NEET MDS Synopsis
Bile
PhysiologyBile contains:
bile acids. These amphiphilic steroids emulsify ingested fat. The hydrophobic portion of the steroid dissolves in the fat while the negatively-charged side chain interacts with water molecules. The mutual repulsion of these negatively-charged droplets keeps them from coalescing. Thus large globules of fat (liquid at body temperature) are emulsified into tiny droplets (about 1 µm in diameter) that can be more easily digested and absorbed.
bile pigments. These are the products of the breakdown of hemoglobin removed by the liver from old red blood cells. The brownish color of the bile pigments imparts the characteristic brown color of the feces.
Biomechanics of complete edentulous state
Prosthodontics
The clinical implications of an edentulous stomatognathic system are considered under the following factors:
(1) modi?cations in areas of support .
(2) functional and parafunctional considerations.
(3) changes in morphologic face height, and temporomandibular joint (TMJ).
(4) cosmetic changes and adaptive responses
Support mechanism for complete dentures
Mucosal support and masticatory loads
- The area of mucosa available to receive the load from complete dentures is limited when compared with the corresponding areas of support available for natural dentitions.
- The mean denture bearing area to be 22.96 cm2 in the edentulous maxillae and approximately 12.25 cm2 in an edentulous mandible
- In fact, any disturbance of the normal metabolic processes may lower the upper limit of mucosal tolerance and initiate in?ammation
Residual ridge
The residual ridge consists of denture-bearing mucosa, the submucosa and periosteum, and the underlying residual alveolar bone.
The alveolar bone supporting natural teeth receives tensile loads through a large area of periodontal ligament, whereas the edentulous residual ridge receives vertical, diagonal, and horizontal loads applied by a denture with a surface area much smaller than the total area of the periodontal ligaments of all the natural teeth that had been present.
There are two physical factors involved in denture retention that are under the control of the dentist
- The maximal extension of the denture base
- maximal intimate contact of the denture base and its basal seat
- The buccinator, the orbicularis oris, and the intrinsic and extrinsic muscles of the tongue are the key muscles that the dentist harnesses to achieve this objective by means of impression techniques.
- The design of the labial buccal and lingual polished surface of the denture and the form of the dental arch are considered in balancing the forces generated by the tongue and perioral musculature.
Function: mastication and other mandibular movements
Mastication consists of a rhythmic separation and apposition of the jaws and involves biophysical and biochemical processes, including the use of the lips, teeth, cheeks, tongue, palate, and all the oral structures to prepare food for swallowing.
- The maximal bite force in denture wearers is ?ve to six times less than that in dentulous individuals.
- The pronounced differences between persons with natural teeth and patients with complete dentures are conspicuous in this functional context:
(1) the mucosal mechanism of support as opposed to support by the periodontium ;
(2) the movements of the dentures during mastication;
(3) the progressive changes in maxillomandibular relations and the eventual migration of dentures
(4) the different physical stimuli to the sensor motor systems.
Parafunctional considerations
- Parafunctional habits involving repeated or sustained occlusion of the teeth can be harmful to the teeth or other components of the masticatory system.
- Teeth clenching is common and is a frequent cause of the complaint of soreness of the denture-bearing mucosa.
- In the denture wearer, parafunctional habits can cause additional loading on the denture-bearing tissues
Force generated during mastication and parafunction
Functional (Mastication)
Direction -> Mainly vertical
Duration and magnitude -> Intermittent and light diurnal only
Parafunction
Direction -> Frequently horizontalas well as vertical
Duration and magnitude -> Prolonged, possibly excessive Both diurnal and nocturnal
Changes in morphology (face height), occlusion, and the TMJs
The reduction of the residual ridges under complete dentures and the accompanying reduction in vertical dimension of occlusion tend to cause a reduction in the total face height and a resultant mandibular prognathism.
In complete denture wearers, the mean reduction in height of the mandibular residual alveolar ridge measured in the anterior region may be approximately four times greater than the mean reduction occurring in the maxillary residual alveolar process
Occlusion
- In complete denture prosthodontics, the position of planned maximum intercuspation of teeth is established to coincide with the patient’s centric relation.
-The coincidence of centric relation and centric occlusion is consequently referred to as centric relation occlusion (CRG).
- Centric relation at the established vertical dimension has potential for change. This change is brought about by alterations indenture-supporting tissues and facial height, as well as by morphological changes in the TMJs.
TMJ changes
impaired dental ef?ciency resulting from partial tooth loss and absence of or incorrect prosthodontic treatment can in?uence the outcome of temporomandibular disorders.
Aesthetic, behavioral, and adaptive response
Aesthetic changes associated with the edentulous state.
- Deepening of nasolabial groove
- Loss of labiodentals angle
- Narrowing of lips
- Increase in columellae philtral angle
- Prognathic appearance
Cryosurgery
Oral and Maxillofacial SurgeryCryosurgery
Cryosurgery is a medical technique that utilizes extreme
rapid cooling to freeze and destroy tissues. This method is particularly
effective for treating various conditions, including malignancies, vascular
tumors, and aggressive tumors such as ameloblastoma. The process involves
applying very low temperatures to induce localized tissue destruction while
minimizing damage to surrounding healthy tissues.
Mechanism of Action
The effects of rapid freezing on tissues include:
Reduction of Intracellular Water:
Rapid cooling causes water within the cells to freeze, leading to a
decrease in intracellular water content.
Cellular and Cell Membrane Shrinkage:
The freezing process results in the shrinkage of cells and their
membranes, contributing to cellular damage.
Increased Concentrations of Intracellular Solutes:
As water is removed from the cells, the concentration of solutes
(such as proteins and electrolytes) increases, which can disrupt
cellular function.
Formation of Ice Crystals:
Both intracellular and extracellular ice crystals form during the
freezing process. The formation of these crystals can puncture cell
membranes and disrupt cellular integrity, leading to cell death.
Cryosurgery Apparatus
The equipment used in cryosurgery typically includes:
Storage Bottles for Pressurized Liquid Gases:
Liquid Nitrogen: Provides extremely low
temperatures of approximately -196°C, making it highly
effective for cryosurgery.
Liquid Carbon Dioxide or Nitrous Oxide: These gases
provide temperatures ranging from -20°C to -90°C, which
can also be used for various applications.
Pressure and Temperature Gauge:
This gauge is essential for monitoring the pressure and temperature
of the cryogenic gases to ensure safe and effective application.
Probe with Tubing:
A specialized probe is used to direct the pressurized gas to the
targeted tissues, allowing for precise application of the freezing
effect.
Treatment Parameters
Time and Temperature: The specific time and temperature
used during cryosurgery depend on the depth and extent of the tumor being
treated. The clinician must carefully assess these factors to achieve
optimal results while minimizing damage to surrounding healthy tissues.
Applications
Cryosurgery is applied in the treatment of various conditions, including:
Malignancies: Used to destroy cancerous tissues in
various organs.
Vascular Tumors: Effective in treating tumors that have
a significant blood supply.
Aggressive Tumors: Such as ameloblastoma, where rapid
and effective tissue destruction is necessary.
Model. Cast. and Die Materials
Dental Materials
Model. Cast. and Die Materials
Applications
- Gold casting, porcelain and porcelain-fused–to metal fabrication procedures
- Orthodontic and pedodontic appliance construction
- Study models for occlusal records
Terms
a. Models-replicas of hard and soft tissues for study of dental symmetry
b. Casts-working replicas of hard and soft tissues for use in the fabrication of appliances or restorations
c. Dies :- working replicas of one tooth (or a few teeth) used for the fabrication of a restoration
d. Duplicates-second casts prepared from original casts
Classification by materials
a Models :- (model plaster or orthodontic stone; gypsum product)
b. Stone casts (regular stone; gypsum product)
c. Stone dies (diestone; gypsum product)-may electroplated
d. Epoxy dies (epoxy polymer)-abrasion-resistant dies
Respiratory Viral Diseases
General Pathology
Respiratory Viral Diseases
Respiratory viral infections cause acute local and systemic illnesses. The common cold, influenza, pharyngitis, laryngitis (including croup), and tracheobronchitis are common.
An acute, usually afebrile, viral infection of the respiratory tract, with inflammation in any or all airways, including the nose, paranasal sinuses, throat, larynx, and sometimes the trachea and bronchi.
Etiology and Epidemiology
Picornaviruses, especially rhinoviruses and certain echoviruses and coxsackieviruses, cause the common cold. About 30 to 50% of all colds are caused by one of the > 100 serotypes of rhinoviruses.
Symptoms and Signs
Clinical symptoms and signs are nonspecific.
After an incubation period of 24 to 72 h, onset is abrupt, with a burning sensation in the nose or throat, followed by sneezing, rhinorrhea, and malaise.
Characteristically, fever is not present, particularly with a rhinovirus or coronavirus. Pharyngitis usually develops early; laryngitis and tracheobronchitis vary by person and causative agent. Nasal secretions are watery and profuse during the first days, but become more mucoid and purulent.
Cough is usually mild but often lasts into the 2nd wk.
The Middle Ear
AnatomyThe Middle Ear
This part of the ear is in a narrow cavity in the petrous part of the temporal bone.
It contains air, three auditory ossicles, a nerve and two small muscles.
The middle ear is separated from the external acoustic meatus by the tympanic membrane.
This cavity includes the tympanic cavity proper, the space directly internal to the tympanic membrane, and the epitympanic recess, the space superior to it.
The middle ear is connected anteriorly with the nasopharynx by the auditory tube.
Posterosuperiorly, the tympanic cavity connects with the mastoid cells through the aditus ad antrum (mastoid antrum).
The tympanic cavity is lined with mucous membrane that is continuous with the mucous membrane of the auditory tube, mastoid cells, and aditus ad antrum.
Contents of the Tympanic Cavity or Middle Ear
This cavity contains the auditory ossicles (malleus, incus and stapes); the stapedius and tensor tympani muscles; the chorda tympani nerve (a branch of the facial nerve, CN VII); and the tympanic plexus of nerves.
HISTOLOGY OF THE ODONTOBLAST
Dental Anatomy
HISTOLOGY OF THE ODONTOBLAST
Formation of Dentin
Mantle dentin: First formed dentin
Type I collagen with ground substance
Formation of the odontoblast process
Matrix vesicles
Appearance of hydroxyapatite crystals
Predentin
Primary physiologic (circumpulpal) dentin
All organic matrix is formed from odontoblasts
Smaller collagen fibers
Presence of phosphophoryn
Mineralization
Globular calcification
Interglobular dentin: Areas of incomplete calcification
Incremental lines of von Ebner: Daily, 4mm of organic matrix is deposited. Also every 5 days the arrangement of collagen fibers changes. This creates the incremental lines of von Ebner.
Intratubular dentin
Dentin tubules
S-shaped in the coronal aspect, straight in root dentin
Von Korff fibers
They are an artifact
Caridex System
Conservative DentistryCaridex SystemCaridex is a dental system designed for the treatment of root canals,
utilizing the non-specific proteolytic effects of sodium hypochlorite (NaOCl) to
aid in the cleaning and disinfection of the root canal system. Below is an
overview of its components, mechanism of action, advantages, and drawbacks.
1. Components of Caridex
A. Caridex Solution I
Composition:
0.1 M Butyric Acid
0.1 M Sodium Hypochlorite (NaOCl)
0.1 M Sodium Hydroxide (NaOH)
B. Caridex Solution II
Composition:
1% Sodium Hypochlorite in a weak alkaline solution.
C. Delivery System
Components:
NaOCl Pump: Delivers the sodium hypochlorite
solution.
Heater: Maintains the temperature of the solution
for optimal efficacy.
Solution Reservoir: Holds the prepared solutions.
Handpiece: Designed to hold the applicator tip for
precise application.
2. Mechanism of Action
Proteolytic Effect: The primary mechanism of action of
Caridex is based on the non-specific proteolytic effect of sodium
hypochlorite.
Chlorination of Collagen: The
N-monochloro-dl-2-aminobutyric acid (NMAB) component enhances the
chlorination of degraded collagen in dentin.
Conversion of Hydroxyproline: The hydroxyproline
present in collagen is converted to pyrrole-2-carboxylic acid, which is part
of the degradation process of dentin collagen.
3. pH and Application Time
Resultant pH: The pH of the Caridex solution is
approximately 12, which is alkaline and conducive to the disinfection
process.
Application Time: The recommended application time for
Caridex is 20 minutes, allowing sufficient time for the
solution to act on the root canal system.
4. Advantages
Effective Disinfection: The use of sodium hypochlorite
provides a strong antimicrobial effect, helping to eliminate bacteria and
debris from the root canal.
Collagen Degradation: The system's ability to degrade
collagen can aid in the removal of organic material from the canal.
5. Drawbacks
Low Efficiency: The overall effectiveness of the
Caridex system may be limited compared to other modern endodontic cleaning
solutions.
Short Shelf Life: The components may have a limited
shelf life, affecting their usability over time.
Time and Volume: The system requires a significant
volume of solution and a longer application time, which may not be practical
in all clinical settings.