Endodontic Materials Flashcards
By what units do endodontic hand instruments increase by as size increases?
by 5 UNITS from size 10 to 60.
by 10 UNITS from 60 to 150.
What does the endodontic hand file size mean?
represents the DIAMETER OF THE FILE AT THE TIP. (ex. 10 is 10/100 and thus 0.1mm at the tip).
How long is a hand file working blade? Where does it start and where does it end? How much thicker is the top of the working blade compared to the bottom?
- Starts at tip (D0), ends at D16.
- 16mm long.
- D16 is 32/100 or 0.32mm greater than D0.
What is the tip angle of an endodontic hand file?
tip angle is 75 degrees +/- 15 degrees
What is the taper of stainless steel hand files? What does this mean? What length are these files available in?
- 2% (0.02) taper - every 1mm towards the shank the diameter of the file increases by 0.02mm.
- length is available in 21, 25, 31mm (working part remains 16mm).
What are stainless steel hand files composed of?
iron alloys with at least 10.5% chromium
(other metals: nickel, molybedenum, titanium, copper).
what are the advantages and disadvantages of stainless steel hand files?
- Advantages: do not easily corrode, rust or stain.
- Disadvantages: poor flexibility, leads to many procedural errors during canal shaping.
What is the difference between how small and larger hand files are manufactured?
- small are made from SQUARE BLOCKS (thus more resistant to torque)
- large are made from TRIANGULAR BLOCKS (thus better cutting efficiency).
What are the 3 types of stainless steel files?
- barbed broaches
- roamers
- files (K files, Flexofile, Hedstrom).
When are barbed broaches used? When are they NOT to be used?
- used for emergency pulp extirpation (removal of pulpal tissue when present).
- can be used in anterior teeth, CANNOT be used in NARROW, CURVED CANALS.
When are roamers used?
Were used historically.
What are hand instruments particularly useful for?
In the EARLY phases of instrumentation to establish a GLIDE PATH prior to using rotary instruments.
- in anatomically challenging cases and in treating instrumentation complications (may be the only option).
What are flexofiles used for?
- estabilishing glide path, apical gauging, negotiating ledges and blockages.
what is the tip of flexofile called?
BATT TIP (non-agressive tip).
What are 3 advantages of flexofiles?
- Non-aggressive tip (BATT TIP).
- good flexibility
- efficient at cutting dentine with a low risk of transportation and ledge formation.
What is the ideal instrumentation technique to use flexofiles with?
balanced force
What are some properties of Hedstrom files (3) and when are they used?
- very stiff.
- can only be used in up and down motion.
- file cuts when moved in coronal direction.
- used in RETREATMENT to remove gutta-percha or an overfilling of the canal.
What are 4 main disadvantages of hand files?
- Mishaps (ledging, transportation, zipping of foramen, blockages).
- Debris extrusion.
- Time consuming.
- Less predictable shapes in curved canals.
when were rotary nickel titanium files introduced?
1990s.
What do Ni Ti rotary files require?
Endodontic, torque control motor - NEVER use in slow speed.
What are two MAIN properties of niti files?
- superelasticity
- shape memory
What is the advantage of Superelasticity in NiTi files?
- allows NiTi files to be placed in CURVED CANALS with LESS LATERAL FORCES
–> less zipping, transportation, ledging.
–> more centrally placed restoration.
What does superelasticity mean?
- can be strained more than other alloys without permanent deformation.
What are NiTi files made of?
56% nickel, 44% titanium
What is NiTi shape memory due to?
- at root temp in AUSTENITE form.
- when stress is applied it changes to MARTENSITE (and changes shape)
What are two differences in the properties of SS and NiTi files?
- NiTi can be elastically deformed up to 3 times more than stainless steel flies before permanent deformation.
- NiTi have a lower modulus of elasticity –> forces exerted on root canals by deformed NiTi files is much less than ss files resulting in less iatrogenic errors during instrumentaion.
What is the unstressed form of Niti? The stressed form?
- Unstressed: Austenite
- Stressed: Martensite
Why can NiTi shape memory be disadvantageous?
- problematic in CURVED canals as they always want to straighten –> over-instrumentation, canal straightening, unfavourable stressed (cyclical fatigue failure).
What is the first generation of NiTi files? When was it released? Taper type?
1990s - Profile, system GT.
CONSTANT taper.
What is the second generation of NiTi files? When was it released? Taper type?
2006 - Protaper, Protaper Universal. VARIABLE taper.
How is superelastic NiTi wire (M wire) formed? How is this different (in terms of structure) to normal NiTi?
Through a thermomechanical processing procedure. Has more stable martensite under clinical conditions.
What are four advantageous properties of M wire compared to normal NiTi?
- Higher tensile strength.
- improved FATIGUE RESISTANCE.
- greater flexibility
- increased safety (protection against instrument fracture).
What are the 3 crystalline phases of M wire?
- deformed and microtwinned martensite.
- Premartensitic R phase.
- Austenite.
By how much (in %) does M wire improve resistance to cyclic fatigue? Why is this advantageous?
- 400%
- reduces potential for separated instruments in curved canals.
What is the fifth generation of NiTi files? When was it released? What is its rotary motion?
- Released in 2013 - Protaper NEXT.
-offset from central axis of rotation –> asymmetrical rotary motion that travels along the length of the file “SWAGGERING EFFECT”
What is the SWAGGERING EFFECT
In Protaper Next files, the cros-section is offset from the central axis of rotation, causing asymmetrical rotary motion that travels the length of the file.
What is the taper, use and mode of use (how to use it) of Proglider?
- 2% taper.
- used to EXAGERRATE THE GLIDE PATH.
- In and Out motion.
What are controlled memory files? Give 4 examples.
- Thermomechanically processed, have martensitic properties at room temperature –> very flexible files with NO MEMORY (no SPRING BACK).
- Thus can adapt to root canal curvatures without creatung undesirable lateral forces.
- typhoon, edgetaper platinum, hyflex cm, PROTAPER GOLD
What are 4 advantages of NiTi vs SS.
- increased flexibility in larger sizes.
- increased cutting efficiency.
- better safety in use.
- better user friendliness.
What are 4 disadvantages of NiTi files?
- Instrument fracture (TORTIONAL STRESS or CYCLICAL FATIGUE).
- expense
- access can be difficult in posterior teeth.
- unsuitable for complex canal anatomy (ex. dens invaginatus).
What are 3 advantages of larger tapers? To what taper should canals be prepared?
- MINIMUM OF 6% to achieve optimum obturation.
- Greater taper allows more effective disinfection.
What are interappointment medicaments and what are their aims (2)?
- ANTIMICORBIAL agents placed in the root canal system between appointments.
- Aims:
- reduce and prevent multiplication of microorganisms.
- prevent reinfection from apical and coronal leakage.
What is a type of HISTORICAL inter-appointment medicament? Why?
- Phenolic compounds: camphorated phenol, formocresol, cresophene.
- Highly toxic to vital tissues, carcinogenic?, not effective.
why are phenol medicaments not effective?
- work by release of vapors and are therefore fairly short-acting.
What are 5 uses of calcium hydroxide? Setting or non setting?
- pulp capping (setting)
- root canal sealer
- apexification (non setting)
- treatment of root perforations, root fractures, root resorption and dental trauma.
- inter-appointment intracanal medicament (non setting).
What is the pH of calcium hydroxide? What does it dissociate to and what does that cause?
- Strong base (12.5-12.8).
- Dissociates to calcium and OH ions –> induce hard tissue deposition + are antibacterial.
What are 5 functions of CaOH when used as a medicament?
- kills bacteria and inactivates endotoxin (LPS).
- reduces inflammation.
- helps eliminate apical exudate.
- controls inflammatory root resorption.
- prevents contamination between appointments.
How does CaOH affect bacteria?
Hydroxyl ions:
- damage bacterial cytoplasmic membrane.
- protein denaturation.
- damage to DNA.
What is requirement for maximum CaOH antibacterial effect?
- DIRECT CONTACT with bacterial cells.
For what microorganism is the efficacy of CaOH doubted?
enterococcus faecalis.
Is CaOH as an inter appointment medicament setting or non-setting? Gives two product names.
- NON setting paste.
- Ultracal, Hypocal.
What are the steps to placing CaOH as an inter-appointment medicament?
- dry the canal with paper points to working length.
- use spiral fillers or disposable tips 2mm from WL.
- completely fill canal without extruding excess.
What is a weeping canal?
discharge in the canal at each opening.
How do you treat a canal with exudate?
- dress the canal with CaOH
(calcifying potential, high pH, may cauterise residual chronically inflamed pulpp).
What is apexification?
- creating an environment AFTER PULP DEATH that allows a CALCIFIED BARRIER to form across an OPEX APEX of an IMMATURE TOOTH.
- calcified barrier: osteocementum, bone-like tissue.
What products are used for apexification?
Mineral trioxide aggregate, calcium hydroxide.
What are two indications for apexification?
- Vital radicular pulp in an IMMATURE tooth pulpotomy (may have some root formation from surviving Hertwig’s epithelial root sheath).
- Pulpless immature tooth with other without periapical radiolucency. (use MTA)
What would you use to perform an apexification in an pulpless immature tooth with or without periapical radiolucency?
Mineral Trioxide Aggregate
