Endodontics Flashcards
describe the bacterial mix in a compromised root canal
aerobic and anaerobic bacteria,
changes to more anaerobic with time,
change to more gram negative,
symbiotic relationship of: streptococci, prevotella oralis, porphyromonas
what should be assessed radiographically in the pulp chamber ?
position of roof and floor,
amount of reparative dentine
what should deb assessed radiographically in the root canals ?
number of roots and canals,
degree of generalised calcification,
pulp stones,
curvature
what exists at a cellular level in the apical war zone ?
polymorphonuclear leucocytes,
macrophages,
B and T lymphocytes,
plasma cells
what inflammatory mediators are present in an apical abscess ?
neuropoetides,
complement systems,
lysozymes
what produces the periapical lesion ?
prostoglandins, leukotrienes, cytokines
what are the tree types of files used in endodontics ?
K files, Hedstrom files, ProTaper files
what are the requirements for the pre - operative radiograph ?
tooth centrally located,
3-4 mm peri-radicular tissue visible,
second film with 15 to 20 degree horizontal parallax
what is the purpose of the access cavity ?
remove the entire roof of the coronal pulp chamber,
allows ready access to all root canals with straight line access
what determines the shape of the access cavity ?
position and number of pulp horns
which burs should be used to prepare the access cavity ?
high speed for initial penetration: small round 520 tapered fissure 554 slow speed for refinement: tapered fissure round burs
what are the stages of creating the access cavity ?
breach pulp chamber with 554,
apply rubber dam,
remove roof of pulp chamber with slow speed long shank round bur - cut on upstroke,
flare walls of pulp chamber and access cavity so greatest diameter is at tooth surface,
clear debris with excavator,
irrigate with ultrasonic,
locate canals and check straight line access
what are the advantages of rubber dam in endodontics >
protects oro-pharynx, protects soft tissues from caustic materials, retracts soft tissues and tongue, improves access, prevents salivary contamination
what are the 3 methods of measuring working length?
tables of average length,
apex locator,
radiography
how do apex locators work ?
measure electrical resistance with direct, alternating and high frequency currents,
measure voltage gradients,
calculate ratio between impedance
what is the impedance measures by apex locators between apical tissues and the lip ?
6.5 kOhms
what are the problems with the use of apex locators ?
wet canals (absolute AL machines only) - e.g. hypochlorite, puss, tissue exudate
heavily restored crown - eg amalgam, gold inlay
poor contact of lip electrode
what is the working length ?
distance from a fixed reference point on the crown of the tooth to the terminus near the radiographic apex
what is the modified step back technique ?
the coronal aspect is opened up first before creating terminal stop and flaring backwards to the original flare
when in the modified step back technique used ?
large canals,
most often anterior teeth or single rooted premolar teeth
what shape should the prepared canal be ?
continuously tapering cone
what files are used for orifice enlargement ?
hedstrom
describe the hedstrom files
machined from a round tapered blank,
creates a sharp cutting blade,
file has aggressive cutting action
what are the alternative instruments for orifice enlargement ?
Gates Glidden burs
what is the equation for calculating the diameter of GG burs ?
20(GG+1)+10 in hundredths of a mm
describe the tip of modern end files
Batt tip,
blunted,
enables file to follow canal wall
what is meant by ISO?
international standards applied to endodontic files
what are the iso standards ?
standardised sizing related to diameter 1mm from tip of instrument,
colour coded handles,
standardised length of working part of instrument,
standardised taper 2%
what 3 lengths are files made to ?
21mm,
25mm,
31mm
what length is the cutting area of endodontic files ?
always 16mm
how are endodontic files allocated sizes ?
one hundredths of a mm at the projected tip e.g. size 25 file is 0.25mm at the tip
how is instrument taper calculated ?
16X0.02 = 0.32 (width of files at the upper end of cutting area)
eg a iso 25 file is 0.25 mm at tip and 0.32 mm wider at top
what is the purpose of orifice enlargement ?
remove heavily infected material,
improves access to apical third,
improves irrigation,
reduces effective curvature
how many instrument changes are required to create the apical stop ?
9
how many file changes are required to create the step back ?
14
how many degrees should the file be turned when watch winding ?
90
describe the balanced force technique
power phase - place file until it binds, turn clockwise by 90 degrees control phase - turn file 120 degrees anticlockwise whilst applying apical pressure
what are the advantages of the balanced force technique ?
superior shaping,
file remains central within canal,
less debris pushed apically
what sized file should deb used to create an apical stop ?
2 sizes above the first file that binds in the canal
what errors can occur during canal preparation ?
incomplete debridement,
lateral perforation,
apical perforation,
blockage of canals,
ledging,
apical zipping - inappropriate rotation of instruments,
elbow formation - inappropriate pre curving of instruments
when and why is longitudinal circumferential filing used ?
large irregular shaped canals at the step back stage,
when balanced force is inappropriate as files would be loose in canal
what are the ideal properties of an irrigant ?
non irritant, bacteriocidal, dissolve organic material, remove inorganic material, non staining to dentine, lubrication of instruments
what irritants are used in RCT ?
sterile saline,
local anaesthetic solution,
sodium hypochlorite,
chlorhexidine
what is the concentration of sodium hypochlorite used in RCT ?
0.5-5.0%
what is the gauge of the irrigation needles?
27
what is unique about irrigation needles ?
side delivery to avoid danger of solution extrusion through the apex
what is the chelating agent used in RCT ?
Ethylene Diamine Tetra Acetic acid 15-17 %
what is the purpose of the chelating agent ?
breaks down inorganic debris,
lubricant,
removes smear layer with NaOCl
what lubricating pastes are used in RCT ?
canal +,
fileze,
glyde
what is the contents of lubricating pastes ?
15% EDTA,
10% urea peroxide,
water soluble base
what is gutta percher ?
transiosomer of rubber
when is the crown down technique used ?
in small canals
what are the advantages of the crown down technique ?
excellent shaping with minimal number of instrument changes,
flexible nickel titanium files follow gentle curves in canal morphology
what is the cutting length of ProTaper files ?
14mm
what lengths are available in ProTaper files ?
21mm,
25mm,
31mm
what is the maximum flute diameter of ProTaper files ?
1.2 mm
what are the advantages of ProTaper files ?
patented progressive taper design improves flexibility and cutting efficiency,
fewer files needed to achieve fully tapered canal,
files engage a smaller area of dentine, reducing torsional loads, file fatigue and risk of separation,
convex triangular cross section reduces contact area between file and dentine,
greater cutting efficiency through balancing the pitch and helical angles
what are ProTaper files made of ?
nickel titanium
what are the properties of nickel titanium ?
super elasticity and shape memory,
3-5 times elasticity of steel,
decreased ledging and transportation
describe the structure of nickel titanium
two crystallographic forms -
austenite (parent shape)
martensite (daughter shape)
change from parent to daughter is stress induced
What is the purpose of obturation ?
Prevent microorganisms entering and re infecting the canal, prevent tissue fluids percolating back into the canal and providing a culture medium for residual bacteria
What is the aim of obturation ?
Create apical and coronal seal
What are the ideal requirements prior to filling a canal ?
Dry, absence of pain, no infection, reduction in mobility
What is the significance of the smear layer when filling root canals ?
1-2 microns thick but extends into tubules 40 microns, avenue for leakage of microorganisms, substrate for microbial proliferation
How is the smear layer removed ?
17% edta with sodium hypochlorite
10-55% citric acid rinsed with sodium hypochlorite
What is edta a constituent of ?
Glyde
What material is used to obturation the canal ?
Gupta percher
What is in a gutta percher point ?
Gutta percher, zinc oxide, waxes, colouring agents, metal salts
What is the function of a root canal sealer ?
Cements the core material into the canal, fills voids, lubricant, bacteriocidal agent, thermal insulator
What are the characteristics of an ideal sealer ?
Non irritating, hermetic sealing ability, insoluble in tissue fluids, dimensionally stable, radiolaque, bacteriostatic, non staining to dentine
What are the different types of sealers ?
Zinc oxide eugenol, calcium hydroxide, resin, glass ionomers
Describe the zinc oxide and eugenol sealer
Weak and porous when set, decompose in tissue fluid, cytotoxic, most popular
Describe the calcium hydroxide sealers
Designed to stimulate healing and hard tissue formation at foramen, caoh2 may leach out and weaken cement
Describe the resin sealers
Good sealing and adhesive properties, initial inflammatory reaction, antibacterial properties, less popular
Describe glass ionomers sealers
Adheres to dentine walls, initial inflammatory reaction, sealing ability debated
What is the most common sealer ?
Tubli seal
How is gutta percher condensed in the canal ?
Cold lateral condensation
What is the sequence for placing gutta percher ?
Sealer around canal walls, place master gutta percher point, place accessory points
What is used to place the sealer in the canal ?
Master apical k file
What should be done once the canal is fully obturated ?
Radiograph, remove coronal gp with hot excavator
What are the common errors of obturation ?
Inaccurate placement of gp point, incorrect spreaders, extrusion of filler or sealer through apex, excessive condensation pressure, inadequate coronal seal
What is the purpose of obturation ?
Prevent microorganisms entering and re infecting the canal, prevent tissue fluids percolating back into the canal and providing a culture medium for residual bacteria
What is the aim of obturation ?
Create apical and coronal seal
What are the ideal requirements prior to filling a canal ?
Dry, absence of pain, no infection, reduction in mobility
What is the significance of the smear layer when filling root canals ?
1-2 microns thick but extends into tubules 40 microns, avenue for leakage of microorganisms, substrate for microbial proliferation
How is the smear layer removed ?
17% edta with sodium hypochlorite
10-55% citric acid rinsed with sodium hypochlorite
What is edta a constituent of ?
Glyde
What material is used to obturation the canal ?
Gupta percher
What is in a gutta percher point ?
Gutta percher, zinc oxide, waxes, colouring agents, metal salts
What is the function of a root canal sealer ?
Cements the core material into the canal, fills voids, lubricant, bacteriocidal agent, thermal insulator
What are the characteristics of an ideal sealer ?
Non irritating, hermetic sealing ability, insoluble in tissue fluids, dimensionally stable, radiolaque, bacteriostatic, non staining to dentine
What are the different types of sealers ?
Zinc oxide eugenol, calcium hydroxide, resin, glass ionomers
Describe the zinc oxide and eugenol sealer
Weak and porous when set, decompose in tissue fluid, cytotoxic, most popular
Describe the calcium hydroxide sealers
Designed to stimulate healing and hard tissue formation at foramen, caoh2 may leach out and weaken cement
Describe the resin sealers
Good sealing and adhesive properties, initial inflammatory reaction, antibacterial properties, less popular
Describe glass ionomers sealers
Adheres to dentine walls, initial inflammatory reaction, sealing ability debated
What is the most common sealer ?
Tubli seal
How is gutta percher condensed in the canal ?
Cold lateral condensation
What is the sequence for placing gutta percher ?
Sealer around canal walls, place master gutta percher point, place accessory points
What is used to place the sealer in the canal ?
Master apical k file
What should be done once the canal is fully obturated ?
Radiograph, remove coronal gp with hot excavator
What are the common errors of obturation ?
Inaccurate placement of gp point, incorrect spreaders, extrusion of filler or sealer through apex, excessive condensation pressure, inadequate coronal seal
What does ledermix contain ?
Demethychlortetracycline, triamcinalone acetonide
What does odontopaste contain ?
Clindamycin, triamcinalone acetonide
What should the use of ledermix be restricted to ?
Acutely inflamed vital pulp where analgesia for extirpation cannot be obtained, insuffienct time to do rct following pulpal exposure
What is the medicament of choice ?
Calcium hydroxide
What are the properties of calcium hydroxide ?
12.5 ph, bacteriocidal, solvent of organic debris, connective tissue repair, hard tissue Genesis, neutralises acids (oh ion)
Activates calcium dependent atp reaction for hard tissue formation (ca ion)
What are the uses of calcium hydroxide ?
Pulp cap, inter visit medicament, treatment of large peri apical lesions, apexification, root resorption, root fractures
What is r4 root canal solution ?
20% chlorhexidiene solution
How are canals temporarily sealed ?
Cotton wool dressing, gic or zinc oxide eugenol
