NEET MDS Synopsis
Dimensions of Toothbrushes
PeriodontologyDimensions of Toothbrushes
Toothbrushes play a crucial role in maintaining oral hygiene, and their
design can significantly impact their effectiveness. The American Dental
Association (ADA) has established guidelines for the dimensions and
characteristics of acceptable toothbrushes. This lecture will outline these
specifications and discuss their implications for dental health.
Acceptable Dimensions of Toothbrushes
Brushing Surface Dimensions:
Length:
Acceptable brushing surfaces should measure between 1 to
1.25 inches (25.4 to 31.8 mm) long.
Width:
The width of the brushing surface should range from 5/16
to 3/8 inch (7.9 to 9.5 mm).
Rows of Bristles:
Toothbrushes should have 2 to 4 rows of bristles to
effectively clean the teeth and gums.
Tufts per Row:
Each row should contain 5 to 12 tufts of
bristles, allowing for adequate coverage and cleaning ability.
Filament Diameter:
The diameter of the bristles can vary, affecting the stiffness and
cleaning effectiveness:
Soft Filaments:
Diameter of 0.2 mm (0.007 inches). Ideal
for sensitive gums and children.
Medium Filaments:
Diameter of 0.3 mm (0.012 inches). Suitable
for most adults.
Hard Filaments:
Diameter of 0.4 mm (0.014 inches).
Generally not recommended for daily use as they can be abrasive
to the gums and enamel.
Filament Stiffness:
The stiffness of the bristles is determined by the diameter relative
to the length of the filament. Thicker filaments tend to be stiffer,
which can affect the brushing technique and comfort.
Special Considerations for Children's Toothbrushes
Size:
Children's toothbrushes are designed to be smaller to accommodate
their smaller mouths and teeth.
Bristle Thickness:
The bristles are thinner, measuring 0.005 inches (0.1
mm) in diameter, making them gentler on sensitive gums.
Bristle Length:
The bristles are shorter, typically around 0.344 inches (8.7
mm), to ensure effective cleaning without causing discomfort.
Clinical Implications
Choosing the Right Toothbrush:
Dental professionals should guide patients in selecting toothbrushes
that meet ADA specifications to ensure effective plaque removal and gum
protection.
Emphasizing the importance of using soft or medium bristles can help
prevent gum recession and enamel wear.
Education on Brushing Technique:
Proper brushing technique is as important as the toothbrush itself.
Patients should be educated on how to use their toothbrush effectively,
regardless of the type they choose.
Regular Replacement:
Patients should be advised to replace their toothbrush every 3
to 4 months or sooner if the bristles become frayed. This
ensures optimal cleaning effectiveness.
Special Considerations for Children:
Parents should be encouraged to choose appropriately sized
toothbrushes for their children and to supervise brushing to ensure
proper technique and effectiveness.
GENERAL SOMATIC AFFERENT (GSA) PATHWAYS FROM THE BODY
Physiology
GENERAL SOMATIC AFFERENT (GSA) PATHWAYS FROM THE BODY
Pain and Temperature
Pain and temperature information from general somatic receptors is conducted over small-diameter (type A delta and type C) GSA fibers of the spinal nerves into the posterior horn of the spinal cord gray matter .
Fast and Slow Pain
Fast pain, often called sharp or pricking pain, is usually conducted to the CNS over type A delta fibers.
Slow pain, often called burning pain, is conducted to the CNS over smaller-diameter type C fibers.
Touch and Pressure
Touch can be subjectively described as discriminating or crude.
Discriminating (epicritic) touch implies an awareness of an object's shape, texture, three-dimensional qualities, and other fine points. Ability to recognize familiar objects simply by tactile manipulation.
The conscious awareness of body position and movement is called the kinesthetic sens
Crude (protopathic) touch, lacks the fine discrimination described above and doesn't generally give enough information to the brain to enable it to recognize a familiar object by touch alone.
Subconscious Proprioception
Most of the subconscious proprioceptive input is shunted to the cerebellum.
Posterior Funiculus Injury
Certain clinical signs are associated with injury to the dorsal columns.
As might be expected, these are generally caused by impairment to the kinesthetic sense and discriminating touch and pressure pathways.
They include
(1) the inability to recognize limb position,
(2) astereognosis,
(3) loss of two-point discrimination,
(4) loss of vibratory sense, and
(5) a positive Romberg sign.
Astereognosis is the inability to recognize familiar objects by touch alone. When asked to stand erect with feet together and eyes closed, a person with dorsal column damage may sway and fall. This is a positive Romberg sign.
TRACHEOSTOMY TUBES
Surgery
TYPES OF TRACHEOSTOMY TUBE
A tracheostomy tube may be metallic or nonmetallic
Metallic Tracheostomy Tube
Metallic tubes are formed from the alloy of silver, copper and phosphorus
Example Jackson’s Tracheostomy tube.
Has an inner and an outer tube.The inner tube is longer than the outer one so that secretions and crusts formed in it can be removed and the tube reinserted after cleaning without difficulty. However, they do not have a cuff and cannot produce an airtight seal.
Advantages of a double lumen tracheostomy tube are easy to remove,clean and replace inner cannula.
Inner cannula should be removed and cleaned as and when indicated for the first 3 days. Outer tube, unless blocked or displaced, should not be removed for 3-4 days to allow a track to be formed when tube placement will be easy.
Nonmetallic Tracheostomy Tube
Can be of cuffed or noncuffed variety, e.g. rubber and PVC tubes.
Cuffed Tracheostomy Tubes
Pediatric tubes do not have a cuff.
Cuffed tubes are used in situation where positive pressure ventilation is required, or when the airway is at risk from aspiration. (In unconscious patient or when patient is on respiration).
The cuff should be deflated every 2 hours for 5 mins to present pressure damage to the trachea.
Uncuffed Tracheostomy Tubes
It is suitable for a patient who has returned to the ward from a prolonged stay in intensive care and requires physiotherapy and suction via trachea.
This type of tube is not suitable for patients who are unable to swallow due to incompetent laryngeal reflexes, and aspiration of oral or gastric contents is likely to occur.
An uncuffed tube is advantageous in that it allows the patient to breathe around it in the event of the tube becoming blocked. Patients can also speak with an uncuffed tube.
Important
Nonmetallic Tracheostomy Tube - Cuffed tubes are used in situation where positive pressure ventilation is required, or when the airway is at risk from aspiration. (In unconscious patient or when patient is on respiration).
Metallic Tracheostomy Tube -Metallic tubes are formed from the alloy of silver, copper and phosphorus .
Example Jackson’s Tracheostomy tube.
Advantages of a double lumen tracheostomy tube are easy to remove,clean and replace inner cannula.
CASTING
Dental Materials
CASTING: casting is the process by which the wax pattern of a restoration is converted to a replicate in a dental alloy. The casting process is used to make dental restorations such as inlays, onlays, crowns, bridges and removable partial dentures.
Objectives of casting
1) To heat the alloy as quickly as possible to a completely molten condition.
2) To prevent oxidation by heating the metal with awell adjusted torch .
3) To produce a casting with sharp details by having adequate pressure to the well melted metal to force into the mold.
STEPS IN MAKING A CAST RESTORATION
1. TOOTH PREPARATION
2. IMPRESSION
3. DIE PREPARATION
4. WAX PATTERN FABRICATION
5. SPRUING
N. meningiditis
General Pathology
N. meningiditis
Major cause of fulminant bacteremia and meningitis. Has a unique polysaccharide capsule. It is spread person to person by the respiratory route. Frequently carried in nasopharynx, and carriage rates increased by close quarters. Special risk in closed populations (college dorms) and in people lacking complement. Sub-saharan Africa has a “meningitis belt.”
Pathogenesis is caused by adherence factors that attach to non-ciliated nasopharyngeal epithelium. These factors include pili which promote the intial epithelial (and erythrocyte) attachment, and Opa/Opc surface binding proteins.
Adherence stimulates engulfment of bacteria by epithelial cells. Transported to basolateral surface.
The polysaccharide capsule is a major virulence factor that prevents phagocytosis and lysis.
A lipo-oligosaccharide endotoxin also contributes to sepsis.
Tetracycline
Pharmacology
Tetracycline
Tetracycline is an antibiotic produced by the streptomyces bacterium
Mechanism and Resistance Tetracycline inhibits cell growth by inhibiting translation. It binds to the 30S ribosomal subunit and prevents the amino-acyl tRNA from binding to the A site of the ribosome. This prevents the addition of amino acids to the elongating peptide chain, preventing synthesis of proteins. The binding is reversible in nature.
Example: Chlortetracycline, oxytetracycline, demethylchlortetracycline, rolitetracycline, limecycline, clomocycline, methacycline, doxycycline, minocycline
Source: Streptomyces spp.; some are also semi-synthetic
Spectrum of activity: Broad-spectrum. Exhibits activity against a wide range of Gram-positive, Gram-negative bacteria, atypical organisms such as chlamydiae, mycoplasmas, rickettsiae and protozoan parasites.
Effect on bacteria: Bacteriostatic
Cells become resistant to tetracyline by at least two mechanisms: efflux and ribosomal protection.
Contraindications Tetracycline use should be avoided during pregnancy and in the very young (less than 6 years) because it will result in permanent staining of teeth causing an unsightly cosmetic result.
Tetracyclines also become dangerous past their expiration dates. While most prescription drugs lose potency after their expiration dates, tetracyclines are known to become toxic over time; expired tetracyclines can cause serious damage to the kidneys.
Miscellaneous: Tetracyclines have also been used for non-antibacterial purposes, having shown properties such as anti-inflammatory activity, immunosuppresion, inhibition of lipase and collagenase activity, and wound healing.
Griseofulvin
Pharmacology
Griseofulvin
Griseofulvin is an antifungal drug. It is used both in animals and in humans, to treat ringworm infections of the skin and nails. It is derived from the mold Penicillium griseofulvum.
It is administered orally.
Pancreas
Physiology
The bulk of the pancreas is an exocrine gland secreting pancreatic fluid into the duodenum after a meal. However, scattered through the pancreas are several hundred thousand clusters of cells called islets of Langerhans. The islets are endocrine tissue containing four types of cells. In order of abundance, they are the:
beta cells, which secrete insulin and amylin;
alpha cells, which secrete glucagon;
delta cells, which secrete somatostatin, and
gamma cells, which secrete a polypeptide of unknown function.
Beta Cells
Beta cells secrete insulin in response to a rising level of blood sugar
Insulin affects many organs. It
stimulates skeletal muscle fibers to
take up glucose and convert it into glycogen;
take up amino acids from the blood and convert them into protein.
acts on liver cells
stimulating them to take up glucose from the blood and convert it into glycogen while
inhibiting production of the enzymes involved in breaking glycogen back down (glycogenolysis) and
inhibiting gluconeogenesis; that is, the conversion of fats and proteins into glucose.
acts on fat (adipose) cells to stimulate the uptake of glucose and the synthesis of fat.
acts on cells in the hypothalamus to reduce appetite.
Diabetes Mellitus
Diabetes mellitus is an endocrine disorder characterized by many signs and symptoms. Primary among these are:
a failure of the kidney to retain glucose .
a resulting increase in the volume of urine because of the osmotic effect of this glucose (it reduces the return of water to the blood).
There are three categories of diabetes mellitus:
Insulin-Dependent Diabetes Mellitus (IDDM) (Type 1) and
Non Insulin-Dependent Diabetes Mellitus (NIDDM)(Type 2)
Inherited Forms of Diabetes Mellitus
Insulin-Dependent Diabetes Mellitus (IDDM)
IDDM ( Type 1 diabetes)
is characterized by little or no circulating insulin;
most commonly appears in childhood.
It results from destruction of the beta cells of the islets.
The destruction results from a cell-mediated autoimmune attack against the beta cells.
What triggers this attack is still a mystery, although a prior viral infection may be the culprit.
Non Insulin-Dependent Diabetes Mellitus (NIDDM)
Many people develop diabetes mellitus without an accompanying drop in insulin levels In many cases, the problem appears to be a failure to express a sufficient number of glucose transporters in the plasma membrane (and T-system) of their skeletal muscles. Normally when insulin binds to its receptor on the cell surface, it initiates a chain of events that leads to the insertion in the plasma membrane of increased numbers of a transmembrane glucose transporter. This transporter forms a channel that permits the facilitated diffusion of glucose into the cell. Skeletal muscle is the major "sink" for removing excess glucose from the blood (and converting it into glycogen). In NIDDM, the patient's ability to remove glucose from the blood and convert it into glycogen is reduced. This is called insulin resistance. NIDDM (also called Type 2 diabetes mellitus) usually occurs in adults and, particularly often, in overweight people.
Alpha Cells
The alpha cells of the islets secrete glucagon, a polypeptide of 29 amino acids. Glucagon acts principally on the liver where it stimulates the conversion of glycogen into glucose (glycogenolysis) which is deposited in the blood.
Glucagon secretion is
stimulated by low levels of glucose in the blood;
inhibited by high levels, and
inhibited by amylin.
The physiological significance of this is that glucagon functions to maintain a steady level of blood sugar level between meals.
Delta Cells
The delta cells secrete somatostatin. Somatostatin has a variety of functions. Taken together, they work to reduce the rate at which food is absorbed from the contents of the intestine. Somatostatin is also secreted by the hypothalamus and by the intestine.
Gamma Cells
The gamma cells of the islets secrete pancreatic polypeptide. No function has yet been found for this peptide of 36 amino acids.