NEET MDS Synopsis
SALIVARY GLANDS Embryonic development
Dental Anatomy
Embryonic development
The parotid derives from ectoderm
The sublingual-submandibular glands thought to derive from endoderm
Differentiation of the ectomesenchyme
Development of fibrous capsule
Formation of septa that divide the gland into lobes and lobules
The parotid develops around 4-6 weeks of embryonic lofe
The submandibular gland develops around the 6th week
The sublingual and the minor glands develop around the 8-12 week
RESPIRATORY DISORDERS - Cystic Fibrosis
PhysiologyCystic Fibrosis
→ Thick mucus coagulates in ducts, produces obstruction, Too thick for cilia to move
→ Major Systems Affected: Respiratory System, G. I. Tract,Reproductive Tract
→ Inherited, autosomal recessive gene, most common fatal genetic disorder
→ Major characteristic, Altered electrolyte composition (Saliva & sweat Na+, K+, Cl-)
→ Family history of Cystic Fibrosis
→ Respiratory Infections & G.I.Tract malabsorption
→ Predisposes lung to Secondary infection (Staphylococcus, Pseudomonas)
→ Damages Respiratory Bronchioles and Alveolar ducts, Produces Fibrosis of Lungs, Large cystic dilations)
Introduction
Dental Materials
Introduction
The science of dental materials involves a study of the composition and properties of materials and the way in which they interact with the environment in which they are placed
Selection of Dental materials
The process of materials selection should ideally follow a logical sequence involving
(1) analysis of the problem,
(2) consideration of requirements,
(3) consideration of available materials and their properties, leading to
(4) choice of material.
Evaluation of the success or failure of a material may be used to influence future decisions on materials selection.
Endocrine System
Physiology
The endocrine system along with the nervous system functions in the regulation of body activities. The nervous system acts through electrical impulses and neurotransmitters to cause muscle contraction and glandular secretion and interpretation of impulses. The endocrine system acts through chemical messengers called hormones that influence growth, development, and metabolic activities
Pentose Phosphate Pathway (Hexose Monophosphate Shunt)
Biochemistry
Pentose Phosphate Pathway (Hexose Monophosphate Shunt)
The pentose phosphate pathway is primarily an anabolic pathway that utilizes the 6 carbons of glucose to generate 5 carbon sugars and reducing equivalents. However, this pathway does oxidize glucose and under certain conditions can completely oxidize glucose to CO2 and water. The primary functions of this pathway are:
To generate reducing equivalents, in the form of NADPH, for reductive biosynthesis reactions within cells.
To provide the cell with ribose-5-phosphate (R5P) for the synthesis of the nucleotides and nucleic acids.
Although not a significant function of the PPP, it can operate to metabolize dietary pentose sugars derived from the digestion of nucleic acids as well as to rearrange the carbon skeletons of dietary carbohydrates into glycolytic/gluconeogenic intermediates
Enzymes that function primarily in the reductive direction utilize the NADP+/NADPH cofactor pair as co-factors as opposed to oxidative enzymes that utilize the NAD+/NADH cofactor pair. The reactions of fatty acid biosynthesis and steroid biosynthesis utilize large amounts of NADPH. As a consequence, cells of the liver, adipose tissue, adrenal cortex, testis and lactating mammary gland have high levels of the PPP enzymes. In fact 30% of the oxidation of glucose in the liver occurs via the PPP. Additionally, erythrocytes utilize the reactions of the PPP to generate large amounts of NADPH used in the reduction of glutathione. The conversion of ribonucleotides to deoxyribonucleotides (through the action of ribonucleotide reductase) requires NADPH as the electron source, therefore, any rapidly proliferating cell needs large quantities of NADPH.
Regulation: Glucose-6-phosphate Dehydrogenase is the committed step of the Pentose Phosphate Pathway. This enzyme is regulated by availability of the substrate NADP+. As NADPH is utilized in reductive synthetic pathways, the increasing concentration of NADP+ stimulates the Pentose Phosphate Pathway, to replenish NADPH
Transoral Lithotomy
Oral and Maxillofacial SurgeryTransoral Lithotomy: Procedure for Submandibular Duct Stone Removal
Transoral lithotomy is a surgical technique used to remove
stones (calculi) from the submandibular duct (Wharton's duct). This procedure is
typically performed under local anesthesia and is effective for addressing
sialolithiasis (the presence of stones in the salivary glands).
Procedure
Preoperative Preparation:
Radiographic Assessment: The exact location of the
stone is determined using imaging studies, such as X-rays or ultrasound,
to guide the surgical approach.
Local Anesthesia: The procedure is performed under
local anesthesia to minimize discomfort for the patient.
Surgical Technique:
Suture Placement: A suture is placed behind the
stone to prevent it from moving backward during the procedure,
facilitating easier access.
Incision: An incision is made in the mucosa of the
floor of the mouth, parallel to the duct. Care is taken to avoid injury
to surrounding structures, including:
Lingual Nerve: Responsible for sensory
innervation to the tongue.
Submandibular Gland: The gland itself should be
preserved to maintain salivary function.
Blunt Dissection:
After making the incision, blunt dissection is performed to
carefully displace the surrounding tissue and expose the duct.
Identifying the Duct:
The submandibular duct is located, and the segment of the duct that
contains the stone is identified.
Stone Removal:
A longitudinal incision is made over the stone within the duct. The
stone is then extracted using small forceps. Care is taken to ensure
complete removal to prevent recurrence.
Postoperative Considerations:
After the stone is removed, the incision may be closed with sutures,
and the area is monitored for any signs of complications.
Complications
Bacterial Sialadenitis: If there is a secondary
infection following the procedure, it can lead to bacterial sialadenitis,
which is an inflammation of the salivary gland due to infection. Symptoms
may include pain, swelling, and purulent discharge from the duct.
Amyotrophic lateral sclerosis
General Pathology
Amyotrophic lateral sclerosis (Lou Gehrig’s disease)
a. Characterized by the rapid degeneration of motor neurons in the spinal cord and corticospinal tracts.
b. More common in men in their 50s.
c. Clinically, the disease results in rapidly progressive muscle atrophy due to denervation. Other symptoms include fasciculations, hyperreflexia, spasticity, and pathologic reflexes. Death usually occurs within a few years from onset, usually by respiratory failure or infection.
Capacity of Motion of the Mandible
Conservative DentistryCapacity of Motion of the Mandible
The capacity of motion of the mandible is a crucial aspect of dental and
orthodontic practice, as it influences occlusion, function, and treatment
planning. In 1952, Dr. Harold Posselt developed a systematic approach to
recording and analyzing mandibular movements, resulting in what is now known as
Posselt's diagram. This guide will provide an overview of Posselt's work, the
significance of mandibular motion, and the key points of reference used in
clinical practice.
1. Posselt's Diagram
A. Historical Context
Development: In 1952, Dr. Harold Posselt utilized a
system of clutches and flags to record the motion of the mandible. His work
laid the foundation for understanding mandibular dynamics and occlusion.
Recording Method: The original recordings were
conducted outside of the mouth, which magnified the vertical dimension of
movement but did not accurately represent the horizontal dimension.
B. Modern Techniques
Digital Recording: Advances in technology have allowed
for the use of digital computer techniques to record mandibular motion in
real-time. This enables accurate measurement of movements in both vertical
and horizontal dimensions.
Reconstruction of Motion: Modern systems can compute
and visualize mandibular motion at multiple points simultaneously, providing
valuable insights for clinical applications.
2. Key Points of Reference
Three significant points of reference are particularly important in the study
of mandibular motion:
A. Incisor Point
Location: The incisor point is located on the midline
of the mandible at the junction of the facial surface of the mandibular
central incisors and the incisal edge.
Clinical Significance: This point is crucial for
assessing anterior guidance and incisal function during mandibular
movements.
B. Molar Point
Location: The molar point is defined as the tip of the
mesiofacial cusp of the mandibular first molar on a specified side.
Clinical Significance: The molar point is important for
evaluating occlusal relationships and the functional dynamics of the
posterior teeth during movement.
C. Condyle Point
Location: The condyle point refers to the center of
rotation of the mandibular condyle on the specified side.
Clinical Significance: Understanding the condyle point
is essential for analyzing the temporomandibular joint (TMJ) function and
the overall biomechanics of the mandible.
3. Clinical Implications
A. Occlusion and Function
Mandibular Motion: The capacity of motion of the
mandible affects occlusal relationships, functional movements, and the
overall health of the masticatory system.
Treatment Planning: Knowledge of mandibular motion is
critical for orthodontic treatment, prosthodontics, and restorative
dentistry, as it influences the design and placement of restorations and
appliances.
B. Diagnosis and Assessment
Evaluation of Movement: Clinicians can use the
principles established by Posselt to assess and diagnose issues related to
mandibular function, such as limitations in movement or discrepancies in
occlusion.