NEET MDS Lessons
Pedodontics
Transpalatal Arch
The transpalatal arch (TPA) is a fixed orthodontic appliance used primarily in the maxillary arch to maintain or regain space, particularly after the loss of a primary molar or in cases of unilateral space loss. It is designed to provide stability to the molars and prevent unwanted movement.
Indications
- Unilateral Loss of Space:
- The transpalatal arch is particularly effective in cases where there is unilateral loss of space. It helps maintain the position of the remaining molar and prevents mesial movement of the adjacent teeth.
- It can also be used to maintain the arch form and provide anchorage during orthodontic treatment.
Contraindications
- Bilateral Loss of Space:
- The use of a transpalatal arch is contraindicated in cases of bilateral loss of space. In such situations, the appliance may not provide adequate support or stability, and other treatment options may be more appropriate.
Limitations/Disadvantages
- Tipping of Molars:
- One of the primary limitations of the transpalatal arch is the potential for both molars to tip together. This tipping can occur if the arch is not properly designed or if there is insufficient anchorage.
- Tipping can lead to changes in occlusion and may require additional orthodontic intervention to correct.
Pit and Fissure Sealants
Pit and fissure sealants are preventive dental materials used to protect occlusal surfaces of teeth from caries by sealing the grooves and pits that are difficult to clean. According to Mitchell and Gordon (1990), sealants can be classified based on several criteria, including polymerization methods, resin systems, filler content, and color.
Classification of Pit and Fissure Sealants
1. Polymerization Methods
Sealants can be differentiated based on how they harden or polymerize:
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a) Self-Activation (Mixing Two Components)
- These sealants harden through a chemical reaction that occurs when two components are mixed together. This method does not require any external light source.
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b) Light Activation
- Sealants that require a light source to initiate the polymerization
process can be further categorized into generations:
- First Generation: Ultraviolet Light
- Utilizes UV light for curing, which can be less common due to safety concerns.
- Second Generation: Self-Cure
- These sealants harden through a chemical reaction without the need for light, similar to self-activating sealants.
- Third Generation: Visible Light
- Cured using visible light, which is more user-friendly and safer than UV light.
- Fourth Generation: Fluoride-Releasing
- These sealants not only provide a physical barrier but also release fluoride, which can help in remineralizing enamel and providing additional protection against caries.
- First Generation: Ultraviolet Light
- Sealants that require a light source to initiate the polymerization
process can be further categorized into generations:
2. Resin System
The type of resin used in sealants can also classify them:
- BIS-GMA (Bisphenol A Glycidyl Methacrylate)
- A commonly used resin that provides good mechanical properties and adhesion.
- Urethane Acrylate
- Offers enhanced flexibility and durability, making it suitable for areas subject to stress.
3. Filled and Unfilled
Sealants can be categorized based on the presence of fillers:
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Filled Sealants
- Contain added particles that enhance strength and wear resistance. They may provide better wear characteristics but can be more viscous and difficult to apply.
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Unfilled Sealants
- Typically have a smoother flow and are easier to apply, but may not be as durable as filled sealants.
4. Clear or Tinted
The color of the sealant can also influence its application:
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Clear Sealants
- Have better flow characteristics, allowing for easier penetration into pits and fissures. They are less visible, which can be a disadvantage in monitoring during follow-up visits.
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Tinted Sealants
- Easier for both patients and dentists to see, facilitating monitoring and assessment during recalls. However, they may have slightly different flow characteristics compared to clear sealants.
Application Process
- Sealants are applied in a viscous liquid state that enters the micropores of the tooth surface, which have been enlarged through acid conditioning.
- Once applied, the resin hardens due to either a self-hardening catalyst or the application of a light source.
- The extensions of the hardened resin that penetrate and fill the micropores are referred to as "tags," which help in retaining the sealant on the tooth surface.
Types of Crying
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Obstinate Cry:
- Characteristics: This cry is loud, high-pitched, and resembles a siren. It often accompanies temper tantrums, which may include kicking and biting.
- Emotional Response: It reflects the child's external response to anxiety and frustration.
- Physical Manifestation: Typically involves a lot of tears and convulsive sobbing, indicating a high level of distress.
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Frightened Cry:
- Characteristics: This cry is not about getting what the child wants; instead, it arises from fear that overwhelms the child's ability to reason.
- Physical Manifestation: Usually involves small whimpers, indicating a more subdued response compared to the obstinate cry.
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Hurt Cry:
- Characteristics: This cry is a reaction to physical discomfort or pain.
- Physical Manifestation: It may start with a single tear that runs down the child's cheek without any accompanying sound or resistance, indicating a more internalized response to pain.
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Compensatory Cry
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Characteristics:
- This type of cry is not a traditional cry; rather, it is a sound that the child makes in response to a specific stimulus, such as the sound of a dental drill.
- It is characterized by a constant whining noise rather than the typical crying sounds associated with distress.
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Physical Manifestation:
- There are no tears or sobs associated with this cry. The child does not exhibit the typical signs of emotional distress that accompany other types of crying.
- The sound is directly linked to the presence of the stimulus (e.g., the drill). When the stimulus stops, the whining also ceases.
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Emotional Response:
- The compensatory cry may indicate a child's attempt to cope with discomfort or fear in a situation where they feel powerless or anxious. It serves as a way for the child to express their discomfort without engaging in more overt forms of crying.
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Classification of Oral Habits
Oral habits can be classified based on various criteria, including their nature, impact, and the underlying motivations for the behavior. Below is a detailed classification of oral habits:
1. Based on Nature of the Habit
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Obsessive Habits (Deep Rooted):
- International or Meaningful:
- Examples: Nail biting, digit sucking, lip biting.
- Masochistic (Self-Inflicting):
- Examples: Gingival stripping (damaging the gums).
- Unintentional (Empty):
- Examples: Abnormal pillowing, chin propping.
- International or Meaningful:
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Non-Obsessive Habits (Easily Learned and Dropped):
- Functional Habits:
- Examples: Mouth breathing, tongue thrusting, bruxism (teeth grinding).
- Functional Habits:
2. Based on Impact
- Useful Habits:
- Habits that may have a positive or neutral effect on oral health.
- Harmful Habits:
- Habits that can lead to dental issues, such as malocclusion, gingival damage, or tooth wear.
3. Based on Author Classifications
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James (1923):
- a) Useful Habits
- b) Harmful Habits
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Kingsley (1958):
- a) Functional Oral Habits
- b) Muscular Habits
- c) Combined Habits
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Morris and Bohanna (1969):
- a) Pressure Habits
- b) Non-Pressure Habits
- c) Biting Habits
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Klein (1971):
- a) Empty Habits
- b) Meaningful Habits
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Finn (1987):
- I. a) Compulsive Habits
- b) Non-Compulsive Habits
- II. a) Primary Habits
4. Based on Functionality
- Functional Habits:
- Habits that serve a purpose, such as aiding in speech or feeding.
- Dysfunctional Habits:
- Habits that disrupt normal oral function or lead to negative consequences.
Anomalies of Number: problems in initiation stage
Hypodontia: 6% incidence; usually autosomal dominant (50% chance of passing to children) with variable expressivity (e.g., parent has mild while child has severe); most common missing permanent tooth (excluding 3rd molars) is Md 2nd premolar, 2nd most common is X lateral; oligodontia (at least 6 missing), and anodontia
1. Clincial implications: can interfere with function, lack of teeth → ↓ alveolar bone formation, esthetics, hard to replace in young children, implants only after growth completed, severe cases should receive genetic and systemic evaluation to see if other problems
2. Syndromes with hypodontia: Rieger syndrome, incontinentia pigmenti, Kabuki syndrome, Ellis-van Creveld syndrome, epidermolysis bullosa junctionalis, and ectodermal dysplasia (usually X-linked; sparse hair, unable to sweat, dysplastic nails)
Supernumerary teeth: aka hyperdontia; mesiodens when located in palatal midline; occur sporadically or as part of syndrome, common in cleft cases; delayed eruption often a sign that supernumeraries are preventing normal eruption
1. Multiple supernumerary teeth: cleidocranial dysplasia/dysostosis, Down’s, Apert, and Crouzon syndromes, etc.
Anomalies of Size: problems in morphodifferentiation stage
Microdontia: most commonly peg laterals; also in Down’s syndrome, hemifacial microsomia
Macrodontia: may be associated with hemifacial hypertrophy
Fusion: more common in primary dentition; union of two developing teeth
Gemination: more common in primary; incomplete division of single tooth bud → bifid crown, one pulp chamber; clinically distinguish from fusion by counting geminated tooth as one and have normal # teeth present (not in fusion)
Anomalies of Shape: errors during morphodifferentiation stage
Dens evaginatus: extra cusp in central groove/cingulum; fracture can → pulp exposure; most common in Orientals
Dens in dente: invagination of inner enamel epithelium → appearance of tooth within a tooth
Taurodontism: failure of Hertwig’s epithelial root sheath to invaginate to proper level → elongated (deep) pulp chamber, stunted roots; sporadic or associated with syndrome (e.g., amelogenesis imperfecta, Trichodento-osseous syndrome, ectodermal dysplasia)
Conical teeth: often associated with ectodermal dysplasia
Anomalies of Structure: problems during histodifferentiation, apposition, and mineralization stages
Dentinogenesis imperfecta: problem during histodifferentiation where defective dentin matrix → disorganized and atubular circumpulpal dentin; autosomal dominant inheritance; three types, one occurs with osteogenesis imperfecta (brittle bone syndrome); not sensitive despite exposed dentin; primary dentition has bulbous crowns, obliterated pulp chambers, bluish-grey or brownish-yellow teeth that are easily worn; permanent teeth often stained but can be sound
Amelogenesis imperfecta: heritable defect, independent from metabolic, syndromes, or systemic conditions (though similar defects seen with syndromes or environmental insults); four main types (hypoplastic, hypocalcified, hypomaturation, hypoplastic/hypomaturation with taurodontism); proper treatment addresses sensitivity, esthetics, VDO, caries and gingivitis prevention
Enamel hypoplasia: quantitative defect of enamel from problems in apposition stage; localized (caused by trauma) or generalized (caused by infection, metabolic disease, malnutrition, or hereditary disorders) effects; more common in malnourished children; least commonly Md incisors affected, often 1st molars; more susceptible to caries, excessive wearing → lost VDO, esthetic problems, and sensitivity to hot/cold
Enamel hypocalcification: during calcification stage
Fluorosis: excess F ingestion during calcification stage → intrinsic stain, mottled appearance, or brown staining and pitting; mild, moderate, or severe; porous enamel soaks up external stain
Salivary Factors and Their Mechanisms
1. Buffering Factors
Buffering factors in saliva help maintain a neutral pH in the oral cavity, which is vital for preventing demineralization of tooth enamel.
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HCO3 (Bicarbonate)
- Effects on Mineralization: Acts as a primary buffer in saliva, helping to neutralize acids produced by bacteria.
- Role in Raising Saliva or Plaque pH: Increases pH by neutralizing acids, thus promoting a more favorable environment for remineralization.
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Urea
- Effects on Mineralization: Releases ammonia (NH3) when metabolized, which can help raise pH and promote mineralization.
- Role in Raising Saliva or Plaque pH: Contributes to pH elevation through ammonia production.
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Arginine-rich Proteins
- Effects on Mineralization: Releases ammonia, which can help neutralize acids and promote remineralization.
- Role in Raising Saliva or Plaque pH: Increases pH through ammonia release, creating a less acidic environment.
2. Antibacterial Factors
Saliva contains several antibacterial components that help control the growth of pathogenic bacteria associated with dental caries.
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Lactoferrin
- Effects on Bacteria: Binds to iron, which is essential for bacterial growth, thereby inhibiting bacterial proliferation.
- Effects on Bacterial Aggregation or Adherence: May promote clearance of bacteria through aggregation.
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Lysozyme
- Effects on Bacteria: Hydrolyzes cell wall polysaccharides of bacteria, leading to cell lysis and death.
- Effects on Bacterial Aggregation or Adherence: Can indirectly promote clearance by breaking down bacterial cell walls.
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Peroxidase
- Effects on Bacteria: Produces hypothiocyanate (OSCN), which inhibits glycolysis in bacteria, reducing their energy supply.
- Effects on Bacterial Aggregation or Adherence: May help in the aggregation of bacteria, facilitating their clearance.
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Secretory IgA
- Effects on Bacteria: Neutralizes bacterial toxins and enzymes, reducing their pathogenicity.
- Effects on Bacterial Aggregation or Adherence: Binds to bacterial surfaces, preventing adherence to oral tissues.
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Alpha Amylase
- Effects on Bacteria: Produces glucose and maltose, which can serve as energy sources for some bacteria.
- Effects on Bacterial Aggregation or Adherence: Indirectly promotes bacterial aggregation through the production of glucans.
3. Factors Affecting Mineralization
Certain salivary proteins play a role in the mineralization process and the maintenance of tooth enamel.
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Histatins
- Effects on Mineralization: Bind to hydroxyapatite, aiding in the supersaturation of saliva, which is essential for remineralization.
- Effects on Bacteria: Some inhibition of mutans streptococci, which are key contributors to caries.
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Proline-rich Proteins
- Effects on Mineralization: Bind to hydroxyapatite, aiding in saliva supersaturation.
- Effects on Bacteria: Promote adherence of some oral bacteria.
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Cystatins
- Effects on Mineralization: Bind to hydroxyapatite, aiding in saliva supersaturation.
- Effects on Bacteria: Promote adherence of some oral bacteria.
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Statherin
- Effects on Mineralization: Bind to hydroxyapatite, aiding in saliva supersaturation.
- Effects on Bacteria: Promote adherence of some oral bacteria.
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Mucins
- Effects on Mineralization: Provide a physical and chemical barrier in the enamel pellicle, protecting against demineralization.
- Effects on Bacteria: Facilitate aggregation and clearance of oral bacteria.