dental materials ch. 2- oral environment and patient considerations 1/16/2025

Oral environment and patient considerations

Dental Biomaterials

  • placed and used within oral cavity so must be

    • biocompatible

    • durable

Oral Environment

  • produces many limitations to both the physical and mechanical properties of dental materials

  • Dental material must be compatible in an environment of moister, stresses, temperatures, acid levels

Dental materials

  1. preventative/therapeutic- help prevent disease or trauma; might have therapeutic action on the teeth or oral tissues. {pit and fissure sealants, mouth guards, mouth rinse, toothpaste, fluoride}

  2. restorative- repair or replace tooth structure. Can be direct or indirect

    1. Direct restoration- placed immediately and directly into a prepared tooth in a malleable state that then sets to harden (can be done in single visit)

    2. Indirect restoration- involves customized tooth replacements that require fabrication outside of mouth (like in lab) usually requires a second appointment to fir and cement the restoration

  3. Auxiliary- used to fabricate and maintain restorations

Biocompatibility- materials used in oral cavity must not impede or adversely affect any other tissues; must be safe for us;

  • what’s the function of a dental material depend on ?

    • properties of the material as w

Force

  • matierals must be able to withstand a varying degree of force or load throu

    • Compression force- crushing biting forces; posterior teeth are ideally s

    • Tensile force- applied in opposite directions to stretch an

    • Shearing force- 2 surfaces slide against each other in opposite directions

    • Torsion or Torque- twisting force that has tensile and compressive forces; more descriptive of normal masticatoru evemts

Stress

  • when force is exerted on tooth or material, the tooth creates resistance to counteract the force

  • the internal force which resists the applied force is called stress

    • if the stress within the object can’t resist the force it will defore and cause strain on the tooth

  • Flexural stress- bending stress; combination of tension and compression. if stress exerted over large area, tooth structures can more likely handle the stress, but if its over small area, the increase in pressure may result in fracture

  • repeated stresses may make microscopic fflaws that grow over time which cause a fracture- fatigue failure

Moisture and Acid levels

  • oral cavity always in contacat with moisture.

  • can vary from acid to alkaline

  • depends on bacteria biofilm they have

  • normal resting pH of saliva:

_ desired materials should have low solubility (

Corrosion- deterioration or dissolution of the metal in response to a chemical attack or in an electr

Metals like steel can’t be used in oral cavity bc it breaks down becoming rust

when steel is coated first with a barrier the barrier gives steel its stainless quality- it won’t rust

Galvanism

  • an environment containing moisture, acidity, and dissimilar metals makes the generation of an electric current possible; this is the phenomenon of electric current being transmitted between two dissimilar metals (seen in amalgam restorations)

  • the salts of the saliva facilitate the movement of something something

  • it’s like a shock

Temperature

  • With few exceptions, all forms of matter expand when they are heated and contract when cooled, resulting in dimensional change

    • we need materials that expand and contract similar to the rate our tooth structures expand and contract

    • if material is placed in cavity restoration, and it expands and gets bigger than tooth it can fracture tooth. If material contracts more than tooth structure, the margins of the filling will loosen and pull away from the margins and the tooth and yuh

  • Coefficient of Thermal Expansion (CTE)- measurement of change in volume or length in relationship to change in temperature

  • percolation- repeated shrinkage and expansion of dental material

  • thermal conductivity- rate which heat flows through material over time

    • poor thermal conductor- feels temp but (heat) doesn’t spread

    • good thermal conductor- heat spreads

Retention- it’s ability to maintain its position without displacement under stress

  • mechanical- use of undercut or other projections into which material is locked in place; once material is hardened in place, it’s retained through its design. Can no longer be used when significant amounts of tooth structure is removed

  • Chemical adhesion- commonly called dental cements; contact the two? together

  • bonding- describes retention of materials; creates microscopic pores in dentin and mechanically lock into tooth structure (I missed SO much here oops) think velcro! This offers several advantages in producing retention. Less removal of tooth structure, stronger retentive force,

  • Most of todays materials use combo of mechanical and chemical or bonding

  • something else

  • Depends on several factors [wetting, viscosity, etc']

    • wetting- degree which liquid adhesive is able to spread over surface of tooth and restprative material. the material needs to spread out over the tooth, shouldn’t bead!

    • Viscosity- surace roughness will increase the wetting of the surface by the liquid. high viscosity= thicker so we want something with lower viscosity

    • Film thickness- the minimal thickness obtainable by a layer of a matieral particularly important in working with dental cements

    • Surface characteristics- cleanliness of surface, moisture contam, surfaace texture, and something else

  • Microleakage- surface between walls of the tooth structure and the restoration is called the interface. if the interface isn’t sealed, there’s a slight space there and fluids and microorganisms can seep in there the seepage is called microleakage.

Esthetics-

  • three components of color

    • Hue-

    • Chroma- intensity of color

    • Value- how light/dark

  • color of teeth determined by amt of light that passes through them

    • transparent

    • opaque- light is completely absorbed by the object

    • usually both of these processes occur reflecting light to carious degrees and giving

Detection of restorative materials

  • obvious ID

    • difficult ID

    • Tactile eval- feel for any margins

    • visual eval

    • radiographic eval