materials

Question 1

what does a taper of 0.02 mean?

Answer 1

2% taper, every 1mm towards the shank the diameter increases by 0.02mm

Question 2

what are the advantages of SS files?

Answer 2

dont corrode, rust or stain

Question 3

what are the disadvantages of SS files?

Answer 3

poor flexibility and errors in shaping

Question 4

what types of canals are barbed broaches not suitable for?

Answer 4

curved or narrow

Question 5

what types of SS files are there?

Answer 5

flexofiles, K files and Hedstroem files

Question 6

what are the advantages of flexofiles?

Answer 6

batt tip is non-aggressive, low risk of transport and ledge formation

Question 7

what are hand files mainly useful for?

Answer 7

creating a glide path

Question 8

what are hedstroem files used for and why are they poor for use in preparation of canals?

Answer 8

used in removal of gutta percha due to retreatment or overfilling, not useful for canal prep as they are stiff and can only be used in an up and down motion

Question 9

what are common problems with SS file preps?

Answer 9

ledges, blockages, transportation, debris extrusion

Question 10

what are the favourable characteristics of rotary nickel titanium instruments?

Answer 10

superelastic and memory

Question 11

what is superelasticity?

Answer 11

allows instruments to be used in curved canals with less lateral forces so less lodging, transportation, zipping etc.

Question 12

what is the composition of nickel-titanium instruments?

Answer 12

56% nickel, 44% titanium

Question 13

what are the advantages of nickel titanium instruments over stainless steel ones?

Answer 13

increased flexibility, increased cutting efficiency, better safety and more user friendly

Question 14

name a passive cutting file type and an active cutting file type

Answer 14

passive = profile system GT 
active = ProTaper universal

Question 15

what are the advantages of M wire?

Answer 15

superplastic, improved fatigue resistance, increased safety

Question 16

what are the 3 crystalline phases of M wire?

Answer 16

deformed and micro twinned martensite
premartensitic r phase
austenite

Question 17

what are the advantages of a larger taper?

Answer 17

optimum obturation, effective disinfection of canal

Question 18

what is the purpose of an inter appointment disinfectant?

Answer 18

to reduce and prevent microorganisms that remain following careful cleaning and shaping
to prevent reinfection through coronal or apical leakage

Question 19

requirements of a good inter appointment disinfectant?

Answer 19

long lasting disinfectant action
not irritating to periradicular tissues
non-toxic
not damaging to tooth tissue or restorative materials

Question 20

phenolic compound inter appointment disinfectants

Answer 20

camphorated phenol or CMCP

toxic and possibly carcinogenic

Question 21

what are the uses of calcium hydroxide?

Answer 21

used as an inter-appointment medicament, for pulp capping, for apexification and as a root canal sealer

Question 22

what is the pH of calcium hydroxide?

Answer 22

12.5-12.8 (strong base)

Question 23

what are the characteristics of calcium hydroxide as a medicament?

Answer 23

kills bacteria, inactivates endotoxins, reduces inflammation, eliminates apical exudate, controls inflammatory root resorption, prevents contamination between appointments

Question 24

what is the mechanism for the antibacterial activity of calcium hydroxide?

Answer 24

releases OH- in an aqueous environment to damage the bacterial cytoplasmic membrane, denature proteins and damage bacterial DNA

Question 25

name two commercial calcium hydroxide products

Answer 25

hydrocal, ultracal

Question 26

why is calcium hydroxide useful for weeping canals?

Answer 26

it has a high pH, calcifying potential and the ability to cauterise residual chronically inflamed pulp

Question 27

what are the ideal technical properties of an obturating material?

Answer 27

no shrinkage on setting, no solubility in tissue fluids, good adhesion/adaptation to dentine, no water absorption, no tooth discolouration

Question 28

what are the ideal biological properties of an obturating material?

Answer 28

no allergy for patients or staff, no irritation to local tissues, sterile, antimicrobial, stimulate periradicular healing

Question 29

what are the ideal handling properties of an obturating material?

Answer 29

radiopaque, sets in adequate time, easy to remove and apply using heat, solvents or mechanical instrumentation

Question 30

what is gutta percha a transionomer of?

Answer 30

polyisoprene

Question 31

what are the two crystalline forms of gutta percha?

Answer 31

alpha which is a solid compatible mass and beta which is soft and tacky when heated and shrinks on cooling

Question 32

what are the disadvantages of gutta percha?

Answer 32

lack of adhesion to dentine, shrinks on cooling, cannot be heat sterilised

Question 33

how would you sterilise gutta percha?

Answer 33

sodium hypochlorite solution 1 min

Question 34

what are 3 alternatives to GP?

Answer 34

thermoplastic GP, guttacore and thermafil

Question 35

what is the principal of thermoplastic GP?

Answer 35

continuous wave of obturation

Question 36

why is a sealer required along with GP?

Answer 36

gutta percha, no matter how well adapted to the canal walls, will not create a fluid tight seal

Question 37

what are the ideal properties of a sealer?

Answer 37

provide a fluid tight seal, no shrinkage on setting, slow setting time, fills canal irregularities, bacteriostatic, adheres to dentine, biocompatible

Question 38

what is an advantage of calcium hydroxide as a sealer?

Answer 38

therapeutic activity

Question 39

what are the advantages of bioceramic sealers?

Answer 39

biocompatible, hydrophilic, chemically stable, expand slightly on setting, form a hydroxyapatite, no inflammatory response if overfilled

Question 40

what does smart paste bio contain?

Answer 40

zirconium oxide, calcium silicates, calcium phosphate monobasic, calcium hydroxide

Question 41

name 3 advantages of smart paste bio?

Answer 41

releases calcium hydroxide and hydroxyapatite on setting, hydrophilic, antimicrobial during setting

Question 42

what do calcium silicate sealers consist of?

Answer 42

MTA and water soluble polymer

Question 43

what is advantageous about calcium silicate sealers?

Answer 43

hydrophilic, slow setting, alkaline, stimulate cementogenesis

Question 44

how do calcium silicate sealers stimulate cementogenesis and hard tissue formation?

Answer 44

by osteocalcin gene expression of osteoblast cells

Question 45

what can odontopaste be used for?

Answer 45

an inter-appointment medicament

Question 46

what is odontopaste composed of?

Answer 46

zinc oxide based with corticosteroid and antibiotic

Question 47

what are the contra-indications for odontopaste?

Answer 47

pregnancy, breast-feeding, hypersensitivity to ingredients, purulent pulpitis, deciduous teeth

Question 48

what does iodine kill?

Answer 48

bacteria, fungi, viruses and spores

Question 49

what does povidone iodine do?

Answer 49

induces non-specific cell death due to oxidising free iodine

Question 50

what are the contra-indications of povidone iodine?

Answer 50

pregnancy, breastfeeding and hypersensitivity

Question 51

what facultative anaerobe may be present in pretreatment cases and how is it destroyed?

Answer 51

enterococci faecalis destroyed with IKI or povidone 10 min soak