Dental Education and Materials Overview
8 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

ما هي المهمة الأساسية لتعليم طب الأسنان؟

توفير تعليم طب الأسنان الذي يركز على المتعلم والبحث العلمي المتطور والرعاية الصحية المتمحورة حول المريض والمشاركة المجتمعية ضمن ثقافة تنظيمية إيجابية.

أي من القيم الجوهرية التالية يتم تضمينها في تعليم طب الأسنان؟ (اختر جميع الخيارات المناسبة)

  • استغلال
  • احترام (correct)
  • ابتكار (correct)
  • نقص

يجب أن تكون المواد المستخدمة في نماذج الأسنان هشة.

False (B)

ما هو تعريف 'الطين' في مجال طب الأسنان؟

<p>نموذج لسن واحد، يتم تحضيره من انطباع.</p> Signup and view all the answers

أي من المواد التالية تصنف كمنتج جبس وفقًا لمواصفات ADA؟

<p>كل ما ذكر (A)</p> Signup and view all the answers

الجص عبارة عن __________.

<p>كبريتات الكالسيوم</p> Signup and view all the answers

ما هي الخصائص الميكانيكية المطلوبة لمواد النموذج والموت؟

<p>يجب أن تكون قوية لمقاومة الانكسار، صلبة لمقاومة الخدش، وقادرة على إنتاج تفاصيل دقيقة.</p> Signup and view all the answers

طابق الأنواع المختلفة من منتجات الجبس مع طرق تصنيعها:

<p>بلستر = وعاء مفتوح عند 120°C حجر الأسنان = تحت ضغط البخار في درجة حرارة 120°C الحجر عالي القوة = غلي في محلول CaCl2 بنسبة 30%</p> Signup and view all the answers

Flashcards

Dental Model

A positive replica of teeth and related jaw tissues, made from an impression.

Die

A model of a single tooth, made from an impression.

Working Cast

A model used for treatments that includes both models and dies.

Gypsum Products

Materials used to create dental models and dies, derived from calcium sulfate.

Signup and view all the flashcards

Mechanical Properties

Strength and hardness needed for model and die materials to withstand use without breakage or scratching.

Signup and view all the flashcards

Fine Details Reproduction

The ability of model/die materials to accurately capture the small details of an impression.

Signup and view all the flashcards

Dimensional Stability

Maintaining consistent size during setting and storage.

Signup and view all the flashcards

Compatibility with Impression Materials

No chemical reaction between model/die materials and the impression.

Signup and view all the flashcards

Color Contrast

Visually distinguishing the model/die from the rest of the material.

Signup and view all the flashcards

Ease of Use

How simple it is to work with and handle the material.

Signup and view all the flashcards

Plaster

Type of gypsum product, known for lower strength.

Signup and view all the flashcards

Dental Stone

Gypsum product with better strength than plaster, used often for models.

Signup and view all the flashcards

High-Strength Stone

Strongest type of gypsum product, used where high durability is needed.

Signup and view all the flashcards

Calcium Sulfate Hemihydrate

Chemical formula CaSO4. 1/2H2O; the primary component of most gypsum products found in dentistry.

Signup and view all the flashcards

W/P Ratio

Water-to-powder ratio used in gypsum product preparation which changes the properties of the hardening material.

Signup and view all the flashcards

Manufacturing Method

The process used for creating gypsum products by eliminating water, which affects particle sizes and shapes.

Signup and view all the flashcards

Study Notes

Vision and Mission

  • Vision: Shaping the future of Dentistry through excellence in dental education, innovative research, patient-centered care and health promotion internationally.
  • Mission: Providing learner-focused dental education, cutting-edge scientific research, patient-centered care, community engagement, all within a positive organizational culture.
  • Core Values: Leadership, Excellence, Innovation, Collaboration, Respect, Integrity.

Model and Die Materials

  • Cast: A positive replica of teeth and/or associated supporting soft and hard tissues.
  • Die: A model of a single tooth, prepared from an impression.
  • Model & Die Materials Requirements:
    • High strength to resist breakage during use.
    • Hard to use.
    • Ability to reproduce fine details of the impression.
    • Little dimensional change on setting, and remain dimensionally stable during storage.
    • Compatibility with impression materials (no interaction between the impression and model/die materials).
    • Good color contrast.
    • Ease of use.
    • Cheap.

Types of Gypsum Products

  • Gypsum Products: Pure gypsum products used in dentistry are classified as plaster, dental stone, and high-strength stone.
  • Chemical Composition: All gypsum products are chemically the same – calcium sulfate hemihydrate (CaSO₄·½H₂O).
  • Differences: They differ in manufacturing method, particle size, W/P ratio, and physical properties.
  • Manufacturing Methods:
    • Plaster: Open vessel at 120°C
    • Dental stone: Autoclave under steam pressure at 120°C
    • High-strength stone: Boiling in 30% CaCl₂ solution

Manipulation of Gypsum Products

  • Proportion P and L: (Details given in the document)
  • Bulk P: (Details given in the document)
  • Microstone: (Details given in the document)
  • Pre-packaged P: (Details given in the document)
  • Transfer to impression: (Details given in the document)

Setting Reaction of Gypsum

  • Reverse of Manufacturing: The setting reaction is the reverse of the manufacturing process.
  • Reaction: Calcium sulfate hemihydrate + Water →Calcium sulfate dihydrate + Heat

Mechanism of Setting (Crystalline Theory)

  • Dissolution: Some hemihydrate dissolves in water, forming Ca²⁺ and SO₄²⁻ ions.
  • Nucleation: These ions then form dihydrate nuclei for crystallization.
  • Crystal Growth: More dihydrate precipitates around these nuclei, leading to crystal growth until all hemihydrate is transformed into dihydrate.
  • Solubility Difference: Solubility of hemihydrate in water is higher than that of the formed dihydrate.
  • Super Saturation: Concentration of dihydrate increases rapidly, to create a super-saturated solution.

Water/Powder Ratio (W/P)

  • Theoretical Ratio: 100 g of hemihydrate requires 18.6 ml of water for complete hydration.
  • Practical Ratio: (Actual ratios varies for plaster, stone, improved stone.)
  • Importance: Excess water leads to porosity in the final product.

Setting Time

  • Definition: Time elapsed from mixing until hardening.
  • Divisions:
    • Mixing time: Duration from powder addition to water until a homogenous mix.
    • Working time (3 minutes): Time available for mixing and use before initial setting occurs.
    • Initial setting time (12 minutes): Period beginning mixing until partial setting; material is rigid but not hard.
    • Final setting time (Several hours): Complete setting occurs, resulting in hard and strong model/die.

Measuring Setting Time

  • Loss of Gloss: To determine proper working time; indicates partial setting.
  • Temperature Rise: Reaction is exothermic; implies setting.
  • Penetration Tests: Resistance of set gypsum to penetration by needles (Vicat & Gillmore needles) to measure setting time.

Control of Setting Time

  • Operator Factors:
    • W/P ratio: High W/P ratio results in less nuclei of crystallization and slow growth rate (retardation).
    • Mixing time and rate: More nuclei of crystallization and accelerated crystal growth.
    • Temperature:
      • 20-50°C: Accelerates setting.
      • Above 50°C: Retards setting.
      • 100°C: No reaction.
  • Manufacturer Factors:
    • Powder Fineness: Smaller particles increase wetting, dissolution rate, nuclei and crystal growth rate acceleration.
    • Impurities: Terra Alba as nucleating agents increases number of nuclei and accelerate crystal growth rate.
    • Chemicals (Retarders and Accelerators): Retarders (Borax, blood, saliva) coat hemihydrate and reduce solubility or coat growing crystals inhibiting crystal growth rate (retardation). Accelerators (2% K₂SO₄) accelerate dissolution, nuclei, and crystallization growth.

Properties of Gypsum Products

  • Dimensional Changes: Volumetric contraction (7%) during setting, but setting expansion is observed which is due to outward thrusting of growing crystals.
  • Porosity: Set gypsum is porous due to greater external volume than crystalline volume. Excess water remains in the pores.
  • Strength: Different strengths are noted:
    • Wet Strength (green strength) : Strength of gypsum during or immediately after hydration.
    • Dry Strength: Strength after water is removed.
  • Factors affecting strength:
    • W/P Ratio: Higher ratio results in more excess water leaving more pores and a weaker product.
    • Mixing Time & Rate: Overmixing leads to fracture and decreasing strength.
    • Chemicals: Chemicals impact crystal shape and decrease strength.
    • Gypsum Product Type: Improved stone > Dental stone > Plaster.

Surface Hardness and Abrasion Resistance

  • Surface Hardness: Typically low, making surfaces susceptible to scratches.
  • Resin (Polymer): Applying resin increases surface hardness and abrasion resistance.

Reproduction of Detail

  • Accuracy: Gypsum products do not accurately reproduce surface details.
  • Porosity: Porous microscopic surface of the set gypsum and air bubbles formed at the interface between the impression and gypsum casts.

Additional Notes

  • The impression should be washed before pouring the model to avoid any contaminants or foreign materials interfering with the reproducibility and strength of the model.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Model and Die Materials PDF

Description

يستكشف هذا الاختبار رؤية ومهمة التعليم في طب الأسنان، بالإضافة إلى المواد المستخدمة في نماذج الأسنان والأسباب وراء اختيارها. سيتعرف المشاركون على القيم الأساسية لهذا المجال الحيوي وخصائص المواد المناسبة لصنع النماذج. هذا الاختبار مهم لكل مهتم بالتعليم والبحث في طب الأسنان.

More Like This

Dental Terms Flashcards
24 questions

Dental Terms Flashcards

StylishPeach4517 avatar
StylishPeach4517
Genetics in Dental Education
50 questions

Genetics in Dental Education

FineLookingAquamarine248 avatar
FineLookingAquamarine248
Dentist-Patient Relationship Overview
10 questions
Use Quizgecko on...
Browser
Browser