determine if an onlay is appropriate.
Radiographic Evaluation: Use X-rays to evaluate the
tooth structure and surrounding tissues.
B. Tooth Preparation
Burs Used:
Commonly used burs include No. 169 L for initial cavity preparation
and No. 271 for refining the preparation.
Cavity Preparation:
Occlusal Entry: The initial occlusal entry should
be approximately 1.5 mm deep.
Divergence of Walls: All cavity walls should
diverge occlusally by 2-5 degrees:
2 degrees: For short vertical walls.
5 degrees: For long vertical walls.
Proximal Box Preparation:
The proximal box margins should clear adjacent teeth by 0.2-0.5 mm,
with 0.5 ± 0.2 mm being ideal.
C. Bevels and Flares
Facial and Lingual Flares:
Primary and secondary flares should be created on the facial and
lingual proximal walls to form the walls in two planes.
The secondary flare widens the proximal box, allowing for better
access and cleaning.
Gingival Bevels:
Should be 0.5-1 mm wide and blend with the secondary flare,
resulting in a marginal metal angle of 30 degrees.
Occlusal Bevels:
Present on the cavosurface margins of the cavity on the occlusal
surface, approximately 1/4th the depth of the respective wall, resulting
in a marginal metal angle of 40 degrees.
4. Dimensions for Onlay Preparation
A. Depth of Preparation
Occlusal Depth: Approximately 1.5 mm to ensure adequate
thickness of the restorative material.
Proximal Box Depth: Should be sufficient to accommodate
the onlay while maintaining the integrity of the tooth structure.
B. Marginal Angles
Facial and Lingual Margins: Should be prepared with a
30-degree angle for burnishability and strength.
Enamel Margins: Ideally, the enamel margins should be
blunted to a 140-degree angle to enhance strength.
C. Cusp Reduction
Cusp Coverage: Cusp reduction is indicated when more
than 1/2 of a cusp is involved, and mandatory when 2/3 or more is involved.
Uniform Metal Thickness: The reduction must provide for
a uniform metal thickness of approximately 1.5 mm over the reduced cusps.
Facial Cusp Reduction: For maxillary premolars and
first molars, the reduction of the facial cusp should be 0.75-1 mm for
esthetic reasons.
D. Reverse Bevel
Definition: A bevel on the margins of the reduced cusp,
extending beyond any occlusal contact with opposing teeth, resulting in a
marginal metal angle of 30 degrees.
5. Considerations for Onlay Preparation
Retention and Resistance: The preparation should be
designed to maximize retention and resistance form, which may include the
use of proximal retentive grooves and collar features.
Aesthetic Considerations: The preparation should
account for the esthetic requirements, especially in anterior teeth or
visible areas.
Material Selection: The choice of material (e.g., gold,
porcelain, composite) will influence the preparation design and dimensions.
Sub-Stages of Adolescence
PedodonticsThree Sub-Stages of Adolescence
Adolescence is a critical developmental period characterized by significant
physical, emotional, and social changes. It is typically divided into three
sub-stages: early adolescence, middle adolescence, and late adolescence. Each
sub-stage has distinct characteristics that influence the development of
identity, social relationships, and behavior.
Sub-Stages of Adolescence
1. Early Adolescence (Approximately Ages 10-13)
Characteristics:
Casting Off of Childhood Role: This stage marks the
transition from childhood to adolescence. Children begin to distance
themselves from their childhood roles and start to explore their
emerging identities.
Physical Changes: Early physical development
occurs, including the onset of puberty, which brings about changes in
body shape, size, and secondary sexual characteristics.
Cognitive Development: Adolescents begin to think
more abstractly and critically, moving beyond concrete operational
thinking.
Emotional Changes: Increased mood swings and
emotional volatility are common as adolescents navigate their new
feelings and experiences.
Social Changes: There is a growing interest in peer
relationships, and friendships may begin to take on greater importance
- Exploration of Interests: Early adolescents often
start to explore new interests and hobbies, which can lead to the
formation of new social groups.
2. Middle Adolescence (Approximately Ages 14-17)
Characteristics:
Participation in Teenage Subculture: This stage is
characterized by a deeper involvement in peer groups and the teenage
subculture, where social acceptance and belonging become paramount.
Identity Formation: Adolescents actively explore
different aspects of their identity, including personal values, beliefs,
and future aspirations.
Increased Independence: There is a push for greater
autonomy from parents, leading to more decision-making and
responsibility.
Romantic Relationships: The exploration of romantic
relationships becomes more prominent, influencing social dynamics and
emotional experiences.
Risk-Taking Behavior: Middle adolescents may engage
in risk-taking behaviors as they seek to assert their independence and
test boundaries.
3. Late Adolescence (Approximately Ages 18-21)
Characteristics:
Emergence of Adult Behavior: Late adolescence is
marked by the transition into adulthood, where individuals begin to take
on adult roles and responsibilities.
Refinement of Identity: Adolescents solidify their
sense of self, integrating their experiences and values into a coherent
identity.
Future Planning: There is a focus on future goals,
including education, career choices, and long-term relationships.
Social Relationships: Relationships may become more
mature and stable, with a shift from peer-focused interactions to deeper
connections with family and romantic partners.
Cognitive Maturity: Cognitive abilities continue to
develop, leading to improved problem-solving skills and critical
thinking.
Most Common Site of Primary Bone Tumors
Orthopaedics
Most Common Site of Primary Bone Tumors
Epiphyseal
- Chondroblastoma (before physeal closure)
- Osteoclastom/Giant cell tumor (after physeal closure in adults)
- Articular osteochondroma
Metaphyseal
- Chondrosarcoma
- Enchondroma
- Osteochondroma
- Osteoblastoma
- Bone cyst
- Osteosarcorna
- Osteoclastoma (in children)
- Osteomyelitis mostly starts in metaphysis
?Diaphyseal
- Round cell lesions: Ewing’s sarcoma/Multiple myeloma /Reticulum cell sarcoma
- Admantinoma
- Osteoid osteoma
DISTORTION OF THE PATTERN
Dental Materials
DISTORTION OF THE PATTERN
Distortion is dependant on temperature & time interval before investing .
To avoid any distortion ,
Invest the pattern as soon as possible .
Proper handling of the pattern .
PREREQUISITES
Wax pattern should be evaluated for smoothness , finish & contour .
Pattern is inspected under magnification & residual flash is removed .
Periodontal Bone Grafts
PeriodontologyPeriodontal Bone Grafts
Bone grafting is a critical procedure in periodontal surgery, aimed at
restoring lost bone and supporting the regeneration of periodontal tissues.
1. Bone Blend
Bone blend is a mixture of cortical or cancellous bone that is procured using a trephine or rongeurs, placed in an
amalgam capsule, and triturated to achieve a slushy osseous mass. This technique
allows for the creation of smaller particle sizes, which enhances resorption and
replacement with host bone.
Particle Size: The ideal particle size for bone blend is
approximately 210 x 105 micrometers.
Rationale: Smaller particle sizes improve the chances of
resorption and integration with the host bone, making the graft more effective.
2. Types of Periodontal Bone Grafts
A. Autogenous Grafts
Autogenous grafts are harvested from the patient’s own body, providing the
best compatibility and healing potential.
Cortical Bone Chips
History: First used by Nabers and O'Leary in 1965.
Characteristics: Composed of shavings of cortical
bone removed during osteoplasty and ostectomy from intraoral sites.
Challenges: Larger particle sizes can complicate
placement and handling, and there is a potential for sequestration. This
method has largely been replaced by autogenous osseous coagulum and bone
blend.
Osseous Coagulum and Bone Blend
Technique: Intraoral bone is obtained using high-
or low-speed round burs and mixed with blood to form an osseous coagulum
(Robinson, 1969).
Advantages: Overcomes disadvantages of cortical
bone chips, such as inability to aspirate during collection and
variability in quality and quantity of collected bone.
Applications: Used in various periodontal
procedures to enhance healing and regeneration.
Intraoral Cancellous Bone and Marrow
Sources: Healing bony wounds, extraction sockets,
edentulous ridges, mandibular retromolar areas, and maxillary
tuberosity.
Applications: Provides a rich source of osteogenic
cells and growth factors for bone regeneration.
Extraoral Cancellous Bone and Marrow
Sources: Obtained from the anterior or posterior
iliac crest.
Advantages: Generally offers the greatest potential
for new bone growth due to the abundance of cancellous bone and marrow.
B. Bone Allografts
Bone allografts are harvested from donors and can be classified into three
main types:
Undermineralized Freeze-Dried Bone Allograft (FDBA)
Introduction: Introduced in 1976 by Mellonig et al.
Process: Freeze drying removes approximately 95% of
the water from bone, preserving morphology, solubility, and chemical
integrity while reducing antigenicity.
Efficacy: FDBA combined with autogenous bone is
more effective than FDBA alone, particularly in treating furcation
involvements.
Demineralized (Decalcified) FDBA
Mechanism: Demineralization enhances osteogenic
potential by exposing bone morphogenetic proteins (BMPs) in the bone
matrix.
Osteoinduction vs. Osteoconduction: Demineralized
grafts induce new bone formation (osteoinduction), while
undermineralized allografts facilitate bone growth by providing a
scaffold (osteoconduction).
Frozen Iliac Cancellous Bone and Marrow
Usage: Used sparingly due to variability in
outcomes and potential complications.
Comparison of Allografts and Alloplasts
Clinical Outcomes: Both FDBA and DFDBA have been
compared to porous particulate hydroxyapatite, showing little difference in
post-treatment clinical parameters.
Histological Healing: Grafts of DFDBA typically heal
with regeneration of the periodontium, while synthetic bone grafts (alloplasts)
heal by repair, which may not restore the original periodontal architecture.
The Soft Palate
Anatomy
This is the posterior curtain-like part, and has no bony support. It does, however, contain a membranous aponeurosis.
The soft palate, or velum palatinum (L. velum, veil), is a movable, fibromuscular fold that is attached to the posterior edge of the hard palate.
It extends posteroinferiorly to a curved free margin from which hangs a conical process, the uvula (L. uva, grape).
The soft palate separates the nasopharynx superiorly and the oropharynx inferiorly.
During swallowing the soft palate moves posteriorly against the wall of the pharynx, preventing the regurgitation of food into the nasal cavity.
Laterally, the soft palate is continuous with the wall of the pharynx and is joined to the tongue and pharynx by the palatoglossal and palatopharyngeal folds.
The soft palate is strengthened by the palatine aponeurosis, formed by the expanded tendon of the tensor veli palatini muscle.
This aponeurosis attaches to the posterior margin of the hard palate.
Physiologic anatomy of the respiratory system
PhysiologyRespiration occurs in three steps :
1- Mechanical ventilation : inhaling and exhaling of air between lungs and atmosphere.
2- Gas exchange : between pulmonary alveoli and pulmonary capillaries.
3- Transport of gases from the lung to the peripheral tissues , and from the peripheral tissues back to blood .
These steps are well regulated by neural and chemical regulation.
Respiratory tract is subdivided into upper and lower respiratory tract. The upper respiratory tract involves , nose , oropharynx and nasopharynx , while the lower respiratory tract involves larynx , trachea , bronchi ,and lungs .
Nose fulfills three important functions which are :
1. warming of inhaled air .
b. filtration of air .
c. humidification of air .
Pharynx is a muscular tube , which forms a passageway for air and food .During swallowing the epiglottis closes the larynx and the bolus of food falls in the esophagus .
Larynx is a respiratory organ that connects pharynx with trachea . It is composed of many cartilages and muscles and
vocal cords . Its role in respiration is limited to being a conductive passageway for air .
Trachea is a tube composed of C shaped cartilage rings from anterior side, and of muscle (trachealis muscle ) from its posterior side.The rings prevent trachea from collapsing during the inspiration.
From the trachea the bronchi are branched into right and left bronchus ( primary bronchi) , which enter the lung .Then they repeatedly branch into secondary and tertiary bronchi and then into terminal and respiratory broncholes.There are about 23 branching levels from the right and left bronchi to the respiratory bronchioles , the first upper 17 branching are considered as a part of the conductive zones , while the lower 6 are considered to be respiratory zone.
The cartilaginous component decreases gradually from the trachea to the bronchioles . Bronchioles are totally composed of smooth muscles ( no cartilage) . With each branching the diameter of bronchi get smaller , the smallest diameter of respiratory passageways is that of respiratory bronchiole.
Lungs are evolved by pleura . Pleura is composed of two layers : visceral and parietal .
Between the two layers of pleura , there is a pleural cavity , filled with a fluid that decrease the friction between the visceral and parietal pleura.
Respiratory muscles : There are two group of respiratory muscles:
1. Inspiratory muscles : diaphragm and external intercostal muscle ( contract during quiet breathing ) , and accessory inspiratory muscles : scaleni , sternocleidomastoid , internal pectoral muscle , and others( contract during forceful inspiration).
2. Expiratory muscles : internal intercostal muscles , and abdominal muscles ( contract during forceful expiration)