NEET MDS Synopsis
CARCINOMA IN SITU
General Pathology
CARCINOMA IN SITU
Epithelial malignancy which has not yet invaded even -the local confines viz basement membrane is termed as carcinoma in situ (intra epithelial neoplasia, pre-invasive cancer)
This lesion merges morphologically with severe dysplasia
Common sites for carcinoma-in-situ :
Cervical squamous epithelium
Oropharynx
Bronchial epithelium.
Breast ducts and lobules.
Skin, in the form of Bowen's disease.
Glans penis and vulva in the form of Erythroplasia of Queyrat
CASTING
Dental Materials
CASTING
Melting & Casting Technique Melting & Casting requires Heat source to melt the alloy Casting force, to drive the alloy into the mould
Casting Torch Selection Two type of torch tips: Multi-orifice Single-orifice Multi-orifice tip is widely used for metal ceramic alloys. Main advantage is distribution of heat over wide area for uniform heating of the alloy. Single-orifice tip concentrate more heat in one area.Three fuel sources are used for Casting Torch; Acetylene ,Natural Gas ,Propane
CASTING CRUCIBLES
Four types are available ;
1) Clay .
2) Carbon .
3) Quartz .
4) Zirconia –Alumina .
Casting Machines
It is a device which uses heat source to melt the alloy casting force .
Heat sources can be :
1) Reducing flame of a torch .( conventional alloys & metal ceramic alloys )
2) Electricity .(Base metal alloys )
Advantages of electric heating :
-heating is evenly controlled .
-minimal undesirable changes in the alloy composition .
- Appropriate for large labs .
Disadvantage :
Expensive .
Casting machines use :
1) Air pressure .
2) Centrifugal force .
3) Evacuation technique .
Alloys can be melted by :
1) Alloy is melted in a separate crucible by a torch flame & is cast into the mold by centrifugal force .(centrifugal C M )
2) Alloy is melted by resistance heating or by induction furnace & then cast centrifugally by motor or spring action (springwound CM electrical resistance )
3) Alloy is melted by induction heating cast into mold centrifugally by motor or spring action .(Induction CM )
4) Alloy is vacum melted by an argon atmosphere
Torch melting / Centrifugal casting machine
Electrical resistance /Heated casting machine
Melting of the alloy should be done in a graphite or ceramic crucible .
Advantage :
-Oxidation of metal ceramic restorations on
overheating is prevented .
-Help in solidification from tip of the casting to the button surface .
Induction casting machine
Commonly used for melting base metal alloys.
Advantage :
- Highly efficient .
- Compact machine withlow power consumption
-No pre heating needed ,
- safe & reliable.
Direct current arc melting machine
A direct current arc is produced between two electrodes :
The alloy & the water cooled tungsten electrode .Temp used is 4000 degrees .
Disadvanage :
High risk of overheating the alloy .
Vacuum or pressure assisted casting machine
Molten alloy is drawn into the evacuated mold by gravity or vacuum & subjected to aditional pressure
For Titanium & its alloys vacuum heated argon pressure casting machines are used .
Accelerated casting method
This method reduces the time of both bench set of the investment & burnout .
Uses phosphate bonded investments which uses 15 mnts for bench set & 15mnts for burnout by placing in a pre – heated furnace to 815 degrees .
Effect of burnout on gypsum bonded investments
Rate of heating has influence on smoothness & on overall dimensions of the investment
Rapid heating causes cracking & flaking which can cause fins or spines .
Avoid heating gypsum bonded investment above 700 degrees .Complete the wax elimination below that temp .
Effect of burnout on phosphate bonded investments
Usual burnout temp is 750 -1030 degrees.
Although they are strong they are brittle too .
Since the entire process takes a long time two stage burnout & plastic ring can be used .
Thalassemia
Medicine
Thalassemia
Thalassemias are a heterogeneous group of hereditary blood disorders characterized by faulty globin chain synthesis resulting in defective hemoglobin, which can lead to anemia
Thalassemia provides partial resistance against malaria.
Beta thalassemia
Clinical features
Minor variant (heterozygous): unremarkable symptoms (low risk of hemolysis, rarely splenomegaly)
Major variant (homozygous) Severe hemolytic anemia, Hepatosplenomegaly ,Growth retardation ,Skeletal deformities (high forehead, prominent zygomatic bones, and maxilla)
Alpha thalassemia
most commonly seen in people of Asian and African descent
Clinical features
Silent carrier: asymptomatic
Alpha thalassemia trait: mild hemolytic anemia with normal RBC and RDW
Hemoglobin H disease
Jaundice and anemia at birth
Chronic hemolytic anemia which may require transfusions
Hb-Bart's hydrops fetalis syndrome (most severe variant of alpha thalassemia)
Intrauterine ascites and hydrops fetalis, severe hepatosplenomegaly, and often cardiac and skeletal anomalies
Incompatible with life (death in utero or shortly after birth)
Diagnostics
Microcytic hypochromic anemia
Blood smear: target cells , teardrop cells
Bone marrow biopsy: reactive hyperplasia
Confirmatory tests
Hb-electrophoresis Alpha thalassemia can usually only be detected if ≥ 3 alleles are defective.
DNA analysis: to test for alpha thalassemia minor and minima (< 3 alleles defective)
Skeletal deformities -high forehead, prominent zygomatic bones and maxilla can be seen on all imaging modalities.
X-ray: hair-on-end (“crew cut”) sign
Liver Diseases
General Pathology
1. Pyogenic liver abscesses may be caused by E. coli, Klebsiella, Streptococcus, Staphylococcus, Bacteroides, Pseudomonas, and fungi.
Parasitic infections
1. Schistosomiasis is caused by different organisms in different parts of the world.
a. Clinical features include splenomegaly, portal hypertension, and ascites. Lesions are caused by the immune response to ova.
2. Amebiasis is caused by Entamoeba histolytica.
a. Clinical features include bloody diarrhea, pain, fever, jaundice, and hepatomegaly.
Drug-induced liver damage may be caused by agents that are direct hepatotoxins, such as carbon tetrachloride, acetaminophen, methotrexate, anabolic steroids, and oral contraceptive pills.
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).
Ichthyosis vulgaris
General Pathology
Ichthyosis vulgaris is a genetic disease characterized by increased cohesiveness of the cells in the stratum corneum, resulting up in a piling up stratum corneum (scales like a fish).
OCCLUSION AND DENTAL DEVELOPMENT-Stages-Deciduous dentition period
Dental Anatomy
Deciduous dentition period.
-The deciduous teeth start to erupt at the age of six months and the deciduous dentition is complete by the age of approximately two and one half years of age.
-The jaws continue to increase in size at all points until about age one year.
-After this, growth of the arches is lengthening of the arches at their posterior (distal) ends. Also, there is slightly more forward growth of the mandible than the maxilla.
1. Many early developmental events take place.
-The tooth buds anticipate the ultimate occlusal pattern.
-Mandibular teeth tend to erupt first. The pattern for the deciduous incisors is usually in this distinctive order:
(1) mandibular central
(2) maxillary central incisors
(3) then all four lateral incisors.
-By one year, the deciduous molars begin to erupt.
-The eruption pattern for the deciduous dentition as a whole is:
(1) central incisor
(2) lateral incisor
(3) deciduous first molar
(4) then the canine
(5) then finally the second molar.
-Eruption times can be variable.
2. Occlusal changes in the deciduous dentition.
-The overjet tends to diminish with age. Wear and mandibular growth are a factor in this process.
-The overbite often diminishes with the teeth being worn to a flat plane occlusion.
-Spacing of the incisors in anticipation of the soon-to-erupt permanent incisors appears late. Permanent anterior teeth (incisors and canines) are wider mesiodistally than deciduous anterior teeth. In contrast, the deciduous molar are wider mesiodistally that the premolars that later replace them.
-Primate spaces occur in about 50% of children. They appear in the deciduous dentition. The spaces appear between the upper lateral incisor and the upper canine. They also appear between the lower canine and the deciduous first molar.
Management of H. Pylori Infection and ZE Syndrome
Pharmacology
Management of H. Pylori Infection
- Gram – rod
- Causes erosion of protective epithelial cells -> gastritis or peptic ulcer
H2 antagonist or PPI + Abx
- Metronidazole or amoxicillin/clarithromycin
- PPI + 2 or 3 antimicrobials is standard
- Ex: Ranitidine + Peptobismol + Clarithromycin + Amoxicillin 7-14 days
-Add bismuth if resistant H. pylori
- Ex: PPI + BMT (Bismuth + Metronidazole + tetracycline) 7days
Treatment for ZE Syndrome
- Gastrinoma of the duodenum or pancreas
-Elevated gastrin levels- Peptic/gastric ulcers
- Treatment
High dose PPI until resorting to surgery or chemotherapy for tumor removal