Showing posts from March, 2021


  CONFIGURATION FACTOR ( C- FACTOR)  IN COMPOSITE  It is a three dimensional configuration of a prepared cavity. c - factor was introduced by feilzer in the year 1987 Configuration factor is calculated by the number of bonded surface to unbounded surface . composite resin undergo  polymerisation shrinkage : polymerisation shrinkage is a process that occurs when resin gets cured. stress generation along bonded area as they are bonded  micro mechanically free surface - free flow of composite thereby decreasing stress.   NOTE: REFER THE ABOVE IMAGE - In order to get a better understanding on bounded and unbounded surface in a prepared. cavity  REASONS FOR POLYMERISATION SHRINKAGE When composite resin gets cured ,during  the polymerisation process since monomeric particles are more voluminous than polymer ,moneric chains gets unbounded vanderwal force of interaction gets converted to covalent bond. matrix generally shrink from cavity wall,material cure towards the centre of bulk pulls mate

Rheological material characterisation in dentistry

 RHEOLOGY Rheology is the study of deformation and flow characteristic of matter. Importance of Rheology in dentistry : In dentistry we are subjected to manipulate material which flow or deform when subject to stress. Classification of fluid based on rheology: Newtonian Pseudoplastic Dilatant plastic 1) Newtonin : Newtonian fluid have a constant viscosity they,have ideal fluid shear stress proportional  to strain rate . For example- water and newly mixed zinc phosphate cement. 2) Pseudoplastic: Pseudoplastic fluid is a shear thinning  fluid Viscosity decreases ,shear rate increases until it reaches constant value. For example: polycarboxylate cement ,elastomeric impression material. 3) Dilatant: Dilatant fluid is a shear thickening fluid Viscosity increases ,shear rate increases For example:traditional resin composite  4) Plastic fluid: Plastic fluid until certain yield stress is applied ,attain constant viscosity. The application of yield stress to cause flow in material is known as b

Tarnish and Corrosion

  TARNISH AND CORROSION  TARNISH : S urface discoloration  on a metal /even slight loss of surface finish. CORROSION:  D eterioration of a metal by reacting with environment,water ,oxygen,chloride ion,sulfide contribute corrosion attack. CAUSES FOR TARNISH    : Pigment producing bacteria formation of hard ,soft deposit on surface of restoration (eg-calculus) formation of thin film oxide and sulphide. CLASSIFICATION OF CORROSION CHEMICAL/DRY :  In chemical type of corrosion metal reacts to form oxide,sulphide  in the absence of  electrolyte for an example : oxidation of alloy particle in amalgam. 2) Electrochemical /wet corrosion: In electrochemical type of corrosion there will be formation of free electron ,electrolyte that provide pathway for transport of electrons. types of  electrochemical corrosion : A) galvanic corrosion B) concentration cell corrosion and C) stress corrosion  A) Galvanic corrosion:   When two dissimilar metal lie on direct contact with each other ,saliva acts

PLATELET (Thrombocyte) - Short notes

 PLATELET ( THROMBOCYTE ) THROMBOCYTE: THROMBO- CLOT,CYTE- CELL. SIZE : 2 - 4 micro meter in diameter  COLOR ;  colorless SHAPE: oval,disc shaped  Platelets are seen using specialized  stain such as leishmans stain ,on  staining   it appears bluish ,granular cytoplasm There is  NO NUCLEUS present in platelet and hence cannot be reproduced . Blood is a specialized body fluid . Blood products : white blood cells , red blood cells ,plasma ,platelet. WHITE BLOOD CELLS : colorless  ,nucleated cell,plays an important role in defense mechanism of body. white blood cell include : neutrophil,eosinophil,basophil,lymphocyte and monocyte . normal white blood cell count : 4,000 to 11,000 cells per milli meter cube . RED BLOOD CELLS:  Red blood cell develop from erythrocyte ,derived from progenitor cells. Normal hemoglobin level in blood :   A dult male - 15 to 18 gram per deci litre  Adult female - 11.5-13 gram per deci litre  N ewborn - 15 gram per deci litre   3 month old : 9 gram per deci li

Derivatives of germ layers

  DERIVATIVE OF GERM LAYERS INTRODUCTION : 1)Germ layers arise from a process of gastrulation ,an early phase of embryological development in which implanted blastula develops into 3 germ cell layers ,occur during 3rd week of development. 2) Its marked by extensive cell movement where blastula  becomes organised into 3 layers .  MORULA ( a ball of cells) ,BLASTULA(hallow ball) ,gastrulation ( 3 layers of hollow ball ) 3) BLASTOCOEL: fluid filled cavity that forms in the blastula of early amphibian and its functions is to permit cell migration during gastrulation and to prevent cell beneath it from interacting prematurely with other cells . DERIVATIVE OF ECTODERM : 1) Epidermis of skin ,hair,nail,sweat,sebaceous gland . 2) epidermis lower part of anal canal,terminal part of urinary and genital tract . 3)epidermis of cheek,gum,palate,oral cavity,nasal cavity,para nasal sinus 4) enamel of teeth  5) central nervous system : formed by neural crest cells  6) peripheral nervous system : retin