NEET MDS Synopsis
COMPOSITE RESINS -ACID ETCH TECHNIQUE
Dental Materials
ACID ETCH TECHNIQUE
Cavities requiring added retention (to hold firmly) are treated with an acid etching technique. This technique improves the seal of the composite resin to the cavity wall. The enamel adjacent to the margins of the preparation is slightly decalcified with a 40 to 50 percent phosphoric acid solution. This etched enamel enhances the mechanical retention of the composite resin. In addition, the acid etch technique is used to splint unstable teeth to adjacent teeth. The acid is left on the cut tooth structure only 15 seconds, in accordance with the directions for one common commercial brand. The area is then flushed with water for a minimum of 30 seconds to remove the decalcified material. Etched tooth structure will have a chalky appearance.
Cardiac Conditions and Prophylaxis for Bacterial Endocarditis
Oral and Maxillofacial SurgeryOverview of Infective Endocarditis (IE):
Infective endocarditis is an inflammation of the inner lining of the
heart, often caused by bacterial infection.
Certain cardiac conditions increase the risk of developing IE,
particularly during dental procedures that may introduce bacteria into the
bloodstream.
High-Risk Cardiac Conditions: Antibiotic prophylaxis is
recommended for patients with the following high-risk cardiac conditions:
Prosthetic cardiac valves
History of infective endocarditis
Cyanotic congenital heart disease
Surgically constructed systemic-pulmonary shunts
Other congenital heart defects
Acquired valvular dysfunction
Hypertrophic cardiomyopathy
Mitral valve prolapse with regurgitation
Moderate-Risk Cardiac Conditions:
Mitral valve prolapse without regurgitation
Previous rheumatic fever with valvular dysfunction
Negligible Risk Conditions:
Coronary bypass grafts
Physiological or functional heart murmurs
Prophylaxis Recommendations
When to Administer Prophylaxis:
Prophylaxis is indicated for dental procedures that involve:
Manipulation of gingival tissue
Perforation of the oral mucosa
Procedures that may cause bleeding
Antibiotic Regimens:
The standard prophylactic regimen is a single dose administered 30-60
minutes before the procedure:
Amoxicillin:
Adult dose: 2 g orally
Pediatric dose: 50 mg/kg orally (maximum 2 g)
Ampicillin:
Adult dose: 2 g IV/IM
Pediatric dose: 50 mg/kg IV/IM (maximum 2 g)
Clindamycin (for penicillin-allergic patients):
Adult dose: 600 mg orally
Pediatric dose: 20 mg/kg orally (maximum 600 mg)
Cephalexin (for penicillin-allergic patients):
Adult dose: 2 g orally
Pediatric dose: 50 mg/kg orally (maximum 2 g)
The Walls of the Orbit
AnatomyThe Walls of the Orbit
Each orbit has four walls: superior (roof), medial, inferior (floor) and lateral.
The medial walls of the orbit are almost parallel with each other and with the superior part of the nasal cavities separating them.
The lateral walls are approximately at right angles to each other
CLEANING AND PICKLING ALLOYS
Dental Materials
CLEANING AND PICKLING ALLOYS
The surface oxidation or other contamination of dental alloys is a troublesome occurrence. The oxidation of base metals in most alloys can be kept to a minimum or avoided by using a properly adjusted method of heating the alloy and a suitable amount of flux when melting the alloy . Despite these precautions, as the hot metal enters the mold, certain alloys tend to become contaminated on the surface by combining with the hot mold gases, reacting with investment ingredients, or physically including mold particles in the metal surface. The surface of most cast, soldered, or otherwise heated metal dental appliances is cleaned by warming the structure in suitable solutions, mechanical polishing, or other treatment of the alloy to restore the normal surface condition.
Surface tarnish or oxidation can be removed by the process of pickling. Castings of noble or high-noble metal may be cleaned in this manner by warming them in a 50% sulfuric acid and water solution . . After casting, the alloy (with sprue attached) is placed into the warmed pickling solution for a few seconds. The pickling solution will reduce oxides that have formed during casting. However, pickling will not eliminate a dark color caused by carbon deposition
The effect of the solution can be seen by comparing the submerged surfaces to those that have still not contacted the solution. the ordinary inorganic acid solutions and do not release poisonous gases on boiling (as sulfuric acid does). In either case, the casting to be cleaned is placed in a suitable porcelain beaker with the pickling solution and warmed gently, but short of the boiling point. After a few moments of heating, the alloy surface normally becomes bright as the oxides are reduced. When the heating is completed, the acid may be poured from the beaker into the original storage container and the casting is thoroughly rinsed with water. Periodically, the pickling solution should be replaced with fresh solution to avoid excessive contamination.
Precautions to be taken while pickling
With the diversity of compositions of casting alloys available today, it is prudent to follow the manufacturer's instructions for pickling precisely, as all pickling solutions may not be compatible with all alloys. Furthermore, the practice of dropping a red-hot casting into the pickling solution should beavoided. This practice may alter the phase structure of the alloy or warp thin castings, and splashing acid may be dangerous to the operator. Finally, steel or stainless steel tweezers should not be used to remove castings from the pickling solutions. The pickling solution may dissolve the tweezers and plate the component metals onto the casting. Rubber-coated or Teflon tweezers are recommended for this purpose.
The Occipital Bone
Anatomy-> This bone forms much of the base and posterior aspect of the skull.
-> It has a large opening called the foramen magnum, through which the cranial cavity communicates with the vertebral canal.
-> It is also where the spinal cord becomes continuous with the medulla (oblongata) of the brain stem.
-> The occipital bone is saucer-shaped and can be divided into four parts: a squamous part (squama), a basilar part (basioccipital part), and two lateral parts (condylar parts).
-> These four parts develop separately around the foramen magnum and unite at about the age of 6 years to form one bone.
-> On the inferior surfaces of the lateral parts of the occipital bone are occipital condyles, where the skull articulates with C1 vertebra (the atlas) at the atlanto-occipital joints.
-> The internal aspect of the squamous part of the occipital bone is divided into four fossae: the superior two for the occipital poles of the cerebral hemispheres, and the inferior two, called cerebellar fossae, for the cerebellar hemispheres.
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
Tracheostomy
General SurgeryTracheostomy
Tracheostomy is a surgical procedure that involves creating an opening in the
trachea (windpipe) to facilitate breathing. This procedure is typically
performed when there is a need for prolonged airway access, especially in cases
where the upper airway is obstructed or compromised. The incision is usually
made between the 2nd and 4th tracheal rings, as entry through the 1st ring can
lead to complications such as tracheal stenosis.
Indications
Tracheostomy may be indicated in various clinical scenarios, including:
Acute Upper Airway Obstruction: Conditions such as
severe allergic reactions, infections (e.g., epiglottitis), or trauma that
obstruct the airway.
Major Surgery: Procedures involving the mouth, pharynx,
or larynx that may compromise the airway.
Prolonged Mechanical Ventilation: Patients requiring
artificial ventilation for an extended period, such as those with
respiratory failure.
Unconscious Patients: Situations involving head
injuries, tetanus, or bulbar poliomyelitis where airway protection is
necessary.
Procedure
Technique
Incision: A horizontal incision is made in the skin
over the trachea, typically between the 2nd and 4th tracheal rings.
Dissection: The subcutaneous tissue and muscles are
dissected to expose the trachea.
Tracheal Entry: An incision is made in the trachea, and
a tracheostomy tube is inserted to maintain the airway.
Complications of Tracheostomy
Tracheostomy can be associated with several complications, which can be
categorized into intraoperative, early postoperative, and late postoperative
complications.
1. Intraoperative Complications
Hemorrhage: Bleeding can occur during the procedure,
particularly if major blood vessels are inadvertently injured.
Injury to Paratracheal Structures:
Carotid Artery: Injury can lead to significant
hemorrhage and potential airway compromise.
Recurrent Laryngeal Nerve: Damage can result in
vocal cord paralysis and hoarseness.
Esophagus: Injury can lead to tracheoesophageal
fistula formation.
Trachea: Improper technique can cause tracheal
injury.
2. Early Postoperative Complications
Apnea: Temporary cessation of breathing may occur,
especially in patients with pre-existing respiratory issues.
Hemorrhage: Postoperative bleeding can occur, requiring
surgical intervention.
Subcutaneous Emphysema: Air can escape into the
subcutaneous tissue, leading to swelling and discomfort.
Pneumomediastinum and Pneumothorax: Air can enter the
mediastinum or pleural space, leading to respiratory distress.
Infection: Risk of infection at the incision site or
within the tracheostomy tube.
3. Late Postoperative Complications
Difficult Decannulation: Challenges in removing the
tracheostomy tube due to airway swelling or other factors.
Tracheocutaneous Fistula: An abnormal connection
between the trachea and the skin, which may require surgical repair.
Tracheoesophageal Fistula: An abnormal connection
between the trachea and esophagus, leading to aspiration and feeding
difficulties.
Tracheoinnominate Arterial Fistula: A rare but
life-threatening complication where the trachea erodes into the innominate
artery, resulting in severe hemorrhage.
Tracheal Stenosis: Narrowing of the trachea due to scar
tissue formation, which can lead to breathing difficulties.
Ossification
Anatomy
Ossification
Intramembranous-found in the flat bones of the face
Mesenchymal cells cluster and form strands
Strands are cemented in a uniform network. Which is known as osteoid
Calcium salts are deposited; osteoid is converted to bone
Trabeculae are formed and make cancellous bone with open spaces known as marrow cavities
Periosteum forms on the inner and outer surfaces of the ossification centers
Surface bone becomes compact bone
Endochondral-primary type of ossification In the human