NEET MDS Synopsis
The Auditory Ossicles
AnatomyThe Auditory Ossicles
The Malleus
Its superior part, the head, lies in the epitympanic recess.
The head articulates with the incus.
The neck, lies against the flaccid part of the tympanic membrane.
The chorda tympani nerve crosses the medial surface of the neck of the malleus.
The handle of the malleus (L. hammer) is embedded in the tympanic membrane and moves with it.
The tendon of the tensor tympani muscle inserts into the handle.
The Incus
Its large body lies in the epitympanic recess where it articulates with the head of the malleus.
The long process of the incus (L. an anvil) articulates with the stapes.
The short process is connected by a ligament to the posterior wall of the tympanic cavity.
The Stapes
The base (footplate) of the stapes (L. a stirrup), the smallest ossicle, fits into the fenestra vestibuli or oval window on the medial wall of the tympanic cavity.
Functions of the Auditory Ossicles
The auditory ossicles increase the force but decrease the amplitude of the vibrations transmitted from the tympanic membrane.
Non-odontogenic cysts
Oral Pathology
Nasopalatine cyst
Radiology
The nasopalatine cyst appears as a well-defined, round radiolucency in the midline of the anterior maxilla . Sometimes it appears to be 'heart-shaped' because of super-imposition of the anterior nasal spine.
Radiological assessment should include examination of the lamina dura of the central incisors (to exclude a radicular cyst) and assessment of size (the nasopalatine foramen may reach a width of as much as 10 mm).
Pathology
The cyst is lined by a layer of pseudostratified ciliated columnar epithelium and/or stratified squamous epithelium. The capsule of the cyst is fibrous and may include the incisive canal neurovascular bundle.
Nasolabial cyst
Radiology
'Bowing' inwards of the anterolateral margin of the nasal cavity has been recorded
Pathology
The nasolabial cyst is lined by non-ciliated pseudostratified columnar epithelium, which is often rich in mucous cells.
Immunohistochemistry
General Pathology
Immunohistochemistry
This is a method is used to detect a specific antigen in the tissue in order to identify the type of disease.
Root canal Types
Endodontics
Common Canal Configurations:
There are many combinations of canals that are present in the roots of human permanent dentition, most of these root canal systems in any one root can be categorized in six different types. These six types are:
Type I : Single canal from pulp chamber to the apex.
Type II : Two separate canals leaving the chamber but merging short of the apex to form only one canal.
Type III : Two separate canals leaving the chamber and existing the root in separate apical foramina.
Type IV : One canal leaving the pulp chamber but dividing short of the apex into two separate canals with two separate apical foramina.
Type V : One canal that divides into two in the body of the root but returns to exist as one apical foramen.
Type VI : Two canals that merge in the body of the root but re-divide to exist into two apical foramina.
Root Canal Classes:
Another classification has been developed to describe the completion of root canal formation and curvature.
Class I : Mature straight root canal.
Class II : Mature but complicated root canal having-severe curvature, S-shaped course, dilacerations or bayonet curve.
Class III : Immature root canal either tubular or blunder bass.
SEQUENCE OF ERUPTION OF DECIDUOUS TEETH
Orthodontics
SEQUENCE OF ERUPTION OF DECIDUOUS TEETH
Upper/Lower A B D C E
SEQUENCE OF ERUPTION OF PERMAMENT TEETH
Upper: 6 1 2 4 3 5 7 Lower: 6 1 2 3 4 5 7
or 6 1 2 4 5 3 7 or 6 1 2 4 3 5 7
ANTHROPOID SPACE / PRIMATE SPACE / SIMIEN’S SPACE
The space mesial to upper deciduous canine and distal to lower deciduous canine is characteristically found in primates and hence it is called primate space.
INCISOR LIABILITY
When the permanent central incisor erupt, these teeth use up specially all the spaces found in the normal dentition. With the eruption of permanent lateral incisor the space situation becomes tight. In the maxillary arch it is just enough to accommodate but in mandibular arch there is an average 1.6 mm less space available. This difference between the space present and space required is known as incisor liability.
These conditions overcome by;
1. This is a transient condition and extra space comes from slight increase in arch width.
2. Slight labial positioning of central and lateral incisor.
3. Distal shift of permanent canine.
LEE WAY SPACE (OF NANCE)
The combined mesiodistal width of the permanent canines and pre molars is usually less that of the deciduous canines and molars. This space is
called leeway space of Nance.
Measurement of lee way space:
Is greater in the mandibular arch than in the maxillary arch It is about 1.8mm [0.9mm on each side of the arch] in the maxillary arch.
And about 3.4mm [1.7 mm on side of the arch] in the mandibular arch.
Importance:
This lee way space allows the mesial movement of lower molar there by correcting flush terminal plane.
LWS can be measure with the help of cephalometry.
FLUSH TERMINAL PLANE (TERMINAL PLANE RELATIONSHIP)
Mandibular 2nd deciduous molar is usually wider mesio-distally then the maxillary 2nd deciduous molar. This leads to the development of flush terminal plane which falls along the distal surface of upper and lower 2nd deciduous molar. This develops into class I molar relationship.
Distal step relationship leads to class 2 relationship.
Mesial step relationship mostly leads to class 3 relationship.
FEATURE OF IDEAL OCCLUSION IN PRIMARY DENTITION
1. Spacing of anterior teeth.
2. Primate space is present.
3. Flush terminal plane is found.
4. Almost vertical inclination of anterior teeth.
5. Overbite and overjet varies.
UGLY DUCKLING STAGE
Definition:
Stage of a transient or self correcting malocclusion is seen sometimes is called ugly duck ling stage.
Occurring site: Maxillary incisor region
Occuring age: 8-9 years of age.
This situation is seen during the eruption of the permanent canines. As the developing p.c. they displace the roots of lateral incisor mesially this results is transmitting of the force on to the roots of the central incisors which also gets displaced mesially. A resultant distal divergence of the crowns of the two central incisors causes midline spacing.
This portion of teeth at this stage is compared to that of ugly walk of the duckling and hence it is called Ugly Duckling Stage.
Described by Broad bent. In this stage children tend to look ugly. Parents are often apprehensive during this stage and consult the dentist.
Corrects by itself, when canines erupt and the pressure is transferred from the roots to the coronal area of the incisor.
IMPORTANCE OF 1ST MOLAR
1. It is the key tooth to occlusion.
2. Angle’s classification is based on this tooth.
3. It is the tooth of choice for anchorage.
4. Supports occlusion in a vertical direction.
5. Loss of this tooth leads to migration of other tooth.
6. Helps in opening the bite.
Mercury hygiene
Dental Materials
Mercury hygiene
Do not contact mercury with skin
Clean up spills to minimize mercury vaporization
Store mercury or precapsulated products in tight containers
Only triturate amalgam components-in tightly- sealed capsules
Use amalgam with covers
Store spent amalgam under water or fixer in a tightly sealed jar
Use high vacuum suction during amalgam alloy placement, setting, or removal when mercury may be vaporized
Polishing amalgams generally causes localized melting of silver-mercury phase with release of mercury vapor, so water cooling and evacuation must be used
Huntington’s disease
General Pathology
Huntington’s disease
a. Causes dementia.
b. Genetic transmission: autosomal dominant.
c. Characterized by the degeneration of striatal neurons, affecting cortical and basal ganglia function.
d. Clinically, the disease affects both movement and cognition and is ultimately fatal.
Headgear
OrthodonticsHeadgear is an extraoral orthodontic appliance used to
correct dental and skeletal discrepancies, particularly in growing patients. It
is designed to apply forces to the teeth and jaws to achieve specific
orthodontic goals, such as correcting overbites, underbites, and crossbites, as
well as guiding the growth of the maxilla (upper jaw) and mandible (lower jaw).
Below is an overview of headgear, its types, mechanisms of action, indications,
advantages, and limitations.
Types of Headgear
Class II Headgear:
Description: This type is used primarily to correct
Class II malocclusions, where the upper teeth are positioned too far
forward relative to the lower teeth.
Mechanism: It typically consists of a facebow that
attaches to the maxillary molars and is anchored to a neck strap or a
forehead strap. The appliance applies a backward force to the maxilla,
helping to reposition it and/or retract the upper incisors.
Class III Headgear:
Description: Used to correct Class III
malocclusions, where the lower teeth are positioned too far forward
relative to the upper teeth.
Mechanism: This type of headgear may use a
reverse-pull face mask that applies forward and upward forces to the
maxilla, encouraging its growth and improving the relationship between
the upper and lower jaws.
Cervical Headgear:
Description: This type is used to control the
growth of the maxilla and is often used in conjunction with other
orthodontic appliances.
Mechanism: It consists of a neck strap that
connects to a facebow, applying forces to the maxilla to restrict its
forward growth while allowing the mandible to grow.
High-Pull Headgear:
Description: This type is used to control the
vertical growth of the maxilla and is often used in cases with deep
overbites.
Mechanism: It features a head strap that connects
to the facebow and applies upward and backward forces to the maxilla.
Mechanism of Action
Force Application: Headgear applies extraoral forces to
the teeth and jaws, influencing their position and growth. The forces can be
directed to:
Restrict maxillary growth: In Class II cases,
headgear can help prevent the maxilla from growing too far forward.
Promote maxillary growth: In Class III cases,
headgear can encourage forward growth of the maxilla.
Reposition teeth: By applying forces to the molars,
headgear can help align the dental arches and improve occlusion.
Indications for Use
Class II Malocclusion: To correct overbites and improve
the relationship between the upper and lower teeth.
Class III Malocclusion: To promote the growth of the
maxilla and improve the occlusal relationship.
Crowding: To create space for teeth by retracting the
upper incisors.
Facial Aesthetics: To improve the overall facial
profile and aesthetics by modifying jaw relationships.
Advantages of Headgear
Non-Surgical Option: Provides a way to correct skeletal
discrepancies without the need for surgical intervention.
Effective for Growth Modification: Particularly useful
in growing patients, as it can influence the growth of the jaws.
Improves Aesthetics: Can enhance facial aesthetics by
correcting jaw relationships and improving the smile.
Limitations of Headgear
Patient Compliance: The effectiveness of headgear
relies heavily on patient compliance. Patients must wear the appliance as
prescribed (often 12-14 hours a day) for optimal results.
Discomfort: Patients may experience discomfort or
soreness when first using headgear, which can affect compliance.
Adjustment Period: It may take time for patients to
adjust to wearing headgear, and they may need guidance on how to use it
properly.
Limited Effectiveness in Adults: While headgear is
effective in growing patients, its effectiveness may be limited in adults
due to the maturity of the skeletal structures.