NEET MDS Synopsis
AGE CHANGES of the Periodontal Ligament (PDL)
Dental Anatomy
AGE CHANGES
Progressive apical migration of the dentogingival junction.
Toothbrush abrasion of the area can expose dentin that can cause root caries and tooth mobility.
Histology of the alveolar bone
Near the end of the 2nd month of fetal life, mandible and maxilla form a groove that is opened toward the surface of the oral cavity.
As tooth germs start to develop, bony septa form gradually. The alveolar process starts developing strictly during tooth eruption.
The alveolar process is the bone that contains the sockets (alveoli) for the teeth and consists of
a) outer cortical plates
b) a central spongiosa and
c) bone lining the alveolus (bundle bone)
The alveolar crest is found 1.5-2.0 mm below the level of the CEJ.
If you draw a line connecting the CE junctions of adjacent teeth, this line should be parallel to the alveolar crest. If the line is not parallel, then there is high probability of periodontal disease.
Bundle Bone
The bundle bone provides attachment to the periodontal ligament fibers. It is perforated by many foramina that transmit nerves and vessels (cribiform plate). Embedded within the bone are the extrinsic fiber bundles of the PDL mineralized only at the periphery. Radiographically, the bundle bone is the lamina dura. The lining of the alveolus is fairly smooth in the young but rougher in the adults.
Clinical considerations
Resorption and regeneration of alveolar bone
This process can occur during orthodontic movement of teeth. Bone is resorbed on the side of pressure and opposed on the site of tension.
Osteoporosis
Osteoporosis of the alveolar process can be caused by inactivity of tooth that does not have an antagonist
Indirect Pulp Capping
Pedodontics
Indirect Pulp Capping
Indirect pulp capping is a dental procedure designed to treat teeth with deep
carious lesions that are close to the pulp but do not exhibit pulp exposure. The
goal of this treatment is to preserve the vitality of the pulp while allowing
for the formation of secondary dentin, which can help protect the pulp from
further injury and infection.
Procedure Overview
Initial Appointment:
During the first appointment, the dentist excavates all superficial carious
dentin. However, any dentin that is affected but not infected (i.e., it is
still healthy enough to maintain pulp vitality) is left intact if it is
close to the pulp. This is crucial because leaving a thin layer of affected
dentin can help protect the pulp from exposure and further damage.
Pulp Dressing:
After the excavation, a pulp dressing is placed over the remaining affected
dentin. Common materials used for this dressing include:
Calcium Hydroxide: Promotes the formation of
secondary dentin and has antibacterial properties.
Glass Ionomer Materials: Provide a good seal and
release fluoride, which can help in remineralization.
Hybrid Ionomer Materials: Combine properties of
both glass ionomer and resin-based materials.
The tooth is then sealed temporarily, and the patient is scheduled for a
follow-up appointment, typically within 6 to 12 months.
Second Appointment:
At the second appointment, the dentist removes the temporary restoration and
excavates any remaining carious material. The floor of the cavity is
carefully examined for any signs of pulp exposure. If no exposure is found
and the tooth has remained asymptomatic, the treatment is deemed successful.
Permanent Restoration:
If the pulp is intact, a permanent restoration is placed. The materials used
for the final restoration can vary based on the tooth's location and the
clinical situation. Options include:
For Primary Dentition: Glass ionomer, hybrid
ionomer, composite, compomer, amalgam, or stainless steel crowns.
For Permanent Dentition: Composite, amalgam,
stainless steel crowns, or cast crowns.
Indications for Indirect Pulp Capping
Indirect pulp capping is indicated when the following conditions are met:
Absence of Prolonged Pain: The tooth should not have a
history of prolonged or repeated episodes of pain, such as unprovoked
toothaches.
No Radiographic Evidence of Pulp Exposure: Preoperative
X-rays must not show any carious penetration into the pulp chamber.
Absence of Pathology: There should be no evidence of
furcal or periapical pathology. It is essential to assess whether the root
ends are completely closed and to check for any pathological changes,
especially in anterior teeth.
No Percussive Symptoms: The tooth should not exhibit
any symptoms upon percussion.
Evaluation and Restoration After Indirect Pulp Therapy
After the indirect pulp therapy, the following evaluations are crucial:
Absence of Subjective Complaints: The patient should
report no toothaches or discomfort.
Radiographic Evaluation: After 6 to 12 months,
periapical and bitewing X-rays should show deposition of new secondary
dentin, indicating that the pulp is healthy and responding well to
treatment.
Final Restoration: If no pulp exposure is observed
after the removal of the temporary restoration and any remaining soft
dentin, a permanent restoration can be placed.
PFM Alloys
Dental Materials
PFM Alloys
Applications-substructures for porcelain-fused-to-metal crowns and bridges
Classification
o High-gold alloys
o Palladium-silver alloys
o Nickel-chromium alloys
Structure
Composition
o High-gold alloys are 98% gold. platinum. And palladium
o Palladium-silver alloys are 50% to 60% palladium and 30 to 40% silver
o Nickel-chromium alloys are 70% to 80% nickel and 15% chromium with other metals
Manipulation
o Must have melting temperatures above that of porcelains to be bonded to their surface
o More difficult to cast (see section on chromium alloys)
Properties - Physical
Except for high-gold alloys, others are less dense alloys
Alloys are designed to have low thermal expansion coefficients that must be matched to the overlying porcelain
Chemical-high-gold alloys are immune, but others passivate
Mechanical-high modulus and hardness
MECHANISM OF HORMONE ACTION
Physiology
Hormones are carried by the blood throughout the entire body, yet they affect only certain cells. The specific cells that respond to a given hormone have receptor sites for that hormone.
This is sort of a lock and key mechanism. If the key fits the lock, then the door will open. If a hormone fits the receptor site, then there will be an effect. If a hormone and a receptor site do not match, then there is no reaction. All of the cells that have receptor sites for a given hormone make up the target tissue for that hormone. In some cases, the target tissue is localized in a single gland or organ. In other cases, the target tissue is diffuse and scattered throughout the body so that many areas are affected.
Hormones bring about their characteristic effects on target cells by modifying cellular activity. Cells in a target tissue have receptor sites for specific hormones. Receptor sites may be located on the surface of the cell membrane or in the interior of the cell.
In general those protein hormones are unable to diffuse through the cell membrane and react with receptor sites on the surface of the cell. The hormone receptor reaction on the cell membrane activates an enzyme within the membrane, called adenyl cyclase, which diffuses into the cytoplasm. Within the cell, adenyl cyclase catalyzes or starts the process of removal of phosphates from ATP to produce cyclic adenosine monophosphate or c AMP. This c AMP activates enzymes within the cytoplasm that alter or change the cellular activity. The protein hormone, which reacts at the cell membrane, is called the first messenger. c Amp that brings about the action attributed to the hormone is called the second messenger. This type of action is relatively rapid because the precursors are already present and they just needed to be activated in some way.
Connective Tissue
Anatomy
Connective Tissue
Functions of Connective tissue:
→ joins together other tissues
→ supporting framework for the body (bone)
→ fat stores energy
→ blood transports substances
Connective tissue is usually characterized by large amounts of extracellular materials that separate cells from each other, whereas epithelial tissue is mostly cells with very little extracellular material. The extracellular substance of connective tissue consists of protein fibers which are embedded in ground substance containing tissue fluid.
Fibers in connective tissue can be divided into three types:
→ Collagen fibers are the most abundant protein fibers in the body.
→ Elastic fibers are made of elastin and have the ability to recoil to original shape.
→ Reticular fibers are very fine collagen fibers that join connective tissues to other tissues.
Connective tissue cells are named according to their functions:
→ Blast cells produce the matrix of connective tissues
→ Cyte cells maintains the matrix of connective tissues
→ Clast cells breaks down the matrix for remodeling (found in bone)
Characteristics of Facilitated Diffusion & Active Transport
PhysiologyCharacteristics of Facilitated Diffusion & Active Transport - both require the use of carriers that are specific to particular substances (that is, each type of carrier can 'carry' one type of substance) and both can exhibit saturation (movement across a membrane is limited by number of carriers & the speed with which they move materials
BradyKinin
Pharmacology
BradyKinin
An endogenous vasodilator occurring in blood vessel walls.
At least two distinct receptor types, B1 and B2, appear to exist for BradyKinin
Roles of bradykinin:
1) Mediator of inflammation and pain.
2) Regulation of microcirculation.
3) Their production is interrelated with clotting and fibrinolysin systems.
4) Responsible for circulatory change after birth.
5) Involved in shock and some immune reactions.
Infections caused by gonorrhea
General Pathology
Infections caused by gonorrhea
1. Acute urethritis. Mostly in males. Generally self-limiting. Dysuria and purulent discharge.
2. Endocervical infection. Purulent vaginal discharge, abnormal menses, pelvic pain. Often co-infection with other STD’s. Some women are asymptomatic.
3. Pelvic Inflammatory Disease (PID). Consequence of ascending endocervical infection. Causes salpingitis, endometriosis, bilateral abdominal pain, discharge, fever. May lead to sterility, chronic pain, and ectopic pregnancy because of loss of fallopian cilia.
4. Anorectal inflammation. Mostly in homosexual men. Pain, itching, discharge from anus.
5. Dermatitis/arthritis. Occurs after bacteremia. Skin will have papules on an erythematous base which develop into necrotic pustules. Asymmetric joint pain. These infections are susceptible to penicillin.
6. Neonatal infections. Ophthalmia neonatorum is a conjunctival infection from going through infected vagina. After one year of age, suspect child abuse.