NEET MDS Synopsis
Dentinogenesis
Dental Anatomy
Dentinogenesis
Dentin formation, known as dentinogenesis, is the first identifiable feature in the crown stage of tooth development. The formation of dentin must always occur before the formation of enamel. The different stages of dentin formation result in different types of dentin: mantle dentin, primary dentin, secondary dentin, and tertiary dentin.
Odontoblasts, the dentin-forming cells, differentiate from cells of the dental papilla. They begin secreting an organic matrix around the area directly adjacent to the inner enamel epithelium, closest to the area of the future cusp of a tooth. The organic matrix contains collagen fibers with large diameters (0.1-0.2 μm in diameter). The odontoblasts begin to move toward the center of the tooth, forming an extension called the odontoblast process. Thus, dentin formation proceeds toward the inside of the tooth. The odontoblast process causes the secretion of hydroxyapatite crystals and mineralization of the matrix. This area of mineralization is known as mantle dentin and is a layer usually about 150 μm thick.
Whereas mantle dentin forms from the preexisting ground substance of the dental papilla, primary dentin forms through a different process. Odontoblasts increase in size, eliminating the availability of any extracellular resources to contribute to an organic matrix for mineralization. Additionally, the larger odontoblasts cause collagen to be secreted in smaller amounts, which results in more tightly arranged, heterogenous nucleation that is used for mineralization. Other materials (such as lipids, phosphoproteins, and phospholipids) are also secreted.
Secondary dentin is formed after root formation is finished and occurs at a much slower rate. It is not formed at a uniform rate along the tooth, but instead forms faster along sections closer to the crown of a tooth. This development continues throughout life and accounts for the smaller areas of pulp found in older individuals. Tertiary dentin, also known as reparative dentin, forms in reaction to stimuli, such as attrition or dental caries.
The dentin in the root of a tooth forms only after the presence of Hertwig's epithelial root sheath (HERS), near the cervical loop of the enamel organ. Root dentin is considered different than dentin found in the crown of the tooth (known as coronal dentin) because of the different orientation of collagen fibers, the decrease of phosphoryn levels, and the less amount of mineralization.
Chronic myelocytic leukaemia
General Pathology
Chronic myelocytic leukaemia
Commoner in adults (except the Juvenile type)
Features:
- Anaemia.
- Massive splenomegaly
- Bleeding tendencies.
- Sternal tenderness.
- Gout and skin manifestations
Blood picture:
- Marked leucocytosis of 50,-1000,000 cu.mm, often more
- Immature cells of the series with 20-50 % myelocytes
- Blasts form upto 5-10% of cells
- Basophils may be increased
- Leuocyte alkaline phosphate is reduced
- Anaemia with reticutosis and nucleated RBC
- Platelets initially high levels may fall later if patient goes into blast crisis.
Bone marrow:
- Hyper cellular marrow.
- Myeloid hyperplasia with more of immature forms, persominatly myelocytes.
Chromosomal finding. Philadelphia (Phi) chromosome is positive adult cases .It is a short chromosome due to deletion of long arm of chromosome 22 (translocated to no.9),
Juvenile type :- This is Ph1 negative has more nodal enlargement and has a worse prognosis, with a greater proneness to infections and haemorrhage
Surface Defence Mechanisms
General Pathology
Surface Defence Mechanisms
1. Skin:
(i) Mechanical barrier of keratin and desquamation.
(ii) Resident commensal organisms
(iii)Acidity of sweat.
(iv) Unsaturated fatty acids of sebum
2. Oropharyngeal
(i)Resident flora
(ii) Saliva, rich in lysozyme, mucin and Immunoglobulins (lgA).
3. Gastrointestinal tract.-
(i) Gastric HCI
(ii) Commensal organisms in Intestine
(iii) Bile salts
(iv) IgA.
(v) Diarrhoeal expulsion of irritants.
4. Respiratory tract:
(i) Trapping in turbinates
(ii) Mucus trapping
(iii) Expulsion by coughing and sneezing.
(iv) Ciliary propulsion.
(V) Lysozymes and antibodies in secretion.
(vi) Phagocytosis by alveolar macrophages.
5. Urinary tract:
(i) Flushing action.
(ii) Acidity
(iii) Phagocytosis by urothelial cells.
6. Vagina.-
(i) Desquamation.
(ii) Acid barrier.
(iii) Doderlein's bacilli (Lactobacilli)
7. Conjunctiva:
Lysozymes and IgA in tears
The Body Regulates pH in Several Ways
PhysiologyThe Body Regulates pH in Several Ways
Buffers are weak acid mixtures (such as bicarbonate/CO2) which minimize pH change
Buffer is always a mixture of 2 compounds
One compound takes up H ions if there are too many (H acceptor)
The second compound releases H ions if there are not enough (H donor)
The strength of a buffer is given by the buffer capacity
Buffer capacity is proportional to the buffer concentration and to a parameter known as the pK
Mouth bacteria produce acids which attack teeth, producing caries (cavities). People with low buffer capacities in their saliva have more caries than those with high buffer capacities.
CO2 gas (a potential acid) is eliminated by the lungs
Other acids and bases are eliminated by the kidneys
Valproic acid
Pharmacology
Valproic acid: broad spectrum (for most seizure types)
Mechanism: blocks Ca T currents in thalamic neurons (prevents reverberating activity in absence seizures), ↓ reactivation of Na channels (in tonic/clonic seizures; prolongs refractory periods of neurons, prevents high frequency cell firing)
Side effects: very low toxicity; common = anorexia, N/V; at high doses inhibits platelet function (bruising and gingival bleeding); rarely see idiosyncratic hepatotoxicity
Drug interactions: induces hepatic microsomal enzymes (↓ effectiveness of other drugs), binds tightly to plasma proteins so displaces other drugs
Polycystic kidney disease
General Pathology
Polycystic kidney disease
Characterized by the formation of cysts and partial replacement of renal parenchyma.
Genetic transmission: autosomal dominant.
Clinical manifestations:
hypertension, hematuria, palpable renal masses, and progression to renal failure. Commonly associated with berry
aneurysms.
Hypnosis
PedodonticsHypnosis in Pediatric Dentistry
Hypnosis: An altered state of consciousness
characterized by heightened suggestibility, focused attention, and increased
responsiveness to suggestions. It is often used to facilitate behavioral and
physiological changes that are beneficial for therapeutic purposes.
Use in Pediatrics: According to Romanson (1981),
hypnosis is recognized as one of the most effective nonpharmacologic
therapies for children, particularly in managing anxiety and enhancing
cooperation during medical and dental procedures.
Dental Application: In the field of dentistry, hypnosis
is referred to as "hypnodontics" (Richardson, 1980) and is also known as
psychosomatic therapy or suggestion therapy.
Benefits of Hypnosis in Dentistry
Anxiety Reduction:
Hypnosis can significantly alleviate anxiety in children, making
dental visits less stressful. This is particularly important for
children who may have dental phobias or anxiety about procedures.
Pain Management:
One of the primary advantages of hypnosis is its ability to reduce
the perception of pain. By using focused attention and positive
suggestions, dental professionals can help minimize discomfort during
procedures.
Behavioral Modification:
Hypnosis can encourage positive behaviors in children, such as
cooperation during treatment, which can reduce the need for sedation or
physical restraint.
Enhanced Relaxation:
The hypnotic state promotes deep relaxation, helping children feel
more at ease in the dental environment.
Mechanism of Action
Suggestibility: During hypnosis, children become more
open to suggestions, allowing the dentist to guide their thoughts and
feelings about the dental procedure.
Focused Attention: The child’s attention is directed
away from the dental procedure and towards calming imagery or positive
thoughts, which helps reduce anxiety and discomfort.
Implementation in Pediatric Dentistry
Preparation:
Prior to the procedure, the dentist should explain the process of
hypnosis to both the child and their parents, addressing any concerns
and ensuring understanding.
Induction:
The dentist may use various techniques to induce a hypnotic state,
such as guided imagery, progressive relaxation, or verbal suggestions.
Suggestion Phase:
Once the child is in a relaxed state, the dentist can provide
positive suggestions related to the procedure, such as feeling calm,
relaxed, and pain-free.
Post-Hypnosis:
After the procedure, the dentist should gradually bring the child
out of the hypnotic state, reinforcing positive feelings and
experiences.
Hormones of the Hypothalamus
Physiology
The hypothalamus is a region of the brain. It secretes a number of hormones.
Thyrotropin-releasing hormone (TRH)
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)
Corticotropin-releasing hormone (CRH)
Somatostatin
Dopamine
All of these are released into the blood, travel immediately to the anterior lobe of the pituitary, where they exert their effects.
Two other hypothalamic hormones:
Antidiuretic hormone (ADH) and
Oxytocin
travel in neurons to the posterior lobe of the pituitary where they are released into the circulation.