Single tooth anatomy

Page 1

Increasing Surface Energy

  • How to increase surface energy:

    • Acid Etching

  • Application of Phosphoric Acid:

    • To increase surface energy of the tooth.

  • Achieving Low Surface Tension:

    • Use of low molecular weight monomer, resulting in a more fluid adhesive.

  • Organic Component in Enamel:

    • Contains 1% organic material to help manage cracks on the tooth surface.

  • Dentin Composition:

    • High in organic components, mainly collagen.

    • Aging of collagen causes teeth to turn yellow.

  • Phosphoric Acid Application:

    • 60 seconds application shows no change compared to 30 seconds.

  • Optimal Phosphoric Acid Application on different surfaces:

    • Best on buccal enamel for orthodontic brackets.

    • Weaker bonding in Class II (dentin-rich) and Class V (cervical enamel) areas due to moisture and structural differences.

  • Adhesion Types:

    • Micromechanical adhesion to enamel.

  • Adhesive Compatibility:

    • Adhesive and composite (containing Bis-GMA) must be chemically compatible and hydrophobic.

  • Bonding Strength Comparison:

    • Better in Class IV restorations (incisal edge) due to thicker enamel than in Class V restorations (cervical area).

  • Usage of Rubber Dam:

    • To avoid moisture during bonding; moisture prevents proper polymerization.

  • Bonding in Dentin:

    • Easier in superficial dentin compared to deeper dentin due to less moisture.

Adhesion Types

  • Ochemical Adhesion:

    • Includes physical, chemical, and mechanical properties.

  • Clinical Failures:

    • Caused by issues such as cohesion failure or adhesion inadequacy leading to gap formation and restoration staining.

  • Organic Composition of Enamel:

    • 96% inorganic (hydroxyapatite), 3% water, 1% organic material.

  • Loss of Bonding Strength:

    • With age, organic proportion increases, leading to reduced bonding strength.

  • Application of Phosphoric Acid:

    • Etches enamel and creates micromechanical retention.

  • Aprismatic Enamel:

    • Requires sand blasting with aluminum oxide for retention if phosphoric acid is insufficient.

Page 2

Dentin Considerations

  • Bonding Strength:

    • Easier in superficial dentin than deep dentin due to larger tubules and moisture.

  • Smear Layer:

    • Protective covering of dentin tubules, significant for bonding considerations.

    • Composed of:

      • Smear-on layer (superficial)

      • Smear plug layer (covers tubule entries).

  • Issues with Smear Layer Removal:

    • Leaving it can lead to restorations breaking due to improper bonding.

  • Hybrid Layer:

    • Formed when the adhesive infiltrates and replaces the smear layer, allowing for better bonding.

    • Thicker when using a two-bottle adhesive system.

  • Role of Solvent in Adhesives:

    • Facilitates infiltration of collagen fibers; ethanol is the most common solvent.

  • Adhesives for Dentin and Enamel:

    • Not necessary to use separate adhesives for each.

Page 3

Decay and Preparation Techniques

  • Gingival Contact Removal:

    • Essential for thorough decay removal.

  • Gingival Floor Planing:

    • To eliminate unsupported enamel rods.

  • Drying After Primer Application:

    • Required to evaporate alcohol solvent.

  • Moisture Control Techniques:

    • Use of self-etching systems to facilitate bonding.

  • Etching Time Control:

    • Dentin is prone to over-etching; self-etching aids control.

  • MMP Activation Control:

    • Self-etching helps manage activation of collagen-degrading enzymes.

  • Total Etch vs. Self-Etch:

    • Total Etch: Apply for 20 seconds, then dry; Self-Etch: Apply with microbrush for 30 seconds.

  • Selectively Etching Enamel:

    • Solves the problem of poor enamel bonding from self-etching adhesives.

Page 4

Composite Composition

  • Inorganic Components of Composites:

    • Composed of various fillers.

  • Ideal Filler Content:

    • Higher filler content enhances performance; 100% filler results in a ceramic material.

  • Silane:

    • A bifunctional monomer crucial for composite interactions.

  • Common Initiator and Activator:

    • Camphorquinone is the most common initiator, activated by blue curing light (470 nm wavelength).

  • Composite Types:

    • Microhybrid and nanohybrid composites offer strength and polishability.

    • Nanofilled composites show clinical results similar to microhybrids.

  • Composite Layering and Shrinkage Control:

    • Apply composite in layers to mitigate shrinkage, ideally in 2 mm increments.

Page 5

Managing Composite Shrinkage

  • Factors Affecting Shrinkage:

    • Size of monomers, filler content, and type of composite (flowable vs packable).

  • Clinician's Shrinkage Control Techniques:

    • Volume of resin, C-factor control, light intensity adjustments, and using low-shrinkage resins.

  • Recommended Layer Thickness:

    • 2 mm layers recommended to achieve effective light penetration and shrinkage control.

  • Understanding C-factor:

    • The ratio of bonded to unbonded surfaces impacts shrinkage risk.

  • Curing Light Requirements:

    • Minimum intensity of 450 mW/cm² needed to polymerize composite effectively.

  • Impact of Polymerization Speed on Shrinkage:

    • Slower polymerization generates less shrinkage, supported by lower intensity settings on curing lights.

Page 6

Material Properties and Polymerization

  • Material Types:

    • Weak: Composites

    • Strong: Metals, ceramics

    • Ductile vs Brittle: Ductile materials deform before breaking; brittle materials do not.

    • Flexible vs Stiff: Flowable composites are flexible while others are stiff.

  • Post-Curing Adjustments:

    • Resin polishing typically occurs immediately post-placement despite ongoing polymerization.

Chemical Aggressions to Teeth

  • Types of Chemical Challenges:

    • Caries, dental adhesives, low-pH beverages, gastric acid.

  • Erosion Identification:

    • Gastric acid erosion noted on lingual tooth surfaces.

Physical and Mechanical Aggressions

  • Common Physical Aggressions:

    • High-speed drills and curing lights.

  • Mechanical Aggressions:

    • Attrition and abrasion.

  • Patient Age Factor:

    • Older patients generally present more protective opportunities than younger ones.

  • Glass Ionomer Cement (GIC) Basics:

    • Composed of polyacrylic acid and glass silicate, offering chemical adhesion due to polyacrylic acid.

Page 7

Caries Management

  • Initial Caries Removal:

    • Begin from the periphery to ensure complete decay elimination.