Dental Trivia- WebDental

1. Patron Saint of dentistry  : St.Appolonia of Alexandria,249 AD

2. First Known dentist : Egyptian , Hesi-Re [3000 B.C]

3. First speciality : Orthodontics [1901]

4. Order of specialities :Ortho [1901]-  Oral surgery [1918]  -Periodontics [1918] -Prosthodontics[1918] -Pedodontics[1927]-Public health [1937] -Oral pathology[1946]  -Endodontics[1963]

5. Earliest Practice of Prosthetic arts –Phoenicians Circa

6. First Dental engine was invented in 1870

7. Pulpitis was recognized by “Archigenus “ in 100 A.D

8. Chirurgia Magna –French Surgeon “GUY de Cahuliac “ in 1386- was the first to coin the term Dentator And Dentists

9. Vesalious In 1500 of Belgium –Accurately Described the teeth of Pulp and pulp chambers

10. Fallopius – Dental Follicle ,Trigeminal nerve,auditory nerve ,Glossopharyngeal ,Hard and Soft palate

11.Credit for the accurate description of Maxillary Sinus : Dr.Nathaniel Highmore of England

12. Ambrose  Pare- a barber surgeon at 16 years of age –a member of College of Surgeons at age 37- Palatal Obturators and transplant techniques

13. Purman of Breslau – Known for Wax impressions

14. Philip Pfaff in 18th century introduced Plaster Of Paris for pouring up models

15. Pierre Fauchard- Father of Scientific dentistry ,Father of Orthodontics

16.Dentistry’s First Pharmacopea –Robert Bunon 1743

17.John Green wood 1789 dentures for George Washington

18. Charles Good year – 1840- Vulcanite rubber

19. E J Dunning -1844- Made plaster of Paris impressions , first shown in America

20.First Women dentist in England – widow of Dr.Povey in 1719

21.First Women dentist In US – Emeline Rupert Jones of Connecticut

22. First Women Graduate – Dr.Lucy Hobbs in 1865-She  graduated From OHIO dental college

23. Introduction Of porcelain into dentistry –Duchantenu

24. John Baker – MD surgeon Dentist –earliest qualified Dentist to practice in Boston and in America -1763 A.D

25. 1769 A.D – Title Of Doctor Began to be used

26. 1788 A.D – Improvement and development of Porcelain dentures by de Chemant

27. First dental book to be published in America – Richard Cotland Skinner

28. First dental chair – James  Snell 1832

29. American Journal of Dental Science – 1839 A.D – First dental periodical

30 .First dental school –Baltimore dental college of Surgery –Founded By Harris and Harden

31.Rubber Dam suggested By Sanford .C.Barnum

32.First Foot /threadle engine – Morrison in 1872

33.Hydraulic Chair – Wilkerson -1877 AD

34.System of Dental nomenclature –G.V Black

35. Roentgen- discovered Xray

36. Edward kells – Demonstrates the use of Roentgen rays in dentistry

37. Weston A Price recommends the use of X-ray in RCT

38. Dr.William H Taggart –cast gold inlays

39.Castan –invented epoxy resins

40. Microwave Amplification By stimulated emission of radiation –MASER – Bell Labs’ Arthur L Schawlow and Charles H Townes

41. Theodore Maimans’s Ruby Laser- First working laser in history-May 16 1960

42. Dr.Ali Javan – First Gas laser with Helium Neon 1960

43. Carbon Dioxide Laser – Kumar Patel in 1964

44. L’Esperance –First to report clinical use of an Argon laser in ophthalmology-1968

45 .First artificial fluoridation plant at Grand Rapids ,USA

46.First water turbine hand piece by Dr.Nelson in 1954

47.First air turbine –Dr.Borden in 1957

PHYSICAL PROPERTIES OF MATERIALS – handout -will be on 10-3 quiz

PHYSICAL PROPERTIES OF MATERIALS
Definite and precise terms are used to describe the physical properties of dental
materials. These terms must be clearly defined in order for one to understand the
interrelationships between physical properties, structures, and composition. The
following definitions apply to metals or alloys used in the dental lab

a. Hardness. Hardness is the measure of the resistance of a metal to
indentation or scratching. It is an indication of the strength and wear ability of an alloy
or metal.

b. Ductility. Ductility is the measure of the capacity of a metal to be stretched
or drawn by a pulling or tensile force without fracturing. This property permits a metal to
be drawn into a thin wire.

c. Malleability. Malleability is the measure of the capacity of a metal to be
extended in all directions by a compressive force, such as rolling or hammering. This
property permits a metal to be shaped into a thin sheet or plate.

d. Flexibility and Elasticity. These terms differ in their technical definition, but
they are very closely related.

–Flexibility is the characteristic of a metal that allows it to deform temporarily.

The elasticity of a metal is used when it returns to its original shape when the load or force is removed.

e. Fatigue. Fatigue is the property of a metal to tire and to fracture after
repeated stressing at loads below its proportional limit.

f. Structure (Crystalline or Grain Structure). Metals are crystalline and many
of their physical properties depend largely upon the size and arrangement of their
minute crystals called grains.
(1) Grain size. The size of the grains in a solidified metal depends upon the
number of nuclei of crystallization present and the rate of crystal growth. In the practical
sense, the faster a molten is cooled to solidification, the greater will be the number of
nuclei and the smaller will be the grain size.

Generally speaking, small grains arranged in an orderly fashion give the most desirable properties.

(2) Grain shape. The shape of the grains is also formed at the time of crystallization.

If the metal is poured or forced into a mold before cooling, the grains will be in a flattened state.

Metal formed by this method is known as cast metal.

If the metal is shaped by rolling, bending, or twisting, the grains are elongated and the metal
becomes a wrought wire.

g. Crushing Strength. Crushing strength is the amount of resistance of a
material to fracture under compression.

h. Thermal Conductivity. Thermal conductivity is defined as the ability of a
material to transmit heat or cold.

A low thermal conductivity is desired in restorative materials used on the tooth

whereas a high thermal conductivity is desirable where the material covers soft tissue.

Notes for Gypsum (will be on quiz)

Gypsum- notes to study for quiz

Gypsum = Calcium sulfate dihydrate (Calcium Sulfate plus 2 parts water)

CaSO4 2H2O

Gypsum is mined.
The process to produce Plaster of Paris and artificial stone (dental stone or die stone) from raw gypsum is called Calcination (also referred to as calcining)

Calcining in an open vat with heat = Plaster of Paris or Lab plaster

Calcining by steam heat under pressure in an autoclave = Artificial stone, Dental stones, Die stone or Hydrocal

Calcining removes ¾ (75%) of the water from the ground gypsum.

Plaster and Dental stones are chemically identical. But the powder particles have different shapes.

Plaster = Rough, irregular & porous

Dental Stones = Prismatic, more regular in shape, dense and nonporous
Water and gypsum powder are commonly mixed in a rubber bowl with a stiff metal or plastic spatula.

Water measured first, put into bowl

Plaster is measured and added to the water.

 

When water is mixed with calcium sulfate hemihydrate, heat is produced as the product converts back into a hard stone-like form.

The heat release is known as an exothermic reaction.

Exothermic reactions give off heat, heat Exits the mass

Endothermic reactions require heat for the reaction to take place.

The amount of heat released in an exothermic reaction is equal to the amount of heat required to form the hemihydrate form of gypsum.

 

The amount of water used when mixing a gypsum material affects the hardness and strength of the gypsum. It also affects the setting time.

 

When you hold a model made from gypsum under running water the surface begins to erode.

Fine details and dimension are lost from a stone cast exposed to running water.

 

Setting times =             working time

INITIAL setting time = 8-15 MINUTES

FINAL setting time = 45 Minutes – 1 hour

 

Accelerators= shorten the setting time

Retarders = lengthen the setting time

Instead of using chemical accelerators and retarders, it is safer to control the setting time by manipulating or changing the water temperature, mixing rate/speed, mixing time, and the water to powder ratio (amount of water)

 

Wet strength vs dry strength

Wet strength is the strength of the material with excess water still present.

Dry strength is the strength of a dried gypsum 24 hours after setting

The compression/crushing strength of gypsum left to dry 24 hours doubles compared to wet strength.

Greatest strength is achieved after 24 hours.

If you were to use reduced water to powder ration in a gypsum mixture, and mix it very hard and fast at a temperature of 45°C, (113°F) the setting time would be shortened.


Increase Setting Time (set slower) of gypsum

  • Use cooler water
  • Use a chemical retarder
  • Use more water than recommended (thin mix)

Decrease setting time (set quicker) of gypsum

  • Use warmer water up to 85 ºF
  • Use a chemical accelerant
  • Spatulate (mix) longer and faster up to one minute
  • Use less water than recommended (thick mix)
  • Use slurry water

ADA Classification of Gypsum products

Type I = Impression Plaster- rarely used today

Type II = Lab Plaster or Model Plaster (white) weakest, least expensive

Type III = Dental Stone or Buff Stone (yellow)

Type IV = Die Stone (blue, green or pink)

Type V = High Strength stone (Ivory stone used in Ceramics) Strongest, most expensive, newest

Infection control- see:

https://eccdentaltech.files.wordpress.com/2014/09/infection-control-in-the-dental-lab-what-you-should-know.pdf

Levels of decontamination

Low = Sanitize

Medium = Disinfect

High = sterilize