NEET MDS Synopsis
TOOTH MORPHOLOGY
Dental Anatomy
TOOTH MORPHOLOGY
Descriptive anatomy
Median sagittal plane: the imaginary plane in the center that divides right from left.
Median line: an imaginary line on that plane that bisects the dental arch at the center.
Mesial: toward the center (median) line of the dental arch.
Distal: away from the center (median) line of the dental arch.
Occlusal plane: A plane formed by the cusps of the teeth. It is often curved, as in a cylinder. We will speak often of the occlusal surface of a tooth.
Proximal: the surface of a tooth that is toward another tooth in the arch.
Mesial surface: toward the midline.
Distal surface: away from the midline.
Facial: toward the cheeks or lips.
Labial: facial surface of anterior teeth (toward the lips).
Buccal: facial surfaceof anterior teeth (toward the cheeks).
Lingual: toward the tongue.
Occlusal: the biting surface; that surface that articulates with an antagonist tooth in an opposing arch.
Incisal: cutting edge of anterior teeth.
Apical: toward the apex, the tip of the root.
Pantothenic Acid
Biochemistry
Pantothenic Acid
Pantothenic Acid is involved in energy production, and aids in the formation of hormones and the metabolism of fats, proteins, and carbohydrates from food.
RDA The Adequate Intake (AI) for Pantothenic Acid is 5 mg/day for both adult males and females.
Pantothenic Acid Deficiency
Pantothenic Acid deficiency is uncommon due to its wide availability in most foods.
Cavernous Sinus
AnatomyCavernous Sinus
Each cavernous sinus is a large venous space situated in the middle cranial fossa on either side of the body of the sphenoid bone. Its interior is divided into a number of trabeculae or caverns. The floor of the sinus is formed by the endosteal dura mater. The lateral wall, roof and medial wall are formed by the meningeal dura mater.
Structures in the lateral wall of the sinus from above downwards:
Oculomotor nerve
Trochlear nerve
Ophthalmic nerve - in the anterior part of the sinus, it divides into the lacrimal, frontal and nasociliary nerves.
Maxillary nerve - it leaves the sinus by passing through the foramen rotundum on its way to the pterygopalatine fossa.
Trigeminal ganglion - the ganglion and its dural cave project into the posterior part of the lateral wall of the sinus.
Structures passing through the centre of the sinus:
Internal carotid artery with the venous and sympathetic plexus around it.
Abducent nerve, inferolateral to the internal carotid artery.
Tributaries (incoming channels) of cavernous sinus
Superior ophthalmic vein.
A branch of inferior ophthalmic vein or sometimes vein itself.
Central vein of retina (it may also drain into superior ophthalmic vein).
Superficial middle cerebral vein.
Inferior cerebral vein.
Sphenoparietal sinus.
Frontal trunk of middle meningeal vein (it may also drain into pterygoid plexus or into sphenoparietal sinus).
Draining channels (communications) of cavernous sinus
Into transverse sinus through superior petrosal sinus.
Into internal jugular vein through inferior petrosal sinusand through a plexus around the ICA
Into pterygoid plexus of veinsthrough emissary veins.
Into facial vein through superior ophthalmic vein.
Right and left cavernous sinus communicates with each other by anterior and posterior intercavernous sinuses and through basilar plexus of veins.
Intrinsic Muscles of the Tongue
AnatomyIntrinsic Muscles of the Tongue
The Superior Longitudinal Muscle of the Tongue
The muscle forms a thin layer deep to the mucous membrane on the dorsum of the tongue, running from its tip to its root.
It arises from the submucosal fibrous layer and the lingual septum and inserts mainly into the mucous membrane.
This muscle curls the tip and sides of the tongue superiorly, making the dorsum of the tongue concave.
The Inferior Longitudinal Muscle of the Tongue
This muscle consists of a narrow band close to the inferior surface of the tongue.
It extends from the tip to the root of the tongue.
Some of its fibres attach to the hyoid bone.
This muscle curls the tip of the tongue inferiorly, making the dorsum of the tongue convex.
The Transverse Muscle of the Tongue
This muscle lies deep to the superior longitudinal muscle.
It arises from the fibrous lingual septum and runs lateral to its right and left margins.
Its fibres are inserted into the submucosal fibrous tissue.
The transverse muscle narrows and increases the height of the tongue.
The Vertical Muscle of the Tongue
This muscle runs inferolaterally from the dorsum of the tongue.
It flattens and broadens the tongue.
Acting with the transverse muscle, it increases the length of the tongue.
CHEMICAL AGENTS
General Microbiology
CHEMICAL AGENTS
Chlorine and iodine are most useful disinfectant Iodine as a skin disinfectant and chlorine as a water disinfectant have given consistently magnificent results. Their activity is almost exclusively bactericidal and they are effective against sporulating organisms also.
Mixtures of various surface acting agents with iodine are known as iodophores and these are used for the sterilization of dairy products.
Apart from chlorine, hypochlorite, inorganic chioramines are all good disinfectants but they act by liberating chlorine.
Hydrogen peroxide in a 3% solution is a harmless but very weak disinfectant whose primary use is in the cleansing of the wound.
Potassium permanganate is another oxidising agent which is used in the treatment of urethntzs.
Formaldehyde — is one of the least selective agent acting on proteins. It is a gas that is usually employed as its 37% solution, formalin.
When used in sufficiently high concentration it destroys the bacteria and their spores.
Classification of chemical sterilizing agents
Chemical disinfectant
Interfere with membrane functions
• Surface acting agents : Quaternary ammonium, Compounds, Soaps and fatty acids
• Phenols : Phenol, cresol, Hexylresorcinol
• Organic solvent : Chloroform, Alcohol
Denatures proteins
• Acids and alkalies : Organic acids, Hydrochloric acid , Sulphuric acid
Destroy functional groups of proteins
• Heavy metals : Copper, silver , Mercury
• Oxidizing agents: Iodine, chlorine, Hydrogen peroxide
• Dyes : Acridine orange, Acriflavine
• Alkylating agents : Formaldehyde, Ethylene oxide
Applications and in-use dilution of chemical disinfectants
Alcohols : Skin antiseptic Surface disinfectant, Dilution used 70%
Mercurials : Skin antiseptic Surface disinfectant Dilution Used 0.1 %
Silver nitrate : Antiseptic (eyes and burns) Dilution Used 1 %
Phenolic compound : Antiseptic skin washes Dilution Used .5 -5 %
Iodine : Disinfects inanimate object, Skin antiseptic Dilution used 2%
Chlorine compounds : Water treatment Disinfect inanimate objects , Dillution used 5 %
Quaternary ammonium Compounds : Skin antiseptic , Disinfects inanimate object, Dilution Used < 1 %
Glutaraldehyde: Heat sensitve instruments, Dilution used 1-2 %
Cold sterilization can be achieved by dipping the precleaned instrument in 2% solution of gluteraldehyde for 15-20 minutes. This time is sufficient to kill the vegetative form as well as spores ofthe organisms that are commonly encountered in the dentistry.
Ethylene oxide is an a agent extensively used in gaseous sterilization. It is active against all kinds of bacteria and their spores. but its greatest utility is in sterilizing those objects which are damaged by heat (e.g. heart lung machine). It is also used to sterlise fragile, heat sensitive equipment, powders as well as components of space crafts.
Evaluation of Disinfectants
Two methods which are widely employed are:
Phenol coefficient test, Kelsey -Sykes test
These tests determine the capacity of disinfectant as well as their ability to retain their activity.
Orthodontic MCQ 1
Orthodontics
1. An adult patient with a Class II molar relationship and a cephalometric ANB angle of 2 degrees has which type of malocclusion?
1. Class II dental malocclusion
2. Class II skeletal malocclusion
3. Class I dental malocclusion
4. Class II skeletal malocclusion
ans 1. The molars are Class II but the skeletal relationship described by a normal ANB measurement is normal, so the malocclusion is dental
in origin.
2. Which of the following reactions is least likely to be observed during orthodontic treatment?
1. Root resorption
2. Devitalization of teeth that are moved
3. Mobility of teeth that are moved
4. Development of occlusal interferences
Ans 2. Root resorption is common during orthodontic treatment, although lesions often repair on the root surface. Mobility of teeth is also common as the PDL reorganizes and widens during tooth movement. It is uncommon for teeth to become devitalized as a result of orthodontic movement unless they have also been substantially compromised by injury or infection.
3. A 7-year-old has a 4-mm maxillary midline diastema. Which of the following should be done?
1. Brackets should be placed to close it.
2. A radiograph should be taken to rule out the presence of a supernumerary tooth.
3. Nothing should be done. It will close on its own.
4. Nothing should be done. Treatment should be deferred until the rest of the permanent dentition erupts.
Ans. 2. When a large diastema greater than 2 mm is present, it will probably not close on its own. Diagnostic tests, such as a radiograph, should be accomplished to rule out the presence of a supernumerary tooth, usually a mesiodens.
4. When Class III elastics are used, the maxillary first molars will _____.
1. Move distally and intrude
2. Move mesially and extrude
3. Move mesially and intrude
4. Move only mesially; there will be no movement in the vertical direction
ans 2. Class III elastics are worn from the maxillary first molars to the mandibular canines. The force system created by Class III elastics will produce mesial movement and extrusion of the maxillary first molars.
5. Ideally, Orthodontic traction to pull an impacted tooth to line of arch should begin
1. at 2-3 months post surgically
2. As soon as possible after surgery
3. After a waiting period of at least1.5 months
4. Only the method of traction is critical, not the time
ans 2
Mechanical approaches for aligning unerupted teeth. Orthodontic traction to pull an unerupted tooth toward the line of the arch
should begin as soon as possible after surgery Ideally a fixed orthodontic appliance should already be in place before the unerupted tooth is exposed, so that orthodontic force can be applied immediately. If this is not practical, active orthodontic
movement should being no later than 2 or 3 weeks post-surgically.
Plasma
PhysiologyPlasma: is the straw-colored liquid in which the blood cells are suspended.
Composition of blood plasma
Component
Percent
Water
~92
Proteins
6–8
Salts
0.8
Lipids
0.6
Glucose (blood sugar)
0.1
Plasma transports materials needed by cells and materials that must be removed from cells:
various ions (Na+, Ca2+, HCO3−, etc.
glucose and traces of other sugars
amino acids
other organic acids
cholesterol and other lipids
hormones
urea and other wastes
Most of these materials are in transit from a place where they are added to the blood
exchange organs like the intestine
depots of materials like the liver
to places where they will be removed from the blood.
every cell
exchange organs like the kidney, and skin.
Garre’s Osteomyelitis
Oral Pathology
Garre’s Osteomyelitis (Chronic Osteomyelitis with Proliferative Perosteitis)
Chronic Non Suppurative Sclerosing Osteitis/ Periostitis Ossificans.
Non suppurative productive disease characterized by a hard swelling.
Occurs due to low grade infection and irritation
The infectious agent localizes in or beneath the periosteal covering of the cortex & spreads only slightly into the interior of the bone.
Occurs primarily in young persons who possess great osteogenic activity of the periosteum.
Clinical Features
Uncommonly encountered, described in tibia and in the head and neck region, in the mandible.
Typically involves the posterior mandible & is usually unilateral.
Patients present with an asymptomatic bony, hard swelling with normal appearing overlying skin and mucosa.
On occasion slight tenderness may be noted
pain is most constant feature
The increase in the mass of bone may be due to mild toxic stimulation of periosteal osteoblasts by attenuated infection.
Radiographic features
Laminations vary from 1 – 12 in number, radiolucent separations often are present between new bone and original cortex. (“onion skin appearance”)
Trabeculae parallel to laminations may also be present.
Histologic Features
Reactive new bone.
Parallel rows of highly cellular & reactive woven bone in which the individual trabeculae are oriented perpendicular to surface.
Osteoblasts predominate in this area.
D/D for Garre’s Osteomyelitis
Ewing's sarcoma
Caffey’s disease
Fibrous dysplasia
Osteosarcoma
Treatment
Removal of the offending cause.
Once inflammation resolves, layers of the bone consolidate in 6 – 12 months, as the overlying muscle helps to remodel.
If no focus of infection evident, biopsy recommended.