DENTAL MATERIALS #2

TERMINOLOGIES:

FLOW – a property of the material to be deformed continuously without altering the magnitude of the applied force

* Impression materials should have good flow property in order to get the detailed parts

RHEOLOGY – study of the flow of matter MICROLEAKAGE – the presence of microscopic spaces between

the restoration and the prepared cavity which may lead to bacterial growth around the restoration and it is usually associated with post-operative sensitivity

THERMAL CHANGES – the tooth structure and the restoration are continuously exposed to hot and cold beverages and food, therefore, thermal conductivity and the coefficient of thermal expansion of the restorative material are important properties to preserve the health of the pulp

GALVANISM/GALVANIC ACTION – the presence of different metals in the oral cavity producing elective shock or electric current

*170lbs – average biting force

INFECTION CONTROL – the routine use of mask and gloves to protect the dentist against infection from microorganism

WEAR, ABRASSION & EROSION – loss of material from a surface caused by mechanical action or through combination of chemical and mechanical action

o ABRASSION - mechanicalo EROSION – chemicalo WEAR – both chemical and mechanical

ALLERGY – abnormal antigen-antibody reaction to a substance that is harmless to most individuals

BIOCOMPATIBILITY – the ability of a material to elicit and appropriate biological response in a given application in the body

TOXICITY – a dose related potential material to cause cell or tissue death

VISCOSITY – the resistance of a fluid to flow TARNISH – surface discoloration on a metal or a slight loss or

alteration of the surface finish or luster CORROSION – deterioration of a metal which is caused by

reaction with its environment

TOXICITY EVALUATION OF DENTAL MATERIALS; Should be harmless to the pulp and the soft tissues No toxic substance that can be absorbed into the circulatory

system to cause toxic response Free of sensitivity agents to cause an allergic response No carcinogenic potential

GYPSUM – rock or solid substances which have been grounded into powder form and then heated

CALCINATION – manufacturing process if gypsum followed by heating process

OPEN CALCINATION – gypsum is heated on a kettle 110 - 120°C resulting in β-hemihydrate or PLASTER OF PARIS

CLOSED CALCINATION – gypsum is heated 120 - 130°C resulting in α-hemihydrate or DENTAL STONE

ADA CLASSIFICATION OF GYPSUM PRODUCTS

TYPE I – SOLUBLE/IMPRESSION PLASTERo Used as an impression material, usually secondary

material TYPE II – MODEL PLASTER/PLASTER OF PARIS

o Investing medium used to stabilize the articulation of the upper and lower cast in the articulator

o For study cast TYPE III – DENTAL STONE

o For construction of a working cast TYPE IV – DENTAL STONE HIGH STRENGTH/ DIE CAST

o For construction of working die TYPE V – DENTAL STONE HIGH STRENGTH, HIGH EXPANSION

o For cast constructiono used in casting gold (18k)

PLASTER OF PARIS bigger in size compared to dental stone has irregularly shaped crystal less dense, randomly shaped used to make study cast/model used as an investing medium to create the mold of the future

restoration used to make surgical cast used to make figurines

DENTAL STONE smaller, prismatic and regularly shaped compact/denser stronger than plaster

DENTAL STONE HIGH STRENGTH stronger than ordinary dental stone used to make working die

DENTAL STONE HIGH STRENGTH, HIGH EXPANSION used as investing medium if using white metals

IMPRESSION – negative copy of an arch

CAST – positive copy of an arch

DIE – copy of a single tooth or more

*pure gold (24k) cannot be used in the oral cavity*white metals have high shrinkage

Rosette Go 111508