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Questions and Answers
What type of reaction do glass ionomer materials (GIC) undergo during setting?
What type of reaction do glass ionomer materials (GIC) undergo during setting?
Which of the following is considered a direct restorative material?
Which of the following is considered a direct restorative material?
In the Bronsted-Lowry definition, what role does a base play?
In the Bronsted-Lowry definition, what role does a base play?
What best describes the pH level of blood?
What best describes the pH level of blood?
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Which material is not typically categorized under surgical materials?
Which material is not typically categorized under surgical materials?
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What is one of the primary setting reactions in dental cements?
What is one of the primary setting reactions in dental cements?
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Which dental material is often used for making mouth guards?
Which dental material is often used for making mouth guards?
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What pH value is critical for demineralization of hydroxyapatite?
What pH value is critical for demineralization of hydroxyapatite?
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Which classification involves dental cements that utilize acid-base reactions?
Which classification involves dental cements that utilize acid-base reactions?
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What is the primary buffer system that helps maintain the blood plasma pH around 7.4?
What is the primary buffer system that helps maintain the blood plasma pH around 7.4?
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Which of the following statements about the composition of enamels is correct?
Which of the following statements about the composition of enamels is correct?
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Which buffer system is considered the secondary buffer in unstimulated saliva?
Which buffer system is considered the secondary buffer in unstimulated saliva?
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At which pH range is the phosphate buffer effective for salivary buffering?
At which pH range is the phosphate buffer effective for salivary buffering?
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Which of the following is NOT an acidic functional group required for a molecule to be classified as an organic acid?
Which of the following is NOT an acidic functional group required for a molecule to be classified as an organic acid?
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What is the role of A/B equilibria in relation to drugs?
What is the role of A/B equilibria in relation to drugs?
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What is the solubility product (Ksp) used for?
What is the solubility product (Ksp) used for?
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Which amino acid is mentioned as having an ionizable side chain that contributes to protein buffering?
Which amino acid is mentioned as having an ionizable side chain that contributes to protein buffering?
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Which chemical component accounts for 35% of the plaque buffer's composition?
Which chemical component accounts for 35% of the plaque buffer's composition?
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What is the optimal buffer ratio for achieving the best buffering capacity?
What is the optimal buffer ratio for achieving the best buffering capacity?
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What happens to a tooth when the pH of the surrounding fluid phase is lower than 4.5-5.5?
What happens to a tooth when the pH of the surrounding fluid phase is lower than 4.5-5.5?
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Which statement best describes the critical pH in relation to mineral saturation?
Which statement best describes the critical pH in relation to mineral saturation?
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What is one mechanism by which fluoride enhances the stability of teeth?
What is one mechanism by which fluoride enhances the stability of teeth?
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How does fluoride act when present during active caries development?
How does fluoride act when present during active caries development?
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Which process is significantly influenced by intermolecular forces in dental materials?
Which process is significantly influenced by intermolecular forces in dental materials?
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What role do CaF2 globules play in fluoride's mechanism of action?
What role do CaF2 globules play in fluoride's mechanism of action?
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Which property of fluoride is crucial in inhibiting demineralization during the active stages of caries?
Which property of fluoride is crucial in inhibiting demineralization during the active stages of caries?
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What is the primary reason for fluoride’s strong attraction to calcium ions?
What is the primary reason for fluoride’s strong attraction to calcium ions?
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In the context of electronegativity, which statement is accurate?
In the context of electronegativity, which statement is accurate?
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What is the primary function of the oval foramen in the fetal heart?
What is the primary function of the oval foramen in the fetal heart?
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Which structure prevents the tricuspid and bicuspid valves from inverting under pressure?
Which structure prevents the tricuspid and bicuspid valves from inverting under pressure?
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Where do all veins of the coronary sinus ultimately drain?
Where do all veins of the coronary sinus ultimately drain?
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What happens to the semilunar valves during ventricular relaxation?
What happens to the semilunar valves during ventricular relaxation?
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Which nerve passes posterior to the lung root in relation to the heart?
Which nerve passes posterior to the lung root in relation to the heart?
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What is the role of the coronary arteries?
What is the role of the coronary arteries?
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Which statement about strong electrolytes is true?
Which statement about strong electrolytes is true?
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What characterizes a weak acid compared to a strong acid?
What characterizes a weak acid compared to a strong acid?
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In a buffer solution, how is the pH primarily controlled?
In a buffer solution, how is the pH primarily controlled?
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Which of the following acids is classified as a strong acid?
Which of the following acids is classified as a strong acid?
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What is the key role of a buffer in a solution?
What is the key role of a buffer in a solution?
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What is a characteristic of non-electrolytes?
What is a characteristic of non-electrolytes?
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Which of the following best describes amphiprotic substances?
Which of the following best describes amphiprotic substances?
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What is the consequence of using weak acids in dental etching?
What is the consequence of using weak acids in dental etching?
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How are pKa and acid strength related?
How are pKa and acid strength related?
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Which of the following describes weak electrolytes accurately?
Which of the following describes weak electrolytes accurately?
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Study Notes
Dental Biomaterials
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Dental biomaterials encompass the study of materials used in dentistry, focusing on their composition, properties, manipulation, chemical reactions, mechanisms of action, clinical applications, and indications/contraindications.
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Applications include:
- Preventive and protective materials: Mouthguards, often made from polymers (resin).
- Polymer composites: Used as resin composites.
- Orthodontics: Utilizing polymers, metal alloys, and polymer composites.
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Restorative materials:
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Direct:
- Metal alloys
- Resin composites
- Glass ionomers
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Indirect (fixed and removable):
- Polymers
- Metal alloys
- Resin composites
- Ceramics
- Hybrid materials
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Direct:
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Impression materials: Typically polymer composites.
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Dental model materials: Consisting of gypsum and polymers.
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Root canal materials: Include metal alloys, polymers, polymer composites, and mineral aggregates.
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Surgical materials: Employing metal alloys, polymers, polymer composites, mineral aggregates, and biological materials.
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Implants: Constructed from metal alloys, polymers, polymer composites, and ceramics.
Direct Restorative Materials
- Resin composites: Polymerized through chemical or light activation.
- Glass ionomer materials (GIC): Set by cross-linking and gelation reactions.
- Amalgam: Results from the reaction of mercury with metal elements.
pH in Dentistry
- pH plays a crucial role in dental caries, affecting the demineralization and remineralization of hydroxyapatite.
- Critical pH is the pH value at which demineralization occurs.
- pH of blood: Maintained within a narrow range of 7.35-7.45.
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pH affects:
- Drug absorption
- Drug activity
- Drug partitioning
Dental Cements
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Dental cements are used to fix a tooth to a prosthesis, often employed as temporary fillings.
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Classification:
- Polymerization
- Acid-base cements
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Types: Zinc phosphate, zinc oxide eugenol, zinc polycarboxylate, and glass ionomer cements.
Brønsted-Lowry Theory
- Acid: Proton (H+) donor.
- Base: Proton acceptor.
Electrolyte Classification
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Electrolytes: Solutes that conduct electricity in solution.
- Strong electrolytes: Completely dissociate into ions, excellent conductors (e.g., ionic compounds).
- Weak electrolytes: Partially dissociate into ions, poor conductors (e.g., some covalent compounds).
- Non-electrolytes: Do not dissociate, do not conduct electricity (e.g., non-polar covalent compounds).
Neutralization Reaction
- Formation of water (weak electrolyte) drives the reaction forward.
- General reaction: Acid + Base → Water + Salt
Weak Acids in Dentistry
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Etchants: Used to prepare surfaces for bonding, enhancing bond strength.
- Enamel and dentin etchants
- Ceramic etchants
- Cements: Acid-base reaction plays a role in their setting.
Buffer Solutions
- Buffer: A solution that resists changes in pH upon addition of small amounts of acid or base ("pH shock absorber").
- Composition: A weak acid and its conjugate base.
- pH Control: By adjusting the relative concentrations of the weak acid and its conjugate base.
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Buffer capacity: The ability of the buffer to resist pH changes.
- Concentration: Higher concentration = greater capacity.
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Buffer ratio: [base]/[acid].
- Optimal buffering occurs at a ratio of 1.
- Effective range: 0.1-10.
Common Buffers
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Carbonic acid/Bicarbonate buffer:
- Maintains blood plasma pH at 7.4 (7.35-7.45).
- Primary buffer system in blood and stimulated saliva.
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Phosphate buffer:
- Secondary buffer in unstimulated saliva.
- Important for buffering salivary pH (5.1-8).
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Protein buffers:
- Buffer cells and blood plasma using carboxylic acid and amine groups.
- Contribute to salivary buffering (pH 3.4-5).
Organic Acids
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Criteria: Organic molecules must contain an acidic functional group to be considered acids.
- Examples of functional groups: Carboxylic acid (CO2H), sulphonic acid (SO3H), phosphoric acid (PO3H2), phenolic OH (Ar-OH).
Acid-Base Equilibria and Drugs
- Solubility: A/B equilibria explain drug solubility vs. pH.
- Stability: A/B equilibria explain drug stability vs. pH, determining susceptibility to degradation by acidic or basic attacks.
- Uptake Mechanism: A/B equilibria help understand uptake mechanisms for certain drugs.
Tooth Enamel
- Composition: 96% mineral by weight, 4% water and proteins (amelogenin, enamelin).
- Major mineral: Calcium phosphate, primarily hydroxyapatite (Ca10(PO4)6(OH)2).
Demineralization/Remineralization
- Dental caries is a dynamic process, altering enamel structure in response to chemical/biochemical changes.
- Plaque buffer: A complex mixture containing phosphate, bicarbonate, proteins, and organic acids.
Solubility Product (Ksp)
- Definition: A special equilibrium constant that predicts whether an ionic compound will precipitate from a solution based on known ion concentrations.
- Ion product (Q): The product of ion concentrations in solution at any given time.
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Ksp: The ion product at saturation, representing the maximum solubility of the compound.
- Q > Ksp: Precipitation occurs.
- Q < Ksp: No precipitation, solution is unsaturated.
Tooth Dissolution
- Critical pH: The pH value at which a solution is saturated with respect to a particular mineral.
- Dissolution: Occurs when solution pH < critical pH, leading to undersaturation and mineral dissolution.
- Remineralization: Occurs when solution pH > critical pH, leading to supersaturation and mineral precipitation.
- Saliva and Plaque: Typically supersaturated with calcium, phosphate, and hydroxide ions, preventing tooth dissolution.
Fluoride
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Effect: Fluoride substitutes for hydroxide ions in enamel defects, strengthening the crystal structure and reducing dissolution rate.
- FAP-like material: A fluorhydroxyapatite formed with fluoride incorporation.
- Caries Inhibition: Fluoride primarily works by inhibiting demineralization at the enamel-plaque interface.
Fluoride Mechanisms
- Plaque matrix: Concentrates fluoride from saliva due to electrostatic attraction.
- CaF2 formation: Fluoride binds to calcium ions to form calcium fluoride globules, acting as a fluoride reservoir.
- FAP formation: Fluoride released during acidification contributes to the formation of FAP-like veneer on the enamel surface.
Fluoride and Remineralization
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Mechanisms:
- Inhibition of demineralization: Low fluoride concentrations (1-50 ppm) reduce dissolution.
- Enhancement of mineralization: Formation of FAP-like material on the crystal surface, facilitated by CaF2 globules.
- Nucleation: Partially demineralized crystals act as nucleators, attracting fluoride, calcium, and phosphate ions for FAP formation.
- Inhibition of enolase: An enzyme involved in carbohydrate metabolism.
Intermolecular Forces
- Importance: Crucial for liquid flow (viscosity), surface wetting, and capillary action in dental materials.
- Types: Weak forces acting between molecules (electrostatic).
- Factors Influenced: Viscosity and surface energy.
- Impact: Affect liquid flow, surface wetting, and capillary action.
Polarity
- Electronegativity: The ability of an atom to attract shared electrons in a covalent bond.
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Polarity: Determined by the difference in electronegativity between atoms in a bond.
- Polar molecules: Uneven electron distribution, creating partial charges.
- Non-polar molecules: Even electron distribution, no partial charges.
- Impact: Affects intermolecular forces and material properties.
Heart Anatomy
- Atria: Thin-walled collecting chambers, divided into right and left atria.
- Oval Foramen (Fossa ovalis): A flap in the septum between the atria, allowing blood to flow from right to left atrium during fetal development and closing after birth.
- Papillary muscles: Muscles within the ventricles that connect to chordae tendineae, preventing valve prolapse.
Heart Valves
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Cuspid valves: Located between atria and ventricles, preventing backflow of blood.
- Tricuspid valve: Right atrioventricular valve, with three cusps.
- Bicuspid (mitral) valve: Left atrioventricular valve, with two cusps.
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Semilunar valves: Located between ventricles and major arteries, preventing backflow of blood.
- Pulmonary valve: Between the right ventricle and pulmonary artery.
- Aortic valve: Between the left ventricle and aorta.
Heart Orientation
- Right border: Right atrium.
- Base: Posterior surface, formed by both atria.
- Left border: Left ventricle.
- Apex: Anterior inferior point, located at the left ventricle, near the midclavicular line.
Coronary Arteries
- Supply: Deliver oxygenated blood to the heart muscle.
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Right coronary artery:
- Sinu-atrial nodal branch: Supplies the sinoatrial node (pacemaker of the heart).
- Right marginal branch: Supplies the right ventricle.
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Left coronary artery:
- Anterior interventricular branch (left anterior descending): Supplies the anterior and inferior portions of both ventricles and the interventricular septum.
- Circumflex branch: Supplies the left atrium and posterior portion of the left ventricle.
- Left marginal branch: Supplies the left ventricle.
Coronary Veins
- Drainage: Carry deoxygenated blood from the heart muscle.
- Coronary sinus: The main vein that collects blood from the heart muscle and drains into the right atrium.
- Other veins: Smaller veins that drain into the coronary sinus or directly into the right atrium.
Mediastinum
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Superior mediastinum: The space between the lungs and the heart.
- Right and left internal thoracic arteries: Supplies the anterior chest wall.
Nerve Relations
- Phrenic nerves (C3, C4, C5): Run anterior to the lung root, controlling the diaphragm.
- Vagus nerves: Run posterior to the lung root, involved in parasympathetic innervation.
- Relationship to heart chambers: Important for understanding the innervation of the heart.
Thoracic Duct
- Lymphatic system: Carries lymph fluid throughout the body, collecting waste and immune cells.
- Origin: Upper aspect of the cisterna chyli, passing out of the abdomen through the aortic hiatus.
- Path: Ascends through the chest, collecting lymph from the lower body, left upper body, and left side of the head and neck.
- Drainage: Drains into the left subclavian vein at the junction with the left internal jugular vein.
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Test your knowledge on dental biomaterials, focusing on their properties, applications, and various types used in dentistry. This quiz will cover preventive, restorative, and impression materials and their clinical uses. Perfect for anyone studying or working in the dental field.
