NEET MDS Synopsis
The Submandibular Glands
AnatomyThe Submandibular Glands
Each of these U-shaped salivary glands is about the size of a thumb and lies along the body of the mandible.
It is partly superior and partly inferior to the posterior 1/2 of the base of the mandible.
It is partly superficial and partly deep to the mylohyoid muscle.
The submandibular duct arises from the portion of the gland that lies between the mylohyoid and hyoglossus muscle.
The duct passes deep and then superficial to the lingual nerve.
It opens by one to three orifices on a small sublingual papilla beside the lingual frenulum.
The submandibular gland is supplied by parasympathetic, secretomotor fibres from the submandibular ganglion (preganglionic fibres from the chorda tympani via the lingual nerve).
Osteoporosis
General Pathology
Osteoporosis
is characterized by increased porosity of the skeleton resulting from reduced bone mass. The disorder may be localized to a certain bone (s), as in disuse osteoporosis of a limb, or generalized involving the entire skeleton. Generalized osteoporosis may be primary, or secondary
Primary generalized osteoporosis
• Postmenopausal
• Senile
Secondary generalized osteoporosis
A. Endocrine disorders
• Hyperparathyroidism
• Hypo or hyperthyroidism
• Others
B. Neoplasia
• Multiple myeloma
• Carcinomatosis
C. Gastrointestinal disorders
• Malnutrition & malabsorption
• Vit D & C deficiency
• Hepatic insufficiency
D. Drugs
• Corticosteroids
• Anticoagulants
• Chemotherapy
• Alcohol
E. Miscellaneous
• osteogenesis imperfecta
• immobilization
• pulmonary disease
Senile and postmenopausal osteoporosis are the most common forms. In the fourth decade in both sexes, bone resorption begins to overrun bone deposition. Such losses generally occur in areas containing abundant cancelloues bone such as the vertebrae & femoral neck. The postmenopausal state accelerates the rate of loss; that is why females are more susceptible to osteoporosis and its complications.
Gross features
• Because of bone loss, the bony trabeculae are thinner and more widely separated than usual. This leads to obvious porosity of otherwise spongy cancellous bones
Microscopic features
• There is thinning of the trabeculae and widening of Haversian canals.
• The mineral content of the thinned bone is normal, and thus there is no alteration in the ratio of minerals to protein matrix
Etiology & Pathogenesis
• Osteoporosis involves an imbalance of bone formation, bone resorption, & regulation of osteoclast activation. It occurs when the balance tilts in favor of resorption.
• Osteoclasts (as macrophages) bear receptors (called RANK receptors) that when stimulated activate the nuclear factor (NFκB) transcriptional pathway. RANK ligand synthesized by bone stromal cells and osteoblasts activates RANK. RANK activation converts macrophages into bone-crunching osteoclasts and is therefore a major stimulus for bone resorption.
• Osteoprotegerin (OPG) is a receptor secreted by osteoblasts and stromal cells, which can bind RANK ligand and by doing so makes the ligand unavailable to activate RANK, thus limiting osteoclast bone-resorbing activity.
• Dysregulation of RANK, RANK ligand, and OPG interactions seems to be a major contributor in the pathogenesis of osteoporosis. Such dysregulation can occur for a variety of reasons, including aging and estrogen deficiency.
• Influence of age: with increasing age, osteoblasts synthetic activity of bone matrix progressively diminished in the face of fully active osteoclasts.
• The hypoestrogenic effects: the decline in estrogen levels associated with menopause correlates with an annual decline of as much as 2% of cortical bone and 9% of cancellous bone. The hypoestrogenic effects are attributable in part to augmented cytokine production (especially interleukin-1 and TNF). These translate into increased RANK-RANK ligand activity and diminished OPG.
• Physical activity: reduced physical activity increases bone loss. This effect is obvious in an immobilized limb, but also occurs diffusely with decreased physical activity in older individuals.
• Genetic factors: these influence vitamin D receptors efficiency, calcium uptake, or PTH synthesis and responses.
• Calcium nutritional insufficiency: the majority of adolescent girls (but not boys) have insufficient dietary intake of calcium. As a result, they do not achieve the maximal peak bone mass, and are therefore likely to develop clinically significant osteoporosis at an earlier age.
• Secondary causes of osteoporosis: these include prolonged glucocorticoid therapy (increases bone resorption and reduce bone synthesis.)
The clinical outcome of osteoporosis depends on which bones are involved. Thoracic and lumbar vertebral fractures are extremely common, and produce loss of height and various deformities, including kyphoscoliosis that can compromise respiratory function. Pulmonary embolism and pneumonia are common complications of fractures of the femoral neck, pelvis, or spine.
Vitiligo
General Pathology
Vitiligo is an autoimmune destruction of melanocytes resulting in areas of depigmentation.
- commonly associated with other autoimmune diseases such as pernicious anemia, Addison's disease, and thyroid disease.
- common in the Black population
Types of Fixed Orthodontic Appliances
OrthodonticsTypes of Fixed Orthodontic Appliances
Braces:
Traditional Metal Braces: Composed of metal
brackets bonded to the teeth, connected by archwires. They are the most
common type of fixed appliance.
Ceramic Braces: Similar to metal braces but made of
tooth-colored or clear materials, making them less visible.
Lingual Braces: Brackets are placed on the inner
surface of the teeth, making them invisible from the outside.
Self-Ligating Braces:
These braces use a specialized clip mechanism to hold the archwire
in place, eliminating the need for elastic or metal ligatures. They can
reduce friction and may allow for faster tooth movement.
Space Maintainers:
Fixed appliances used to hold space for permanent teeth when primary
teeth are lost prematurely. They are typically bonded to adjacent teeth.
Temporary Anchorage Devices (TADs):
Small screws or plates that are temporarily placed in the bone to
provide additional anchorage for tooth movement. They help in achieving
specific movements without unwanted tooth movement.
Palatal Expanders:
Fixed appliances used to widen the upper jaw (maxilla) by applying
pressure to the molars. They are often used in growing patients to
correct crossbites or narrow arches.
Components of Fixed Orthodontic Appliances
Brackets: Small metal or ceramic attachments bonded to
the teeth. They hold the archwire in place and guide tooth movement.
Archwires: Thin metal wires that connect the brackets
and apply pressure to the teeth. They come in various materials and sizes,
and their shape can be adjusted to achieve desired movements.
Ligatures: Small elastic or metal ties that hold the
archwire to the brackets. In self-ligating braces, ligatures are not needed.
Bands: Metal rings that are cemented to the molars to
provide anchorage for the appliance. They may have attachments for brackets
or other components.
Hooks and Accessories: Additional components that can
be attached to brackets or bands to facilitate the use of elastics or other
auxiliary devices.
Indications for Use
Correction of Malocclusions: Fixed appliances are
commonly used to treat various types of malocclusions, including crowding,
spacing, overbites, underbites, and crossbites.
Tooth Movement: They are effective for moving teeth
into desired positions, including tipping, bodily movement, and rotation.
Retention: Fixed retainers may be used after active
treatment to maintain the position of teeth.
Jaw Relationship Modification: Fixed appliances can
help in correcting skeletal discrepancies and improving the relationship
between the upper and lower jaws.
Advantages of Fixed Orthodontic Appliances
Continuous Force Application: Fixed appliances provide
a constant force on the teeth, allowing for more predictable and efficient
tooth movement.
Effective for Complex Cases: They are suitable for
treating a wide range of orthodontic issues, including severe malocclusions
that may not be effectively treated with removable appliances.
Patient Compliance: Since they are fixed, there is no
reliance on patient compliance for wearing the appliance, which can lead to
more consistent treatment outcomes.
Variety of Options: Patients can choose from various
types of braces (metal, ceramic, lingual) based on their aesthetic
preferences.
Disadvantages of Fixed Orthodontic Appliances
Oral Hygiene Challenges: Fixed appliances can make it
more difficult to maintain oral hygiene, increasing the risk of plaque
accumulation, cavities, and gum disease.
Discomfort: Patients may experience discomfort or
soreness after adjustments, especially in the initial stages of treatment.
Dietary Restrictions: Certain foods (hard, sticky, or
chewy) may need to be avoided to prevent damage to the appliances.
Duration of Treatment: Treatment with fixed appliances
can take several months to years, depending on the complexity of the case.
Supporting Cusps in Dental Occlusion
Conservative DentistrySupporting Cusps in Dental Occlusion
Supporting cusps, also known as stamp cusps, centric holding cusps, or
holding cusps, play a crucial role in dental occlusion and function. They are
essential for effective chewing and maintaining the vertical dimension of the
face. This guide will outline the characteristics, functions, and clinical
significance of supporting cusps.
Supporting Cusps: These are the cusps of the maxillary
and mandibular teeth that make contact during maximum intercuspation (MI)
and are primarily responsible for supporting the vertical dimension of the
face and facilitating effective chewing.
Location
Maxillary Supporting Cusps: Located on the lingual
occlusal line of the maxillary teeth.
Mandibular Supporting Cusps: Located on the facial
occlusal line of the mandibular teeth.
Functions of Supporting Cusps
A. Chewing Efficiency
Mortar and Pestle Action: Supporting cusps contact the
opposing teeth in their corresponding faciolingual center on a marginal
ridge or a fossa, allowing them to cut, crush, and grind fibrous food
effectively.
Food Reduction: The natural tooth form, with its
multiple ridges and grooves, aids in the reduction of the food bolus during
chewing.
B. Stability and Alignment
Preventing Drifting: Supporting cusps help prevent the
drifting and passive eruption of teeth, maintaining proper occlusal
relationships.
Characteristics of Supporting Cusps
Supporting cusps can be identified by the following five characteristic
features:
Contact in Maximum Intercuspation (MI): They make
contact with the opposing tooth during MI, providing stability in occlusion.
Support for Vertical Dimension: They contribute to
maintaining the vertical dimension of the face, which is essential for
proper facial aesthetics and function.
Proximity to Faciolingual Center: Supporting cusps are
located nearer to the faciolingual center of the tooth compared to
nonsupporting cusps, enhancing their functional role.
Potential for Contact on Outer Incline: The outer
incline of supporting cusps has the potential for contact with opposing
teeth, facilitating effective occlusion.
Broader, Rounded Cusp Ridges: Supporting cusps have
broader and more rounded cusp ridges than nonsupporting cusps, making them
better suited for crushing food.
Clinical Significance
A. Occlusal Relationships
Maxillary vs. Mandibular Arch: The maxillary arch is
larger than the mandibular arch, resulting in the supporting cusps of the
maxilla being more robust and better suited for crushing food than those of
the mandible.
B. Lingual Tilt of Posterior Teeth
Height of Supporting Cusps: The lingual tilt of the
posterior teeth increases the relative height of the supporting cusps
compared to nonsupporting cusps, which can obscure central fossa contacts.
C. Restoration Considerations
Restoration Fabrication: During the fabrication of
restorations, it is crucial to ensure that supporting cusps do not contact
opposing teeth in a manner that results in lateral deflection. Instead,
restorations should provide contacts on plateaus or smoothly concave fossae
to direct masticatory forces parallel to the long axes of the teeth.
Empyema
Medicine
• Thoracic empyema is purulent pleural effusion
• End stage of pleural effusion if not treated properly
• Thick pus with a thick cortex of fibrin and coagulum over lung
Etiology
Most common cause : Parapneumonic, Postsurgical & post-traumatic
Most common: pneumonia → extension of bacterial infection into the pleural space
Less common: infected hemothorax, ruptured lung abscess, esophageal tear, thoracic trauma
Empyema due to pneumonia three phase
The exudative phase :
- protein > 3g/100 ml
- Infection from lung
- Antibiotics & aspiration or drainage
The fibrinopurulent phase :(next few days)
Pleural fluid become thick ,
Drainage must
The organized phase:
- Lung trapped by thick peel or cortex
- Surgical management
- VATS,
- thorocotomy
Condition predispose to Empyema
Pulmonary infection:
- Unresolved pneumonia
- Broncietasis
- Tuberculosis
- Fungal infection
- Lung abscess
Aspiration of pleural effusion
Trauma :
- Penetrating injury
- Surgery
- Oesophgeal peforation
Extrapulmonary sources : Subphernic abscess
Bone infection osteomyelitits ribs and vertebra
Smallpox (variola)
General Pathology
Smallpox (variola)
- vesicles are well synchronized (same stage of development) and cover the skin and mucous membranes.
- vesicles rupture and leave pock marks with permanent scarring.
HISTOLOGIC CHANGES OF THE PULP
Dental Anatomy
HISTOLOGIC CHANGES OF THE PULP
Regressive changes
Pulp decreases in size by the deposition of dentin.
This can be caused by age, attrition, abrasion, operative procedures, etc.
Cellular organelles decrease in number.
Fibrous changes
They are more obvious in injury rather than aging. Occasionally, scarring may also be apparent.
Pulpal stones or denticles
They can be: a)free, b)attached and/or c)embedded. Also they are devided in two groups: true or false. The true stones (denticles) contain dentinal tubules. The false predominate over the the true and are characterized by concentric layers of calcified material.
Diffuse calcifications
Calcified deposits along the collagen fiber bundles or blood vessels may be observed. They are more often in the root canal portion than the coronal area.
Histology of the Cementum
Cementum is a hard connective tissue that derives from ectomesenchyme.
Embryologically, there are two types of cementum:
Primary cementum: It is acellular and develops slowly as the tooth erupts. It covers the coronal 2/3 of the root and consists of intrinsic and extrinsic fibers (PDL).
Secondary cementum: It is formed after the tooth is in occlusion and consists of extrinsic and intrinsic (they derive from cementoblasts) fibers. It covers mainly the root surface.
Functions of Cementum
It protects the dentin (occludes the dentinal tubules)
It provides attachment of the periodontal fibers
It reverses tooth resorption
Cementum is composed of 90% collagen I and III and ground substance.
50% of cementum is mineralized with hydroxyapatite. Thin at the CE junction, thicker apically.