NEET MDS Synopsis
Enamel
Dental Anatomy
Enamel
Composition: 96% mineral, 4% organic material and water
Crystalline calcium phosphate, hydroxyapatite
Physical characteristics: Hardness compared to mild steel; enamel is brittle
Support from dentin is necessary
Enamel has varies in thickness
Structure of enamel
Ground sections of enamel disclose the information that we have about enamel
Enamel is composed of rods
In the past we used the term prism (do not use)
Enamel rod
The rod has a cylinder-like shape and is composed of crystals that run parallel to the longitudinal axis of the rod. At the periphery of the rod the crystals flare laterally.
Interrod region: surrounds each rod; contain more enamel protein (fish scale appearance)
Rod sheath: boundary where crystals of rods meet those of the interrod region at sharp angles (We used to describe that as a keyhole configuration)
Each ameloblast forms one rod and together with adjacent ameloblasts the interrod region Very close to dentin there is no rod structure since the Tomes' processes develop after the first enamel is formed.
Striae of Retzius and cross striations
Incremental lines
Enamel structure is altered along these lines
Cross striations are also a form of incremental lines highlighting the daily secretory activity of ameloblasts
Bands of Hunter and Schreger
Optical phenomenon produced by changes in rod direction
Gnarled enamel
Twisting of rods around each other over the cusps of teeth
Enamel tufts and lamellae
They are like geologic faults
Tufts project from the DE junction, appear branched and contain greater concentrations of enamel protein than enamel
Lamellae extend from the enamel surface
Enamel spindles
Perikymata
Shallow furrows on surface of enamel formed by the striae of Retzius
Visor osteotomy
Oral and Maxillofacial SurgeryVisor Osteotomy
Visor osteotomy is a surgical procedure primarily aimed at
increasing the height of the mandibular ridge to enhance denture support. This
technique is particularly beneficial for patients with resorbed or atrophic
mandibles, where the lack of adequate bone height can compromise the retention
and stability of dentures.
Goals of Visor Osteotomy
Increase Mandibular Ridge Height: The primary objective
is to augment the height of the mandibular ridge, providing a more favorable
foundation for denture placement.
Improve Denture Support: By increasing the ridge
height, the procedure aims to enhance the retention and stability of
dentures, leading to improved function and patient satisfaction.
Procedure Overview
Incision and Exposure:
A surgical incision is made in the oral mucosa to expose the
mandible.
The incision is typically placed along the vestibular area to
minimize scarring and optimize healing.
Central Splitting of the Mandible:
The mandible is carefully split in the buccolingual dimension. This
involves creating a central osteotomy that divides the mandible into two
sections.
The split allows for manipulation of the bone segments to achieve
the desired height.
Superior Positioning of the Lingual Section:
The lingual section of the mandible is then repositioned superiorly.
This elevation is crucial for increasing the height of the ridge.
The repositioned segment is stabilized using wires or other fixation
devices to maintain the new position during the healing process.
Bone Grafting:
Cancellous bone graft material is placed at the outer cortex over
the superior labial junction. This grafting material helps to improve
the contour of the mandible and provides additional support for the
overlying soft tissues.
The use of bone grafts can enhance the healing process and promote
new bone formation in the area.
Closure:
The surgical site is closed in layers, ensuring that the mucosa and
underlying tissues are properly approximated.
Postoperative care instructions are provided to the patient to
facilitate healing and minimize complications.
Indications
Atrophic Mandible: Patients with significant bone
resorption in the mandible, often seen in edentulous individuals, are prime
candidates for this procedure.
Denture Retention Issues: Individuals experiencing
difficulties with denture retention and stability due to inadequate ridge
height may benefit from visor osteotomy.
Benefits
Enhanced Denture Support: By increasing the height of
the mandibular ridge, patients can achieve better retention and stability of
their dentures.
Improved Aesthetics: The procedure can also enhance the
facial contour, contributing to improved aesthetics for the patient.
Functional Improvement: Patients may experience
improved chewing function and overall quality of life following the
procedure.
Considerations and Risks
Surgical Risks: As with any surgical procedure, there
are risks involved, including infection, bleeding, and complications related
to anesthesia.
Healing Time: Patients should be informed about the
expected healing time and the importance of following postoperative care
instructions.
Follow-Up: Regular follow-up appointments are necessary
to monitor healing and assess the need for any adjustments to dentures.
Stationary Relationship
Dental Anatomy
Stationary Relationship
a) .Centric Relation is the most superior relationship of the condyle of the mandible to the articular fossa of the temporal bone as determined by the bones ligaments. and muscles of the temporomandibular joint; in an ideal dentition it is the same as centric occlusion.
(b) Canines may also be used to confirm the molar relationships to classify occlusion when molars are missing; a class I canine relationship shows the cusp tip of the maxillary canine facial to the mesiobuccal cusp of the first permanent molar
c) Second primary molars are used to classify the occlusion in a primary dentition
(d) In a mixed dentition the first permanent molars will erupt into a normal occlusion if there is a terminal step between the distal surfaces of maxillarv and mandibular second primary molars; if these surfaces are flush, a terminal plane exists and the first permanent molars will first erupt into an end-to-end relationship until there is a shifting of space or exfoliation of the second primary molar
Classification of Fatty Acids and Triglycerides
Biochemistry
Classification of Fatty Acids and Triglycerides
Short-chain: 2-4 carbon atoms
Medium-chain: 6-12 carbon atoms
Long-chain: 14-20 carbon atoms
Very long-chain: >20 carbon atoms
• are usually in esterified form as major components of other lipids
A16-carbon fatty acid, with one cis double bond between carbon atoms 9 and 10 may be represented as 16:1 cisD9.
Double bonds in fatty acids usually have the cis configuration. Most naturally occurring fatty acids have an even number of carbon atoms
Examples of fatty acids
18:0
stearic acid
18:1 cisD9
oleic acid
18:2 cisD9,12
linoleic acid
18:3 cisD9,12,15
linonenic acid
20:4 cisD5,8,11,14
arachidonic acid
There is free rotation about C-C bonds in the fatty acid hydrocarbon, except where there is a double bond. Each cis double bond causes a kink in the chain,
COMPOSITE RESINS - Properties
Dental Materials
Properties-improve with filler content
Physical
Radiopacity depends on ions in silicate glass or the addition of barium sulfate (many systems radiolucent)
Coefficient of thermal expansion is 35 to 45 ppm/C and decreases with increasing filler content
Thermal and electrical insulators
Chemical
Water absorption is 0.5 % to 2.5% and increases with polymer level)
Acidulated topical fluorides (e.g., APF) tend to dissolve glass particles, and thus composites should be protected with petroleum jelly (Vaseline) during those procedures
Color changes occur in resin matrix with time because of oxidation, which produces colored by-products
Mechanical
Compressive strength is 45,000 to 60,000 lb/ in2, which is adequate
Wear resistance-improves with higher filler content, higher percentage of conversion in curing, and use of microfiller, but it is not adequate for some posterior applications
Surfaces rough from wear retain plaque and stain more readily
Biologic
Components may be cytotoxic, but cured composite is biocompatible as restorative filling material
Drugs used in cough.
Pharmacology
PHARYNGEAL DEMULCENTS
Administered in the form of lozenges, cough drops and cough linctus.
Produce soothing action on throat directly and by increasing the flow of saliva and provide symptomatic relief from dry cough.
EXPECTORANT
Expectorants are the drugs which increase the production of bronchial secretion and reduce its viscosity to facilitate its removal by coughing.
ANTITUSSIVES
They are central cough suppressants and act centrally to raise the threshold of cough centre and inhibit the cough reflex by suppressing the coordinating cough centre in the medulla oblongata.
Codeine - it depresses cough centre but is less constipating and abuse liability is low.
Pholcodeine is similar to codeine in efficacy and is longer acting. It has no analgesic or addicting property.
Noscapine is another opium alkaloid of benzylisoquinoline group. It is used as antitussive with no analgesic and drug abuse or drug dependence property.
Dextromethorphan is a synthetic compound and its dextroisomer is used as antitussive and is as effective as codeine
Pipazethate is another synthetic compound of phenothiazine category used as antitussive with little analgesic and sedative properties.
ANTIHISTAMINICS
They do not act on cough centre but provide relief due to their sedative and anticholinergic action.
BRONCHODILATORS
Bronchodilators are helpful in individuals with cough and bronchoconstriction due to bronchial hyperreactivity. They help by improving the effectiveness of cough in clearing secretions.
Direct Pulp Capping
EndodonticsDirect pulp capping is a minimally invasive endodontic procedure used to
preserve the vitality of the tooth's pulp when it is exposed due to caries or
trauma. The goal is to induce a biological response that leads to the formation
of dentin-bridge to seal the pulp and prevent further infection.
Indications:
- Cariously exposed pulp that is asymptomatic and has no evidence of
irreversible pulpitis.
- Recent traumatic exposure of the pulp with no signs of necrosis or infection.
- Presence of a thin layer of residual dentin over the pulp.
Contraindications:
- Signs of irreversible pulpitis or pulpal necrosis.
- Presence of a deep carious lesion that may lead to pulpal exposure during
restoration.
- Large pulp exposures or when the pulp is exposed for an extended period.
- Immunocompromised patients or those with poor oral hygiene.
Procedure:
1. Local anesthesia: Numb the tooth and surrounding tissue to ensure patient
comfort.
2. Caries removal: Carefully remove caries and any infected dentin using a
high-speed handpiece with water spray to prevent pulp exposure.
3. Hemostasis: Apply a mild hemostatic agent if necessary to control bleeding.
4. Pulp conditioning: Apply a calcium hydroxide paste or a bioactive material to
the exposed pulp for a brief period.
5. Application of the capping material: Place a bioactive material, such as
mineral trioxide aggregate (MTA), calcium silicate, or a glass ionomer cement,
directly over the pulp.
6. Restoration: Seal the tooth with a temporary restoration material and place a
final restoration (usually a composite resin) to protect the pulp from further
trauma.
7. Follow-up: Monitor the tooth for signs of pain, swelling, or discoloration.
If these symptoms occur, a root canal treatment may be necessary.
Advantages:
- Preservation of pulp vitality.
- Reduced need for root canal treatment.
- Faster healing and less post-operative sensitivity.
- Conservative approach, maintaining more natural tooth structure.
Disadvantages:
- Limited success in deep or prolonged exposures.
- Higher risk of failure in certain cases, such as extensive caries or pulp
exposure.
- Requires careful technique to avoid further pulp damage.
Bones of the Skull
Anatomy
BONES OF THE CRANIUM
Occipital (1)
Frontal (1)
Sphenoid (1)
Ethmoid (1)
Parietal (2)
Temporal (2)
BONES OF THE FACE
Mandible (1)
Vomer (1)
Maxillae (2)
Zygomae (2)
Lacrimal (2)
Nasal (2)
Inferior nasal conchae (2)
Palatine (2)