Biomaterials- Chapter 2

therapeutic materials

• used to treat disease

• for short periods of time

• ex. sealants, fluorides

restorative materials

• used to reconstruct tooth structure

• expected to remain for indefinite lengths of time

• we want to last for years

patient concerns

• concerns, questions, and demands must play a part in the decision process

• ex. cost (silver cheaper than gold), how will it look

preventative/ therapeutic

• materials are used to prevent disease or trauma

restorative materials

• used to repair or replace tooth structure lost to disease or trauma

classifications of dental materials

• preventative/therapeutic

• restorative materials

biocompatibility: chart

• must benefit patient

• must not adversely affect living tissue

• adverse responses: postoperative sensitivity, toxicity and hypersensitivity

• some materials may be therapeutic in small quantities or in contact w tissues for short periods of time, but also may be irritating to soft tissues with longer contact or in larger doses

biocompatibility: types

• postoperative sensitivity common

• patients adverse response

postoperative sensitivity common

• may occur from toxicity of the restorative, preventative, or threptic material or bacterial invasion

patients adverse response

• patients allergic to some metals, particularly nickel- crown, margins, lips from ortho appliances, attached gingiva from metal framework

• composites may discolor- what would cause this?

• medical history important

force

• is a push, pull, or twist applied to a material

stress

• force applied at the surface level creates

force, stress, strain order

• force creates - stress, if change- creates strain

tensile force

• “pull apart”

• force applied at each end of a material in opposite directions to stretch an object or pull it apart

• different foods=different chewing

compressive force

• push together

• force applied to compress or squeeze an object

• crushing bite forces

shearing force

• force applied when 2 surfaces slide against each other in opposite directions

  • anterior teeth biting into food, used for cutting

torsion or torque

• twisting force that has tensile & compressive forces

  • normal masticatory events

stress & strain

• when force is exerted on a tooth or restorative material, the tooth or materials creates stress to resist the force

stress

• amount of force

• amount of force exerted from within an object to resist an external force

strain

• the amount of change

• the amount of change that the force has produced in the object

flexural stress

• bending stress

• caused by- combination of tension and compression

fatigue failure

• a fracture resulting from repeated stresses that produce microscopic flaws that grow

types of moisture in the oral cavity

• foods

• saliva

• blood

normal ph of saliva

• 6.2 to 7.0

• (neutral)

soluble material dissolves in fluid

• materials should have low solubility- not susceptible to being dissolved in a solvent

effects of moisture

• gold & porcelain retain better bc they are insoluble compared to composites that are more soluble

corrosion

• (has to be replaced)

• the deterioration or dissolving of the metal in response to a chemical attack

• exceptions- noble metals (gold and platinum)

• amalgams are susceptible to corrosion causing marginal breakdowns and discoloration of the tooth

tarnish

• (doesn’t have to be replaced)

• limited to the surface

• is a discoloration resulting from oxidation of a thin layer of metal at its surface

• not as destructive as corrosion

how long after drinking acid does it stay in ur mouth

• 20 mins after u stop drinking

galvanism

• environment containing moisture, electrolytes, and dissimilar metals make the generation of electrical current possible

• may result in stimulation to the pulp- galvanic shock

galvanic shock

• stimulation to the pulp

• ex. metal fork touching a metal restoration, biting aluminum foil

ingestion of hot & cold drinks/food and smoking may alter oral envirnment

• most forms of matter expand when heated and contract when cooled

dimensional change is a change in the size of matter

• acceptable materials used as restorations or replacement of tooth structure should have characteristics similar to tooth structures

• excessive expansion may result in the fracture of cusps & excessive contraction may result in leakage into open gaps, resulting in sensitivity

coefficient of thermal expansion- measures of change in volume or length in relationship to change in…

• amalgam readily heats up and exceeds or cools and contracts w small temp change

• composite is not a good conductor of temp and requires greater temp change to expand or contract

  • both have rates of expansion & contraction that differ significantly enough from enamel and dentin that the marginal…

temperature

• thermal conductivity is the rate at which heat flows through a material over time

how long could u be sensitive after a filling

• 2 weeks

poor thermal conductors

• enamel

• dentin

excellent conductors

• metals

one of the best thermal conductors

• gold

very poor conductors

• nonmetals

• dentin acts as a natural insulator

• ice used w thermal/stimulation test

• base/liner placed if close to the pulp

2 types of retention

• mechanical

• chemical

mechanical retention

• involves the use of undercuts in a prep so material is locked into place

• requires removal of more tooth structure

• ex. silver fillings- u can have saliva

chemical retention

• through adhesion or bonding (glue)

• more conservative as no undercuts are necessary

• stronger retentive force between tooth and restoration

• seal margin to prevent seepage of bacteria and fluids through percolation

• ex. composites (glue to teeth)

wetting

• degree to which a liquid adhesive is able to spread over the surface of a tooth and restorative material

  • increased ability to spread = better retention

• (syrup)

viscosity

• ability of a liquid material to resist flow

  • high viscosity- thicker and don’t flow well

• (honey is more viscos)

film thickness

• is the minimal thickness obtainable by a layer of a liquid material after it sets

mickroleakage

• seepage of harmful materials, leakage of fluid and bacteria caused by microscopic gaps that occur at the interface of the tooth and restoration margins

  • recurrent decay, marginal staining, and tooth sensitivity

  • caused by deterioration of material, percolation due to differences in cte, or lack of adhesion of the material to the tooth

hue

• dominant color of the wavelength detected

• yellow/brown range

chroma

• intensity/strength of the color

• pale in color

value

• how light or dark

• get darker as we age

biofilm

• “dental plaque”

• primary role in dental caries & periodontal diseases

surface roughness

• roughness from abrasion, polishing, hand & ultrasonic scaling, & lack of polishing after placing a restoration

  • direct correlation of biofilm accumulation

  • fluoride releasing materials in restorations neutralize acids

detection of restorative materials

• obvious identification

• difficult identification

• tactile evaluation- feel w finger

• visual evaluation

• radiographic evaluation

summary: materials must be

• biocompatible

• exhibit long term clinical durability

• be esthetically acceptable

factors of oral environments

• moisture

• differing stresses

• temps

• acid levels