NEET MDS Synopsis
Composite Cavity Preparation
Conservative DentistryComposite Cavity PreparationComposite cavity preparations are designed to optimize the placement and
retention of composite resin materials in restorative dentistry. There are three
basic designs for composite cavity preparations: Conventional, Beveled
Conventional, and Modified. Each design has specific characteristics and
indications based on the clinical situation.
1. Conventional Preparation DesignA. Characteristics
Design: Similar to cavity preparations for amalgam
restorations.
Shape: Box-like cavity with slight occlusal
convergence, flat floors, and undercuts in dentin.
Cavosurface Angle: Near 90° (butt joint), which
provides a strong interface for the restoration.
B. Indications
Moderate to Large Class I and Class II Restorations:
Suitable for larger cavities where significant tooth structure is missing.
Replacement of Existing Amalgam: When an existing
amalgam restoration needs to be replaced, a conventional preparation is
often indicated.
Class II Cavities Extending onto the Root: In cases
where the cavity extends onto the root, a conventional design is preferred
to ensure adequate retention and support.
2. Beveled Conventional PreparationA. Characteristics
Enamel Cavosurface Bevel: Incorporation of a bevel at
the enamel margin to increase surface area for bonding.
End-on-Etching: The bevel allows for more effective
etching of the enamel rods, enhancing adhesion.
Benefits:
Improves retention of the composite material.
Reduces microleakage at the restoration interface.
Strengthens the remaining tooth structure.
B. Preparation Technique
Bevel Preparation: The bevel is created using a
flame-shaped diamond instrument, approximately 0.5 mm wide and angled at 45°
to the external enamel surface.
C. Indications
Large Area Restorations: Ideal for restoring larger
areas of tooth structure.
Replacing Existing Restorations: Suitable for class
III, IV, and VI cavities where composite is used to replace older
restorations.
Rarely Used for Posterior Restorations: While
effective, this design is less commonly used for posterior teeth due to
aesthetic considerations.
3. Modified PreparationA. Characteristics
Depth of Preparation: Does not routinely extend into
dentin; the depth is determined by the extent of the carious lesion.
Wall Configuration: No specified wall configuration,
allowing for flexibility in design.
Conservation of Tooth Structure: Aims to conserve as
much tooth structure as possible while obtaining retention through
micro-mechanical means (acid etching).
Appearance: Often has a scooped-out appearance,
reflecting its conservative nature.
B. Indications
Small Cavitated Carious Lesions: Best suited for small
carious lesions that are surrounded by enamel.
Correcting Enamel Defects: Effective for addressing
minor enamel defects without extensive preparation.
C. Modified Preparation Designs
Class III (A and B): For anterior teeth, focusing on
small defects or carious lesions.
Class IV (C and D): For anterior teeth with larger
defects, ensuring minimal loss of healthy tooth structure.
Applegate's Classification for edentulous arches
ProsthodonticsApplegate's Classification is a system used to categorize edentulous
(toothless) arches in preparation for denture construction. The classification
is based on the amount and quality of the remaining alveolar ridge, the
relationship of the ridge to the residual ridges, and the presence of undercuts.
The system is primarily used in the context of complete denture prosthodontics
to determine the best approach for achieving retention, stability, and support
for the dentures.
Applegate's Classification for edentulous arches:
1. Class I: The alveolar ridge has a favorable arch form and sufficient height
and width to provide adequate support for a complete denture without the need
for extensive modifications. This is the ideal scenario for denture
construction.
2. Class II: The alveolar ridge has a favorable arch form but lacks the
necessary height or width to provide adequate support. This may require the use
of denture modifications such as flanges to enhance retention and support.
3. Class III: The ridge lacks both height and width, and there may be undercuts
or excessive resorption. In this case, additional procedures such as ridge
augmentation or the use of implants might be necessary to improve the foundation
for the denture.
4. Class IV: The ridge has an unfavorable arch form, often with significant
resorption, and may require extensive surgical procedures or adjuncts like
implants to achieve a functional and stable denture.
5. Class V: This is the most severe classification where the patient has no
residual alveolar ridge, possibly due to severe resorption, trauma, or surgical
removal. In such cases, the creation of a functional and stable denture may be
highly challenging and might necessitate advanced surgical procedures and/or the
use of alternative prosthetic options like over-dentures with implant support.
It's important to note that this classification is a guide, and individual
patient cases may present with a combination of features from different classes
or may require customized treatment plans based on unique anatomical and
functional requirements.
Pouring the Final Impression
Conservative DentistryPouring the Final Impression
Technique
Mixing Die Stone: A high-strength die stone is mixed
using a vacuum mechanical mixer to ensure a homogenous mixture without air
bubbles.
Pouring Process:
The die stone is poured into the impression using a vibrator and a
No. 7 spatula.
The first increments should be applied in small amounts, allowing
the material to flow into the remote corners and angles of the
preparation without trapping air.
Surface Tension-Reducing Agents: These agents can be
added to the die stone to enhance its flow properties, allowing it to
penetrate deep into the internal corners of the impression.
Final Dimensions
The impression should be filled sufficiently so that the dies will be
approximately 15 to 20 mm tall occluso-gingivally after trimming. This
height is important for the stability and accuracy of the final restoration.
Dentin
Dental Anatomy
Dentin
Composition: 70% inorganic, 20% organic, 10% water by weight and 45%, 33%, and 22% in volume respectively
Hydroxyapatite crystals and collagen type I
Physical characteristics: Harder than bone and softer than enamel
Yellow in color in normal teeth
Radiographic appearance: More radiolucent than enamel
Primary (circumpulpal) dentin: forms most of the tooth
Mantle dentin: first dentin to form; forms the outline of dentin in the adult tooth
Predentin: lines the innermost portion of dentin (faces the pulp)
Secondary dentin: after root formation dentin continues to form, continuous to primary dentin but with structural irregularities
Tertiary dentin: reactive or reparative dentin; may or may not have characteristics of primary dentin; produced in the area of an external stimulus; osteodentin
Dentin is formed by cells called odontoblasts.
These cells derive from the ectomesenchyme and produce the organic matrix that will calcify and become the dentin.
Formation of dentin initiates formation of enamel.
The formation of dentin starts during late bell-stage in the area of the future cusp.
First coronal dentin and then root dentin.
Completion of dentin does not occur until about 18 months after eruption of primary and 2-3 years after eruption of permanent teeth.
The rate of dentin development varies.
The role of the internal (inner) dental (enamel) epithelium
Cuboidal - Columnar (reverse polarization)
Ectomesenchymal cells of the dental papilla become preodontoblasts - odontoblasts
Acellular zone disappears
Histologic features of dentin
Odontoblasts
Dentinal tubules
Extend through the entire thickness of dentin
S-shaped (primary curvatures) path in the crown, less S-shaped in the root, almost straight in the cervical aspect
Secondary curvatures
Tubular microbranches
Presence of fluid
Intratubular dentin
Dentin in the tubule that is hypermineralized
The term peritubular dentin should not be used
Sclerotic dentin
Dentinal tubules that are occluded with calcified material
Most likely a physiologic response
Reduction of permeability of dentin
Intertubular dentin
Dentin between the tubules
Interglobular dentin
Areas of unmineralized or hypomineralized dentin
The defect affects mineralization and not the architecture of dentin
Incremental lines
Lines of von Ebner: lines associated with 5-day rythmic pattern of dentin deposition
Contour lines of Owen: Originally described by Owen they result from a coincidence of the secondary curvatures between neighboring dentinal tubules.
Granular Layer of Tomes
Seen only in ground sections in the root area covered by cementum
Originally, they were thought to be areas of hypomineralization
They are true spaces obtained by sections going through the looped terminal portions dentinal tubules
DE junction :Scalloped area
Enamel tissue with incremental lines of Retzius and dentin tissue with parallel, curved dentinal tubules are in contact at the irregular dentino-enamel junction. The junction often has a scalloped-shaped morphology
DC junction Dentin Cemental Junction
Eruption Gingivitis
Pedodontics
Eruption Gingivitis
Eruption gingivitis is a transitory form of gingivitis observed in young
children during the eruption of primary teeth. It is characterized by
localized inflammation of the gingiva that typically subsides once the
teeth have fully emerged into the oral cavity.
Characteristics
Age Group:
Eruption gingivitis is most commonly seen in young children,
particularly during the eruption of primary teeth. However, a
significant increase in the incidence of gingivitis is often noted in
the 6-7 year age group when permanent teeth begin to erupt.
Mechanism:
The increase in gingivitis during this period is attributed to several
factors:
Lack of Protection: During the early stages of active
eruption, the gingival margin does not receive protection from the
coronal contour of the tooth, making it more susceptible to
irritation and inflammation.
Food Impingement: The continual impingement of food on the
gingiva can exacerbate the inflammatory process, leading to gingival
irritation.
Contributing Factors
Accumulation of Debris:
Food debris, material alba, and bacterial plaque often accumulate around
and beneath the free gingival tissue. This accumulation can partially
cover the crown of the erupting tooth, contributing to inflammation.
Common Associations:
Eruption gingivitis is most frequently associated with the eruption of
the first and second permanent molars. The inflammation can be painful
and may lead to complications such as:
Pericoronitis: Inflammation of the soft tissue surrounding
the crown of a partially erupted tooth.
Pericoronal Abscess: A localized collection of pus in the
pericoronal area, which can result from the inflammatory process.
Clinical Management
Oral Hygiene:
Emphasizing the importance of good oral hygiene practices is crucial
during this period. Parents should be encouraged to assist their
children in maintaining proper brushing and flossing techniques to
minimize plaque accumulation.
Professional Care:
Regular dental check-ups are important to monitor the eruption process
and manage any signs of gingivitis or associated complications.
Professional cleanings may be necessary to remove plaque and debris.
Symptomatic Relief:
If the child experiences pain or discomfort, topical analgesics or
anti-inflammatory medications may be recommended to alleviate symptoms.
Gross Features of the Tongue
AnatomyGross Features of the Tongue
The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
The apex of the V is posterior and the two limbs diverge anteriorly.
The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.
Oral Part of the Tongue
This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.
On each side of the frenulum is a deep lingual vein, visible as a blue line.
It begins at the tip of the tongue and runs posteriorly.
All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.
On the dorsum of the oral part of the tongue is a median groove.
This groove represents the site of fusion of the distal tongue buds during embryonic development.
The Lingual Papillae and Taste Buds
The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
They are arranged in rows parallel to the sulcus terminalis.
The fungiform papillae are small and mushroom-shaped.
They usually appear are pink or red spots.
The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.
The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.
The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.
The Pharyngeal Part of the Tongue
This part lies posterior to the sulcus terminalis and palatoglossal arches.
Its mucous membrane has no papillae.
The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.
Str. Pneumoniae
General Pathology
Str. Pneumoniae
Probably the most important streptococci. Primary cause of pneumonia. Usually are diplococci. Ste. pneumoniae are α-hemolytic and nutritionally fastidious. Often are normal flora.
Key virulence factor is the capsule polysaccharide which prevents phagocytosis. Other virulence factors include pneumococcal surface protein and α-hemolysin.
Major disease is pneumonia, usually following a viral respiratory infection. Characterized by fever, cough, purulent sputum. Bacteria infiltrates alveoli. PMN’s fill alveoli, but don’t cause necrosis. Also can cause meningitis, otitis, sinusitis.
There are vaccines against the capsule polysaccharide. Resistance to penicillin, cephalosporins, erythromycins, and fluoroquinalones is increasing.
Benzylpenicillin (penicillin G)
Pharmacology
Benzylpenicillin (penicillin G)
Benzylpenicillin, commonly known as penicillin G, is the gold standard penicillin. Penicillin G is typically given by a parenteral route of administration because it is unstable to the hydrochloric acid of the stomach.
Indications :
bacterial endocarditis, meningitis, aspiration pneumonia, lung abscess,community-acquired pneumonia, syphilis, septicaemia in children