NEET MDS Synopsis
Events in gastric function
PhysiologyEvents in gastric function:
1) Signals from vagus nerve begin gastric secretion in cephalic phase.
2) Physical contact by food triggers release of pepsinogen and H+ in gastric phase.
3) Muscle contraction churns and liquefies chyme and builds pressure toward pyloric sphincter.
4) Gastrin is released into the blood by cells in the pylorus. Gastrin reinforces the other stimuli and acts as a positive feedback mechanism for secretion and motility.
5) The intestinal phase begins when acid chyme enters the duodenum. First more gastrin secretion causes more acid secretion and motility in the stomach.
6) Low pH inhibits gastrin secretion and causes the release of enterogastrones such as GIP into the blood, and causes the enterogastric reflex. These events stop stomach emptying and allow time for digestion in the duodenum before gastrin release again stimulates the stomach.
Bile
PhysiologyBile contains:
bile acids. These amphiphilic steroids emulsify ingested fat. The hydrophobic portion of the steroid dissolves in the fat while the negatively-charged side chain interacts with water molecules. The mutual repulsion of these negatively-charged droplets keeps them from coalescing. Thus large globules of fat (liquid at body temperature) are emulsified into tiny droplets (about 1 µm in diameter) that can be more easily digested and absorbed.
bile pigments. These are the products of the breakdown of hemoglobin removed by the liver from old red blood cells. The brownish color of the bile pigments imparts the characteristic brown color of the feces.
Gingiva
Dental Anatomy
Gingiva
The connection between the gingiva and the tooth is called the dentogingival junction. This junction has three epithelial types: gingival, sulcular, and junctional epithelium. These three types form from a mass of epithelial cells known as the epithelial cuff between the tooth and the mouth.
Much about gingival formation is not fully understood, but it is known that hemidesmosomes form between the gingival epithelium and the tooth and are responsible for the primary epithelial attachment. Hemidesmosomes provide anchorage between cells through small filament-like structures provided by the remnants of ameloblasts. Once this occurs, junctional epithelium forms from reduced enamel epithelium, one of the products of the enamel organ, and divides rapidly. This results in the perpetually increasing size of the junctional epithelial layer and the isolation of the remenants of ameloblasts from any source of nutrition. As the ameloblasts degenerate, a gingival sulcus is created.
Roseola
General Pathology
Roseola
- alias exanthem subitum; caused by Herpes virus type 6.
- children 6 months to 2 years old; spring and fall; incubation 10-15 days.
- sudden onset of a high fever with absence of physical findings; febrile convulsions are particularly common.
- fever falls by crisis on the 3rd or 4th day → 48 hours after temperature returns to normal macular or maculopapular rash starting on the trunk and spreading centrifugally.
Full Mucoperiosteal Flap Design in Periradicular Surgery
EndodonticsA full mucoperiosteal flap is a critical component in periradicular surgery,
allowing access to the underlying bone and root structures for effective
treatment. This flap design includes the surface mucosa, submucosa, and
periosteum, providing adequate visibility and access to the surgical site.
Here’s a detailed overview of the flap design, its types, and considerations in
periradicular surgery.
Key Components of Full Mucoperiosteal Flap
Surface Mucosa:
The outermost layer that is reflected during the flap procedure.
Submucosa:
The layer beneath the mucosa that contains connective tissue and
blood vessels.
Periosteum:
A dense layer of vascular connective tissue that covers the outer
surface of bones, providing a source of blood supply during healing.
Flap Design Types
Two-Sided (Triangular) Flap:
Description: Created with a horizontal
intrasulcular incision and a vertical relieving incision.
Indications: Commonly used for anterior teeth.
Advantages: Provides good access while preserving
the interdental papilla.
Drawbacks: May be challenging to re-approximate the
tissue.
Three-Sided (Rectangular) Flap:
Description: Involves a horizontal intrasulcular
incision and two vertical relieving incisions.
Indications: Used for posterior teeth.
Advantages: Increases surgical access to the root
surface.
Drawbacks: Difficult to re-approximate the tissue
and may lead to scarring.
Envelope Flap:
Description: A horizontal intrasulcular incision
without vertical relieving incisions.
Indications: Provides access to the buccal aspect
of the tooth.
Advantages: Minimally invasive and preserves more
tissue.
Drawbacks: Limited access to the root surface.
Surgical Procedure Steps
Local Anesthesia:
Administer local anesthesia to ensure patient comfort during the
procedure.
Incision:
Make a horizontal intrasulcular incision along the gingival margin,
followed by vertical relieving incisions as needed.
Flap Reflection:
Carefully reflect the flap to expose the underlying bone and root
structures.
Bone Removal and Curettage:
Remove any bone or granulation tissue as necessary to access the
root surface.
Apicectomy and Retrograde Filling:
Perform apicectomy if indicated and prepare the root end for
retrograde filling.
Flap Re-approximation:
Re-approximate the flap and secure it with sutures to promote
healing.
Postoperative Care:
Provide instructions for postoperative care, including the use of
ice packs and gauze to control bleeding.
Considerations
Haemostasis:
Achieving and maintaining haemostasis is crucial for optimal
visualization and healing. Techniques include the use of local
anesthetics with vasoconstrictors and topical hemostatic agents.
Tissue Preservation:
Care should be taken to preserve as much tissue as possible to
enhance healing and minimize scarring.
Postoperative Monitoring:
Monitor the surgical site for signs of infection or complications
during the healing process.
Limited Mucoperiosteal Flap Design in Periradicular Surgery
Limited mucoperiosteal flaps are essential in periradicular surgery,
particularly for accessing the root surfaces while minimizing trauma to the
surrounding tissues. This flap design is characterized by specific incisions and
techniques that aim to enhance surgical visibility and access while promoting
better healing outcomes.
Limited Mucoperiosteal Flaps
Definition: Limited mucoperiosteal flaps involve
incisions that do not include marginal or interdental tissues, focusing on
preserving the integrity of the surrounding soft tissues.
Purpose: These flaps are designed to provide access to
the root surfaces for procedures such as apicoectomy, root resection, or
treatment of periapical lesions.
Types of Limited Mucoperiosteal Flaps
Submarginal Horizontal Incision
Description: A horizontal incision made in the
attached gingiva, avoiding the marginal gingiva.
Advantages: Preserves the marginal tissue, reducing
the risk of gingival recession and scarring.
Semilunar Flap
Description: A curved incision that begins in the
alveolar mucosa, dips into the attached gingiva, and returns to the
alveolar mucosa.
Advantages: Provides access while minimizing trauma
to the marginal tissue; however, it has poor healing potential and may
lead to scarring.
Scalloped (Ochsenbein-Luebke) Flap
Description: Similar to the rectangular flap but
with a scalloped horizontal incision in the attached gingiva.
Advantages: Follows the contour of the gingival
margins, preserving aesthetics but is also prone to delayed healing and
scarring.
Surgical Technique
Incision: The flap is initiated with a careful incision
in the attached gingiva, ensuring that the marginal tissue remains intact.
Reflection: The flap is gently reflected to expose the
underlying bone and root surfaces, allowing for the necessary surgical
procedures.
Irrigation and Closure: After the procedure, the area
should be well-irrigated to prevent infection, and the flap is
re-approximated and sutured in place.
Clinical Considerations
Healing Potential: Limited mucoperiosteal flaps
generally have better healing potential compared to full mucoperiosteal
flaps, as they preserve more of the surrounding tissue.
Aesthetic Outcomes: These flaps are particularly
beneficial in aesthetic zones, as they minimize the risk of visible scarring
and gingival recession.
Postoperative Care: Proper postoperative care,
including the use of ice packs and digital pressure on gauze, is essential
to control bleeding and promote healing.
Drawbacks
Limited Access: While these flaps minimize trauma, they
may provide limited access to the root surfaces, which can be a disadvantage
in complex cases.
Healing Complications: Although they generally promote
better healing, there is still a risk of complications such as delayed
healing or scarring, particularly with semilunar and scalloped designs.
Conclusion
Limited mucoperiosteal flap designs are valuable in periradicular surgery,
offering a balance between surgical access and preservation of surrounding
tissues. Understanding the various types of flaps and their applications can
significantly enhance the outcomes of endodontic surgical procedures. Proper
technique and postoperative care are crucial for achieving optimal healing and
aesthetic results.
Gingival Seat in Class II Restorations
Conservative DentistryGingival Seat in Class II Restorations
The gingival seat is a critical component of Class II restorations,
particularly in ensuring proper adaptation and retention of the restorative
material. This guide outlines the key considerations for the gingival seat in
Class II restorations, including its extension, clearance, beveling, and wall
placement.
1. Extension of the Gingival Seat
A. Apical Extension
Apical to Proximal Contact or Caries: The gingival seat
should extend apically to the proximal contact point or the extent of
caries, whichever is greater. This ensures that all carious tissue is
removed and that the restoration has adequate retention.
2. Clearance from Adjacent Tooth
A. Clearance Requirement
Adjacent Tooth Clearance: The gingival seat should
clear the adjacent tooth by approximately 0.5 mm. This clearance is
essential to prevent damage to the adjacent tooth and to allow for proper
adaptation of the restorative material.
3. Beveling of the Gingival Margin
A. Bevel Angles
Amalgam Restorations: For amalgam restorations, the
gingival margin is typically beveled at an angle of 15-20 degrees. This
bevel helps to improve the adaptation of the amalgam and reduce the risk of
marginal failure.
Cast Restorations: For cast restorations, the gingival
margin is beveled at a steeper angle of 30-40 degrees. This angle enhances
the strength of the margin and provides better retention for the cast
material.
B. Contraindications for Beveling
Root Surface Location: If the gingival seat is located
on the root surface, beveling is contraindicated. This is to maintain the
integrity of the root surface and avoid compromising the periodontal
attachment.
4. Wall Placement
A. Facial and Lingual Walls
Extension of Walls: The facial and lingual walls of the
proximal box should be extended such that they clear the adjacent tooth by
0.2-0.3 mm. This clearance helps to ensure that the restoration does not
impinge on the adjacent tooth and allows for proper contouring of the
restoration.
B. Embrasure Placement
Placement in Embrasures: The facial and lingual walls
should be positioned in their respective embrasures. This placement helps to
optimize the aesthetics and function of the restoration while providing
adequate support.
The Frontal Bone
Anatomy- The forehead is formed by the smooth, broad, convex plate of bone called the frontal squama.
- In foetal skulls, the halves of the frontal squama are divided by a metopic suture.
- In most people, the halves of the frontal bone begin to fuse during infancy and the suture between is usually not visible after 6 years of age.
- The frontal bone forms the thin roof of the orbits (eye sockets).
- Just superior to and parallel with each supraorbital margin is a bony ridge, the superciliary arch, which overlies the frontal sinus. This arch is more pronounced in males.
- Between these arches there is a gently, rounded, medial elevation called the gabella; this term derives from the Latin word glabellus meaning smooth and hairless. In most people, the skin over the gabella is hairless.
-The slight prominences of the forehead on each side, superior to the superciliary arches, are called frontal eminences (tubers).
- The supraorbital foramen (occasionally a notch), which transmits the supraorbital vessels and nerve is located in the medial part of the supraorbital margin.
- The frontal bone articulates with the two parietal bones at the coronal suture.
-It also articulates with the nasal bones at the frontonasal suture. At the point where this suture crosses the internasal suture in the medial plane, there is an anthropological landmark called the nasion . The depression is located at the root of the nose, where it joins the cranium.
- The frontal bone also articulates with the zygomatic, lacrimal, ethmoid, and sphenoid bones.
In about 8% of adult skulls, a remnant of the inferior part of the metopic (interfrontal) suture is visible. It may be mistaken in radiographs for a fracture line by inexperienced observers.
- The superciliary arches are relatively sharp ridges of bone and a blow to them may lacerate the skin and cause bleeding.
- Bruising of the skin over a superciliary arch causes tissue fluid and blood to accumulate in the surrounding connective tissue, which gravitates into the upper eyelid and around the eye. This results in swelling and a "black eye".
- Compression of the supraorbital nerve as it emerges from its foramen causes considerable pain, a fact that may be used by anaesthesiologists and anaesthetists to determine the depth of anaesthesia and by physicians attempting to arouse a moribund patient.
Herpes simplex
General Pathology
Herpes simplex is subdivided into type 1 and 2, the former usually developing lesions around the lips and mouth and the latter producing vesicular lesions in the genital region
- contracted by physical contact; incubation 2-10 days.
- primary HSV I usually is accompanied by systemic signs of fever and Lymphadenopathy, while recurrent herpes is not associate with systemic signs.
- dentists often become infected by contact with patient saliva and often develop extremely painful infections on the fingers (herpetic whitlow).
- Herpes viruses remain dormant in sensory ganglia and are reactivated by stress, sunlight, menses, etc.
- Herpes gingivostomatitis is MC primary HSV 1 infectionÆpainful, vesicular eruptions that may extend for the tongue to the retropharynx.
- Herpes keratoconjunctivitis (HSV 1)
- Kaposi's varicelliform eruption refers to an HSV 1 infection superimposed on a previous dermatitis, usually in an immunodeficient person.
- laboratory: culture; ELISA test on vesicle fluid; intranuclear inclusions within multinucleated squamous cells in scrapings (Tzanck preps) of vesicular lesions.