NEET MDS Synopsis
Conditioning and Behavioral Responses
PedodonticsConditioning and Behavioral Responses
This section outlines key concepts related to conditioning and behavioral
responses, particularly in the context of learning and emotional responses in
children.
1. Acquisition
Acquisition refers to the process of
learning a new response to a stimulus through conditioning. This is the
initial stage where an association is formed between a conditioned stimulus
(CS) and an unconditioned stimulus (US).
Example: A child learns to associate the sound of a
bell (CS) with receiving a treat (US), leading to a conditioned response
(CR) of excitement when the bell rings.
2. Generalization
Generalization occurs when the conditioned
response is evoked by stimuli that are similar to the original conditioned
stimulus. This means that the learned response can be triggered by a range
of similar stimuli.
Example: If a child has a painful experience with a
doctor in a white coat, they may generalize this fear to all doctors in
white coats, regardless of the specific individual or setting. Thus, any
doctor wearing a white coat may elicit a fear response.
3. Extinction
Extinction is the process by which the
conditioned behavior diminishes or disappears when the association between
the conditioned stimulus and the unconditioned stimulus is no longer
reinforced.
Example: In the previous example, if the child visits
the doctor multiple times without any unpleasant experiences, the fear
associated with the doctor in a white coat may gradually extinguish. The
lack of reinforcement (pain) leads to a decrease in the conditioned response
(fear).
4. Discrimination
Discrimination is the ability to
differentiate between similar stimuli and respond only to the specific
conditioned stimulus. It is the opposite of generalization.
Example: If the child is exposed to clinic settings
that are different from those associated with painful experiences, they
learn to discriminate between the two environments. For instance, if the
child visits a friendly clinic with a different atmosphere, they may no
longer associate all clinic visits with fear, leading to the extinction of
the generalized fear response.
Excision of Lesions Involving the Jaw Bone
General SurgeryExcision of Lesions Involving the Jaw Bone
When excising lesions involving the jaw bone, various terminologies are used
to describe the specific techniques and outcomes of the procedures.
1. Enucleation
Enucleation refers to the separation of a
lesion from the bone while preserving bone continuity. This is achieved by
removing the lesion along an apparent tissue or cleavage plane, which is
often defined by an encapsulating or circumscribing connective tissue
envelope derived from the lesion or surrounding bone.
Key Characteristics:
The lesion is contained within a defined envelope.
Bone continuity is maintained post-excision.
2. Curettage
Curettage involves the removal of a lesion
from the bone by scraping, particularly when the lesion is friable or lacks
an intact encapsulating tissue envelope. This technique may result in the
removal of some surrounding bone.
Key Characteristics:
Indicates the inability to separate the lesion along a distinct
tissue plane.
May involve an inexact or immeasurable thickness of surrounding
bone.
If a measurable margin of bone is removed, it is termed "resection
without continuity defect."
3. Marsupialization
Marsupialization is a surgical procedure
that involves the exteriorization of a lesion by removing overlying tissue
to expose its internal surface. This is done by excising a portion of the
lesion bordering the oral cavity or another body cavity.
Key Characteristics:
Multicompartmented lesions are rendered unicompartmental.
The lesion is clinically cystic, and the excised tissue may include
bone and/or overlying mucosa.
4. Resection Without Continuity Defect
This term describes the excision of a
lesion along with a measurable perimeter of investing bone, without
interrupting bone continuity. The anatomical relationship allows for the
removal of the lesion while preserving the integrity of the bone.
Key Characteristics:
Bone continuity is maintained.
Adjacent soft tissue may be included in the resection.
5. Resection With Continuity Defect
This involves the excision of a lesion that
results in a defect in the continuity of the bone. This is often associated
with more extensive resections.
Key Characteristics:
Bone continuity is interrupted.
May require reconstruction or other interventions to restore
function.
6. Disarticulation
Disarticulation is a special form of
resection that involves the temporomandibular joint (TMJ) and results in a
continuity defect.
Key Characteristics:
Involves the removal of the joint and associated structures.
Results in loss of continuity in the jaw structure.
7. Recontouring
Recontouring refers to the surgical
reduction of the size and/or shape of the surface of a bony lesion or bone
part. The goal is to reshape the bone to conform to the adjacent normal bone
surface or to achieve an aesthetic result.
Key Characteristics:
May involve lesions such as bone hyperplasia, torus, or exostosis.
Can be performed with or without complete eradication of the lesion
(e.g., fibrous dysplasia).
The Sprue
Dental Materials
The Sprue :
Its a channel through which molten alloy can reach the mold in an invested ring after the wax has been eliminated. Role of a Sprue: Create a channel to allow the molten wax to escape from the mold. Enable the molten alloy to flow into the mold which was previously occupied by the wax pattern.
FUNCTIONS OF SPRUE
1 . Forms a mount for the wax pattern .
2 . Creates a channel for elimination of wax .
3 .Forms a channel for entry of molten metal
4 . Provides a reservoir of molten metal to compensate for the alloy shrinkage .
SELECTION OF SPRUE
Sprue former gauge selection is often empirical, is yet based on the following five general principles:
1. Select the gauge sprue former with a diameter that is approximately the same size as the thickest area of the wax pattern. If the pattern is small, the sprue former must also be small because a large sprue former attached to a thin delicate pattern could cause distortion. However if the sprue former diameter is too small this area will solidify before the casting itself and localized shrinkage porosity may result.
2. If possible the sprue former should be attached to the portion of the pattern with the largest cross-sectional area. It is best for the molten alloy to flow from the thick section to the surrounding thin areas. This design minimizes the risk of turbulence.
3. The length of the sprue former should be long enough to properly position the pattern in the casting ring within 6mm of the trailing end and yet short enough so the molten alloy does not solidify before it fills the mold.
4. The type of sprue former selected influences the burnout technique used. It is advisable to use a two-stage burnout technique whenever plastic sprue formers or patterns are involved to ensure complete carbon elimination, because plastic sprues soften at temperatures above the melting point of the inlay waxes.
5. Patterns may be sprued directly or indirectly. For direct sprueing the sprue former provides the direct connection between the pattern area and the sprue base or crucible former area. With indirect spruing a connector or reservoir bar is positioned between the pattern and the crucible former. It is common to use indirect spruing for multiple stage units and fixed partial dentures.
Formation and Eruption of Deciduous Teeth.
Dental Anatomy
Formation and Eruption of Deciduous Teeth.
-Calcification begins during the fourth month of fetal life. By the end of the sixth month, all of the deciduous teeth have begun calcification.
-By the time the deciduous teeth have fully erupted (two to two and one half years of age), cacification of the crowns of permanent teeth is under way. First permanent molars have begun cacification at the time of birth. -Here are some things to know about eruption patterns:
(1) Teeth tend to erupt in pairs.
(2) Usually, lower deciduous teeth erupt first. Congenitally missing deciduous teeth is infrequent. Usually, the lower deciduous central incisors are thefirst to erupt thus initiating the deciduous dentition. The appearance of the deciduous second molars completes the deciduous dentition by 2 to 2 1/2 years of age.
- Deciduous teeth shed earlier and permanent teeth erupt earlier in girls.
- The orderly pattern of eruption and their orderly replacement by permanent teeth is important.
- order for eruption of the deciduous teeth is as follows:
(1) Central incisor.........Lower 6 ½ months, Upper 7 ½ months
(2) Lateral incisor.........Lower 7 months, Upper 8 months
(3) First deciduous molar...Lower 12-16 months, Upper 12-16 months
(4) Deciduous canine........Lower 16-20 months, Upper 16-20 months
(5) Second deciduous molar..Lower 20-30 months, Upper 20-30 months
Megaloblastic anaemia
General Pathology
Megaloblastic anaemia
Metabolism: B12(cyanocobalamin) is a coenzyme in DNA synthesis and for maintenance of nervous system. Daily requirement 2 micro grams. Absorption in terminal ileum in the presence gastric intrinsic factor. It is stored in liver mainly-
Folic acid (Pteroylglutamic acid) is needed for DNA synthesis.. Daily requirement 100 micro grams. Absorption in duodenum and jejunum
Causes of deficiency .-
- Nutritional deficiency-
- Malabsorption syndrome.
- Pernicious anaemia (B12).
- Gastrectomy (B12).
- Fish tapeworm infestation (B12).
- Pregnancy and puerperium (Folic acid mainly).
- Myeloproliferative disorders (Folic acid).
- Malignancies (Folic acid).
- Drug induced (Folic-acid)
Features:
(i) Megaloblastic anaemia.
(ii) Glossitis.
(iii) Subacute combined degeneration (in B12deficiency).
Blood picture :
- Macrocytic normochromic anaemia.
- Anisocytosis and poikilocytosis with Howell-Jolly bodies and basophilic stippling.
- Occasional megalo blasts may be-seen.
- Neutropenia with hypersegmented neutrophills and macropolycytes.
- Thrombocytopenia.
- Increased MVC and MCH with normal or decreased MCHC.
Bone marrow:
- Megaloblasts are seen. They are larger with a more open stippled chromatin. The nuclear maturation lags behind. the cytoplasmic maturation. Maturation arrest is seen (more of early forms).
- Immature cells of granulocyte series are also larger.
-Giant stab forms (giant metamyelocytes).
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
Heart sounds
Physiology
Heart sounds
Heart sounds are a result of beating heart and resultant blood flow . that could be detected by a stethoscope during auscultation . Auscultation is a part of physical examination that doctors have to practice them perfectly.
Before discussion the origin and nature of the heart sounds we have to distinguish between the heart sounds and hurt murmurs. Heart murmurs are pathological noises that results from abnormal blood flow in the heart or blood vessels.
Physiologically , blood flow has a laminar pattern , which means that blood flows in form of layers , where the central layer is the most rapid . Laminar blood flow could be turned into turbulent one .
Turbulent blood flow is a result of stenotic ( narrowed ) valves or blood vessels , insufficient valves , roughened vessels` wall or endocardium , and many diseases . The turbulent blood flow causes noisy murmurs inside or outside the heart.
Heart sounds ( especially first and second sounds ) are mainly a result of closure of the valves of the heart . While the third sound is a result of vibration of ventricular wall and the leaflets of the opened AV valves after rapid inflow of blood from the atria to ventricles .
Third heart sound is physiologic in children but pathological in adults.
The four heart sound is a result of the atrial systole and vibration of the AV valves , due to blood rush during atrial systole . It is inaudible neither in adults nor in children . It is just detectable by the phonocardiogram .
Characteristic of heart sounds :
1. First heart sound (S1 , lub ) : a soft and low pitch sound, caused by closure of AV valves.Usually has two components ( M1( mitral ) and T1 ( tricuspid ). Normally M1 preceads T1.
2. Second heart sound ( S2 , dub) : sharp and high pitch sound . caused by closure of semilunar valves. It also has two components A2 ( aortic) and P2 ( pulmonary) . A2 preceads P2.
3. Third heart sound (S3) : low pitched sound.
4. Fourth heart sound ( S4) very low pitched sound.
As we notice : the first three sounds are related to ventricular activity , while the fourth heart sound is related to atrial activity.
Closure of valves is not the direct cause for heart sounds , but sharp blocking of blood of backward returning of blood by the closing valve is the direct cause.
Clinical significance PTH secretion
Biochemistry
Clinical significance
Primary hyperparathyroidism is due to autonomous, abnormal hypersecretion of PTH in the parathyroid gland
Secondary hyperparathyroidism is an appropriately high PTH level seen as a physiological response to hypocalcemia.
A low level of PTH in the blood is known as hypoparathyroidism and is most commonly due to damage to or removal of parathyroid glands during thyroid surgery.